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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.
251

Indigenous forests of Mpumalanga Province (South Africa); patterns and processes for inclusion in a systematic conservation plan

Lotter, Mervyn Charles 01 July 2014 (has links)
Systematic conservation planning (SCP) relies fundamentally on spatial information about the distribution of biodiversity, and applying the principles of conserving a representative sample of biodiversity pattern that can persist over time, and the translation of conservation objectives into explicit quantitative targets. My thesis focuses on the development of appropriate data sets to include Mpumalanga Province’s indigenous forests (South Africa) within a regional SCP. My aim is to investigate and describe forest pattern and ecological processes at appropriate scales to inform a provincial SCP assessment. A large data set consisting of 506 plots of 20 m x 20 m sampled the indigenous forests in and around Mpumalanga to inform the identification of SCP forest features and conservation targets. The current National Forest Classification (NFC) identifies forest types at a national scale, inappropriate for a regional assessment. I identified a hierarchy of forest subtypes, nested within the NFC based on Flexible beta (β = –0.25) clustering and Bray-Curtis resemblance measure. This classification procedure is selected after a detailed evaluation of available methods to identify a robust numerical classification technique, optimising on statistically identified faithful species. Fourteen forest subtypes are distinguished within three national forest types. I propose that the Wakkerstroom Midlands Forest Subtype be embedded within the Northern Highveld Forest Type, and not the Low Escarpment Mistbelt Forest Type as is currently recognised in the NFC. The proposed forest subtypes are described in terms of dominant plant families and genera, growth forms, seasonality or leaf retention characteristics, and the proportion of forest dependant species. A total of 125 plant families, 375 genera and 619 species are identified to occur in the Mpumalanga forests, with the most abundant species per family being Rubiaceae (33 plant species), Fabaceae (26), Celastraceae (25), Orchidaceae (23), Euphorbiaceae (22), Aspleniaceae (21) and Apocynaceae (20). 76% of all forest plant species are obligate forest species and 80% of all tree cover is evergreen. The identification and understanding of underlying ecological processes is informed by the analysis of three scales of environmental variables and geographic space on forest composition using variation partitioning and ordination. I propose the application of semivariogram analysis to categorise environmental variables into three scales of influence (local, regional and supra-regional scales). The largest fraction of variation is explained by the regional variables (45%), followed by the effects of supra-regional (21%) and local variables (19%). Using the full floristic data, both the environmental and geographic variable matrices accounted for 55% of observed variation. Geographic space (23%) partially explains the important role of dispersal in influencing variation in species patterns across all forest strata, even in the herbaceous stratum where the substantial contribution of dispersal is unexpected. My analysis provides insight into the relative contributions of environmental variables and the scale of their influence, and highlights the importance of dispersal in explaining forest vegetation patterns in Mpumalanga. The use of ecological processes within SCP is still in its infancy, particularly in light of the threat of climate change. I propose a new method based on graph theory that incorporates dispersal distance to identify connectivity importance values for each forest patch based on their contribution towards landscape connectivity. Minimum patch distance is informed through a dispersal range ensuring 75% of flora can disperse between patches. The connectivity analysis supports resilience and persistence in SCP scenarios. Finally I needed to set quantitative targets for the pattern and process features for their inclusion within a SCP. With an overarching goal of ensuring that at least 75% of all species are represented by at least one individual within each forest subtype in a SCP, I utilised the Species Area Relationship (SAR) to determine the slope of the relationship and to estimate the proportion of area required to represent 75% of species. The number of plots in my data set was low for certain forest subtypes, which necessitated an approach of utilising highest values from estimators of species richness and integrating forest subtype targets with those for forest types of a higher level in the NFC. I integrate forest connectivity into pattern targets as a precautionary approach given the vulnerability of naturally disconnected forest patches and the importance of emigration and immigration of plant diaspores in maintaining forest composition across a network of small forest patches. The resulting forest pattern targets ranged between 24.9% and 49.7% for forest subtypes, with a mean value of 34.8%. I also propose forest process targets for more spatially fixed processes, such as the important forest patches supporting connectivity, as well as the spatially flexible buffers around each priority forest patch. Spatially fixed forest process targets are set at 100% and for spatially flexible forest processes the targets are set at 60% of original extent. Consideration also needs to be given to design criteria that can assist in developing a framework for prioritising conservation actions based on vulnerability and irreplaceability.
252

