Species richness and food web structure of soil decomposer community as affected by the size of habitat fragment and habitat corridors

Abstract

While most ecologists agree that the effects of fragmentation on diversity of organisms are predominantly negative and that the scale of fragmentation defines their severity, the role of habitat corridors in mitigating those effects still remains controversial. This ambiguousness rests largely on various difficulties in experimentation, a problem partially solved in the present paper by the use of easily manipulated soil communities. In this 2.5-year-long field experiment, we investigated the responses of soil decomposer organisms (from microbes to mesofaunal predators) to habitat fragment size, in the presence or absence of habitat corridors connecting the fragments. The habitat fragments and corridors, composed of forest humus soil, were embedded in mineral soil representing an uninhabitable (or nonpreferred) matrix for the decomposer organisms. The results demonstrate that soil decomposer organisms do respond to changes in their habitat size: the species richness of microarthropods (mites and collembolans) increased as the size of the fragments increased. Especially collembolan species and predatory mites proved to be sensitive to the restricted habitat size, which is suggested to be a consequence of the large proportion of rare species and small and fluctuating population sizes in these groups. Contrary to our expectations, the presence of corridors had no positive effects on species richness or abundance of any of the studied faunas, possibly because of the low quality of the corridors. On the other hand, the biomass of soil fungi increased in the presence of corridors, which apparently provided a preferred pathway for vegetative dispersal of the fungi. Our results indicate that despite their characteristic underground environment, the response of soil decomposer organisms -in particular that of microarthropods -to habitat size is not unlike to that of the larger organisms in aboveground habitats.

Forest area and connectivity influence root‐associated fungal communities in a fragmented landscape

“…For example, small‐scale experiments have suggested that habitat fragmentation may change predator‐prey dynamics and soil food web structure (Holyoak and Lawler , Rantalainen et al. ). In addition, fragmentation may also affect the distribution of hosts for obligatory parasitic or mutualistic fungal taxa (Cordeiro and Howe ), movement patterns of fungal vectors, and the availability of other abiotic or biotic factors, which may also contribute to disparate responses to habitat fragmentation among fungal groups that differ in life‐history strategies (Sato et al.…”

Rhizosphere fauna: the functional and structural diversity of intimate interactions of soil fauna with plant roots

“…Although the dispersal range of microbes by soil fauna might be quite limited, this distance seems not without significance in respect to the tiny size of microorganisms and microbial competition within the tight network of roots in dense stands of established vegetation. Similarly Rantalainen et al (2004) demonstrated in a laboratory study an important role of enchytraeids in spreading saprophytic fungi between habitat patches through corridors, but in a successive field study it was shown that most fungi had quite good dispersal abilities via hyphal growth independent of soil faunal activity (Rantalainen et al 2005). At present, evidence suggests nematodes as being important vectors of bacteria, whereas fungivores appear to have more important roles as consumers than as vectors of fungi in the rhizosphere.…”

Macroecological patterns in soil communities

“…The understanding of area–species diversity relationships is of utmost and practical importance as they allow prediction of the negative impact of habitat fragmentation on biodiversity (Gaston & Spicer, 1998). The effect of habitat fragmentation on soil biodiversity has been directly addressed in a few studies focusing on microarthropods (Rantalainen et al. , 2005), termites (Fonseca De Souza & Brown, 1994), ants (Suarez et al.…”