The methane concentration profile from -1.5m depth in soil to 32m height in air was measured in alpine steppe lo-cated in the permafrost area. Methane concentrations showed widely variations both in air and in soil du...The methane concentration profile from -1.5m depth in soil to 32m height in air was measured in alpine steppe lo-cated in the permafrost area. Methane concentrations showed widely variations both in air and in soil during the study period. The mean concentrations in atmosphere were all higher than those in soil, and the highest methane concentration was found in air at the height of 16m with the lowest concentration occur-ring at the depth of 1.5m in soil. The variations of atmospheric methane concentrations did not show any clear pattern both temporally and spatially, although they exhibited a more steady-stable state than those in soil. During the seasonal variations, the methane concentrations at different depths in soil were sig-nificantly correlated (R2>0.6) with each other comparing to the weak correlations (R2<0.2) between the atmospheric concentra-tions at different heights. Mean methane concentrations in soil significantly decreased with depth. This was the compositive influence of the decreasing production rates and the increasing methane oxidation rates, which was caused by the descent soil moisture with depth. Although the methane concentrations at all depths varied widely during the growing season, they showed very distinct temporal variations in the non-growing season. It was indicated from the literatures that methane oxidation rates were positively correlated with soil temperature. The higher methane concentrations in soil during the winter were deter-mined by the lower methane oxidation rates with decreasing soil temperatures, whereas methane production rates had no reaction to the lower temperature. Relations between methane contribution and other environmental factors were not discussed in this paper for lacking of data, which impulse us to carry out further and more detailed studies in this unique area.展开更多
Permafrost degradation is prevalent on the Qinghai-Tibet Plateau.This may lead to changes in water and heat transition in soils and thus affect the structure and function of ecosystems.In this paper,using the measured...Permafrost degradation is prevalent on the Qinghai-Tibet Plateau.This may lead to changes in water and heat transition in soils and thus affect the structure and function of ecosystems.In this paper,using the measured data of alpine steppe in Wudaoliang assessed the model performance in simulating soil freezing and thawing processes.Comparison of the simulated results by simultaneous heat and water(SHAW) model to the measured data showed that SHAW model performed satisfactorily.Based on analyzing the simulated and predicted results,two points were obtained:(1) freezing and thawing of the active layer proceeded both from the soil surface downward.Compared with the freezing process,the thawing process was slower.The freezing period persisted in the surface layer(4 cm depth) for about 5 months;(2) in the next 50 years,frozen period would be shorten about 20 days in the top 100 cm depth while the thawing would start earlier 40 days than present.Soil water storage in the 0-60 cm would decrease by 22% averagely,especially from June to August when the vegetation is at the dominating water consumed stage.Therefore,this kind of permafrost degradation as active layer freezing and thawing processes changes will reduce soil water content and thus influence those ecosystems above it.展开更多
基金funded by The National Basic Research Program (Grant No. G1998040800)Pre-studies project of National Basic Research Program (Grant No. 2005CCA05500)
文摘The methane concentration profile from -1.5m depth in soil to 32m height in air was measured in alpine steppe lo-cated in the permafrost area. Methane concentrations showed widely variations both in air and in soil during the study period. The mean concentrations in atmosphere were all higher than those in soil, and the highest methane concentration was found in air at the height of 16m with the lowest concentration occur-ring at the depth of 1.5m in soil. The variations of atmospheric methane concentrations did not show any clear pattern both temporally and spatially, although they exhibited a more steady-stable state than those in soil. During the seasonal variations, the methane concentrations at different depths in soil were sig-nificantly correlated (R2>0.6) with each other comparing to the weak correlations (R2<0.2) between the atmospheric concentra-tions at different heights. Mean methane concentrations in soil significantly decreased with depth. This was the compositive influence of the decreasing production rates and the increasing methane oxidation rates, which was caused by the descent soil moisture with depth. Although the methane concentrations at all depths varied widely during the growing season, they showed very distinct temporal variations in the non-growing season. It was indicated from the literatures that methane oxidation rates were positively correlated with soil temperature. The higher methane concentrations in soil during the winter were deter-mined by the lower methane oxidation rates with decreasing soil temperatures, whereas methane production rates had no reaction to the lower temperature. Relations between methane contribution and other environmental factors were not discussed in this paper for lacking of data, which impulse us to carry out further and more detailed studies in this unique area.
基金supported by the National Basic Research Program of China(Grant No.2005CB422005)the National Basic S&T Project of China(Grant No.2006FY110200)China Postdoctoral Science Foundation(Grant No.20090460506)
文摘Permafrost degradation is prevalent on the Qinghai-Tibet Plateau.This may lead to changes in water and heat transition in soils and thus affect the structure and function of ecosystems.In this paper,using the measured data of alpine steppe in Wudaoliang assessed the model performance in simulating soil freezing and thawing processes.Comparison of the simulated results by simultaneous heat and water(SHAW) model to the measured data showed that SHAW model performed satisfactorily.Based on analyzing the simulated and predicted results,two points were obtained:(1) freezing and thawing of the active layer proceeded both from the soil surface downward.Compared with the freezing process,the thawing process was slower.The freezing period persisted in the surface layer(4 cm depth) for about 5 months;(2) in the next 50 years,frozen period would be shorten about 20 days in the top 100 cm depth while the thawing would start earlier 40 days than present.Soil water storage in the 0-60 cm would decrease by 22% averagely,especially from June to August when the vegetation is at the dominating water consumed stage.Therefore,this kind of permafrost degradation as active layer freezing and thawing processes changes will reduce soil water content and thus influence those ecosystems above it.
