Assessment of ecological quality in Northwest China (2000-2020) using the Google Earth Engine platform: Climate factors and land use/land cover contribute to ecological quality

The ecological quality of inland areas is an important aspect of the United Nations Sustainable Development Goals (UN SDGs). The ecological environment of Northwest China is vulnerable to changes in climate and land use/land cover, and the changes in ecological quality in this arid region over the last two decades are not well understood. This makes it more difficult to advance the UN SDGs and develop appropriate measures at the regional level. In this study, we used the Moderate Resolution Imaging Spectroradiometer (MODIS) products to generate remote sensing ecological index (RSEI) on the Google Earth Engine (GEE) platform to examine the relationship between ecological quality and environment in Xinjiang during the last two decades (from 2000 to 2020). We analyzed a 21-year time series of the trends and spatial characteristics of ecological quality. We further assessed the importance of different environmental factors affecting ecological quality through the random forest algorithm using data from statistical yearbooks and land use products. Our results show that the RSEI constructed using the GEE platform can accurately reflect the ecological quality information in Xinjiang because the contribution of the first principal component was higher than 90.00%. The ecological quality in Xinjiang has increased significantly over the last two decades, with the northern part of this region having a better ecological quality than the southern part. The areas with slightly improved ecological quality accounted for 31.26% of the total land area of Xinjiang, whereas only 3.55% of the land area was classified as having a slightly worsen (3.16%) or worsen (0.39%) ecological quality. The vast majority of the deterioration in ecological quality mainly occurred in the barren areas Temperature, precipitation, closed shrublands, grasslands and savannas were the top five environmental factors affecting the changes in RSEI. Environmental factors were allocated different weights for different RSEI categories. In general, the recovery of ecological quality in Xinjiang has been controlled by climate and land use/land cover during the last two decades and policy-driven ecological restoration is therefore crucial. Rapid monitoring of inland ecological quality using the GEE platform is projected to aid in the advancement of the comprehensive assessment of the UN SDGs.     

陕甘宁接壤区气候变化特征及其生态环境效应

为了能够正确反映陕甘宁接壤区多年气候变化的趋势,特别是1999年以后的气候改善状况,利用线性回归分析、趋势分析等方法对1951～2004年间39个测站的气温和降水的记录进行分析.结果表明:陕甘宁接壤区暖干化趋势明显,多年来一直处于干燥的状态,气温在波动中不断升高,降水在波动中不断减少,这种恶劣的气候状况严重影响了陕甘宁接壤区的生态环境建设.但是1999年之后,在气候暖干化的大背景之下,气温有所降低,降水有所增加,这是一个较好的气候变化趋势,对于气候的转型以及生态环境的重建有着重要的意义.     

Spatiotemporal changes of eco-environmental quality based on remote sensing-based ecological index in the Hotan Oasis,Xinjiang

The rapid economic development that the Hotan Oasis in Xinjiang Uygur Autonomous Region,China has undergone in recent years may face some challenges in its ecological environment. Therefore,an analysis of the spatiotemporal changes in ecological environment of the Hotan Oasis is important for its sustainable development. First, we constructed an improved remote sensing-based ecological index(RSEI) in 1990, 1995, 2000, 2005, 2010, 2015 and 2020 on the Google Earth Engine(GEE) platform and impleme...     

全球气候变化下黄土高原泾河流域近40年的气候变化特征分析

全球气候变化对于农业生产活动和生态环境保护有着深刻的影响。本文用时间序列分析中的距平曲线和短期预测方法分析了泾河流域内14个气象站点1960~1999(1971-2000)年气温和降水量的变化趋势,并用简单气候偏差指数计算了逐年的降水量变差;同时用变异系数计算了14个站点1960~1999(1971-2000)年的降水量年际变差。结果表明:近40年来14个站点的年均温度呈现明显的上升趋势,平均增温0.7℃略高,年平均增温率为0.0225℃/a;年降水量呈现微弱的减少趋势,但是波动幅度和变异系数都在增加,降水量年际间偏差呈现先减少后又增加的趋势。年内气候变化的趋势变化表现为:冬季温度升高;春季、夏季降水量占全年的百分比有显著增加趋势,而秋季降水所占的百分比显著减少。最后分析了全球变化背景下泾河流域近40年来气候出现的这种暖干化趋势对流域农业生产和生态环境的可能影响,可为相关部门调整农业结构、种植结构,优化种植模式等决策提供指导。     

