Changes in litter traits induced by vegetation restoration accelerate litter decomposition in Robinia pseudoacacia plantations

Abstract

The chemical traits of litter are among the most critical factors that affect its decomposition. During vegetation restoration of planted forests, increasing age of the planted species and succession of the understory species may lead to significant changes in litter traits. However, it is unclear how these changes occur and how they affect litter decomposition. Therefore, we studied the decomposition of litter from four Robinia pseudoacacia plantations in the Loess Plateau in China with stand ages of 10-43 years using an indoor simulation test. We measured changes in litter substrate quality and chemical diversity, structural properties of the litter microbial community, activity of litter enzymes, and mixed decomposition effects during vegetation restoration. Their relationships to changes in litter decomposition rate were analyzed using structural equation modeling. Improvements in substrate quality of forest litter induced by vegetation restoration drove changes in fungal community composition during late decomposition (day 358), which in turn increased the activity of lignindecomposing enzymes and ultimately accelerated litter decomposition. At the same time, decreases in the chemical diversity of forest litter induced by vegetation restoration reduced the diversity of litter fungi during middle and late decomposition (days 182 and 358). This caused significant negative mixed decomposition effects, thereby inhibiting litter decomposition. However, improvements in litter substrate quality dominated the changes in litter decomposition rate, and the decomposition rate of R. pseudoacacia plantation litter thus increased over the course of vegetation restoration.

Litter C and N losses at different decomposition stages of Robinia pseudoacacia: The weaker effects of soil enzyme activities compared with those of litter quality and the soil environment

“…Carbon and nitrogen losses from leaf litter increased during vegetation restoration, while those from root litter showed the opposite trend; the older stand ages (45 Y) had the lowest carbon and nitrogen losses, which agrees with our second hypothesis. A previous study demonstrated that the rate of decomposition of R. pseudoacacia plantation litter increased during the revegetation process (Zhang et al, 2021), similar to our results. Litter N and P contents increased with restoration duration (Supplementary Table S1), which may have been beneficial for rapidly growing microbes and accelerating carbon and nitrogen losses (Xiao et al, 2019), as the effect of restoration duration on litter decomposition was more pronounced during the early stage.…”

“…Enzyme activities significantly varied during the decomposition of leaf litter and fine roots (Table 3; Figure 5). Previous studies have demonstrated that enzyme activities mediate the litter decomposition process (Fu et al, 2021;Li et al, 2021;Zhang et al, 2021;Li et al, 2022). Enzyme activities often have a positive effect on litter decomposition at the local scale (Zhong et al, 2017;Zheng et al, 2021).…”

“…However, there are studies showing opposing evidence. One report indicated that improvements in litter substrate quality accelerated leaf litter decomposition rates with vegetation restoration (Zhang et al, 2021), while another showed that leaf litter decomposition is not affected by stand age (Li et al, 2020). The changing patterns and influencing factors of litter decomposition during vegetation restoration are diverse and complex.…”

Short-Term Vegetation Restoration Enhances the Complexity of Soil Fungal Network and Decreased the Complexity of Bacterial Network

“…Previous studies have found positive [62,63] or negative [47,64] effects of vegetation restoration on fungal diversity. For example, the decrease in plant diversity in the sown treatments was followed by a decline in the diversity of plant litter and root exudates; a reduction in the heterogeneity of resources may induce a reduction in the fungal diversity [10,64]. On the contrary, some studies have shown that vegetation restoration can improve fungal diversity by increasing the enzyme activities and soil nutrients [65][66][67].…”

Soil degradation regulates the effects of litter decomposition on soil microbial nutrient limitation: Evidence from soil enzymatic activity and stoichiometry

“…Litter decomposition plays an important role in nutrient cycling in terrestrial ecosystems (Wu et al, 2021;Zhao et al, 2021;Zhang et al, 2022). Different qualities of litter inputs change the nutrient contents of soil (e.g., C, N, P, etc.…”