, 唐艳鸿北京大学城市与环境学院 地表过程分析与模拟教育部重点实验室,北京 100871
Development and achievements of biogeography and ecology at Peking University
LIUHongyan, TANGYanhong收稿日期:2017-10-16
修回日期:2017-11-2
网络出版日期:2017-11-20
版权声明:2017《地理学报》编辑部本文是开放获取期刊文献，在以下情况下可以自由使用：学术研究、学术交流、科研教学等，但不允许用于商业目的.
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1 发展脉络
1953年,北京大学地质地理系建立了植物地理学教研小组,1991年在这个小组的基础上成立了景观生态学教研室,在国内最早开展宏观生态学研究。陈昌笃、王恩涌、吴荔明、田连恕、黄润华、崔海亭等学术前辈先后在植物地理教学小组和景观生态学教研室工作,为学科发展做出了贡献。此后,研究队伍不断扩大,2002年6月在上述教研室的基础上成立了生态学系,方精云担任首任系主任。生态学系目前有在职教员15人,唐艳鸿担任系主任。经过65年的发展,特别是近15年来的发展,北大生物地理学与生态学已经成为国内综合性研究型大学中首批从事各类生态学专门人才培养和生态学基础与应用研究的机构之一。城市与环境学院招收生态学专业和自然地理专业的博士生、生态学专业的硕士生,2003年开始招收生态学专业本科生。相应地,研究领域也逐步扩展,从生理生态学、群落生态学、景观生态学研究到生物多样性、全球变化以及随后开展的碳循环、生态遥感和全球生态模型研究,代表了从格局到过程,从区域到全球的发展方向。2011年,“中国陆地植被时空格局与生态功能”创新研究群体成功获得国家自然科学基金委支持,并延续至今。
2 主要成就
北京大学的植物地理与生态学研究始终围绕植被的结构、功能和动态开展研究,在此基础上面向全球变化应对、生物多样性保护、可持续发展等国家需求开展了理论与应用结合的研究,主要学术成就可以概括为6个方面：2.1 气候变化及陆地生态系统响应
国际社会对全球变化尤其是对气候变暖及其机制的争论激烈。方精云团队针对这一热点问题开展了较为系统地分析,其部分研究结果以评述论文的形式分别用中英文发表在“中国科学”上（参见“中国科学：地球科学”2011年41卷10期：“全球变暖、碳排放及不确定性”）。该研究在系统梳理气候变化研究进展的基础上,对全球化石燃料碳排放与大气CO2浓度之间、大气CO2浓度与温度变化之间的关系进行了分析,认为全球变暖是客观事实,但全球升温幅度存在不确定性;对于全球变暖的机制,归因于人类活动和自然因素的共同影响,但其相对贡献量难以量化。该研究发表后在国际上引起了强烈反响,被多家研究机构和媒体转载或评述。方精云和朴世龙等较早地开展了气候变化的生态响应研究。方精云团队应用基于遥感观测的CASA模型[1-4],整合近20年的卫星遥感植被、气候、土壤和太阳辐射等地面观测数据,研究了中国陆地植被的净初级生产力（NPP）的时空变化及其与环境因子的关系,并发展了区域植被动态变化的评价方法。其核心结论是,20世纪80年代初以来,中国植被NPP在波动中呈增加趋势,生长季节的提前是其增加的主要因素;受土地利用和气候变化的影响,NPP的变化存在巨大的空间异质性;在国家尺度,植被活动滞后于温度变化[1-2, 5]。朴世龙团队的研究进一步发现,大气CO2浓度升高等导致1982年以来全球大部分地区陆地植被生长总体呈增加趋势[6]。该文章被评为2016年气候变化领域最受媒体关注的10篇文章之一。
另一方面,各种全球变化过程引起的陆地生态系统响应又会通过生物地球物理过程和生物地球化学过程,来反馈调节气候系统,但相关研究非常匮乏。朴世龙团队与欧美科学家合作,首次利用遥感获取的全球植被叶面积数据驱动地球系统模型,并结合理论模型,探讨了植被变化对地表能量平衡的影响。研究发现,过去30年的陆地植被生长活动增强,通过生物地球物理过程减缓了全球气候变暖,其降温效应相当于全球变暖速率观测值的12%。这主要由植被变化所引起的地表蒸腾增强、大气透明度减弱、大气环流变化所致。该成果不仅有助于了解陆地生态系统变化对气候系统的反馈作用,也为应对气候变暖的宏观决策提供了科学依据[7]。
近年来物候对气候变化的响应研究颇受生态学家关注,已成为全球变化研究领域的一个新热点。朴世龙团队与欧洲科学家合作,利用欧洲物候观测网1245个站点树木春季展叶物候数据,系统地分析了过去30年全球变暖对欧洲温带地区树木展叶物候的影响及其机制。研究发现,较之于20世纪80-90年代,2000年以后树木春季展叶物候对春季温度的敏感性下降了约40%,这意味着植物物候表现出了对气候变暖的适应性。通过理论模型,研究小组进一步证实了这一现象与过去30年植物休眠期温度上升有关。这一成果不仅改变了目前全球变暖将会持续导致植物春季物候提前的普遍观点,而且有助于深入了解植物对气候变化的响应过程及其机制,为利用物候数据准确重建历史气候提供了重要的理论基础[8]。
朴世龙课题组还在农业植被响应气候变化方面有突破性进展。他应邀在Nature杂志上发表了综述论文,系统地分析了气候变化对中国农业和水资源的挑战[9]。近期,朴世龙课题组通过比较全球范围内大田水稻增温实验和3种模型（经验统计模型和基于站点及全球格点尺度的作物过程模型）的模拟结果,发现经验统计模型和全球作物模型可能低估了增温对全球水稻的减产效应。同时,针对不同全球作物模型模拟结果之间存在较大的不确定性,他们首次结合条件概率的方法,估算未来气候变暖对水稻产量的潜在影响。研究结果表明,未来长期温度升高导致全球水稻的潜在减产效应约为8% K-1[10-11]。
方精云课题组一直关注湖泊水体对气候变化的响应。早期比较系统地研究了长江中游湖泊的分布、变化及其对生物多样性的可能影响,尤其对洞庭湖和江汉平原的湖泊变迁进行了较为细致的研究[12]。近年来开展了内蒙古高原湖泊水位变化的研究,通过遥感影像分析发现开矿和农业活动是内蒙古湖泊面积减小和湖泊干涸的主要原因[13]。刘鸿雁课题组进一步研究了气候变化影响下中国半干旱区湿地的变化,发现了伴随着湖泊水位的下降,盐化草甸取代了沼泽和低地草甸[14]。
青藏高原生态系统的敏感性是全球关注的热点之一。贺金生研究组在青海海北建立了国际上先进的全球变化研究实验平台,包括“增温—降水”控制实验、草地N、P、K养分添加实验、湿地温室气体排放监测平台。课题组通过连续5年的群落调查和生产力测定,研究了高寒草地植物群落生产力对增温和降水改变的响应,探讨了高寒草甸群落稳定性的控制因子,揭示了气候变暖对高寒生态系统生产力稳定性的影响机制[15]。课题组进一步结合海北高寒草地生态系统国家野外科学观测研究站32年的生物量监测、控制实验和基于青藏高原相关实验的Meta分析,发现尽管在过去32年间生物量没有显著变化趋势,但群落物种组成却发生了显著变化,禾草类生物量显著增加,而莎草类显著降低。由于禾草类根系较莎草类根系分布更深,气候变化引起的禾草类增加使得整个生态系统能够在干旱条件下接收到更深层次的土壤水分[16]。这在机理上解释了为什么尽管高寒草甸经历了急剧的气候变化,但生物量却相对稳定。
2.2 陆地生态系统碳循环
早在21世纪初,方精云课题组构建了中国第一个国家尺度的陆地碳循环模式;其研究方法被广泛应用,同时也为中国参加国际气候变化谈判提供了实质性科学数据。该课题组在国内率先开展了陆地生态系统碳循环的研究：创建了“连续生物量转换因子法”,使复杂的区域森林生物量的估算简单易行[3, 17-18];建立了整合草场资源清查、野外实测以及卫星遥感数据为一体的草地碳储量的估算方法[19-20];提出了基于作物产量指标与遥感信息相结合的农作物碳储量的估算方法[18],为中国陆地碳循环的研究奠定了方法论基础。2009年,研究组又采用多种方法,进一步系统研究了中国陆地生态系统的碳平衡[21],受到高度关注,并为中国CO2的减排政策提供依据。2011年,作为首席专家组成员,联合美国等多国专家,牵头对世界森林碳收支进行了估算[22],在世界范围内引起了热议。2014年,方精云课题组还利用日本森林资源清查数据,发现环境变化（主要包括CO2浓度、氮沉降、温度和降水量）显著促进了森林的生长,森林生长对环境变化的响应随森林类型和年龄的变化而不同[23]。区域碳源汇的研究一直是碳循环研究的目标。朴世龙等首次采用自上而下的大气反演模型和自下而上的过程模型及地面资料有机结合的途径,阐明了中国陆地生态系统净吸收的二氧化碳量可以部分抵消其工业源排放量[21],受到高度关注。朴世龙等还首次提出欧亚大陆和北美大陆碳汇形成机制不一样,并阐明了欧亚和北美大陆春季和秋季温度变化的不同格局可能是导致过去20年欧亚大陆植被生长加速比北美更快的主要原因[24]。朴世龙课题组还将研究区拓展到热带,探讨了热带地区生态系统碳汇功能年际变化及其与气候之间的关系,发现最近20年热带地区生态系统碳汇的温度敏感性在增加,其敏感程度主要受降水的调节。这一成果不仅有助于了解热带生态系统碳循环对气候变化的响应过程及其机制,而且为准确估算生态系统碳循环和气候变化之间反馈提供了一个重要的理论基础[25]。
植物凋落物和木质残体是森林生态系统碳储量和碳汇的重要组分,但由于以往数据不足、缺乏有效的研究方法,致使中国森林植物残体碳储量及其变化缺乏准确的估算,从而限制了中国森林生态系统碳收支的全面评估。方精云课题组对中国森林植被、土壤、凋落物和木质残体碳密度进行了系统调查,并结合森林清查和遥感数据,首次量化了中国森林凋落物碳和木质残体的碳储量及其变化,发现其碳储量约为9.3亿t C,并以每年670万t C的速率增长。该成果填补了中国森林生态系统碳收支研究的空白[26]。此外,王娓课题组还通过建立全球根和叶凋落物分解的数据库,探讨分解速率常数和气候、初始凋落物质量和生物因子的关系。发现温度在调节叶凋落物分解正反馈方面发挥关键作用,粗根的分解较细根更加受到气候因素的影响。该研究首次提出了未来在预测地下碳排放对气候变化响应时,区分粗根和细根的重要性[27-28]。
土壤呼吸是陆地生态系统碳释放的重要过程。北京大学在土壤碳循环方面也有长期的研究基础。王娓课题组系统研究了温带季节性积雪覆盖生态系统冬季土壤碳排放对年碳排放的贡献,发现冬季土壤碳排放是不可忽视的地气CO2交换过程[29],冬季低温下具有更高的土壤微生物生物量和潜在胞外酶活力,土壤微生物区系组成的改变是影响低温条件下土壤碳排放的一个关键驱动因素,这一结果挑战了传统观念。此外,王娓课题组还通过建立全球森林和草地生态系统土壤呼吸的数据库,量化了土壤碳排放对温度和降水变化的响应,发现土壤碳排放随温度升高呈现出线性增长,但随降水的增加呈现非线性响应[30-31];根系呼吸比微生物呼吸具有更高的温度敏感性,长期以来采用土壤总呼吸的Q10高估了土壤有机质分解对温度变化的敏感性[31]。贺金生研究组利用先进的土壤呼吸连续监测技术,首次对青藏高原高寒草甸非生长季的土壤呼吸进行了研究,发现尽管非生长季长达半年左右,但高寒草甸非生长季土壤呼吸量为82~89 g C m-2 yr-1,占全年呼吸总量的11.8%~13.2%。非生长季年土壤呼吸量可以用土壤表层积温来很好的预测[32]。
2.3 生物多样性及其保护
物种多样性的大尺度格局及其成因一直吸引着全球的生态学家和生物地理学家,但由于其复杂性,这一问题仍是生态学的未解难题之一。自20世纪90年代中期开始,方精云课题组致力于中国植物多样性分布规律及其机制的研究,整合各类相关项目,克服重重困难,独自发起并实施了一项浩瀚的多样性研究计划——“北京大学山地植物多样性研究计划”（PKU-PSD计划）,生态学系多位在职教员,如沈泽昊、唐志尧、郑成洋、吉成均等参与了该计划。通过近20年的艰苦努力,该计划采用统一的研究方法和技术方案,对遍布全国的65座重要山地和约300个草原地点进行了植物多样性和群落结构的系统调查,共获得森林样方1600多个,草地样方1500余个。同时,方精云、王志恒、唐志尧等与全国各地的科研人员合作,建立了含有全部中国木本植物（共11405种）的“中国木本植物分布数据库”,出版了《中国木本植物分布图集》[33]。基于这些资料,系统研究了中国山地植物多样性分布格局[34-37]及植物群落的构建机制[38],初步阐明了中国山地生物多样性分布格局、物种共存与多样性维持机制。该成果在“生物多样性”上面出版了两本专集,在Ecography上出版一本专辑,在多样性格局的形成机制方面取得了一系列重要发现。同时,系统地研究了中国木本植物物种多样性的大尺度地理格局及其成因,检验了生态学代谢理论对木本植物多样性格局的适用性,揭示了生态学代谢理论的尺度效应,发展了其理论框架,创建了多样性—温度—面积的统一机制性模型[39]。在生物多样性的热点地区研究方面,贺金生课题组对青藏高原高寒草地的生物多样性开展了系列研究,包括植物[40]、真菌[41]、土壤动物[42]等在青藏高原的分布和主要控制因素。研究组进一步利用野外大范围的调查取样,结合室内高通量测序等技术,探讨了生态系统中生物因素（植物、动物、细菌、菌根真菌和古菌多样性）和非生物因素（气候和土壤）对生态系统多功能性的相对贡献[43]。该研究强调了地上与地下生物多样性对生态系统多功能性的联合效应比两者的单独效应更强[43]。
