Apr 20th, 1:00 PM - 4:00 PM
Influence of Biological Soil Crust and Litter on Bromus Tectorum Establishment Under Natural Conditions
Dr. Marcelo Serpe
Previous experiments under growth chamber conditions indicated that a biological soil crust dominated by the moss Bryum argenteum decreased the establishment of the invasive weed Bromus tectorum (cheatgrass). We are presently studying whether a similar phenomenon occurs in a natural setting. For this purpose, we prepared trays with bare soil and soil covered with biological soil and distributed B. tectorum seeds over these surfaces. Furthermore, we covered half of the trays with B. tectorum litter to investigate the effect of the litter on seed germination and on the photosynthetic performance of the biological soil crust. The trays were placed at the Idaho Botanical Gardens during the summer of 2008. Shoot biomass of B. tectorum and chlorophyll fluorescence parameters of the biological soil crust were determined on samples collected on October 2008 and February 2009. Shoot biomass was about half on biological soil crust than on bare soil. In contrast, the presence of litter led to an increase in the biomass of B. tectorum. For the samples collected on October 2008, the Fv/Fm ratio of the crust determined by chlorophyll fluorescence was not affected by the presence of litter. However, prolonged exposure to litter lowered the photosynthetic efficiency of the crust. On February of 2009, the average Fv/Fm values of crust covered with litter and control crust were 0.36 and 0.76, respectively. We plan to make more measurements on May and July 2009 to ascertain the results observed and to analyze the effects of the treatments on the yield of B. tectorum seeds.