Abstract
Abstract. Understanding how ecosystem carbon (C) and nitrogen (N) cycles respond to the variability of precipitation can help us assess the effects of global climate change on terrestrial ecosystem structure and function. We investigated the contributions of aboveground biomass, litter, root, soil and microbial communities to ecosystem C and N processes at 14 sites along a 1000 km precipitation gradient in native Leymus chinensis grasslands of northeastern China. The results show that aboveground biomass C and N increased gradually, while no significant regional trends in litter and root biomass were found with increasing mean annual precipitation (MAP) along the gradient. Soil respiration increased first and then decreased from the dry to mesic sites, which could be ascribed to the relative changes in temperature, soil fungal : bacterial biomass and N availability. Surprisingly, N mineralization varied only slightly along the gradient, likely due to the decreases of soil organic matter quality (i.e., C : N). Stepwise regression models indicated regional soil C and N content positively correlated with MAP and clay content. Overall, C and N sequestration increased 3.2- and 1.8-fold with increasing MAP in terms of C and N storage in aboveground biomass, roots, litter and soil. It was concluded from the current study that regional precipitation variability strongly influences ecosystem C and N dynamics. The ecosystem C and N sequestration are primarily modulated by annual precipitation and soil texture, while the C and N turnover are largely controlled by microbial community composition, temperature and soil quality in L. chinensis grasslands across the large-scale precipitation gradient.
Highlights
It is well known that precipitation has an important impact on ecosystem C and N cycles, especially in grasslands and water-limited regions, which cover ca. 45 % of the global terrestrial area (Saco et al, 2007; Zhou et al, 2009)
Previous studies have demonstrated that ecosystem aboveground primary production (Barrett et al, 2002; Huxman et al, 2004; Hsu et al, 2012), litter mass (Zhou et al, 2009), soil C and N dynamics (Porporato et al, 2003; Wang et al, 2008; Baumann et al, 2009) and trace gas flux (McCulley et al, 2005; Niu et al, 2009) are strongly influenced by mean annual precipitation (MAP) and water availability at local, regional and global scales
Recent research has indicated that the variability of precipitation is an important driver impacting ecosystem C and nutrient cycles directly through C sequestration, mineralization and uptake as well as controlling inputs and outputs of nutrients at global and regional extent (Austin and Sala, 2002)
Summary
It is well known that precipitation has an important impact on ecosystem C and N cycles, especially in grasslands and water-limited regions, which cover ca. 45 % of the global terrestrial area (Saco et al, 2007; Zhou et al, 2009). Previous studies have demonstrated that ecosystem aboveground primary production (Barrett et al, 2002; Huxman et al, 2004; Hsu et al, 2012), litter mass (Zhou et al, 2009), soil C and N dynamics (Porporato et al, 2003; Wang et al, 2008; Baumann et al, 2009) and trace gas flux (McCulley et al, 2005; Niu et al, 2009) are strongly influenced by mean annual precipitation (MAP) and water availability at local, regional and global scales. Root production is an important resource of organic matter, which represents 50–80 % of total biomass
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