生物多样性的形成与维持机制是生态学研究的核心议题。传统观点认为生态位分化是物种共存的基础。王少鹏等基于物种谱系年龄与多度关系,对中性理论进行了分析检验。理论分析表明,在不同种化模式下,中性群落中物种年龄与其种群大小（个体数量）呈负相关或无相关。然而,巴拿马地区530个热带树种的谱系年龄和种群大小呈显著的正相关,从而否定了中性理论的预测。为此,该研究引入种化速率的种间差异,对中性模型进行了理论扩展。在扩展模型中,种化速率低的物种在群落演化中体现出相对优势,因而具有较大的种群。这最终导致物种年龄与种群大小呈现正相关,从而对经验格局给出了机制解释[44]。
唐志尧课题组通过数字化构建了中国现有自然保护区空间数据库,在此基础上,利用精确的物种分布数据,确定了中国生物多样性分布热点地区及保护空白;通过分析中国木本植物、兰科植物以及生态系统在保护区中的覆盖状况,评价了中国现有国家级自然保护区对物种多样性与生态系统多样性的体现程度[45-49]。
2.4 植物化学计量学
植物化学计量学研究是生态系统功能研究的重要途径。早在1995年,方精云在参加中国首次北极科学考察时就开始关注植物和环境中重要化学元素的分布及相互关系。2005年,方精云课题组研究发现中国植物叶片的磷含量显著低于世界平均水平,导致氮磷比显著高于世界平均值;中国土壤的磷含量低是导致植物氮磷比偏高的主要原因[50]。基于中国植物多元素地理格局及其生态驱动机制的研究,方精云课题组通过植物营养生态学研究的一种新方法提出了植物养分平衡假说——“限制元素稳定性假说”（Stability of Limiting Elements Hypothesis）[50]。该研究不仅揭示了大尺度环境梯度中植物所受的基本生态化学计量（养分平衡）的限制,在植物营养领域也有潜在的应用价值。方精云课题组还将植物化学计量研究由陆地拓展到水体。通过综合全球数据,发现在氮磷等化学物质的过量输入和复杂的生物地球化学循环过程的共同作用下,人为活动引起的富营养化导致了淡水水体和水生植物的氮磷含量的增加,却降低了它们的氮磷比值。这些结果表明人为活动可以改变淡水生态系统的限制因子,进而影响到淡水生态系统的结构、功能和动态。通过淡水径流输送的方式,潜在地影响到河口和滨海地区的食物网结构或养分循环。该研究强调了养分管理工作的重要性,并对控制和治理富营养化具有启示意义[51]。
唐志尧课题组则将植物化学计量学研究在不同的生命组建水平进行了拓展,通过大量调查和实测数据,研究了中国主要陆地植物不同器官之间化学计量特征的关系[52-54],并首次开展了群落层次的植物化学计量特征大尺度格局研究[55]。
2.5 植物地理学研究
北京大学的植被地理学研究具有良好的传统,尤其是在干旱半干旱区植被地理的研究方面做出了开创性的工作。早在1961-1965年,北京大学自然地理专业组织了毛乌素沙区自然条件及其改良利用综合考察,陈昌笃负责完成了《毛乌素沙区植被与植物资源》考察报告[56]。该报告系统地总结了毛乌素沙区的植物区系、植物群落类型、植被演替规律,探讨了植被的水平和垂直分布规律,明确指出了巴彦淖—盐场堡一线为荒漠草原和典型草原的分界线[57]。20世纪70年代末以来,北京大学植物地理小组系统地开展了新疆的荒漠和草原植被研究。陈昌笃系统地总结了中国的荒漠类型,首次从气候—植被—土壤系统的角度提出了中国的荒漠存在三种主要类型：半荒漠（或草原化荒漠）、普通荒漠（或典型荒漠）、极旱荒漠,并划定了其分布界限[58]。北京大学植物地理小组还对中国典型荒漠和极旱荒漠的植物区系和群落特征进行了较为系统的研究[58-60]。崔海亭等参与了内蒙古草场资源遥感应用研究,这是中国最早的生态遥感研究之一。有关干旱、半干旱区的植物地理研究一直得到了延续,刘鸿雁课题组系统地研究了中国北方林草交错带的植被格局与成因[61-63]。北京大学植物地理学另一重要的贡献是以林线（高山林线和干旱林线）作为突破口,通过引入孢粉和树木年轮等手段,将植物地理格局与植被历史演化结合起来,在国内率先提倡第四纪生态学研究,从而实现了植物地理学研究与全球变化研究的有机结合[64]。作为森林生长的极限,林线对气候变化敏感,在全球变化研究中备受关注。早在20世纪80年代,崔海亭提出了高山林线植被的判定标志[65];90年代开始,崔海亭组织了太白山、五台山高山林线的研究,出版了专著《山地生态学与高山林线研究》[66]。此后,刘鸿雁等进一步研究了天山、阿尔泰山的高山林线,并探讨了高山林线的森林生长与更新[67-68]。在高山林线的植被演化方面,提出了东亚夏季风的强弱决定林线植被组成的演化而冬季风的强弱则影响了林线的位置变化[69]。有关林草交错带的研究也一直延续下来并与全球变化研究结合[70]。刘鸿雁等对亚洲内陆地区林草交错带（干旱林线）树木生长的系统总结表明,半干旱区树木生长因为生长季前期和初期的干旱自1994年以来出现了显著的生长衰退以至普遍的森林死亡,而在半湿润区则不出现这一现象[71],该研究被广泛引用并收入IPCC第五次评估报告。基于沉积物孢粉和炭屑的分析,刘鸿雁课题组提出了火等干扰因素在林草交错带植被动态中的决定性作用[72],据此解释了植被动态对气候变化非线性响应的成因,对预测未来全球变化背景下敏感地区森林的动态具有重要意义[73]。
在植被—气候关系和植被区划方面,方精云等也提出了创新性的观点。在早期系统地研究了中国植被—气候关系的基础上[74],他指出了秦岭—淮河一线作为暖温带和亚热带界限是不合理的[75]。由于温度和降水具有类似的梯度变化,降水也影响到植被的温度地带性。从植被性质以及水热条件来看,长江一线作为中国东部地区亚热带和暖温带的界限具有合理性[75]。
在植被地理学研究开拓创新的同时,北京大学研究团队坚持在关键地区开展大规模植被调查。半个多世纪以来,在沙地和沙漠植被、山地植被方面积累了大量的基础资料。自2011年以来,刘鸿雁负责领导了十所高校和研究所完成了科技部基础性工作专项“华北地区自然植物群落资源综合考察”,对广义的华北地区的植物群落进行了全面清查、精查和基准点调查,完成植物群落样方10000余个,全面评价了华北地区的植物资源分布及保护利用现状,正在出版著作《华北地区植物群落图志》。方精云、唐志尧、吉成均、郑成洋、朱江玲等参加了该项目。21世纪初以来,沈泽昊课题组全面开展了中国西南干热河谷植物地理学研究,系统地揭示了区域植被和生物多样性格局,探讨了其成因,相关研究成果在《生物多样性》上出版专辑[76]。除了大规模的野外调查以外,一些新的手段也被引入植物地理学研究,方精云课题组利用星载激光雷达数据,揭示了全球森林冠层高度的地理分布,发现水分是森林高度的主要决定因素[77]。
2.6 景观生态学与城市生态学
陈昌笃是中国最早倡导景观生态学的****之一[78-79]。早在20世纪80年代,陈昌笃连续发表了《论地生态学》和《再论地生态学》,提出了将生态学划分为生物生态学、地生态学、全球生态学的三分法,并指出三类生态学代表三个空间水平。他进一步提出了地生态学研究的8个核心问题：人工生态系统研究、生物指示现象研究、地生态学制图、生态监测、生态预测、生态规划与设计、生态影响评价。他也最早将地生态学的思想应用于城市化等领域[80]。过去20多年以来,北京大学景观生态教研室（现生态学系）的师生一直活跃在景观生态学的前沿。曾辉课题组利用遥感、GIS结合模型方法,对中国发达地区快速城市化过程的景观动态、机制及其生态效应进行了创新性研究;其对城乡混合景观动态过程的生态效应的深入研究,是国内城市景观生态研究领域中的代表性工作[81]。进入21世纪,随着中国快速城市化和工业化过程的不断推进,曾辉课题组利用景观生态学基本理论和方法,开展高强度人为活动区域的生态评价、规划和设计,为地区社会经济发展提供科学决策依据,成为北京大学景观生态学研究的一个新的学科发展亮点。山地是中国自然景观的重要特征,沈泽昊课题组长期研究山地地形复杂性对森林火烧、植物种子扩散与更新动态等空间过程的影响[82]及其对生物多样性格局的多尺度效应[83-84],形成了以山地景观生态为特色的研究方向。
3 学科发展和国际影响
20世纪70年代末期至90年代初期,陈昌笃和崔海亭分别开展干旱区和半干旱区植物地理学研究,在新疆干旱区的植物区系和植被地理、内蒙古草地资源的遥感研究、北方生态过渡带研究方面做出了突出贡献。1991年,以陈昌笃和崔海亭为主要学术带头人,成立了中国高等院校中的第一个景观生态学研究室;在国内率先倡导开展景观生态学、城市生态学、全球生态学研究,推动了宏观生态学研究的发展;并在生物多样性和生态遥感研究领域亦做出突出贡献。陈昌笃曾担任第四届中国生态学会理事长,在任期间大力推动生态学的理论为可持续发展的实践服务。20世纪90年代末以来,通过有效的人才引进,北京大学不但保持了传统研究领域的优势,还开辟了一系列与国际前沿接轨的新兴研究方向。学术带头人方精云在国内较早地开展了植被与气候关系的定量化研究;最早系统地开展了陆地生态系统碳循环的研究。近年来,方精云领导的研究小组在中国陆地生态系统碳循环和植被生产力方面的研究取得突破性进展,在国际国内学术界和社会产生了重大影响。朴世龙教授围绕全球变化的生态响应在国际顶尖刊物发表了一系列论文,产生了广泛的国际影响,其成果曾被评为“中国高校十大科技进展”。
按照基本科学指标数据库（Essential Science Indicators, ESI）的统计,北京大学生态学与环境科学的学科排名在全球居前0.4%,进入世界一流行列。北大的生态学科与国际著名高校和研究机构有着广泛的合作关系。
4 对国家需求的贡献
北京大学的相关研究工作在气候变化、生物多样性保护、可持续发展等方面始终结合国家需求。在气候变化的应对方面,方精云参与了对IPCC报告的独立调查,此项工作不仅对联合国和科学界产生了重要的影响,有助于中国气候变化适应对策的制定。此外,受中国科学院咨询与评议委员会的委托,方精云团队对中国及世界主要国家的碳排放形势进行了深入细致的分析和预测,针对哥本哈根气候谈判,向国务院提交了建议书,就中国政府应采取的立场和应对策略提出了相关建议。建议书引起了中央政府的高度重视,为解决国家重大战略需求发挥了作用。在自然保护方面,由陈昌笃教授主持编撰的一系列关于生物多样性保护文件,如《中国自然保护纲要》[85]、《中国生物多样性国情咨询报告》[86],已成为中国生物多样性保护的纲领性文件。在可持续发展的研究方面,早期崔海亭等参与的内蒙古草场资源综合调查与制图、“三北防护林”遥感应用研究获得了国家科技进步三等奖（集体）、教育部和内蒙古自治区的科技进步一等奖,近年来曾辉等相关研究团队曾先后承担了一大批国家和地方的重要科研生产项目,先后6次获得省部级以上的各类科研奖励。5 未来展望
经过半个多世纪,尤其是最近15年的建设,北京大学的植物地理学研究不仅自身得到了迅速发展,而且推动了生态学的发展。生态学研究的硬件条件得到了根本改善,为学科的未来发展创造了条件。目前已具备植物生理生态学、树轮生态学、植物化学、古生态学等实验条件,群落、景观和生态系统生态学的模型模拟条件。作为北京大学“地表过程与分析模拟教育部重点实验室”的一部分,具备先进的生态学过程分析的实验条件,建设了塞罕坝生态站等观测设施和全国树木生长、森林施肥实验平台,正在建设高山林线监测等平台。未来的学科发展将紧密结合学科前沿和国家需求,加强一流学科建设。中国得天独厚的自然地理条件和丰富的动植物资源为生物地理学和生态学研究提供了广阔的平台,同时,中国快速经济发展导致的一系列生态与环境问题也为生态学研究带来迫切的需求和巨大的挑战。北京大学未来的生态学研究将充分利用中国的自然研究平台,密切结合社会经济发展中的生态与环境问题,以过去特别是近期的研究积累为基础,加强不同尺度生态学研究方法的整合,重视生态系统与生物多样性理论研究,深化机理机制研究,同时围绕区域生态退化开展生态修复的应用研究。
The authors have declared that no competing interests exist.
