Develop and test Mojave native plant materials

Engel, Cayenne

Sites were sampled for three years, sampling red brome biomass, community composition, air temperatures, soil moisture, and soil nitrogen availability. Carbon treatments reduced soil available nitrogen, and also reduced red brome (RB) biomass by an average of 33%. RB biomass was greatest in the 70% light reduction plots, while consistent across all other light reduction treatments. Therefore, we did not see competitive pressure by reducing light availability, and may have seen the facilitation effects of reducing environmental stress by reducing maximum temperatures especially through the hottest months of the year. There were no interactive effects of carbon treatment and light reduction treatments on red brome biomass. Carbon addition appeared to reduce native species abundance and richness along with the reduction in RB, with fewer native species per plot, indicating a possible side effect of a treatment effective against RB. Overall, emergence rates of most of the native annual species were low and patchy among treatments. Emergence was too low to support statistical power for A. tessellata, D. pinnata, L. tenella, and S. columbariae. There was no overall relationship between outplant density, species identity, or plant size and red brome density. However, two species, Baileya multiradiata and Encelia farinosa exhibited a positive relationship between outplant density and red brome density. While RB abundance increased with outplant density for those two species, there were no relationships between plant community composition and outplant density or identity. We found sparse but statistically significant relationships between outplant density and richness and diversity (not ecologically significant). Due to practicality and necessity outplant densities are relatively low, we observed little evidence for using outplanting as a means of controlling red brome abundance. Rather, we only saw evidence of facilitation.