NATURAL REFORESTATION OF ABANDONED FARMLAND - THE ROLE OF SOILS

Natural regeneration of abandoned farmland in several areas within the catchments of the Sydney Water Board has been very slow. Several hypo theses have been put forward to explain the fact that natural reforest ation has not occurred, even after up to 50 years of abandonment. This study examines regeneration in relation to substrate, soil types and soil chemistry. The abandoned farmlands occur on four main soil types: (i) eutrophic krasnozem, now occupied mainly by bracken fern (Pteridi um esculentum) associated with young seedlings of Eucalyptus and Acaci a; (ii) mesotrophic yellow earth, now occupied by blady grass (Imperat a cylindrica), with few tree seedlings and scattered, dead Acacia tree s; and (iii) mesotrophic alluvial soil, and (iv) oligotrophic lithosol , which both support stands of Acacia. The soil properties of the kras nozem and the yellow earth appear to be suitable for tree establishmen t and growth, and do not differ from similar soils in nearby areas cur rently under cultivation or supporting undisturbed forest. Poor forest establishment in these soils might be the result of frequent fires an d biotic factors such as competition from the bracken and blady grass sward. The lack of eucalypt reforestation of the poorer soils might be explained by their poorer fertility, perhaps tolerated better by the Acacia species.