黄土高原植被降水利用效率对植被恢复/退化的响应

基于2000-2014年MODIS NDVI数据及气象数据,运用累计降水利用效率变化差异（CRD,cumulative rain use efficiency differences）估算模型和基于地形要素降水量插值法,探讨2000-2014年黄土高原RUE（降水利用效率rain use efficiency）对植被变化的响应,以期为黄土高原生态可持续发展提供数据支撑。结果表明：黄土高原大部分地区植被覆盖得以改善,其面积约占总面积的81%,区域边缘植被覆盖退化严重。黄土高原降水利用效率RUE与累计NDVI的相关性总体表现为“东南呈正相关,西北为负相关”的空间格局,全区相关系数以正相关为主。黄土高原CRD与植被变化趋势的相关性显著,其中,植被退化背景下,植被退化程度越严重,RUE越低;植被恢复背景下,RUE受“退耕还林还草”作用显著,2000-2005年,RUE呈上升趋势,2007年后,随着退耕还林还草政策的工作重心转移,RUE呈波动变化。     

黄土高原植被覆盖度变化的地形分异及土地利用/覆被变化的影响

基于16 d合成MODIS NDVI数据提取的时间序列植被覆盖度数据,采用一元线性回归趋势分析,对黄土高原2000-2008年植被覆盖度的时空变化及其地形分异、土地利用/覆被变化的影响进行了定量分析。结果表明：（1）研究时段黄土高原植被覆盖度整体呈快速上升趋势,局部下降;（2）黄土高原植被覆盖度变化存在明显的地形分异,陡坡等植被恢复、重建和保育的主要区域植被覆盖度增速显著;（3）土地利用/覆被变化对植被覆盖度的增加影响突出,土地利用/覆被类型变更区植被覆盖度增速显著高于未变化区域,退耕还林还草区增速尤其突出;（4）土地利用/覆被类型未变化区域植被覆盖度总体上也呈增加趋势,但因植被覆盖度水平相对较高,增速明显低于土地利用/覆被类型变化区。上述结果表明,黄土高原植被保育、植被恢复和重建在植被覆盖度提升方面取得了明显成效。     

黄土高原植被覆盖变化对生态系统服务影响及其阈值

黄土高原是退耕还林工程的核心区域,是中国生态恢复成效最显著的区域。明确黄土高原植被恢复对生态系统服务的影响,识别植被影响的阈值效应,是学术研究和管理实践共同的需求。然而,目前相关研究仍存在研究空缺,特别是在区域尺度对生态系统服务随植被变化阈值进行识别的研究较少。本文选择植被覆盖度（FVC）为指标表征2000—2015年黄土高原植被恢复情况,以土壤保持服务、产水服务和碳固定服务为指标表征研究区生态系统服务情况,对二者的时空变化及交互作用进行分析,评估植被覆盖变化对生态系统服务的影响,并对影响的阈值进行定量识别。结果显示：① 2000—2015年黄土高原植被显著恢复;生态系统服务变化差异明显,碳固定服务明显增强,土壤保持服务得到一定改善,产水服务较为稳定。② 植被覆盖变化与生态系统服务变化的相关程度存在差异,植被覆盖与碳固定服务的关联性最强,其次为土壤保持服务。③ 植被覆盖增加能够促进区域生态系统服务总体提升,但促进作用存在阈值效应。植被覆盖影响的阈值在林地区、林地—草地区、草地区和草地—沙漠区分别为44%、32%、34%和34%,超过上述阈值,植被覆盖增加的促进作用趋于减弱。     

Responses of Ecosystems to Ecological Compensation in a Key Ecological Function Area of the Loess Plateau

