Effects of Forest Restoration on Soil Carbon, Nitrogen, Phosphorus, and Their Stoichiometry in Hunan, Southern China

Chuanhong Xu,Xiangwen Deng,Wenhua Xiang,Shuai Ouyang,Mengmeng Gou,Xi Fang,Pifeng Lei,Liang Chen

doi:10.3390/su10061874

Abstract

Forest restoration affects nutrient cycling in terrestrial ecosystems. However, the dynamics of carbon (C), nitrogen (N), and phosphorous (P), and their stoichiometry (C:N:P ratio) in the soil during forest restoration are poorly understood in subtropical areas. In the current study, we collected soil samples at three depths (0–10, 10–20, and 20–30 cm) at three restoration stages (early, intermediate, and late) in subtropical forests. Soil organic carbon (SOC), total nitrogen (N), and total phosphorous (P) concentrations were determined. Forest restoration significantly affected soil nutrient concentrations and stock (p < 0.05). SOC concentrations increased from 12.6 to 18.6 g/kg and N concentrations increased from 1.2 to 1.6 g/kg, while P decreased from 0.3 to 0.2 g/kg. A similar pattern of change was found for the nutrient stock as restoration proceeded. C:P and N:P ratios increased to a greater extent than that of C:N ratios during forest restoration, implying that subtropical forests might be characterized by P limitation over time. The slopes and intercepts for the linear regression relationships between SOC, N, and P concentrations were significantly different across the forest restoration stages (p < 0.05). This indicated that forest restoration significantly affects the coupled relationships among C-N, C-P, and N-P in subtropical forest soil. Our results add to the current body of knowledge about soil nutrient characteristics and have useful implications for sustainable forest management in subtropical areas.

Highlights

Forest restoration leads to changes in tree species composition with different traits
At any given restoration stage, the soil organic carbon (SOC) and N stock (Ns) concentrations and stocks decreased with soil depth, while soil P stock (Ps) concentrations and stock were lower at all three depths across the forest restoration stages (Figures 2C and 3C)
Our results showed that there were significant increases in the N:P ratio in subtropical forest soils during forest restoration, and our previous results showed that the N:P ratio becomes significantly higher in both fresh leaves and litterfall with forest restoration [14], which again indicates that the P limitation occurs at late restoration stages of subtropical forests

Summary

Introduction

Forest restoration leads to changes in tree species composition with different traits These shifts result in different amounts and quality of litter (leaves and fine roots) input, nutrient uptake by trees, and microclimates for litter decomposition, which, in turn, influence soil organic carbon (SOC), total nitrogen (N), and total phosphorous (P) dynamics and their stoichiometry (carbon (C):N:P ratio), affecting nutrient recycling [1,2]. N:P ratios have been shown to become significantly higher in both fresh leaves and litterfall from early- to late-restoration species, and late-restoration species are more likely to recycle P than N This implies that the nutrient limitation shifts from N at the early restoration stage (young stands) to P at the late restoration stage (old stands) [14,15,16,17]

Methods

Results

Discussion

Conclusion