参考文献 原文顺序
文献年度倒序
文中引用次数倒序
被引期刊影响因子
| [1] | We used a simple process model and satellite data to explore trends in China's terrestrial net primary production (NPP). We found that the country's terrestrial NPP increased by 18.7% from 1982 to 1999. Evidence for this major increase also came from crop yields and forest inventory surveys, and much of it appeared to be the result of a lengthening of the growing season. Plant growth also increased during the middle of the growing season, but to a lesser extent. Historical NPP trends indicate a great deal of spatial heterogeneity, increasing significantly over an area covering 30.8% of China during the past 18 years, but decreasing in areas undergoing rapid urbanization. |
| [2] | In this paper, we analyzed interannual variations of normalized difference vegetation index (NDVI) and their relationships with climatic variables (temperature and precipitation) and human activity in China between 1982 and 1999. Monthly and seasonal NDVI increased significantly at both the country and biome scales over the study period. NDVI shows the largest increase (14.4% during the 18 years and a trend of 0.0018 yr) over 85.9% of the total study area in spring and the smallest increase (5.2% with a trend of 0.0012 yr) over 72.2% of the area in summer. The NDVI trends show a marked heterogeneity corresponding to regional and seasonal variations in climates. There is about a 3-month lag for the period between the maximum trend in temperature (February) and that in NDVI (April or May) at the country and biome scales. Human activity (urbanization and agricultural practices) also played an important role in influencing the NDVI trends over some regions. Rapid urbanization resulted in a sharp decrease in NDVI in the Yangtze River and Pearl River deltas, while irrigation and fertilization may have contributed to the increased NDVI in the North China plain. |
| [3] | . In this study, we explore the trend in desertification in China from 1982 to 1999 by investigating the changes in area and normalized difference vegetation index (NDVI) of arid and semiarid regions, using NDVI time series data sets and climatic variables. We use Thornthwaite moisture index (I) to define the arid and semiarid region as I<= -40 and -40 < I<= -20, respectively. Rainy season NDVI (May to October NDVI) increased in most areas of arid and semiarid regions over the past two decades, accounting for 72.3% and 88.2% of total area of arid and semiarid regions, respectively. Compared to that in the early 1980s, the area of arid and semiarid regions decreased by 23 10km(6.9%) and 7 10km(7.9%) by the end of the 1990s, suggesting a reversal of desertification processes in these two climate regions. Transformation from warm-arid to warm-wet climate and weakened disturbance from human activities may be the major causes of this declined trend. |
| [4] | Vegetation net primary production (NPP) derived from a carbon model (Carnegie–Ames–Stanford Approach, CASA) and its interannual change in the Qinghai-Xizang (Tibetan) Plateau were investigated in this study using 1982–1999 time series data sets of normalized difference vegetation index (NDVI) and paired ground-based information on vegetation, climate, soil, and solar radiation. The 18-year averaged annual NPP over the plateau was 125 g C m 612 yr 611 , decreasing from the southeast to the northwest, consistent with precipitation and temperature patterns. Total annual NPP was estimated between 0.183 and 0.244 Pg C over the 18 years, with an average of 0.212 Pg C (1 Pg = 10 15 g). Two distinct periods (1982–1990 and 1991–1999) of NPP variation were observed, separated by a sharp reduction during 1990–1991. From 1982 to 1990, annual NPP did not show a significant trend, while from 1991 to 1999 a marked increase of 0.007 Pg C yr 612 was observed. NPP trends for most vegetation types resembled that of the whole plateau. The largest annual NPP increase during 1991–1999 appeared in alpine meadows, accounting for 32.3% of the increment of the whole region. Changes in solar radiation and temperature significantly influenced NPP variation, suggesting that solar radiation may be one of the major factors associated with changes in NPP. |
| [5] | |
| [6] | Global environmental change is rapidly altering the dynamics of terrestrial vegetation, with consequences for the functioning of the Earth system and provision of ecosystem services. Yet how global vegetation is responding to the changing environment is not well established. Here we use three long-term satellite leaf area index (LAI) records and ten global ecosystem models to investigate four key drivers of LAI trends during 1982-2009. We show a persistent and widespread increase of growing season integrated LAI (greening) over 25% to 50% of the global vegetated area, whereas less than 4% of the globe shows decreasing LAI (browning). Factorial simulations with multiple global ecosystem models suggest that COfertilization effects explain 70% of the observed greening trend, followed by nitrogen deposition (9%), climate change (8%) and land cover change (LCC) (4%). COfertilization effects explain most of the greening trends in the tropics, whereas climate change resulted in greening of the high latitudes and the Tibetan Plateau. LCC contributed most to the regional greening observed in southeast China and the eastern United States. The regional effects of unexplained factors suggest that the next generation of ecosystem models will need to explore the impacts of forest demography, differences in regional management intensities for cropland and pastures, and other emerging productivity constraints such as phosphorus availability. |
| [7] | The surface air temperature response to vegetation changes has been studied for the extreme case of land-cover change; yet, it has never been quantified for the slow but persistent increase in leaf area index (LAI) observed over the past 30 years (Earth greening). Here we isolate the fingerprint of increasing LAI on surface air temperature using a coupled land-atmosphere global climate model prescribed with satellite LAI observations. We find that the global greening has slowed down the rise in global land-surface air temperature by 0.09 +/- 0.02 C since 1982. This net cooling effect is the sum of cooling from increased evapotranspiration (70%), changed atmospheric circulation (44%), decreased shortwave transmissivity (21%), and warming from increased longwave air emissivity (-29%) and decreased albedo (-6%). The global cooling originated from the regions where LAI has increased, including boreal Eurasia, Europe, India, northwest Amazonia, and the Sahel. Increasing LAI did not, however, significantly change surface air temperature in eastern North America and East Asia, where the effects of large-scale atmospheric circulation changes mask local vegetation feedbacks. Overall, the sum of biophysical feedbacks related to the greening of the Earth mitigated 12% of global land-surface warming for the past 30 years. |
| [8] | Abstract Earlier spring leaf unfolding is a frequently observed response of plants to climate warming. Many deciduous tree species require chilling for dormancy release, and warming-related reductions in chilling may counteract the advance of leaf unfolding in response to warming. Empirical evidence for this, however, is limited to saplings or twigs in climate-controlled chambers. Using long-term in situ observations of leaf unfolding for seven dominant European tree species at 1,245 sites, here we show that the apparent response of leaf unfolding to climate warming (ST, expressed in days advance of leaf unfolding per °C warming) has significantly decreased from 1980 to 2013 in all monitored tree species. Averaged across all species and sites, ST decreased by 40% from 4.0 ± 1.8 days °C(-1) during 1980-1994 to 2.3 ± 1.6 days °C(-1) during 1999-2013. The declining ST was also simulated by chilling-based phenology models, albeit with a weaker decline (24-30%) than observed in situ. The reduction in ST is likely to be partly attributable to reduced chilling. Nonetheless, other mechanisms may also have a role, such as 'photoperiod limitation' mechanisms that may become ultimately limiting when leaf unfolding dates occur too early in the season. Our results provide empirical evidence for a declining ST, but also suggest that the predicted strong winter warming in the future may further reduce ST and therefore result in a slowdown in the advance of tree spring phenology. |
| [9] | |
| [10] | Wheat growth is sensitive to temperature, but the effect of future warming on yield is uncertain. Here, focusing on China, we compiled 46 observations of the sensitivity of wheat yield to temperature change (S, yield change per °C) from field warming experiments and 102 Sestimates from local process-based and statistical models. The average Sfrom field warming experiments, local process-based models and statistical models is -0.7+/-7.8(+/-s.d.)% per °C, -5.7+/-6.5% per °C and 0.4+/-4.4% per °C, respectively. Moreover, Sis different across regions and warming experiments indicate positive Svalues in regions where growing-season mean temperature is low, and water supply is not limiting, and negative values elsewhere. Gridded crop model simulations from the Inter-Sectoral Impact Model Intercomparison Project appear to capture the spatial pattern of Sdeduced from warming observations. These results from local manipulative experiments could be used to improve crop models in the future. |
| [11] | Abstract Wheat, rice, maize, and soybean provide two-thirds of human caloric intake. Assessing the impact of global temperature increase on production of these crops is therefore critical to maintaining global food supply, but different studies have yielded different results. Here, we investigated the impacts of temperature on yields of the four crops by compiling extensive published results from four analytical methods: global grid-based and local point-based models, statistical regressions, and field-warming experiments. Results from the different methods consistently showed negative temperature impacts on crop yield at the global scale, generally underpinned by similar impacts at country and site scales. Without CO 2 fertilization, effective adaptation, and genetic improvement, each degree-Celsius increase in global mean temperature would, on average, reduce global yields of wheat by 6.0%, rice by 3.2%, maize by 7.4%, and soybean by 3.1%. Results are highly heterogeneous across crops and geographical areas, with some positive impact estimates. Multimethod analyses improved the confidence in assessments of future climate impacts on global major crops and suggest crop- and region-specific adaptation strategies to ensure food security for an increasing world population. |
| [12] | Abstract Freshwater lakes store water for human use and agricultural irrigation and provide habitats for aquatic fauna and flora. However, a number of these lakes have been degraded by human activities at a rapid rate. Here, we used historical land cover information and remotely sensed data to explore a 7-decade (between 1930s and 1998) shrinkage and fragmentation of Dongting Lake, the second largest freshwater lake in China, located in the drainage basin of Central Yangtze River. The water surface area of Dongting Lake decreased by 49.2%, from 4955 km2 in the 1930s to 2518 km2 in 1998, with an average decrease rate of 38.1 km2/yr in the past 7 decades. The lake was also fragmented, as indicated by a decreasing mean patch size from 4.2 km2 in the 1930s to 1.7 km2 in 1998. The degradation of the lake is largely attributed to a rapidly growing human population in the lake region that led to extensive impoldering. The degradation of the lake has resulted in negative ecological consequences, such as frequent flooding, a decline of biodiversity, and extinction of some endemic species. Our results also suggest that lake restoration projects implemented in this region since the end of the 1990s will help to decrease the lake degradation. |
| [13] | Abstract Lakes are widely distributed on the Mongolian Plateau and, as critical water sources, have sustained Mongolian pastures for hundreds of years. However, the plateau has experienced significant lake shrinkage and grassland degradation during the past several decades. To quantify the changes in all of the lakes on the plateau and the associated driving factors, we performed a satellite-based survey using multitemporal Landsat images from the 1970s to 2000s, combined with ground-based censuses. Our results document a rapid loss of lakes on the plateau in the past decades: the number of lakes with a water surface area >1 km(2) decreased from 785 in the late 1980s to 577 in 2010, with a greater rate of decrease (34.0%) in Inner Mongolia of China than in Mongolia (17.6%). This decrease has been particularly pronounced since the late 1990s in Inner Mongolia and the number of lakes >10 km(2) has declined by 30.0%. The statistical analyses suggested that in Mongolia precipitation was the dominant driver for the lake changes, and in Inner Mongolia coal mining was most important in its grassland area and irrigation was the leading factor in its cultivated area. The deterioration of lakes is expected to continue in the following decades not only because of changing climate but also increasing exploitation of underground mineral and groundwater resources on the plateau. To protect grasslands and the indigenous nomads, effective action is urgently required to save these valuable lakes from further deterioration. |
| [14] | The widely distributed 241 lakes in the semiarid region of China bordering the Asian Gobi desert provide an irreplaceable environment for the region's human inhabitants, livestock, and wildlife. Using satellite imagery, we tracked the changing areas of lake water and freshwater/salty marshes during the last four decades and correlated observed changes with concurrent temperature and precipitation. On average, most of the lake size groups across different subregions showed a reduction in area from the 1970s to 2000s, particularly from the 1990s to 2000s (P < 0.05); 121 of the 241 lakes became fully desiccated at the end of the 2000s. Our results confirmed the prevalence of drought-induced lake shrinkage and desiccation at a regional scale, which has been sustained since the year 2000, and highlighted an accelerated shrinkage of individual lakes by human water use in the agriculture-dominated regions. Lake waters have become salinized, and freshwater marsh has been replaced by salty marsh, threatening the populations of endangered waterfowl species such as the red-crowned crane as well as the aquatic ecosystem. Although the dry lakebeds are a potential source of dust, the establishment of salty marsh on bare lake beds could have partially reduced dust release due to the increase in vegetation cover. |