Estimating volume and value on standing timber in hybrid poplar plantations using terrestrial laser scanning : a case study

Barnett, Jennifer S. 25 May 2012 (has links)
Terrestrial laser scanning (TLS) may provide a way to increase timber value recovery by replacing manual timber cruising with a simple-to-use, cost-effective alternative. TLS has been studied in several trials worldwide. Past studies have not compared TLS based estimates with mill estimates of stem value and volume. Three differently stocked stands of hybrid poplar were selected for diameter, stem sinuosity and height measurement using manual cruising and TLS. Selected trees were harvested and transported to a mill where they were scanned and then processed into lumber and chips. Data gathered using both manual and TLS methods were used to obtain stem volume and value estimates to compare with mill estimates. Results indicated that TLS diameter measurements were more accurately matched to mill and manual measurements up to about 7.5 meters on the stem than above 7.5 meters on the stem in all three stands. Stem curvature comparisons indicated that the variation between TLS and mill centerline measurements was similar to the variation between repeat mill scan measurements of the same stems. Using TLS as a pre-harvest inventory tool showed that additional revenue could be obtained from the reallocation of saw-log and chip log volume to veneer logs of various sizes in all three stands. It was also shown that the sampling error required to estimate stand value was greater than was required to estimate stand volume within the same error limits. / Graduation date: 2012
253

Understanding the present and historic forest resource use of the Ntabamhlope indigenous state forest by rural communities.

Mthimkhulu, Oscar. January 2009 (has links)
Ntabamhlophe indigenous state forest is the focus study area. It is one of the forests that are found along the Drakensberg mountain range in KwaZulu- Natal province in South Africa. It is a proclaimed forest of approximately 50ha in extent. The Ntabamhlophe indigenous state forest was formerly called Monk’s Cowl State Forest, (Monk’s Cowl State Forest - iNtabamhlophe) situated in central uKhahlamba Drakensberg Park World Heritage Site, KwaZulu-Natal, South Africa. This forest is located on communal land. In many parts of the world, indigenous forests face growing threats and pressures. Internationally this has resulted in approximately 9.4 million hectares being lost by 1990. Indigenous forests play an important role in ecosystem processes. They are associated with a range of products and processes that support the livelihood of millions of people around the world. Forests cover more than 3 000 km2 or 0.1% of the land surface of South Africa. Furthermore, due to the lack of appropriate management programmes, South Africa has contributed its share to indigenous forest loss. Approximately 76% (3240ha) of the Drakensberg Montane forest is formally protected South Africa’s geographical positioning is such that it has historically had a smaller extent of forests. The future of South Africa’s remaining indigenous forests depends partly on the values ascribed to them by local communities. The study objectives were, (i) to understand the values and perceptions of the community towards the existence and future management of the Ntabamhlophe indigenous state forest, and (ii) to determine the different types of forest products and resources used by the community and their values to the users (cultural, spiritual or economic values). To understand Ntabamhlophe community’s indigenous forest resource use, values and perceptions, a qualitative survey method was used. This was conducted by using focus group techniques. The use of focus groups provided an insight into qualitative data. The technique combined both wise counsel and focus group workshops. The use of this technique aimed at drawing upon respondents’ attitudes, feelings, beliefs, experiences and reactions. The questionnaire design was based on the structures of other studies, on user attitudes and values relating to forest resources. The study revealed that the community ascribes high values to the indigenous forest, however they do not have a proper forest management system in place. The following were regarded as the major threats facing Ntabamhlophe forest resources: crime, uncontrolled and excessive burning, uncontrolled harvesting of indigenous medicinal plant and fuelwood, deforestation (clearing forests for plantations, e.g. vegetable crops and Cannabis sativa). Illegal hunting, soil erosion, and inappropriate forest management systems (nonexistence) were all considered by community representatives as serious threats to the survival of this indigenous forest. The findings also revealed that there is a lack of capacity and skills, appropriate stakeholder representation and coherent community leadership to pursue Ntabamhlophe Mountain and forest conservation initiatives. Given the circumstances, there is an apparent lack of confidence on the part of the community to confirm their natural resource conservation priorities. The community representatives recommended that the current uncontrolled activities be prohibited. They also had a strong belief that the forest should be protected through a cooperative management system involving Ezemvelo KZN Wildlife, the Traditional Authority, the Department of Water Affairs and Forestry and Imbabazane Local Municipality. The focus group indicated that they had a very high future benefit expectation of activities such as education, water, cultural, biodiversity, spiritual upliftment, tourism, craft and free access (Table 6). They also indicated that gathering medicinal plants and fuelwood was very common. Educational benefit was regarded as the most important of all, followed by tourism and biodiversity conservation. / Thesis (M.Env.Dev.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.
254

