We investigated the moisture origin and contribution of different water sources to surface runoff entering the headwaters of the Heihe River basin on the basis of NECP/NCAR(National Centers for Environmental Predictio...We investigated the moisture origin and contribution of different water sources to surface runoff entering the headwaters of the Heihe River basin on the basis of NECP/NCAR(National Centers for Environmental Prediction/National Center for Atmospheric Research) re-analysis data and variations in the stable hydrogen and oxygen isotope ratios(δ D and δ 18O) of precipitation,spring,river,and melt water. The similar seasonality in precipitation δ 18O at different sites reveals the same moisture origin for water entering the headwaters of the Heihe River basin. The similarity in the seasonality of δ 18O and d-excess for precipitation at Yeniugou and Urumchi,which showed more positive δ 18O and lower d-excess values in summer and more negative δ 18O and higher d-excess values in winter,indicates a dominant effect of westerly air masses in summer and the integrated influence of westerly and polar air masses in winter. Higher d-excess values throughout the year for Yeniugou suggest that in arid inland areas of northwestern China,water is intensively recycled. Temporal changes in δ 18O,δ D,and d-excess reveal distinct contributions of different bodies of water to surface runoff. For example,there were similar trends for δ D,δ 18O,and d-excess of precipitation and river water from June to September,similar δ 18O trends for river and spring water from December to February,and similar trends for precipitation and runoff volumes. However,there were significant differences in δ 18O between melt water and river water in September. Our results show that the recharge of surface runoff by precipitation occurred mainly from June to mid-September,whereas the supply of surface runoff in winter was from base flow(as spring water) ,mostly with a lower runoff amount.展开更多
In the reconstruction of past climate using stable carbon isotope composition (δ13C) in tree ring,the responses of the stable carbon composition (δ13C) of multiple tree species to environmental factors must be known...In the reconstruction of past climate using stable carbon isotope composition (δ13C) in tree ring,the responses of the stable carbon composition (δ13C) of multiple tree species to environmental factors must be known detailedly. This study presented two δ13C series in annual tree rings for Chinese hem-lock (Tsuga chinensis Pritz) and alpine pine (Pinus densata Mast),and investigated the relationships between climatic parameters and stable carbon discrimination (△13C) series,and evaluated the poten-tial of climatic reconstruction using △13C in both species,in a temperate-moist region of Chuanxi Pla-teau,China. The raw δ13C series of the two species was inconsistent,which may be a result of different responses caused by tree's inherent physiological differences. After removing the low-frequency ef-fects of CO2 concentration,the high-frequency (year-to-year) inter-series correlation of △13C was strong,indicating that △13C of the two tree species were controlled by common environmental conditions. The △13C series of the species were most significantly correlated with temperature and moisture stress,but in different periods and intensity between the species. During the physiological year,the impacts of temperature and moisture stress on △13C occur earlier for Chinese hemlock (previous December to February for moisture stress and February to April for temperature,respectively) than for alpine pine (March to May for moisture stress and April to July for temperature,respectively). In addition,in temperate-moist regions,the control on △13C of single climatic parameter was not strongly dominant and the op-timal multiple regressions functions just explained the 38.5% variance of the total. Therefore,there is limited potential for using δ13C alone to identify clear,reliable climatic signals from two species.展开更多
The foliar C and N stable isotopic compositions(δ 13C and δ 15N) and the relationships between these compositions and environmental factors of C3 plants in the Ethiopia Rift Valley were investigated. There were thre...The foliar C and N stable isotopic compositions(δ 13C and δ 15N) and the relationships between these compositions and environmental factors of C3 plants in the Ethiopia Rift Valley were investigated. There were three distribution patterns for foliar δ 13C with mean values of ?26.7‰±0.4‰,?29.7‰± 0.6‰,and ?26.9‰± 1.2‰ in cold-moist,temperate-moist,and arid-hot environments,respectively. The δ 15N values ranged from ?1.4‰± 1.7‰ to 14.3‰± 0.1‰,with higher values under arid-hot conditions and the lowest values in plants growing at higher altitudes under cold-moist conditions. A strong negative relationship between mean annual precipitation and δ 15N explained more than half of the observed variation in the δ 15N values(r2 = 0.54,P < 0.001);a modest positive relationship was also found between δ 15N and tem-perature(r2 = 0.32,P < 0.01). A weakly positive relationship existed between δ 13C and temperature,and changes in δ 13C values with precipitation and altitude followed quadratic curves. This suggests a shift in the effects of water and heat conditions caused by altitude on carbon isotopic discrimination.展开更多
基金supported by the National Natural Science Foundation of China (91025016)the West Light Foundation of Western Doctors of the Chinese Academy of Sciences,the West Action Program of the Chinese Academy of Sciences (KZCX2-XB2-04-03)the China Postdoctoral Science Foundation (200801244 and 20070420135)
