2000-2018年中亚五国水分利用效率对气候变化的响应

水分利用效率(Water use efficiency,WUE)是研究陆地碳水循环耦合的一种常用度量指标。基于MODIS的总初级生产力(GPP)和蒸散发(ET)数据,通过Slope趋势分析和敏感性分析等方法,研究了中亚WUE的时空变化规律及其对气候因子与干旱的动态响应。结果表明:(1)2000-2018年,中亚年均WUE随着生境湿润程度的增加而升高(生长期规律与此相反),其中湿地WUE最高(1.820±0.10 g C·mm^-1·m^-2),而灌丛WUE最低(1.330±0.18 g C·mm^-1·m^-2)。(2)中亚WUE呈略微下降趋势,每年下降速率为0.016 g C·mm^-1·m^-2,年均WUE的显著下降区域大于上升区域。WUE对年降水和年气温的敏感性均表现为正值区大于负值区且均存在阈值效应,降水敏感性阈值介于250~300 mm(低值点)和500~550 mm(高值点),温度阈值介于3~6℃(高值点)和9~12℃(低值点),且εNDV(I WUE对NDVI敏感性系数)与降水变化呈正相关关系,与气温变化呈负相关关系。(3)通过WUE与标准化降水指数(SPEI)的相关性比较,发现WUE受干旱程度影响由大到小依次为灌丛、作物、森林、草原和湿地,且不同植被类型下WUE随着干旱程度的增加而升高。     

气候要素及El Niño/La Niña事件对中国陆地NPP变化的影响

植被净初级生产力（NPP）是表征陆地生态系统碳循环的重要指标,也是人类社会赖以生存与发展的物质基础。基于遥感—过程耦合模型（GLOPEM-CEVSA模型）模拟的中国区域NPP数据和气象站点观测资料以及厄尔尼诺/拉尼娜（El Ni?o/La Ni?a）事件信息,利用GIS空间分析技术和数理统计方法研究了中国植被NPP的时空格局、动态变化以及气候要素和El Ni?o/La Ni?a气候事件对其影响。结果表明,1982-2011年,中国植被NPP总体上以5.66 gCm^-2(10a)^-1的趋势增长,空间上,植被NPP在中国西部和东北北部、东部地区增加,而在东北中部、华北平原、内蒙中东部、长三角和珠三角地区减少。中国江淮地区植被NPP的降低与日照时数的减少具有较好的对应关系,在华北地区和新疆北部,NPP的增减取决于降水量的增减。东北地区日照时数的增加和气温的升高则是NPP增加的主要原因。就全国整体而言,在El Ni?o年植被NPP增加的区域略多于减少的区域,在La Ni?a年NPP增加的区域则与减少的区域基本相等,日照时数是造成El Ni?o年与La Ni?a年植被NPP差异的主要气候因子。未来需要更加关注辐射、极端气候事件以及人为空气污染对中国不同地区植被的影响。     

中国陆地生态系统净初级生产力变化特征——基于过程模型和遥感模型的评估结果

净初级生产力（NPP）作为生态系统物质与能量循环的基础,是区域和全球尺度碳循环和碳收支研究的重要组成部分。研究区域和全球尺度的净初级生产力主要依靠模型手段实现,过程和遥感模型是目前广泛使用的两种模型形式。本文搜集并整理了基于过程模型和遥感模型对我国陆地生态系统净初级生产力的模拟结果,分析了中国陆地生态系统净初级生产力的时间变化及对未来气候变化的响应特征,旨在对其进行综合评价。结果表明,中国陆地生态系统NPP平均为（2.828±0.827）PgC.a-1。1982-1998年的年际变化特征上,NPP平均每年增加0.027 PgC,年增长率为1.07%,总体上呈现在波动中逐年上升的趋势。不同植被类型的单位面积NPP总体表现为常绿阔叶林显著高于其他植被类型,但不同研究结果间变化范围很大;落叶针叶林、常绿针叶林和落叶阔叶林相差较小;农作物低于阔叶林,但高于针叶林;草地和荒漠均位于低值区,但前者显著高于后者。不同植被类型的NPP总量总体表现为农作物和草地位居前两位,两者之和高达各植被类型NPP总量之和的58.34%;除灌丛和常绿针叶林外,其余植被类型均不足总量的10%。在未来气候情景下,中国陆地生态系统NPP总体上可能表现为先增加后减小的趋势。     

