Sichuan Zoige Alpine Wetland Ecosystem National Observation and Research Station, Institute of Qinghai-Tibetan Plateau, Southwest Minzu University, Chengdu, 610041, People's Republic of China.
State Key Laboratory of Grassland Agro-Ecosystems & College of Ecology, Lanzhou University, Lanzhou, 730000, People's Republic of China.
Oecologia. 2022 Aug;199(4):897-905. doi: 10.1007/s00442-022-05223-7. Epub 2022 Jul 30.
Grazing is one of the most important management practices for grasslands. To date, most studies on how grazing affects plant diseases have focused on a single plant species, ignoring plant community characteristics and phylogeny. We used data from a 6-year yak grazing experiment (0, 1, 2, and 3 yak(s) ha treatment) in an alpine meadow ecosystem of Qinghai-Tibetan Plateau, from which we tested grazing effects on foliar fungal diseases at both population and community levels. By measuring plant community variables (including richness, evenness, phylogenetic diversity, and composition) and disease severity, we evaluated the relative importance of plant community-mediated effects of yak grazing on community pathogen load with a multi-model inference approach. We found significant differences in pathogen load among different grazing treatments; we recorded the highest and lowest pathogen loads in the 1 yak ha treatment and in the 3 yaks ha treatment, respectively. Pielou's evenness index and community proneness (i.e., an estimate of the capacity of plant communities to support diseases) best explained variation in pathogen load, indicating that plant community-mediated effects (through evenness and proneness) of yak grazing determined pathogen load. Our study provides empirical evidence that grazing influences foliar fungal disease prevalence through plant community evenness and composition, which demonstrates the necessity of incorporating host plant community characteristics into disease load prediction frameworks.
放牧是草原最重要的管理措施之一。迄今为止，大多数关于放牧如何影响植物病害的研究都集中在单一植物物种上，而忽略了植物群落特征和系统发育。我们使用了青藏高原高寒草甸生态系统中为期 6 年的牦牛放牧实验（0、1、2 和 3 头牦牛/公顷处理）的数据，从这些数据中，我们在种群和群落水平上测试了放牧对叶部真菌病害的影响。通过测量植物群落变量（包括丰富度、均匀度、系统发育多样性和组成）和病害严重程度，我们使用多模型推理方法评估了牦牛放牧对群落病原体负荷的植物群落介导效应的相对重要性。我们发现不同放牧处理之间的病原体负荷存在显著差异；我们分别在 1 头牦牛/公顷处理和 3 头牦牛/公顷处理中记录到了最高和最低的病原体负荷。皮埃罗均匀度指数和群落倾向（即估计植物群落支持疾病的能力）最好地解释了病原体负荷的变化，表明牦牛放牧的植物群落介导效应（通过均匀度和倾向）决定了病原体负荷。我们的研究提供了经验证据，表明放牧通过植物群落均匀度和组成影响叶部真菌病害的流行率，这表明有必要将宿主植物群落特征纳入疾病负荷预测框架中。
