Spatial-temporal patterns of vegetation dynamics and their relationships to climate variations in Qinghai Lake Basin using MODIS time-series data

Global warming has led to significant vegetation changes in recent years. It is necessary to investigate the effects of climatic variations（temperature and precipitation） on vegetation changes for a better understanding of acclimation to climatic change. In this paper, we focused on the integration and application of multi-methods and spatial analysis techniques in GIS to study the spatio-temporal variation of vegetation dynamics and to explore the vegetation change mechanism. The correlations between EVI and climate factors at different time scales were calculated for each pixel including monthly, seasonal and annual scales respectively in Qinghai Lake Basin from the year of 2001 to 2012. The primary objectives of this study are to reveal when, where and why the vegetation change so as to support better understanding of terrestrial response to global change as well as the useful information and techniques for wise regional ecosystem management practices. The main conclusions are as follows：（1） Overall vegetation EVI in the region increased 6% during recent 12 years. The EVI value in growing seasons（i.e. spring and summer） exhibited very significant improving trend, accounted for 12.8% and 9.3% respectively. The spatial pattern of EVI showed obvious spatial heterogeneity which was consistent with hydrothermal condition. In general, the vegetation coverage improved in most parts of the area since nearly 78% pixel of the whole basin showed increasing trend, while degraded slightly in a small part of the area only.（2） The EVI change was positively correlated with average temperature and precipitation. Generally speaking, in Qinghai Lake Basin, precipitation was the dominant driving factor for vegetation growth; however, at different time scale its weight to vegetation has differences.（3） Based on geo-statistical analysis, the autumn precipitation has a strong correlation with the next spring EVI values in the whole region. This findings explore the autumn precipitation is an important indicator, and then, limits the plant growth of next spring.

Glacier extent changes and possible causes in the Hala Lake Basin of Qinghai-Tibet Plateau

Glacier is a common sensitivity indicator of environmental and global climate change.Examining the relationship between glacier area and climate change will help reveal glacier change mechanisms and future trends.Glacier changes are also of great significance to the regulation of regional water resources.This study selected the Hala Lake Basin in the northeastern Qinhai-Tibet Plateau as a study area,and examined the relationships between the temporal and spatial change of glaciers in the northeastern Qinghai-Tibet Plateau and climate change based on remote sensing imagery,climatological data,and topographic data during the past 30 years.Results showed that glacier area in the Hala Lake basin fluctuated and decreased from106.24 km2 in 1986 to 78.84 km2 in 2015,with a decreasing rate of 0.94 km2·yr-1.The number of glacier patches,mean patch area,and largest patch index all decreased from 1986 to 2015,while the splitting index increased from 1986 to 2015,indicating that the landscape fragmentation of glacier in the Hala Lake Basin was increasing significantly during the study period.Glacier area change was mainly concentrated in the slopes>25°with an altitude of 4500-5000 m,and the retreating rate of glacier of sunny slope was obviously higher than that of shady slope.Geometric center of glacier in the basin moved from southwest to northeast towards high altitude.Results of the response of glacier extent to climate change showed that temperature was the dominant factor affecting glacier area dynamic change in the Hala Lake Basin.It is predicted that in future several years,the glacier area will decrease and fragment continually as a result of global warming on the Tibetan Plateau.

Dating of two thermokarst lakes in Beiluhe Basin, Qinghai-Tibetan Plateau

Most of the thermokarst lakes are spread appreciably in Beiluhe Basin,Qinghai-Tibet Plateau,China,where ice-rich permafrost exists.Two typical thermokarst lakes with differing area and depth were examined to ascertain their age.We obtained lake-bottom samples of 50 cm length from lake BLH-A and 25 cm length from lake BLH-B.Environmental 137 Cs and 210 Pb and radiocarbon age dating techniques were applied to the 50 cm and 25 cm samples,respectively.The results indicate that the initiation of BLH-A is about 800-900 a B.P.,and approximately 1,450±30 a B.P.to 2,230±30 a B.P.for BLH-B.These results will provide scientific bases for sedimentological study and thermokarst activity in Beiluhe Basin.

