Impacts of Soil Faunal Community Composition on Model Grassland Ecosystems

Abstract

Human impacts, including global change, may alter the composition of soil faunal communities, but consequences for ecosystem functioning are poorly understood. We constructed model grassland systems in the Ecotron controlled environment facility and manipulated soil community composition through assemblages of different animal body sizes. Plant community composition, microbial and root biomass, decomposition rate, and mycorrhizal colonization were all markedly affected. However, two key ecosystem processes, aboveground net primary productivity and net ecosystem productivity, were surprisingly resistant to these changes. We hypothesize that positive and negative faunal-mediated effects in soil communities cancel each other out, causing no net ecosystem effects.

Linking Species Richness, Biodiversity and Ecosystem Function in Soil Systems

“…The microcosms were maintained in the Ecotron for a period of 8.5 months. Bradford et al (2002) found significant increases in decomposition rate in the most complex faunal treatment, but both mycorrhizal colonization and root biomass were less abundant in the macrofauna treatments. Interestingly plant growth was not enhanced in these treatments, despite higher nutrient (N and P) availability.…”

“…Bradford et al suggested that respiration was most likely buffered by the combined stimulatory effect of both mesofauna and macrofauna on microbes, which served to maintain microbial activity at a level equivalent to that in the microfauna and mesofauna communities. This study has been considered a benchmark in large-scale microcosm studies, but as Bradford et al (2002) note, it is not a substitute of longer-term in situ field studies.…”

“…In fact, earlier analyses of similar food webs by Moore et al (1993) and Moore and de Ruiter (2000) showed that loss of top predators had much greater impacts on lower trophic levels than their low biomasses might indicate. Another approach to microcosm studies was taken by the group working in the Ecotron facility at Silwood Park, UK Constructing analogs of a temperate, acidic, sheep-grazed grassland in northern Britain, Bradford et al (2002) established terrestrial microcosms of graded complexity, with soil, plants and microorganisms, and then assemblages of microfauna, micro-and mesofauna, and then micro-, meso-and macrofauna. Thus, soil community composition was manipulated through assemblages of different animal body sizes.…”

Biotic interactions mediate soil microbial feedbacks to climate change

“…A variety of other fauna, including meso-or microinvertebrates, also will contribute to the grazing effects recorded here (7,33). Indeed, the exclusion of other common macroinvertebrates, such as diplopods, from experimental chambers means that the invertebrate treatments plots are likely to underrepresent the potential for grazers to regulate the fungal community response to global change (34). However, the unique capacity of isopods to sever and ingest thick fungal cords makes this interaction a particularly strong one within forest soil (20).…”

Biotic interactions, ecological knowledge and agriculture

“…The role of diversity per se, however, is unclear. In experiments that removed key taxonomic groups, little change in the rates of soil respiration or above-ground productivity were found (Liiri et al 2002), perhaps because the relatively low degree of specialization among detritivores implies considerable redundancy among this functional group (Bradford et al 2002). Others caution that it may take exposure to multiple types of stresses before there is sufficient loss of buffering capacity due to redundancy within functional groups for changes in ecosystem properties to become apparent (Griffiths et al 2000).…”