Growth, nutrient cycling, and grazing of three perennial tussock grasses of the Pilbara region of NW Australia

Lachlan Ingram

    Research output: ThesisDoctoral Thesis

    287 Downloads (Pure)

    Abstract

    [Truncated] Despite the importance of arid and semi-arid native grasslands for cattle and sheep production, there is a paucity of data on many important aspects of growth, nutrient cycling and effects of grazing thereof, in native Australian grasslands. In response to this, a long-term (~ 2.5 years) study was undertaken which investigated growth, nutrient uptake, nutrient cycling and soil nutrient availability in grazed and ungrazed plots of three grasslands of the semi-arid Pilbara region of north-western Australia. The three species studied, Astrebla pectinata, Themeda triandra and Eragrostis xerophila are all C4, perennial, tussock grass species native to the Pilbara.

    Using standard monitoring methods (i.e. plant density, foliage and basal cover) it was established that these grasslands were in average to good ‘health’, and that grazing has generally had a minimal, and in some cases, a positive impact on these grasslands.

    Grass growth was heavily reliant on summer rainfall, as rainfall and/or air temperatures during winter were generally too low to result in growth, particularly for inland grasslands i.e. A. pectinata and T. triandra. Despite the short duration of the growing season (due to high evaporative conditions) and the low fertility of Pilbara soils, the rate, as well as the total mass of grass production was comparable to other similar grasslands. Litter accumulation was generally low in all grasslands suggesting that, despite high C:N litter values, turnover was high, particularly after summer rains. Under normal or above-average rainfall, grazing had little impact whereas during periods of low rainfall, grazing had the potential to reduce both current and future above ground phytomass production. The negative impact of grazing on net primary production was, however, nullified to some extent by compensatory regrowth of grazed biomass.

    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • The University of Western Australia
    Publication statusUnpublished - 2001

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