Print PageBiofuel crops are of interest as a means of reducing our dependence on fossil fuels and as a potential means of mitigating atmospheric pollutants associated with climate change. We describe methods to examine the effects of feral biofuel crop escapes on constructed native plant communities growing in outdoor sunlit mesocosms under ambient and simulated climate change conditions. Experimental results after the first year of a multi-year study are reported below. Mesocosms containing wet prairie or oak savannah communities were exposed to two temperature levels (ambient and elevated) and two moisture levels (control and drought-stressed). Elevated temperature mesocosms were approximately 2oC warmer than the ambient controls during the summer months. Soil moisture levels for the drought treatment were maintained 20% lower than the controls during the summer dry period. Control soil moisture regimes were based on seasonal soil moisture patterns at nearby native wet prairie and oak savannah communities in the Willamette valley of Oregon. Each mesocosm contained three 1.2 m2 pots of equal plant density at the start of the experiment in 2010: the control pot contained five species of native grasses and forbs; a second pot contained five natives plus crop sorghum (Sorghum bicolor [cv Piper]) an annual; a third pot contained five natives plus Johnsongrass (Sorghum halepense, a weedy rhizomatous perennial which hybridizes with S. bicolor).
Results/Conclusions
At the end of the first growing season in the oak savanna mesocosms, both Sorghum species produced significantly less biomass (P<0.05) than a native perennial grass species (Elymus glaucus). The climate change treatments had a significant negative effect on total community aboveground biomass (P < 0.01). Crop Sorghum seed production was significantly greater (P< 0.06) under the climate change treatments relative to the controls. Both climate change treatments and the type of biofuel species (native perennial grass, crop sorghum, or Johnsongrass) had significant effects on belowground total fungal biomass (P = 0.004). In particular, soil cores from crop sorghum pots had lower fungal biomass than cores taken from pots that contained only native species or pots that contained Johnsongrass (P< 0.05). Similar trends were observed in the total aboveground biomass data for the wet prairie mesocosms. Continuation of these experiments for several more years will allow us to gain additional insights on how biofuel crop establishment in native plant communities may impact ecosystem services in current and projected climate change scenarios.