内蒙古草地NPP变化特征及其对气候变化敏感性的CENTURY模拟研究

气候变化及其对植被净初级生产力的影响是全球变化研究的核心内容之一。基于空间化的CENTURY生物过程模型,分析1981-2010年内蒙古草地净初级生产力（NPP）的时空演变规律及其对关键气候因子的敏感性特征。结果表明：近30年内蒙古草地大部分区域NPP呈下降态势但趋势并不显著,全区平均降速约为1.17 g C/m²·a;NPP年代际变化时空差异较大,1980s至1990s约69.65%的区域NPP下降,1990s至2000s NPP下降加剧,下降面积较前者扩大了17.50%;NPP对降水与温度的敏感性特征空间异质性较强,但总体上区域降水减少可能是近30年内蒙古草地NPP下降的主要因素,温度升高同样会导致草地NPP下降,但作用程度较小。     

东北地区植被分布全球气候变化区域响应

根据东北地区生态气候环境和生物地理规律对Holdridge生命地带分类系统进行修正,将东北地区植被分为寒温带湿润森林、寒温带潮湿森林、温带湿润森林、暖温带湿润森林、温带半湿润森林草甸草原、温带半湿润草甸草原、温带半干旱典型草原、暖温带半湿润草甸草原和暖温带半干旱典型草原等9 个生命地带并分析了其空间分布特征。运用大气环流模式分析东北地区由于温室气体增加导致的气候变化趋势。以此为基础评价东北地区植被分布的区域响应。全球气候变暖情景下,东北地区暖温带和温带范围明显扩大,而寒温带范围缩小甚至退出东北地区,植被分布界限显著北移;同时湿润区面积减少半湿润区和半干旱区扩大,导致森林面积缩小草原面积扩大。     

西藏NPP时空格局与气候因子的关系

根据2000-2012年1 km MOD17A3 NPP遥感数据和气温、降水等气象资料,在GIS支撑下,结合多种统计计算方法,对西藏NPP时空格局与气候因子的关系进行研究。结果表明:2000-2012年间西藏陆地植被的NPP为119.3～148.4 g·m^-2·a^-1,平均为135.2 g·m^-2·a^-1;近年来西藏NPP呈不显著上升趋势,NPP总体上由东南向西北逐渐变小。13年来西藏NPP在总体不变(面积占61.11%)的基础上略有增加(面积占10.7%);不同植被类型中阔叶林的NPP最大,为1 185.2～1 430.2 g·m^-2·a^-1,其次是混交林,为535.1～741.2 g·m^-2·a^-1,其后依次是稀树草原、针叶林、农用地、草地和灌丛;西藏NPP与气温、降水因子分别有较好的正、负相关性。所有植被类型都与年均气温呈正相关,其中草地的NPP与年均气温的相关系数达0.88,其次是针叶林为0.76,相关性最差为热带稀树草原0.13;与年降水量的相关性,除了热带稀树草原正相关(0.26),其余都负相关,草地、针叶林的相关系数分别为-0.79、-0.73。     

干旱对河西走廊植被净初级生产力的影响

干旱对生态系统碳循环具有重要影响,随着气候变暖,全球干旱事件频率不断上升,研究干旱对植被净初级生产力的影响具有重要意义.提高植被净初级生产力(NPP)的时间分辨率是认识干旱对其影响机制的重要途径.基于5天NDVI遥感数据,以河西走廊为研究区,利用CASA模型估算2010-2015年5天步长尺度的NPP,将5天降水为零定...     