Effects of climate change and land use/cover change on the volume of the Qinghai Lake in China

Qinghai Lake is the largest saline lake in China.The change in the lake volume is an indicator of the variation in water resources and their response to climate change on the Qinghai-Tibetan Plateau(QTP)in China.The present study quantitatively evaluated the effects of climate change and land use/cover change(LUCC)on the lake volume of the Qinghai Lake in China from 1958 to 2018,which is crucial for water resources management in the Qinghai Lake Basin.To explore the effects of climate change and LUCC on the Qinghai Lake volume,we analyzed the lake level observation data and multi-period land use/land cover(LULC)data by using an improved lake volume estimation method and Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model.Our results showed that the lake level decreased at the rate of 0.08 m/a from 1958 to 2004 and increased at the rate of 0.16 m/a from 2004 to 2018.The lake volume decreased by 105.40×10^(8) m^(3) from 1958 to 2004,with the rate of 2.24×10^(8) m^(3)/a,whereas it increased by 74.02×10^(8) m^(3) from 2004 to 2018,with the rate of 4.66×10^(8) m^(3)/a.Further,the climate of the Qinghai Lake Basin changed from warm-dry to warm-humid.From 1958 to 2018,the increase in precipitation and the decrease in evaporation controlled the change of the lake volume,which were the main climatic factors affecting the lake volume change.From 1977 to 2018,the measured water yield showed an"increase-decrease-increase"fluctuation in the Qinghai Lake Basin.The effects of climate change and LUCC on the measured water yield were obviously different.From 1977 to 2018,the contribution rate of LUCC was -0.76% and that of climate change was 100.76%;the corresponding rates were 8.57% and 91.43% from 1977 to 2004,respectively,and -4.25% and 104.25% from 2004 to 2018,respectively.Quantitative analysis of the effects and contribution rates of climate change and LUCC on the Qinghai Lake volume revealed the scientific significance of climate change and LUCC,as well as their individual and combined effects in the Qinghai Lake Basin and on the QTP.This study can contribute to the water resources management and regional sustainable development of the Qinghai Lake Basin.

Stable isotopes of water as a tracer for revealing spatial and temporal characteristics of groundwater recharge surrounding Qinghai Lake,China

Studying spatial and temporal characteristics of regional groundwater recharge will guide the scientific management and sustainable development of regional water resources.This study investigated stable isotopes(δ^(18)O and δ^(2) H)of precipitation,groundwater,river water and lake water during 2019-2020 in Qinghai Lake Basin to reveal the spatial and temporal characteristics of groundwater recharge.The local meteoric water line was simulated using ordinary least squares regression(δ^(2) H=7.80δ^(18)O+10.60).The local evaporation lines of the river water,lake water and groundwater were simulated asδ^(2) H=6.21δ^(18)O-0.72,δ^(2) H=5.73δ0-3.60 and δ^(2) H=6.59δ0+1.76,respectively.The δ^(2) H and δ^(18)O of river water and groundwater were in more depleted values due to the recharge by precipitation at high altitudes or precipitation effects,and theδ^(2) H andδ^(18)O of the lake water were in more enriched values because of evaporation.The relationship between the δ^(2) H and δ^(18)O of groundwater and river water was not significantly different,indicating a strong hydrological connection between the groundwater and river water surrounding Qinghai Lake.Additionally,the maximum values of δ^(18)O and the minimum values of lc-excess of groundwater in most regions were both in August,and the minimum values of δ^(18)O and the maximum values of lc-excess of groundwater in most regions were both in October.Therefore,the groundwater was recharged by soil water with strong evaporation in August and recharged by precipitation at high altitudes in October.The recharge rate of groundwater was relatively fast in areas with large slopes and large hydraulic gradients(e.g.,south of Qinghai Lake),and in areas with strong hydrological connections between the groundwater and river water(e.g.,the Buha River Valley).Those results can provide data support for protection and utilization of water resources in Qinghai Lake Basin,and provide reference for groundwater research in closed lake basins on the Qinghai-Tibet Plateau.

