Changes in the sizes of precipitation events in the context of global climate change may have profound impacts on ecosystem productivity in arid and semiarid grasslands. However, we still have little knowledge about t...Changes in the sizes of precipitation events in the context of global climate change may have profound impacts on ecosystem productivity in arid and semiarid grasslands. However, we still have little knowledge about to what extent grassland productivity will respond to an individual precipitation event. In this study, we quantified the duration, the maximum, and the time-integrated amount of the response of daily gross primary productivity (GPP) to an individual precipitation event and their variations with different sizes of precipitation events in a typical temperate steppe in Inner Mongolia, China. Results showed that the duration of GPP-response (τ<sub>R</sub>) and the maximum absolute GPP-response (GPP<sub>max</sub>) increased linearly with the sizes of precipitation events (P<sub>es</sub>), driving a corresponding increase in time-integrated amount of the GPP-response (GPP<sub>total</sub>) because variations of GPPtotal were largely explained by τ<sub>R</sub> and GPP<sub>max</sub>. The relative contributions of these two parameters to GPP<sub>total</sub> were strongly P<sub>es</sub>-dependent. The GPP<sub>max</sub> contributed more to the variations of GPP<sub>total</sub> when P<sub>es</sub> was relatively small (<20 mm), whereas τ<sub>R</sub> was the main driver to the variations of GPP<sub>total</sub> when P<sub>es</sub> was relatively large. In addition, a threshold size of at least 5 mm of precipitation was required to induce a GPP-response for the temperate steppe in this study. Our work has important implications for the modeling community to obtain an advanced understanding of productivity-response of grassland ecosystems to altered precipitation regimes.展开更多
青藏高原是陆地碳循环研究中的热点地区。在全球气候变化背景下,其总初级生产力(gross primary production,GPP)在区域碳循环过程中发挥着重要作用。结合遥感数据使用模型模拟有助于了解青藏高原区域尺度上生态系统生产力的变化过程,以...青藏高原是陆地碳循环研究中的热点地区。在全球气候变化背景下,其总初级生产力(gross primary production,GPP)在区域碳循环过程中发挥着重要作用。结合遥感数据使用模型模拟有助于了解青藏高原区域尺度上生态系统生产力的变化过程,以及预测其未来的变化趋势。本研究使用6种常见的遥感GPP产品(GLASS、MODIS MOD17A2、FLUXCOM、VODCA2、改进的EC-LUE数据及VPM数据),结合涡度协方差通量观测数据(海北灌丛、海北湿地和当雄)进行验证后,对青藏高原2001—2015年生态系统GPP空间分布格局及时间变化趋势进行分析。结果表明:不同生态遥感产品得到的青藏高原年平均GPP、区域年均GPP时空分布格局与变化趋势存在较大差异,6套产品得到的2001—2015年变化趋势分别-0.77 g C·m^(-2)·a^(-1)(GLASS)、3.63 g C·m^(-2)·a^(-1)(MOD17A2)、-1.21 g C·m^(-2)·a^(-1)(FLUXCOM)、1.53 g C·m^(-2)·a^(-1)(VODCA2)、4.73 g C·m^(-2)·a^(-1)(VPM)和-0.81 g C·m^(-2)·a^(-1)(改进的EC-LUE);在空间分布上多年平均GPP总体呈现“东南高、西北低”的特点,区域差异较大;在青藏高原生态系统中,GLASS产品区域平均年GPP最高(827.78 Tg C·a^(-1)),MOD17A2产品最低(484.04 Tg C·a^(-1)),2001—2015年青藏高原生态系统GPP变化程度分布区域基本相同,东南部最剧烈,而西部最为稳定;经过站点数据验证,MOD17A2在8天尺度上结果相对更好,而FLUXCOM数据集在月尺度上结果相对更好,结合在区域尺度上的表现,MOD17A2数据集更加适用于青藏高原地区。展开更多
Investigating the spatial and temporal variance in productivity along natural precipitation gradients is one of the most efficient approaches to improve understanding of how ecosystems respond to climate change. In th...Investigating the spatial and temporal variance in productivity along natural precipitation gradients is one of the most efficient approaches to improve understanding of how ecosystems respond to climate change. In this paper, by using the natural precipitation gradient of the Inner Mongolian Plateau from east to west determined by relatively long-term observations, we analyzed the temporal and spatial dynamics of aboveground net primary productivity (ANPP) of the temperate grasslands covering this region. Across this grassland transect, ANPP increased exponentially with the increase of mean annual precipitation (MAP) (ANPP=24.47e0.005MAP, R2=0.48). Values for the three vegetation types desert steppe, typical steppe, and meadow steppe were: 60.86 gm-2a-1, 167.14 gm-2a-1 and 288.73 gm-2a-1 respectively. By contrast, temperature had negative effects on ANPP. The moisture index (K ), which takes into ac- count both precipitation and temperature could explain the spatial variance of ANPP better than MAP alone (ANPP=2020.34K1.24, R2=0.57). Temporally, we found that the inter-annual variation in ANPP (cal- culated as the coefficient of variation, CV) got greater with the increase of aridity. However, this trend was not correlated with the inter-annual variation of precipitation. For all of the three vegetation types, ANPP had greater inter-annual variation than annual precipitation (PPT). Their difference (ANPP CV/PPT CV) was greatest in desert steppe and least in meadow steppe. Our results suggest that in more arid regions, grasslands not only have lower productivity, but also higher inter-annual variation of production. Climate change may have significant effects on the productivity through changes in precipitation pattern, vegetation growth potential, and species diversity.展开更多