黄河源区气候—植被—水文协同演变及成因辨析

全球变化下黄河源区水文过程的演变影响流域生态系统的水源涵养功能,流域植被改变也影响水循环。本文基于气候、植被信息和VIP分布式生态水文模型,开展黄河源区水碳循环要素变化的集成模拟,分析了气候—植被—水文要素的协同演变机制。结果表明,2000年以来黄河源区气候呈暖湿化趋势;植被绿度明显提高,2010—2019年比2000—2009年平均增加了4.5%;生长季延长了至少10 d;植被生产力（GPP）显著上升,倾向率为4.57 gC m^-2 a^-1;植被恢复措施对GPP变化的贡献约为23%,气候变化和大气CO₂升高的施肥效应的贡献为77%。源区植被蒸散量（ET）呈增加趋势,倾向率为2.54 mm a^-1,水分利用效率（WUE）亦提高,平均相对上升率为5.1% a^-1。GPP、ET和WUE年总量及其变化率在海拔4200 m以下随高度上升而减小,之后变化趋缓。源区植被绿度和径流系数与当年和前一年降水呈显著正相关,反映降水蓄存于植物根层土壤的遗留效应。蒸散增强在一定程度上有利于源区地表—大气之间的水分再循环,帮助缓解生态恢复引起的产水能力下降,促进降水—植被—径流之间的良性互馈关系的形成。揭示水文对气候变化和植被恢复的响应和互馈机制,可为生态恢复措施对源区水源涵养功能的影响及效应的定量评估提供科学依据。     

中国东南部植被NPP的时空格局变化及其与气候的关系研究

基于2001~2010年MOD17A3年均NPP数据和气象站点气温、降水资料,利用GIS空间分析技术和数理统计方法研究中国东南部植被NPP的时空格局、动态变化及与气候要素的关系。结果表明,中国东南部植被年均NPP总体上呈现从南到北、由东至西逐渐减少的分布,不同植被类型的NPP存在明显差异,以常绿阔叶林最高,落叶针叶林最低。2001~2010年间,植被NPP整体上略有减少。空间上植被NPP在南部地区明显减少,而在北部地区明显增加。植被NPP与降水和气温的相关性均表现出明显的地域差异。     

中国不同气候带各类型森林的生物量和净第一性生产力

根据<中国植被>的区划,将收集的全国984个样点的森林数据归并到5种气候带类型中,计算了各类型森林以及同一类型森林(分人工林和天然林)的生物量和净第一性生产力,还计算了不同气候带森林各器官的平均生物量和净第一性生产力.结果表明,从寒温带到热带各类型森林的生物量和净第一性生产力逐渐增加,天然林的生物量大于人工林生物量;除热带林外,人工林的净第一性生产力大于天然林净第一性生产力.     

基于MOD16监测陕西省地表蒸散变化

基于MOD16数据产品结合气象数据,统计分析了陕西省2000-2013年地表蒸散的时空分布特征,研究表明MOD16蒸散产品能够满足陕西省地表蒸散时空分布研究的要求,结果对陕西省水资源的有效利用具有重要的理论和实践意义。主要结论:(1) 2000-2013年蒸散(ET)、潜在蒸散(PET)年际波动不大,全省ET平均值在490 mm左右, PET平均值在1550 mm左右,年平均ET与PET的差距说明陕西省较为干旱缺水。全省ET、PET的年内变化都呈单峰分布趋势,两者变化存在差异, 6月两者差距最大,此时最为缺水。(2)陕西省不同区域蒸散有明显的空间分布差异,陕西南部水分较为充足,而在陕西北部较为缺水。陕西中西部区域干旱有所缓解,中东部区域干旱加重。(3)各功能区年平均ET与PET大小顺序正好相反,干旱程度顺序为防风治沙工程区>陕北退耕还林区>渭北退耕还林区>关中农业生产区>陕北天然林保护区>陕南退耕还林区>陕南天然林保护区。各功能区年内ET月平均变化差异明显,可分为三类,单峰型、波动型、双峰型。(4)蒸散的时空变化与气候特点,特别是水热条件的时空变化有很高的相关关系,而与植被的分布和生长状况也紧密相关。     

Spatiotemporal variations of water use efficiency and its driving factors in Inner Mongolia from 2001 to 2020

