Enhanced root exudation stimulates soil nitrogen transformations in a subalpine coniferous forest under experimental warming

作者：Huajun Yin, Yufei Li, Juan Xiao, Zhenfeng Xu, Xinyin Cheng, Qing Liu · 发表于：Global Change Biology · 年份：2013 · DOI：10.1111/gcb.12161 · 被引用次数：288 · 研究领域：Soil Carbon and Nitrogen Dynamics、Plant Water Relations and Carbon Dynamics、Peatlands and Wetlands Ecology

Despite the perceived importance of exudation to forest ecosystem function, few studies have attempted to examine the effects of elevated temperature and nutrition availability on the rates of root exudation and associated microbial processes. In this study, we performed an experiment in which in situ exudates were collected from Picea asperata seedlings that were transplanted in disturbed soils exposed to two levels of temperature (ambient temperature and infrared heater warming) and two nitrogen levels (unfertilized and 25 g N m(-2) a(-1) ). Here, we show that the trees exposed to an elevated temperature increased their exudation rates I (μg C g(-1) root biomass h(-1) ), II (μg C cm(-1) root length h(-1) ) and III (μg C cm(-2) root area h(-1) ) in the unfertilized plots. The altered morphological and physiological traits of the roots exposed to experimental warming could be responsible for this variation in root exudation. Moreover, these increases in root-derived C were positively correlated with the microbial release of extracellular enzymes involved in the breakdown of organic N (R(2) = 0.790; P = 0.038), which was coupled with stimulated microbial activity and accelerated N transformations in the unfertilized soils. In contrast, the trees exposed to both experimental warming and N fertilization did not show increased exudation rates or soil enzyme activity, indicating that the stimulatory effects of experimental warming on root exudation depend on soil fertility. Collec...