| [15] | Anthropogenic climate change has emerged as a critical environmental problem, prompting frequent investigations into its consequences for various ecological systems. Few studies, however, have explored the effect of climate change on ecological stability and the underlying mechanisms. We conduct a field experiment to assess the influence of warming and altered precipitation on the temporal stability of plant community biomass in an alpine grassland located on the Tibetan Plateau. We find that whereas precipitation alteration does not influence biomass temporal stability, warming lowers stability through reducing the degree of species asynchrony. Importantly, biomass temporal stability is not influenced by plant species diversity, but is largely determined by the temporal stability of dominant species and asynchronous population dynamics among the coexisting species. Our findings suggest that ongoing and future climate change may alter stability properties of ecological communities, potentially hindering their ability to provide ecosystem services for humanity. Temporal stability of plant communities is driven by several mechanisms and may be influenced by climate change. Here it is shown that warming, but not precipitation, reduces species asynchrony in an alpine grassland, leading to lower biomass temporal stability. |
| [16] | |
| [17] | The location and mechanisms responsible for the carbon sink in northern mid-latitude lands are uncertain. Here, we used an improved estimation method of forest biomass and a 50-year national forest resource inventory in China to estimate changes in the storage of living biomass between 1949 and 1998. Our results suggest that Chinese forests released about 0.68 petagram of carbon between 1949 and 1980, for an annual emission rate of 0.022 petagram of carbon. Carbon storage increased significantly after the late 1970s from 4.38 to 4.75 petagram of carbon by 1998, for a mean accumulation rate of 0.021 petagram of carbon per year, mainly due to forest expansion and regrowth. Since the mid-1970s, planted forests (afforestation and reforestation) have sequestered 0.45 petagram of carbon, and their average carbon density increased from 15.3 to 31.1 megagrams per hectare, while natural forests have lost an additional 0.14 petagram of carbon, suggesting that carbon sequestration through forest management practices addressed in the Kyoto Protocol could help offset industrial carbon dioxide emissions. |
| [18] | Distribution of vegetation is closely coupled with climate; the climate controls distribution of vegetation and the vegetation type reflects regional climates. To reveal vegetation_climate relationships is the foundation for understanding the vegetation distribution and theoretically serving vegetation regionalization. Vegetation regionalization is a theoretical integration of vegetation studies and provides a base for physiogeographical regionalization as well as agriculture and forestry regionalization. Based on a brief historical overview on studies of vegetation_climate relationships and vegetation regionalization conducted in China, we review the principles, bases and major schemes of previous vegetation regionalization and discuss on several contentious boundaries of vegetation zones in the present paper. We proposed that, under the circumstances that the primary vegetation has been destroyed in most parts of China, the division of vegetation zones/regions should be based on the distribution of primary and its secondary vegetation types and climatic indices that delimit distribution of the vegetation types. This not only reveals the closed relationship between vegetation and climate, but also is feasible practically. Although there still are divergence of views on the name and their boundaries of the several vegetation zones, it is commonly accepted that there are eight major vegetation regions in China, i.e. cold temperate needleleaf forest region, temperate needleleaf and broadleaf mixed forest region, warm temperate deciduous broadleaf forest region, subtropical evergreen broadleaf forest region, tropical monsoon forest and rain forest region, temperate steppe region, temperate desert region, and Qinghai_Xizang (Tibetan) Plateau high_cold vegetation region. Analyzing characteristics of vegetation and climate of major vegetation boundaries, we suggested that: 1) Qinling Mountain_Huaihe River line is an important arid/humid climatic, but not a thermal climatic boundary, and thus can not also be regarded as the northern limit of the subtropical vegetation zone; 2) the northern limit of subtropical vegetation zone in China is along the northern coast of the Yangtze River, from Hangzhou Bay, via Taihu Lake, Xuancheng and Tongling in Anhui Province, through by southern slope of the Dabie Mountains, to Wuhan and its west, coinciding with a warmth index ( WI ) value of 130-140 onth; 3) the tropical region is limited in a very small area in southeastern Hainan Island and southern edge of Taiwan Island; and 4) considering a significant difference in climates between the southern and northern parts of the warm temperate zone, we suggested that the warm temperate zone in China is divided into two vegetation regions, deciduous broadleaf woodland region and deciduous and evergreen broadleaf mixed forest region, the Qinling Mountain_Huaihe River line being as their boundary. We also claimed that the zonal vegetation in North China is deciduous broadleaf woodland. Finally, we emphasized the importance of dynamic vegetation regionalization linked to climate changes. |
| [19] | In this paper, we use growing season Normalized Difference Vegetation Index (NDVI) as an indicator of plant growth to quantify the relationships between vegetation production and intra-annual precipitation patterns for three major temperate biomes in China: grassland, deciduous broadleaf forest, and deciduous coniferous forest. With increased precipitation, NDVI of grassland and deciduous broadleaf forest increased, but that of deciduous coniferous forest decreased. More frequent precipitation significantly increased growth of grassland and deciduous broadleaf forest, but did not alter that of deciduous coniferous forest at low precipitation levels and constrained its growth at high precipitation levels. The relationships between NDVI and average precipitation per event were opposite to those between NDVI and precipitation frequency. Such nonlinear feedback suggests that the responses of vegetation production to changes in precipitation patterns differ by both biome type and precipitation amount. |
| [20] | The significant worldwide increase in observed river runoff has been tentatively attributed to the stomatal "antitranspirant" response of plants to rising atmospheric CO60 [Gedney N, Cox PM, Betts RA, Boucher O, Huntingford C, Stott PA (2006) Nature 439: 835-838]. However, CO60 also is a plant fertilizer. When allowing for the increase in foliage area that results from increasing atmospheric CO60 levels in a global vegetation model, we find a decrease in global runoff from 1901 to 1999. This finding highlights the importance of vegetation structure feedback on the water balance of the land surface. Therefore, the elevated atmospheric CO60 concentration does not explain the estimated increase in global runoff over the last century. In contrast, we find that changes in mean climate, as well as its variability, do contribute to the global runoff increase. Using historic land-use data, we show that land-use change plays an additional important role in controlling regional runoff values, particularly in the tropics. Land-use change has been strongest in tropical regions, and its contribution is substantially larger than that of climate change. On average, land-use change has increased global runoff by 0.08 mm/year05 and accounts for ≈50% of the reconstructed global runoff trend over the last century. Therefore, we emphasize the importance of land-cover change in forecasting future freshwater availability and climate. |
| [21] | Global terrestrial ecosystems absorbed carbon at a rate of 1-4 Pg yr(-1) during the 1980s and 1990s, offsetting 10-60 per cent of the fossil-fuel emissions. The regional patterns and causes of terrestrial carbon sources and sinks, however, remain uncertain. With increasing scientific and political interest in regional aspects of the global carbon cycle, there is a strong impetus to better understand the carbon balance of China. This is not only because China is the world's most populous country and the largest emitter of fossil-fuel CO(2) into the atmosphere, but also because it has experienced regionally distinct land-use histories and climate trends, which together control the carbon budget of its ecosystems. Here we analyse the current terrestrial carbon balance of China and its driving mechanisms during the 1980s and 1990s using three different methods: biomass and soil carbon inventories extrapolated by satellite greenness measurements, ecosystem models and atmospheric inversions. The three methods produce similar estimates of a net carbon sink in the range of 0.19-0.26 Pg carbon (PgC) per year, which is smaller than that in the conterminous United States but comparable to that in geographic Europe. We find that northeast China is a net source of CO(2) to the atmosphere owing to overharvesting and degradation of forests. By contrast, southern China accounts for more than 65 per cent of the carbon sink, which can be attributed to regional climate change, large-scale plantation programmes active since the 1980s and shrub recovery. Shrub recovery is identified as the most uncertain factor contributing to the carbon sink. Our data and model results together indicate that China's terrestrial ecosystems absorbed 28-37 per cent of its cumulated fossil carbon emissions during the 1980s and 1990s. |
| [22] | |
| [23] | Forests in the middle and high latitudes of the northern hemisphere function as a significant sink for atmospheric carbon dioxide (CO2). This carbon (C) sink has been attributed to two processes: age-related growth after land use change and growth enhancement due to environmental changes, such as elevated CO2, nitrogen deposition, and climate change. However, attribution between these two processes is largely controversial. Here, using a unique time series of an age-class dataset from six national forest inventories in Japan and a new approach developed in this study (i.e., examining changes in biomass density at each age class over the inventory periods), we quantify the growth enhancement due to environmental changes and its contribution to biomass C sink in Japan's forests. We show that the growth enhancement for four major plantations was 4.0 7.7 Mg C a(-1) from 1980 to 2005, being 8.4-21.6% of biomass C sequestration per hectare and 4.1-35.5% of the country's total net biomass increase of each forest type. The growth enhancement differs among forest types, age classes, and regions. Our results provide, to our knowledge, the first ground-based evidence that global environmental changes can increase C sequestration in forests on a broad geographic scale and imply that both the traits and age of trees regulate the responses of forest growth to environmental changes. These findings should be incorporated into the prediction of forest C cycling under a changing climate. |
| [24] | Temperature data over the past five decades show faster warming of the global land surface during the night than during the day(1). This asymmetric warming is expected to affect carbon assimilation and consumption in plants, because photosynthesis in most plants occurs during daytime and is more sensitive to the maximum daily temperature, T-max, whereas plant respiration occurs throughout the day(2) and is therefore influenced by both T-max and the minimum daily temperature, T-min. Most studies of the response of terrestrial ecosystems to climate warming, however, ignore this asymmetric forcing effect on vegetation growth and carbon dioxide (CO2) fluxes(3-6). Here we analyse the interannual covariations of the satellite-derived normalized difference vegetation index (NDVI, an indicator of vegetation greenness) with Tmax and Tmin over the Northern Hemisphere. After removing the correlation between Tmax and Tmin, we find that the partial correlation between Tmax and NDVI is positive in most wet and cool ecosystems over boreal regions, but negative in dry temperate regions. In contrast, the partial correlation between Tmin and NDVI is negative in boreal regions, and exhibits a more complex behaviour in dry temperate regions. We detect similar patterns in terrestrial net CO2 exchange maps obtained from a global atmospheric inversion model. Additional analysis of the long-term atmospheric CO2 concentration record of the station Point Barrow in Alaska suggests that the peak-to-peak amplitude of CO2 increased by 23 +/- 11% for a +1 degrees C anomaly in T-max from May to September over lands north of 51 degrees N, but decreased by 28 +/- 14% for a +1 degrees C anomaly in T-min. These lines of evidence suggest that asymmetric diurnal warming, a process that is currently not taken into account in many global carbon cycle models, leads to a divergent response of Northern Hemisphere vegetation growth and carbon sequestration to rising temperatures. |
| [25] | Earth system models project that the tropical land carbon sink will decrease in size in response to an increase in warming and drought during this century, probably causing a positive climate feedback. But available data are too limited at present to test the predicted changes in the tropical carbon balance in response to climate change. Long-term atmospheric carbon dioxide data provide a global record that integrates the interannual variability of the global carbon balance. Multiple lines of evidence demonstrate that most of this variability originates in the terrestrial biosphere. In particular, the year-to-year variations in the atmospheric carbon dioxide growth rate (CGR) are thought to be the result of fluctuations in the carbon fluxes of tropical land areas. Recently, the response of CGR to tropical climate interannual variability was used to put a constraint on the sensitivity of tropical land carbon to climate change. Here we use the long-term CGR record from Mauna Loa and the South Pole to show that the sensitivity of CGR to tropical temperature interannual variability has increased by a factor of 1.9 0.3 in the past five decades. We find that this sensitivity was greater when tropical land regions experienced drier conditions. This suggests that the sensitivity of CGR to interannual temperature variations is regulated by moisture conditions, even though the direct correlation between CGR and tropical precipitation is weak. We also find that present terrestrial carbon cycle models do not capture the observed enhancement in CGR sensitivity in the past five decades. More realistic model predictions of future carbon cycle and climate feedbacks require a better understanding of the processes driving the response of tropical ecosystems to drought and warming. |
| [26] | Forests play an important role in global carbon cycles. However, the lack of available information on carbon stocks in dead organic matter, including woody debris and litter, reduces the reliability of assessing the carbon cycles in entire forest ecosystems. Here we estimate that the national DOM carbon stock in the period of 2004–2008 is 92565±655465Tg, with an average density of 5.9565±650.3565Mg C65ha611. Over the past two decades from periods of 1984611988 to 2004612008, the national dead organic matter carbon stock has increased by 6.765±652.265Tg carbon per year, primarily due to increasing forest area. Temperature and precipitation increase the carbon density of woody debris, but decrease that of litter. Additionally, the woody debris increases significantly with above ground biomass and forest age. Our results can improve estimates of the carbon budget in China's forests and for better understanding of effects of climate and stand characteristics on dead organic matter distribution. Reliable estimates of the total forest carbon (C) pool are lacking due to insufficient information on dead organic matter (DOM). Here, the authors estimate that the current DOM C stock in China is 92565±655465Tg and that it grew by 6.765±652.265Tg C/yr over the past two decades primarily due to increasing forest area |
