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Rapid positive response of young trees growth to warming reverses nitrogen loss from subtropical soil

Lyu, Maokui1; Chen, Shidong1; Zhang, Qiufang1; Yang, Zhijie1; Xie, Jinsheng1; Wang, Chao2; Wang, Xiaohong1; Liu, Xiaofei1; Xiong, Decheng1; Xu, Chao1; Lin, Weisheng1; Chen, Guangshui1; Chen, Yuehmin1; Yang, Yusheng1

Published Feb 01, 2024 on Dryad. https://doi.org/10.5061/dryad.g79cnp5xd

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Feb 01, 2024 version files 109.57 KB

Abstract

  1. Global warming is widely expected to alter nitrogen (N) cycling in terrestrial ecosystems by accelerating N transformations in soils. However, it is unclear how warming will affect plant–soil N cycling in subtropical ecosystems.
  2. Here, we measured the N transformations including net ammoniation, nitrification, nitrous oxide emissions, and nitrate in soil solution throughout the plant–soil continuum with two years of experimental soil warming (+5 °C) in a young subtropical Chinese fir mesocosm. Seasonal variations of soil and plant (foliage and root) N concentrations and isotopes (δ15N), foliar water use efficiency, and arbuscular mycorrhizal colonization rate were measured.
  3. Soil warming significantly increased net ammoniation and nitrification of the soil, together with the transient positive response observed in inorganic N of the soil. Warming increased nitrate N fluxes in soil solution and nitrous oxide emissions in the first year but not in the second year, suggesting N losses through leaching and gaseous in the initial period of warming. Warming primarily induced enrichment of 15N in foliage relative to the soil, which was attributed to the trade-offs of persistent increases in plant N uptake caused by enhanced tree growth and a decrease in N losses with continuous warming.
  4. Warming significantly increased arbuscular mycorrhizal colonization and foliar water use efficiency throughout the warming period. These results suggest that young trees’ growth and N uptake can rapidly acclimate to warming by mechanisms including increases in plant water use efficiency and mycorrhizal colonization.
  5. Our findings highlight that warming accelerates the plant–soil N cycle and promotes young trees’ growth and N uptake, which in turn reduces soil N lost from this subtropical ecosystem. Therefore, our study suggests that the competition for N between plants and microbes governs whether subtropical forests are opened or closed N cycle systems under climate warming. We highlight that young trees can still maintain their high productivity in facing future climate warming since warming can improve plant N uptake and reduce N loss from subtropical ecosystems.