Swiss Federal Institute of Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903, Birmensdorf, Switzerland.
Microb Ecol. 2014 Oct;68(3):584-95. doi: 10.1007/s00248-014-0435-0. Epub 2014 Jun 3.
Grassland ecosystems support large communities of aboveground herbivores that are known to directly and indirectly affect belowground properties such as the microbial community composition, richness, or biomass. Even though multiple species of functionally different herbivores coexist in grassland ecosystems, most studies have only considered the impact of a single group, i.e., large ungulates (mostly domestic livestock) on microbial communities. Thus, we investigated how the exclusion of four groups of functionally different herbivores affects bacterial community composition, richness, and biomass in two vegetation types with different grazing histories. We progressively excluded large, medium, and small mammals as well as invertebrate herbivores using exclosures at 18 subalpine grassland sites (9 per vegetation type). We assessed the bacterial community composition using terminal restriction fragment length polymorphism (T-RFLP) at each site and exclosure type during three consecutive growing seasons (2009-2011) for rhizosphere and mineral soil separately. In addition, we determined microbial biomass carbon (MBC), root biomass, plant carbon:nitrogen ratio, soil temperature, and soil moisture. Even though several of these variables were affected by herbivore exclusion and vegetation type, against our expectations, bacterial community composition, richness, or MBC were not. Yet, bacterial communities strongly differed between the three growing seasons as well as to some extent between our study sites. Thus, our study indicates that the spatiotemporal variability in soil microclimate has much stronger effects on the soil bacterial communities than the grazing regime or the composition of the vegetation in this high-elevation ecosystem.
草原生态系统支持大量的地上食草动物，这些动物已知会直接和间接地影响地下特性，如微生物群落组成、丰富度或生物量。尽管草原生态系统中有多种功能不同的食草动物共存，但大多数研究只考虑了单一群体的影响，即大型有蹄类动物（主要是家畜）对微生物群落的影响。因此，我们研究了排除四种功能不同的食草动物如何影响两种具有不同放牧历史的植被类型中的细菌群落组成、丰富度和生物量。我们在 18 个亚高山草地站点（每个植被类型 9 个）使用围栏逐步排除大型、中型和小型哺乳动物以及无脊椎草食动物。我们在三个连续的生长季节（2009-2011 年）中使用末端限制性片段长度多态性（T-RFLP）在每个站点和围栏类型上评估根际和矿物土壤的细菌群落组成。此外，我们测定了微生物生物量碳（MBC）、根生物量、植物碳氮比、土壤温度和土壤水分。尽管这些变量中的几个受到食草动物排除和植被类型的影响，但出乎我们的意料，细菌群落组成、丰富度或 MBC 并没有受到影响。然而，细菌群落在三个生长季节之间以及在我们的研究地点之间存在很大差异。因此，我们的研究表明，土壤微气候的时空变异性对土壤细菌群落的影响远大于放牧制度或该高海拔生态系统中植被的组成。
