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- Volume 2001, Issue 191, 2001
Southern African Forestry Journal - Volume 2001, Issue 191, 2001
Volume 2001, Issue 191, 2001
Source: Southern African Forestry Journal 2001, pp 1 –8 (2001)More Less
Simultaneous stand-level growth and yield models for <i>Eucalyptus grandis</i> in Zimbabwe were developed from Correlated Curve Trend (CCT) and Nelder wheel experiments replicated on five different sites. Nonlinear three-stage least squares method was used to simultaneously fit prediction and projection equations for stand basal area, volume and stand density (S/ha). The age-dominant height model was fitted separately to the data to enable the estimation of site indices for the plots. The data consisted of a total of 313 growth periods of stands ranging in age from 1.3 years to 19.5 years, and site indices from 14 m to 37 m (at an index age of 7 years). The models were validated both quantitatively and qualitatively. Correlation between error components for basal area and volume was strong and significant while the correlation of stand density with basal area and volume was either weak or non-significant. Degree of determination was relatively high for all the models. The mean biases for basal area, volume and stand density predictions were negative. The use of these models in stands managed for pole or saw log production was recommended.
Yield potential of selected Eucalyptus genetic stock on the sandy soils of the South African Cape West CoastSource: Southern African Forestry Journal 2001, pp 9 –20 (2001)More Less
Land available for afforestation in the Western Cape Region has largely been subordinate to agriculture. Eucalypt species have never been tested intensively along the West Coast. Climatic matching suggests planting of species from West Australia as native habitat introductions, or from seed sources in the Mediterranean region where eucalypt species have been tried successfully, such as Morocco and Israel. Promising growth of eucalypt hybrids on marginal sites in the summer rainfall areas of South Africa prompted the inclusion of local as well as some hybrid seedlots obtained from Morocco. The terrain of the trial site is an almost flat old dune area (slopes < 3%) with a westerly aspect and 7 km from the sea. The mean annual rainfall is about 400 mm, with most rain falling during winter. The other months are usually windy and dry, and the summer months are hot (maximum temperature > 35<sup>o</sup>C). The sandy soils have a coarse texture within the normal rooting depth. During winter water tables were observed on all soils within 2-3 m from the soil surface. The trial was planted during the winter of 1991. It consisted of ten local hybrid families of different species involving <i>Eucalyptus grandis</i>, 14 <i>E. camaldulensis</i> seedlots from Australia, Morocco and Israel, 7 hybrid lots from Morocco, 4 <i>E. grandis</i> ex Morocco and 11 other species including <i>E. gomphocephala</i> and <i>E. cladocalyx</i>. The results indicate the potential for correct species/provenance selection. Potential yields of 8 to 10 m3 / annum / ha are predicted on the assumption that good genetic stock and correct silvicultural procedures are used. Most notable was the expected performance of the well known West Australian species (<i>E. gomphocephala, E. cladocalyx</i>). The group of 14 <i>E. camaldulensis</i> seedlots can be regarded as representing a series of provenances from Australia, except for three from Israel and one from Morocco. As expected, the different provenances survived well but performed variably, generally ranking in the bottom 50 %. However, two seedlots - the provenance from Lake Albacutya and the seedlot from Morocco - are worth noting as they actually ranked among the top ten for index score. Generally, the provenances from Queensland (e.g. Petford) and New South Wales that normally do well in summer rainfall regions did not do well. As the relevant parent species originate in summer rainfall regions, the phenomenal growth rate of many of the hybrid families came as a surprise in this trial. The yield of the best <i>E. grandis x E. camaldulensis</i> (GXC) family would have been equivalent to that of <i>E. gomphocephala</i> if the survival was equally good. The <i>E. grandis x E. tereticornis</i> (GXT) family did survive and performed equally well. The second best GXC family would have yielded even better than the GXT if it had a better survival. The GXC and GXT families were all within the top 50 % of the trial.
