Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references.

This study aims at explaining the distribution and composition of the southern Cape forests, the largest forest complex in southern Africa. These are the only forests in southern Africa which are actively and scientifically managed for their products and values. Population growth due to forestry, agricultural and economic development and a growing tourism industry exerts increasing pressures on the natural environment of the southern Cape coast and therefore affect the dynamics and conservation of the forests. Conservation and sustained utilization of the forests require a sound knowledge of the composition, structure and dynamics of the forests. This study was aimed at an understanding of the biogeography of the forests at the landscape level in order to isolate those variables which contributed to the present distribution and composition of the forests. Determinants of the forest location pattern in the southern Cape were identified as rainfall above 500 mm, which determines the potential limits of the forests, and the bergwind fire pattern, which determines the actual forest distribution. Fires driven by the hot, dry, northwesterly, föhnlike bergwinds interacted with the terrain physiography since prehistorical times and the forests persisted in topographic shadow areas. The largest forests in the area therefore occur on the coastal platform at the foot of the mountains, in the river valleys and on the coastal scarp. Forests in the mountains, with high rainfall, are small and scattered. The results have shown that the bergwind driven fires control the distribution of forests which have important implications for the understanding of forest dynamics and for conservation management of forests in multiple-use management systems. Forest composition at the landscape level was studied by means of plant species lists. A species list for the southern Cape forests was annotated with information on the growth form, breeding system, propagule type, forest type, moisture tolerance, abundance and spread in the study area, and the distribution range in southern Africa, of each species. Analyses of the list showed that the species/family ratios for the southern Cape forest flora are very low, that woody plants have mostly fleshy propagules and herbaceous plants mostly dry propagules, and that several species have adaptations to adverse conditions. The species richness and composition, and floristic similarity and relationships were compared between the southern Cape forest flora and the floras of 13 other forests representing particular geographic regions in southern Africa. Forest size explained relatively little of the variation in species richness of the forests. Stepwise multiple regression analyses indicated that the number of dispersal corridors, the proximity to other forests and mean altitude explained most of the variation in number of woody species, whereas the number of landscape types and dispersal corridors explained most of the variation in number of herbaceous species. The high similarity between the southern Cape forest flora and those of the forests along the escarpment from the eastern Cape to northern Transvaal, and the southern attenuation of species suggest that the forests were once continuous. It is suggested that the Sundays river valley east of Port Elizabeth isolated the southern Cape forests from those to the east already during the Pliocene or earlier.

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The practice of burning large acreages of forest lands in the West for the reduction of fuel hazards is currently accepted by certain land management agencies. Although these prescribed burns frequently accomplish their objectives, little attention has been given to the possible effects these have on watershed conditions. In Arizona, where the demand for water is increasing each year, and where large burning programs are in effect, the influences of burning on water infiltration into the soil is of particular importance. Literature on burning and infiltration relationships is inconclusive. Detrimental and beneficial effects to soils and infiltration capacities have been reported. During the summer of 1963, four sites were selected in the ponderosa pine region of east central Arizona. This study area was located five miles east of McNary on the Fort Apache Indian Reservation, where a large prescribed burning program has been underway since 1948. In July, a light burn and a heavy burn treatment, which approximated prescribed burning and wildfire conditions, respectively, were conducted on each of the four sites. Temperatures during treatments were measured with fusion pyrometers. Surface soil temperatures for the light burns did not exceed 200°F. Maximum temperatures at the soil surface for heavy burns ranged from 350°F. to 550°F. An infiltrometer plot, one by four feet in size, was installed in the center of each treatment area (unburned control, light burn, and heavy burn) on each site. A modified North Fork infiltrometer with constant head tank was utilized to conduct infiltration measurements. The twelve infiltrometer plots remained in place for 25 months, through two overwintering periods. Two infiltration runs were conducted on each plot in late summer,. 1963, and three series of runs were made in both the summers of 1964 and 1965. Infiltration curves were plotted for each run from runoff data programmed into a computer and incremental digital plotter. Infiltration capacity values were obtained directly from these curves. Light and heavy burns produced highly significant decreases in infiltration capacities immediately following burning. No statistically significant differences due to burning were detected between the burning treatments and controls during the second and third summers. It was concluded that the burning programs conducted in late fall on the Fort Apache Indian Reservation, when followed by an overwintering period with freezing and thawing conditions, cause no appreciable effect on watershed conditions. Additional results showed that nearly all the 96 infiltration curves plotted exhibited a pronounced dip after five to fifteen minutes of water application. Soil wettability or a resistance to wetting is felt to be an important factor in causing this depression; however, the extent and practical significance of this new phenomenon is uncertain. Increases in soil pH, carbon, and total nitrogen percentages for the surface two inches of soil were detected immediately following light and heavy burning treatments. These increases were still evident two years after treatment but to a lesser extent. A statistically significant increase in the bulk density of the surface one inch of soil, which was found immediately after burning, was not found after one overwintering period. Changes in the physical and chemical properties of the silt loam soils in the study area following burning were considered to be negligible.

Tree population dynamics were monitored in three tropical rain forest sites in Peninsular Malaysia. The studies involved trees ≥ 10 cm dbh, over 36 years in hill dipterocarp forest at Bukit Lagong, and over 38 and 13 years in lowland dipterocarp forests at Sungei Menyala and Pasoh respectively. Trees were periodically measured for dbh, and mortality and recruitment recorded. Sapling populations at Sungei Menyala were also enumerated at periods separated by about 30 years. The major findings were: decline in tree density over the periods of study were offset by incremental growth in surviving trees, showing that the forests are fully stocked and structurally stable; mortality rates and 'half-life' values were 2.03%, 2.07% and 1.39% yr^-1, and 34.2, 33.5 and 49.9 years for Sungei Menyala, Pasoh and Bukit Lagong respectively; mortality was not correlated with size class for the lowland forests, but there was some evidence for higher mortality in the larger size classes for the hill forest, this possibly being related to soil instability on steep slopes; the risk of death was about 7-8 times greater for trees with negative or no growth, with suppression leading to higher mortality in canopy than in understorey species; recruitment rates to the 10 cm dbh class were 1.32%, 1.46% and 0.85% yr^-1 at Sungei Menyala, Pasoh and Bukit Lagong respectively; dbh increments were linear over long periods for most trees, future size of individuals therefore predictable from one set of measurements; fast-growing mature trees are estimated to be as young as 60 years; variation in species composition over time was slight compared with variation between sites; sapling composition and density at Sungei Menyala changed greatly over 30 years but that for adults remained constant over 38 years, showing that future canopy composition is unlikely to change without catastrophic disturbances occurring.

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The natural history, population dynamics, and community ecology of five small mammals from tropical deciduous and semideciduous (arroyo) forests were studied in western Mexico. I evaluated the influence of habitat heterogeneity and productivity on species diversity, population dynamics, and patterns of resource utilization. I expected higher biomass and species diversity and denser populations in the more complex and productive arroyo forest than in the deciduous forest. Species diversity was higher in the arroyo forest but total biomass, population density and fluctuations were very similar in both forests, despite strong differences in habitat heterogeneity and productivity. Reproduction of all species was associated to seasonality in food availability. Populations of all the species had qualitatively similar temporal patterns of reproduction and population fluctuations because they used similar food resources. Peaks in reproduction and population densities coincided with peaks in food production, suggesting that food availability is a limiting factor. Species differed in variables affecting resource utilization such as body mass, diet, and habitat selection. Results indicate that food resource partitioning and macro and microhabitat preferences permit coexistence. This study suggests that habitat heterogeneity and productivity have a profound influence in population and community ecology of small mammals in the Neotropics.

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