| [27] | Fine root decomposition represents a large carbon (C) cost to plants, and serves as a potential soil C source, as well as a substantial proportion of net primary productivity. Coarse roots differ markedly from fine roots in morphology, nutrient concentrations, functions, and decomposition mechanisms. Still poorly understood is whether a consistent global pattern exists between the decomposition of fine (<265mm root diameter) and coarse (≥265mm) roots. A comprehensive terrestrial root decomposition dataset, including 530 observations from 71 sampling sites, was thus used to compare global patterns of decomposition of fine and coarse roots. Fine roots decomposed significantly faster than coarse roots in middle latitude areas, but their decomposition in low latitude regions was not significantly different from that of coarse roots. Coarse root decomposition showed more dependence on climate, especially mean annual temperature (MAT), than did fine roots. Initial litter lignin content was the most important predictor of fine root decomposition, while lignin to nitrogen ratios, MAT, and mean annual precipitation were the most important predictors of coarse root decomposition. Our study emphasizes the necessity of separating fine roots and coarse roots when predicting the response of belowground C release to future climate changes. |
| [28] | Climate and initial litter quality are the major factors influencing decomposition rates on large scales. We established a comprehensive database of terrestrial leaf litter decomposition, including 785 datasets, to examine the relationship between climate and litter quality and evaluate the factors controlling decomposition on a global scale, the arid and semi-arid (AS) zone, the humid middle and humid low (HL) latitude zones. Initial litter nitrogen (N) and phosphorus (P) concentration only increased with mean annual temperature (MAT) in the AS zone and decreased with mean annual precipitation (MAP) in the HL zone. Compared with nutrient content, MAT imposed less effect on initial litter lignin content than MAP. MAT were the most important decomposition driving factors on a global scale as well as in different climatic zones. MAP only significantly affected decomposition constants in AS zone. Although litter quality parameters also showed significant influence on decomposition, their importance was less than the climatic factors. Besides, different litter quality parameters exerted significant influence on decomposition in different climatic zones. Our results emphasized that climate consistently exerted important effects on decomposition constants across different climatic zones. |
| [29] | Most soil respiration measurements are conducted during the growing season. In tundra and boreal forest ecosystems, cumulative winter soil CO 2 fluxes are reported to be a significant component of their annual carbon budgets. However, little information on winter soil CO 2 efflux is known from mid-latitude ecosystems. Therefore, comparing measurements of soil respiration taken annually versus during the growing season will improve the accuracy of ecosystem carbon budgets and the response of soil CO 2 efflux to climate changes. In this study we measured winter soil CO 2 efflux and its contribution to annual soil respiration for seven ecosystems (three forests: Pinus sylvestris var. mongolica plantation, Larix principis-rupprechtii plantation and Betula platyphylla forest; two shrubs: Rosa bella and Malus baccata; and two meadow grasslands) in a forest-steppe ecotone, north China. Overall mean winter and growing season soil CO 2 effluxes were 0.15–0.2602μmol02m 61202s 611 and 2.65–4.6102μmol02m 61202s 611, respectively, with significant differences in the growing season among the different ecosystems. Annual Q 10 (increased soil respiration rate per 1002°C increase in temperature) was generally higher than the growing season Q 10. Soil water content accounted for 84% of the variations in growing season Q 10 and soil temperature range explained 88% of the variation in annual Q 10. Soil organic carbon density to 3002cm depth was a good surrogate for SR 10 (basal soil respiration at a reference temperature of 1002°C). Annual soil CO 2 efflux ranged from 394.7602g02C02m 612 to 973.1802g02C02m 612 using observed ecosystem-specific response equations between soil respiration and soil temperature. Estimates ranged from 424.9002g02C02m 612 to 784.7302g02C02m 612 by interpolating measured soil respiration between sampling dates for every day of the year and then computing the sum to obtain the annual value. The contributions of winter soil CO 2 efflux to annual soil respiration were 3.48–7.30% and 4.92–7.83% using interpolated and modeled methods, respectively. Our results indicate that in mid-latitude ecosystems, soil CO 2 efflux continues throughout the winter and winter soil respiration is an important component of annual CO 2 efflux. |
| [30] | Quantifying global patterns of forest soil respiration (SR), its components of heterotrophic respiration (HR) and belowground autotrophic respiration (AR), and their responses to temperature and precipitation are vital to accurately evaluate responses of the terrestrial carbon balance to future climate change. There is great uncertainty associated with responses of SR to climate change, concerning the differences in climatic controls and apparent Q 10 (the factor by which respiration increases for a 1002°C increase in temperature) over HR and AR. Here, we examine available information on SR, HR, AR, the contribution of HR to SR (HR/SR), and Q 10 of SR and its components from a diverse global database of forest ecosystems. The goals were to test how SR and its two components (AR and HR) respond to temperature and precipitation changes, and to test the differences in apparent Q 10 between AR and HR. SR increased linearly with mean annual temperature (MAT), but responded non-linearly to mean annual precipitation (MAP) in naturally-regenerated forests. For every 102°C increase in MAT, overall emissions from SR increased by 24.602g02C02m 61202yr 611. When MAP was less than 81302mm, every 10002mm increase in MAP led to a release of 75.302g02C02m 61202yr 611, but the increase rate declined to 20.302g02C02m 61202yr 611 when MAP was greater than 81302mm. MAT explained less variation in AR than that in HR. The overall emissions in AR and HR for every 102°C increase in MAT, increased by 12.9 and0216.102g02C02m 61202yr 611, respectively. The AR emissions for every 10002mm increase in MAP, increased by 44.502g02C02m 61202yr 611 when MAP less than 100002mm. However, above the threshold, AR emissions stayed relatively constant. HR increased linearly by 15.002g02C02m 61202yr 611 with every 10002mm increased in MAP. The Q 10 value of SR increased with increasing depth at which soil temperature was measured up to 1002cm and was negatively correlated with HR/SR. Our synthesis suggests AR and HR differ in their responses to02temperature and precipitation change. We also emphasized the importance of information on soil temperature measurement depth when applying field estimation of Q 10 values into current terrestrial ecosystem models. Q 10 values derived from field SR measurements including AR, will likely overestimate the temperature response of HR on a future warmer earth. |
| [31] | Grasslands comprise approximately 40% of the earth's land area (excluding areas of permanent ice cover) and play a critical role in the global carbon cycle. In this paper, by reviewing literature, we quantify annual soil CO 2 efflux, contribution of root respiration to total soil respiration, apparent temperature sensitivity of soil respiration (indicated by Q 10), and turnover rates of soil organic carbon (SOC). We discuss effects of human activities (grazing, land-use changes, and fertilization) on soil respiration rates of global natural grasslands. The soil CO 2 efflux from temperate and tropical natural grasslands is 389.8 ± 45.502g C m 61 2 yr 61 1 and 601.3 ± 45.602g C m 61 2 yr 61 1 (mean ± S.E.), respectively. The contribution of root respiration to total soil respiration averages 36%, ranging from 8% to 64%. Annual soil CO 2 efflux increases with temperature and precipitation, but increased precipitation can cause a decrease in soil respiration rate in rainy regions. Mean turnover rates of SOC are 7102years in temperate grasslands and 1502years in tropical grasslands. The average Q 10 value is 2.13, with 2.23 for temperate grasslands and 1.94 for tropical grasslands. Human activities significantly affect soil respiration but the extent varies among sites. |
| [32] | Abstract The Tibetan alpine grasslands, sharing many features with arctic tundra ecosystems, have a unique non-growing-season climate that is usually dry and without persistent snow cover. Pronounced winter warming recently observed in this ecosystem may significantly alter the non-growing-season carbon cycle processes such as soil respiration ( Rs ), but detailed measurements to assess the patterns, drivers of, and potential feedbacks on Rs have not been made yet. We conducted a 4 year study on Rs using a unique Rs measuring system, composed of an automated soil CO2 flux sampling system and a custom-made container, to facilitate measurements in this extreme environment. We found that in the nongrowing season, (1) cumulative Rs was 82–8965g C m612, accounting for 11.8–13.2% of the annual total Rs ; (2) surface soil freezing controlled the diurnal pattern of Rs and bulk soil freezing induced lower reference respiration rate ( R 0) and temperature sensitivity ( Q 10) than those in the growing season (0.40–0.53 versus 0.84–1.326508mol CO2 m61265s611 for R 0 and 2.5–2.9 versus 2.9–5.6 for Q 10); and (3) the intraannual variation in cumulative Rs was controlled by accumulated surface soil temperature. We found that in the summer monsoon-dominated Tibetan alpine grassland, surface soil freezing, bulk soil freezing, and accumulated surface soil temperature are the day-, season-, and year-scale drivers of the non-growing-season Rs , respectively. Our results suggest that warmer winters can trigger carbon loss from this ecosystem because of higher Q 10 of thawed than frozen soils. |
| [33] | |
| [34] | Most of the world’s terrestrial biome types can be found in China. To systematically investigate species composition and structure of China’s forest communities, we launched a long-term project consisting forest vegetation surveys across China’s mountains in the mid 1990s. Over the study period, we have conducted vegetation surveys for 65 mountains and collected vegetation data from about 1500 forest plots, using consistent sampling protocols. In this paper we first introduce the aims, protocols, and major research themes of the project, and then describe the major characteristics of forest communities and their geographic patterns and climatic controls. As latitude increased, diameter at breast height (DBH) and height of trees increased, while individual density of trees and woody species richness decreased. Total basal area (TBA) of trees and species richness of herbs did not vary with latitude. Contemporary climate seems to drive these patterns: temperature was the leading factor for DBH, precipitation was most important for tree height and individual density, actual evapotranspiration (a surrogate of productivity) determined woody (trees and shrubs) species richness, and rainfall was the major controller of the herb species richness. The species–abundance relationship showed that species dominance (measured by the number of individuals per species) declined significantly from boreal forests to evergreen broadleaf forests from north to south. Our results are in line with the idea that productivity drives woody species richness. Similarly, we find that biomass (measured as TBA) is invariant along the environmental gradients. However, individual density varies dramatically, in contrast to the assumptions underlying the metabolic theory of ecology. |
| [35] | The relationship between climate/productivity and historical/regional contingency and their relative influence on geographical patterns of species richness (GPSR) are still unresolved. Based on field data from 1494 plots from forests on 63 mountains across China, we document the GPSR for forest communities. Regression tree and generalized linear models were used to explore the discreteness and gradient of the distribution of tree species richness (-diversity), and to estimate the correlations of climate, historical floristic region, and local habitat with species richness. The collinearity between climatic variables and region were further disentangled; and the spatial autocorrelation in the patterns of -diversity and the residuals of alternative predictive models were compared. Overall, 75% of variation in plot-based -diversity of trees was accounted for by all variables included, and about 66.5%, 64.5% and 27.9% by climate, region, and local habitat respectively. Importantly, the explanatory power of these variables differed in particular for coniferous, deciduous broadleaved and evergreen broadleaved species. Ambient temperature was more important for -diversity of trees than were the other climatic variables across China. Spatial autocorrelation in the pattern of -diversity could be accounted for mainly by spatial variation climate. The concordance between tree -diversity, historical flora, contemporary climate, and Quaternary climate change mode suggests the climate/productivity and historical/regional contingency both contribute to the GPSR in a complimentary manner. Taken together, our results provide unique evidence to link of the effects of contemporary climate and historical climate change on species richness across scales. |
| [36] | <P>Environment and spatial processes are key factors in shaping species composition in a community. These two factors make competing predictions concerning the decay of species composition similarity with environmental divergence and geographic distance. Unfortunately, these can be difficult to test independently because changes in environment are commonly well correlated with geographic distance. However, an opportunity is provided by exploiting marked regional differences in the spatial structure of the environment. In this study, we test the predictions of environment filtering and dispersal in explaining species turnover using > 300 study sites spanning 4000 km, across three major grasslands in China in which the environment is spatially structured to different degrees. We find that species composition similarity decayed with environmental divergence in the same way in all three regions, and even across biogeographic regions between which dispersal barriers are evident; in contrast, the decay of species composition similarity with geographic distance depended largely on the spatial structure of the environment. We conclude that, at the scale of study, environmental filtering rather than spatial processes best explains patterns of species turnover in China's grasslands.</P> |