Population dynamics of tropical forest trees

Manokaran, N. January 1988 (has links)
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.
255

Inter-specific competition in Nigerian rain forest and its bearing on silviculture

Keay, Ronald William John January 1963 (has links)
No description available.
256

Modelling deforestation and land degradation in the Guinea highlands of West Africa using remote sensing and geographic information systems.

Gilruth, Peter Thomas. January 1991 (has links)
A dynamic spatial model of deforestation and land-use change was developed from remotely sensed data for the Fouta Djallon mountain range in the Republic of Guinea, West Africa. The objective was to simulate patterns of land clearing for shifting cultivation in terms of farmers' selection behavior for new fields based on topography and proximity to villages. Data describing the current and historic condition of the vegetation cover, land use, and erosion for a watershed in Guinea were derived from aerial photography and ground sampling. Maps of these conditions were prepared and entered in a geographic information system (GIS) together with topographic data. From these data, maps of secondary variables (slope, village proximity, site productivity, and labor) were derived using the spatial operators contained in the GIS. These variables were ranked for agricultural preference and combined following a pair-wise hierarchy to generate a composite agricultural site-preference surface. This ranking was done in iterations, using a two-year time increment, which corresponds to the typical duration of cultivation for any one field. Different variable combinations and underlying assumptions of model logic were tested to determine influence on simulation results. To validate the model, the projected landscape was compared with land-use data collected in 1989. Although the model did not simulate the farmers' selection behavior for topography and village proximity successfully, test results with individual variables suggest that site productivity as determined by the length of fallow is a critical variable in the site selection process. The addition of site quality data should improve model results. The watershed in which this study was performed is the focus of a development initiative supported by the U.S. Agency for International Development (USAID), in which viable options are being sought for regional application. Thus, aside from documenting the dynamics of shifting cultivation, this model allows planners to evaluate alternative strategies of land-use conversion with a graphic display of zones of potential hazards. Finally, the data contained in the GIS serve as a structure for monitoring long-term change in the region.
257

Effects of coppice thinning on growth and yield of Emory oak sprouts in southeastern Arizona.

