了解植被物候与城市化之间的关系对于认识人类活动对生态系统的影响至关重要。基于呼和浩特市近20 a MODIS的两种植被指数数据,利用动态阈值法提取了植被物候,结合城市化指标,研究了2001—2020年呼和浩特市植被物候对城市化的响应。研...了解植被物候与城市化之间的关系对于认识人类活动对生态系统的影响至关重要。基于呼和浩特市近20 a MODIS的两种植被指数数据,利用动态阈值法提取了植被物候,结合城市化指标,研究了2001—2020年呼和浩特市植被物候对城市化的响应。研究表明:森林和灌木地返青期(Start of growing season,SOS)发生较早(平均值第132 d),但其枯黄期(End of growing season,EOS)也较早(第265 d)。SOS较晚的是耕地(第168 d),EOS较晚的是草地(第275 d),表明研究区木本植物SOS和EOS均早于草本植物。人造地表植被物候年际变化较大,在SOS和EOS的物候变化率分别为每10 a提前4.1 d和推迟0.7 d。此外,以人造地表比率和城乡梯度信息(即从城市核心到周边农村地区的同心环)为城市化指标,探讨了呼和浩特市中心城区植被物候对城市化的响应。研究发现SOS随人造地表比率上升而提前,EOS则出现相反的趋势。从城乡梯度上看,在特定范围内,远离城市中心SOS波动上升,即距城市中心越远植被SOS越晚,而EOS逐渐下降,即距城市中心越远植被EOS越早。总之,不同的城市化指标显示了植被物候对城市化的非线性响应。展开更多
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 evapotr...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 k Pa 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.展开更多
Climate change is manifesting rapidly in the form of fires,droughts,floods,resource scarcity,and species loss,and remains a global risk.Owing to the disaster risk management,there is a need to determine the Dead Fuel ...Climate change is manifesting rapidly in the form of fires,droughts,floods,resource scarcity,and species loss,and remains a global risk.Owing to the disaster risk management,there is a need to determine the Dead Fuel Index(DFI)threshold of the fire occurrence area and analyze the spatio-temporal variation of DFI to apply prevention measures efficiently and facilitate sustainable fire risk management.This study used the MODIS Burned Area Monthly L3(MCD64A1),Landsat Global Burned Area(BA)products,and MODIS Surface Reflectance 8-Day L3(MOD09A1)data from 2001 to 2020 to calculate the values of the DFI in the study area before the occurrence of fire.The results showed that:(1)The inversion of the meadow steppe DFI values in the fire area was distributed in the range of 14-26,and the fire rate was the highest in the range of 20-22.The inversion of the typical steppe DFI values in the fire area was distributed in the range of 12-26,and the fire rate was the highest in the range of 16-22.(2)Areas with high fire DFI values included Khalkhgol,Matad,Erdenetsagaan,Bayandun,Gurvanzagal,Dashbalbar in Mongolia,and scattered areas of the Greater Khingan Mountains(forest edge meadow steppe area),East and West Ujumqin Banner,and Xin Barag Right Banner.The highest fire probability of fire occurred during October and April.(3)The DFI values were sensitive to changes in altitude.The results of this study may provide useful information on surface energy balance,grassland carbon storage,soil moisture,grassland health,land desertification,and grazing in the study area,especially for fire risk management.展开更多
基金National Natural Science Foundation of China,No.42061070,No.61631011Science and Technology Fundamental Resources Survey Special Sub-project,No.2017FY101301-4Fundamental Research Funds for the Inner Mongolia Normal University,No.2022JBBJ013。
文摘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 k Pa 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.
基金The International(Regional)Cooperation and Exchange Programs of National Natural Science Foundation of China,No.41961144019,No.4191101037The Inner Mongolia Natural Science Foundation,No.2021MS04016。
文摘Climate change is manifesting rapidly in the form of fires,droughts,floods,resource scarcity,and species loss,and remains a global risk.Owing to the disaster risk management,there is a need to determine the Dead Fuel Index(DFI)threshold of the fire occurrence area and analyze the spatio-temporal variation of DFI to apply prevention measures efficiently and facilitate sustainable fire risk management.This study used the MODIS Burned Area Monthly L3(MCD64A1),Landsat Global Burned Area(BA)products,and MODIS Surface Reflectance 8-Day L3(MOD09A1)data from 2001 to 2020 to calculate the values of the DFI in the study area before the occurrence of fire.The results showed that:(1)The inversion of the meadow steppe DFI values in the fire area was distributed in the range of 14-26,and the fire rate was the highest in the range of 20-22.The inversion of the typical steppe DFI values in the fire area was distributed in the range of 12-26,and the fire rate was the highest in the range of 16-22.(2)Areas with high fire DFI values included Khalkhgol,Matad,Erdenetsagaan,Bayandun,Gurvanzagal,Dashbalbar in Mongolia,and scattered areas of the Greater Khingan Mountains(forest edge meadow steppe area),East and West Ujumqin Banner,and Xin Barag Right Banner.The highest fire probability of fire occurred during October and April.(3)The DFI values were sensitive to changes in altitude.The results of this study may provide useful information on surface energy balance,grassland carbon storage,soil moisture,grassland health,land desertification,and grazing in the study area,especially for fire risk management.