Soil organic carbon （SOC） stocks in terrestrial ecosystems vary considerably with land use types. Grassland, forest, and cropland coexist in the agro-pastoral ecotone of Inner Mongolia, China. Using SOC data compile...Soil organic carbon （SOC） stocks in terrestrial ecosystems vary considerably with land use types. Grassland, forest, and cropland coexist in the agro-pastoral ecotone of Inner Mongolia, China. Using SOC data compiled from literature and field investigations, this study compared SOC stocks and their vertical distributions among three types of ecosystems. The results indicate that grassland had the Largest SOC stock, which was 1.5- and 1.8-folds more than stocks in forest and cropland, respectively. Relative to the stock in 0-100 cm depth, grassland held more than 40% of its SOC stock in the upper 20 cm soil layer; forest and cropland both held over 30% of their respective SOC stocks in the upper 20 cm soil layer. SOC stocks in grazed grasslands were remarkably promoted after -〉20 years of grazing ex- clusion. Conservational cultivation substantially increased the SOC stocks in cropland, espe- cially in the 0-40 cm depth. Stand ages, tree species, and forest types did not have obvious impacts on forest SOC stocks in the study area likely due to the younger stand ages. Our study implies that soil carbon loss should be taken into account during the implementation of ecological projects, such as reclamation and afforestation, in the arid and semi-arid regions of China.展开更多
Vegetation biomass is an important component of terrestrial ecosystem carbon stocks. Grasslands are one of the most widespread biomes worldwideplaying an important role in global carbon cycling. Thereforestudying spat...Vegetation biomass is an important component of terrestrial ecosystem carbon stocks. Grasslands are one of the most widespread biomes worldwideplaying an important role in global carbon cycling. Thereforestudying spatial patterns of biomass and their correlations to environment in grasslands is fundamental to quantifying terrestrial carbon budgets. The Eurasian steppean important part of global grasslandsis the largest and relatively well preserved grassland in the world. In this studywe analyzed the spatial pattern of aboveground biomass（AGB）and correlations of AGB to its environment in the Eurasian steppe by meta-analysis. AGB data used in this study were derived from the harvesting method and were obtained from three data sources（literatureglobal NPP database at the Oak Ridge National Laboratory Distributed Active Archive Center（ORNL）some data provided by other researchers）. Our results demonstrated that：（1） as for the Eurasian steppe overallthe spatial variation in AGB exhibited significant horizontal and vertical zonality. In detailAGB showed an inverted parabola curve with the latitude and with the elevationwhile a parabola curve with the longitude. In additionthe spatial pattern of AGB had marked horizontal zonality in the Black Sea-Kazakhstan steppe subregion and the Mongolian Plateau steppe subregionwhile horizontal and vertical zonality in the Tibetan Plateau alpine steppe subregion.（2） Of the examined environmental variablesthe spatial variation of AGB was related to mean annual precipitation（MAP）mean annual temperature（MAT）mean annual solar radiation（MAR）soil Gravel contentsoil p H and soil organic content（SOC） at the depth of 0–30 cm. NeverthelessMAP dominated spatial patterns of AGB in the Eurasian steppe and its three subregions.