School of Life Sciences and Biopharmaceutical Sciences, Shenyang Pharmaceutical University, Shenyang 110016, China.
Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
Ying Yong Sheng Tai Xue Bao. 2023 Jul;34(7):1834-1844. doi: 10.13287/j.1001-9332.202307.016.
Nitrogen deposition and summer precipitation in eastern Inner Mongolia are predicted to increase in recent decades. However, such increases in nitrogen inputs and precipitation may not be continuous under the future new patterns of global change, with the direction and magnitude of which may change or weaken. The legacy effects of nitrogen and water addition after cessation on ecosystems are still unclear. Based on a 13-year nitrogen and water addition experiment in temperate grassland of northern China, we examined the short-term (2 years) legacy effects of historical nitrogen and water addition on soil physicochemical properties and microbial properties after the cessation of nitrogen and water addition in the 14th year. The results showed that the positive effects of historical nitrogen addition on most of soil nutrient variables diminished after two years of cessation, including ammonium nitrogen, nitrate nitrogen, dissolved organic carbon and nitrogen, and Olsen-P concentrations. In contrast, there were legacy effects on soil microbial characteristics. For example, the historical nitrogen input of 15 g N·m·a reduced microbial biomass carbon, respiration, and alkaline phosphomonoesterase activity by 73.3%, 81.9%, and 70.3% respectively. It implied that microbial parameters restored slowly in comparison with soil nutrients, showing a hysteresis effect. Results of Pearson's correlation and redundancy analysis showed that the legacy effects of historical nitrogen addition on microbial parameters could be attributed to the negative effects of nitrogen addition on soil pH. Historical water addition showed significant legacy effects on soil pH, ammonium nitrogen, dissolved organic carbon and nitrogen, respiration, and soil enzyme activities, which significantly interacted with historical nitrogen addition. These results are of great significance to predict the changes in grassland ecosystem functions and services under the local environmental improvement conditions, and to reveal the restoration mechanism of degraded grassland.
近几十年来，预测内蒙古东部的氮沉降和夏季降水将会增加。然而，在未来全球变化的新模式下，氮素输入和降水的增加可能不会是连续的，其方向和幅度可能会发生变化或减弱。氮和水添加停止后对生态系统的遗留效应仍不清楚。基于中国北方温带草原的 13 年氮和水添加实验，我们研究了短期（2 年）历史氮和水添加停止后对生态系统的遗留效应，即在第 14 年停止氮和水添加后对土壤理化性质和微生物特性的影响。结果表明，历史氮添加对大多数土壤养分变量的正向效应在停止添加两年后减弱，包括铵态氮、硝态氮、溶解有机碳和氮以及Olsen-P 浓度。相比之下，土壤微生物特性具有遗留效应。例如，历史氮输入量为 15 g N·m·a 时，微生物生物量碳、呼吸和碱性磷酸单酯酶活性分别减少了 73.3%、81.9%和 70.3%。这表明与土壤养分相比，微生物参数恢复缓慢，表现出滞后效应。Pearson 相关和冗余分析的结果表明，历史氮添加对微生物参数的遗留效应可以归因于氮添加对土壤 pH 的负面影响。历史水分添加对土壤 pH、铵态氮、溶解有机碳和氮、呼吸和土壤酶活性具有显著的遗留效应，与历史氮添加显著相互作用。这些结果对预测在当地环境改善条件下草原生态系统功能和服务的变化，揭示退化草原的恢复机制具有重要意义。
