Treesearch

In a low-phosphate medium fosetyl-Al showed a much higher activity in vitro against Phytophthora than previously reported in the literature. Both fosetyl-Al, and more particularly phosphorous acid (H3PO3), were highly inhibitory in vitro against several species of Phytophthora. Phosphorous acid was much less inhibitory in vitro against Pythium and had only low activity against a selection of non-oomycetous fungi. The EC50 values for an isolate of Phytophthora cinnamomi, cultured on a low phosphate medium, were 0.05 PO3 meq of H3PO3 (4 μg/mi) and 0.45 PO3 meq of fosetyl-Al per liter (54...

The relationship between measures of site disturbance and erosion resulting from timber harvest was studied by regression analyses. None of the 12 regression models developed and tested yielded a coefficient of determination (R2) greater than 0.60. The results indicated that the poor fits to the data were due, in part, to unexplained qualitative differences in disturbance associated with cable and tractor yarded harvests. Improved prediction might be achieved by weighting each elementary area of disturbance by the sine of its slope for estimates of surface erosion and by both the sine of...

Abstract - Solution and landsliding, the dominant erosion processes in undisturbed forested mountainous watersheds, are both influenced by subsurface drainage. Biological processes that generate organic acids accelerate loss of dissolved solids by promoting the dissolution of primary minerals in granitic rock. These organic acids can also disperse the secondary minerals, kaolinite and ferric hydroxide. This accelerates erosion by subsurface drainage through suffusion and piping, particularly in well-drained, gap-graded soils. Solution, suffusion, and piping on steep slopes can promote...

Hardware and software supporting a sediment sampling procedure--Sampling At List Time (SALT) have been perfected. SALT provides estimates of sediment discharge having improved accuracy and estimable precision. Although the greatest benefit of SALT may accrue to those attempting to monitor ""flashy"" small streams, its superior statistical properties should improve any suspended sediment monitoring program

Cased boreholes on the Redwood Creak basin in northwestern California were surveyed semiannually by inclinometer from 1974 to 1982. Regressions were calculated between borehole displacement and an antecedent precipitation index (API) variable.

The organic constituents of water extracts from Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) roots that cause kaolinite dispersion were investigated. The dissolved organic matter was fractionated according to molecular size and chemical characteristics into acids, neutrals, and bases of the hydrophilic and hydrophobic groups.

Methods for assessing the impact of fire on forest recreation were studied in a literature search and an experiment. Contingent market valuation appeared the most promising. This direct, economic approach uses personal interviews and sets up a hypothetical market transaction in which values are estimated. In an illustrative application of this method, respondents were shown sequences of photographs of recreation sites depicting scenes before and after a fire. They were a asked about their preferences among the scenes depicted and about their willingness-to-pay an entrance fee to the...