Carbon storage and spatial distribution characteristics in the Bailongjiang Watershed in Gansu based on InVEST model
ZHANGYing1,, XIEYuchu1,2, QIShanshan1, GONGJie1,, ZHANGLingling1 1. Key Laboratory of Western China’s Environmental Systems (Ministry of Education),College of Earth and Environmental Sciences,Lanzhou University,Lanzhou 730000,China2. Key Laboratory of Environment Change and Resources Use in Beibu Gulf (Ministry of Education),Guangxi Teachers Education University,Nanning 530001,China 通讯作者:通讯作者:巩杰,E-mail:jgong@lzu.edu.cn 收稿日期:2016-01-27 修回日期:2016-05-20 网络出版日期:-- 版权声明:2016《资源科学》编辑部《资源科学》编辑部 基金资助:国家自然科学基金项目(41271199)甘肃省民生科技计划项目(1503FCME006) 作者简介: -->作者简介:张影,女,黑龙江绥化人,硕士生,主要从事土地利用变化与景观生态研究。E-mail:zhy14@lzu.edu.cn
关键词:碳储量;空间格局;InVEST模型;生态系统服务;甘肃白龙江流域 Abstract Research into the spatial distribution characteristics of carbon storage plays an important role in ecosystem carbon pools and management. Based on the carbon module of InVEST and GIS,the Bailongjiang watershed in Gansu,China was selected as a case study to estimate carbon storage and analyze the impact of vegetation types,elevation,slope and slope direction for the spatial distribution of carbon storage. The total carbon storage of the watershed was 251.57 TgC,and the average carbon density was 136.46 MgC/hm2. Among them,the soil carbon storage accounted for 202.20 TgC while vegetation carbon storage was 49.37 TgC,soil carbon storage was the main part of the total carbon storage in the Bailongjiang watershed. The spatial distribution of carbon storage was concentrated in the northwestern mountain forest region (e.g. Diebu Count)and the southern area of Baishuijiang (e.g. Baishuijiang National Nature Reserve). Spruce and fir and evergreen coniferous forest occupied the largest vegetation carbon in the watershed;the value in the eastern and southeastern part of the study area was lower,such as in Wudu District and the northeast part of Tanchang,and the carbon storage in alpine sparse vegetation area was the lowest. Carbon storage had apparently spatial differentiation with the zonality of elevation,slope and slope direction in the Bailongjiang watershed. The watershed carbon storage increased with increasing elevation,then decreased with increasing elevation. Most of the watershed carbon storage was distributed between 1500m to 3500m and 25° to 40°. Carbon storage was higher in the areas belonging to shady slope and semi-shady slope than that of semi-sunny slope and sunny slope. These results can be used for the governance of ecosystem carbon pools and human activities at the watershed scale.
