Composition of woody species in a dynamic forest-woodland-savannah mosaic in Uganda: implications for conservation and management

Forest¿woodland¿savannah mosaics are a common feature in the East African landscape. For the conservation of the woody species that occur in such landscapes, the species patterns and the factors that maintain it need to be understood. We studied the woody species distribution in a forest¿woodland¿savannah mosaic in Budongo Forest Reserve, Uganda. The existing vegetation gradients were analyzed using data from a total of 591 plots of 400 or 500 m2 each. Remotely sensed data was used to explore current vegetation cover and the gradients there in for the whole area. A clear species gradient exists in the study area ranging from forest, where there is least disturbance, to wooded grassland, where frequent fire disturbance occurs. Most species are not limited to a specific part of the gradient although many show a maximum abundance at some point along the gradient. Fire and accessibility to the protected area were closely related to variation in species composition along the ordination axis with species like Cynometra alexandri and Uvariopsis congensis occurring at one end of the gradient and Combretum guenzi and Lonchocarpus laxiflorus at the other. The vegetation cover classes identified in the area differed in diversity, density and, especially, basal area. All vegetation cover classes, except open woodland, had indicator species. Diospyros abyssinica, Uvariopsis congensis, Holoptelea grandis and all Celtis species were the indicator species for the forest class, Terminalia velutina and Albizia grandbracteata for closed woodland, Grewia mollis and Combretum mole for very open woodland and Lonchocarpus laxiflorus, Grewia bicolor and Combretum guenzi for the wooded grassland class. Eleven of the species occurred in all cover classes and most of the species that occurred in more than one vegetation cover class showed peak abundance in a specific cover class. Species composition in the study area changes gradually from forest to savannah. Along the gradient, the cover classes are distinguishable in terms of species composition and vegetation structure. These classes are, however, interrelated in species composition. For conservation of the full range of the species within this East African landscape, the mosaic has to be managed as an integrated whole. Burning should be varied over the area with the forest not being burnt at all and the wooded grassland burnt regularly. The different vegetation types that occur between these two extremes should be maintained using a varied fire regim

Pinus caribaea volume 2: wood properties

Volume 1 of this monograph on Pinus caribaea Morelet published in 1973 contains information on the species in its natural environment and an account of its use as a plantation tree including its silviculture, mensuration and protection. In addition there was a short section on tree improvement and wood properties and one on economics and management. It was planned at the time of writing Volume 1 that a more comprehensive Volume 2 should be written dealing with wood properties and uses of the wood. This volume is intended to bring the wood properties section of Volume 1 up to date and amplify it to become a comprehensive survey of the current state of knowledge on the wood properties of the species in its natural environment and in plantations. It is complementary to Volume 1 in that no attempt is made to cover any of the same ground other than that dealing with wood properties and uses...</p

Some wood properties of Pinus patula (Schiede and deppe) from Uganda and techniques developed in studying them

A comparison is made of 25 physical and mechanical properties of the wood of Pinus patula(Schiede and Deppe) from twenty trees from four sites in Uganda. X-ray densitometry was used to study wood density and statistical methods were used to analyse the data; a number of techniques were developed to study particular properties. The following were the main findings of the study. The range of physical and strength properties between and within trees was determined. Between site differences were small compared with between tree differences; within tree differences followed the normal increase of density and strength from pith to bark but were more variable up the tree. The limited number of morphological characters studied were not closely related to wood properties. Principal component and regression analysis showed strength properties (except cleavage strength) and density to be closely related. Shrinkage and distortion were not closely related to other properties except grain angle. A contour drawing program for maps was adopted and used to compare contours of density, ring width and 'dry matter' production within trees. This enabled the effects of rate of growth on wood density and total wood production to be seen within different parts of the stem of the tree avoiding the confusions of physiological and chronological age inherent in most mathematical methods of analysis. The technique is not, however, easily susceptible to testing for statistical reliability. There appeared to be a close relationship between ring width and wood density within an individual tree. Variations in size of juvenile core and differences between the core and mature wood were considerable. Transition from core to mature wood was found to be sharp where a severe pruning had occurred. A computer program was developed to integrate wood density, wood volume and weight of wood produced during the whole of each year's growth of wood in order to measure the total, averaged, response of the tree to environment and silvicultural treatments. Although the number of trees was small the study suggested a close relationship between pruning and wood density and that it may be possible to control juvenile core by pruning without seriously reducing volume production. In spite of variation of density patterns between trees, fairly close correlations were obtained between breast height wood density in the early life of the tree and whole tree wood density at 20 years old; breast height cores taken from 5 year old trees appear to give a good indication of what future wood density will be and which trees are likely to be superior in this respect. In spite of the generally good relationship between wood density and the main strength properties, consistent differences in specific strength (strength:weight ratio) were found between different trees, suggesting that some trees may produce more efficient wood in terms of strength per unit of weight than others. No attempt was made in this study to discover the reasons for this. A number of suggestions are made for further study.</p

