State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling 712100, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A&F University, Yangling 712100, PR China; Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xian 710061, PR China.
Sci Total Environ. 2019 Mar 25;658:1440-1451. doi: 10.1016/j.scitotenv.2018.12.289. Epub 2018 Dec 21.
The effects of precipitation patterns on the metabolism of soil microbes are poorly understood, especially in water-limited ecosystems where soil microorganisms play crucial roles in the turnover of soil organic carbon (SOC) and nutrients. We investigated the influence of the gradient levels of mean annual precipitation (MAP from 300 to 900 mm) on soil microbial metabolism in an arid and semi-arid grassland region located in Loess Plateau, China and identified relationships between microbial metabolic limitations and the variation of soil organic matter (SOM). Microbial metabolism in this arid and semi-arid region was limited by soil C and phosphorus (P) or nitrogen (N). Microbial C and P limitations decreased with the increase of MAP. Microbial C and P limitations were lowest in the areas with MAPs of 700-900 mm, whereas N limitation was observed in the areas with MAPs >700 mm. The results of a variation-partitioning analysis and partial least squares path modeling indicated that the microbial C and N/P limitations on regional scales were mainly determined by climate factors (MAP and mean annual temperature (MAT)), followed by vegetation biomass and soil properties. The extents of soil drying-rewetting processing caused by different MAPs directly affected microbial nutrient limitation. Our results suggested that the influence of precipitation variation on microbial metabolic limitation strongly governed SOM stability and that an increase in the rate of SOM decomposition with increasing precipitation could be caused by increased microbial nutrient limitation. SOM may be most stable at a MAP of 700 mm in the arid and semi-arid regions (300-900 mm MAP) where microbial nutrient limitation was lowest. This study provided novel insights into the responses of soil microbial metabolism to precipitation change and is an important step toward understanding the mechanisms of SOM stability in an arid and semi-arid grassland ecosystem under scenarios of precipitation variation.
降水模式对土壤微生物代谢的影响还知之甚少，尤其是在水分有限的生态系统中，土壤微生物在土壤有机碳 (SOC) 和养分的转化中起着至关重要的作用。我们研究了年平均降水量 (MAP 从 300 至 900 毫米) 的梯度水平对位于中国黄土高原干旱半干旱草原地区土壤微生物代谢的影响，并确定了微生物代谢限制与土壤有机质 (SOM) 变化之间的关系。该干旱半干旱地区的微生物代谢受到土壤 C、磷 (P) 或氮 (N) 的限制。微生物 C 和 P 的限制随着 MAP 的增加而降低。在 MAP 为 700-900 毫米的地区，微生物 C 和 P 的限制最小，而在 MAP 大于 700 毫米的地区则观察到 N 限制。变分划分分析和偏最小二乘路径模型的结果表明，区域尺度上微生物 C 和 N/P 限制主要受气候因素 (MAP 和年平均温度 (MAT)) 决定，其次是植被生物量和土壤特性。不同 MAP 引起的土壤干湿再湿润处理的程度直接影响微生物养分限制。研究结果表明，降水变化对微生物代谢限制的影响强烈控制着 SOM 的稳定性，降水增加导致微生物养分限制增加，可能会导致 SOM 分解速率增加。在干旱半干旱地区 (MAP 为 300-900 毫米) ，当微生物养分限制最小时，MAP 为 700 毫米可能使 SOM 最稳定。本研究为土壤微生物代谢对降水变化的响应提供了新的见解，是理解降水变化情景下干旱半干旱草原生态系统 SOM 稳定性机制的重要一步。