Touchan, Ramzi January 1991 (has links)
Emory oak (Quercus Emoryi) is a dominant tree species in San Rafael Valley in southeastern Arizona. However, basic information about the effects of coppice thinning on the growth and yield of this species is lacking. Thus, objectives of the study were to measure the effects of coppice thinning on Emory oak survivor growth, ingrowth, and mortality, which are the basic components of a growth budget. This study determined gross growth, net growth, and yield estimates. In addition, this study evaluated the mean annual growth (MAG) values in relation to the biological rotation age of Emory oak in southeastern Arizona. Coppice thinning treatments were applied to sprouts of different ages. Height and diameter at root collar measurements were taken immediately after thinning and again 5 years later. Sprouts were classified into 5 age groups, 4 stump diameters, and 3 level of coppice thinnings and an unthinned control. The interactions of these treatments and their effect on growth and yield were analyzed. Stump diameters did not significantly affect the growth components, growth estimates, or yield estimates. The number of residual sprouts significantly affected the growth components, growth estimates, and yield estimates. Survivor growth, gross growth, net growth, and yield were lowest for 1 residual sprout, except for net growth of 8-year-old sprouts. There were no significant differences in net growth between the different coppice thinning treatments. At age 8-year-old sprouts, the mean annual growth of individual sprouts increased as the number of residual sprouts per stump reduced. Based on this relationship, it is recommended that 1 residual sprout be left when thinning sprouts. Age of sprouts significantly affected growth. There was an increase in the mortality of the control sprouts in the 6th year. Based on those results, it is recommended that thinning be conducted in the 5th year of the sprout's growth. Proper timing of thinning can reduce the rotation age of Emory oak sprouts, if the rotation is based on achievement of a specified diameter. To draw firm conclusions about the effects of thinning on shortening the rotation age, the study measurement needs to be continued into the future.
258

GROWTH AND YIELD OF EMORY OAK WOODLANDS IN SOUTHEASTERN ARIZONA

Touchan, Ramzi, 1949- January 1986 (has links)
No description available.
259

Stalled gaps or rapid recovery : the influence of damage on post-logging forest dynamics and carbon balance

Lincoln, Philippa R. January 2008 (has links)
I assessed forest dynamics, stand structure and composition using repeated measurements of permanent plots over twelve years, in areas logged according to RIL guidelines and areas logged conventionally (CL) in Sabah, Malaysia. I compared successful pathways between treatments and used stand dynamics data to estimate carbon fluxes and pools over twelve years. Matrix models were used to generate projections of carbon emissions, sequestration and storage over a thirty-year logging cycle. Stem density (439 stems ha<sup>-1</sup> (95% CI = 358 – 477), basal area (32 m<sup>2</sup> ha<sup>-1</sup> (95% CI = 23-44) ) and carbon stored in above ground biomass (AGB, 1160 Mg C ha<sup>-1</sup> (95% CI = 97 – 232)) did not differ from prelogging levels twelve years after RIL. There was no recovery of these years variables after CL (246 stems ha<sup>-1</sup> (95% CI = 200 – 303), basal area 20 m<sup>2</sup> ha<sup>-1</sup> (95% CI = 13-28), carbon in AGB 101 Mg C ha<sup>-1</sup> (95% CI = 58 – 157)). Mortality, growth and recruitment rates remained elevated throughout the study. Both damaged and undamaged trees experiencing high mortality, especially after CL. Stalled, tree-less gaps and vine-covered building phase forest covered 54% of the CL area and appeared to have increased over time. Closed canopy and tree-dominated building phase forest dominated the RIL areas (81%). Total carbon storage over a thirty year logging cycle after RIL is projected to be 40% higher than after CL and result in reduced emissions of 88 Mg C ha<sup>-1</sup> and increased sequestration of 27 Mg C ha<sup>-1</sup>. The total carbon benefit of using RIL instead of CL in lowland dipterocarp forest is projected to be 196 Mg C ha<sup>-1</sup> over a cutting cycle. My comparisons and projections of emissions, sequestration and storage in above-ground biomass show that the carbon benefit of reduced-impact logging exceeds previous projections. RIL areas are likely to provide substantial co-benefits in timber stocking, biodiversity conservation and resilience to climate change compared with CL areas.
260

Modelling competition amongst individual trees in Caledonian Forest

Richards, Mark L. A. January 2007 (has links)
Spatial competition indices for Scots pine and birch growing in heterogeneous Caledonian forest in Glen Affric were developed. Competition indices (CIs) have frequently been used in empirical models of individual tree growth. However, the contribution of CIs to the predictive ability of growth models is often very small. The poor performance of CIs may relate to the choice of spatial descriptors and functional form of the index. To improve CI performance a novel approach utilising neural networks and simulated annealing for the optimisation of CIs was developed.

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