Volume and taper studies in Pinus patula and Cupressus lusitanica trees growing in Kenya forest plantations are discussed. The ultimate objective of the study was to find suitable models for estimating volumes and taper rates using two approaches for each parameter (i.e. volume and taper). These included producing volume models in the traditional way and by integrating taper models. Taper models derived from the best of the volume models were compared to the taper models produced from taper data in the traditional way to find out the efficiency of each approach. Data from the two species were used to fit a few popular volume and taper models. Trials were also made to develop new models. Of the popular volume models tested the logarithmic volume model was found to be giving very good estimates. Weighted models conditioned through the origin, by a technique proposed in the study, were also giving similar good estimates. Models weighted by current approach were, however, giving relatively poor estimates. Volume-based taper models were found to be giving biased diameter estimates along the tree profiles. However, when integrated for total volume, the volume estimates given seemed to be better than those given by the other taper models tested. Because of their bias in estimating the diameters and other points along the tree profile, volume-based taper models are not recommended for estimating volumes to any other points along the tree profiles. Other popular taper models were also giving biased diameter estimates. They lacked inflection points. When integrated for volumes, they were giving very poor estimates. Two fairly simple taper models have been proposed which have most of the characteristics needed in a taper model to give proper profile description. They have been recommended for constructing the inside volume tables and taper tables for the two species. They should also apply well in other conifers. One model describes profiles of trees with butt swell while the other describes trees with smooth stem forms. / Forestry, Faculty of / Graduate

This study presents the growth, yield and the silvicultural management of Cupressus lusitanica, Pinus patula and Pinus radiata, the three most important timber species growing in the Kenya highlands. The study Is based on 163, 176 and 164 permanent sample plots for the three species respectively. The stand dominant height development was predicted as a function of stand age and site index, defined as dominant height at reference age of 15 years. The Chapman-Richard's growth function was used for C. lusitanica and P. radiata while a linear quadratic equation was used to describe dominant height development for P. patula by geographical regions. Height development for the two pine species was found to be significantly different (up to age 20 years) in the Shamba and grassland establishment sites. Stand basal area before thinning was predicted as a function of stand age, dominant height and number of stems using a Weibull-type growth equation. In thinned stands basal area was predicted through a basal area increment nonlinear equation. For P. radiata, basal area increment was predicted as a function of basal area at the beginning of the growth period (1 year) and age. For C. lusitanica and P. patula, a third term-stand density index, defined as the percent ratio of average spacing between trees to stand dominant height was included. The Weibull probability density function was used to characterize stand diameter distribution with the Weibull parameters predicted as a function of stand parameters. Stand volumes were determined from tree volume equations for the respective species while the mean DBH of stems removed in thinnings was predicted from mean stand DBH before thinning and weight of thinning. Using the above functions, a growth and yield simulation model EXOTICS was constructed. Written in FORTRAN IV G-level which is compatible with IBM System/360 and System/370, EXOTICS is an interactive whole-stand/distance independent model with an added capability for providing diameter distribution (by 3 cm diameter classes) to give final main stand yield by size classes. The model is intended to facilitate silvicultural management of the three species in the Kenya highlands. On validation, EXOTICS was found to have no bias within the range of validation data, and 95% confidence limits of 16%, 20% and 17% for C. lusitanica, P. patula and P. radiata respectively. Using EXOTICS, the current silvicultural management schedules in Kenya were studied. The thinning regimes were found to have marked effects on the current annual volume increment. It was therefore concluded that at the present level of silvicultural management, Moller's theory that thinning has no appreciable effects on total volume yield does not hold for the three species in Kenya. The current thinning policy aimed at production of large-sized sawlog crop in as short a rotation as possible at the expense of some loss in total yield is discussed and found to have been overtaken by events. A policy based on the concept of maximum volume production is advocated. A thinning experiment (using C. lusitanica) demonstrated that total merchantable volume could be increased by between 5 and 10% (using 20% thinning intensity) depending on site quality class. Within the range of stockings maintained in plantations in Kenya, thinning intensity was found to be the most important consideration, with stocking before thinning having very little effect on both mean annual volume increment and total merchantable volume yield up to age 40 years. / Forestry, Faculty of / Graduate

Self-reliance in wood products is one of the major objectives of Kenya's forest policy; stated as the management of forest resources for the adequate provision of the needs of the country in timber and other forest products to meet the community's requirements, and where possible provide for exports. The implications of such a policy are such that strategies formulated, programmes designed and practices employed in production of wood resources and wood-based products should be geared towards the anticipated needs of the intermediate consumers, which in turn are only responding to the needs of the final consumers - the society. It is argued here that such production strategies, programmes and practices cannot be formulated and pursued to satisfactorily fulfill the policy objectives, without first identifying and understanding the needs of the specific target markets. Among factors identified as necessary in understanding the target markets are market structure, size, location and dynamics of consumption pattern-determining parameters such as time, demographic and economic factors. Using production and consumption data, primarily for the period 1960-1975, quantitative and qualitative methods were used to analyze and describe the various markets of wood products, as the basis of forecasting the probable future market trends. On the basis of current management and consumption trends, forecast estimates indicate possible internal wood supply deficits during, and beyond, the period 1996-2000 AD. Current and projected market trends indicate a progressive shift from mechanical wood industries and products, mainly sawnwood, towards fibre-based reconstituted wood products - fibreboards, particleboards and paper products. This projected development would tend to favour greater attention by forest management to the potentials of not only natural forests but species diversification of man-made forests. The fibre-based industries can satisfactorily utilize small-sized logs, hence shorter rotations, and a wide range of species composition since some of the products do not exhibit individually specific wood characteristics. Plantation-species diversity, in addition to avoiding the risks of possible loss in case of an epidemic, has the advantages of comparative climatic and zonal suitability in establishment. Trends indicate that fuelwood is, and for some time will continue to be the single major component of wood consumption, rising from about 15 million M³ (rw) by 1975 to about 30 million M³ (rw) per year by 2000 AD; yet forest management seems to have no supply strategy for this product. A major identified deficiency in forestry production-utilization-marketing as a system has been insufficient coordination in wood production management decisions with different industries' development programmes and anticipated market trends, and their requirements. Probable future wood supply-demand balances were comparatively estimated on the basis of potential supplies from current and planned wood production programmes and the projected markets. From the view point of wood production management decisions, medium and long-term market forecasts can be considered more meaningful than short-term needs, since the latter will have to draw from maturing stocks, while current and planned forest establishment programmes are the basis of future medium and long-term supplies. For this reason, emphasis has been laid on the medium and long-term forecasts, up to 50 years from now, or 1 to 2 production rotations. This analysis indicates that while management has placed emphasis on plantation forestry for industrial wood supplies, the strategy, despite its merits, is biased in favour of predominantly two exotic softwood species groups, comprising of cypress and pines despite the feasibility of producing wood supplies from potentially commercial and marketable indigenous species (mainly hardwoods) and other exotic hardwoods. While natural forests constitute about 92 percent and plantations 8 percent of Kenya's forests, little management effort has been directed at commercial wood production from the former, whose annual supplies average 20 percent of total industrial wood harvested. Quantitative and qualitative analysis of indigenous woods in natural forests indicates great commercial potential of these indigenous resources. There is a need for a shift from exclusive reliance on silvicultural considerations and wood production per se as the main criteria for production management, to a set of criteria that gives sufficient consideration emphasis on utilization and marketing requirements. Greater co-ordination between foresters, industries and marketers is required in the areas of research, development decisions, information gathering and dissemination, and wood resources allocation and sales to facilitate Production Planning for the target market needs. / Forestry, Faculty of / Graduate