Climate change is now evident in the Qinghai-Tibet Plateau(QTP), with impacts on the alpine ecosystem, particularly on water and heat balance between the active layer and the atmosphere. Thus, we document the basic ch...Climate change is now evident in the Qinghai-Tibet Plateau(QTP), with impacts on the alpine ecosystem, particularly on water and heat balance between the active layer and the atmosphere. Thus, we document the basic characteristics of changes in the water and heat dynamics in response to experimental warming in a typical alpine swamp meadow ecosystem. Data sets under open top chambers(OTC) and the control manipulations were collected over a complete year. The results show that annual(2008) air temperatures of OTC-1 and OTC-2 were 6.7 °C and 3.5 °C warmer than the control. Rising temperature promotes plant growth and development. The freeze-thaw and isothermal days of OTCs appeared more frequently than the control, owing to comparably higher water and better vegetation conditions. OTCs soil moisture decreased with the decrease of soil depth; however, there was an obviously middle dry aquifer of the control, which is familiar in QTP. Moreover, experimental warming led to an increase in topsoil water content due to poorly drained swamp meadow ecosystem with higher organic matter content and thicker root horizons. The results of this study will have some contributions to alpine cold ecosystem water-heat process and water cycle under climate change.展开更多
Alpine swamp meadows on the Tibetan Plateau,with the highest soil organic carbon content across the globe,are extremely vulnerable to climate change.To accurately and continually quantify the gross primary production...Alpine swamp meadows on the Tibetan Plateau,with the highest soil organic carbon content across the globe,are extremely vulnerable to climate change.To accurately and continually quantify the gross primary production（GPP） is critical for understanding the dynamics of carbon cycles from site-scale to global scale.Eddy covariance technique（EC） provides the best approach to measure the site-specific carbon flux,while satellite-based models can estimate GPP from local,small scale sites to regional and global scales.However,the suitability of most satellite-based models for alpine swamp meadow is unknown.Here we tested the performance of four widely-used models,the MOD17 algorithm（MOD）,the vegetation photosynthesis model（VPM）,the photosynthetic capacity model（PCM）,and the alpine vegetation model（AVM）,in providing GPP estimations for a typical alpine swamp meadow as compared to the GPP estimations provided by EC-derived GPP.Our results indicated that all these models provided good descriptions of the intra-annual GPP patterns（R〉20.89,P〈0.0001）,but hardly agreed with the inter-annual GPP trends.VPM strongly underestimated the GPP of alpine swamp meadow,only accounting for 54.0% of GPP_EC.However,the other three satellite-based GPP models could serve as alternative tools for tower-based GPP observation.GPP estimated from AVM captured 94.5% of daily GPP_EC with the lowest average RMSE of 1.47 g C m^（-2）.PCM slightly overestimated GPP by 12.0% while MODR slightly underestimated by 8.1% GPP compared to the daily GPP_EC.Our results suggested that GPP estimations for this alpine swamp meadow using AVM were superior to GPP estimations using the other relatively complex models.展开更多
Aims The mature meadows(MMs)and the swamp meadows(SMs)are the two most important ecosystems in the eastern Tibetan Plateau,China.Besides their substantial differences in terms of soil water conditions and thereby the ...Aims The mature meadows(MMs)and the swamp meadows(SMs)are the two most important ecosystems in the eastern Tibetan Plateau,China.Besides their substantial differences in terms of soil water conditions and thereby the soil oxygen and nutrients,however,little is known about the differences in community composition,struc-ture,traits and productivity between these two meadows.We par-ticularly ask whether light availability mediated by physical structure heterogeneity is a key determinant of the difference in community composition and productivity between these two meadows.Methods We examined the community structure,composition,aboveground net primary productivity(ANPP),light availability in understory and the community-weighted means(CWMs)for leaf morphological and physiological traits in 12 random plots(5 m×5 m)for each of the studied habitats.Important findings The results showed that plant community in the MM had higher variation in both vertical and horizontal structure and thus had more light availability in the understory.The MM had higher spe-cies richness and greater ANPP than the SM.The CWMs of leaf morphological and physiological traits for species in the MM fea-tured a fast-growing strategy(i.e.higher height,leaf area and net photosynthesis rate and lower nitrogen:phosphorus ratio),in con-trast to those in the SM.We also found that there were significant correlations between the CWM of traits and the ANPP,indicating that some key traits in these habitats have linked to community productivity.Our study also suggests that the heterogeneity in the community structure,which affects light availability in the under-story,may play an important role in determining the community composition and productivity.In conclusion,our study revealed significant differences in community structure,composition and traits between the MM and the SM,and the light availability that related closely to community structure is the key factor to deter-mine the composition and productivity of the community of these two habitats.展开更多
基金funded by The Natural Science foundation of China (No. 40925002)The Natural Science foundation of Fujian Province (No. 2015J05114)
文摘Climate change is now evident in the Qinghai-Tibet Plateau(QTP), with impacts on the alpine ecosystem, particularly on water and heat balance between the active layer and the atmosphere. Thus, we document the basic characteristics of changes in the water and heat dynamics in response to experimental warming in a typical alpine swamp meadow ecosystem. Data sets under open top chambers(OTC) and the control manipulations were collected over a complete year. The results show that annual(2008) air temperatures of OTC-1 and OTC-2 were 6.7 °C and 3.5 °C warmer than the control. Rising temperature promotes plant growth and development. The freeze-thaw and isothermal days of OTCs appeared more frequently than the control, owing to comparably higher water and better vegetation conditions. OTCs soil moisture decreased with the decrease of soil depth; however, there was an obviously middle dry aquifer of the control, which is familiar in QTP. Moreover, experimental warming led to an increase in topsoil water content due to poorly drained swamp meadow ecosystem with higher organic matter content and thicker root horizons. The results of this study will have some contributions to alpine cold ecosystem water-heat process and water cycle under climate change.
