Spatiotemporal pattern of forest fragmentation in the Loess Plateau
YANGZhiqi1,2,3,, DONGJinwei1,, XUXinliang1, ZHAOGuosong1, CHENWei2, ZHOUYan1,3 1. Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China2. State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China3. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China 通讯作者:通讯作者:董金玮,E-mail: dongjw@igsnrr.ac.cn 收稿日期:2017-09-19 修回日期:2017-12-18 网络出版日期:2018-06-25 版权声明:2018《资源科学》编辑部《资源科学》编辑部 基金资助:中国科学院战略性先导科技专项(A类)资助(XDA19040301)遥感科学国家重点实验室开放基金(OFSLRSS201606) 作者简介: -->作者简介: 杨智奇,男,山东济宁人,硕士生,主要研究方向为土地利用变化与森林制图。E-mail: yangzhiqi@cugb.edu.cn
关键词:森林破碎化;黄土高原;.破碎化模型;退耕还林;时空格局 Abstract As the main type of terrestrial ecosystem, forests play an important role in maintaining biodiversity and regulating regional climates. However, increasingly aggravated deforestation or forest degradation, such as forest fragmentation, have impeded sustainable forest development and threatened biodiversity around the world, especially in the fragile Loess Plateau of China. Hence, the objective of this study was to investigate the spatiotemporal pattern of forest fragmentation in the Loess Plateau from 1980 to 2015 using a landscape fragmentation model and long-term land use datasets in seven periods (1980, 1990, 1995, 2000, 2005, 2008, and 2015) generated by the visual interpretation of Landsat images. We found that the fraction of forest area decreased first and then increased; meanwhile, the forest fragmentation situation aggravated first and then alleviated, corresponding with that of forest proportions. The highly fragmented patch forest category was predominant, while the least fragmented interior forest category was a minority and highly concentrated in its spatial distribution. In addition, the patch forest and interior forest categories decreased from 1980 to 1995, and then increased after 2000. At a regional level, forests in the plain valley areas and earth hill areas with limited soil erosion more easily recovered and showed a rapid recovery of forest fragmentation. At the county level, forest fragmentation differed remarkably in various counties; specifically, forest fragmentation problems in Shaanxi and Inner Mongolia provinces were more severe than in Shanxi province. On the whole, before the implementation of the “Grain for Green” Project, the areas of forests tended to decline and forest fragmentation was aggravated, severely damaging the regional environment. After the implementation of the “Grain for Green” Project, areas of forests increased rapidly and forest fragmentation was alleviated.
Keywords:forest fragmentation;Loess Plateau;fragmentation model;the “Grain for Green” Project;;spatiotemporal pattern -->0 PDF (18742KB)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--> 杨智奇, 董金玮, 徐新良, 赵国松, 陈炜, 周岩. 黄土高原森林破碎化的基本特征与时空格局演变[J]. 资源科学, 2018, 40(6): 1246-1255 https://doi.org/10.18402/resci.2018.06.14 YANGZhiqi, DONGJinwei, XUXinliang, ZHAOGuosong, CHENWei, ZHOUYan. Spatiotemporal pattern of forest fragmentation in the Loess Plateau[J]. RESOURCES SCIENCE, 2018, 40(6): 1246-1255 https://doi.org/10.18402/resci.2018.06.14