Pinus caribaea volume 2: wood properties

Volume 1 of this monograph on Pinus caribaea Morelet published in 1973 contains information on the species in its natural environment and an account of its use as a plantation tree including its silviculture, mensuration and protection. In addition there was a short section on tree improvement and wood properties and one on economics and management. It was planned at the time of writing Volume 1 that a more comprehensive Volume 2 should be written dealing with wood properties and uses of the wood. This volume is intended to bring the wood properties section of Volume 1 up to date and amplify it to become a comprehensive survey of the current state of knowledge on the wood properties of the species in its natural environment and in plantations. It is complementary to Volume 1 in that no attempt is made to cover any of the same ground other than that dealing with wood properties and uses...</p

Some wood properties of Pinus patula (Schiede and deppe) from Uganda and techniques developed in studying them

A comparison is made of 25 physical and mechanical properties of the wood of Pinus patula(Schiede and Deppe) from twenty trees from four sites in Uganda. X-ray densitometry was used to study wood density and statistical methods were used to analyse the data; a number of techniques were developed to study particular properties. The following were the main findings of the study. The range of physical and strength properties between and within trees was determined. Between site differences were small compared with between tree differences; within tree differences followed the normal increase of density and strength from pith to bark but were more variable up the tree. The limited number of morphological characters studied were not closely related to wood properties. Principal component and regression analysis showed strength properties (except cleavage strength) and density to be closely related. Shrinkage and distortion were not closely related to other properties except grain angle. A contour drawing program for maps was adopted and used to compare contours of density, ring width and 'dry matter' production within trees. This enabled the effects of rate of growth on wood density and total wood production to be seen within different parts of the stem of the tree avoiding the confusions of physiological and chronological age inherent in most mathematical methods of analysis. The technique is not, however, easily susceptible to testing for statistical reliability. There appeared to be a close relationship between ring width and wood density within an individual tree. Variations in size of juvenile core and differences between the core and mature wood were considerable. Transition from core to mature wood was found to be sharp where a severe pruning had occurred. A computer program was developed to integrate wood density, wood volume and weight of wood produced during the whole of each year's growth of wood in order to measure the total, averaged, response of the tree to environment and silvicultural treatments. Although the number of trees was small the study suggested a close relationship between pruning and wood density and that it may be possible to control juvenile core by pruning without seriously reducing volume production. In spite of variation of density patterns between trees, fairly close correlations were obtained between breast height wood density in the early life of the tree and whole tree wood density at 20 years old; breast height cores taken from 5 year old trees appear to give a good indication of what future wood density will be and which trees are likely to be superior in this respect. In spite of the generally good relationship between wood density and the main strength properties, consistent differences in specific strength (strength:weight ratio) were found between different trees, suggesting that some trees may produce more efficient wood in terms of strength per unit of weight than others. No attempt was made in this study to discover the reasons for this. A number of suggestions are made for further study.</p

A guide to the use of Mexican and Belizean timbers

The problems of utilising the thousands of species of tree, found in tropical forests, in an efficient manner, to make useful products, have perplexed tropical foresters and wood-using industries for a long time. The number of species is large, the number of properties, which together determine whether a species is used for a particular end-use,is often quite large and the quantities available of anyone species at a particular time are often quite small.</p

A guide to the use of Mexican and Belizean timbers

The problems of utilising the thousands of species of tree, found in tropical forests, in an efficient manner, to make useful products, have perplexed tropical foresters and wood-using industries for a long time. The number of species is large, the number of properties, which together determine whether a species is used for a particular end-use,is often quite large and the quantities available of anyone species at a particular time are often quite small.</p

A guide to the use of Mexican and Belizean timbers

The problems of utilising the thousands of species of tree, found in tropical forests, in an efficient manner, to make useful products, have perplexed tropical foresters and wood-using industries for a long time. The number of species is large, the number of properties, which together determine whether a species is used for a particular end-use,is often quite large and the quantities available of anyone species at a particular time are often quite small.</p

'Prospect' for improved use of tropical timbers: a guide to the use of lesser known timbers

PROSPECT (Programmed Retrieval Of Species by the Property and End-use Classification of their Timbers) is a database containing the wood properties of tropical timbers; a recommendation was made by the 11th Commonwealth Conference in 1980 that the Oxford Forestry Institute should develop a computer operated database drawing information from its extensive library records. Following this a three year project from 1981 till 1984 was funded by the Overseas Development Administration (ODA) of the British Government. The project employed a team of three people, headed by Dr. C. Goodwin-Bailey, who wrote a computer database program to operate on the Department's mini-computer which was the only machine at the time capable of running it. Data were abstracted from the literature and by the end of the project the information for some 1300 species had been recorded on cards; 900 of these had been entered into the database. At that stage no further funds were available to promote the use of the system although it was used internally and a limited number of enquiries were answered using information from it. Subsequently, in 1989, a decision was made to convert the package for use by IBM-compatible machines, which by then had developed sufficiently in processing power to be able to manage such large volumes of data. By this time there were similar but smaller databases operated by France and the Netherlands which are described in the literature (lTIO, 1989 &amp; Wageningen, 1991).</p