Spatial-temporal variations of ecological vulnerability in the Tarim River Basin,Northwest China

As the largest inland river basin of China, the Tarim River Basin (TRB), known for its various natural resources and fragile environment, has an increased risk of ecological crisis due to the intensive exploitation and utilization of water and land resources. Since the Ecological Water Diversion Project (EWDP), which was implemented in 2001 to save endangered desert vegetation, there has been growing evidence of ecological improvement in local regions, but few studies have performed a comprehensive ecological vulnerability assessment of the whole TRB. This study established an evaluation framework integrating the analytic hierarchy process (AHP) and entropy method to estimate the ecological vulnerability of the TRB covering climatic, ecological, and socioeconomic indicators during 2000-2017. Based on the geographical detector model, the importance of ten driving factors on the spatial-temporal variations of ecological vulnerability was explored. The results showed that the ecosystem of the TRB was fragile, with more than half of the area (57.27%) dominated by very heavy and heavy grades of ecological vulnerability, and 28.40% of the area had potential and light grades of ecological vulnerability. The light grade of ecological vulnerability was distributed in the northern regions (Aksu River and Weigan River catchments) and western regions (Kashgar River and Yarkant River catchments), while the heavy grade was located in the southern regions (Kunlun Mountains and Qarqan River catchments) and the Mainstream catchment. The ecosystems in the western and northern regions were less vulnerable than those in the southern and eastern regions. From 2000 to 2017, the overall improvement in ecological vulnerability in the whole TRB showed that the areas with great ecological improvement increased by 46.11%, while the areas with ecological degradation decreased by 9.64%. The vegetation cover and potential evapotranspiration (PET) were the obvious driving factors, explaining 57.56% and 21.55% of the changes in ecological vulnerability across the TRB, respectively. In terms of ecological vulnerability grade changes, obvious spatial differences were observed in the upper, middle, and lower reaches of the TRB due to the different vegetation and hydrothermal conditions. The alpine source region of the TRB showed obvious ecological improvement due to increased precipitation and temperature, but the alpine meadow of the Kaidu River catchment in the Middle Tianshan Mountains experienced degradation associated with overgrazing and local drought. The improved agricultural management technologies had positive effects on farmland ecological improvement, while the desert vegetation in oasis-desert ecotones showed a decreasing trend as a result of cropland reclamation and intensive drought. The desert riparian vegetation in the lower reaches of the Tarim River was greatly improved due to the implementation of the EWDP, which has been active for tens of years. These results provide comprehensive knowledge about ecological processes and mechanisms in the whole TRB and help to develop environmental restoration measures based on different ecological vulnerability grades in each sub-catchment.     

中国西北干旱区和东部季风影响区冬季气温变化特征对比分析

利用我国西北干旱区138站、东部季风区375站1960～2006年47年的冬季气温资料,对其时空变化特征及气温变化倾向率进行了对比分析,并对其变化异同的原因进行了分析,结果表明:干旱区与季风区的时间变化规律基本一致,总体是在波动中呈一致的上升趋势,但西风地区的升温趋势较季风区更加明显;增温趋势与纬度有关,增温大区主要位...     

