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Restoring a seasonal wetland using woven black plastic weed mat to overcome a weed threshold



Little information is available on the use of woven black polypropylene weed control mat in ecological restoration. At a 6.5-ha area of fertile Vertosol soil ex-farmland near Perth, Western Australia, concerted efforts to control weed using conventional methods such as herbicides, fire and cultivation proved ineffective. After 5 years, weeds still dominated the site, and native plant establishment was poor. Small-scale preliminary trials of various weed suppression coverings were then undertaken, with plastic weed mat the most cost-effective in overcoming the weed threshold, permitting native tree seedling establishment. In a larger-scale trial of weed mat over the whole site, weeds were controlled and high levels of native plant establishment achieved, with a diverse range of understorey, midstorey and overstorey species providing 56% projected foliage cover. This ensured that completion criteria were finally satisfied. These results suggest that weed mat may be effective for weed control in large-scale restoration where conventional methods have failed, as long as ultimate removal or decomposition and other issues are addressed.