We examined the distribution and abundance of ground-dwelling mammals in 13 areas involving 42 eucalypt communities within 500 000 ha of eucalypt forest in south-eastern New South Wales. Data are presented on the relative abundance and distribution of mammals in relation to the complexity of the habitat of the vegetation communities, basal area of the trees, and indices of nutrients in the foliage of the trees. For all ground-dwelling mammals except common wombat, large wallaby and red fox there was no positive correlation with foliage nutrients, nitrogen, phosphorus and potassium, which have been found to be important for the arboreal fauna. Abundances of native small mammals were positively correlated with foliage magnesium and habitat complexity and negatively with nitrogen, phosphorus and potassium. However, habitat complexity was more important than the nutrient status; small mammals were present at all nutrient levels, but their abundance fell substantially as habitat complexity decreased. Also, the influence of nutrients was masked in habitats of high complexity; there was no relationship with nitrogen, phosphorus and potassium and a negative relationship with magnesium. Sites with a high basal area of trees had a sparse understorey of shrubs. Abundances of some herbivorous mammals such as eastern grey kangaroo were positively correlated with the basal area of trees and negatively with habitat complexity, which indicates their preference for forest with an open understorey. The predators, dingo,red fox and cat, were found in all categories of the variables, with cat positively correlated with basal area and negatively with magnesium and red fox the opposite. Dingo was positively correlated with habitat complexity. The composition of the ground-dwelling mammal fauna in south-eastern forests is determined by the complexity of the understorey. A significant reduction in understorey shrubs would result in a decrease in the abundance and number of species of small and medium-sized mammals and an increase in large grazing mammals. The results are discussed in relation to the arboreal fauna and forest management, including the use of control burning and grazing by domestic stock.