陕西省生态资本供求时空演变特征研究

依据生态足迹方法核算了陕西省各市1990年～2008年生态资本,并对其时空演变特征进行分析。结果表明:(1)1990-2008年陕西省各市生态资本供需态势可分为三类:西安市、宝鸡市、咸阳市和渭南市为I型(生态赤字扩大),铜川市、汉中市、安康市和榆林市为Ⅱ型(盈余转赤字),商洛市和延安市为Ⅲ型(盈余转持平);(2)生态压力变化表现出高压力高速扩张(如西安市)、中压力中速扩张(如咸阳市、宝鸡市、渭南市)、低压力低速扩张(如榆林市、延安市、铜川市、安康市、商洛市和汉中市)的特征;(3)关中地区人均资本需求量普遍较大,但是人均资本供给量普遍偏小,陕北和陕南地区人均生态资本需求量较小,但人均资本供给量较大。因此,关中地区生态资本供需缺口最大。2008年,生态赤字总量占陕西省89%。其中,西安市是陕西省最大的生态赤字贡献城市,占到了陕西省的41.4%,咸阳市第二(17.7%),渭南市第三(15.4%),宝鸡市第四(13.2%)。     

1960-2008年黑河流域地表干湿状况的时空变化分析

利用1960-2008年黑河流域16个气象站的逐日气象资料,采用FAO推荐的Penman-Monteith公式计算最大可能蒸散量,进而计算该流域的湿润指数,对地表干湿状况的时空变化特征及其主要影响因素进行分析。结果表明：黑河流域及其上、中、下游地区的湿润指数总体呈上升趋势,地表湿润状况有所改善,且湿润指数的年际波动性较明显,变异系数分别为14.97%、13.63%、25.47%、37.72%。除下游地区外,夏季的湿润指数变化速率最快,冬季的变化速率最慢;春季,黑河流域地表以变干趋势为主,其他季节均以变湿趋势为主。影响黑河流域地表干湿状况的主要因素是降水量,其他气候因子的变化对地表干湿状况起增强或削弱作用。     

Development of a large-scale remote sensing ecological index in arid areas and its application in the Aral Sea Basin

The Aral Sea Basin in Central Asia is an important geographical environment unit in the center of Eurasia.It is of great significance to the ecological protection and sustainable development of Central Asia to carry out dynamic monitoring and effective evaluation of the eco-environmental quality of the Aral Sea Basin.In this study,the arid remote sensing ecological index(ARSEI)for large-scale arid areas was developed,which coupled the information of the greenness index,the salinity index,the humidity index,the heat index,and the land degradation index of arid areas.The ARSEI was used to monitor and evaluate the eco-environmental quality of the Aral Sea Basin from 2000 to 2019.The results show that the greenness index,the humidity index and the land degradation index had a positive impact on the quality of the ecological environment in the Aral Sea Basin,while the salinity index and the heat index exerted a negative impact on the quality of the ecological environment.The eco-environmental quality of the Aral Sea Basin demonstrated a trend of initial improvement,followed by deterioration,and finally further improvement.The spatial variation of these changes was significant.From 2000 to 2019,grassland and wasteland(saline alkali land and sandy land)in the central and western parts of the basin had the worst ecological environment quality.The areas with poor ecological environment quality are mainly distributed in rivers,wetlands,and cultivated land around lakes.During the period from 2000 to 2019,except for the surrounding areas of the Aral Sea,the ecological environment quality in other areas of the Aral Sea Basin has been improved in general.The correlation coefficients between the change in the eco-environmental quality and the heat index and between the change in the eco-environmental quality and the humidity index were–0.593 and 0.524,respectively.Climate conditions and human activities have led to different combinations of heat and humidity changes in the eco-environmental quality of the Aral Sea Basin.However,human activities had a greater impact.The ARSEI can quantitatively and intuitively reflect the scale and causes of large-scale and long-time period changes of the eco-environmental quality in arid areas;it is very suitable for the study of the eco-environmental quality in arid areas.     