Evaluation of the ecological effects of eco-compensation policies helps analyze policy rationality and feasibility and provides scientific and practical bases for perfecting eco-compensation systems. Taking the key ecological function area of the Loess Plateau, China as a case study, we have evaluated ecosystem responses to the Grain-for-Green Project that commenced in 1999. Six indicators were selected to assess changes in ecosystem structure, quality and function. The results showed that implementation of the Grain-for-Green Project has reduced sloping cropland by 1571 km² and increased ecological land by 1337 km². The increase in ecological land alters ecosystem structures across the study area and the decline in sloping cropland reduces farming activity interference; both of these are conducive to the restoration of natural vegetation. From 2000 to 2010, the vegetation cover of grassland, desert and forest ecosystems increased 10.89%, 8.34% and 4.24% respectively and average NPP rose 51%, with an average annual growth rate of around 5%. This indicates that eco-compensation has promoted the improvement of ecosystem quality. Total biomass of ecosystems increased two times on average from 2000 to 2010, meaning that the carbon sequestration capacity of ecosystems also increased. The reduction in the area of water loss and soil erosion and the increase in retained runoff by forests indicate an improvement in ecosystem function and services on the Loess Plateau.     

Modeling net primary productivity of the terrestrial ecosystem in China from 1961 to 2005简

Net primary productivity （NPP） is the structure and function of the ecosystem. NPP can most important index that represents the be simulated by dynamic global vegetation models （DGVM）, which are designed to represent vegetation dynamics relative to environ- mental change. This study simulated the NPP of China＇s ecosystems based on the DGVM Integrated Biosphere Simulator （IBIS） with data on climate, soil, and topography. The appli- cability of IBIS in the NPP simulation of China＇s terrestrial ecosystems was verified first. Comparison with other relevant studies indicates that the range and mean value of simula- tions are generally within the limits of observations; the overall pattern and total annual NPP are close to the simulations conducted with other models. The simulations are also close to the NPP estimations based on remote sensing. Validation proved that IBIS can be utilized in the large-scale simulation of NPP in China＇s natural ecosystem. We then simulated NPP with climate change data from 1961 to 2005, when warming was particularly striking. The following are the results of the simulation. （1） Total NPP varied from 3.61 GtC/yr to 4.24 GtC/yr in the past 45 years and exhibited minimal significant linear increase or decrease. （2） Regional differences in the increase or decrease in NPP were large but exhibited an insignificant overall linear trend. NPP declined in most parts of eastern and central China, especially in the Loess Plateau. （3） Similar to the fluctuation law of annual NPP, seasonal NPP also displayed an insignificant increase or decrease; the trend line was within the general level. （4） The re- gional differences in seasonal NPP changes were large. NPP declined in spring, summer, and autumn in the Loess Plateau but increased in most parts of the Tibetan Plateau.     

1961–2005年中国陆地生态系统净初级生产力模拟（英文）

Net primary productivity(NPP) is the most important index that represents the structure and function of the ecosystem.NPP can be simulated by dynamic global vegetation models(DGVM),which are designed to represent vegetation dynamics relative to environmental change.This study simulated the NPP of China's ecosystems based on the DGVM Integrated Biosphere Simulator(IBIS) with data on climate,soil,and topography.The applicability of IBIS in the NPP simulation of China's terrestrial ecosystems was verified first.Comparison with other relevant studies indicates that the range and mean value of simulations are generally within the limits of observations;the overall pattern and total annual NPP are close to the simulations conducted with other models.The simulations are also close to the NPP estimations based on remote sensing.Validation proved that IBIS can be utilized in the large-scale simulation of NPP in China's natural ecosystem.We then simulated NPP with climate change data from 1961 to 2005,when warming was particularly striking.The following are the results of the simulation.(1) Total NPP varied from 3.61 GtC/yr to 4.24 GtC/yr in the past 45 years and exhibited minimal significant linear increase or decrease.(2) Regional differences in the increase or decrease in NPP were large but exhibited an insignificant overall linear trend.NPP declined in most parts of eastern and central China,especially in the Loess Plateau.(3) Similar to the fluctuation law of annual NPP,seasonal NPP also displayed an insignificant increase or decrease;the trend line was within the general level.(4) The regional differences in seasonal NPP changes were large.NPP declined in spring,summer,and autumn in the Loess Plateau but increased in most parts of the Tibetan Plateau.     

