Effects of grazing on carbon exchange in a Leymus secalinus grassland ecosystem in the agro-pastoral ecotone of Northern Shanxi

doi:10.11686/cyxb2018724

Abstract

Abstract: Ecosystem net carbon exchange (NEE) is an important index to evaluate the carbon cycle, and is calculated from total primary productivity (GEP) and ecosystem respiration (ER). The aim of this study was to explore the effects of grazing on carbon exchange in the Leymus secalinus grassland ecosystem in the agro-pastoral ecotone of Northern Shanxi. Using the static chamber technique (LI-840a), we measured the daily and seasonal dynamics of NEE, ER, and GEP in the L. secalinus grassland under grazing during 2015 and 2016, and analyzed the correlation between these indexes and atmospheric temperature, soil temperature, soil moisture content, and aboveground and belowground biomass. The NEE, ER, and GEP showed clear daily and seasonal variations, which were the unimodal type. The values of NEE were lower in May, June, and September, but higher in July and August. The daily dynamics of NEE were mainly controlled by air temperature, while the seasonal changes were mainly controlled by soil temperature. Correlations between aboveground biomass as well as belowground biomass and NEE, ER, and GEP were extremely significant. Compared with fencing, grazing significantly decreased the NEE rate of the ecosystem in this grassland, but it did not affect the daily and seasonal trends in NEE. These results showed that, compared with enclosure, grazing can decrease the carbon exchange capacity and weaken the carbon sink function of a grassland ecosystem by reducing the proportion of photosynthetic matter in grassland vegetation.

Key words: grazing, Leymus secalinus grassland, net ecosystem carbon exchange, ecosystem respiration, gross ecosystem primary productivity

XING Peng-fei, LI Gang, CHEN Xiao-peng, LI De-ying, WANG Chang-hui, DONG Kuan-hu, ZHAO Xiang. Effects of grazing on carbon exchange in a Leymus secalinus grassland ecosystem in the agro-pastoral ecotone of Northern Shanxi[J]. Acta Prataculturae Sinica, 2019, 28(10): 1-11.

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