虫害对草地生态系统生物量危害损失评估

根据我国农业部统计数据,结合全国草地覆盖遥感数据,结合全国草地覆盖遥感数据,利用生态能学方法,评估了2000—2010年虫害对我国草地生态系统生物量危害损失。结果表明:11年期间全国由于虫害造成草地生物量损失约为年均230.9万t,损失量呈现先上升后下降后上升再下降的波动趋势,年份间危害差异变化很大,最高年份(2008年),损失328.5万t,占我国牧草需求量的32.8%。区域草地虫害强度排序为:中部西部东部,西部和中部共占比例高达96%;华北西北东北西南,其中内蒙古省年均损失量占全国总量的53.47%。这种特征与中国草被覆盖分布及防治科技发展程度密切相关。评估结果显示,我国草地生态系统虫害分布范围广,危害损失巨大,危害动态波动变化,应该加强对重点区域的草原虫害监测和预报,制定应对草原虫害治理策略。     

乌梁素海生态恢复机理与工程技术的研究

在我国干旱区典型草型湖泊—乌梁素海设立试验基地 ,进行生态恢复工程试验研究。研究表明 :乌梁素海受富营养化影响 ,正在向芦苇沼泽—碱蓬盐化草甸—白刺荒漠方向演化。生态恢复机理是 :( 1 )减少大型水生植物有机氮、磷向底质的沉降 ,削弱内源性营养物负荷的积累与储备 ;( 2 )减少大型水生植物死亡后矿化成氨态氮 ;( 3)控制底质中有机氮向水体释放生成氨态氮。采用机械化方式收割大型水生植物转移营养盐 ,抑制生物促淤效应以及对芦苇区进行园田化生态管理是乌梁素海生态恢复的关键技术 ,也是乌梁素海环境与资源持续发展的核心问题     

扎龙湿地近58年气温、降水变化特征研究

根据齐齐哈尔市1951-2008年气象观测数据,利用统计分析方法分析了58年来扎龙湿地气温和降水的变化情况。分析结果表明：年平均气温变化呈上升趋势,年降水量变化呈波动趋势,存在2～3年、6～7年变化周期。气温的季节变化呈不同程度的上升趋势,降水的季节变化呈不同程度的波动趋势;年均气温的代际变化较为和缓,呈小幅上升趋势,...     

内蒙古西部自然保护区生态环境保护可持续发展——以西鄂尔多斯保护区为例

恶劣的自然地理环境条件使得内蒙古西部自然保护区生态环境保护十分困难，而人类活动，特别是地区经济、城市工业等的发展又成为目前造成保护区生态环境恶化的直接原因，西鄂尔多斯自然保护区就是一典型例证。     

甘南州近35年蒸发量时空演变特征及对环境的影响

通过借助GIS空间分析技术、小波分析方法和数理统计理论,对甘南州近35年来蒸发量时空特征进行定性分析并阐述其对生态环境的影响.结果表明:近35年来甘南州蒸发量总体上呈上升趋势且通过了显著性检验,其中上升趋势最快的是甘南州东南部区域的舟曲和卓尼.从时间上看,蒸发量的变化呈波动式上升状态.其中1980s是整个甘南州蒸发量最...     

黑河中游植被覆盖率变化趋势及其驱动因子分析

利用2002~2011年的黑河干流中游归一化值被指数数据获得植被覆盖率变化趋势,选取合适的NDVI阈值将整个区域划分为"绿洲区"和"荒漠区",并分别探讨了地下水埋深、中游耗水量及累积降水量对两种区域面积和植被覆盖率变化的影响。结果表明:黑河干流中游植被覆盖率整体呈增长趋势,由2002年的32%增长到了2011年的36%,对植被覆盖率增长贡献最大的因素为绿洲区扩张,10年间绿洲区面积占比增长了10%;影响绿洲扩张的主要因素为地下水位埋深和中游耗水量,绿洲区植被覆盖率变化较小,可忽略其影响。荒漠区植被覆盖率的变化主要受累积降水量影响。利用地下水位埋深、中游耗水量、累积降水量可预测区域植被覆盖率的变化趋势,区分人类活动和气候变化对区域植被覆盖率的影响是可行的。     

Spatiotemporal analysis of drought variability based on the standardized precipitation evapotranspiration index in the Koshi River Basin,Nepal

