Abstract
Abstract. Global change has been shown to alter the amount of above-ground litter inputs to soil greatly, which could cause substantial cascading effects on below-ground biogeochemical cycling. Despite extensive study, there is uncertainty about how changes in above-ground litter inputs affect soil carbon and nutrient turnover and transformation. Here, we conducted a meta-analysis on 70 litter-manipulation experiments in order to assess how changes in above-ground litter inputs alter soil physicochemical properties, carbon dynamics and nutrient cycles. Our results demonstrated that litter removal decreased soil respiration by 34%, microbial biomass carbon in the mineral soil by 39% and total carbon in the mineral soil by 10%, whereas litter addition increased them by 31, 26 and 10%, respectively. This suggests that greater litter inputs increase the soil carbon sink despite higher rates of carbon release and transformation. Total nitrogen and extractable inorganic nitrogen in the mineral soil decreased by 17 and 30%, respectively, under litter removal, but were not altered by litter addition. Overall, litter manipulation had a significant impact upon soil temperature and moisture, but not soil pH; litter inputs were more crucial in buffering soil temperature and moisture fluctuations in grassland than in forest. Compared to other ecosystems, tropical and subtropical forests were more sensitive to variation in litter inputs, as altered litter inputs affected the turnover and accumulation of soil carbon and nutrients more substantially over a shorter time period. Our study demonstrates that although the magnitude of responses differed greatly among ecosystems, the direction of the responses was very similar across different ecosystems. Interactions between plant productivity and below-ground biogeochemical cycling need to be taken into account to predict ecosystem responses to environmental change.
Highlights
Above-ground litterfall is one of the most important components of carbon and nutrient cycling, and the litter layer regulates soil microclimate by forming a buffering interface between the soil surface and the atmosphere (Sayer, 2006)
Litter removal increased the temperature of the mineral soil by 4 %, and litter addition decreased it by 3 % (Table 1)
The response of soil temperature to litter manipulation differed among ecosystems: in grasslands, soil temperature increased with litter removal and decreased with litter addition, whereas intropical forest www.biogeosciences.net/10/7423/2013/
Summary
Above-ground litterfall is one of the most important components of carbon and nutrient cycling, and the litter layer regulates soil microclimate by forming a buffering interface between the soil surface and the atmosphere (Sayer, 2006). Terrestrial ecosystems are undergoing simultaneous changes in climate and biogeochemical cycles, and those changes could affect plant net primary production (NPP) positively or negatively Changes such as elevated CO2 (King et al, 2005), nitrogen deposition (Xia and Wan, 2008) and temperature increases (Raich et al, 2006) were found to enhance plant productivity, whereas elevated O3 (Liu et al, 2005), drought (Zhao and Running, 2010) and acid deposition (Irving and Miller, 1981) generally decreased productivity. Xu et al.: Variability of above-ground litter inputs alters soil physicochemical and biological processes increase in above-ground litterfall after hurricanes or severe storms (Ostertag et al, 2003), or rapid loss of the litter layer after wildfires (Wardle et al, 2003)
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