Archibald, R.D., Bowen, B.J., Hardy, G.E.St.J., Fox, J.E.D. and Ward, D.J. (2005) Changes to tuart woodland in Yalgorup National Park over four decades. In: Calver, M.C., Bigler-Cole, H., Bolton, G., Dargavel, J., Gaynor, A., Horwitz, P., Mills, J. and Wardell-Johnston, G., (eds.) A Forest Conscienceness: Proceedings 6th National Conference of the Australian Forest History Society Inc. Millpress Science Publishers, Rotterdam, pp. 363-372.
The condition of the tuart tree (Eucalyptus gomphocephala), a coastal southwestern Australian woodland species, has declined dramatically within parts of its distribution over the last decade, particularly within Yalgorup National Park. Prior to the park being gazetted in 1968, some of the woodlands were used for cattle grazing. Frequent, light, understorey burns were carried out to encourage grass fodder growth. Earlier, Aboriginal use is believed to have involved a similar regime to facilitate hunting and access. Since gazettal, the majority of the park has either been excluded from fire, or burnt infrequently by wildfire and prescribed fire. Consequently, from 1968 to the present, most fires are thought to have been more intense due to increased fuel loads. Alterations in disturbance patterns (particularly fire) elsewhere, have been linked with vegetation changes (composition and structure) and in some instances, declining tree health. For tuart woodland, it has been proposed that increased abundance and vigour of the lower storey peppermint tree (Agonis flexuosa) and a decline in the health of tuart trees are consequences of reduced fire frequency. Sample plot data from the mid – late 1970s and photographs from 1957 are contrasted with the 2003/2004 situation to describe changes in tuart woodland. Declining tuart health, changes in the health and abundance of some understorey species (for example, fewer Banksia attenuata) and a shift towards peppermint dominance are revealed. The contribution of changing fire regimes to these trends is explored. While a link between fire and changes to the woodland may be established, factors underlying the loss of tuart dominance remain to be determined. An integrated research project is in progress to examine the range of decline factors.