Drought is an inevitable condition with negative impacts in the agricultural and climatic sectors, especially in developing countries. This study attempts to examine the spatial and temporal characteristics of drought and its trends in the Koshi River Basin(KRB) in Nepal, using the standardized precipitation evapotranspiration index(SPEI) over the period from 1987 to 2017. The Mann-Kendall test was used to explore the trends of the SPEI values. The study illustrated the increasing annual and seasonal drought trends in the KRB over the study period. Spatially, the hill region of the KRB showed substantial increasing drought trends at the annual and seasonal scales, especially in summer and winter. The mountain region also showed a significant increasing drought trend in winter. The drought characteristic analysis indicated that the maximum duration, intensity, and severity of drought events were observed in the KRB after 2000. The Terai region presented the highest drought frequency and intensity, while the hill region presented the longest maximum drought duration. Moreover, the spatial extent of drought showed a significant increasing trend in the hill region at the monthly(drought station proportion of 7.6%/10 a in August), seasonal(drought station proportion of 7.2%/10 a in summer), and annual(drought station proportion of 6.7%/10 a) scales. The findings of this study can assist local governments, planners, and project implementers in understanding drought and developing appropriate mitigation strategies to cope with its impacts.     

新疆艾比湖流域生态环境空间分异特征研究

本文着重从地质地貌、气候、植被、土壤及水环境等方面对艾比湖流域生态环境空间分异规律以及相互之间的联系,将有助于深刻了解该流域生态环境形成和演化的自然背景和各种资源组合的规律,这是解决艾比湖流域生态环境恶化问题关键出发点。综合分析艾比湖流域生态环境空间分异的气候、地质构造和地貌演化、地表水和地下水水文化学性质、土壤性状和水资源供应状况等自然地理要素,为该流域合理开发和配置各种资源提供理论依据,以保证该流域各种资源的可持续利用和生态环境的改善。     

近50年陕甘宁地区气候变化特征分析

根据陕甘宁地区气温、降水和蒸发量资料,运用回归分析、趋势分析和5年滑动平均法,分析该区1955-2004年的气候演变过程,比较不同气候要素在不同阶段的变化特点,特别是退耕还林近5来气候的变化趋势。结果表明:50年来年均温呈明显上升趋势,冬春温增幅较大;降水呈减少趋势,夏秋季降水急剧减少;蒸发量减少。近5年来,温度保持在较高水平,秋冬季降水有所增加,降水变率增大。最后,初探了陕甘宁地区气候变化的原因,肯定该区仍处于暖干期,指出气候变化特征对该区生态建设的指导意义。     

基于水资源和气候系统影响下的黑河流域生态环境变迁研究

分析了黑河流域生态环境恶化的现状和主要特征,主要表现为沙化加剧,绿洲萎缩;河水断流,湖泊干涸;地下水位下降,水质恶化等。在此基础上分析认为;水分条件是导致生态系统状态变化的主要驱动力,但气候变化在一定程度上加剧了生态环境恶化的进程和严重程度。因此,保护黑河流域本已非常脆弱的生态环境主要从研究水问题入手。除了调整种植业结构,大力发展节水农业;加强水资源管理以及普及节水意识等方面外,更重要的是要创新水问题研究思路,实行虚拟水战略。     

近50 a中国西北地区东部降水特征

利用我国西北地区东部54个气象站1960-2009年的降水资料,采用M-K检验和小波分析方法,对该地区的降水特征进行了分析。结果表明：① 西北地区东部降水量呈微弱下降趋势,1990年后降水减少趋势更为明显,Ⅱ区降水变化趋势较Ⅰ区更加显著;② 该地区降水频次以弱降水和中等强度降水为主,占降水总天数的70%以上,弱降水频次减少趋势显著;③ 中等强度降水和强降水的降水量占全年降水的75%以上,中等降水的降水量呈减少趋势,是造成年降水量减少的主要原因;④ 小波分析结果显示,年降水、中等降水和强降水序列均存在显著的3 a和5 a短周期,其中Ⅰ区和Ⅱ区的中等降水和强降水小波周期在20世纪70年代之后完全不同,中等降水的减少与70年代周期的变长密切相关。