The hydrogen isotopic composition of plant leaf wax（δDwax） is used as an important tool for paleohydrologic reconstruction. However, the understanding of the relative importance of environmental and biological fact...The hydrogen isotopic composition of plant leaf wax（δDwax） is used as an important tool for paleohydrologic reconstruction. However, the understanding of the relative importance of environmental and biological factors in determining δDwax values still remains incomplete. To identify the effects of soil moisture and plant physiology on δDwax values in an arid ecosystem, and to explore the implication of these values for paleoclimatic reconstruction, we measured δD values of soil water（δDwater） and δDwax values in surface soils along two distance transects extending from the lakeshore to wetland to dryland around Lake Qinghai and Lake Gahai on the northeast Qinghai-Tibetan Plateau. The results showed that the δDwater values were negatively correlated with soil water content（SWC）（R^2=0.9166）, and ranged from –67‰ to –46‰ with changes in SWC from 6.2% to 42.1% in the arid areas of the Gangcha（GCh） and Gahai（GH） transects. This indicated that evaporative D-enrichment in soil water was sensitive to soil moisture in an arid ecosystem. Although the shift from grasses to shrubs with increasing aridity occurred in the arid area of the GH transect, the δDwax values in surface soils from the arid areas of the two transects still showed a negative correlation with SWC（R^2=0.6835）, which may be due to the controls of primary evaporative D-enrichment in the soil water and additional transpirational D-enrichment in the leaf water on the δDwaxvalues. Our preliminary research suggested that δDwax values can potentially be applied as a paleo-humidity indicator on the northeast Qinghai-Tibetan Plateau.展开更多
In the territory of the Voronezh region of Russia in ordinary middle loam chernozem the elevated concentration of endogenous hydrogen streams up to 0.65% at the depth of 100 - 120 cm was detected. This phenomenon is o...In the territory of the Voronezh region of Russia in ordinary middle loam chernozem the elevated concentration of endogenous hydrogen streams up to 0.65% at the depth of 100 - 120 cm was detected. This phenomenon is observed in the center of depressions. The soils differ in morphological, chemical and physical properties. The top humus horizon is markedly bleached comparing to the soil outside the depression: The lightness L readings increase for 16% - 30%. The soil acidity (up to pH 4.5 - 5.0) and organic carbon content are elevated comparing to the sample for reference. The proportion of fulvic acids increases on average thrice as compared with the soils outside the hydrogen fluids influence zone. Despite the high humus content the mechanical strength of aggregates decreases 3 - 4 times. Under conditions of hydrogen fluids, changes occur at the aggregate structural level in the direction of decreasing their mechanical strength. In the center of the depressions strength of aggregates is reduced by 2 - 3 times in comparison with the control. The opposite regularity was observed in the absence of hydrogen flows, where the strength of aggregates was 3 times higher than in comparison with the control.展开更多
基金supported by the National Basic Research Program of China (2013CB955901)the National Natural Science Foundation of China (41073018)
文摘The hydrogen isotopic composition of plant leaf wax（δDwax） is used as an important tool for paleohydrologic reconstruction. However, the understanding of the relative importance of environmental and biological factors in determining δDwax values still remains incomplete. To identify the effects of soil moisture and plant physiology on δDwax values in an arid ecosystem, and to explore the implication of these values for paleoclimatic reconstruction, we measured δD values of soil water（δDwater） and δDwax values in surface soils along two distance transects extending from the lakeshore to wetland to dryland around Lake Qinghai and Lake Gahai on the northeast Qinghai-Tibetan Plateau. The results showed that the δDwater values were negatively correlated with soil water content（SWC）（R^2=0.9166）, and ranged from –67‰ to –46‰ with changes in SWC from 6.2% to 42.1% in the arid areas of the Gangcha（GCh） and Gahai（GH） transects. This indicated that evaporative D-enrichment in soil water was sensitive to soil moisture in an arid ecosystem. Although the shift from grasses to shrubs with increasing aridity occurred in the arid area of the GH transect, the δDwax values in surface soils from the arid areas of the two transects still showed a negative correlation with SWC（R^2=0.6835）, which may be due to the controls of primary evaporative D-enrichment in the soil water and additional transpirational D-enrichment in the leaf water on the δDwaxvalues. Our preliminary research suggested that δDwax values can potentially be applied as a paleo-humidity indicator on the northeast Qinghai-Tibetan Plateau.
文摘In the territory of the Voronezh region of Russia in ordinary middle loam chernozem the elevated concentration of endogenous hydrogen streams up to 0.65% at the depth of 100 - 120 cm was detected. This phenomenon is observed in the center of depressions. The soils differ in morphological, chemical and physical properties. The top humus horizon is markedly bleached comparing to the soil outside the depression: The lightness L readings increase for 16% - 30%. The soil acidity (up to pH 4.5 - 5.0) and organic carbon content are elevated comparing to the sample for reference. The proportion of fulvic acids increases on average thrice as compared with the soils outside the hydrogen fluids influence zone. Despite the high humus content the mechanical strength of aggregates decreases 3 - 4 times. Under conditions of hydrogen fluids, changes occur at the aggregate structural level in the direction of decreasing their mechanical strength. In the center of the depressions strength of aggregates is reduced by 2 - 3 times in comparison with the control. The opposite regularity was observed in the absence of hydrogen flows, where the strength of aggregates was 3 times higher than in comparison with the control.
