Restoration of Themeda australis swards suppresses soil nitrate and enhances ecological resistance to invasion by exotic annuals

摘要: Understanding processes that underlie ecological resistance to weed invasion is critical for sustainable restoration of invaded plant communities. Experimental studies have demonstrated invasive nitrophilic annuals can be controlled by addition carbon reduce soil nitrate concentrations, sometimes leading enhanced establishment native plants. However, effects supplements on are temporary, and the longer-term value supplementation as a tool dependent re-established ecosystem repeat invasion. We investigated whether swards tussock grass Themeda australis (R.Br.) Stapf (a natural understorey dominant in mesic grassy woodlands SE Australia) could suppress through this or other means, impart ongoing exotic restored woodlands. In remnant annuals, we applied three plot treatments (carbon supplements, annual spring burns untreated control) two seed (± seed) replicated, factorial design. Within 3 years, successful burnt carbon-supplemented plots was associated with reduction levels comparable non-invaded, Themeda-dominated reference sites region (<3 mg/kg), significantly reduced cover compared unseeded plots. By contrast, not seeded Themeda, increased after cessation returned control plots, despite high perennial grasses. Few persistent burning nutrients were evident 9–19 months these treatments. Results suggest keystone species regulates cycling, thereby imparting annuals.