In southeastern Australia, the establishment of tree plantations of Pinus radiata D. Don result in fragmentation of native forests. Conditions within forest fragments adjacent to plantations are dynamic. We use the Wog Wog Habitat Fragmentation Experiment to document the influence of a mature plantation on microclimate, soil chemistry and debris within forest fragments and in continuous forest controls. Fragments were of three sizes - small (0.25 ha), medium (0.88 ha), and large (3.06 ha) - and sampling was stratified according to location within fragment (center, edge, corner). Small forest fragments exhibited an increase in canopy cover and soil moisture, and cooler daily maximum temperatures than continuous forest. We also found the amount of native litter was reduced in fragment corners. Our results demonstrate that tree plantations can continue to modify environmental conditions within forest fragments long after plantation establishment. Changes to the conditions within fragments may facilitate alterations to the biotic component of these areas. These findings have important implications for the conservation and management of dynamic forest-plantation systems.