Treesearch

Fotiar moisture was monitored for five conifers and associated understory vegetation in Pacific Northwest forests. Decline in foliar moisture of new foliage occurred over the dry season, while less variation was evident in older foliage. Late season foliar moisture ranged from 130 to 170%. In riparian-upland comparisons, largest differences were found for understory vegetation, with less variation evident for overstory trees. Minimum foliar moisture values of 100-120% are appropriate to use in crown fire risk assessment for the Pacific Northwest.

Projected increasing demands for timber coupled with reduced harvests on public lands have led to concern among some forest policymakers regarding the adequacy of future U.S. timber supplies. One question concerns the likelihood that prevailing market incentives will induce industrial and nonindustrial private landowners to intensify forest management.

Estimation of the amount of carbon stored in forests is a key challenge for understanding the global carbon cycle, one which remote sensing is expected to help address. However, estimation of carbon storage in moderate to high biomass forests is difficult for conventional optical and radar sensors. Lidar (light detection and ranging) instruments measure the vertical structure of forests and thus hold great promise for remotely sensing the quantity and spatial organization of forest biomass. In this study, we compare the relationships between LIDAR-measured canopy structure and coincident...

We explore the thesis that stochasticity in successional-disturbance systems can be an agent of species extinction. The analysis uses a simple model of patch dynamics for seral stages in an idealized landscape; each seral stage is assumed to support a specialist biota. The landscape as a whole is characterized by a mean patch birth rate, mean patch size, and mean lifetime for each patch type. Stochasticity takes three forms: (1) patch stochasticity is randomness in the birth times and sizes of individual patches, (2) landscape stochasticity is variation in the annual means of birth rate...

Three thinning treatments (thinned to 3.7 by 3.7 m, thinned to 4.3 by 4.3 m, and an unthinned control treatment with nominal spacing averaging 2.6 by 2.6 m) were installed in a 10-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) plantation growing on a low-quality site at the Wind River Experimental Forest in southwest Washington. Two years after thinning, two fertilizer treatments were superimposed on the design (0 and 224 kg per ha of nitrogen applied as ammonium nitrate). Diameter growth increased with increasing spacing throughout the 6-year study period, and it was also...

Because of concern over widespread population declines, the distribution, stand conditions, and health of whitebark pine (Pinus albicaulis Englem.) were evaluated along the Pacific Crest National Scenic Trail on the Umpqua National Forest. Whitebark pine occurred on 76 percent of the survey transects. In general, whitebark pine was found in stands with lower overall densities and fewer late-seral species, particularly Shasta red fir (Abies magnifica var. shatensis A. Murr.) and mountain hemlock (Tsuga mertensiana [Bong.] Carr.). Whitebark pine stocking differed widely, from less than 1 up...

The effects of partial cutting on species composition, new and residual-tree cohorts, tree size distribution, and tree growth was evaluate on 73 plots in 18 stands throughout southeast Alaska. These partially cut stands were harvested 12-96 years ago, when 16-96% if the former stand basal area was removed. Partial cutting maintained stand structures similar to uncut old-growth stands, and the cutting had no significant effects on tree species composition. The establishment of new-tree cohorts was positively related to the proportion of basal-area cut. The current stand basal area, tree...

A large number of lightning-caused fires burned across the western United States during the summer of 2000. In a previous study, the authors determined that a simple index of low-level moisture (85-kPa dewpoint depression) and instability (85–50-kPa temperature difference) from the Spokane, Washington, upper-air soundings was very useful for indicating the likelihood of ‘‘dry’’ lightning (occurring without significant concurrent rainfall) in the Pacific Northwest. This same method was applied to the summer-2000 fire season in the Pacific Northwest and northern Rockies. The mean 85-kPa...

We (i) quantified effects of skidder yarding on soil properties and seedling growth in a portion of western Oregon, (ii) determined if tilling skid trails improved tree growth, and (iii) compared results with those from an earlier investigation in coastal Washington. Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were hand planted at eight recent clearcuts in skid ruts in either nontilled or tilled trails, in adjacent soil berms, and in adjacent logged-only portions. Four and 5 years after skidding, rut depths averaged 15 cm below the original soil surface; mean fine-soil...

Knowledge of the community structure of ectomycorrhizal fungi among successional forest age-classes is critical for conserving fungal species diversity. Hypogeous and epigeous sporocarps were collected from three replicate stands in each of three forest age-classes (young, rotation-age, and old-growth) of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) dominated stands with mesic plant association groups. Over four fall and three spring seasons, 48 hypogeous and 215 epigeous species or species groups were collected from sample areas of 6300 and 43 700 m2, respectively. Cumulative...