Abstract
Litter decomposition plays a critical role in regulating biogeochemical cycles in terrestrial ecosystems and is profoundly impacted by increasing atmospheric nitrogen (N) deposition. Here, a N manipulation experiment was conducted to explore the effects of N additions (0 kg N ha−1 yr−1, 20 kg N ha−1 yr−1 and 40 kg N ha−1 yr−1) on decay rates and nutrients release of two contrasting species, the evergreen and nutrient-poor Michelia wilsonii and the deciduous and nutrient-rich Camptotheca acuminata, using a litterbag approach at the western edge of the Sichuan Basin of China. The decay rate and the mineralization of N and phosphorus (P) was faster in nutrient-rich C. acuminata litter than in nutrient-poor M. wilsonii litter, regardless of N regimes. N additions tended to decrease the decay constant (k value) in M. wilsonii litter, but had no effect on C. acuminata litter. N additions had no significant effects on carbon (C) release of both litter types. N additions showed negative effects on N and P release of M. wilsonii litter, particularly in the late decomposition stage. Moreover, for C. acuminata litter, N additions did not affect N release, but retarded P release in the late stage. N additions did not affect the C:N ratio in both litter types. However, N additions—especially high-N addition treatments—tended to reduce C:P and N:P ratios in both species. The effect of N addition on N and P remaining was stronger in M. wilsonii litter than in C. acuminata litter. The results of this study indicate that N additions retarded the nutrients release of two foliar litters. Thus, rising N deposition might favor the retention of N and P via litter decomposition in this specific area experiencing significant N deposition.
Highlights
The decomposition of plant litter is a key determinant of carbon (C) and nutrient cycling in terrestrial ecosystems
This study found that the effect of N addition on litter N release differed between contrasting litters, with M. wilsonii being stronger than C. acuminata
This study investigated the litter decomposition and nutrients release of two contrasting litter types following gradient N additions in a subtropical forest with high N background
Summary
The decomposition of plant litter is a key determinant of carbon (C) and nutrient cycling in terrestrial ecosystems. It is a primary source of energy and nutrients for complex detritus-based food webs and constitutes an important ecosystem service by recycling nutrients, renewing soil fertility, and carbon sequestration [1]. Elevated N deposition increases soil N availability [6], which could further have complex and profound influences on litter decomposition in subtropical forests. As a global change driver, has great potential to affect plant litter decomposition in terrestrial ecosystems [7]. In N-deficient ecosystems, N addition generally stimulates the decomposition by increasing soil N availability or reducing the C:N litter ratios [11]. In N-sufficient sites, the added N often shows an inhibitory or neutral effect on litter decomposition and nutrients mineralization due to the saturation of soil
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