Treesearch

Abstract - When monitoring suspended sediment for watershed research, reliable and accurate results may be a higher priority than in other settings. Timing and frequency of data collection are the most important factors influencing the accuracy of suspended sediment load estimates, and, in most watersheds, suspended sediment transport is dominated by a few, large rainstorm events. Automated data collection is essential to effectively capture such infrequent events. Turbidity Threshold Sampling, a method that distributes sample collection over the range of rising and falling turbidity...

Tributary and headwater valleys in the Caspar Creek watershed,in coastal Mendocino County, California,show signs of incision along much of their lengths.An episode of incision followed initial-entry logging which took place between 1860 and 1906. Another episode of incision cut into skid-trails created for second-entry logging in the 1970's.

This is the first issue of the State Forests Research and Demonstration program's newsletter. With this initial issue we have chosen to highlight the Caspar Creek Watershed Study and the contributions it is making toward a better understanding of the impacts of forest management on the environment.

Abstract - Caspar Creek Experimental Watersheds were established in 1962 to research the effects of forest management on streamflow, sedimentation, and erosion in the rainfall-dominated, forested watersheds of north coastal California. Currently, 21 stream sites are gaged in the North Fork (473 ha) and South Fork (424 ha) of Caspar Creek. From 1971 to 1973, 65% of the timber volume in the South Fork was selectively cut and tractor yarded, and from 1985 to 1991, 50% of the North Fork basin was harvested, mostly as cable-yarded clearcuts. Three unlogged tributaries serve as controls.

Abstract - Automated data collection is essential to effectively measure suspended sediment loads in storm events, particularly in small basins. Continuous turbidity measurements can be used, along with discharge, in an automated system that makes real-time sampling decisions to facilitate sediment load estimation. The Turbidity Threshold Sampling method distributes sample collection over the range of rising and falling turbidity values and attempts to sample all significant turbidity episodes. A data logger activates a pumping sampler when specified turbidity conditions are met. The...

Model-based stratified sampling is illustrated by a case study of stemflow volume in a redwood forest. The approach is actually a model-assisted sampling design in which auxiliary information (tree diameter) is utilized in the design of stratum boundaries to optimize the efficiency of a regression or ratio estimator. The auxiliary information is utilized in both the design and estimation phases. Stemflow and its variance were modelled as powers of diameter and a generalized non-linear least squares model was used to estimate the exponents and to impute values for missing storm events prior...

The concern of this paper is obtaining baseline values for the number of forest fires as a function of time and location and other explanatories. A model is developed and applied to a large data set from Federal lands in the state of Oregon. To proceed the data are grouped into small spatial-temporal cells (voxels). Fires are rare so there are many of these voxels with no fires. In fact there are so many such cells that in the analyses presented a sample is taken to make the work manageable. The paper sets down a likelihood for the sampled data and fits a generalized additive model...

The San Dimas Experimental Forest (SDEF) was established in the early 1930s to document and quantify wildland hydrology in the semiarid chaparral-covered steeplands of southern California. Concomitantly, the nearly seventy years of accumulated watershed research in this fire-prone ecosystem has produced invaluable information on post-fire erosion and the effectiveness and consequences of post-fire erosion control treatments. On average, first-year post-fire watershed sediment yield is 35 times greater than comparable unburned annual levels. This accelerated erosion can cause site degradatio...

The San Dimas Experimental Forest was established in 1934. A large database of fire history, and stream flow exists for several locations within the forest. San Dimas was selected as a perfect example of the hydrology, geology, and ecology of the mountains of southern California. As such the long-term data set provides the best examples available of rainfallrunoff relationships in a mountainous Mediterranean climate. One of the most important ecological processes operating at San Dimas is the frequent stand replacing fires that occur approximately every 40 years. The effect of fire on...

The mountains of southern California have some of the highest rates of atmospheric deposition in the world. Over the last two decades a consistent picture of unusually high levels of nitrate in streams has been painted using field sites at the San Dimas Experimental Forest (SDEF) and across southern California. Within the context of southern California, three major processes appear to drive the observed variability in nitrate concentrations in streams. First, chronic atmospheric nitrogen deposition leads to high nitrate concentrations. Second, the profound inter-annual variability in...