Keywords:carbon storage;spatial distribution;InVEST model;ecosystem service;Bailongjiang Watershed;Gansu -->0 PDF (1012KB)元数据多维度评价相关文章收藏文章 本文引用格式导出EndNoteRisBibtex收藏本文--> 张影, 谢余初, 齐姗姗, 巩杰, 张玲玲. 基于InVEST模型的甘肃白龙江流域生态系统碳储量及空间格局特征[J]. , 2016, 38(8): 1585-1593 https://doi.org/10.18402/resci.2016.08.16 ZHANGYing, XIEYuchu, QIShanshan, GONGJie, ZHANGLingling. Carbon storage and spatial distribution characteristics in the Bailongjiang Watershed in Gansu based on InVEST model[J]. 资源科学, 2016, 38(8): 1585-1593 https://doi.org/10.18402/resci.2016.08.16
1 引言
全球气候变化是国际科学组织和各国政府高度关注的全球性重大环境问题之一[1,2]。陆地生态系统(如森林、草地、灌丛和湿地等)通过释放和吸收大气中的CO2和N2O等温室气体来调节区域气候,提高陆地生态系统的覆盖面积是减缓全球气候变化的主要方式之一[3,4]。近年来,国内外****针对陆地生态系统(尤其是森林生态系统)的碳储量和碳汇功能进行了大量研究。如Dorji等估算了喜马拉雅山脉东部的不丹山区不同土地利用和土地覆盖类型的土壤有机碳密度和储量,模拟了土壤有机碳密度和储量的空间分布,建立了区域土壤碳储量基线数据[5]。方精云等构建了中国森林蓄积量与生物量之间的转换因子连续函数,并估算了中国森林生态系统碳储量状况[6]。Wei等基于木材蓄积量转换森林生物量估算了中国东北天然保护林的森林碳储量[7]。高阳等根据森林资源清查资料及野外调查等估算了宁夏森林生态系统固碳现状等[8]。随着一系列林业生态建设工程的实施,森林面积和林木蓄积量持续增加,有必要重新核算各地区的碳储量来科学反映生态系统的固碳现状[9]。总的来说,这些研究多侧重于某一类生态系统(如森林生态系统)碳储量的估算,且多以行政单元为研究区来反映碳储量的数量变化状况[9-12],而对流域尺度的碳储量空间分异的报道较少,涉及地质灾害频发的山区流域——甘肃白龙江区域的相关报道更为鲜见。王渊刚等探讨了近50年玛纳斯河流域土地利用/覆被变化对碳储量的影响[13]。许文强等研究了干旱区三工河流域土壤碳储量及空间分布特征,为流域土壤碳循环研究提供了数据支撑等[14]。流域是一个完整的地理生态单元,既是区域生态、经济和社会发展等复杂问题研究的热点区域,也是地球系统科学的主要研究对象,从流域的角度来讨论环境问题并实现社会的可持续发展是一条更有效地应用系统综合的途径[15]。 InVEST(Integrated Valuation of Ecosystem Ser-vice and Tradeoffs)模型是由斯坦福大学、大自然保护协会、世界自然基金会等机构共同研发,旨在权衡发展和自然保护之间的关系,可用于量化多种生态系统服务功能(如生物多样性、碳储量、产水量、土壤保持和水体净化等)的综合评估模型[16-18],它能直接反映不同政策和规划对经济和环境等方面的影响[19]。本文以甘肃白龙江流域为例,基于森林资源清查资料、实测数据和前人研究成果等,结合GIS和InVEST的碳储量模块,开展流域碳储量制图及其空间特征分析,研究结果可为流域生态系统管理及减排增汇政策制定等提供科学依据。
2 研究区概况、研究方法与数据来源
2.1 研究区概况
甘肃白龙江流域(32°36′N-34°24′N,103°00′E-105°30′E)是长江二级支流嘉陵江上游重要的水土保持和水源涵养地,也是碳储存功能重要区之一(图1)。流域内地势自西北向东南倾伏,海拔高差大,高山峻岭与峡谷盆地相间分布、沟壑纵横。流域内气候类型复杂多样,夏季高温多雨,冬季温凉少雨,年均气温6~15℃,年均降水量400~850mm。植被覆盖较好,森林广布,流域源头属青藏高原高寒植被区域,中上游属暖温带落叶阔叶林区域,下游属亚热带常绿阔叶林区域[20]。其森林以云杉、桦、柏、杨、栎、油松等为主[21,22]。白龙江流域土壤类型主要包括棕壤、暗棕壤、褐土、高山草甸土、钙质粗骨土、水稻土、黑钙土等[23];其中,上游宽谷盆地以山地棕褐土为主,中游及下中游则以棕色森林土为主,地表多见土石等松散堆积物[24]。流域土层较薄,土壤全氮、全K含量处于中等水平,全磷含量低于全国平均水平,土壤有机质含量空间分异性较大,土壤养分表聚性明显,土壤pH随海拔增加而降低,高海拔区土壤pH呈中性或酸性[25,26]。 显示原图|下载原图ZIP|生成PPT 图1研究区地理位置示意 -->Figure 1The location of the study area -->
