不同发生期热浪及刈割对呼伦贝尔草甸草原羊草种子生产及重要值的影响

热浪是持续数天时间的极端高温天气事件,常伴随极端高温和水分匮缺双重胁迫,对草本植物生长和繁殖过程存在显著影响。基于此,本研究在内蒙古呼伦贝尔羊草草甸草原进行了为期3年的野外原位热浪模拟试验,关注不同发生期热浪(早期H₁,晚期H₂)及刈割(M)对群落优势种羊草(Leymus chinensis)种子的生产及羊草重要值的连续影响。结果表明：晚期热浪处理(H₂)显著降低了羊草的多度和重要值。刈割处理显著降低了2021年羊草的产量,多度,高度及重要值,分别为51.74%,69.39%,33.70%,45.60%。热浪和刈割的交互作用对羊草的千粒干重,含水率,穗长有显著影响。不同发生期的热浪对羊草的生产影响不一致,面对不同发生期的草地热浪灾害事件,草地管理措施上的重视度和关注点存在差异。在未来极端气候热浪频发背景下,草地刈割的频率应适当降低,以防止草地群落发生退化。

The Influences of Divergent Period of Heat Waves and Mowing on the Seed Production and Important Values of Leymus chinensis in Hulunbuir Meadow Grassland

Heat wave is a kind of extreme hot weather event, normally occurring consecutively for several days long, and usually companied with water deficiency, which have a significant influence on the growth and reproduction process of herbaceous plants. Moreover, the occurrence time of heat wave is a crucial factor that determine its effect on herbaceous plants, but now still lack of research focused on that occurrence time. In this study, a 3-year in situ artificial heat wave simulation experiment was carried out in Hulunbuir meadow grassland, Inner Mongolia, with a focus on the effects of the occurrence time of heat waves (early H₁, late H₂) and mowing (M) on plant seed production and important value of the grassland dominant herbaceous species, Leymus chinensis. Our results showed that the heat wave treatment did not caused a significant variation on Leymus chinensis seed production, but the late occurrence of heat wave (H₂) significantly reduced the species abundance and important value in the community. The mowing treatment significantly recued the seed yield, abundance, height and important value of Leymus chinensis in year 2021 by 51.74%, 69.39%, 33.70% and 45.60%, respectively. The interaction of heat wave with mowing significantly induced variances of 1000-seed dry weight, seed water content and spike length of Leymus chinensis. The results in this study indicated that the divergent time of heat wave occurrence would lead divergent influences on the seed production, growth and community performance of Leymus chinensis. The management measures and focuses should be differently given when the disaster of heat wave would occur at different time. Also, in the scenario of heat wave frequency shall increase in future, the mowing of Leymus chinensis grassland should be reduced to prevent the grassland community from degradation.