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| Invertebrates species found in 3 hectares of forest soil. Source: Krough et. al. 2011 |
Soils provide important services to human populations, including supporting the majority of food production, regulating water quality and supply, buffering against floods and droughts and participating in carbon and nutrient cycling (Lavelle et al. 2006; Jeffrey et al. 2010). Soil organisms represent as much as quarter of described biodiversity (Jeffrey et al. 2010) with most terrestrial invertebrates living in soil for some part of their life cycle (Giller 1996); in some ecosystems soil biodiversity may outnumber above ground biodiversity (Lavelle et al. 2006; Giller 1996).
Soil fauna are a major influence on ecosystem services provided by soils e.g. the importance of earthworms in soils had been appreciated for hundreds of years, their burrowing and casting activities promoting growth of vegetation by incorporating organic matter into the soil and improving drainage (Carpenter et al. 2011). Many other invertebrates also influence soil ecosystem function, including movement of soil particles and breakdown of leaf litter, increasing its decomposition rate.
Spatial and temporal heterogeneity at multiple scales is a clear influence on soil biodiversity, with well-established differences in soil fauna from contrasting mull and mor forest soils (Giller 1996) and habitat type (Carpenter et al. 2012; Eggleton et al. 2005). On a smaller spatial tree species diversity has been found to influence earthworm density (Cesarz et al. 2007) and the presence of deadwood is positively correlated with soil arthropods (Jabin et al. 2004). The work of the Soil Biodiversity Group of the Natural History Museum, London has so far concentrated on soil biodiversity at the site (Eggleton et al. 2009) and landscape (Carpenter et al. 2012) scale, the methodology sampling the main habitat of uniform litter, not sources of micro-heterogeneity. This study investigates diversity patterns of soil macrofauna and plants at a smaller spatial scale, using two sampling methods (Winkler bag extraction of leaf litter and soil pits) within a single woodland to survey eleven ‘microhabitats’; defined as areas of limited spatial extent which differ in character from the surrounding, more extensive habitat. Multivariate statistics are then used to identify the differences between the microhabitat communities, explore the influence of environmental variables and identify what additional variation is added compared to a standard survey. The study site is situated on the Isle of Wight, an island off the coast of south Hampshire not previously sampled by the Soil Biodiversity Group. As the first quantitative survey for the site it will additionally form a baseline study for soil biodiversity monitoring during planned woodland management.