EFFECT OF PARTHENIUM WEED (Parthenium hysterophorus L.) ON GRAZED PLANT COMMUNITIES DURING A PERIOD OF CONCERTED MANAGEMENT

The response of a rangeland community to different parthenium weed (Parthenium hysterophorus L.) management regimes is being assessed in a pastoral area at Kilcoy, Queensland, Australia. The area selected to do this work is on a gentle slope with good drainage and has a typical soil for this region (i.e. a brown-grey Dermosol). This area has been divided into four sites to undertake the following treatments: 1) non-grazed with chemical control applied; 2) non-grazed without chemical control; 3) grazed with chemical control applied and 4) grazed without chemical control. In the previous season, prior to the application of these treatments (i.e. in summer 2009/2010) the species composition of the community was recorded and used as the community benchmark. This paper reports upon that community structure. In total, 48 plant species were recorded within the above-ground community and 64 species within the soil seed bank. The above-ground vegetation was dominated by stoloniferous grass species, but there was also a high frequency of species belonging to the Malvaceae, Chenopodiaceae and Amaranthaceae families. Parthenium weed was found in high abundance and frequency within all of the four sites (i.e. 100 % and 63 % respectively). A correlation analysis showed that parthenium weed frequency was negatively associated with the Shannon index, as well as with the dry matter of the remaining species. A similar trend was found within the soil seed bank, with the species diversity being lower when parthenium weed’s frequency was higher. These preliminary results provide a background against which the effect of chemical management of parthenium weed and/or a reduction in grazing pressure might improve the species composition of the community, which will be best seen in the years to come.