基金National Natural Science Foundation of China(41571042,40603024)
文摘Alpine swamp meadows on the Tibetan Plateau,with the highest soil organic carbon content across the globe,are extremely vulnerable to climate change.To accurately and continually quantify the gross primary production（GPP） is critical for understanding the dynamics of carbon cycles from site-scale to global scale.Eddy covariance technique（EC） provides the best approach to measure the site-specific carbon flux,while satellite-based models can estimate GPP from local,small scale sites to regional and global scales.However,the suitability of most satellite-based models for alpine swamp meadow is unknown.Here we tested the performance of four widely-used models,the MOD17 algorithm（MOD）,the vegetation photosynthesis model（VPM）,the photosynthetic capacity model（PCM）,and the alpine vegetation model（AVM）,in providing GPP estimations for a typical alpine swamp meadow as compared to the GPP estimations provided by EC-derived GPP.Our results indicated that all these models provided good descriptions of the intra-annual GPP patterns（R〉20.89,P〈0.0001）,but hardly agreed with the inter-annual GPP trends.VPM strongly underestimated the GPP of alpine swamp meadow,only accounting for 54.0% of GPP_EC.However,the other three satellite-based GPP models could serve as alternative tools for tower-based GPP observation.GPP estimated from AVM captured 94.5% of daily GPP_EC with the lowest average RMSE of 1.47 g C m^（-2）.PCM slightly overestimated GPP by 12.0% while MODR slightly underestimated by 8.1% GPP compared to the daily GPP_EC.Our results suggested that GPP estimations for this alpine swamp meadow using AVM were superior to GPP estimations using the other relatively complex models.
基金This work was supported by National Natural Science Foundation of China(grant No.41171214).
文摘Aims The mature meadows(MMs)and the swamp meadows(SMs)are the two most important ecosystems in the eastern Tibetan Plateau,China.Besides their substantial differences in terms of soil water conditions and thereby the soil oxygen and nutrients,however,little is known about the differences in community composition,struc-ture,traits and productivity between these two meadows.We par-ticularly ask whether light availability mediated by physical structure heterogeneity is a key determinant of the difference in community composition and productivity between these two meadows.Methods We examined the community structure,composition,aboveground net primary productivity(ANPP),light availability in understory and the community-weighted means(CWMs)for leaf morphological and physiological traits in 12 random plots(5 m×5 m)for each of the studied habitats.Important findings The results showed that plant community in the MM had higher variation in both vertical and horizontal structure and thus had more light availability in the understory.The MM had higher spe-cies richness and greater ANPP than the SM.The CWMs of leaf morphological and physiological traits for species in the MM fea-tured a fast-growing strategy(i.e.higher height,leaf area and net photosynthesis rate and lower nitrogen:phosphorus ratio),in con-trast to those in the SM.We also found that there were significant correlations between the CWM of traits and the ANPP,indicating that some key traits in these habitats have linked to community productivity.Our study also suggests that the heterogeneity in the community structure,which affects light availability in the under-story,may play an important role in determining the community composition and productivity.In conclusion,our study revealed significant differences in community structure,composition and traits between the MM and the SM,and the light availability that related closely to community structure is the key factor to deter-mine the composition and productivity of the community of these two habitats.
