Abstract
AbstractGlobal change‐induced litter decomposition strongly affects the carbon (C) and nitrogen (N) dynamics in grassland ecosystems. However, few studies show the interactive effects of global change factors on litter and root decomposition. We conducted a four‐year grassland field experiment to examine the quality and decomposition of litter and root in a three‐factorial experiment with elevated CO2, increased N deposition, and plant species richness. We found that elevated CO2 decreased the litter N content and root lignin content. N addition increased the root N content and decreased the litter lignin content. Increasing plant richness decreased the N and lignin contents in litter and root. In contrast to the quality changes, elevated CO2 had no effect on decomposition of litter and root. N addition increased the C loss of the litter by 4.8%, but did not affect C and N loss in root. Increasing plant richness affected the C and N loss in litter and root. ANCOVAs showed that tissue quality and root biomass affected the C and N loss in litter and root, and soil C and N affected the N loss of litter and root. However, changes in tissue quality, biomass, and soil as covariates did not significantly change the effects of CO2, N, and plant richness on decomposition. The structural equation model showed that elevated CO2 indirectly decreased litter N loss and increased root N loss, while N addition indirectly increased the C and N loss in litter and root, via their effects on tissue quality. Increasing plant richness increased litter C and N loss, but indirectly decreased root C and N loss. N deposition can accelerate litter and root decomposition, thus modifying the limitation of elevated CO2 on soil N availability. Biodiversity loss greatly alters litter and root decomposition, potentially driving any changes in C and N cycling. Our study clearly demonstrates a relative certainty of a predicted increase in the C loss and N release in litter and root decomposition with increased N deposition, whereas the effects of elevated CO2 and plant diversity changes on decomposition strongly differ between litter and root in grassland ecosystems.
Highlights
Litter decomposition may accelerate or decelerate global climate changes, because changes in litter quantity and quality can change both the cycling rates and the pools of carbon (C) and nutrients within an ecosystem (Dijkstra et al 2004, Sierra et al 2011, van Groenigen et al 2014)
To develop an understanding of why ecosystems differ in their responses to elevated CO2, there is an increased need to examine how the litter decomposition and nutrient release were determined by the changes in litter quality, quantity, microclimate, and soil biota caused by elevated CO2
Tissue quality Our study clearly illustrates that elevated CO2, N addition, and increasing plant species richness cause the changes in both aboveground litter tissue quality and belowground root tissue quality
Summary
Litter decomposition may accelerate or decelerate global climate changes, because changes in litter quantity and quality can change both the cycling rates and the pools of carbon (C) and nutrients within an ecosystem (Dijkstra et al 2004, Sierra et al 2011, van Groenigen et al 2014). Global climate changes can strongly affect litter decomposition due to the changes in physical decomposition environment induced by temperature or precipitation and the indirect roles through their effects on productivity and litter quality (Zhang et al 2008, Boyero et al 2011). Many studies have shown that elevated CO2 stimulates net primary productivity (NPP) and increases litter mass (Reich et al 2001a, Cotrufo et al 2005) Such increase in litter mass can affect C and N release from litter decomposition (Kemp et al 1994). To develop an understanding of why ecosystems differ in their responses to elevated CO2, there is an increased need to examine how the litter decomposition and nutrient release were determined by the changes in litter quality, quantity, microclimate, and soil biota caused by elevated CO2
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