Project Number: 2070-22000-004-02
Start Date: Sep 01, 2010
End Date: Sep 01, 2014
Based on the results of a number of studies funded by the GBNPSIP, this study will examine the direct and indirect effects of disturbance, safe site availability, drought, crested wheatgrass and cheatgrass abundance, seeding depth, and seeding rate on forb establishment and diversity in a crested wheatgrass stand in southeast Oregon. Classical experimental designs and statistical tests do not allow the importance of direct and indirect effects and factor interactions to be easily evaluated. I will use structural equation modeling to quantify the relative importance of each of these factors and their interactions for forb establishment. For this experiment, 300, 6m x 6m plots will be established. One of five disturbance treatments (crested control) will be applied to each plot including: undisturbed, light till, herbicide, 1-way disking, 2-way disking. Half of these plots will be drill seeded with a rangeland drill. Seeds in the other half of the plots will be placed by hand in drill rows and buried 1/8 of an inch deep. Half of the plots also will receive supplemental watering in spring. Plots will be seeded at ½x, 1x, or 2x the recommend forb seeding rate. Eight forb species will be used based in recommendations from the GBNPSIP and land managers. Response variables including forb germination and establishment as well as first, second and third year survival and fecundity. Treatment effects on crested and cheatgrass density and cover and soil moisture availability will be quantified. The relative importance of each factor for forb establishment will be determined using path analysis and structural equation modeling in SAS. Formerly 5360-22000-003-01R (12/10).