Institute of Wetland Research, Chinese Academy of Forestry, Beijing 100091, China; Beijing Key Laboratory of Wetland Services and Restoration, Beijing 100091, China; Sichuan Zoige Wetland Ecosystem Research Station, Tibetan Autonomous Prefecture of Aba, 624500, Sichuan, China.
Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Sci Total Environ. 2022 Feb 20;808:152140. doi: 10.1016/j.scitotenv.2021.152140. Epub 2021 Dec 3.
Alpine meadows on the Qinghai-Tibetan Plateau are sensitive to climate change. The precipitation regime in this region has undergone major changes, "repackaging" precipitation from more frequent, smaller events to less frequent, larger events. Nitrous oxide (NO) is an important indicator of responses to global change in alpine meadow ecosystems. However, little information is available describing the mechanisms driving the response of NO emissions to changes in the precipitation regime. In this study, a manipulative field experiment was conducted to investigate NO flux, soil properties, enzyme activity, and gene abundance in response to severe and moderate changes in precipitation regime over two years. Severe changes in precipitation regime led to a 12.6-fold increase in NO fluxes (0.0068 ± 0.0018 mg m h) from Zoige alpine meadows relative to natural conditions (0.0005 ± 0.0029 mg m h). In addition, severe changes in precipitation regime significantly suppressed the activities of leucine amino peptidase (LAP) and peroxidase (PEO), affected ecoenzymatic stoichiometry, and increased the abundances of gdhA, narI and nirK genes, which significantly promoted organic nitrogen (N) decomposition, denitrification, and anammox processes. The increase in abundance of these genes could be ascribed to changes in the abundance of several dominant bacterial taxa (i.e., Actinobacteria and Proteobacteria) as a result of the altered precipitation regime. Decreases in nitrate and soil moisture caused by severe changes in precipitation may exacerbate N limitation and water deficit, lead to a suppression of soil enzyme activity, and change the structure of microorganism community. The N cycle of the alpine meadow ecosystem may accelerate by increasing the abundance of key N functional genes. This would, in turn, lead to increased NO emission. This study provided insights into how precipitation regimes changes affect N cycling, and may also improve prediction of NO fluxes in response to changes in precipitation regime.
青藏高原上的高山草甸对气候变化敏感。该地区的降水格局发生了重大变化，“重新包装”了降水，使降水更频繁、更小，频率更低、更大。氧化亚氮（NO）是高山草甸生态系统对全球变化响应的一个重要指标。然而，关于驱动 NO 排放对降水格局变化响应的机制的信息很少。在这项研究中，进行了一项控制性野外实验，以研究在两年内严重和中度改变降水格局时 NO 通量、土壤性质、酶活性和基因丰度的变化。与自然条件相比，降水格局的剧烈变化导致若尔盖高山草甸的 NO 通量增加了 12.6 倍（0.0068±0.0018 mg m h）。此外，降水格局的剧烈变化显著抑制了亮氨酸氨基肽酶（LAP）和过氧化物酶（PEO）的活性，影响了生态酶化学计量，增加了 gdhA、narI 和 nirK 基因的丰度，这显著促进了有机氮（N）的分解、反硝化和厌氧氨氧化过程。这些基因丰度的增加可能归因于改变降水格局导致的几种优势细菌类群（即放线菌和变形菌）丰度的变化。强烈降水变化引起的硝酸盐和土壤水分减少可能加剧 N 限制和水分亏缺，导致土壤酶活性受到抑制，并改变微生物群落结构。通过增加关键 N 功能基因的丰度，高山草甸生态系统的 N 循环可能会加速。这反过来又会导致 NO 排放的增加。本研究深入了解了降水格局变化如何影响 N 循环，并可能改善对降水格局变化的 NO 通量的预测。
