Abstract
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.
Highlights
Nitrogen (N) is one of the most important nutrient elements for plant growth and the key limiting factor for vegetation productivity (McLay et al, 2001; Zhu et al, 2018; Lu et al, 2020)
The objectives of this study were to (i) detect the effect of experimental warming on the soil and plant δ15N based on a global meta-analysis of 20 studies and (ii) identify the main factors influencing the warming effect on the soil and plant δ15N
Peer-reviewed journal articles and dissertations related to soil and plant δ15N under experimental warming were searched using Web of Science and China National Knowledge Infrastructure (CNKI; http://www.cnki.net) last access: 31 March 2020 (Table 1)
Summary
Nitrogen (N) is one of the most important nutrient elements for plant growth and the key limiting factor for vegetation productivity (McLay et al, 2001; Zhu et al, 2018; Lu et al, 2020). If the available N in the soil is insufficient, it will damage and weaken the ecosystem service function, including the supply of primary material products, water conservation, climate regulation, etc. If the available N in the soil is over supplied, it will damage the structure and function of the ecosystem, resulting in a series of environmental problems such as soil acidification and imbalance of ecosystem nutrient (Schrijver et al, 2008). The intermediate products of the N cycling processes, such as nitrate nitrogen (NO−3 -N), nitrous oxide (N2O) and nitric oxide (NO), may cause eco-environmental pollution such as eutrophication of water bodies and aggravation of climate-related issues (Liao et al, 2019).
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