文摘We investigated the moisture origin and contribution of different water sources to surface runoff entering the headwaters of the Heihe River basin on the basis of NECP/NCAR(National Centers for Environmental Prediction/National Center for Atmospheric Research) re-analysis data and variations in the stable hydrogen and oxygen isotope ratios(δ D and δ 18O) of precipitation,spring,river,and melt water. The similar seasonality in precipitation δ 18O at different sites reveals the same moisture origin for water entering the headwaters of the Heihe River basin. The similarity in the seasonality of δ 18O and d-excess for precipitation at Yeniugou and Urumchi,which showed more positive δ 18O and lower d-excess values in summer and more negative δ 18O and higher d-excess values in winter,indicates a dominant effect of westerly air masses in summer and the integrated influence of westerly and polar air masses in winter. Higher d-excess values throughout the year for Yeniugou suggest that in arid inland areas of northwestern China,water is intensively recycled. Temporal changes in δ 18O,δ D,and d-excess reveal distinct contributions of different bodies of water to surface runoff. For example,there were similar trends for δ D,δ 18O,and d-excess of precipitation and river water from June to September,similar δ 18O trends for river and spring water from December to February,and similar trends for precipitation and runoff volumes. However,there were significant differences in δ 18O between melt water and river water in September. Our results show that the recharge of surface runoff by precipitation occurred mainly from June to mid-September,whereas the supply of surface runoff in winter was from base flow(as spring water) ,mostly with a lower runoff amount.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 90211018, 40501076 and 40371118)the International Partnership Project of the Chinese Academy of Sciences (Grant No. CXTD-Z2005-2)the Innovation Project of the Key Laboratory of Cryosphere and Environment, Cold and Arid Re-gions Environmental and Engineering Research Institute, Chinese Academy of Sciences
文摘In the reconstruction of past climate using stable carbon isotope composition (δ13C) in tree ring,the responses of the stable carbon composition (δ13C) of multiple tree species to environmental factors must be known detailedly. This study presented two δ13C series in annual tree rings for Chinese hem-lock (Tsuga chinensis Pritz) and alpine pine (Pinus densata Mast),and investigated the relationships between climatic parameters and stable carbon discrimination (△13C) series,and evaluated the poten-tial of climatic reconstruction using △13C in both species,in a temperate-moist region of Chuanxi Pla-teau,China. The raw δ13C series of the two species was inconsistent,which may be a result of different responses caused by tree's inherent physiological differences. After removing the low-frequency ef-fects of CO2 concentration,the high-frequency (year-to-year) inter-series correlation of △13C was strong,indicating that △13C of the two tree species were controlled by common environmental conditions. The △13C series of the species were most significantly correlated with temperature and moisture stress,but in different periods and intensity between the species. During the physiological year,the impacts of temperature and moisture stress on △13C occur earlier for Chinese hemlock (previous December to February for moisture stress and February to April for temperature,respectively) than for alpine pine (March to May for moisture stress and April to July for temperature,respectively). In addition,in temperate-moist regions,the control on △13C of single climatic parameter was not strongly dominant and the op-timal multiple regressions functions just explained the 38.5% variance of the total. Therefore,there is limited potential for using δ13C alone to identify clear,reliable climatic signals from two species.
基金Supported by the Import-Talents Program of the Cold and Arid Regions Environ-mental and Engineering Research Institute (Grant No. 2005104)the National Natural Science Foundation of China (Grant No. 40501076)the Chinese Science Expedition (DEEP) of the China Association for Scientific Expedition, and Inter-national Partnership Project of Chinese Academy Sciences (Grant No. CXTD-Z2005-2)
文摘The foliar C and N stable isotopic compositions(δ 13C and δ 15N) and the relationships between these compositions and environmental factors of C3 plants in the Ethiopia Rift Valley were investigated. There were three distribution patterns for foliar δ 13C with mean values of ?26.7‰±0.4‰,?29.7‰± 0.6‰,and ?26.9‰± 1.2‰ in cold-moist,temperate-moist,and arid-hot environments,respectively. The δ 15N values ranged from ?1.4‰± 1.7‰ to 14.3‰± 0.1‰,with higher values under arid-hot conditions and the lowest values in plants growing at higher altitudes under cold-moist conditions. A strong negative relationship between mean annual precipitation and δ 15N explained more than half of the observed variation in the δ 15N values(r2 = 0.54,P < 0.001);a modest positive relationship was also found between δ 15N and tem-perature(r2 = 0.32,P < 0.01). A weakly positive relationship existed between δ 13C and temperature,and changes in δ 13C values with precipitation and altitude followed quadratic curves. This suggests a shift in the effects of water and heat conditions caused by altitude on carbon isotopic discrimination.