Abstract
Plant species diversity affects carbon and nutrient cycling during litter decomposition, yet the generality of the direction of this effect and its magnitude remains uncertain. With a meta-analysis including 65 field studies across the Earth's major forest ecosystems, we show here that decomposition was faster when litter was composed of more than one species. These positive biodiversity effects were mostly driven by temperate forests but were more variable in other forests. Litter mixture effects emerged most strongly in early decomposition stages and were related to divergence in litter quality. Litter diversity also accelerated nitrogen, but not phosphorus release, potentially indicating a decoupling of nitrogen and phosphorus cycling and perhaps a shift in ecosystem nutrient limitation with changing biodiversity. Our findings demonstrate the importance of litter diversity effects for carbon and nutrient dynamics during decomposition, and show how these effects vary with litter traits, decomposer complexity and forest characteristics.
Highlights
Forests mediate biosphere-atmosphere carbon (C) dynamics via primary productivity (Huang et al, 2018; Liang et al, 2016) and decomposition (Handa et al, 2014; Hooper et al, 2012)
The average mass loss and N release measured at final harvest were higher in litter mixtures compared to those expected from single species litter, but there was no effect on P release (Figure 2)
Our quantitative synthesis of litter mixture effects on decomposition, encompassing most of the Earth’s forest biomes, suggests that mixing litter from different plant species generally accelerated litter mass loss and N release compared to what is predicted based on single species decomposition (Figures 2 and 3)
Summary
Forests mediate biosphere-atmosphere carbon (C) dynamics via primary productivity (Huang et al, 2018; Liang et al, 2016) and decomposition (Handa et al, 2014; Hooper et al, 2012). Litter mixtures can decompose at different rates than would be predicted from the rates of the individual component species, resulting in non-additive effects with either faster (synergistic effects) or slower (antagonistic effects) decomposition (Gartner and Cardon, 2004; Wardle et al, 1997). Synergistic effects may result from fungi-driven nitrogen (N) transfer among different litter types (Lummer et al, 2012; Schimel and Hattenschwiler, 2007) or through complementary resource use among microbial decomposers or detritivores (Gessner et al, 2010; Vos et al, 2013). Antagonistic effects may result from inhibiting or recalcitrant compounds (e.g. lignin and polyphenols) present in one litter type that negatively affect the decomposition of the whole mixture of litter (Hattenschwiler et al, 2005). Despite the accumulating number of case studies, it remains difficult to generalize these data beyond the specific context of the different studies, hindering a more general understanding of the importance of litter diversity for biogeochemical cycling in forests
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