whole-sekuljica-thesis-2012.pdf (1.43 MB)
Re-establishing dry sclerophyll forest on unused farmland
thesisposted on 2023-05-26, 01:34 authored by Sekuljica, L
There have been few systematic experimental studies testing different restoration techniques in varying environments on the same property. The present experimental work was done to provide a basis for re-establishing sclerophyll forest on agricultural land located on the Tasman Peninsula. In determining appropriate habitat restoration goals it was necessary to reconstruct the original vegetation. Thus the first goal was to conduct a vegetation survey of the field site with the aim of identifying and mapping the vascular plant species and community types present. The results from the vegetation survey showed that the remnant vegetation consisted of sedgey Eucalyptus ovata woodland, shrubby E. obliqua forest and heathy E. obliqua/E. amygdalina forest and that the pasture consisted of five floristic communities dominated by exotic grasses. The environmental envelopes of the three native vegetation communities were then compared to those of the exotic vegetation communities. This process allowed the exotic species combinations to be used as analogues of the former distribution of the native vegetation communities. The level of intervention that was required to promote the successful re-establishment of native vegetation was investigated. The sowing of native seeds resulted in poor germination of all native species, with the exception of Acacia verticillata and A. melanoxylon, with germination the greatest in unfenced areas where weed colonisation of gaps was slowest. The reintroduction of Eucalyptus and Allocasuarina seedlings into three different exotic weed communities demonstrated that soil properties had a greater influence on seedling survival and growth than competition from exotic weeds and that species did best on sites in which they would have naturally occurred. In the field of restoration ecology there is little research on whether the simultaneous reintroduction of tree, shrub and groundcover species could accelerate forest restoration on agricultural land compared to plantings of single species. The results obtained from the field trial that examined the neighbour interactions of E. obliqua, Allocasuarina littoralis and Poa labillardierei showed that the presence of neighbours could promote greater seedling growth than that of individuals planted without neighbours. For A. littoralis and E. obliqua the greatest growth occurred when its neighbours were four A. littoralis seedlings, whilst the greatest growth by P. labillardierei occurred when its neighbours were a mixture of itself and E. obliqua. These results suggest that intra- and interspecific interactions can have a positive effect on the growth of the three species. The field trials at the study site indicate that competition from weeds and lack of native seed storage limit the ability of native vegetation to re-establish on the abandoned pasture. Poor establishment from the sowing of native seeds onto gaps created in the grass sward illustrated the need to re-introduce seedlings to promote the restoration of native species in the exotic weed communities. The seedlings of different dominant tree species varied in their survival and growth in different exotic weed communities, indicating the importance of adjusting restoration processes to variations in microhabitat. Restoration may also be accelerated by planting mixtures of tree, shrub and groundcover species.
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