Abstract

In order to investigate the effects of N deposition on soil biochemistry in secondary forests, one N addition experiment was conducted in a secondary evergreen broad-leaved forest in the western edge of Sichuan Basin, with the highest level of background N deposition (about 95 kg N ha−1 yr−1) in China. Three N treatment levels (+0, +50, +150 kg N ha−1 yr−1) were monthly added to soil surface in this forest beginning in April 2013. Soil biochemistry and root biomass of the 0–10 cm soil horizon were measured from May 2014 to April 2015. Soil respiration was measured for two years (September 2013 to August 2015). It was showed that N additions were correlated to significantly lower soil pH, microbial biomass C (MBC) concentration, MBC/microbial biomass N (MBN) ratio, root biomass, and soil respiration rate, and significantly higher concentrations of ammonium (NH4+) and nitrate (NO3−). These results indicate that N additions had a significant effect on the size of soil microbial community. In addition, soil C storage may potentially increase due to the dropped soil C release under N addition.

Highlights

  • In order to investigate the effects of N deposition on soil biochemistry in secondary forests, one N addition experiment was conducted in a secondary evergreen broad-leaved forest in the western edge of Sichuan Basin, with the highest level of background N deposition in China

  • The net primary productivity (NPP) of most terrestrial ecosystems is often limited by N; N additions tend to increase NPP in these ecosystems[8]

  • A number of studies have reported that N additions significantly increase ecosystem NPP9–11, and aboveground biomass[12, 13]

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Summary

Introduction

In order to investigate the effects of N deposition on soil biochemistry in secondary forests, one N addition experiment was conducted in a secondary evergreen broad-leaved forest in the western edge of Sichuan Basin, with the highest level of background N deposition (about 95 kg N ha−1 yr−1) in China. Previous studies indicated that increased N deposition generally results in soil acidification[28, 29], and changes soil enzyme activity, microbial activity and nutrient cycling[26, 30, 31]. All of these effects are likely to affect soil C dynamics. It has been predicted that the largest increases in N deposition in the world will occur in this region over the few decades[3]

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