黄土高原植被恢复潜力研究

黄土高原从1999年开始大规模退耕还林（草）,植被覆盖发生了较大变化,对黄土高原植被恢复现状和恢复潜力进行评估具有重要意义。本文使用1999-2013年SPOT VEG NDVI数据,采用线性回归、Hurst指数分析法、统计学方法以及地理空间分析技术,对黄土高原植被恢复状况和潜力进行了探讨。结论主要为：① 1999年退耕还林（草）以来,黄土高原植被覆盖度呈显著上升趋势,黄土高原三分之二地区的植被将会持续改善;② 植被响应曲线分析表明,黄土区植被覆盖度和干旱指数呈显著的指数关系,且缓坡相关性大于陡坡。土石山区植被响应函数为线性函数,相关系数下降;③ 整个黄土高原地区平均植被恢复潜力为69.75%。植被恢复潜力值东南高而西北低,黄土高原东南地区植被恢复状况较好,其植被恢复潜力指数较小,而植被恢复潜力指数较高的地区主要为北方风沙区及西部丘陵沟壑区;④ 不同降水量条件下,植被恢复速度差别显著,其中降水量在375~575 mm之间的地区,植被恢复最快。植被恢复措施应该“因水制宜”,避免因造林带来的土壤干化加剧。研究结果以期为黄土高原生态文明建设提供科学支撑。     

Remote-sensing data reveals the response of soil erosion intensity to land use change in Loess Plateau,China

Developing an effective approach to rapidly assess the effects of restoration projects on soil erosion intensity and their extensive spatial and temporal dynamics is important for regional ecosystem management and the development of soil conservation strategies in the future. This study applied a model that was developed at the pixel scale using water soil erosion indicators (land use, vegetation coverage and slope) to assess the soil erosion intensity in the Loess Plateau, China. Landsat TM/ETM+ images in 2000, 2005 and 2010 were used to produce land use maps based on the object-oriented classification method. The MODIS product MOD13Q1 was adopted to derive the vegetation coverage maps. The slope gradient maps were calculated based on data from the digital elevation model. The area of water soil-eroded land was classified into six grades by integrating slope gradients, land use and vegetation coverage. Results show that the Grain-To-Green Project in the Loess Plateau worked based on the land use changes from 2000 to 2010 and enhanced vegetation restoration and ecological conservation. These projects effectively prevented soil erosion. During this period, lands with moderate, severe, more severe and extremely severe soil erosion intensities significantly decreased and changed into less severe levels, respectively. Lands with slight and light soil erosion intensities increased. However, the total soil-eroded area in the Loess Plateau was reduced. The contributions of the seven provinces to the total soil-eroded area in the Loess Plateau and the composition of the soil erosion intensity level in each province are different. Lands with severe, more severe and extremely severe soil erosion intensities are mainly distributed in Qinghai, Ningxia, Gansu and Inner Mongolia. These areas, although relatively small, must be prioritised and preferentially treated.     

黄土高原不同生态类型NDVI时空变化及其对气候变化响应

了解植被的时空变化及其气候主控因子可为植被保护和恢复提供重要的理论依据。基于MOD13A1和气象数据,分析了黄土高原Normalized Difference Vegetation Index （NDVI）时空变化特征,探讨了NDVI对水热条件在不同时间尺度的响应特征。结果表明：黄土高原植被覆盖状态正在不断的改善,气候呈暖湿的发展趋势;83.77%的植被退化区（退化区面积占研究区总面积的5.79%）海拔<2000 m且退化类型以不显著减少为主,不同覆被类型的退化区海拔分布及退化比例差异明显,湿地的退化面积比最高（23.91%）、其次耕地（11.88%）。年尺度上,NDVI与降水呈正相关的面积高于气温,约75.06%的区域受水分条件控制;灌木地（海拔分布<2200 m）、耕地（<3000 m）、草地（<3000 m）和裸地（600~3700 m）等植被生长受水分条件影响;森林（<1000 m、1700~3700 m）和湿地（>2500 m）的植被生长受热量影响。月尺度上,黄土高原植被NDVI对热量响应以滞后1个月为主,不同植被对水热响应的滞后性差异明显,草地、湿地、耕地和裸地对热量响应以滞后1个月为主;森林和灌木地则表现水热同期的特征。伴随滞后时间的推移,水分主控面积逐渐降低,热量成为影响植被生长的主要因素,水热主控及响应滞后性分布受海拔影响明显。     