（3） A Gaussian function was found between AGB and MAP in the Eurasian steppe overallwhich was primarily determined by unique patterns of grasslands and environment in the Tibetan Plateau. AGB was significantly positively related to MAP in the Black Sea-Kazakhstan steppe subregion（elevation 〈 3000 m）the Mongolian Plateau steppe subregion（elevation 〈 3000 m） and the surface（elevation ≥ 4800 m） of the Tibetan Plateau. Neverthelessthe spatial variation in AGB exhibited a Gaussian function curve with the increasing MAP in the east and southeast margins（elevation 〈 4800 m） of the Tibetan Plateau. This study provided more knowledge of spatial patterns of AGB and their environmental controls in grasslands than previous studies only conducted in local regions like the Inner Mongolian temperate grasslandthe Tibetan Plateau alpine grasslandetc.展开更多
Climate change is expected to introduce more water demand in the face of diminishing water supplies,intensifying the degree of aridity observed in terrestrial ecosystems in the 21st century.This study investigated spa...Climate change is expected to introduce more water demand in the face of diminishing water supplies,intensifying the degree of aridity observed in terrestrial ecosystems in the 21st century.This study investigated spatiotemporal variability within global aridity index(AI)values from 1970-2018.The results revealed an overall drying trend(0.0016 yr-1,p<0.01),with humid and semi-humid regions experiencing more significant drying than other regions,including those classified as arid or semi-arid.In addition,the Qinghai-Tibet Plateau has gotten wetter,largely due to the increases in precipitation(PPT)observed in that region.Global drying is driven primarily by decreasing and increasing PPT and potential evapotranspiration(PET),respectively.Decreases in PPT alone or increases in PET also drive global aridification,though to a lesser extent.PPT and increasing potential evapotranspiration(PET),with increasing PET alone or decreasing PPT alone.Slightly less than half of the world’s land area has exhibited a wetting trend,largely owing to increases in regional PPT.In some parts of the world,the combined effects of increased PPT and decreased PET drives wetting,with decreases in PET alone explaining wetting in others.These results indicate that,without consideration of other factors(e.g.,CO_(2)fertilization),aridity may continue to intensify,especially in humid regions.展开更多
基金jointly supported by the National Natural Science Foundation of China(31400425,31570437,41301043,31420103917)the National Key Project of Scientific and Technical Supporting Program(2013BAC03B03)+1 种基金the Funding for Talented Young Scientists of IGSNRR(2013RC203)the Social Foundation of Beijing Academy of Social Sciences(154005)
文摘Changes in the sizes of precipitation events in the context of global climate change may have profound impacts on ecosystem productivity in arid and semiarid grasslands. However, we still have little knowledge about to what extent grassland productivity will respond to an individual precipitation event. In this study, we quantified the duration, the maximum, and the time-integrated amount of the response of daily gross primary productivity (GPP) to an individual precipitation event and their variations with different sizes of precipitation events in a typical temperate steppe in Inner Mongolia, China. Results showed that the duration of GPP-response (τ<sub>R</sub>) and the maximum absolute GPP-response (GPP<sub>max</sub>) increased linearly with the sizes of precipitation events (P<sub>es</sub>), driving a corresponding increase in time-integrated amount of the GPP-response (GPP<sub>total</sub>) because variations of GPPtotal were largely explained by τ<sub>R</sub> and GPP<sub>max</sub>. The relative contributions of these two parameters to GPP<sub>total</sub> were strongly P<sub>es</sub>-dependent. The GPP<sub>max</sub> contributed more to the variations of GPP<sub>total</sub> when P<sub>es</sub> was relatively small (<20 mm), whereas τ<sub>R</sub> was the main driver to the variations of GPP<sub>total</sub> when P<sub>es</sub> was relatively large. In addition, a threshold size of at least 5 mm of precipitation was required to induce a GPP-response for the temperate steppe in this study. Our work has important implications for the modeling community to obtain an advanced understanding of productivity-response of grassland ecosystems to altered precipitation regimes.
