Restoring forests on abandoned agricultural lands

Forests on abandoned agricultural lands are among the most common restored habitats worldwide, and in many landscapes, forest clearing and regrowth continue to create and destroy new habitats.  While these forests hold great potential for the conservation and restoration of biological diversity, facilitating their recovery requires that we thoroughly understand the long-term consequences of human land use.  Here I assess the rate and extent of recovery from agriculture by comparing forests on previously plowed lands to adjacent, uncleared stands.  In 20 pairs of forests across the heterogeneous landscape of central New York, I quantified remaining legacies of agriculture in tree communities and environmental conditions, which may influence colonization by herbaceous plants and other species.  Despite striking differences in species composition, the stem density and basal area of the tree communities, and the availability of light in the understory, were similar between the two forest types.  Post-agricultural and uncleared forest soils showed no consistent differences in physical properties, nor in the principal gradient of soil fertility associated with pH.  Within stands, however, soil moisture and pH were more spatially variable in uncleared forests.  Post-agricultural soils had 15% less organic matter, 16% less total carbon and 29% less extractable phosphorus in the top 10 cm than adjacent uncleared stands.  These results demonstrate that, within 100 years, post-agricultural stands have regained many of the attributes of less-disturbed forests.  However, relatively subtle changes in the abiotic environment likely continue to shape the development of biological communities.  Specific habitat modifications may thus facilitate the recovery of native species diversity and composition.