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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Aspects of the ecology of black grouse (Tetrao tetrix) in plantation forests in Scotland

Haysom, Susan L. January 2001 (has links)
Aspects of the ecology of black grouse (Tetrao Tetrix), a species of international conservation concern, in commercial plantation forests were investigated between 1996 - 1998 at three study areas in Scotland. The aim was to identify the species' habitat and area requirements in first and second rotation forestry. The distribution of males was assessed using lek surveys and studied at two spatial scales in the mixed rotation forest landscape of Cowal, Argyll and at two spatial and temporal scales in highland Perthshire - a less afforested region. In addition, a radio-tracking study was undertaken to examine the habitat selection of broods in two first rotation plantations in north Perthshire. Pre-thicket forestry formed a preferred habitat but, in terms of lek distribution, black grouse did not differentiate between first and second rotation pre-thicket habitat patches. Patch size, the total amount of forestry in the area, the proportion that was pre-thicket stock and its level of fragmentation, however, were all correlated with the probability of a location holding a lek and the number of males attending it. Lek isolation reduced the number of males in attendance and increased the likelihood of the lek declining over time. Brood habitat preferences differed from those of adult birds. Broods selected habitats that were 'open' enough to support a rich ground flora and presumably an adequate invertebrate fauna but also 'closed' enough to provide cover, representing a compromise between foraging potential and predation risk. Brood roost sites differed by having shorter trees but a higher degree of cover 1-1.5 metres above the ground. Results from the different study areas and age classes are compared and contrasted and the implications of the research findings for 'black grouse friendly' forestry management are discussed. Finally, suggestions for further work are made.
2

Examining the utility of the random ensemble and remotely sensed image data to predict Pinus patula forest age in KwaZulu-Natal, South Africa.

Dye, Michelle. January 2010 (has links)
The mapping of forest age is important for effective forest inventory as age is indicative of a number of plant physiological processes. Field survey techniques have traditionally been used to collect forest inventory data, but these methods are costly and time-consuming. Remote sensing offers an alternative which is time-effective and cost-effective and can cover large areas. The aim of this research was to assess the capabilities of multispectral and hyperspectral remotely sensed image data and the statistical method, random forest, for Pinus patula age prediction. The first section of this study used spatial and spectral data derived from multispectral QuickBird imagery to predict forest age. Five co-occurrence texture measures (variance, contrast, correlation, homogeneity, and dissimilarity) were calculated on QuickBird panchromatic imagery (0.6 m spatial resolution) using 12 moving window sizes. The spectral data was extracted from visible and near infrared (NIR) QuickBird imagery (2.4 m spatial resolution). Using the random forest ensemble, various methods of combining the spectral and texture variables were evaluated. The best model was achieved using backward variable selection which aims to find the fewest number of input bands while maintaining the highest predictive accuracy. Only five of the original 64 variables were used in the final model (R2 = 0.68). The second part of this study examined the utility of the random forest ensemble and AISA Eagle hyperspectral image data to predict P. patula age. Random forest was used to determine the optimal subset of hyperspectral bands that could predict P. patula age. Two sequential variable selection methods were tested: forward and backward variable selection. Although both methods resulted in the same root mean square error (3.097), the backward variable selection method was unable to significantly reduce the large hyperspectral dataset and selected 206 variables for the model. The forward variable selection method successfully reduced the large dataset to only nine optimal bands while maintaining the highest predictive accuracy from the hyperspectral dataset (R2 = 0.6). Overall, we concluded that (i) remotely sensed data can produce accurate models for P. patula age prediction, (ii) random forest is an effective tool for the combination of spectral and spatial multispectral data, (iii) random forest is an effective tool for variable selection of a high dimensional hyperspectral dataset, and (iv), although random forest has mainly been used as a classifier, it is also a very effective tool for prediction. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.
3

Behavioural ecology of duikers (Cephalophus spp.) in forest and secondary growth, Tai, Cote d'Ivoire

Newing, Helen S. January 1994 (has links)
The behavioural ecology of duikers (Cephalophus spp.) was studied in mature forest and mixed secondary vegetation around TaI National Park, Cöte d'Ivoire. The most common species in both vegetation types was C. maxwelli, followed by C. dorsalis, C. ogilbyi, C. niger, C. zebra and C. lentinki in mature forest, and C. niger, C. dorsalis and C. sylvicultor in secondary vegetation. Population surveys were carried out by a number of methods. Transect censuses by night were found most efficient in mature forest, whereas in secondary vegetation, only pellet transect censuses and drives into nets were possible. C. maxwelli populations were estimated at about 63 km2 in mature forest and 79 km2 in secondary vegetation. Duikers were primarily frugivorous, but the proportion of leaves taken increased in the season of fruit scarcity. Fruit abundance in different habitats increased with the age of the vegetation. Six C. maxwelli in mature forest and four in secondary vegetation were radio-collared to determine ranging patterns and social behaviour. They were diurnal and lived in groups of one male with one or two females and young. Home ranges, which were about 5 ha in size in mature forest and 3.6 ha in secondary vegetation, were defended by males, and the boundaries were marked by latrine areas by both sexes. In mixed secondary vegetation, all habitats were used except open fields and bamboo thickets. Implications for conservation and management are discussed. The continued preservation of mature forest and the control of poaching are essential for the survival of the three rarer species (C. -jentinki, C. zebra and C. ogilbyi). The control of poaching must precede any programme of sustainable harvesting of the more abundant species, which could be carried out in secondary vegetation. Duiker farming may be possible if low-cost sources of fencing and forage can be identified.

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