Biodiversity describes the variety of life and may influence properties and processes of ecosystems, such as biomass production and resistance to disturbance. We investigated the effects of multiple facets of biodiversity – species richness and composition of the community, and intraspecific diversity in two key species – on both production and resistance of experimentally-assembled biological soil crusts (biocrusts). We found that productivity was most strongly influenced by community composition (variation in the presence and relative proportions of community members), and weakly positively influenced by species richness. Intraspecific diversity, encompassing both the richness and composition of clones, had a neutral effect on community productivity within one focal species (Syntrichia caninervis), but a moderately negative effect on productivity within the other focal species (S. ruralis). Resistance was also most strongly influenced by community composition, although different sets of species contributed most to resistance and production. Resistance was not affected by either species richness or intraspecific diversity in either focal species. Our findings supported our general expectation that community-level facets of biodiversity would be more influential than intraspecific diversity within a species because trait variability among species is usually greater than that within. These results also indicated that although species richness is often thought to strongly affect both productivity and resistance, the presence, absence and relative abundance of particular species may be more influential to both. Simultaneous manipulation of multiple facets of biodiversity in experiments may lead to a more complete understanding of the variety of ways in which biodiversity may regulate ecological systems.

中文翻译：

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群落组成对生态系统抵抗力和生产的影响大于物种丰富度或种内多样性

生物多样性描述了生命的多样性，并可能影响生态系统的特性和过程，例如生物量生产和对干扰的抵抗力。我们研究了生物多样性的多个方面——物种丰富度和群落组成，以及两个关键物种的种内多样性——对实验组装的生物土壤结皮（生物结皮）的生产和抵抗力的影响。我们发现生产力受群落组成（群落成员的存在和相对比例的变化）的影响最大，而受物种丰富度的正面影响较弱。种内多样性，包括克隆的丰富度和组成，对一个焦点物种内的群落生产力具有中性影响（Syntrichia caninervis)，但对其他重点物种的生产力有适度的负面影响 ( S. countryis）。抗性也最受群落组成的影响，尽管不同的物种对抗性和生产的贡献最大。抗性不受任一焦点物种的物种丰富度或种内多样性的影响。我们的研究结果支持我们的普遍预期，即生物多样性的社区层面将比物种内的物种内多样性更具影响力，因为物种之间的性状变异通常大于物种内部的变异性。这些结果还表明，尽管物种丰富度通常被认为对生产力和抗性有很大影响，但特定物种的存在、缺失和相对丰度可能对两者的影响更大。