近15 a黄土高原植被覆盖时空变化及驱动力分析

研究黄土高原地区植被覆盖变化及其驱动因素可以揭示研究区气候变化和人工生态调节过程对植被变化的影响。基于500 m分辨率的MODIS-NDVI数据和同期气象数据,运用均值法、斜率分析法、相关分析法及残差法,分析了2001-2015年黄土高原的植被时空演变变化特征及其驱动因素。结果表明：近15 a黄土高原植被在季度上总体都呈现增加趋势且存在一定差异,夏、秋季植被增加最为明显;黄土高原植被覆盖在空间上呈现自东南向西北递减的分布特征;植被NDVI变化在不同季节上都存在明显的空间差异;黄土高原植被NDVI对气温、降水的响应关系有明显的季节差异,并在空间上与降水的相关性显著,与温度相关性不明显;人类活动对植被覆盖变化有双重影响,其中生态恢复工程是黄土高原中部地区植被覆盖快速增加的重要因素。     

Soil erosion and its response to the changes of precipitation and vegetation cover on the Loess Plateau

Soil erosion is a major threat to our terrestrial ecosystems and an important global environmental problem. The Loess Plateau in China is one of the regions that suffered more severe soil erosion and undergoing climate warming and drying in the past decades. The vegetation restoration named Grain-to-Green Program has now been operating for more than 10 years. It is necessary to assess the variation of soil erosion and the response of precipita- tion and vegetation restoration to soil erosion on the Loess Plateau. In the study, the Revised Universal Soil Loss Equation （RUSLE） was applied to evaluate annual soil loss caused by water erosion. The results showed as follows. The soil erosion on the Loess Plateau between 2000 and 2010 averaged for 15.2 t hm-2 a 1 and was characterized as light for the value less than 25 t hm-2 a-1. The severe soil erosion higher than 25 t hm-2 a-~ was mainly distributed in the gully and hilly regions in the central, southwestern, and some scattered areas of earth-rocky mountainous areas on the Loess Plateau. The soil erosion on the Loess Plateau showed a deceasing trend in recent decade and reduced more at rates more than 1 t hm 2 a 1 in the areas suffering severe soil loss. Benefited from the improved vegetation cover and ecological construction, the soil erosion on the Loess Plateau was significantly declined, es- pecially in the east of Yulin, most parts of Yah＇an prefectures in Shaanxi Province, and the west of Luliang and Linfen prefectures in Shanxi Province in the hilly and gully regions. The variation of vegetation cover responding to soil erosion in these areas showed the relatively higher contribution than the precipitation. However, most areas in Qingyang and Dingxi pre- fectures in Gansu Province and Guyuan in Ningxia Hui Autonomous Region were predomi- nantly related to precipitation.     

