Using five well-replicated Qilian juniper (Sabina przewalskii Kom.) tree-ring width index se- ries, monthly normalized difference vegetation index (NDVI) of grassland, and climatic data from 1982 to 2001, the relation...Using five well-replicated Qilian juniper (Sabina przewalskii Kom.) tree-ring width index se- ries, monthly normalized difference vegetation index (NDVI) of grassland, and climatic data from 1982 to 2001, the relationships between tree-ring width index, NDVI of grassland, and climatic data were analyzed firstly. Then, the relationship between tree-ring width index and NDVI of grassland was explored. The re- sults showed that: (1) Temperature and precipitation in June influenced tree-ring width index and NDVI of grassland deeply in Delingha. (2) There were sig- nificant relationships between five tree-ring width index series (DLH1-DLH5) and monthly NDVI of grassland from June to September, with the most significant relationship being between tree-ring width index series and NDVI of grassland in August. (3) The PC1 (the first principal component derived from DLH1-DLH5 series) exhibited good agreement with monthly NDVI of grassland in the grass growth sea- son (from June to September) and the averaged NDVI in the growth season, which was attributed to their common responses to water-supply limit in Delingha. This study may allow an increase in studying the past dynamics of grassland in Delingha in that the variation of grassland NDVI during the last millennium has been reconstructed from PC1.展开更多
Oxygen stable isotope of atmospheric water vapor is widely used to study the modern process of cli- mate. Atmospheric water vapor samples were collected at Dlingha, northeast of Tibetan Plateau during the period from ...Oxygen stable isotope of atmospheric water vapor is widely used to study the modern process of cli- mate. Atmospheric water vapor samples were collected at Dlingha, northeast of Tibetan Plateau during the period from July 2005 to February 2006. The variation of δ18O and the relationships between δ18O and both the temperature and specific humidity are analyzed in this paper. Results show that the sea- sonal variation of δ18O of atmospheric water vapor at Delingha is remarkable with higher δ18O in summer and lower δ18O in winter. The temporal variation of vapor δ18O shows obvious fluctuations, with magnitude of over 37‰. The daily variation of the δ18O is highly correlated with air temperature. The relationship between δ18O and atmospheric water vapor content is complex. Study shows that δ18O of atmospheric water vapor is positively correlated with specific humidity in winter in seasonal scale and inversely correlated with specific humidity in summer rainy period. The δ18O values of at- mospheric water vapor are lower than those of precipitation at Delingha, and the average difference is 10.7‰. Variations of δ18O of atmospheric water vapor is also found to be affected by precipitation events, The model results show that the precipitation effect could have caused the vapor δ18O in the raining season to lower by 7% in average in July and August.展开更多
Delingha is located in the northeast margin of Qaidam Basin.Bayin River alluvial proluvial fan is the main aquifer of Delingha,in which groundwater generally flows from north to south.The hydrochemistry results showed...Delingha is located in the northeast margin of Qaidam Basin.Bayin River alluvial proluvial fan is the main aquifer of Delingha,in which groundwater generally flows from north to south.The hydrochemistry results showed that two different hydrochemical evolution paths formed along southeast and southwest directions,respectively.Cl-Na type groundwater was formed in front of Gahai Lake,and SO_(4)·HCO_(3)-Na·Ca type groundwater was formed in front of Keluke Lake.The results of deuterium(D)and 18O revealed that the groundwater mainly originated from the continuous accumulation of precipitation during geological history under cold and humid climate conditions.In addition,results of ^(14)C indicated that the groundwater age was more than 1140 years,implying relatively poor renewal capability of regional groundwater.Moreover,our numerical modeling results showed that the regional groundwater level will continue to rise under the warm and humid climate conditions.展开更多
基金This work Was supported by the Key Program of the National Natural Science Foundation of China （Grant No. 40331006） the Key Project of Knowledge Innovation of the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences （Grant No. CXI0G-E01-05 -02）.
文摘Using five well-replicated Qilian juniper (Sabina przewalskii Kom.) tree-ring width index se- ries, monthly normalized difference vegetation index (NDVI) of grassland, and climatic data from 1982 to 2001, the relationships between tree-ring width index, NDVI of grassland, and climatic data were analyzed firstly. Then, the relationship between tree-ring width index and NDVI of grassland was explored. The re- sults showed that: (1) Temperature and precipitation in June influenced tree-ring width index and NDVI of grassland deeply in Delingha. (2) There were sig- nificant relationships between five tree-ring width index series (DLH1-DLH5) and monthly NDVI of grassland from June to September, with the most significant relationship being between tree-ring width index series and NDVI of grassland in August. (3) The PC1 (the first principal component derived from DLH1-DLH5 series) exhibited good agreement with monthly NDVI of grassland in the grass growth sea- son (from June to September) and the averaged NDVI in the growth season, which was attributed to their common responses to water-supply limit in Delingha. This study may allow an increase in studying the past dynamics of grassland in Delingha in that the variation of grassland NDVI during the last millennium has been reconstructed from PC1.
基金the National Natural Science Foundation of China (Grant Nos. 40671043, 40571039 and 40771048) National Basic Research Program of China (Grant No. 2005CB422002)
文摘Oxygen stable isotope of atmospheric water vapor is widely used to study the modern process of cli- mate. Atmospheric water vapor samples were collected at Dlingha, northeast of Tibetan Plateau during the period from July 2005 to February 2006. The variation of δ18O and the relationships between δ18O and both the temperature and specific humidity are analyzed in this paper. Results show that the sea- sonal variation of δ18O of atmospheric water vapor at Delingha is remarkable with higher δ18O in summer and lower δ18O in winter. The temporal variation of vapor δ18O shows obvious fluctuations, with magnitude of over 37‰. The daily variation of the δ18O is highly correlated with air temperature. The relationship between δ18O and atmospheric water vapor content is complex. Study shows that δ18O of atmospheric water vapor is positively correlated with specific humidity in winter in seasonal scale and inversely correlated with specific humidity in summer rainy period. The δ18O values of at- mospheric water vapor are lower than those of precipitation at Delingha, and the average difference is 10.7‰. Variations of δ18O of atmospheric water vapor is also found to be affected by precipitation events, The model results show that the precipitation effect could have caused the vapor δ18O in the raining season to lower by 7% in average in July and August.
基金This work was supported by the National Natural Science Foundation of China(41672243)the China Geological Survey Program(DD20160291,DD20189270).
文摘Delingha is located in the northeast margin of Qaidam Basin.Bayin River alluvial proluvial fan is the main aquifer of Delingha,in which groundwater generally flows from north to south.The hydrochemistry results showed that two different hydrochemical evolution paths formed along southeast and southwest directions,respectively.Cl-Na type groundwater was formed in front of Gahai Lake,and SO_(4)·HCO_(3)-Na·Ca type groundwater was formed in front of Keluke Lake.The results of deuterium(D)and 18O revealed that the groundwater mainly originated from the continuous accumulation of precipitation during geological history under cold and humid climate conditions.In addition,results of ^(14)C indicated that the groundwater age was more than 1140 years,implying relatively poor renewal capability of regional groundwater.Moreover,our numerical modeling results showed that the regional groundwater level will continue to rise under the warm and humid climate conditions.