| [37] | Biodiversity patterns and their underlying mechanisms have long been focal topics of study for ecologists and biogeographers. However, compared with spatial variation in species richness (- and -diversity), β-diversity, or the dissimilarity of species composition between two or more sites has until recently received limited attention. In this study, we explored the large-scale patterns of altitudinal turnover (β-diversity) of plants in montane forests of China, based on systematic inventories of 1153 plots from 46 mountains distributed over 0030 degrees of latitude (21.9–51.7°N) and 004100 m of altitude (160–4250 m). The β-diversity of trees and shrubs declined significantly with increasing latitude. Along the altitudinal gradient, β-diversity of both trees and shrubs showed non-significant trends in most mountains. Differences in climate explained 0030.0% of the variation in tree β-diversity (27.7, 36.5, and 26.2% for the Jaccard's, βj, Sorenson's, βs, and Simpson's dissimilarity, βsim, respectively), with mean annual temperature being most important, and ≤ 10.0% of that in shrub β-diversity (10.0, 8.2, and 7.0% for βj, βs, and βsim, respectively), with annual actual evapotranspiration and annual precipitation as the main predictors. However, climatic controls of β-diversity varied dramatically in different biogeograpical regions. The β-diversity of trees exhibited stronger, whereas that of shrubs showed weaker, climatic patterns in temperate and arid than subtropical regions. These results suggest that mechanisms causing patterns of β-diversity may differ between latitudinal and altitudinal gradients, and among biogeographical regions; as a result, caution should be exercised in drawing close parallels between patterns and causes of β-diversity along latitudinal and altitudinal gradients and among regions. |
| [38] | Abstract Aim Most studies on latitudinal gradients of biodiversity have focused on gradients of species richness. Here we aim to test whether, on top of these strong diversity gradients, processes of community assembly vary along a latitudinal gradient of more than 33°. Location China, latitude 18.67–51.86°65N. Methods We used species abundance distribution (SAD) data collected in 32 forest tree plots, and fitted a non-neutral model of community assembly to these SADs. We then calculated the fitted deviation from neutrality, δ, and looked for correlations between δ and geographical and environmental data. Results The fitted parameter δ was positive in most plots, and was furthermore positively correlated with latitude and negatively with temperature, indicating a less even abundance distribution and a likely increase in the strength of environmental filtering in regions further from the tropics and with decreasing temperatures. These results imply that on top of reducing the species richness, cold temperature may impact community assembly processes by strengthening local environmental filtering. Main conclusions Our results suggest a latitudinal gradient in tree community assembly process in Chinese forests, in which deviations from neutrality increase with latitude, probably because of an increase in environmental harshness. |
| [39] | The increase of biodiversity from poles to equator is one of the most pervasive features of nature. For 2 centuries since von Humboldt, Wallace, and Darwin, biogeographers and ecologists have investigated the environmental and historical factors that determine the latitudinal gradient of species diversity, but the underlying mechanisms remain poorly understood. The recently proposed metabolic theory of ecology (MTE) aims to explain ecological patterns and processes, including geographical patterns of species richness, in terms of the effects of temperature and body size on the metabolism of organisms. Here we use 2 comparable databases of tree distributions in eastern Asia and North America to investigate the roles of environmental temperature and spatial scale in shaping geographical patterns of species diversity. We find that number of species increases exponentially with environmental temperature as predicted by the MTE, and so does the rate of spatial turnover in species composition (slope of the species-area relationship). The magnitude of temperature dependence of species richness increases with spatial scale. Moreover, the relationship between species richness and temperature is much steeper in eastern Asia than in North America: in cold climates at high latitudes there are more tree species in North America, but the reverse is true in warmer climates at lower latitudes. These patterns provide evidence that the kinetics of ecological and evolutionary processes play a major role in the latitudinal pattern of biodiversity. |
| [40] | Aim Our objective was to document the general relationship between plant species richness (SR) and above-ground net primary productivity (ANPP) at different spatial scales and the environmental influence on this relationship.Location Temperate and alpine grasslands of China.Methods We investigated SR and ANPP at 321 field sites (1355 plots) across the widely distributed temperate and alpine grasslands of China. Ordinary least squares (OLS) regressions were used to test SR NPP relationships among site means. Plot-level data of SR and ANPP were analysed with general linear models (GLMs) and the correlation between SR and ANPP was decomposed into covariance components to test the influence of climatic variables, region, vegetation type and remaining variation among sites on SR, ANPP and their relationship.Results We found positive linear relationships between SR and ANPP among sites in both the alpine and temperate grassland regions and in different grassland vegetation types of these biomes. Environmental gradients such as growing-season precipitation affected both SR and ANPP in parallel. However, after removing the among-site environmental variation, residual SR and ANPP were no longer correlated at the pooled within-site level.Main conclusions The positive SR NPP relationship across large-scale environmental gradients among sites was most likely the result of climatic variables influencing SR and ANPP in parallel. Our results suggest that in China's natural grasslands there is no direct relationship between SR and ANPP, presumably because the pool of available species for local community assembly is large, in contrast to experiments where species pools are artificially reduced. |
| [41] | Abstract Previous studies have revealed inconsistent correlations between fungal diversity and plant diversity from local to global scales, and there is a lack of information about the diversity-diversity and productivity-diversity relationships for fungi in alpine regions. Here we investigated the internal relationships between soil fungal diversity, plant diversity and productivity across 60 grassland sites on the Tibetan Plateau, using Illumina sequencing of the internal transcribed spacer 2 (ITS2) region for fungal identification. Fungal alpha and beta diversities were best explained by plant alpha and beta diversities, respectively, when accounting for environmental drivers and geographic distance. The best ordinary least squares (OLS) multiple regression models, partial least squares regression (PLSR) and variation partitioning analysis (VPA) indicated that plant richness was positively correlated with fungal richness. However, no correlation between plant richness and fungal richness was evident for fungal functional guilds when analyzed individually. Plant productivity showed a weaker relationship to fungal diversity which was intercorrelated with other factors such as plant diversity, and was thus excluded as a main driver. Our study points to a predominant effect of plant diversity, along with other factors such as carbon02:02nitrogen (C02:02N) ratio, soil phosphorus and dissolved organic carbon, on soil fungal richness. 08 2017 The Authors. New Phytologist 08 2017 New Phytologist Trust. |
| [42] | react-text: 427 Plant biodiversity is often correlated with ecosystem functioning in terrestrial ecosystems. However, we know little about the relative and combined effects of above- and belowground biodiversity on multiple ecosystem functions (e.g., ecosystem multifunctionality, EMF) or how climate might mediate those relationships. Here, we tease apart the effects of biotic and abiotic factors, both above... /react-text react-text: 428 /react-text [Show full abstract] |
| [43] | Abstract Plant biodiversity is often correlated with ecosystem functioning in terrestrial ecosystems. However, we know little about the relative and combined effects of above- and belowground biodiversity on multiple ecosystem functions (for example, ecosystem multifunctionality, EMF) or how climate might mediate those relationships. Here we tease apart the effects of biotic and abiotic factors, both above- and belowground, on EMF on the Tibetan Plateau, China. We found that a suite of biotic and abiotic variables account for up to 86% of the variation in EMF, with the combined effects of above- and belowground biodiversity accounting for 45% of the variation in EMF. Our results have two important implications: first, including belowground biodiversity in models can improve the ability to explain and predict EMF. Second, regional-scale variation in climate, and perhaps climate change, can determine, or at least modify, the effects of biodiversity on EMF in natural ecosystems. |
| [44] | Neutral models of species diversity predict patterns of abundance for communities in which all individuals are ecologically equivalent. These models were originally developed for Panamanian trees and successfully reproduce observed distributions of abundance. Neutral models also make macroevolutionary predictions that have rarely been evaluated or tested. Here we show that neutral models predict a humped or flat relationship between species age and population size. In contrast, ages and abundances of tree species in the Panamanian Canal watershed are found to be positively correlated, which falsifies the models. Speciation rates vary among phylogenetic lineages and are partially heritable from mother to daughter species. Variable speciation rates in an otherwise neutral model lead to a demographic advantage for species with low speciation rate. This demographic advantage results in a positive correlation between species age and abundance, as found in the Panamanian tropical forest community. |
| [45] | |
| [46] | China is very rich in biodiversity, however, it is also characterized by a long history of civilization. As a result, China has a large number of threatened species. Recently the Chinese government evaluated the living status of plants, and published the China Biodiversity Red List: Higher Plants. However, little is known about how threatened plants are distributed and conserved in China. In this study, we developed a fine resolution distribution database for 3244 threatened plants, explored richness patterns and evaluated the in situ conservation status of the threatened plants by overlapping the species distribution with terrestrial national and provincial nature reserves (NNRs and PNRs) in China. We found the greatest richness of threatened plants in the southwestern region of mainland China (mainly Yunnan, southeastern Xizang and western Sichuan), northwestern Guangxi, northern Guangdong, Hainan Island and the mountainous region of Taiwan, while the lowest richness was found in Qinghai, Hebei, Shandong, Jiangsu and Chongqing Provinces. On average, NNRs covered 18.8%, and NNRs and PNRs together covered 27.5%, of threatened plant distribution areas. However, 827 threatened plants (including 627 species endemic to China) were not covered by NNRs and 397 threatened plants (including 293 endemic to China) were not covered by either NNRs or PNRs. We proposed that nature reserves specifically designed for threatened plants need to be established in South China, especially in the Yunnan, Guizhou, Guangxi, Xinjiang Hainan, and Zhejiang Provinces. |
| [47] | Orchidaceae, the orchid family, is one of the species richest families and the most endangered plant groups. Most orchids are narrowly distributed in specific habitats because of their mycorrhizal specificity, pollinator specialization and limited seed germination rate; compared to plants from other families, orchids are extremely susceptible to habitat disturbance. However, little is known about how orchids are distributed and how they are protected at large scales. In this study, we developed a distribution database for all the 1449 orchid species in China. Using this database, we explored patterns of orchid richness in relation to climate, net primary productivity and habitat heterogeneity in China. We then evaluated the in situ conservation status of the orchids in China by overlapping the species distribution and the terrestrial national and provincial nature reserves (NNRs and PNRs) in China. We found that 90% of orchid species in China were distributed in 258,800 km 2 (2.7% of China landmass). Net primary productivity, elevation range, and temperature seasonality together explained 34.4% of variance in orchid richness. On average, NNRs covered 12.1%, NNRs and PNRs together covered 29.1%, of orchid distribution areas. However, there were still 154 (including 83 endemic to China) narrowly distributed orchid species not covered by NNRs; and 48 (including 28 endemic to China) were not covered by either NNRs or PNRs. We proposed that nature reserves specifically designed for orchids need to be established in Southwest China and Hainan Island. |
| [48] | Recent climate change has been widely recognized to influence the distribution of many plants and animals, while its impacts on the distribution of fungi remain largely unknown. Here, we used Ophiocordyceps sinensis , an entomopathogenic fungus and important traditional Chinese medicine whose distribution range was reported as decreased on the Tibetan Plateau in recent decades, as an example to predict the current potential distribution and the possible range shifts in response to climate change of a fungus by using extensive field records and an ensemble species distribution modeling method. It is demonstrated that the distribution range of the fungus wound decrease significantly, shifting upward in altitude and toward the central part of the Plateau. In an unlimited dispersal scenario, net habitat losses of 19% for both years 2050 and 2070 under representative concentration pathways (RCP) 2.6 and of 8% and 4% under RCP8.5 for the years 2050 and 2070, respectively, were predicted. If a non-dispersal scenario was considered, 36 39% of the current habitats would be lost in the future. The results presented here will not only provide useful information for the conservation of O. sinensis , but also provide a representative case of evaluating impacts of climate change on fungal distribution using species distribution modeling method. |
