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
Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope （δD and δ^18O） values of different components such as plant xylem water, precipitation and rive...Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope （δD and δ^18O） values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species （Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum） in three typical ecosystems （forest, shrub and desert） were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. δ^18O values of N. tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all of the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was influenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater rose with an increase in precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environmental conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully understand responses of species on the Tibetan Plateau to changes in precipitation patterns, and to assess accurately changes of vegetation distribution in the future.展开更多
From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China （NSTEC）. B...From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China （NSTEC）. Based on these samples, we studied the geographical distribution patterns of vegetable water use efficiency （WUE） and nitrogen use efficiency （NUE）, and analyzed their relationship with environmental factors. The vegetable WUE and NUE were calculated through the measurement of foliar δ 13C and C/N of predominant species, respectively. The results showed： （1） vegetable WUE, ranging from 2.13 to 28.67 mg C g-1 H2O, increased linearly from south to north in the representative forest ecosystems along the NSTEC, while vegetable NUE showed an opposite trend, increasing from north to south, ranging from 12.92 to 29.60 g C g-1 N. （2） Vegetable WUE and NUE were dominantly driven by climate and significantly affected by soil nutrient factors. Based on multiple stepwise regression analysis, mean annual temperature, soil phosphorus concentration, and soil nitrogen concentration were responding for 75.5% of the variations of WUE （p0.001）. While, mean annual precipitation and soil phosphorus concentration could explain 65.7% of the change in vegetable NUE （p0.001）. Moreover, vegetable WUE and NUE would also be seriously influenced by atmospheric nitrogen deposition in nitrogen saturated ecosystems. （3） There was a significant trade-off relationship between vegetable WUE and NUE in the typical forest ecosystems along the NSTEC （p0.001）, indicating a balanced strategy for vegetation in resource utilization in natural forest ecosystems along the NSTEC. This study suggests that global change would impact the resource use efficiency of forest ecosystems. However, vegetation could adapt to those changes by increasing the use efficiency of shortage resource while decreasing the relatively ample one. But extreme impacts, such as heavy nitrogen deposition, would break this trade-off mech展开更多
We present a record on carbon stable isotopic composition (δ 13C), covering 75 through 10 thousands years ago (ka B.P.), from Hulu Cave, Nanjing. The overlapping δ 13C pro-files are very similar in pattern and range...We present a record on carbon stable isotopic composition (δ 13C), covering 75 through 10 thousands years ago (ka B.P.), from Hulu Cave, Nanjing. The overlapping δ 13C pro-files are very similar in pattern and range, indicating that they mainly record climatic signal. Dur-ing the last glacial-interglacial transition, the >6‰ change of δ 13C values implies different con-tributions of C3 vs. C4 type plants in soils. On millennial scale, however, the increased calcite δ 13C during the warm Dansgaard-Oeschger (DO) events suggests a decrease of dissolved bio-genic CO2 when water flux rate through soil is large. This correlation between heavier δ 13C and higher precipitation is consistent with our previous report on the samples’ stable oxygen isotope records (Wang et al., 2001). Comparison of coeval δ 13C and δ 18O of stalagmites indicates that kinetic fractionation of carbon isotope is closely related to growth rate of stalagmites. This study also shows that local vegetation changes may lag behind precipitation changes by ~700 years during the deglaciation.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the National Key Basic Research Program (NKBRP,2005CB422005)"Knowledge Innovation Engineering" of the Chinese Academy of Sciences (No. KZCX3-SW-339-04)
文摘Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope （δD and δ^18O） values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species （Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum） in three typical ecosystems （forest, shrub and desert） were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. δ^18O values of N. tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all of the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was influenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater rose with an increase in precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environmental conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully understand responses of species on the Tibetan Plateau to changes in precipitation patterns, and to assess accurately changes of vegetation distribution in the future.
基金National Natural Science Foundation of China No.30590381 No.31000211 National Basic Research Program of China No.2010CB833504
文摘From July 2008 to August 2008, 72 leaf samples from 22 species and 81 soil samples in the nine natural forest ecosystems were collected, from north to south along the North-South Transect of Eastern China （NSTEC）. Based on these samples, we studied the geographical distribution patterns of vegetable water use efficiency （WUE） and nitrogen use efficiency （NUE）, and analyzed their relationship with environmental factors. The vegetable WUE and NUE were calculated through the measurement of foliar δ 13C and C/N of predominant species, respectively. The results showed： （1） vegetable WUE, ranging from 2.13 to 28.67 mg C g-1 H2O, increased linearly from south to north in the representative forest ecosystems along the NSTEC, while vegetable NUE showed an opposite trend, increasing from north to south, ranging from 12.92 to 29.60 g C g-1 N. （2） Vegetable WUE and NUE were dominantly driven by climate and significantly affected by soil nutrient factors. Based on multiple stepwise regression analysis, mean annual temperature, soil phosphorus concentration, and soil nitrogen concentration were responding for 75.5% of the variations of WUE （p0.001）. While, mean annual precipitation and soil phosphorus concentration could explain 65.7% of the change in vegetable NUE （p0.001）. Moreover, vegetable WUE and NUE would also be seriously influenced by atmospheric nitrogen deposition in nitrogen saturated ecosystems. （3） There was a significant trade-off relationship between vegetable WUE and NUE in the typical forest ecosystems along the NSTEC （p0.001）, indicating a balanced strategy for vegetation in resource utilization in natural forest ecosystems along the NSTEC. This study suggests that global change would impact the resource use efficiency of forest ecosystems. However, vegetation could adapt to those changes by increasing the use efficiency of shortage resource while decreasing the relatively ample one. But extreme impacts, such as heavy nitrogen deposition, would break this trade-off mech
文摘We present a record on carbon stable isotopic composition (δ 13C), covering 75 through 10 thousands years ago (ka B.P.), from Hulu Cave, Nanjing. The overlapping δ 13C pro-files are very similar in pattern and range, indicating that they mainly record climatic signal. Dur-ing the last glacial-interglacial transition, the >6‰ change of δ 13C values implies different con-tributions of C3 vs. C4 type plants in soils. On millennial scale, however, the increased calcite δ 13C during the warm Dansgaard-Oeschger (DO) events suggests a decrease of dissolved bio-genic CO2 when water flux rate through soil is large. This correlation between heavier δ 13C and higher precipitation is consistent with our previous report on the samples’ stable oxygen isotope records (Wang et al., 2001). Comparison of coeval δ 13C and δ 18O of stalagmites indicates that kinetic fractionation of carbon isotope is closely related to growth rate of stalagmites. This study also shows that local vegetation changes may lag behind precipitation changes by ~700 years during the deglaciation.
