Aridity threshold for alpine soil nitrogen isotope signature and ecosystem nitrogen cycling

作者：Jinhua Mao, Junxiao Pan, Lei Song, Ruiyang Zhang, Jinsong Wang, Dashuan Tian, Quancheng Wang, Jiaqiang Liao, Jinlong Peng, Shuli Niu · 发表于：Global Change Biology · 年份：2024 · DOI：10.1111/gcb.17357 · 被引用次数：21 · 研究领域：Soil Carbon and Nitrogen Dynamics、Peatlands and Wetlands Ecology、Isotope Analysis in Ecology

Abstract Determination of tipping points in nitrogen (N) isotope (δ 15 N) natural abundance, especially soil δ 15 N, with increasing aridity, is critical for estimating N‐cycling dynamics and N limitation in terrestrial ecosystems. However, whether there are linear or nonlinear responses of soil δ 15 N to increases in aridity and if these responses correspond well with soil N cycling remains largely unknown. In this study, we investigated soil δ 15 N and soil N‐cycling characteristics in both topsoil and subsoil layers along a drought gradient across a 3000‐km transect of drylands on the Qinghai–Tibetan Plateau. We found that the effect of increasing aridity on soil δ 15 N values shifted from negative to positive with thresholds at aridity index (AI) = 0.27 and 0.29 for the topsoil and subsoil, respectively, although soil N pools and N transformation rates linearly decreased with increasing aridity in both soil layers. Furthermore, we identified markedly different correlations between soil δ 15 N and soil N‐cycling traits above and below the AI thresholds (0.27 and 0.29 for topsoil and subsoil, respectively). Specifically, in wetter regions, soil δ 15 N positively correlated with most soil N‐cycling traits, suggesting that high soil δ 15 N may result from the “openness” of soil N cycling. Conversely, in drier regions, soil δ 15 N showed insignificant relationships with soil N‐cycling traits and correlated well with factors, such as soil‐available phosphorus and foliage δ 15 N...