Three-River Headwaters （TRH） region involved in this paper refers to the source region of the Changjiang （Yangtze） River, the Huanghe （Yellow） River and the Lancang River in China. Taking the TRH region of the Q...Three-River Headwaters （TRH） region involved in this paper refers to the source region of the Changjiang （Yangtze） River, the Huanghe （Yellow） River and the Lancang River in China. Taking the TRH region of the Qing- hai-Tibet Plateau as a case, the annual evapotranspiration （ET） model developed by Zhang et al. （2001） was applied to evaluate mean annual ET in the alpine area, and the response of annual ET to land use change was analyzed. The plant-available water coefficient （w） of Zhang＇s model was revised by using vegetation-temperature condition index （VTCI） before annual ET was calculated in alpine area. The future land use scenario, an input of ET model, was spa- tially simulated by using the conversion of land use and its effects at small regional extent （CLUE-S） to study the re- sponse of ET to land use change. Results show that the relative errors between the simulated ET and that calculated by using water balance equation were 3.81% and the index of agreement was 0.69. This indicates that Zhang＇s ET model based on revised plant-available water coefficient is a scientific and practical tool to estimate the annual ET in the al- pine area. The annual ET in 2000 in the study area was 221.2 ram, 11.6 mm more than that in 1980. Average annual ET decreased from southeast to northwest, but the change of annual ET between 1980 and 2000 increased from southeast to northwest. As a vast and sparsely populated area, the population in the TRH region was extremely unbalanced and land use change was concentrated in very small regions. Thus, land use change had little effect on total annual ET in the study area but a great impact on its spatial distribution, and the effect of land use change on ET decreased with in- creasing precipitation. ET was most sensitive to the interconversion between forest and unused land, and was least sen- sitive to the interconversion between cropland and low-covered grassland.展开更多
The contribution of climatic change and anthropogenic activities to vegetation productivity are not fully understood.In this study,we determined potential climate-driven gross primary production(GPPp)using a process-b...The contribution of climatic change and anthropogenic activities to vegetation productivity are not fully understood.In this study,we determined potential climate-driven gross primary production(GPPp)using a process-based terrestrial ecosystem model,and actual gross primary production(GPPa)using MODIS Approach in alpine grasslands on the Tibetan Plateau from 2000 to 2015.The GPPa was influenced by both climatic change and anthropogenic activities.Gross primary production caused by anthropogenic activities(GPPh)was calculated as the difference between GPPp and GPPa.Approximately 75.63%and 24.37%of the area percentages of GPPa showed increasing and decreasing trends,respectively.Climatic change and anthropogenic activities were dominant factors responsible for approximately 42.90%and 32.72%of the increasing area percentage of GPPa,respectively.In contrast,climatic change and anthropogenic activities were responsible for approximately 16.88%and 7.49%of the decreasing area percentages of GPPa,respectively.The absolute values of the change trends of GPPp and GPPh of meadows were greater than those of steppes.The GPPp change values were greater than those of GPPh at all elevations,whereas both GPPp and GPPh showed decreasing trends when elevations were greater than or equal to 5000 m,4600 m and 4800 m in meadows,steppes and all grasslands,respectively.Climatic change had stronger effects on the GPPa changes when elevations were lower than 5000 m,4600 m and 4800 m in meadows,steppes and all grasslands,respectively.In contrast,anthropogenic activities had stronger effects on the GPPa changes when elevations were greater than or equal to 5000 m,4600 m and 4800 m in meadows,steppes and all grasslands,respectively.Therefore,the causes of actual gross primary production changes varied with elevations,regions and grassland types,and grassland classification management should be considered on the Tibetan Plateau.展开更多
基金Under the auspices of Supporting Program of the 'Eleventh Five-year Plan' for Science and Technology Research of China (No. 2009BAC61B02)China Postdoctoral Science Foundation Funded Project (No. 20100470561)
文摘Three-River Headwaters （TRH） region involved in this paper refers to the source region of the Changjiang （Yangtze） River, the Huanghe （Yellow） River and the Lancang River in China. Taking the TRH region of the Qing- hai-Tibet Plateau as a case, the annual evapotranspiration （ET） model developed by Zhang et al. （2001） was applied to evaluate mean annual ET in the alpine area, and the response of annual ET to land use change was analyzed. The plant-available water coefficient （w） of Zhang＇s model was revised by using vegetation-temperature condition index （VTCI） before annual ET was calculated in alpine area. The future land use scenario, an input of ET model, was spa- tially simulated by using the conversion of land use and its effects at small regional extent （CLUE-S） to study the re- sponse of ET to land use change. Results show that the relative errors between the simulated ET and that calculated by using water balance equation were 3.81% and the index of agreement was 0.69. This indicates that Zhang＇s ET model based on revised plant-available water coefficient is a scientific and practical tool to estimate the annual ET in the al- pine area. The annual ET in 2000 in the study area was 221.2 ram, 11.6 mm more than that in 1980. Average annual ET decreased from southeast to northwest, but the change of annual ET between 1980 and 2000 increased from southeast to northwest. As a vast and sparsely populated area, the population in the TRH region was extremely unbalanced and land use change was concentrated in very small regions. Thus, land use change had little effect on total annual ET in the study area but a great impact on its spatial distribution, and the effect of land use change on ET decreased with in- creasing precipitation. ET was most sensitive to the interconversion between forest and unused land, and was least sen- sitive to the interconversion between cropland and low-covered grassland.
基金National Natural Science Foundation of China(31600432)National Key Research Projects of China(2017YFA0604801,2016YFC0502005)+1 种基金Bingwei Outstanding Young Talents Program of Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences(2018RC202)Tibet Science and Technology Major Projects of the Pratacultural Industry(XZ201901NA03)
文摘The contribution of climatic change and anthropogenic activities to vegetation productivity are not fully understood.In this study,we determined potential climate-driven gross primary production(GPPp)using a process-based terrestrial ecosystem model,and actual gross primary production(GPPa)using MODIS Approach in alpine grasslands on the Tibetan Plateau from 2000 to 2015.The GPPa was influenced by both climatic change and anthropogenic activities.Gross primary production caused by anthropogenic activities(GPPh)was calculated as the difference between GPPp and GPPa.Approximately 75.63%and 24.37%of the area percentages of GPPa showed increasing and decreasing trends,respectively.Climatic change and anthropogenic activities were dominant factors responsible for approximately 42.90%and 32.72%of the increasing area percentage of GPPa,respectively.In contrast,climatic change and anthropogenic activities were responsible for approximately 16.88%and 7.49%of the decreasing area percentages of GPPa,respectively.The absolute values of the change trends of GPPp and GPPh of meadows were greater than those of steppes.The GPPp change values were greater than those of GPPh at all elevations,whereas both GPPp and GPPh showed decreasing trends when elevations were greater than or equal to 5000 m,4600 m and 4800 m in meadows,steppes and all grasslands,respectively.Climatic change had stronger effects on the GPPa changes when elevations were lower than 5000 m,4600 m and 4800 m in meadows,steppes and all grasslands,respectively.In contrast,anthropogenic activities had stronger effects on the GPPa changes when elevations were greater than or equal to 5000 m,4600 m and 4800 m in meadows,steppes and all grasslands,respectively.Therefore,the causes of actual gross primary production changes varied with elevations,regions and grassland types,and grassland classification management should be considered on the Tibetan Plateau.
