Alien plant invasion has become one of the earth’s most pressing ecological problems (Vitousek et al. 1997). Plant invasions have largely been overlooked in arid desert ecosystems even though the impact can be monumental (Pimentel etal. 2007). Alien annual grasses pose a significant threat to altering the basic structure and function of desert communities. One of the greatest threats is the increase in wildfire frequency and intensity. Fire frequency is increasing at alarming rates and changing fire regimes is providing opportunity for greater likelihood of full-scale plant invasions (Brooks and Pyke 2001).
This impact and threat is only heightened with projected models of change in precipitation patterns (Sun et al. 2007). Precipitation is predicted to occur in early fall months with more high intensity rainfall events. The ability for alien annual grasses to utilize earlier water resources in deserts may give them a monumental head start in seed germination and higher survival over winter. This head start will most likely lead to full-scale invasion as the competition for resources become tilted in favor of the opportunistic and aggressive alien annual grasses. The objective of this study was to experimentally identify biophysical variables and their interactions that influence the growth and reproduction potential of red brome.
We examined seedling emergence, growth, and reproduction of the exotic grass red brome in response to early fall precipitation, soil texture, fertile-island topography, and burn history in a full-factorial design located in natural climate conditions. Seedling emergence, biomass, plant height, and seed production were measured.
Results/Conclusions
Early fall precipitation had the strongest effect on all response variables; soils from fertile-islands, and from burned landscapes increased growth and reproduction of red brome. Fertile island vs inter-shrub space soils increased biomass production followed by soils from burned landscapes vs unburned landscapes. Our data suggests that areas with finer-textured soil will be more prone to high densities and biomass of red brome particularly in years with significant fall moisture. Coarser-textured soils are at less risk of burning due to lower abundance and growth potential of exotic grasses and may create natural fire breaks. Fertile islands soils in both unburned and burned areas support higher densities of red brome and increase seed production that likely contributes to the maintenance of red brome populations. Management planning for fire intervention should consider early-fall precipitation patterns, soil texture and fire history as important determinants of red brome growth and fire potential.