Forest herb colonization of postagricultural forests in central New York State, USA

Summary The recovery of forest vegetation following abandonment of agriculture was followed by surveying forest herbs in central New York State at 25 sites where postagricultural forest occurred directly adjacent to old‐woods (forest that has never been ploughed). The abundance, richness and diversity of 50 forest herbs were on average lower in postagricultural forests than in old‐woods. Thirty of 39 forest herbs that were found in at least four stands were less frequent (number of plots present out of 60) in postagricultural forests than in old‐woods. Three species (Aster divaricatus,Dryopteris intermediaandPolystichum acrostichoides) had significantly higher frequency in old‐woods, while none was significantly more common in postagricultural forests. Although differences among species in their frequency in the two forest types were not strongly related to dispersal mode, species with rapid clonal expansion were significantly more frequent in postagricultural stands. Several species that were less frequent in postagricultural forests than in old‐woods showed decreases in density in postagricultural forests with increasing distance from the adjacent old‐woods.