PARENT SESSION
Contributed Oral Session 11: Invasive Species: Arid Lands
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 520 A, Level 5, Palais des congrès de Montréal
Sugar application and nitrogen pools in Wyoming big sagebrush communities and exotic annual grasslands.
Witwicki, Dana*,1, Doescher, Paul1, Pyke, David2, Perakis, Steven2, 1 Oregon State University, Corvallis, OR2 United States Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR
ABSTRACT- Within Wyoming big sagebrush (Artemisia tridentata ssp wyomingensis) communities of the Great Basin, lands dominated by the exotic annual grasses cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae) are increasing at an alarming rate. Sugar applications, which reduce available soil N, have been suggested as a way to give native vegetation a competitive advantage over exotic annual grasses when reseeding after a fire. The main objective of our study was to understand how sugar application affects N pools in both Wyoming big sagebrush and exotic annual grass communities at 6 sites in eastern Oregon and southwestern Idaho. Each site contains pairs of Wyoming big sagebrush and exotic annual grass communities in close proximity. Pairs were carefully selected with similar soil types, precipitation, elevation, aspect, slope and ecological sites (i.e. potential vegetation and production). At the beginning of the cheatgrass growing season (late fall), three treatments (sugar, nitrogen or control) were applied randomly to plots in each community at each site. One week after application, sugar reduced inorganic N in the top 10cm of soil to lower than detectable levels (<0.1ppm) in over 90% of plots. Soil inorganic N remained nearly as low six months later (during peak cheatgrass biomass). The sugar treatment decreased cheatgrass biomass 80% compared to the control, which was twice as much as the decrease in sagebrush biomass. Additional data using a 15N tracer supports these trends in soil and plant N pools.
Key words: sugar application, Bromus tectorum, Artemisia tridentata, nitrogen