Effects of nitrogen addition on litter decomposition and nutrient release in two tropical plantations with N2-fixing vs. non-N2-fixing tree species
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Background and Aims
Atmospheric nitrogen (N) deposition has elevated rapidly in tropical regions where N2-fixing tree species are widespread. However, the effect of N deposition on litter decomposition in forests with N2-fixing tree species remains unclear. We examined the effect of N addition on litter decomposition and nutrient release in two tropical plantations with Acacia auriculiformis (AA, N2-fixing) and Eucalyptus urophylla (EU, non-N2-fixing) in South China.
Three levels of N additions were conducted: control, medium-N (50 kg N ha−1 yr.−1) and high-N (100 kg N ha−1 yr.−1) in each plantation.
Initial decomposition rate (k a ) for the control plots was faster in the AA plantation than in the EU plantation, but later in decomposition, larger fraction of slowly decomposing litter (A) remained in the former. N addition increased the slow fraction (A), decreasing soil microbial biomass and reducing acid-unhydrolyzable residue (AUR) degradation in the AA plantation. In the EU plantation, however, N additions significantly increased initial decomposition rate (k a ) and soil N availability. Furthermore, N addition decreased litter carbon and N release (in the AA plantation), while litter phosphorus release also decreased in both plantations.
With ongoing N deposition in future, tropical plantations with N2-fixing tree species would potentially increase carbon accumulation and nutrient retention in forest floor by slowing litter decomposition.
KeywordsLitter decomposition Release of carbon Nitrogen and phosphorus Microbial biomass Nitrogen deposition Nitrogen-fixing tree species
This study was financially supported by the National Natural Science Foundation of China (NO: 41273143 and 41473112) and the National Key Basic Research 973 Program (2011CB403204). The authors wish to acknowledge Shengxing Fu, Ruifang Hu and Mozheng Li for their fieldwork.
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