黄河中游的侵蚀环境与植被恢复前景

黄土高原的土壤侵蚀和生态环境问题世界瞩目。在保证蓄水拦沙效益基础上,提高林、草保存率,使植被恢复得到最佳的生态效益,是黄土高原环境整治中亟待解决的关键问题。本文根据黄土高原不同空间地理位置的流域、重点县水文监测资料,研究了气候、地表覆被、土地利用方式的变化对流域侵蚀产沙的影响以及流域产沙与地理环境要素间的耦合关系,定量分析了黄土高原,特别是多沙粗沙区自然与人文要素对流域侵蚀产沙的综合影响和因子的权重分析,并利用天然降雨植被生态需水适宜性系数和林、草恢复度的概念,重点探讨了黄河中游主要产沙区、尤其是多沙粗沙区退耕还林等土地利用方式宏观格局变化与植被恢复前景。研究表明,在植被生长主要依赖天然降雨的黄土高原,生物措施(植被类型)要与自然带相适应,应根据植被恢复度和植被生态需水适应性系数来进行宏观植被的恢复与实施。这是目前在不断增长的人口压力下,进行水土保持,解决好经济发展与环境保护、减少垦殖率与保证老百姓的基本农田、造林种草与植被类型的自然适应性、以及控制泥沙作用中生物措施与工程措施合理布局等诸多矛盾的关键所在。     

近年来的黄土高原耕地时空变化与口粮安全耕地数量分析

基于遥感调查数据集定量分析了1990—2015年中国黄土高原地区耕地的时空变化特征和口粮绝对安全最小耕地保障面积的数量变化。结果表明：黄土高原耕地面积从1990年的192 529.65 km²至2015年的182 688.50 km²,净减少了9 841.14 km²,幅度达5.11%,其中2000—2010年的减幅最大,净减少8 483.00 km²;较大的耕地动态变化图斑主要分布于中部和西部区域,细碎的变化图斑广泛分布;耕地地类转出面积（31 875.82 km²）大于转入面积（21 815.25 km²）,耕地面积的增加主要由草地和林地转化而来,主要分布在灌溉农业区和东南部平原区,减少的耕地主要转化为草地和林地,主要分布在中部沟壑区的雨养农业区。此外,该时期耕地转化为建筑用地和交通用地等人工表面的面积逐渐增加,主要分布在东南部低海拔平原地区;黄土高原口粮绝对安全所需最小耕地保障面积呈明显减少特征（从1990年的70 913.37 km²下降到2015年的33 981.64 km²）,占该区耕地总面积比例呈明显缩减态势（从1990年的36.83%缩减到2015年的18.60%）,目前耕地总量的净减少未对口粮绝对安全的耕地保障数量造成大的影响。     

基于改进土壤冻融水循环的Biome-BGC模型估算青藏高原草地NPP

Biome-BGC模型被广泛用于估算植被净初级生产力（Net Primary Productivity, NPP）,但是该模型未考虑冻土区土壤冻融水循环过程对植被生长的影响。本文基于Biome-BGC模型,改进冻土区活动层土壤冻融水循环,估算了2000—2018年青藏高原高寒草地NPP。通过比较原模型和改进后的模型,并对NPP模拟结果的时空特征进行了分析,结果表明：① 增加冻融循环提高了NPP估算精度,青藏高原草地NPP均值由114.68 gC/(m²·a)提高到128.02 gC/(m²·a)。② 原模型和改进后NPP的空间分布差异较大,时间变化趋势差异不明显。③ 青藏高原草地NPP总量为253.83 TgC/a,呈东南向西北递减的空间格局,年均增速为0.21gC/(m²·a)（P=0.023）,显著增加的占17.85%,主要分布在羌塘高寒草原地带的大部分地区和藏南山地灌木草原地带的西部。④ 该冻融水循环改进方法简单可靠,具有在其他多年冻土区推广的价值。     

基于植被动态的黄土高原生态地理分区

生态地理区划作为自然区划的新分支,近年来受到国内外地理学者的广泛关注,其在认识地理分异规律及区域规划活动中发挥着重要作用。传统生态地理分区多依据自上而下的三级演绎途径,且对于多分区方案的对比与优选缺乏定量化准则。黄土高原作为中国典型的生态脆弱区,植被生长与恢复对缓解当地生态困境十分重要,因此以植被多年动态一致性特征作为分区合理性的评价指标,有助于准确揭示当地生境特点及分异规律。为此,选取热量类、水分类、地形类及地表覆被类共9个指标,采用自组织映射网络（SOFM）与GIS空间分析技术,基于黄土高原近30年来自然本底与覆被状况进行生态地理分区;并依循植被动态一致性准则,依据两步筛选法对多种方案进行优选,最终将黄土高原分为六大生态地理区。研究表明：黄土高原修正6分区方案在12个备选分区方案中效果最好;同时,修正6分区方案多年平均NPP离散系数最低,表明该分区内部离散程度最小。分区方案与既有分区方案相比具有较好的一致性,但由于区划尺度存在一定的差异,整体区域划分更为清晰。对生态地理分区方案优选定量方法的探索,有助于提升自下而上生态地理区划的客观性。     