黄土高原位于100°52′E—114°33′E,33°41′N—41°16′N,是世界上水土流失最严重和生态环境最脆弱的地区之一,总面积62.14万km2,主要包括了日月山以东、太行山以西、长城以南、秦岭以北的广大地区;地势西北高,东南低,自西北向东南呈波状下降,平均海拔在1500~2000m之间(图1)。黄土高原属于平原向高原过渡地带,气候类型复杂,具有典型的大陆季风气候特征,自南而北横跨暖温带和中温带两个热量带,自东向西横贯半湿润、半干旱两个干湿区;降水多集中在7—9月,大部分地区年降水量在400mm左右,年蒸发量为1400~2000mm[19]。由于受到气温、降水和海拔的影响,黄土高原的植被呈现明显的水平和垂直地带性分布差异。水平地带性体现在由东南向西北黄土高原植被呈现暖温带夏绿阔叶林、森林草原及中温带荒漠草原的阶梯变化;垂直地带性体现在高原东部和南部的山地植被呈现明显的差异,特别是黄土高原吕梁山区从上到下依次出现亚高山灌丛带、山地落叶松林带、山地针阔混交林带、山地松林带和草原带的分布差异。为了对黄土高原进行综合有效的治理,2011年国务院批准了“黄土高原地区综合治理规划大纲(2010—2030年)”,将黄土高原分为6个综合治理分区(图1a)[20]。 显示原图|下载原图ZIP|生成PPT 图12015年黄土高原综合治理分区及森林分布状况示意 -->Figure 1Integrated management area and spatial distribution of forest in the Loess Plateau in 2015 -->
20世纪80年代以来,黄土高原的森林面积比例呈现“先减后增”的变化特点,森林类型主要以有林地和灌木林为主(图3)。80年代初期和末期的森林面积比例基本保持一致,分别是14.60%、14.67%;90年代中期的森林面积比例是13.52%;从80年代末期到90年代中期,森林面积呈现明显下降的趋势,其中下降最显著的森林类型是有林地的面积;90年代末期的森林面积比例是14.66%,2015年的森林面积比例是15.20%;从20世纪90年代末期到2015年,黄土高原的森林面积比例具有明显上升的趋势,其中增长最显著的森林类型是其他林地的面积,与2000年相比增加了79.87%,有林地和灌木林的面积具有稳定的波动变化。 显示原图|下载原图ZIP|生成PPT 图31980—2015年黄土高原森林面积和比例 -->Figure 3Area and percentage of forest in the Loess Plateau from 1980 to 2015 -->
在9×9的窗口中利用森林破碎化模型生成了20世纪80年代以来7个不同时期的黄土高原森林破碎化分布图(图4)。从空间尺度上来看,黄土高原的森林破碎化呈现“斑块森林为主导,内部森林分布集中”的特点。除内蒙古之外,斑块森林广泛分布在黄土高原的其他各省;内部森林主要集中分布在陕西以及山西的吕梁山和太行山脉;过渡森林、孔洞森林和边缘森林分布则比较零散。随着时间的变化(图5,见第1251页),黄土高原的森林破碎化程度总体呈现“先加剧后减缓”的特征;其中斑块森林占比最高(>54%)(图5a,见第1251页),孔洞森林和内部森林占比较低(<10%)(图5c、图5e,见第1251页),过渡森林和边缘森林所占比例介于两者之间(图5b、图5d,见第1251页)。从20世纪80年代初到90年代中期,斑块森林、过渡森林和孔洞森林的面积和比例不断减少;2000年以来,除了2008—2015年斑块森林和边缘森林的面积略微减少,其余时期5种破碎化类型的面积均有增加,其中斑块森林、过渡森林和边缘森林的快速增长期是2000—2005年,孔洞森林和内部森林的快速增长期是2008—2015年。总的来说,虽然黄土高原的内部森林占比较低,破碎化程度比较严重,但是自2000年实施退耕还林以来,斑块森林和内部森林一直处在增加的趋势,破碎化程度逐渐减缓。 显示原图|下载原图ZIP|生成PPT 图41980—2015年黄土高原森林破碎化分布示意 -->Figure 4Spatiotemporal distribution of forest fragmentation in the Loess Plateau from 1980 to 2015 -->
显示原图|下载原图ZIP|生成PPT 图51980—2015年黄土高原森林破碎化类型面积和比例 -->Figure 5The area and proportion of forest fragmentation types in the Loess Plateau from 1980 to 2015 -->
3.2 六大综合治理区森林面积变化及破碎化分析
从区域尺度看(图6,见第1251页),1980—1995年黄土高原沟壑区斑块、过渡和孔洞森林的面积减少,边缘和内部森林的面积增加;黄土丘陵沟壑区除边缘森林外,其他破碎化类型的面积均减少;土石山区所有森林破碎化类型的面积明显下降;河谷平原区的斑块、过渡和边缘森林的面积增加,而孔洞和内部森林的面积减少;农灌区除孔洞森林外,其他破碎化类型的面积增加;沙地和沙漠区所有森林破碎化类型的面积减少。 显示原图|下载原图ZIP|生成PPT 图61980—2015年黄土高原6个分区森林破碎化类型的面积 -->Figure 6The area of forest fragmentation types in the six regions of Loess Plateau from 1980 to 2015 -->
评价县级尺度上的森林破碎化对各县级和区域的森林资源管理具有重要意义[28],因此,本文在县级尺度上进一步分析了黄土高原的森林破碎化。首先,为便于数据的深入分析,过渡森林、孔洞森林、边缘森林或内部森林比例为零的县未进行比较;其次,由于各类型数据比较分散,各县森林破碎化程度有较大差异,难以确定破碎化程度最低的县;最后,筛选出了2015年斑块森林和内部森林比例最高的5个县以及退耕还林典型的5个县进行分析(表1,见第1252页)。 Table 1 表1 表11980—2015年黄土高原县级森林破碎化类型百分比 Table 1Percentage of forest fragmentations types at county scale in Loess Plateau from 1980 to 2015
本研究虽然揭示了黄土高原1980—2015年森林面积和破碎化程度的变化趋势,但是基于遥感数据的破碎化分析会受到研究数据的影响,具有一定的不确定性[34]。首先,Landsat数据观测频率较低,容易受到云和阴影的影响,从而降低了数据质量[35, 36];其次,采用人机交互目视解译的方法容易受到解译人员的主观影响,年际间缺乏良好的稳定性和可比较性[37];最后,除1995年的土地利用分类图之外,其余时期的土地利用分类图都采用直接解译动态斑块的方法提取土地利用动态信息,这种方法在整个建立过程中不可避免地会损失一些信息,产生不确定性[38]。 在未来的森林破碎化研究中,可以从数据质量和尺度效应分析等方面减少上述的不确定性。首先,数据质量的提升可以通过采用新的高质量遥感数据来实现。例如PALSAR数据作为一种新型的雷达数据源,其L波段可以穿透森林冠层获取森林的结构信息而且数据质量不受天气状况的影响。融合Landsat的光谱信息和雷达数据的结构信息可以有效地识别森林,提高分类精度[37],减少由数据质量带来的不确定性。其次,在尺度效应方面,基于不同窗口大小的森林破碎化尺度效应也是优化森林破碎化评估应该考虑的问题。一些研究证明利用小窗口的森林破碎化模型将有助于减少不确定性,增加结果的精度[11],具体的影响评价还有待于进一步探讨。 The authors have declared that no competing interests exist.
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