Tectonic Landform of Quaternary Lakes and Its Implications for Deformation in the Northern Qinghai-Tibet Plateau

The Hohxil region in the northern Qinghai-Tibet Plateau is occupied by numerous plateau lakes, which have long been inferred as being tectonic products. However, so far little evidence has been found to support this tentative inference. Field survey and morphotectonic analysis of TM satellite images in the eastern segment of the Hohxil region revealed that Kusai Lake and Yelusu Lake are S- shaped pull-apart basins, which were dominated by left strike-slip master faults trending WNW-ESE. The pull-apart distances of the two lakes are analyzed to be 〈15-20 km and 15 km respectively. Based on studies of the faulting rate, the initiation ages of the pull-apart basins are suggested to be approximately in the Early Pleistocene. The pull-apart basin tectonics is further regarded as a common mechanism for the widely distributed large lake basins in the northern Qinghai-Tibet Plateau. Regional distribution of these pull-apart basins and their substantial intra-block slip suggest that a sinistral shear stress, which is independent of the distinguished strike-slip faults, has been imposed on across the northern Qinghai-Tibet Plateau. Thus, the intra-block slip may be an important expression of the eastward extrusion of the Plateau crustal material in accommodating the ongoing continent-continent convergence between India and Eurasia. The revelation of pull-apart tectonics within the Plateau hinterland provides field evidence and a possible style of deformation for the newly proposed continuous deformation by the global positioning system （GPS） measurement across the northern Qinghai-Tibet Plateau. A model, with respect to systematic tectonic landform development, for pull- apart basins is finally proposed.

青海湖流域种子植物区系研究

青海湖流域位于青海省东部(36°15′~38°15′N,97°50′~101°45′E),处于青藏高原和黄土高原的过渡地带,海拔3 160~4 953 m,全区面积约29 660 km2,属于高原大陆性气候。该区有种子植物823种,隶属于61科231属,依次为青海种、科、属数的23.13%、62.89%和38.82%。区系分析结果表明:(1)该区系的种类仅有2.78种/km2,这在唐古特地区的众多自然区域中相对并不丰富。(2)包括中国特有植物种类在内,该区系的温带成分占99.00%,以绝对优势确定了本区系明显的温带性质。(3)木本种类少,少有古老的和原始的类群,而是以多年生草本为核心的植物区系。(4)该区的一些中国特有种是经其广布的亲缘种衍生而来,这是该区系年轻和衍生的性质的具体体现。(5)我国华北区系和西南高山区系均对该区具有不同程度的影响。(6)特有属少,特有种多数为水生植物,表现出青海湖独特而隐域性的水湿环境的特化结果。(7)中国特有种的核心成分是出现种类最多的甘肃—西藏—四川亚型。而在青藏高原植物亚区中,该区隶属于其中的唐古特地区。

气候变化对青海湖水位的影响及机理分析

为系统分析气候变化背景下青海湖水位的变化过程及影响机理,本研究利用1971—2020年青海湖流域的站点观测资料,运用时间序列分析、地统计学插值和相关性分析相结合的方法,定量分析了青海湖流域水文和气象要素的时空变化特征,并基于全球气候模式预估了不同情景下降水和水位的变化趋势。结果表明:过去50年间青海湖水位和水面面积呈先下降后上升的过程,径流量、降水量和气温呈增加趋势,而蒸发量则明显减小;青海湖水位受径流量、降水量、气温和蒸发量的影响非常显著,相关系数分别高达0.92、0.92、0.88和0.81;2021—2040年青海湖水位在不同情景下均呈上升趋势,年平均水位上升速率分别为0.218、0.187、0.125和0.132 m/a。本研究将为气候变化背景下高原湖泊水循环机理揭示及其量化分析提供科学依据。

青海湖流域植被动态变化驱动力及空间粒度效应

基于Landsat遥感影像分析1986~2020年青海湖流域植被覆盖度时空变化特征,结合多元线性回归和地理探测器,考虑气候、地表及人类足迹的影响,阐明时间和空间尺度下植被覆盖度变化的机制,并探讨空间粒度对驱动因素及其相对贡献的影响.结果表明:(1)近35年来青海湖流域植被状况整体改善,表现为中等、中高覆盖度植被面积增加,其中环青海湖东北部及布哈河上游植被覆盖度呈显著增加趋势;(2)时间尺度上,流域平均植被覆盖度变化受气候暖湿化和生态恢复工程驱动;(3)空间尺度上,植被覆盖度变化由气候、地形、植被和土壤控制,解释力较大因素为气温(0.41),高程(0.34)和降水(0.30).气候、地形和人为因素对植被覆盖度的影响存在交互增强效应,气温、高程对交互效用具有控制作用,其中气温与距水系距离、降水和人类足迹的交互较为显著;(4)空间粒度对植被覆盖度空间变化驱动因素的贡献具有显著影响,考虑气候、地表和人为因素交互作用时青海湖流域植被覆盖度空间变化最佳研究粒度为6km.

