Germinable soil seed bank of pasture, revegetation and remnant Cumberland Plain Woodland

Abstract

SummaryRevegetation of abandoned pasture by planting tree and shrub species has been undertaken in western Sydney to restore Cumberland Plain Woodland. This study investigated the germinable soil seed bank of pastures, revegetated areas and remnants to assess the potential of the seed bank to contribute to Cumberland Plain Woodland restoration. Soil cores were taken, air dried, sieved and spread out in germination trays. Half of the samples were subjected to a fire treatment, with the other half as controls. The size of the germinable seed bank was 9,400–9,500 m−2 in the pasture and revegetated areas, and 3,000 m−2 in the remnant. Exotics, mainly forbs, dominated the seed bank in pasture and revegetated areas, with more than half the number of species and three quarters the number of seedlings. Numbers of native species and seedlings were half to one quarter of exotics in the pasture and revegetated areas. In remnants, native species outnumbered exotics, but numbers of native and exotic seedlings were approximately equal. Numbers of native shrub species and seedlings were low, and seedlings of one native tree appeared. There was some recruitment of seedlings from planted shrub species in the revegetated area. Only native species (numbers of species; seedling numbers) increased after the burn treatment; numbers of exotic species and seedlings were already high in the control and did not increase further after burning. Species composition was significantly affected by vegetation type, and by fire. The seed banks of the pasture and revegetated areas were very similar to each other, and both were most dissimilar to the remnant. The soil seed bank of the pasture had a heavy burden of exotic weeds, the majority forbs with the seeder fire response, and lacked the propagules of native species. The revegetated area was the same, as the revegetation method used planted only trees and some shrubs and did not address the problems of the weed seed abundance and propagule limitation of natives.