N and P fertilization reduced soil autotrophic and heterotrophic respiration in a young Cunninghamia lanceolata forest

Abstract

Understanding the response of heterotrophic (Rh) and autotrophic (Ra) components of soil respiration (Rs) to fertilization is important to evaluate the effects of management practices on soil carbon cycling in plantation forest ecosystems. Therefore, we investigated Ra and Rh using a trenching method in a young Cunninghamia lanceolata plantation, subjected to N and P fertilization in subtropical China. Soil CO2 efflux was measured from December 2013 to November 2015. Mean annual Rs, Ra, and Rh rates decreased on average by 18.6%, 23.6%, and 17.1% after fertilization. The contribution of Rh to Rs ranged from 70.9% to 76.7%. This contribution was greater in P-fertilized plots, suggesting that fertilization changed the contribution of Rh and Ra to Rs. The reduced rate of Rh induced by fertilization contributed on average 66.9% to the decrease in Rs rate. This contribution for Rh was higher in NP-fertilized plots than in other plots Based on a bivariate model, 51.2%–69.3% and 53.6%–66.7% of the variations in Rs and Rh among different treatments were explained by soil temperature and moisture. However, temperature sensitivity of Rs and Rh were not affected by fertilization. Ra and Rh were positively related to fine root biomass. Rh was also positively related to soil organic C, dissolved organic C, and microbial biomass C, but negatively related to soil mineral N content. Our results highlight the importance of fertilization on soil CO2 efflux and its significance to the estimation of forest C sink potential.