Water use efficiency (WUE) is an important variable to explore coupled relationships in carbon and water cycles. In this study, we first compared the spatial variations of annual gross primary productivity (GPP) and evapotranspiration (ET) using four GPP and ET products. Second, we selected the products closest to the flux towers data to estimate WUE. Finally, we quantitatively analyzed the impact of climate change and soil water content on WUE. The results showed that: (1) Four GPP and ET products provided good performance, with GOSIF-GPP and FLDAS-ET exhibiting a higher correlation and the smallest errors with the flux tower data. (2) The spatial pattern of WUE is consistent with that of GPP and ET, gradually decreasing from the northeast to the southwest. Higher WUE values appeared in the northeast forest ecosystem, and lower WUE values occurred in the western Gobi Desert, with a value of 0.28 gC m^?2 mm^?1. The GPP and ET products showed an increasing trend, while WUE showed a decreasing trend (55.15%) from 2001 to 2020. (3) The spatial relationship between WUE and driving factors reveal the variations in WUE of Inner Mongolia are mainly affected by soil moisture between 0 and 10 cm (SM0-10cm), vapor pressure deficit (VPD), and precipitation, respectively. (4) In arid regions, VPD and precipitation exhibit a major influence on WUE. An increase in VPD and precipitation has a negative and positive effect on WUE, with threshold values of approximately 0.36 kPa and 426 mm, respectively. (5) In humid regions, SM0-10cm, VPD, SM10-40cm, and SM40-100cm exert a significant impact on WUE, especially SM0-10cm, and weakens with increasing soil depths, these differences may be related to physiological structure and living characteristics of vegetation types in different climate regimes. Our results emphasize the importance of VPD and soil moisture in regional variability in WUE.     

内蒙古半干旱区蒸散估算和归因分析

蒸散(Evapotranspiration,ET)是生态系统水循环中的重要一环,决定了生态系统水分和热量传输。从区域尺度对蒸散及其蒸腾(Transpiration,T)和蒸发(Evaporation,E)组分进行量化,认识环境因素对其的影响机制,有助于合理利用、分配水资源,为研究气候变化对区域生态系统水文循环的影响提供参考。基于生态系统生产力模拟(Boreal ecosystem productivity simulator,BEPS)模型,验证模型在研究区域的适用性,量化1981—2018年内蒙古半干旱区的ET及其组分的变化情况,并对其进行归因分析。结果表明：经不同数据验证,BEPS模型计算结果能够精确反应研究区域ET及其组分的分布情况和变化趋势。1981—2018年研究区草地、农田和森林多年平均ET分别为278.22 mm、362.50 mm和308.81 mm。E、T和ET多年呈显著上升趋势,上升速率分别为0.42mm·a^-1、0.63 mm·a^-1和1.05 mm·a^-1。ET与T在全区域内空间分布格局相似,与E...     

Vegetation greenness modeling in response to climate change for Northeast Thailand

In Northeast Thailand, the climate change has resulted in erratic rainfall and tem- perature patterns. The region has experienced both periods of drought and seasonal floods with the increasing severity. This study investigated the seasonal variation of vegetation greenness based on the Normalized Difference Vegetation Index （NDVI） in major land cover types in the region. An assessment of the relationship between climate patterns and vegeta- tion conditions observed from NDVI was made. NDVI data were collected from year 2001 to 2009 using multi-temporal Terra MODIS Vegetation Indices Product （MOD13Q1）. NDVI pro- files were developed to measure vegetation dynamics and variation according to land cover types. Meteorological information, i.e. rainfall and temperature, for a 30 year time span from 1980 to 2009 was analyzed for their patterns. Furthermore, the data taken from the period of 2001-2009, were digitally encoded into GIS database and the spatial patterns of monthly rainfall and temperature maps were generated based on kriging technique. The results showed a decreasing trend in NDVI values for both deciduous and evergreen forests. The highest productivity and biomass were observed in dry evergreen forests and the lowest in paddy fields. Temperature was found to be increasing slightly from 1980 to 2009 while no significant trends in rainfall amounts were observed. In dry evergreen forest, NDVI was not correlated with rainfall but was significant negatively correlated with temperature. These re- sults indicated that the overall productivity in dry evergreen forest was affected by increasing temperatures. A vegetation greenness model was developed from correlations between NDVI and meteorological data using linear regression. The model could be used to observe the change in vegetation greenness and dynamics affected by temperature and rainfall.     