柴达木盆地可鲁克湖沉积物表层花粉散布规律及其对区域植被的指示意义

可鲁克湖是柴达木盆地东部荒漠区重要的生态屏障,对全球气候变化响应十分敏感。利用沉积物化石花粉重建湖泊生态系统演变历史及其对全球气候变化响应过程和机制的分析是当前重要的研究方向,本研究系统采集了可鲁克湖沉积物表层样品开展花粉分析。研究结果显示,花粉组合以藜科、禾本科、蒿属、莎草科为主。花粉总浓度在湖泊沉积中心及偏西南区域显著偏高,其中藜科、莎草科、蒿属、白刺属、麻黄属、紫菀属花粉与总浓度变化特征较为一致,而禾本科花粉在湖泊东南部显著富集。湖泊沉积物中的藜科和蒿属花粉较好地指示了柴达木盆地东部灌木-矮灌木荒漠和荒漠草原整体植被特征,而禾本科和莎草科花粉主要指示湖岸周边隐域性沼泽和河滩草甸植被群落;白刺属花粉对湖泊北岸一级阶地上的白刺群落发育和湖面变化具有较好的指示意义,谷物类禾本科和十字花科花粉能较为灵敏地反映湖泊附近的农耕活动,桦木属和云杉属花粉则主要由风力和河流远距离输入。研究揭示了可鲁克湖水深、水动力条件、湖岸周围植被群落分布以及风力作用是影响花粉散布和沉积的重要影响因素,此项研究也为青藏高原湖泊沉积物花粉组合的精确解译提供了重要数据资料和分析依据。

2000—2020年青海湖流域植被降水利用效率时空变化

植被降水利用效率(PUE)是评价植被生产力对降水量时空动态响应特征的重要指标。以年净初级生产力(NPP)数据、年降水量数据为基础,利用地理信息系统(GIS)和遥感(RS)技术,计算并研究了2000—2020年青海湖流域植被降水利用效率时空分布格局及其地形效应,结合年均气温、年均地表温湿度、年生长季光合有效辐射吸收系数和年植被覆盖度等数据,探讨了PUE与各因子间的相关关系。结果表明:(1)青海湖流域单位像元(1 km^(2))PUE平均值在0.4—0.7 gC m^(-2)mm^(-1)间变化,平均为0.54 gC m^(-2)mm^(-1),且在年际间无显著变化趋势(R^(2)=0.05,P≥0.05)。在空间上,青海湖流域多年PUE平均值环湖呈现不均匀分布,除青海湖东岸外,PUE值随湖面距离增大呈减小趋势;其高值区主要集中分布在青海湖西岸和南岸的半环区;年PUE变化趋势的斜率值为-0.05—0.04 gC m^(-2)mm^(-1)a-1,其中显著变化的区域占流域面积的29.63%。(2)青海湖流域多年PUE平均值在海拔效应和坡度坡向两种不同微地形效应下表现出明显的差异。海拔每升高50 m,PUE值将减少0.02 gC m^(-2)mm^(-1);随坡度增加,PUE值呈降低趋势,平坡至险坡(>45°)的变化范围为0.3—0.61 gC m^(-2)mm^(-1);不同坡向PUE值表现为由东北坡向西南坡递减,范围为0.52—0.56 gC m^(-2)mm^(-1)。(3)在空间上,青海湖流域PUE值与地表温度、光合有效辐射吸收系数、植被覆盖度和叶面积指数相关性较为明显。沿海拔梯度,空气温度和地表温度与PUE呈极显著正相关(R^(2)=0.94,P<0.01;R^(2)=0.98,P<0.01),光合有效辐射吸收系数、植被覆盖度和叶面积指数与PUE显著正相关(R^(2)=0.89,P<0.05;R^(2)=0.90,P<0.05;R^(2)=0.86,P<0.05),地表土壤湿度与PUE无显著相关性(R^(2)=0.16,P≥0.05)。评估了青海湖流域植被降水利用效率的特征及其与各因子间的相关关系,明确了植被对降水的利用能力及其耗水特性,可为青海湖流域植被保护和国家公园建设提供理论参考。

