Response of carbon dioxide emissions to sheep grazing and N application in an alpine grassland – Part 1: Effect of sheep grazing

[摘要] Previous work has failed to address fully the response of (autotrophic andheterotrophic) respiration to grazing in different ecosystems, particularlyin alpine grasslands outside the growing season. From 2010 to 2011 a fieldexperiment combined two methods (static closed chambers and a closed dynamicsoil CO₂ flux system) in alpine grasslands located in the TianshanMountains. We examined the effects of grazing regime on ecosystem respiration(R_e) both outside (NGS) and during (GS) the growing season anddetermined the pattern of R_e in relation to climate change. Therewas no significant change in CO₂ emissions under grazing. Heterotrophicrespiration (R_h) accounted for 78.5% of R_e withshort-term grazing exclusion and 93.2% of R_e with long-termgrazing exclusion. R_e, R_h and autotrophic respiration(R_a) fluxes outside the growing season were equivalent to12.9%, 14.1% and 11.4% of the respective CO₂ fluxesduring the growing season. In addition, our results indicate that soil watercontent played a critical role in R_a in the cold and aridenvironment. Both R_h and R_e were sensitive to soiltemperature. Moreover, our results suggest that grazing exerted nosignificant effect on CO₂ emissions in these alpine grasslands.

[学科分类] 地球化学与岩石