甘肃白龙江流域碳储量空间分布如图3所示,流域平均碳密度约为136.46MgC/hm2,碳总储量约为251.57TgC。碳储量主要分布在流域西部和西北部,包括迭部县、舟曲县东南和西南部、文县南部和西北部以及宕昌县东南缘等,文县中部、武都区大部和宕昌东北部碳储量相对较少。具体来说,碳储量的高值区主要集中在山地林区,包括白水江南岸山区、博峪河和拦坝河上中游、迭部至巴藏乡段白龙江两岸山区、宕昌县南部山地林区。低值区主要分布在农业种植区和城镇,以人类活动干扰较强的河谷地带、山前平原和盆中丘陵尤为突出,同时,迭部北部迭山地带高海拔的山区,土地利用类型主要为草地、高寒稀疏植被和积雪覆盖、裸岩等其它用地,也是碳储量的低值区(图3)。 显示原图|下载原图ZIP|生成PPT 图32010年甘肃白龙江流域碳储量空间分布 -->Figure 3Spatial distribution of carbon storage in the Bailongjiang watershed of Gansu in 2010 -->
3.2 流域主要植被和景观类型的碳储量特征
按照不同优势树种分类后统计不同植被和景观的碳总储量发现,乔木林类植被碳储量功能发挥着主体作用(图4),总体表现为:云杉冷杉类>栎类-硬阔>农田>针阔混交林>杨类>阔叶混交林>桦类>山地草地草甸>山地灌丛>油松>亚高山灌丛>高山灌丛>其他松类>高寒草甸>亚高山草甸>柏类>高寒稀疏植被>其它(建设用地、水域、高山积雪极裸岩)(图4)。云杉、冷杉类均为生物碳总储量最大的林地,其碳储量约为81.24TgC,其次是栎类-硬阔类和农田生态系统。柏类和高寒稀疏植被碳储量最少,分别是0.54TgC和0.96TgC。 显示原图|下载原图ZIP|生成PPT 图4甘肃白龙江流域不同植被和景观类型下的碳总储量 -->Figure 4Carbon storage under different vegetation types in the Bailongjiang watershed of Gansu -->
3.3 流域地形因子对碳储量的影响
本文主要从海拔、坡度和坡向3个方面分析地形因子对甘肃白龙江流域碳储量的影响。首先,研究区海拔落差很大(568~4866m),且峰高坡陡、山峦起伏。根据研究区实际情况,将流域海拔划分为8个级别,即≤1000m、1000~1500m、1500~2000m、2000~2500m、2500~3000m、3000~3500m、3500~4000m、>4000m。研究表明,流域碳总储量随海拔高度增加呈先增加后减小的态势;其植被碳储量和土壤碳储量的变化态势与此相似(图5)。具体地,在568~3000m的海拔区段,流域碳储量随海拔高度增加而不断增多,几乎呈线性增长趋势,且在2500~3000m的海拔区段出现最大值,其碳总储量在63.03TgC以上。而在3000m以上的海拔区域,流域内碳储量逐渐减少。从总量分布上看,甘肃白龙江流域碳储量主要集中在1500~3500m的海拔区段内,1000m以下区域和4000m以上的区域分布相对较小。 显示原图|下载原图ZIP|生成PPT 图5甘肃白龙江流域不同高程碳储量分布 -->Figure 5The distribution of carbon storage of different elevation in the Bailongjiang watershed of Gansu -->
利用DEM提取甘肃白龙江流域坡度并进行分级,进而统计流域不同坡度下碳储量分布情况(图6)。结果表明,流域坡度为15°~40°带区的碳储量占甘肃白龙江流域碳总储量的75%以上,<10°的区域碳储量较低,其土壤碳储量和植被的碳储量均较低。 显示原图|下载原图ZIP|生成PPT 图6甘肃白龙江流域不同坡度碳储量分布 -->Figure 6The distribution of carbon storage with different slope -->
由图7可知,白龙江流域内不同坡向上碳储量分布略有差异。阳坡碳总储量约为60.71TgC,阴坡约为64.19 TgC,流域内碳总储量及植被碳储量、土壤碳储量均表现为阴坡>半阴坡>半阳坡>阳坡,但4个坡向的总体碳储量格局差异不大。总体上,坡向对碳储量的影响相对较小。 显示原图|下载原图ZIP|生成PPT 图7甘肃白龙江流域不同坡向碳储量分布 -->Figure 7The distribution of carbon storage with slope direction -->
(1)甘肃白龙江流域生态系统碳储量约为251.57TgC,在空间上呈现一定规律性,高值区主要分布在山地林区,其中以白水江南岸山区、博峪河和拦坝河上中游林区、迭山林区最为突出,低值区多集中于人类活动频繁的农业种植区和城镇。同时,流域内土壤碳储量远大于植被碳储量。从土地利用类型上看,林地的植被碳储量和土壤碳储量最高,其次是草地和耕地,其中,林地中的云、冷杉类常绿针叶林,栎类、硬阔类高山阔叶林和针阔混交林的碳储量相对较大。 (2)甘肃白龙江流域碳储量总体上随海拔增加呈现先上升后下降的趋势,陡坡区域碳储量大于缓坡区域,其高值区分别出现在1500~3500m和25°~40°区段;阴坡和半阴坡的碳储量大于阳坡和半阳坡。 (3)InVEST模型的引入,为碳储量的估算与空间分布提供了可行的方法。本研究在改进和参数本地化的基础上,基于样带实验分析和InVEST模型开展了流域碳储量的定量估算和特征分析,研究结果对于流域生态系统碳库管理和减排增汇政策制定具有重要参考价值。由于研究区没有大型野外观测台站和长期实验观测数据,基础数据匮乏,同时受研究区地形和可达性等限制,以及流域生态系统自身、模型的结构和方法的不确定性等[48,49],故研究结果具有不确定性。建议在以后的研究工作中进一步优化研究方案,评估模型及其参数的适宜性,进行相关参数的本地化处理并验证结果,注重开发适宜中国的本土化评估模型[48],为区域生态系统服务评估服务。 The authors have declared that no competing interests exist.
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