2000-2020年青海湖流域植被净初级生产力时空格局及驱动分析

[目的]明确2000—2020年青海湖流域植被净初级生产力(Net Primary Productivity,NPP)时空格局变化特征,探究影响植被NPP的主要因素及驱动比例,为青海湖流域基础科学研究提供参考。[方法]以青海湖流域为研究区域,基于2000—2020年植被NPP、气温、降水量、植被覆盖度、人类活动强度数据,采用ArcGIS空间分析、地理探测器模型等方法,分析植被NPP在子流域、海拔、微地形上的时空变化,并对流域NPP与气温、降水量和植被覆盖度的相关性及植被NPP的驱动要素进行研究。[结果](1) 21年间青海湖流域年植被NPP逐年波动上升,增速为2.22 g C·m^(2)/a,空间上自西北向东南递增。(2)年植被NPP与年均气温、年降水量、年植被覆盖度的显著相关区域占流域面积比依次为40%,9%,59%。年均气温和年降水量与年植被NPP的一级偏相关系数显著区域占流域面积比分别是59.26%和33.39%。(3)驱动分析表明气温(q=0.58)、海拔(q=0.54)、人类活动(q=0.38)是流域NPP的主要驱动因子,并且因子交互解释力强于单因子解释力。[结论]2000—2020年青海湖流域植被NPP整体逐年增长,在海拔、子流域和微地形格局上表现出显著的空间分异性,气温、海拔、人类活动的交互驱动是流域NPP的主要驱动类型。

基于ANUSPLIN插值法的青海湖流域数字流域模型研究

基于青海湖流域2010—2020年的降水资料,利用ANUSPLIN插值法反演了青海湖流域的降水时空分布。结合水文气象及地球遥感解译等资料,构建了青海湖流域数字流域模型,并对模型参数进行了率定和验证。将模型应用于探究下垫面变化对流域水文过程的影响,解析了青海湖流域水循环演变规律和驱动机制,并对关键参数进行了敏感性分析。结果表明:在率定期和验证期,布哈河口站纳什效率系数分别为0.72和0.67,刚察站分别为0.81和0.84,说明数字流域模型适用于青海湖流域降水长时空序列模拟;土壤垂向下渗速率和土壤水平渗透速率主要影响径流的峰值,其中表层土水平渗透速率最敏感;土壤孔隙率及初始含水量主要影响径流的基流,其中中层土初始含水量最敏感。

青海湖流域主要河流的生态需水

为确保流域生态系统健康发展,实现水资源合理配置,基于青海省水文水资源测报中心实测布哈河口站和刚察站1961-2020年长时间序列数据,通过三性审查验证数据符合计算条件,径流量通过滑动T检验法和MannKendall(M-K)检验法进行趋势变化分析和径流突变检验。采用Tennant、近10年最枯月平均流量法、90%保证率月平均流量法和年内展布法计算布哈河与沙柳河河道内生态需水量。以改进的Tennant评价标准和满足度对4种方法进行对比分析,结果表明:年内展布法计算布哈河生态需水量较为合理,90%保证率月平均流量法计算沙柳河生态需水量较为合理,最终得出布哈河年平均生态需水量为38.4亿m^(3),沙柳河年平均生态需水量为14.12亿m^(3)。

基于生态评价的生态保护修复分区研究——以青海湖流域为例

针对我国生态脆弱区生态保护修复问题,以青海湖流域为例,在生态系统服务重要性和生态敏感性基础上识别关键性生态空间,同时结合流域生态安全格局及典型生态问题,划定生态保护修复分区,并提出不同分区的修复策略。结果表明:青海湖流域内生态系统服务极重要区占流域总面积的63.2%,生态极敏感区占流域总面积的6.55%;青海湖流域的核心型生态空间面积为18746.72 km^(2),优先型生态空间面积为5324.26 km^(2),其共同构成的关键性生态空间占流域总面积的81.15%;根据流域上中下游、地形等实际自然地理特征,提出构建青海湖流域“一网四区”的生态安全格局,结合生态安全格局和关键性生态空间及典型生态问题,将青海湖流域划定为6个生态保护修复分区,并有针对性地提出生物多样性保护、构筑湿地生态系统网络和水土保持等工程措施。