NPP vulnerability of the potential vegetation of China to climate change in the past and future

Using the Integrated Biosphere Simulator, a dynamic vegetation model, this study initially simulated the net primary productivity (NPP) dynamics of China’s potential vegetation in the past 55 years (1961–2015) and in the future 35 years (2016–2050). Then, taking the NPP of the potential vegetation in average climate conditions during 1986–2005 as the basis for evaluation, this study examined whether the potential vegetation adapts to climate change or not. Meanwhile, the degree of inadaptability was evaluated. Finally, the NPP vulnerability of the potential vegetation was evaluated by synthesizing the frequency and degrees of inadaptability to climate change. In the past 55 years, the NPP of desert ecosystems in the south of the Tianshan Mountains and grassland ecosystems in the north of China and in western Tibetan Plateau was prone to the effect of climate change. The NPP of most forest ecosystems was not prone to the influence of climate change. The low NPP vulnerability to climate change of the evergreen broad-leaved and coniferous forests was observed. Furthermore, the NPP of the desert ecosystems in the north of the Tianshan Mountains and grassland ecosystems in the central and eastern Tibetan Plateau also had low vulnerability to climate change. In the next 35 years, the NPP vulnerability to climate change would reduce the forest–steppe in the Songliao Plain, the deciduous broad-leaved forests in the warm temperate zone, and the alpine steppe in the central and western Tibetan Plateau. The NPP vulnerability would significantly increase of the temperate desert in the Junggar Basin and the alpine desert in the Kunlun Mountains. The NPP vulnerability of the subtropical evergreen broad-leaved forests would also increase. The area of the regions with increased vulnerability would account for 27.5% of China.     

2000-2015年城市和工矿用地扩张对净初级生产力的影响

中国近15 a来快速的城市化和工业化对陆地净初级生产力（Net Primary Productivity,NPP）的影响是关系到碳循环和全球变化效应的重要问题。首先,本文基于VPM（Vegetation Photosynthesis Model）模型得到NPP数据,基于中国土地利用数据集（National Land Use Datasets of China（NLUD-China））获取2000-2015年城市和工矿用地数据,然后通过邻域替代法模拟2000-2015年间因中国城市和工矿用地扩张损失的陆地NPP。结果表明：2015年城市和工矿用地占中国国土总面积的1.2%,在2000-2015年间面积增加了70×10³ km²。城市和工矿用地扩张导致陆地NPP损失1.24 TgC·a^-1到3.14 TgC·a^-1,在2005-2010年损失NPP最多（3.14 TgC·a^-1）。耕地被建设用地占用是造成中国陆地NPP损失的重要原因,在2010-2015年共有13×10³ km²的耕地被城市和工矿用地占用,因此损失的NPP达1.51 TgC·a^-1,占中国城市和工矿用地扩张损失NPP总量的82%。从时空分布特征来看,21世纪初剧烈的城市扩张造成沿海和中部地区NPP损失严重（2000-2005年沿海地区主要因城市扩张损失NPP高达0.82 TgC·a^-1）,而2010-2015年主要因工矿用地扩张使西部地区NPP损失升高（在2010-2015年因工矿用地扩张损失NPP 0.46 TgC·a^-1,占中国NPP损失总量的30.81%）,NPP损失量呈现出从东高西低逐渐过渡到东西平衡的时空格局。从影响上分析,城市和工矿用地不透水地表比例（0.59±0.19）高于自然植被的不透水地表比例（0.29±0.14）,并且城市内部透水地表的平均标准化NPP（0.9）低于自然植被的平均标准化NPP（1.1）,是造成城市和工矿用地损失NPP的主要原因。     

