摘要
Aims Kobresia meadows,the dominant species of which differ in different habitats,cover a large area of alpine grassland on the QinghaiTibetan Plateau and act as potential CO_(2) sinks.Kobresia meadows with different dominant species may differ in carbon sink strength.We aimed to test the hypothesis and to clarify the differences in CO_(2) sink strength among three major Kobresia meadows on the plateau and the mechanisms underlying these differences.Methods We measured the net ecosystem exchange flux(NEE),ecosystem respiration flux(ER),aboveground biomass(AGB)and environmental variables in three Kobresia meadows,dominated by K.pygmaea,K.humilis,or K.tibetica,respectively,in Haibei,Qinghai.NEE and ER were measured by a closed-chamber method.Environmental variables,including photosynthetic photon flux density(PPFD),air and soil temperature and air and soil moisture,were monitored during the above flux measurements.Important findings The measured peak AGB increased with soil water content and was 365,402 and 434 g dry weight m2 for K.pygmaea,K.humilis and K.tibetica meadow,respectively.From the maximum ecosystem photosynthetic rate in relation to PPFD measured during the growing season,we estimated gross ecosystem photosynthetic potential(GEPmax)as 22.2,29.9 and 37.8 lmol CO_(2) m2 s1 for K.pygmaea,K.humilis and K.tibetica meadow,respectively.We estimated the respective gross primary production(GPP)values as 799,1063 and 1158 g C m^(-2) year^(-1) and ER as 722,914 and 1011 g C m^(-2) year^(-1).Average net ecosystem production(NEP)was estimated to be 76.9,149.4 and 147.6 g C m^(-2) year^(-1) in K.pygmaea,K.humilis and K.tibetica meadows,respectively.The results indicate that(i)the three meadows were CO_(2) sinks during the study period and(ii)Kobresia meadows dominated by different species can differ considerably in carbon sink strength even under the same climatic conditions,which suggests the importance of characterizing spatial heterogeneity of carbon dynamics in the future.
基金
Integrated Study for Terrestrial Carbon Management of Asia in the 21st Century Based on Scientific Advancements
Early Detection and Prediction of Climate Warming Based on the LongTerm Monitoring of Alpine Ecosystems on the Tibetan Plateau.
