ENVIRONMENTAL-EFFECTS OF FOREST SOIL-INVERTEBRATE AND FUNGAL DENSITIES IN OAK STANDS ALONG AN URBAN-RURAL LAND-USE GRADIENT

Urban-rural land use gradients are environmental gradients determined largely by human activity. Although gradients of land use are readily measurable, little is known about the effects of urbanization on fores t soil properties and soil fauna and microflora. The purpose of this r esearch was to analyze soil-invertebrate and fungal densities in undis turbed forest stands along a soil environmental gradient characterized by i) higher heavy metal concentration, ii) higher organic matter and N concentration, and iii) slightly lower soil pH in urban than in rur al stands. The distribution of Oribatida, Collembola, and fungivorous nematodes are potentially influenced by high heavy metal concentration s in the urban stands, though other factors associated with the urban- rural environmental gradient may also have a strong influence. Litter fungal abundance was followed on a cohort of oak litter over a 36 week period. Although fungal densities were initially similar in urban, su burban, and rural sites, total fungal growth rose quickly in rural lea f litter relative to litter of the same species in urban and suburban stands. As with the fungivorous microinvertebrate feeding groups, fung al densities were negatively correlated with forest floor heavy metal concentrations. The observed patterns in soil invertebrate populations may be partly a trophic response to lower fungal densities in litter in urban stands.