The effects of warming on root exudation and associated soil N transformation depend on soil nutrient availability

Abstract

Although it has been realized that the maintenance of forest ecosystem structure and function and its response to environmental changes are closely related to root exudation, the effects of warming and soil nutrient availability on the root exudate carbon (C) inputs and soil nitrogen (N) transformation related microbial processes are still not well understood. In this study, a randomized block experiment with two temperatures (control and ambient + 3.5 °C) and two nitrogen treatments (control and 25 g N m−2 a−1) was conducted to collect the root exudates of P. tabulaeformis seedlings in situ and the microbial processes related to soil N transformation were simultaneously measured. We found that trees exposed to elevated temperature significantly increased their root exudate carbon input in unfertilized plots, and thus stimulating extracellular enzyme activity and enhancing N benefit. In contrast, the effect of warming on root exudate C input and associated soil N transformation greatly reduced after N addition, indicating that the effect of warming on root C cost and N benefit is regulated by the soil nutrient availability. Collectively, our results suggest that the variation in root C cost-N benefit induced by environmental changes is an important physiological regulatory mechanism for maintaining continuous forest growth. This study provides new insights into understanding nutrient maintenance mechanisms for forest productivity and functional stability under climate changes.