Hydrology, erosion, plant, and soil relationships after rangeland wildfire

Spaeth, Kenneth E.; Pierson, Frederick B.; Robichaud, Peter R.; Moffet, Corey A. 2007. Hydrology, erosion, plant, and soil relationships after rangeland wildfire. In: Sosebee, Ronald E.; Wester, David B.; Britton, Carlton M.; McArthur, E. Durant; Kitchen, Stanley G., comps. Proceedings: Shrubland dynamics -- fire and water; 2004 August 10-12; Lubbock, TX. Proceedings RMRS-P-47. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 62-68.

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Abstract: Wildfire is an important ecological process and management issue on western rangelands. Fire suppression activities in the past century have increased the number and severity of wildfires, resulting in increased soil erosion and decreased water quality. Many infiltration studies on rangeland have shown that litter and vegetation cover protect the soil and enhance infiltration. After fire, water repellency is typically found on the soil surface or a few centimeters below and is also common on unburned rangelands and dry soils conditions. However, the causal agents of water repellency are different for burned and burned conditions. Rainfall simulation studies were conducted for 3 consecutive years immediately following a catastrophic wildfire in Denio, Nevada, in 1999. Study sites were chosen on northfacing hillslopes (35 to 40 percent slope) where the vegetation was dominated by mountain big sagebrush (Artemisia tridentata ssp. vaseyana). The objective of this study was to use indirect gradient analysis on the 1999 data to evaluate and summarize pertinent relationships between vegetation, soil, topographic features, infiltration, runoff, sediment production, and microsite distinction (shrub coppice and interspace) on burned and unburned areas. The first ordination (strategy 1) used four infiltration parameters and the results were unexpected. In the multivariate context, higher infiltration trends were associated with the burned treatment compared to the unburned treatment. Water repellency on the burned sites was apparent at the soil surface; however, it appears that repellency was also a significant factor on the unburned area. Water repellency in the unburned treatment was likely caused by assorted litter buildup (up to 11,605 kg/ha) in > 80-year stands (sagebrush duff and grass in the shrub coppice areas and grass litter in the interspace). The second ordination (strategy 2) involved the same four infiltration parameters, but specifically used plots from the burned treatment. More runoff and sediment was associated with the burn shrub coppice plots; in contrast, higher infiltration capacity in the burned interspace. The third ordination (strategy 3) was based on plant canopy cover by species. Discrete taxa of native grasses, forbs, and shrubs were correlated with infiltration, runoff, and sediment loss on burned and unburned sites. On the unburned sites, water repellency and higher runoff was correlated with Sandberg bluegrass (Poa secunda), bluebunch wheatgrass (Pseudoroegneria spicata), and western aster (Symphyotrichum ascendens). Greater infiltration capacity was correlated with increasing cover of Idaho fescue (Festuca idahoensis) and mountain big sagebrush. Future analysis will evaluate conditions after the first years growing season and beyond.

Moscow FSL publication no. 2007j