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Australian National University (2010)

The biodiversity value of revegetation

Munro, Nicola Therese

Titre : The biodiversity value of revegetation

Auteur : Munro, Nicola Therese

Université de soutenance : Australian National University

Grade : Doctor of Philosophy (PhD) 2010

Résumé partiel
The last few decades have seen a substantial increase in the establishment of revegetation plantings in production landscapes to mitigate the impacts of prior vegetation clearing. These plantings can have a variety of purposes, such as stream bank stabilisation, lowering of water tables, erosion control, and livestock protection. All plantings have the potential to also provide habitat for wildlife, but the extent to which this occurs can differ substantially depending on the attributes of the plantings. In an agricultural landscape in south-eastern Australia, I compared revegetation plantings differing in a number of key attributes. The overarching goals were to determine if : a) plantings established with high plant diversity provided greater biodiversity outcomes than plantings established with low plant diversity, and b) what other attributes of a planting provided greater biodiversity outcomes. Specifically, 1 identified two types of revegetation : (1) ‘ecological plantings’ which were planted for ecosystem restoration purposes and were characterised by a diverse assemblage of tree, shrub and understorey species ; and, (2) ‘woodlot plantings ’ which were planted with low plant species richness of primarily overstorey species (agro-forestry plantings). Both types of plantings were established with predominantly local, native vegetation. I investigated 27 ecological plantings and 16 woodlot plantings, both ranging in age from 2 to 26 years. In addition, I compared the plantings to 11 paddocks (cleared agricultural land) and 18 uncleared remnant sites, as the starting point and goal, respectively, of revegetation. Across a total of 72 sites, I compared the development of vegetation structure and floristic richness, the bird and mammal communities present in the sites, and the ecological function of the sites. Vegetation structural complexity increased with age of planting, toward that of remnants, even when very few species were planted at establishment. Species richness of plants, however, did not increase with age, indicating that colonisation did not occur through time. Therefore, plantings may not provide for the conservation of non-planted flora. Ecological plantings were more similar to remnant vegetation in structure and species composition, and contained greater shrub cover, more plant lifeforms, and lower weed cover than woodlot plantings. In general, ecological plantings can achieve a similar overall structural complexity to remnant vegetation within 30 years, but will not gain a ground layer of native plants, and will not necessarily contain some structural features by this age (such as tree hollows and fallen timber).

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