文摘青藏高原是陆地碳循环研究中的热点地区。在全球气候变化背景下,其总初级生产力(gross primary production,GPP)在区域碳循环过程中发挥着重要作用。结合遥感数据使用模型模拟有助于了解青藏高原区域尺度上生态系统生产力的变化过程,以及预测其未来的变化趋势。本研究使用6种常见的遥感GPP产品(GLASS、MODIS MOD17A2、FLUXCOM、VODCA2、改进的EC-LUE数据及VPM数据),结合涡度协方差通量观测数据(海北灌丛、海北湿地和当雄)进行验证后,对青藏高原2001—2015年生态系统GPP空间分布格局及时间变化趋势进行分析。结果表明:不同生态遥感产品得到的青藏高原年平均GPP、区域年均GPP时空分布格局与变化趋势存在较大差异,6套产品得到的2001—2015年变化趋势分别-0.77 g C·m^(-2)·a^(-1)(GLASS)、3.63 g C·m^(-2)·a^(-1)(MOD17A2)、-1.21 g C·m^(-2)·a^(-1)(FLUXCOM)、1.53 g C·m^(-2)·a^(-1)(VODCA2)、4.73 g C·m^(-2)·a^(-1)(VPM)和-0.81 g C·m^(-2)·a^(-1)(改进的EC-LUE);在空间分布上多年平均GPP总体呈现“东南高、西北低”的特点,区域差异较大;在青藏高原生态系统中,GLASS产品区域平均年GPP最高(827.78 Tg C·a^(-1)),MOD17A2产品最低(484.04 Tg C·a^(-1)),2001—2015年青藏高原生态系统GPP变化程度分布区域基本相同,东南部最剧烈,而西部最为稳定;经过站点数据验证,MOD17A2在8天尺度上结果相对更好,而FLUXCOM数据集在月尺度上结果相对更好,结合在区域尺度上的表现,MOD17A2数据集更加适用于青藏高原地区。
基金Supported by the National Key Research and Development Program (Grant No. 2002CB412501)the National Natural Science Foundation of China (Grant No. 30590381)
文摘Investigating the spatial and temporal variance in productivity along natural precipitation gradients is one of the most efficient approaches to improve understanding of how ecosystems respond to climate change. In this paper, by using the natural precipitation gradient of the Inner Mongolian Plateau from east to west determined by relatively long-term observations, we analyzed the temporal and spatial dynamics of aboveground net primary productivity (ANPP) of the temperate grasslands covering this region. Across this grassland transect, ANPP increased exponentially with the increase of mean annual precipitation (MAP) (ANPP=24.47e0.005MAP, R2=0.48). Values for the three vegetation types desert steppe, typical steppe, and meadow steppe were: 60.86 gm-2a-1, 167.14 gm-2a-1 and 288.73 gm-2a-1 respectively. By contrast, temperature had negative effects on ANPP. The moisture index (K ), which takes into ac- count both precipitation and temperature could explain the spatial variance of ANPP better than MAP alone (ANPP=2020.34K1.24, R2=0.57). Temporally, we found that the inter-annual variation in ANPP (cal- culated as the coefficient of variation, CV) got greater with the increase of aridity. However, this trend was not correlated with the inter-annual variation of precipitation. For all of the three vegetation types, ANPP had greater inter-annual variation than annual precipitation (PPT). Their difference (ANPP CV/PPT CV) was greatest in desert steppe and least in meadow steppe. Our results suggest that in more arid regions, grasslands not only have lower productivity, but also higher inter-annual variation of production. Climate change may have significant effects on the productivity through changes in precipitation pattern, vegetation growth potential, and species diversity.
基金The Strategic Priority Research Program of CAS,No.XDA 05050201The Funding for Talented Young Scientists of IGSNRR,No.2013 RC203Youth Innovation Promotion Association of CAS,No.2015037
文摘Soil organic carbon （SOC） stocks in terrestrial ecosystems vary considerably with land use types. Grassland, forest, and cropland coexist in the agro-pastoral ecotone of Inner Mongolia, China. Using SOC data compiled from literature and field investigations, this study compared SOC stocks and their vertical distributions among three types of ecosystems. The results indicate that grassland had the Largest SOC stock, which was 1.5- and 1.8-folds more than stocks in forest and cropland, respectively. Relative to the stock in 0-100 cm depth, grassland held more than 40% of its SOC stock in the upper 20 cm soil layer; forest and cropland both held over 30% of their respective SOC stocks in the upper 20 cm soil layer. SOC stocks in grazed grasslands were remarkably promoted after -〉20 years of grazing ex- clusion. Conservational cultivation substantially increased the SOC stocks in cropland, espe- cially in the 0-40 cm depth. Stand ages, tree species, and forest types did not have obvious impacts on forest SOC stocks in the study area likely due to the younger stand ages. Our study implies that soil carbon loss should be taken into account during the implementation of ecological projects, such as reclamation and afforestation, in the arid and semi-arid regions of China.
