Understory

The Caspar Creek watershed, in coastal Northern California, features many gullies in its tributary valleys that deliver sediment directly into the perennial channel network. These gullies may help explain rates of sediment delivery in the watershed.Sediment production from gullies responds to pulses in runoff. Resistant elements observed at headcut lips appear to slow the rate of headcut retreat temporarily until the elements are undercut. Headcut retreat occurs at both a gradual rate (0-15 cm yr-1) in most headcuts and at a high rate (>1 m yr-1) in a few. Banks, like headcuts, can fail sud...

Road decommissioning work has been studied in the South Fork Caspar Creek experimental watershed since 1998, when a 4.6 km (2.8 mi) segment of Forest Road 600 was decommissioned. A total of 26 watercourse crossings and eight cross-drain relief culverts were removed, while an additional eight minor crossings remained untreated. A detailed time study documented costs associated with the different treatments implemented at these sites. Gully measurements were made after one and three over-wintering periods. Additional measurements consisted of a longitudinal profile with three to five cross-secti...

Unpaved forest roads are recognized as being the primary source of anthropogenic sediment that is delivered to stream channels in managed forested watersheds in the western United States. Research studies, sediment budgets, and agency monitoring projects in California have shown that road-stream crossings and road segments that drain to crossings are high-risk sites for sediment input. In particular, older "legacy" roads and crossings that pre-date current forest practice rules can be sources of chronic and episodic sediment delivery. Because many California streams provide habitat for listed ...

We developed a predictive model of soil temperature maxima during burning of masticated fuels. The model was well explained by three factors: soil moisture, soil depth, and fuel heat load. Soil texture, in contrast, was unrelated to the temperature profiles, suggesting a single model is applicable for all tested soils (pumice sand, loam, clay). Soil moisture as low as 20% by volume was sufficient to quench soil heating and inhibit the progression of lethal soil temperatures below the surface inch. Thus, burning of masticated fuels when soils are moist is recommended to avoid damaging roots and...

Mastication may moderate fire behavior by reducing fuel bed depth, but high loadings of surface fuels can still result in substantial mortality of residual trees when burned. Even so, it is possible to reduce masticated fuel loads using prescribed fire. In this study, the high soil moisture levels at the time of the burns limited heat penetration into the soil. Under these conditions, the major cause of initial mortality appeared to be due to crown scorch, which can be mitigated by adjusting firing techniques, and burning when air temperature is low.

Ecologically sound fuels management actions are often desired, but ecological and fuels-based management goals may not be synchronous. The MAST treatment generated heavy loadings of woody fuel on the surface, which may inhibit the germination and establishment of shrubs, but also reduced richness of native understory species. Fuel treatments where the masticated material was partially removed by incorporation into the soil or prescribed burning, resulted in greater understory species establishment, but also resulted in higher abundance of fire-stimulated shrubs. The MAST/RX treatment removed t...

The Raider Basin Research Natural Area comprises the upper watersheds of Raider and Hornback creeks. The most distinguishing feature of the RNA is relatively undisturbed stands of old-growth white fir. The white fir stands are characterized by even-aged trees in a closed canopy with more than 80 percent of the overstory being Abies concolor. The sparse herbaceous understory cover typically ranges from 0.2 to 7 percent. Shrubs are uncommon. Other vegetation types within the Raider Basin RNA include whitebark pine forest, northern juniper woodland, montane meadows, subalpine sage scrub, big sage...

The Sacate Ridge Research Natural Area contains excellent representatives of foothill vegetation types such as blue oak woodland, interior live oak woodland, riparian forest, and chaparral. The RNA contains the entire Ross Creek watershed, along with several seasonal streams that drain into Big Creek. The area contains a high concentration of distinctive botanical features including large expanses of blue oak woodland, a diverse type of Ceanothus-dominated chaparral unique to the foothills of eastern Fresno County, two California Native Plant Society (CNPS)-listed rare vascular plants, two CNP...

Scott Camp Creek Research Natural Area lies at the head of Scott Camp Creek, which drains northeast into Siskiyou Lake. It contains four permanent or intermittent small lakes and four marshes/meadows. Scott Camp Creek RNA contains a high concentration of distinctive botanical features including high elevation Port-Orford-cedar stands, four California Native Plant Society-listed rare vascular plants, well-developed fen and aquatic habitats, extensive mixed conifer forest on both gabbro and serpentinite rock types, well-developed alpine talus and scree, montane chaparral, and red fir plant assoc...

The usual analysis of paired-watershed studies is simple and conclusions are consequently very limited. Linear regression models are computed, relating a response in two similar watersheds, before and after a land treatment is applied to one of them. If there is a significant difference between the regression lines, then the treatment is deemed to have had an effect, and the size of the effect is estimated as the average change in response. Sometimes the magnitude of the effect is estimated for different event size classes after testing subsets of events, but the sample sizes are often too sma...