| [49] | Abstract Medicinal plants are more vulnerable to threats than non-medicinal plants. In China, a large number of medicinal plants are threatened by human activities and climate change, which greatly affect the conservation of species diversity, genetic resources and sustainable development of the traditional Chinese medicine industry. In this study, we established the first database for the distributions of 535 threatened medicinal plant species in China at the county level. Using this database, we explored geographic patterns, identified biodiversity hotspots and determined the conservation gaps for these threatened medicinal plants. Threatened medicinal plants were widely distributed in 1709 counties across the whole country. The species richness was higher in southern than in northern China. Using the “top 5% richness algorithm” and the “complementary algorithm”, we identified 213 counties as biodiversity hotspots for threatened medicinal plants in China. However, based on further conservation gap analysis, we found that 30 hotspot counties were not covered by any type of nature reserve (complete conservation gaps), and 27 more hotspot counties were not covered by national or provincial nature reserves in mainland China. We suggest that new nature reserves should be established for the 30 complete conservation gaps, while range, level or management strategies for the current nature reserves should be improved for the remaining 27 conservation gaps to promote the conservation of threatened medicinal plants in China. |
| [50] | Leaf nitrogen and phosphorus stoichiometry of Chinese terrestrial plants was studied based on a national data set including 753 species across the country. Geometric means were calculated for functional groups based on life form, phylogeny and photosynthetic pathway, as well as for all 753 species. The relationships between leaf N and P stoichiometric traits and latitude (and temperature) were analysed. The geometric means of leaf N, P, and N : P ratio for the 753 species were 18.6 and 1.21 mg g(-1) and 14.4, respectively. With increasing latitude (decreasing mean annual temperature, MAT), leaf N and P increased, but the N : P ratio did not show significant changes. Although patterns of leaf N, P and N : P ratios across the functional groups were generally consistent with those reported previously, the overall N : P ratio of China's flora was considerably higher than the global averages, probably caused by a greater shortage of soil P in China than elsewhere. The relationships between leaf N, P and N : P ratio and latitude (and MAT) also suggested the existence of broad biogeographical patterns of these leaf traits in Chinese flora. |
| [51] | Abstract Combined effects of cumulative nutrient inputs and biogeochemical processes that occur in freshwater under anthropogenic eutrophication could lead to myriad shifts in nitrogen (N):phosphorus (P) stoichiometry in global freshwater ecosystems, but this is not yet well-assessed. Here we evaluated the characteristics of N and P stoichiometries in bodies of freshwater and their herbaceous macrophytes across human-impact levels, regions and periods. Freshwater and its macrophytes had higher N and P concentrations and lower N02:02P ratios in heavily than lightly human-impacted environments, further evidenced by spatiotemporal comparisons across eutrophication gradients. N and P concentrations in freshwater ecosystems were positively correlated and N02:02P was negatively correlated with population density in China. These results indicate a faster accumulation of P than N in human-impacted freshwater ecosystems, which could have large effects on the trophic webs and biogeochemical cycles of estuaries and coastal areas by freshwater loadings, and reinforce the importance of rehabilitating these ecosystems. |
| [52] | Abstract Allocation of limiting resources, such as nutrients, is an important adaptation strategy for plants. Plants may allocate different nutrients within a specific organ or the same nutrient among different organs. In this study, we investigated the allocation strategies of nitrogen (N) and phosphorus (P) in leaves, stems and roots of 126 shrub species from 172 shrubland communities in Northern China using scaling analyses. Results showed that N and P have different scaling relationships among plant organs. The scaling relationships of N concentration across different plant organs tended to be allometric between leaves and non-leaf organs, and isometric between non-leaf organs. Whilst the scaling relationships of P concentration tended to be allometric between roots and non-root organs, and isometric between non-root organs. In arid environments, plant tend to have higher nutrient concentration in leaves at given root or stem nutrient concentration. Evolutionary history affected the scaling relationships of N concentration slightly, but not affected those of P concentration. Despite fairly consistent nutrients allocation strategies existed in independently evolving lineages, evolutionary history and environments still led to variations on these strategies. |
| [53] | Concentrations of leaf nitrogen (N) and phosphorus (P) are key leaf traits in ecosystem functioning and dynamics. Foliar stoichiometry varies remarkably among life forms. However, previous studies have focused on trees and grasses, leaving the knowledge gap for the stoichiometric patterns of shrubs. In this study, we explored the intra- and interspecific variations of leaf N and P concentration in relation to climate, soil property and evolutionary history based on 1486 samples composed of 163 shrub species from 361 shrubland sites in northern China expanding 46.1 (86.7-132.8 E) in longitude and 19.8 (32.6-52.4 N) in latitude. The results showed that leaf N concentration decreased with precipitation, leaf P concentration decreased with temperature and increased with precipitation and soil P concentration. Both leaf N and P concentrations were phylogenetically conserved, but leaf P concentration was less conserved than leaf N concentration. At community level, climates explained more interspecific, while soil nutrient explained more intraspecific, variation of leaf nutrient concentrations. These results suggested that leaf N and P concentrations responded to climate, soil, and phylogeny in different ways. Climate influenced the community chemical traits through the shift in species composition, whereas soil directly influenced the community chemical traits. |
| [54] | Legumes are characterized as keeping stable nutrient supply under nutrient-limited conditions. However, few studies examined the legumes' stoichiometric advantages over other plants across various taxa in natural ecosystems. We explored differences in nitrogen (N) and phosphorus (P) stoichiometry of different tissue types (leaf, stem, and root) between N2-fixing legume shrubs and non-N2-fixing shrubs from 299 broadleaved deciduous shrubland sites in northern China. After excluding effects of taxonomy and environmental variables, these two functional groups differed considerably in nutrient regulation. N concentrations and N:P ratios were higher in legume shrubs than in non-N2-fixing shrubs. N concentrations were positively correlated between the plants and soil for non-N2-fixing shrubs, but not for legume shrubs, indicating a stronger stoichiometric homeostasis in legume shrubs than in non-N2-fixing shrubs. N concentrations were positively correlated among three tissue types for non-N2-fixing shrubs, but not between leaves and non-leaf tissues for legume shrubs, demonstrating that N concentrations were more dependent among tissues for non-N2-fixing shrubs than for legume shrubs. N and P concentrations were correlated within all tissues for both functional groups, but the regression slopes were flatter for legume shrubs than non-N2-fixing shrubs, implying that legume shrubs were more P limited than non-N2-fixing shrubs. These results address significant differences in stoichiometry between legume shrubs and non-N2-fixing shrubs, and indicate the influence of symbiotic nitrogen fixation (SNF) on plant stoichiometry. Overall, N2-fixing legume shrubs are higher and more stoichiometrically homeostatic in N concentrations. However, due to excess uptake of N, legumes may suffer from potential P limitation. With their N advantage, legume shrubs could be good nurse plants in restoration sites with degraded soil, but their P supply should be taken care of during management according to our results. |
| [55] | |
| [56] | |
| [57] | |
| [58] | . |
| [59] | 位于北疆准噶尔盆地中部的古尔班通古特沙漠，其植物区系和植被居于亚洲中部荒漠和哈萨克斯坦荒漠之间的过渡，但本身具有自己的特点。沙地植被主要由9个群落和3个群聚组成。由于各部分的自然条件、区系和群落性质的差别，沙漠本身在植被上又分异成三个不同的部分：西南区、东南区和北部区。在亚洲荒漠的详细划分方案中，包括古尔班通古特沙漠在内的准噶尔盆地荒漠可以作为独立的植物地理区划分出来。 . 位于北疆准噶尔盆地中部的古尔班通古特沙漠，其植物区系和植被居于亚洲中部荒漠和哈萨克斯坦荒漠之间的过渡，但本身具有自己的特点。沙地植被主要由9个群落和3个群聚组成。由于各部分的自然条件、区系和群落性质的差别，沙漠本身在植被上又分异成三个不同的部分：西南区、东南区和北部区。在亚洲荒漠的详细划分方案中，包括古尔班通古特沙漠在内的准噶尔盆地荒漠可以作为独立的植物地理区划分出来。 |
| [60] | |
| [61] | The woodland-steppe ecotone of the southeastern Inner Mongolian Plateau in northern China is located at the northwestern limit of the Pacific monsoon influence, where the landscape may have been a sensitive recorder of past climatic changes. Physical, chemical, and biological analyses of AMS 14C-dated sediment sequences from two lakes of this region were used to reconstruct the Holocene vegetation and desertification history and distinguish four periods: (1) a cold and humid period from 10000 to 8000 14C yr B.P., (2) a warm and humid period from 8000 to 5900 14C yr B.P., (3) a warm and dry period from 5900 to 2900 14C yr B.P., and (4) a cool and dry period from 2900 14C yr B.P. to the present. The increased aridity during the middle Holocene was likely caused by increased winter temperatures and enhanced winter evaporation. The transition from a humid to an arid climate after 5900 14C yr B.P. coincided with enhanced aeolian activity, and deciduous woodlands were replaced by pine woodlands and then by steppes in response to the climatic deterioration. These transitions led to the present desertification. The records suggest that a simple association of thermal and moisture conditions, such as warm/wet or cold/dry, may be misleading. |
| [62] | The semi-arid forest-steppe ecotone in China is characterized by a patchy pattern of forest and steppe, with forest patches restricted to shady slopes. To address the effect of topography on forest distribution through regulation of available water, we calculated evaporation as a function of slope aspect and inclination. Field vegetation records from randomly selected sites with minimum slope inclination were used to test the simulated forest distribution. Seasonal and diurnal changes of surface soil temperature and moisture of shady and sunny slopes were recorded. Soil water content was measured during two growing seasons on both sunny and shady slopes with the same forest type at three sites located along the mean annual precipitation (MAP) gradient. Evaporation decreases with slope inclination on shady slopes, but increases with inclination on sunny slopes. The shady slope received 35% of the annual direct solar radiation received by the sunny slope when the slope inclination was 25, and the contrast in annual direct solar radiation between the shady and sunny slopes further widens as slope inclination increases. Steeper shady slopes can support forests in dryer climates, with log-linear regression revealing a minimum slope inclination for forest distribution along the MAP gradient. The simulated minimum slope inclination for forest growth was larger than the observed minimum inclination, and the difference was greater in wetter conditions. A larger forest area fraction was considered to lead to a reduction in soil temperature and evaporation, as verified by soil temperature and moisture records and soil water content measurements. The slope-specific forest distribution in the semi-arid region of China can be explained by a topography-controlled soil water supply. Lower evaporation, resulting from lower direct solar radiation on shady slopes, allows shady slopes to retain a water supply sufficient for sustaining forests, and the existence of forests on shady slopes further reduces evaporation. Different tree species coexist at the xeric timberline due to regulation by slope inclination and aspect. |
| [63] | Biomass and species richness are two important indicators of ecosystem stability. The relationship between biomass and species richness along precipitation gradient in semi-arid regions is significant for prediction of ecosystem stability under the estimated climatic drying in the future. In this study, we investigated species richness, aboveground biomass and cover of temperate steppe along a mean annual precipitation (MAP) gradient in central Inner Mongolian of China. We also measured water use efficiency (WUE) of selected species and overall communities. Our results showed that biomass almost remained unchanged in the moist half of the gradient, but species richness decreased markedly with decreasing MAP. Species richness further showed a negligible decrease, whereas a much sharper drop was detected in biomass towards the arid end with decreasing MAP. Vegetation cover shared a similar pattern with biomass and dropped sharply towards the arid end, which may create a strong light and low competition environment favoring C 4 plants. The increment of C 4 species richness could prevent a more intensive decline of species richness under severe arid conditions by raising overall community water use efficiency. Thus, plant communities experiencing water deficiency could also maintain species richness with the occurrence of C 4 plants. |
| [64] | |
| [65] | <正> 关于华北山地垂直带谱的最高一带的归属说法不一,有些作者把太白山、五台山顶的植被划归高山带,而多数作者则把它们称为亚高山灌丛草甸或亚高山草甸,我们认为,华北山地的最高部分应属于高山带。 . <正> 关于华北山地垂直带谱的最高一带的归属说法不一,有些作者把太白山、五台山顶的植被划归高山带,而多数作者则把它们称为亚高山灌丛草甸或亚高山草甸,我们认为,华北山地的最高部分应属于高山带。 |
| [66] | |
| [67] | Unbiased assessment of forest dynamics, including both tree radial growth and forest regeneration, for marginal forests is an urgent task in the context of widely reported forest decline and die-off caused by recent climate change. Based on a network of stand-total tree ring samplings and forest inventory data from eight stands, we reconstructed tree growth and forest recruitment dynamics during the past decades and investigated the linkages of forest dynamics to climate variations in the western and central Altai Mountains in the Inner Asian drylands. Our results revealed a strong coupling between tree growth, forest recruitment and climate variations. A favorable climate generally increases tree growth and triggers growth release and forest recruitments in these semi-arid forests. Differences in local environmental conditions, disturbance regimes and forest histories could possibly modify the forest recruitment dynamics among these forests. Tree radial growth and forest recruitments in both low and high altitudinal Altai Mountain show divergent responses to climate, especially to the spring temperature. A warmer spring will benefit forest recruitment but tends to limit larch radial growth at lower altitudinal mountains. Our study could provide insights into accurate predictions of forest dynamics in this huge mountainous region with complicated climate patterns. |
