College of Animal Science and Technology, China Agricultural University, Beijing, 100193, China.
Department of Natural Resource Ecology and Management, Oklahoma State University, 008C AGH, Stillwater, Oklahoma, 74078, USA.
Ecology. 2018 Aug;99(8):1847-1856. doi: 10.1002/ecy.2401. Epub 2018 Jul 2.
Overgrazing substantially contributes to global grassland degradation by decreasing plant community productivity and diversity through trampling, defoliation, and removal of nutrients. Arbuscular mycorrhizal (AM) fungi also play a critical role in plant community diversity, composition, and primary productivity, maintaining ecosystem functions. However, interactions between grazing disturbances, such as trampling and defoliation, and AM fungi in grassland communities are not well known. We examined influences of trampling, defoliation, and AM fungi on semiarid grassland plant community composition for 3 yr, by comparing all combinations of these factors. Benomyl fungicide was applied to reduce AM fungal abundance. Overgrazing typically resulted in reduced dominance of Stipa Krylovii, contributing to degradation of typical steppe grasslands. Our results indicated trampling generally had little effect on plant community composition, unless combined with defoliation or AM fungal suppression. Defoliation was the main component of grazing that promoted dominance of Potentilla acaulis over Stipa krylovii and Artemisia frigida, presumably by alleviating light limitation. In non-defoliated plots, AM fungi promoted A. frigida, with a concomitant reduction in S. krylovii growth compared to corresponding AM suppressed plots. Our results indicate AM fungi and defoliation jointly suppress S. krylovii biomass; however, prolonged defoliation weakens mycorrhizal influence on plant community composition. These findings give new insight into dominant plant species shifts in degraded semiarid grasslands.
过度放牧通过踩踏、刈割和养分去除，显著降低植物群落生产力和多样性，从而导致全球草原退化。丛枝菌根（AM）真菌在植物群落多样性、组成和初级生产力方面也起着至关重要的作用，维持着生态系统的功能。然而，放牧干扰（如踩踏和刈割）与草原群落中 AM 真菌之间的相互作用尚不清楚。我们通过比较这些因素的所有组合，研究了踩踏、刈割和 AM 真菌对半干旱草原植物群落组成的影响，为期 3 年。苯菌灵杀菌剂被用来减少 AM 真菌的丰度。过度放牧通常会导致克氏针茅的优势度降低，导致典型草原的退化。我们的结果表明，除非与刈割或 AM 真菌抑制结合，否则踩踏通常对植物群落组成影响不大。刈割是促进委陵菜和冷蒿对克氏针茅优势的主要放牧因素，可能通过缓解光照限制来实现。在未刈割的样地中，AM 真菌促进了冷蒿的生长，与相应的 AM 抑制样地相比，克氏针茅的生长减少。我们的结果表明，AM 真菌和刈割共同抑制克氏针茅的生物量；然而，长时间的刈割会削弱 AM 对植物群落组成的影响。这些发现为退化半干旱草原中优势植物物种的变化提供了新的见解。
