Altitudinal zonation of rain forests was investigated on Bukit Belalong (913m), Brunei. Mean annual rainfall was 4100mm at 45m and 5500mm at 913m. Mean annual temperatureswere 25.7°C (45m) and 21.8°C (913m). Three 0.25ha plots were set up at each of three altitudes. At 200m and 500m there was evergreen lowland rain forest and at 850m there was lower montane rain forest (LMRF). The Dipterocarpaceae had the highest proportion of basal area throughout, but their importance declined in the LMRF where the Fagaceae, Myrtaceae and Lauraceae were increasingly important. Soils in the LMRF were more organic and had higher concentrations of total nitrogen and phosphorus and the soils from 500m were the most acid and least base saturated. Rates of nitrogen mineralisation and soil concentrations of inorganic nitrogen did not differ significantly among altitudes. The rates (t ha-1 yr-1) of total small litterfall and leaf litterfall were significantly lower in the LMRF (10.6 and 7.9 at 200m; 10.5 and 7.9 at 500m; 8.3 and 6.0 at 850m). Litterfall nutrient concentrations were similar among altitudes, but smaller quantities of litterfall nutrients were cycled at 850m. The mass (t ha-1) of the small litter layer was similar throughout (5.2 at 200m; 6.1 at 500m; 5.2 at 850m) but leaf litter kL values were lower at 850m (2.4 at 200m; 2.4 at 500m; 2.0 at 850m). Fine root (<5mm) mass (t ha-1) in the top 100cm of soil was 8.3 (200m); 12.0 (500m); 10.6 (850m). Rates (t ha-1 yr-1) of fine root growth (estimated by ingrowth bags) were 0.9 (200m); 2.2 (500m); 0.5 (850m). A bioassay experiment using rice was made at 30m and 913m. Nutrients were more limiting in the montane soil, but climate was of overriding importance for rice growth. It seems that the LMRF is not nutrient limited and the lower temperatures at 850m are the primary cause of the change in species composition and reduction of stature there.

In Canada’s eastern boreal forest region, partial-harvest silviculture has garnered increasing support for maintaining wildlife species and habitat structure associated with late-successional forests. If late-successional species can find suitable habitat in managed stands that retain a certain number, type, and pattern of live trees, then partial harvesting might represent a viable tool for maintaining species associated with old and complex forests. I used several indirect forms of inference to evaluate whether late-successional vertebrate species can be maintained within partially harvested stands in the eastern boreal forest. A meta-analysis of studies across North America showed that no bird species decreased in abundance by half where light harvesting retained at least 70% of live trees. However, adverse effects occurred at lower levels of retention, with some bird species unlikely to use harvested stands with less than 50% retention until appropriate habitat structure returned. A spatially explicit stand dynamics model showed that while partial harvesting can promote development of understory saplings, downed wood, and heterogeneity, it can also induce long-term decreases in the abundances of large trees and snags. Consequently, species dependent on the latter, such as brown creepers (Certhia americana) and northern flying squirrels (Glaucomys sabrinus), were projected to be more susceptible to partial harvesting than those associated with other types of structure. At a more detailed scale, a neighbourhood model developed from live-trapping data revealed that southern red-backed voles (Myodes gapperi) exhibited local associations with several late-successional features within boreal mixedwood stands. Their associations with some features depended on stand-level habitat conditions, which suggested that vole habitat in managed stands could be improved by retaining live trees and downed wood. A spatially explicit model of optimal home range establishment that incorporated these relationships fit vole abundance data marginally better than an aspatial habitat model. When the home range model was applied to simulated partially harvested stands, it predicted that spatial heterogeneity could have a positive effect on vole abundance, but only at harvest intensities of 70-90% with suppressed shrub cover. With careful attention to issues such as these, partial-harvest silviculture could be useful in maintaining vertebrate biodiversity within eastern boreal forests.

Carbon dioxide is one of the major greenhouse gases being cycled by forests. Mature boreal forests are often carbon sinks, however, following disturbance, forests can become carbon sources. Three forest sites in central Saskatchewan burned in 1977 (F77 site), 1989 (F89 site), and 1998 (F98 site) were studied using eddy covariance to obtain measurements of the energy, carbon, and water budgets. Latent heat flux density increased gradually over time at F98 but remained lower than F77 and F89. Weekly net ecosystem production was lower at F98 than at F77 and F89. F77 lost 40 g C m-2 and 79 g C m-2 in 2004 and 2005, respectively. F89 gained 177 g C m-2, 113 g C m-2, and 88 g C m-2 in 2003, 2004, and 2005, respectively. F98 lost 5 g C m-2, 17 g C m-2, and 52 g C m-2 during these three years, respectively.

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No description available.

Thesis (Ph. D.)--Oregon State University, 1988. / Typescript (photocopy). Includes bibliographical references (leaves 144-157). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 1988. / Typescript (photocopy). Includes bibliographical references (leaves 127-138). Also available on the World Wide Web.

Thesis (M.S. - Watershed Management)--University of Arizona. / Includes bibliographical references.

Thesis (M. S. - Renewable Natural Resources)--University of Arizona, 1990. / Includes bibliographical references (leaves 52-54).

Thesis (M.S.)--Oregon State University, 1969. / Typescript. Includes bibliographical references (leaves 96-101). Also available on the World Wide Web.