| [68] | Forest growth is sensitive to interannual climatic change in the alpine treeline ecotone (ATE). Whether the alpine treeline ecotone shares a similar pattern of forest growth with lower elevational closed forest belt (CFB) under changing climate remains unclear. Here, we reported an unprecedented acceleration of Picea schrenkiana forest growth since 1960s in the ATE of Tianshan Mountains, northwestern China by a stand-total sampling along six altitudinal transects with three plots in each transect: one from the ATE between the treeline and the forest line, and the other two from the CFB. All the sampled P. schrenkiana forest patches show a higher growth speed after 1960 and, comparatively, forest growth in the CFB has sped up much slower than that in the ATE. The speedup of forest growth at the ATE is mainly accounted for by climate factors, with increasing temperature suggested to be the primary driver. Stronger water deficit as well as more competition within the CFB might have restricted forest growth there more than that within the ATE, implying biotic factors were also significant for the accelerated forest growth in the ATE, which should be excluded from simulations and predictions of warming-induced treeline dynamics. |
| [69] | Alpine timberline is particularly sensitive to global climate change, with the danger of losing essential ecosystem services in high elevational regions. Its evolution is generally linked to annual average thermal regimes, and is regarded as an indicator of climate warming. However, the effect of uneven seasonal climate change stressed by the Hijioka et al. (2014) on alpine timberline dynamics in terms of both position migration and species composition remains unclear. Here, we documented approximately 6000 years of postglacial alpine timberline evolution on Mt. Tabai in the monsoon-dominated East Asian subtropical-temperate transition. We analyzed three high-resolution lacustrine sediment sequences located below, within, and above the current alpine timberline, an ecotone between the forest line and treeline, respectively. The timberline position appears to have varied coincidently with the temperature effect of cold East Asian Winter Monsoon (EAWM), implying that enhanced EAWM shortened the duration of the growing season and reduced forest survival at the alpine timberline. Unlike position migration, however, timberline species composition depends on summer precipitation. We found that drought-tolerant herb and shrub species were much more sensitive to variations in the water-bearing East Asian Summer Monsoon (EASM) than mesophytic trees at the alpine timberline. Our results suggest that prediction of future timberline dynamics should consider uneven seasonal climate changes. |
| [70] | . We summarized structure and composition of dry forests from a 90-year-old timber inventory collected by the Bureau of Indian Affairs on the former Klamath Indian Reservation (now part of the Fremont-Winema National Forest). This analysis includes data from 424,626 conifers >= 15 cm dbh on 3068 transects covering 6646 ha. The data represent a 10-20% sample of 38,651 ha of forest growing on sites that are classified as ponderosa pine (Pinus ponderosa) and mixed-conifer habitat types distributed within the 117,672 ha of the study area. Large, drought- and fire-tolerant ponderosa pine dominated these forests. Large tree (>53 cm dbh) basal area (13 +/- 7 m(2)/ha) contributed 83 16% of total basal area; 81 +/- 20% of the large-tree basal area was ponderosa pine. Composition and structure of forests on mixed-conifer sites were very similar to those on ponderosa pine sites. Variability in composition and structure was recorded on all habitat types and was highest on moist mixed-conifer sites. Stand densities (trees per hectare, tph) have more than tripled over the past 90 years from 68 +/- 28 tph to a current density of 234 +/- 122 tph recorded in Current Vegetation Survey data collected by the United States Forest Service. Mean basal area, however, increased by less than 20%. Basal area of large trees (>53 cm dbh) has declined by >50%, and the abundance of large trees as a proportion of the total number of trees per hectare has decreased by more than a factor of five. This landscape-level record of historical forest conditions allows inferences about structure and composition across tens of thousands of hectares. A historical landscape emerges which supports current working hypotheses that frequent, low- to moderate-severity wildfires maintained a predominantly low-density forest dominated by large, fire- and drought-tolerant ponderosa pines across a significant moisture and productivity gradient from the driest ponderosa pine to the mixed-conifer habitat types. (C) 2013 Elsevier B.V. All rights reserved. |
| [71] | Forests around the world are subject to risk of high rates of tree growth decline and increased tree mortality from combinations of climate warming and drought, notably in semi-arid settings. Here, we assess how climate warming has affected tree growth in one of the world's most extensive zones of semi-arid forests, in Inner Asia, a region where lack of data limits our understanding of how climate change may impact forests. We show that pervasive tree growth declines since 1994 in Inner Asia have been confined to semi-arid forests, where growing season water stress has been rising due to warming-induced increases in atmospheric moisture demand. A causal link between increasing drought and declining growth at semi-arid sites is corroborated by correlation analyses comparing annual climate data to records of tree-ring widths. These ring-width records tend to be substantially more sensitive to drought variability at semi-arid sites than at semi-humid sites. Fire occurrence and insect/pathogen attacks have increased in tandem with the most recent (2007-2009) documented episode of tree mortality. If warming in Inner Asia continues, further increases in forest stress and tree mortality could be expected, potentially driving the eventual regional loss of current semi-arid forests. |
| [72] | Based on a sediment core from Lake Hulun Nuur in the semi-arid forest-steppe ecotone in North China, we reconstructed the history of climate change, vegetation development, and fire frequency in this region during the mid- to late Holocene. Four stages were identified: (1) 630009“490009‰cal. yr BP, a warm-humid phase dominated by forest vegetation with moderate fire incidence and a gradual drying trend; (2) 490009“425009‰cal. yr BP, a warm-dry phase dominated by forest vegetation with increased aridity and high fire occurrence; (3) 425009“175009‰cal. yr BP, a gradual drying phase with forest decline and low fire occurrence; and (4) 175009‰cal. yr BP09“present, a cool-dry phase dominated by steppe with some decrease in aridity. Building on previous studies in this region, the successive timing of forest replacement by steppe along the precipitation gradient in the late Holocene indicates a gradual retreat of the forest margin under climate drying. Vegetation succession was predominantly determined by climate, but forests showed strong resilience to mid-Holocene drought events. Fire was suggested as a triggering disturbance that acted to reduce the resilience of forests to drought and prevent rapid forest recovery under subsequent climatic amelioration. No simple anti-correlation between fire and Pacific monsoon intensity suggested by previous studies was found here, highlighting vegetation as a critical factor for fire occurrence through the accumulation of fuel in the semi-arid region, where vegetation growth is strongly constrained by precipitation. |
| [73] | 61Pinus and Quercus are precipitation-sensitive while Betula is temperature-sensitive.61Vegetation sensitivity increased following evident reduction in monsoon.61Plant taxa responded individualistically to Holocene monsoon development in China.61Movement was asymmetrical to Holocene monsoon development in China. |
| [74] | |
| [75] | |
| [76] | 中国西南干旱河谷基本分布在横断山区及其南延山系范围之内(张荣祖,1992),涉及怒江、澜沧江、元江、金沙江、南盘江、雅砻江、大渡河、岷江、白龙江(含支流白水江)等的上、中游干流及部分支流的下陷河谷段,多呈南北或西北-东南走向,海拔范围在500-2,500m.这些生境相似的河段在地形上相对封闭,且被高耸的山岭彼此阻隔,相距数十至数百公里,形成了横断山区特有的倒置生境孤岛群.西南干旱河谷生物多样性的研究意义在于它代表了中国热带和亚热带湿润季风气候控制的自然地理背景下具有隐域和残遗性质的半干旱-干旱植被和植物区系(吴征镒和王荷生,1983),这是青藏高原隆起、南亚-东亚季风加强所产生的诸多自然地理变迁结果之一(张新时,1978;郑度和杨勤业,1985),并与全球同纬度以干旱-半干旱气候主导的植被与植物区系背景相呼应(张荣祖,1992;金振洲,2002;吴征镒等,2011). . 中国西南干旱河谷基本分布在横断山区及其南延山系范围之内(张荣祖,1992),涉及怒江、澜沧江、元江、金沙江、南盘江、雅砻江、大渡河、岷江、白龙江(含支流白水江)等的上、中游干流及部分支流的下陷河谷段,多呈南北或西北-东南走向,海拔范围在500-2,500m.这些生境相似的河段在地形上相对封闭,且被高耸的山岭彼此阻隔,相距数十至数百公里,形成了横断山区特有的倒置生境孤岛群.西南干旱河谷生物多样性的研究意义在于它代表了中国热带和亚热带湿润季风气候控制的自然地理背景下具有隐域和残遗性质的半干旱-干旱植被和植物区系(吴征镒和王荷生,1983),这是青藏高原隆起、南亚-东亚季风加强所产生的诸多自然地理变迁结果之一(张新时,1978;郑度和杨勤业,1985),并与全球同纬度以干旱-半干旱气候主导的植被与植物区系背景相呼应(张荣祖,1992;金振洲,2002;吴征镒等,2011). |
| [77] | Abstract Forest canopy height is an important indicator of forest biomass, species diversity, and other ecosystem functions; however, the climatic determinants that underlie its global patterns have not been fully explored. Using satellite LiDAR-derived forest canopy heights and field measurements of the world's giant trees, combined with climate indices, we evaluated the global patterns and determinants of forest canopy height. The mean canopy height was highest in tropical regions, but tall forests (>50 m) occur at various latitudes. Water availability, quantified by the difference between annual precipitation and annual potential evapotranspiration (P61PET), was the best predictor of global forest canopy height, which supports the hydraulic limitation hypothesis. However, in striking contrast with previous studies, the canopy height exhibited a hump-shaped curve along a gradient of P61PET: it initially increased, then peaked at approximately 680 mm of P61PET, and finally declined, which suggests that excessive water supply negatively affects the canopy height. This trend held true across continents and forest types, and it was also validated using forest inventory data from China and the United States. Our findings provide new insights into the climatic controls of the world's giant trees and have important implications for forest management and improvement of forest growth models. This article is protected by copyright. All rights reserved. |
| [78] | 生态学发展到目前已形成一系列的分科,它已不是一门单独的学科,而是一组学科-学科的体系。名称中包含“生态”二字的学科至少在一百个以上,因而,产生了如何对大量生态学科进行分类的问题。 我们认为,如果根据研究对象的性质和尺度(规模)以及相应地需要采用的研究方法的特点,并考虑当前发展的趋势,可以把生态学概括为3类:生物生态学、地生态学和全球生态学。 从当前趋势看,至少下列8个问题是地生态学注意的核心:(1)人工生态系统;(2)生物(主要是植物)指示现象;(3)地生态制图;(4)生态监测;(5)生态预测;(6)生态区划;(7)生态规划与设计;(8)生态影响评价。 . 生态学发展到目前已形成一系列的分科,它已不是一门单独的学科,而是一组学科-学科的体系。名称中包含“生态”二字的学科至少在一百个以上,因而,产生了如何对大量生态学科进行分类的问题。 我们认为,如果根据研究对象的性质和尺度(规模)以及相应地需要采用的研究方法的特点,并考虑当前发展的趋势,可以把生态学概括为3类:生物生态学、地生态学和全球生态学。 从当前趋势看,至少下列8个问题是地生态学注意的核心:(1)人工生态系统;(2)生物(主要是植物)指示现象;(3)地生态制图;(4)生态监测;(5)生态预测;(6)生态区划;(7)生态规划与设计;(8)生态影响评价。 |
| [79] | |
| [80] | 中国的城市化有３个特点：（１）不匀速，城市数目和城市人口长期增长缓慢，近十年来急剧加快；（２）中小城市发展快，而大城市和特大城市增长慢。（３）特大城市和大城市主要集中于东部沿海地区。中国城市化引起的生态问题有：环境污染、供水紧张、地面沉降等。新中国成立以来，虽然政府采取了多种措施。改善城市环境，也收到了一定效果，但目前在从计划经济向市场经济转变的过渡期间，城市化高速发展，城市生态问题仍然十分严重。迫切需要进一步加强城、乡规划，严格环保立法，制止城市生态状况的进一步恶化。 . 中国的城市化有３个特点：（１）不匀速，城市数目和城市人口长期增长缓慢，近十年来急剧加快；（２）中小城市发展快，而大城市和特大城市增长慢。（３）特大城市和大城市主要集中于东部沿海地区。中国城市化引起的生态问题有：环境污染、供水紧张、地面沉降等。新中国成立以来，虽然政府采取了多种措施。改善城市环境，也收到了一定效果，但目前在从计划经济向市场经济转变的过渡期间，城市化高速发展，城市生态问题仍然十分严重。迫切需要进一步加强城、乡规划，严格环保立法，制止城市生态状况的进一步恶化。 |
| [81] | The rapid urbanization taking place in Asia since 1970 has exhibited a process different from that of the developed countries in the West. This process has contributed to the emergence of a new landscape in Asia — widely known as the desakota (a combination of two Indonesian words: “ desa” for village, “ kota” for town) regions described in the McGee–Ginsburg model. These desakota regions are characterized by an intense mix of agricultural and non-agricultural activities that often stretch along corridors between large city cores. Although, the McGee–Ginsburg model captures the socio-demographic dimensions of the rapid urbanization process, little is known about the dynamics of landscape structures in the emerging desakota regions in Asia. By linking remote sensing, landscape characterization indices, and cellular automata modeling with geographic information systems (GIS), this paper develops a GIS-based spatial analysis and modeling approach to study the landscape dynamics of the desakota regions in southeast China. We tested our method using data between 1992 and 1996 for the city of Longhua in the Shenzhen Special Economic Zone — one of the fastest growing areas in southeast China. The results not only confirm the effectiveness of GIS-based spatial analysis and modeling approach in studying the ecological impacts of human activities, but also reveal the salient features of landscape dynamics in the desakota regions. Drawing from the results of this research, we conclude that the pace of urbanization and the size of desakota regions must be controlled in order to create a sustainable future in developing countries. |
| [82] | |
| [83] | Species richness and turnover rates differed between the western and eastern aspects of Baima Snow Mountain: maximum species richness (94 species in a transect of 1000 m2) was recorded at 2800 m on the western aspect and at 3400 m on the eastern aspect (126 species), which also recorded a much higher value of gamma diversity (501 species) than the western aspect (300 species). The turnover rates were the highest in the transition zones between different vegetation types, whereas species-area curves showed larger within-transect beta diversity at middle elevations. The effect of elevation on alpha diversity was due mainly to the differences in seasonal temperature and moisture, and these environmental factors mattered more than spatial distances to the turnover rates along the elevation gradient, although the impact of the environmental factors differed with the growth form (herb, shrubs or trees) of the species. The differences in the patterns of plant biodiversity between the two aspects helped to assess several hypotheses that seek to explain such patterns, to highlight the impacts of contemporary climate and historical and regional factors and to plan biological conservation and forest management in this region more scientifically. |
| [84] | Evergreen broadleaved woody plants (EBWPs) are dominant components in forests and savanna of the global tropic and subtropic regions. Southern China possesses the largest continuous area of subtropical EBWPs distribution, harboring a high proportion of endemic species. Hotspot and gap analyses are effective methods for analyzing the spatial pattern of biodiversity and conservation and were used here for EBWPs in China. Based on a distribution data set of 6,265 EBWPs with a spatial resolution of 5065×655065km, we measured diversity of EBWPs in China using four indices: species richness, corrected weighted endemism, relative phylogenetic diversity, and phylogenetic endemism. According to the results based on 10% threshold, 15.73% of China’s land area was identified as hotspots using at least one diversity index. Only 2.14% of China’s land area was identified as hotspots for EBWPs by all four metrics simultaneously. Most of the hotspots locate in southern mountains. Moreover, we found substantial conservation gaps for Chinese EBWPs. Only 25.43% of the hotspots are covered by existing nature reserves by more than 10% of their area. We suggest to promote the establishment and management of nature reserve system within the hotspot gaps. |
| [85] | |
| [86] |
