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
Although biotic and abiotic factors have been confirmed to be critical factors that affect community dynamics,their interactive effects have yet to be fully considered in grassland degradation.Herein,we tested how soi...Although biotic and abiotic factors have been confirmed to be critical factors that affect community dynamics,their interactive effects have yet to be fully considered in grassland degradation.Herein,we tested how soil nutrients and microbes regulated plant-soil feedback(PSF)in a degraded alpine grassland.Our results indicated that soil total carbon(STC;from 17.66 to 12.55 g/kg)and total nitrogen(STN;from 3.16 to 2.74 g/kg)exhibited significant(P<0.05)decrease from non-degraded(ND)to severely degraded(SD).Despite higher nutrients in ND soil generating significantly(P<0.05)positive PSF(0.52)on monocots growth when the soil was sterilized,a high proportion of pathogens(36%)in ND non-sterilized soil resulted in a strong negative PSF on monocots.In contrast,the higher phenotypic plasticity of dicots coupled with a higher abundance of mutualists and saprophytes(70%)strongly promoted their survival and growth in SD with infertile soil.Our findings identified a novel mechanism that there was a functional group shift from monocots with higher vulnerability to soil pathogens in the ND fertile soil to dicots with higher dependence on nutritional mutualists in the degraded infertile soil.The emerging irreversible eco-evolutionary in PSF after degradation might cause a predicament for the restoration of degraded grassland.展开更多
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.
基金supported by the National Key R&D Program of China(2023YFF1304304)the National Natural Science Foundation of China(31870406 and 42301071)+1 种基金the China Postdoctoral Science Foundation(2023M743633)the Science and Technology Major Project of Tibetan Autonomous Region of China(XZ202201ZD0005G02).
文摘Although biotic and abiotic factors have been confirmed to be critical factors that affect community dynamics,their interactive effects have yet to be fully considered in grassland degradation.Herein,we tested how soil nutrients and microbes regulated plant-soil feedback(PSF)in a degraded alpine grassland.Our results indicated that soil total carbon(STC;from 17.66 to 12.55 g/kg)and total nitrogen(STN;from 3.16 to 2.74 g/kg)exhibited significant(P<0.05)decrease from non-degraded(ND)to severely degraded(SD).Despite higher nutrients in ND soil generating significantly(P<0.05)positive PSF(0.52)on monocots growth when the soil was sterilized,a high proportion of pathogens(36%)in ND non-sterilized soil resulted in a strong negative PSF on monocots.In contrast,the higher phenotypic plasticity of dicots coupled with a higher abundance of mutualists and saprophytes(70%)strongly promoted their survival and growth in SD with infertile soil.Our findings identified a novel mechanism that there was a functional group shift from monocots with higher vulnerability to soil pathogens in the ND fertile soil to dicots with higher dependence on nutritional mutualists in the degraded infertile soil.The emerging irreversible eco-evolutionary in PSF after degradation might cause a predicament for the restoration of degraded grassland.
