Abstract. The nitrogen-15 (15N) natural abundance composition
(δ15N) in soils or plants is a useful tool to indicate the
openness of ecosystem N cycling. This study aimed to evaluate the
influence of the experimental warming on soil and plant δ15N.
We applied a global meta-analysis method to synthesize 79 and 76 paired
observations of 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 (confidence interval):
−0.987 to −0.162) and 0.189 (95 % CI: −0.210 to 0.569), respectively. This
indicated that soil δ15N had negative response to warming at
the global scale, where warming had no significant effect on plant δ15N. Experimental warming significantly (p<0.05) decreased
soil δ15N in Alkali and medium-textured soils, in
grassland/meadow, under air warming, for a 4–10-year warming period and for an
increase of >3 ∘C in temperature, whereas it significantly
(p<0.05) increased soil δ15N in neutral and
fine-textured soils and for an increase of 1.5–3 ∘C in temperature.
Plant δ15N significantly (p<0.05) increased with
increasing temperature in neutral and fine-textured soils 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 was more effective than plant δ15N in indicating the openness of global ecosystem N cycling.
Responses of Tundra Plants to Experimental Warming: Meta-Analysis of the International Tundra Experiment
