Conservation of the Grassy White Box Woodlands: Rangewide Floristic Variation and Implications for Reserve Design

Abstract

Grassy white box (Eucalyptus albens Benth.) woodlands once covered several million hectares of the wheat-sheep belt of south-eastern Australia. The pre-European floristic composition of these woodlands is little-known, as almost all of them were rapidly cleared for cropping or modified by livestock grazing. Woodland remnants were surveyed across NSW, to describe rangewide variation in the woodland flora, and to provide a basis for reserve design. As far as could be detected from current remnants, some of the major features of the original grassy white box woodland understorey appear to have been relatively constant across NSW: on a wide variety of soils and parent materials from southern to northern NSW, the dominant native grasses in little-disturbed sites were generally Themeda australis (R.Br.) Stapf andor Poa sieberiana Sprengel, and many of the subsidiary herbs and grasses occurred across this range. There were, however, several natural patterns of variation requiring consideration in conservation planning: about half of the subsidiary herb and grass species showed a relationship with latitude, probably relating to a climatic gradient; the understorey became more shrubby, with a sparser and more varied grass component, on soils classed as being 'unsuitable for agriculture'; and on basalt parent materials of the Inverell Plateau, Dichanthium sericeum (R.Br.) A.Camus may have been a more prominent component of the understorey. Natural floristic variation was overlain by patterns resulting from European disturbance, as indicated by floristic distinctions between sites of differing landuse. While these distinctions were partly related to poorer soil resource class in State Forests and Nature Reserves, grazing by livestock and tree clearing are likely to to have contributed to them. Reserves in ine whire box woodiands are presentiy few, and are not representative of the naturai variation. ~ o s t existing reserves occur on soils unsuited to agriculture, compared with the grazing or arable land of typical grassy woodland. Cemetery remnants, rail easements, Travelling Stock Reserves and roadsides provide the best opportunities for conservation on higher-quality soils. Remnant quality declined significantly in southern NSW, indicating a need for greater conservation effort in southern areas.