基金The Chinese Academy of Sciences Strategic Priority Research Program,No.XDA05050602The Key Program of National Natural Science Foundation of China,No.31290221
文摘Vegetation biomass is an important component of terrestrial ecosystem carbon stocks. Grasslands are one of the most widespread biomes worldwideplaying an important role in global carbon cycling. Thereforestudying spatial patterns of biomass and their correlations to environment in grasslands is fundamental to quantifying terrestrial carbon budgets. The Eurasian steppean important part of global grasslandsis the largest and relatively well preserved grassland in the world. In this studywe analyzed the spatial pattern of aboveground biomass（AGB）and correlations of AGB to its environment in the Eurasian steppe by meta-analysis. AGB data used in this study were derived from the harvesting method and were obtained from three data sources（literatureglobal NPP database at the Oak Ridge National Laboratory Distributed Active Archive Center（ORNL）some data provided by other researchers）. Our results demonstrated that：（1） as for the Eurasian steppe overallthe spatial variation in AGB exhibited significant horizontal and vertical zonality. In detailAGB showed an inverted parabola curve with the latitude and with the elevationwhile a parabola curve with the longitude. In additionthe spatial pattern of AGB had marked horizontal zonality in the Black Sea-Kazakhstan steppe subregion and the Mongolian Plateau steppe subregionwhile horizontal and vertical zonality in the Tibetan Plateau alpine steppe subregion.（2） Of the examined environmental variablesthe spatial variation of AGB was related to mean annual precipitation（MAP）mean annual temperature（MAT）mean annual solar radiation（MAR）soil Gravel contentsoil p H and soil organic content（SOC） at the depth of 0–30 cm. NeverthelessMAP dominated spatial patterns of AGB in the Eurasian steppe and its three subregions.（3） A Gaussian function was found between AGB and MAP in the Eurasian steppe overallwhich was primarily determined by unique patterns of grasslands and environment in the Tibetan Plateau. AGB was significantly positively related to MAP in the Black Sea-Kazakhstan steppe subregion（elevation 〈 3000 m）the Mongolian Plateau steppe subregion（elevation 〈 3000 m） and the surface（elevation ≥ 4800 m） of the Tibetan Plateau. Neverthelessthe spatial variation in AGB exhibited a Gaussian function curve with the increasing MAP in the east and southeast margins（elevation 〈 4800 m） of the Tibetan Plateau. This study provided more knowledge of spatial patterns of AGB and their environmental controls in grasslands than previous studies only conducted in local regions like the Inner Mongolian temperate grasslandthe Tibetan Plateau alpine grasslandetc.
基金National Natural Science Foundation of China,No.31922053The Second Tibetan Plateau Scientific Expedition and Research Program,No.2019QZKK0405+1 种基金The Hainan University Start-up Fund,No.KYQD(ZR)21096The Key R&D Program of Hainan,No.ZDYF2022SHFZ042。
文摘Climate change is expected to introduce more water demand in the face of diminishing water supplies,intensifying the degree of aridity observed in terrestrial ecosystems in the 21st century.This study investigated spatiotemporal variability within global aridity index(AI)values from 1970-2018.The results revealed an overall drying trend(0.0016 yr-1,p<0.01),with humid and semi-humid regions experiencing more significant drying than other regions,including those classified as arid or semi-arid.In addition,the Qinghai-Tibet Plateau has gotten wetter,largely due to the increases in precipitation(PPT)observed in that region.Global drying is driven primarily by decreasing and increasing PPT and potential evapotranspiration(PET),respectively.Decreases in PPT alone or increases in PET also drive global aridification,though to a lesser extent.PPT and increasing potential evapotranspiration(PET),with increasing PET alone or decreasing PPT alone.Slightly less than half of the world’s land area has exhibited a wetting trend,largely owing to increases in regional PPT.In some parts of the world,the combined effects of increased PPT and decreased PET drives wetting,with decreases in PET alone explaining wetting in others.These results indicate that,without consideration of other factors(e.g.,CO_(2)fertilization),aridity may continue to intensify,especially in humid regions.