Vegetation change and its response to drought in Inner Mongolia of northern China from 1998 to 2013

Vegetation plays a significant role in global terrestrial ecosystems and in combating desertification. We analyzed vegetation change in Inner Mongolia of northern China using the Normalized Difference Vegetation Index(NDVI) from 1998 to 2013, which is an important composite of Chinese National Ecological Security Shelter. The correlation between vegetation growth and drought quantified using the Standardized Precipitation Evapotranspiration Index(SPEI) was also explored. Results show that vegetation in most of the study area has been rehabilitated to various degrees, especially in regions such as most of the Horqin Sandy Land, eastern Ordos Plateau, Hetao Plain, as well as the middle-northern Da Hinggan Ling Mountains. Vegetation improvement in spring was significant in most of the study area. Vegetation degradation was centrally distributed in Xilingol grassland close to the Sino-Mongolia border and abandoned croplands in Ulanqab Meng. Vegetation change trends and seasonal differences varied among different vegetation types. The biggest vegetation variation in the growing season was the belt-like distribution along those grasslands close to the precipitation isoline of 200 mm and the Sino-Mongolia border, but also variation in summer and autumn exist in obvious spatial differences between grasslands and forests. Drought largely influenced vegetation change of Inner Mongolia at 6-month scale or 12-month scale, except for forests of eastern Hunlun Buir Meng and deserts or gobi deserts of western Alxa Meng. Moreover,drought in the previous winter and early spring seasons had a lag effect on growing-season vegetation. Desert grassland was the most easily affected by drought in the study area. Anthropogenic activities have made great progress in improving local vegetation under the lasting drought background.     

近14a新疆南疆绿洲地区地表蒸散与干旱的时空变化特征研究

利用2001—2014年MOD16蒸散产品数据、MOD13植被[WTBX]NDVI[WTBZ]数据以及常规气象资料,基于植被指数、地表净辐射、气温优化改进混合型线性双源遥感蒸散模型,拟合地表蒸散分析实际蒸散（ET）、潜在蒸散（PET）时空动态变化特征,结合气象站实测蒸发皿数据验证MOD16数据在绿洲地区的适用性。进一步定义蒸散干旱指数（EDI）并计算△EDI进行研究区干旱特征分析,为大面积特殊地形蒸散估算研究和干旱监测提供一定依据。结果表明：（1） MOD16产品数据与研究区实测蒸发皿数据的相关性很好,通过0.01显著性检验,基于MOD16数据估算南疆绿洲地区蒸散量检验可行。（2） 2001—2014年均蒸散量总体变化不大,四季差异明显,ET与PET空间变化趋势相反;ET、PET年均差值较大,绿洲地区地表缺水情况严重。（3） EDI指数绿洲地区年均值总体偏大,△EDI对旱情的反映和干旱程度的判断比较可靠。     

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。     

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。     

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.     

沙地玉米水分利用效率日变化特征

以科尔沁沙地玉米农田生态系统为研究对象,利用涡度相关技术和便携式光合作用测定系统（LI-COR6400）同步观测玉米（郑单958）主要生育期（苗期、拔节期、抽穗期、灌浆期和成熟期）群体和叶片尺度瞬时CO₂交换及水汽交换速率,并分析其水分利用效率的日变化特征。结果表明：各生育期玉米群体尺度瞬时CO₂交换速率分别为-2.205、-26.113、-26.118、-8.201、-3.672 μmolCO₂·m^-2·s^-1,叶片尺度光合速率分别为27.57、59.55、24.38、22.03、20.09 μmolCO₂·m^-2·s^-1。各生育期群体水分利用效率（WUE_C）的日动态呈现“L”型,峰值出现在日出后（约06：00）,分别为0.025、0.039、0.088、0.058、0.191 gCO₂·g^-1H₂O,叶片尺度瞬时水分利用效率（WUE_L）的日动态呈“~”型,峰值出现在06：00—10：00,分别为0.029、0.041、0.017、0.019、0.024 gCO₂·g^-1H₂O。玉米各生育期群体及叶片尺度瞬时CO₂交换速率和水分利用效率均存在明显差异。