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
Our objectives are to examine the effects of hummock-depression spatial heterogeneity on plant communities and soil properties,and to understand the process of maintaining and adjusting microtopography-mediated hydrol...Our objectives are to examine the effects of hummock-depression spatial heterogeneity on plant communities and soil properties,and to understand the process of maintaining and adjusting microtopography-mediated hydrological inputs and their spatial fluctuations that produce obvious microhabitats.We set up 36 plots(1 m×1 m)and sampled 45 plant and 225 soil samples in flooded(FH)and non-flooded hummocks(NFH)and depressions of the marshy,and the surrounding non-wetland meadows as well as in the Yellow River Source Zone,west China.We evaluated whether the alpine marshy wetland has a fertile island effect by the comparison method.Our results show that hummock presence can increase the spatial heterogeneity of the microhabitat and promote the plant diversity and soil fertility of the Kobresia tibetica community.Plant height,coverage,above-ground biomass,species richness and diversity were significantly higher in the FH and NFH microhabitat than in the areas between hummocks and surrounding non-wetland meadows.Compared with broad alpine meadows,the hummock-depression complex provided a microhabitat favorable to the growth of Cyperaceae.In the 0-50 cm soil layer,the closer the soil layer was to the ground surface,the higher its soil organic carbon and total nitrogen contents.Thus,in deeper layers,the gap between soil nutrients in wetland hummock-depression microhabitat and in the surrounding alpine meadows becomes smaller.Hence,the wetland hummock-depression microhabitat formed a fertile island pattern.Therefore,these results contribute toward improving our understanding of ecosystem restoration in alpine marshy meadows.展开更多
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Thank the members of the research team for their kind support in the experiment,and thank the Science and Technology Department of Qinghai Provincial for the funding of the application basic project(2019-ZJ-7035)Discipline Innovation and Introducing Talents Program of Higher Education Institutions(the 111 Project,D18013)Changjiang Scholars and Innovation Team Development plan(IRT_17R62).
文摘Our objectives are to examine the effects of hummock-depression spatial heterogeneity on plant communities and soil properties,and to understand the process of maintaining and adjusting microtopography-mediated hydrological inputs and their spatial fluctuations that produce obvious microhabitats.We set up 36 plots(1 m×1 m)and sampled 45 plant and 225 soil samples in flooded(FH)and non-flooded hummocks(NFH)and depressions of the marshy,and the surrounding non-wetland meadows as well as in the Yellow River Source Zone,west China.We evaluated whether the alpine marshy wetland has a fertile island effect by the comparison method.Our results show that hummock presence can increase the spatial heterogeneity of the microhabitat and promote the plant diversity and soil fertility of the Kobresia tibetica community.Plant height,coverage,above-ground biomass,species richness and diversity were significantly higher in the FH and NFH microhabitat than in the areas between hummocks and surrounding non-wetland meadows.Compared with broad alpine meadows,the hummock-depression complex provided a microhabitat favorable to the growth of Cyperaceae.In the 0-50 cm soil layer,the closer the soil layer was to the ground surface,the higher its soil organic carbon and total nitrogen contents.Thus,in deeper layers,the gap between soil nutrients in wetland hummock-depression microhabitat and in the surrounding alpine meadows becomes smaller.Hence,the wetland hummock-depression microhabitat formed a fertile island pattern.Therefore,these results contribute toward improving our understanding of ecosystem restoration in alpine marshy meadows.
