Smith M D, Hartnett D C, Wilson G W T
Division of Biology, Kansas State University, Manhattan, KS 66506, USA e-mail:
Oecologia. 1999 Dec;121(4):574-582. doi: 10.1007/s004420050964.
In tallgrass prairie, plant species interactions regulated by their associated mycorrhizal fungi may be important forces that influence species coexistence and community structure; however, the mechanisms and magnitude of these interactions remain unknown. The objective of this study was to determine how interspecific competition, mycorrhizal symbiosis, and their interactions influence plant community structure. We conducted a factorial experiment, which incorporated manipulations of abundance of dominant competitors, Andropogon gerardii and Sorghastrum nutans, and suppression of mycorrhizal symbiosis using the fungicide benomyl under two fire regimes (annual and 4-year burn intervals). Removal of the two dominant C grass species altered the community structure, increased plant species richness, diversity, and evenness, and increased abundance of subdominant graminoid and forb species. Suppression of mycorrhizal fungi resulted in smaller shifts in community structure, although plant species richness and diversity increased. Responses of individual plant species were associated with their degree of mycorrhizal responsiveness: highly mycorrhizal responsive species decreased in abundance and less mycorrhizal responsive species increased in abundance. The combination of dominant-grass removal and mycorrhizal suppression treatments interacted to increase synergistically the abundance of several species, indicating that both processes influence species interactions and community organization in tallgrass prairie. These results provide evidence that mycorrhizal fungi affect plant communities indirectly by influencing the pattern and strength of plant competitive interactions. Burning strongly influenced the outcome of these interactions, which suggests that plant species diversity in tallgrass prairie is influenced by a complex array of interacting processes, including both competition and mycorrhizal symbiosis.
在高草草原中，由其相关菌根真菌调节的植物物种间相互作用可能是影响物种共存和群落结构的重要力量；然而，这些相互作用的机制和强度仍然未知。本研究的目的是确定种间竞争、菌根共生及其相互作用如何影响植物群落结构。我们进行了一项析因实验，该实验结合了对优势竞争者糙毛须芒草和垂穗草丰度的操控，以及在两种火烧 regime（年度火烧和四年火烧间隔）下使用杀菌剂苯菌灵抑制菌根共生。去除两种优势 C4 禾本科物种改变了群落结构，增加了植物物种丰富度、多样性和均匀度，并增加了亚优势禾本科植物和草本植物的丰度。抑制菌根真菌导致群落结构的变化较小，尽管植物物种丰富度和多样性增加了。单个植物物种的反应与其菌根反应程度相关：菌根反应强烈的物种丰度下降，而菌根反应较弱的物种丰度增加。优势禾本科植物去除和菌根抑制处理的组合相互作用，协同增加了几种物种的丰度，表明这两个过程都影响高草草原中的物种相互作用和群落组织。这些结果提供了证据，表明菌根真菌通过影响植物竞争相互作用的模式和强度间接影响植物群落。火烧强烈影响了这些相互作用的结果，这表明高草草原中的植物物种多样性受到一系列复杂的相互作用过程的影响，包括竞争和菌根共生。
