Soil and plant δ<sup>15</sup>N have a different response to experimental warming: A global meta-analysis

Abstract

Abstract. The 15N natural abundance composition (δ15N) in soils or plants is a useful tool to indicate the openness of ecosystem N cycling. This study was aimed to evaluate the influence of the global warming on soil and plant δ15N. We applied a global meta-analysis method to synthesize 79 and 76 paired observations for soil and plant δ15N from 20 published studies, respectively. Results showed that the mean effect sizes of the soil and plant δ15N under experimental warming were −0.524 (95 % CI: −0.987 to −0.162) and 0.189 (95 % CI: −0.210 to 0.569), respectively. This indicated that soil and plant δ15N had negative and positive responses to warming at the global scale, respectively. Experimental warming significantly (p < 0.05) decreased soil δ15N in Alkali soil, grassland/meadow, and under air warming, whereas it significantly (p < 0.05) increased soil δ15N in neutral soil. Plant δ15N significantly (p < 0.05) increased with increasing temperature in neutral soil and significantly (p < 0.05) decreased in alkali soil. Latitude did not affect the warming effects on both soil and plant δ15N. However, the warming effect on soil δ15N was positively controlled by the mean annual temperature, which is related to the fact that the higher temperature can strengthen the activity of soil microbes. The effect of warming on plant δ15N had weaker relationships with environmental variables compared with that on soil δ15N. This implied that soil δ15N tended to be more efficient in indicating the openness of global ecosystem N cycling than plant δ15N.