The effects of trampling on soil invertebrate fauna communities in coast live oak forests (Quercus agrifolia) in southern California

Decomposition processes are vital to every ecosystem on Earth.  Microbes and fungi are true decomposers, but edaphic and detritus-dwelling invertebrates perform important ecosystem services including litter comminution, soil aeration, and promotion of microbial population growth.  Trampling can cause major disturbances to the soil environment including; alteration of soil nutrient concentrations, moisture levels, organic matter content, structure and compaction.  This experiment explores the effects of trampling on edaphic and detritus-dwelling invertebrate fauna communities in southern California parks.  Invertebrate community data were collected from six San Diego County Parks and three Orange County Regional Parks in Fall 2011 and Spring 2012.  Eight soil monoliths were extracted from each park (25cm length x 25cm width x 5cm depth) along with any detritus located directly above each monolith.  Four of these monoliths came from rarely trampled areas within the park and four came from adjacent frequently trampled areas (a paired design).  Soil monoliths were sorted by hand on site and all invertebrates visible to the naked eye were preserved and transported to the laboratory.  Detritus samples were placed in Berlese Funnels to collect invertebrates.  All invertebrates were taxonomically identified to family (and further, when feasible).  Community composition differed significantly among sites (p=0.001) and between seasons (p=0.001) but did not differ significantly between impact levels (p=0.052).  Abundances differed significantly among sites (p=0.015), between impact levels (p<0.001) and between seasons (p<0.001).  High impact sampling areas showed significantly lower diversity for both Shannon and Simpson diversity indices (p< 0.001 and p=0.32, respectively) than low impact sampling areas.