基于生态系统服务的青海湖流域生态风险评估及其空间异质性影响因素分析

青海湖流域是我国西北部的“气候调节器”和“空气加湿器”,其生态风险管控对青藏高原乃至我国西部的生态保护和可持续发展都有着重要意义。基于InVEST模型对青海湖流域2005年、2010年、2015年、2020年产水量、土壤保持、生境质量和碳储存4项生态系统服务进行定量评估,借助熵权—TOPSIS法,以生态系统服务的相对损失量来构建区域生态风险指数,并运用地理探测器和地理加权回归模型分析自然—社会要素对青海湖流域生态风险空间异质性的影响。结果表明:(1)2005—2020年青海湖流域产水量、土壤保持、生境质量和碳储存均呈现波动增加的趋势,增幅分别为10.17%、18.36%、9.84%、3.47%,各项生态系统服务的高值区分布于河流上游的河源区和植被覆盖率高的林地区域;(2)2005—2020年青海湖流域生态风险较高,但呈现波动降低的趋势。高风险区主要位于湖区、环湖区、布哈河河谷以及流域西北部;(3)青海湖流域生态风险的空间格局受地形及高程因子主导,但人为干扰度的影响力呈逐年上升趋势。驱动因子交互作用的解释力显著高于单因子;(4)主要驱动因子对研究区生态风险的作用方向及强度存在明显的空间分异特征,坡度呈正相关,年平均气温呈负相关,归一化植被指数(NDVI)和人为干扰度呈现出正负两种效应,但以正向效应为主。研究结果对青海湖流域生态风险管控和高原生态环境保护有一定借鉴意义。

基于MODIS数据青海湖流域内积雪和湖冰物候变化研究

物候变化对气候响应和生态环境方面的研究具有重要意义。本文基于近20年的MODISV6积雪产品和反射率产品,分别获取了青海湖流域的积雪和湖冰物候,并分析了二者的空间分布特征。在此基础上,采用Theil-Sen Median和一元线性回归法分析了积雪物候与湖冰物候的变化趋势,以及低海拔区域内二者的相关关系。结果表明:(1)青海湖湖冰开始冻结日期、开始消融日期和湖冰存在期分别在321~389d、425~464d和0~174d。整体上,开始冻结日期和开始消融日期均呈推迟趋势,推迟率分别为0.3 d·a^(-1)和0.2 d·a^(-1);湖冰存在期则呈缩短趋势,缩短率为0.6 d·a^(-1)。湖冰物候与经度具有显著相关性,湖面自东向西,湖冰开始冻结日期推后、开始消融日期提前、湖冰存在期缩短。(2)青海湖流域积雪初日、积雪终日和积雪日数分别在275~404d、353~484d和3~209d。其中积雪初日和积雪终日整体上分别呈提前趋势和推迟趋势,变化率分别为0.8d·a^(-1)和0.11d·a^(-1);积雪日数呈增长趋势,增长率为0.6d·a^(-1)。积雪物候与海拔密切相关,随着海拔的增加,积雪初日提前、积雪终日推迟、积雪日数增加。(3)冬季负积温和气温是影响湖冰物候的重要因素。冬季负积温和气温升高会导致湖冰开始冻结日期推迟、湖冰开始消融日期提前、湖冰存在期缩短。对于积雪物候,积雪日数与气温之间呈显著的负相关关系,气温下降,积雪日数增加。(4)低海拔流域内部分积雪与湖冰物候参数之间存有潜在联系。积雪初日与湖冰开始冻结日期之间具有较为显著的负相关关系,相关性系数为-0.404。而积雪作为湖面保温层,积雪日数的增加也会很大程度上减缓湖冰消融速度,致使湖冰消融日期推迟,因此二者呈一定正相关关系,相关性系数为0.349。本研究所揭示的流域内生态系统变化规律,对当地生态系统具有积极意义,可以为青海湖流域环境监测提供理论依据和技术支持。