近20 a中亚净初级生产力与实际蒸散发特征分析

中亚碳、水循环在气候变异和人为活动的影响下呈现新的时空特征。但由于观测数据稀缺,生态过程特殊,植被、土壤空间异质性强,中亚植被净初级生产力(NPP)、实际蒸散发(AET)的时空特征相关信息相对不足,且时效性不高。利用全球尺度的NPP、AET、土地覆被数据,气象站点与区域气候数据分析近20 a中亚地区NPP和AET的时空特征。结果表明：与1990年相比,2000年中亚地区农田NPP增幅小于自然植被,植被总固碳量增加了254.65 Tg C;近20 a中亚地区实际总蒸散量先增后降,农田对中亚水资源散失的贡献减小,自然植被的贡献增大,自然植被与农田面积变化决定中亚总蒸散量动态;北部农田区、东部山区及山前绿洲为NPP和AET的高值区,中西部荒漠为低值区。     

Aridity trend and response to vegetation restoration in the loess hilly region of northern Shaanxi Province

Detecting variation trend in dry-wet conditions can provide information for developing strategic measures to mitigate the impacts of global warming, particularly in dry regions. Taking the hilly region of northern Shaanxi on the Loess Plateau as a case area, this study analyzed the trend of aridity variation during 1981-2012, and explored the effect of vegetation restoration promoted by the Grain-for-Green (GFG) program implemented in 1999. The results indicated that the aridity in the region was non-significantly increased by 0.88% per year during 1981-2012, showing a drying trend. This drying trend and amplitude were changed by the influence of vegetation restoration promoted by the GFG program, based on two findings. The first one was that the aridity variation tended to increase during 1981-1999 while it turned to decrease during 2000-2012, with the regional mean relative change rate changed from 2.45% to -1.06%. This distinction was more remarkable in the loess gully region, where the vegetation was improved more obviously. The second one was that the mean vegetation coverage as indicated by EVI increased by 0.90% to 4.32% per year at county level, while the aridity decreased by 0.14% to 2.32% per year during 2000-2012. The regression analysis using the mean county data indicated that the change rate of aridity was negatively related to that of EVI with the coefficient of determination (R²) of 0.56, illustrating that around half of the aridity decline was explained by the EVI change. The mechanism of this effect was complicated, but it was found that the wind speed decline induced by the vegetation improvement could be an important contributor. It is concluded that the region became drier during 1981-2012, but the eco-restoration reduced the drying speed. However, this conclusion is involved in uncertainties, and further study based on experiments is needed to confirm the effect of the GFG-promoted vegetation restoration.     

西部地区生态状况变化及生态系统服务权衡与协同

西部大开发战略实施20年以来,一系列重大生态建设工程使得西部地区的生态状况和生态服务发生了重要变化,本文分析西部地区生态状况变化及其生态服务时空变化特征,并运用相关分析法研究其服务功能权衡协同关系。研究发现西部地区2000—2019年间：① 聚落和湿地生态系统面积显著增加,草地有逐年下降趋势。② 植被覆盖度呈波动上升趋势,存在年际差异且空间差异较大。③ 水源涵养服务有轻微下降趋势,下降区域主要分布在藏东南地区、三江源西部地区、喀斯特石漠化地区等;土壤保持服务波动中呈上升趋势,上升区域主要黄土高原地区、川滇西部地区、藏西北地区、藏东南地区等;防风固沙服务呈下降趋势,大幅下降区域主要位于内蒙古中西部地区、西藏和北疆部分地区。④ 生态系统供给与水源涵养、土壤保持主要为协同关系,与防风固沙主要为权衡关系且分布在农牧交错带地区。⑤ 生态工程区内生态系统服务协同程度大于非工程区。定量评估生态系统服务变化及其权衡协同关系有助于进行科学化生态管理,最大化生态效益。