Abstract
Litter decomposition is a fundamental path for nutrient cycling in a natural ecosystem. However, it remains unclear how species diversity, including richness and evenness, affects the decomposition dynamics in the context of grassland degradation. Using a litter bag technique, we investigated the litter-mixing effects of two coexisting dominant species (Leymus chinensis Lc and Phragmites australis Pa), as monocultures and mixtures with evenness (Lc:Pa) from M1 (30:70%), M2 (50:50%), and M3 (70:30%), on decomposition processes over time (60 and 365 days). The litter bags were placed on the soil surface along a degradation gradient [near pristine (NP), lightly degraded (LD), and highly degraded (HD)]. We found that 1) mass loss in mixture compositions was significantly and positively correlated with initial nitrogen (N) and cellulose contents; 2) litter mixing (richness and evenness) influenced decomposition dynamics individually and in interaction with the incubation days and the degradation gradients; 3) in a general linear model (GLM), nonadditive antagonistic effects were more prominent than additive or neutral effects in final litter and nutrients except for carbon (C); and 4) in nutrients (C, N, lignin) and C/N ratio, additive effects shifted to nonadditive with incubation time. We speculated that the occurrence of nonadditive positive or negative effects varied with litter and nutrients mass remaining in each degraded gradient under the mechanism of initial litter quality of monoculture species, soil properties of experimental sites, and incubation time. Our study has important implications for grassland improvement and protection by considering species biodiversity richness, as well as species evenness.
Highlights
Grasslands cover approximately 40% of earth’s land surface (Huang et al, 2012) and are of critical importance to the maintenance of biogeochemical cycles in grassland ecosystems (Rumpel et al, 2015)
Initial nutrient contents and carbon to nitrogen (C/N) ratio varied between monoculture litters, L. chinensis and P. australis
The C/N ratio was lower in L. chinensis than in P. australis
Summary
Grasslands cover approximately 40% of earth’s land surface (Huang et al, 2012) and are of critical importance to the maintenance of biogeochemical cycles in grassland ecosystems (Rumpel et al, 2015). Litter decomposition is a pivotal process that controls the balances of nutrient. Species Diversity Induces Idiosyncratic Effects cycling and energy flow (Zeng et al, 2018). Like other ecosystems with higher plant diversity, the litter on grassland floor naturally decomposes together (Mao and Zeng, 2012). Biodiversity in an area is dependent on two dimensions, species richness (number of plant species) and evenness (relative abundance of plant species) (Munoz et al, 2018). Previous studies have focused on the contribution of species richness (Ball et al, 2008; Lecerf et al, 2011; Wu et al, 2013; Mao et al, 2015), and the contribution of species evenness in the decomposition process remains understudied
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