青海湖流域生态系统服务空间分异规律及驱动力研究

在青海湖流域拟建国家公园的背景下,生态系统服务空间分异及其驱动因素的探析,可以极大的促进生态环境保护与修复政策制定及区域可持续发展。以青海湖流域为研究对象,基于2010-2020年的土地利用变化,分析生态系统服务的动态变化,探讨了生态系统服务的空间异质性,并引入地理探测器模型探究了生态系统服务空间分异的自然和社会经济驱动因素。结果表明,1)2010-2020年草地作为主要地类变化幅度小;水域面积增幅最大,其主要源于未利用地和草地的转入。2010-2020年ESV表现为弱递增趋势,总生态系统服务价值(ESV)由1.35×10^(3)亿元增加到1.37×10^(3)亿元,增加了1.48%;其中,水域贡献率最大(1.04×10^(3)亿元以上),其次是草地(274亿元以上)。生态服务功能以调节服务为主,贡献量达到1.12×10^(3)亿元以上。2)青海湖流域ESV呈现出从湖体向周围递减的空间格局,并表现出显著的高程依赖性;流域ESV存在显著的空间正相关(Moran’s I均为正数)和聚集分布;高高值和低低值聚集区为空间上的主要聚集区,高高值聚集区主要聚集在低海拔区,低低值聚集区则主要分布在高海拔区,高高值和低低值聚集区在2010-2020年均呈递增趋势,但低低值聚集区增幅极小。3)ESV空间异质性是自然地理和社会经济因素协同作用的结果,自然因素影响力表现出更高的敏感性,海拔和气候所体现出的空间异质性是ESV的主要驱动因素。低海拔地区ESV空间聚集性等结果表明,今后仍需关注人类活动和气候变化对ESV的影响和权衡,以缓解人地矛盾进而推进青海湖国家公园建设。该研究可为区域生态系统保护和管理奠定科学基础,也可为决策者评估生态屏障区的生态安全提供理论基础和参考。

沙柳河流域1969—2020年径流变化及归因分析

以青海湖盆地沙柳河流域为研究对象,利用Penman-Monteith公式探究流域潜在蒸散发量ET0时空变化特征,运用Mann-Kendall及Pettitt检验法检验沙柳河流域1969—2020年径流变化趋势及突变特征,基于水热耦合平衡理论分析量化各因素对径流变化的贡献。1969—2020年沙柳河流域潜在蒸散发量呈下降趋势,平均下降速率为4.8 mm/10 a。突变检验识别径流在2004年存在突变点(2004年之前径流减少,之后显著增加)。基于流域水热耦合平衡方程的径流变化弹性分析表明,研究期内年降水量、潜在蒸散发量、下垫面参数分别增大10%时,年径流量增加14.4%、减少4.4%、减少8.8%。径流变化归因分析结果显示,气候变化和人类活动对沙柳河流域径流量减少的贡献率分别为70.4%和29.6%,气候变化是导致沙柳河流域径流量增加的主要原因,且降水是影响径流量变化的主要因素。

青海湖流域草地植被与物种多样性空间分异研究

【目的】揭示青海湖流域草地植被及物种多样性的空间分异规律。【方法】基于野外调查和遥感技术对草地进行分区,采用Patrick丰富度指数、Shannon-wiener多样性指数、Pielou均匀度指数和Simpson优势度指数分析各类型区物种多样性和重要值。【结果】1)青海湖流域草地主要以禾本科、菊科及莎草科为主。温性草原优势种以芨芨草、短花针茅和西北针茅为主;中海拔的高寒草地形成以冰草、冷蒿和紫花针茅为优势种的草地类型;高寒草甸以嵩草属为主,形成了高山嵩草、矮嵩草、北方嵩草、线叶嵩草草地类型。2)低盖度区以紫花针茅和北方嵩草为优势种,具有耐寒、耐盐碱特点;中盖度区优势种为高山嵩草、线叶嵩草、藏嵩草;高盖度区多以芨芨草、克氏针茅、紫羊茅为优势种,群落结构层次明显。3)不同盖度分区的丰富度指数、多样性指数和均匀度指数呈低盖度(VFC<0.3)<中盖度(VFC0.3~0.6)<高盖度(VFC>0.6),优势度指数呈相反趋势。4)不同草地类型:丰富度指数、多样性指数,形成了“低-高-低”的单峰曲线,在高寒草原区较高,分别介于(0.659~2.897)和(5~26);高寒草甸均匀度指数较高(0.146~0.919)。【结论】盖度对草地物种多样性的影响较小,不同草地类型物种多样性主要受海拔影响,所以海拔是影响青海湖流域草地植被与物种多样性的主要因素。