The Effects of Loblolly Pine Plantations on Small Mammal Populations

Small mammal populations were analyzed over a yearly cycle in four contrasting but similar-aged habitats of the Georgia Piedmont. An abandoned pasture and a broomsedge field were sampled monthly in conjunction with two similar habitats containing loblolly pines which were planted at the time of abandonment. Cotton rat {Sigmodon hispidus) was the only mammal species regularly captured. Cotton rat densities were significantly greater and their population composition remained more constant in the natural vs. planted habitats. Discriminant function analysis indicated that foliage height diversity, cover, and plant and litter biomass were all significant habitat variables accounting for the population differences. The planting of pines in monoculture significantly altered the structural nature of the understory vegetation and thus the small mammal microhabitat. The pines increase the rate of succession and the system rapidly becomes a marginal small mammal habitat. Sigmodon populations present during the early stages of pine growth were smaller, had larger home ranges, and contained a remarkably high percentage of transient males. As the pine canopy closes, a complete shift occurs in the understory vegetation composition and structure. Small mammal population densities are extremely low following pine canopy closure.