State Key Laboratory of Grassland Agro-Ecosystems, College of Ecology, Lanzhou University, Lanzhou 730000, China; National Hulunber Grassland Ecosystem Observation and Research Station & Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
Forestry College, Fujian Agriculture and Forestry University, Fuzhou 350002, China; Isotope Research Center, Fujian Normal University, Fuzhou 350002, China.
Sci Total Environ. 2022 Dec 20;853:158610. doi: 10.1016/j.scitotenv.2022.158610. Epub 2022 Sep 8.
The heat waves (HW) will be more frequent and intense in the future with increased human activity and uncertain implications for ecosystem carbon fluxes. The semi-arid Eurasian grassland is sensitive to climate change and under frequent HWs attacks. Mowing as one of the most common human practices in this region, combining with HW can have comprehensive effects on plant communities, biomass, and nutrient cycling. Hence, a 3-year (2019-2021) field manipulation experiment was conducted to assess how mowing influenced the carbon cycling under HWs, and the interactions between HWs and mowing on carbon fluxes at the community and ecosystem levels in a Eurasian meadow steppe. Over the three years, HW significantly reduced net ecosystem CO exchange (NEE) and gross ecosystem production (GEP) by 28 % and 8 % (P < 0.05), respectively, whereas ecosystem respiration (Re) did not show significant changes. Moderate mowing (stubble height was set at 6-8 cm) for harvest effectively mitigated ecosystem sensitivity to HWs and significantly increased ecosystem carbon fluxes (NEE, Re, and GEP), biomass and the number of species. Mowing reduced the negative impact of HWs on ecosystem carbon fluxes by about 15 % compared to HWs alone, contributing to the invasion of species such as Thalictrum squarrosum and Vicia amoena, and increased the indirect effect of HW on NEE in the structural equation model. In addition, the higher soil water content (SWC) was another effective way to reduce the impact of HWs. Therefore, mowing and higher SWC would be effective ways to counteract the negative effects of HWs on carbon fluxes in future grassland management.
未来随着人类活动的增加，热浪（HW）将更加频繁和强烈，这对生态系统碳通量有着不确定的影响。半干旱的欧亚草原对气候变化敏感，经常受到 HW 的袭击。割草作为该地区最常见的人类活动之一，与 HW 结合会对植物群落、生物量和养分循环产生全面影响。因此，进行了为期 3 年（2019-2021 年）的野外控制实验，以评估割草如何影响 HW 下的碳循环，以及 HW 和割草对欧亚草原生态系统水平和群落水平碳通量的相互作用。在这三年中，HW 显著降低了净生态系统 CO 交换（NEE）和总生态系统生产力（GEP）分别为 28%和 8%（P<0.05），而生态系统呼吸（Re）没有显示出显著变化。适度割草（留茬高度设定为 6-8 厘米）用于收获可以有效地减轻生态系统对 HW 的敏感性，并显著增加生态系统碳通量（NEE、Re 和 GEP）、生物量和物种数量。与 HW 单独作用相比，割草减少了 HW 对生态系统碳通量的负面影响约 15%，有助于促进 Thalictrum squarrosum 和 Vicia amoena 等物种的入侵，并增加了结构方程模型中 HW 对 NEE 的间接影响。此外，较高的土壤水分含量（SWC）是减轻 HW 影响的另一种有效方法。因此，割草和较高的 SWC 将是未来草原管理中抵消 HW 对碳通量负面影响的有效方法。
