North Platte - Pine Beetle_Water Project - Overview - Section 4

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Water From Colorado's Bark Beetle Forests -Project Overview Elder, Rhoades & Hubbard; USFS Rocky Mountain Research Station; 5/15/08 site conditions. Within each of the four study areas we will conduct two operational- scale comparisons of management alternatives (Fuels Reduction, Forest Regeneration, Watershed Protection and No Action). In summary, two replicate sets of four management alternatives will be established within each of four study areas (e.g. n = 32 management alternative plots total). Because of the influences of topographic aspect on forest composition, environmental conditions and hydrology, we will distribute management comparison plots among north- and south-facing slopes. Treatments will generate distinct levels of surface roughness and environmental conditions between neighboring plots. The manipulative treatments correspond to specific mechanical practices used to regulate the amount and distribution of logging debris and seed bed conditions. The Watershed Protection treatment is comparable to a stem-only harvest, lop and scatter slash operation that retains cut branches and tops on site. Removal of logging slash associated with the high activity fuels that control surface fire behavior (e.g. 1-hr, 10-hr, and 100-hr fuels) will be removed in the Fuel Reduction treatment, similar to the result of a whole-tree harvest operation. The Forest Regeneration treatment combines whole-tree harvest fuel reduction with post-harvest mechanical scarification to expose a mineral soil seed bed. The three manipulative treatments will be randomly assigned to 30 x 30 m plots and established in conjunction with harvesting operations. A 30 x 30 m No Action treatment plot will be located in the adjacent uncut stand. Hydrologic Measurements We cannot measure changes in runoff due to treatment directly at the hillslope or plot- scale because there are no gauges at the study plots and there are no long-term records for comparison of pre- and post-treatment runoff. However, changes in snow accumulation, related to changes in vegetation, have been shown by many studies to have high correlations with altered runoff at the basin scale (Troendle and King 1985; Troendle and Nankervis 2000). We will use spatially intensive measurements of snow accumulation at the study sites to estimate differences in water available for runoff between the management treatments and the uncut control sites. At sites where vegetation remains (control and understory), transpiration losses will be estimated from empirical studies of similar areas and this volume will be removed from the water available for runoff. We will use soil moisture measurements to validate infiltration of snowmelt and relate differences in observed soil moisture to differences in snow accumulation. The final product will be an estimate of the water available for runoff from each study plot, both treated and untreated. Surface roughness is the primary control of on-site snow retention (Liston and Sturm 1998; Liston et al. 2002; Heimstra et al. 2002). In the dry air masses of the interior western mountain regions blowing snow sublimates quickly (Schmidt 1982). Removing vegetation through any disturbance alters roughness and on-site snow retention capabilities. We will measure surface roughness along transects by quantifying vegetation height above the ground at fixed intervals along established transects in all four study area conditions. Snow accumulation will be measured along the same transects at peak accumulation to determine the relationship between surface roughness