Source: Southern African Forestry Journal 2001, pp 21 –28 (2001)More Less
With the objective of evaluating the correlation of wood basic density with age in seven <i>Eucalyptus grandis</i> clones planted in Brazil, five trees in each clone were sampled at the ages of 0, 5, 1, 5, 2, 5, 3, 5, 4, 5 and 7, 5 years. The analysis of these samples showed that the intraclonal variation of the basic density (except for 0, 5 year-old) was very low, while the interclonal variation was moderately high (from 7, 5 % at 0, 5 year-old to 4, 1 % at 7, 5 year old) for all ages. The analysis of variance indicated that the variation between clones, between ages and the clone ( age interaction were all significant (P <u><</u> 0, 01), but the variation of the basic density of the trees within-clones were non-significant. The study of temporal stability of the basic density showed that most of the clones behave similarly to the mean clone for all ages. According to the analysis of regression of the mean basic density per clone using temporal-index as predictor it was found that for this group of clones is it possible to predict the basic density of wood produced at one age from its value at another age. Indeed, the correlation of the basic density at different ages within a clone showed that, except for the correlations for wood of 0, 5 year-old, all other correlations were statistically significant. However, it can be noted that correlations based on more recent ages presented higher values of coefficient of correlation, even if the same time span has been considered. Also, it was shown that was it possible to estimate the basic density using the age of the tree as independent variable through the logarithmic model both for individual clones (R<sup>2</sup> from 75 % to 96 %) and for all seven clones analysed together (R<sup>2</sup> = 92 %).
Responses of Eucalyptus species to fertilizer applications made at planting on granitic parent materials in the Mpumalanga and Northern Provinces of South AfricaSource: Southern African Forestry Journal 2001, pp 29 –38 (2001)More Less
Early research trials in South Africa have shown that <i>Eucalyptus</i> species generally respond positively to the addition of nutrients at planting. However, as most of these research trials were located in KwaZulu-Natal, it was important to investigate the nature of the response in other afforested regions of the country where this genus is planted. Consequently, a number of fertilizer trials were established in the late 1980's and early 90's in Mpumalanga and the Northern Province to investigate the nature of fertilizer responses in <i>Eucalyptus</i> species. Three of these trials form a series and were established to investigate the impact of nitrogen (N), phosphorus (P) and potassium (K) additions made both individually and in combination. In addition, two trials in Mpumalanga were initiated to investigate genotype by fertilizer interactions. Viewed as a whole, the results indicate that growth improvements in response to the nutrient additions are readily obtainable. Highly significant positive responses to N and P, each applied individually, occurred immediately after planting. The response to N appeared more sustained than the response to P. The best growth was observed when N and P were applied together. The ratio of N to P that gave the best response ranged from 3:1 to 3:2. No genotype by fertilizer interactions were observed in the trials investigating this aspect.
Source: Southern African Forestry Journal 2001, pp 39 –42 (2001)More Less
Afromontane forests in the southern Cape are surrounded by fire-prone fynbos. Although the presence of charcoal in Afromontane forests indicate that they do burn, little is known about the influence of fire on the dynamics of these forests. We compared the species composition and diversity of tree species in the margin and core of recently burned mountain forest. The species composition and diversity of tree species differed between the forest margin and core, with the core being more species rich and comprising trees not recorded in the margin. Although small trees of a number of species accumulated in the forest margin and core, fire killed most small trees in the margin but only a few in the core. In the margin, comparatively low numbers of small <i>Ocotea bullata</i> and <i>Cunonia capensis</i> were killed, and these two species formed > 90 % of the large trees recorded in the margin, but lower proportions in the forest core. Fire is thus an important factor influencing species composition and diversity in mountain forest.
Source: Southern African Forestry Journal 2001, pp 43 –52 (2001)More Less
Natural resource valuation techniques have been applied in recent years to savannas and savanna resources in South and southern Africa. Results from these studies have been used to demonstrate the importance of savannas, and to assist in resource-use planning. Because these studies have been conducted to meet different research objectives a large number of disparities exist between studies. This makes comparison of results difficult and identification of underlying drivers of value is problematic. This paper discusses issues which can lead to differences in estimates of resource value, and makes recommendations for future studies to reduce incompatibilities. In particular, this paper recommends that future studies make full descriptions of the objectives of the study, the background characteristics of the study area (including the social, political, economic, cultural, and biophysical characteristics), the methods used, and assumptions made. In this way, the values reported from case studies may be used in other research and decision-making exercises
Author Peter J. DyeSource: Southern African Forestry Journal 2001, pp 53 –64 (2001)More Less
Accurate prediction of growth and yield of forest plantations remains important to the forestry industry for such purposes as assessing the benefits of silvicultural practices, matching species to site, understanding economic risks, predicting profitability and scheduling harvests. Conventional methodology is based on statistically-derived stand growth curves used to define a site index reflecting growth potential. Limitations of the method are widely acknowledged: factors constraining productivity are not identified; changes in environmental conditions affecting growth may not be taken into account; and growth predictions at sites not previously afforested may be poorly predicted. The hydrological impact of forest plantations remains a controversial issue. Existing prediction models do not take sufficient stand and site detail into account to usefully predict water use patterns on a scale that is practical to forest managers. Several relatively simple simulation models based on the major physiological processes behind growth and water use of forest stands have emerged recently, and are claimed to be useful tools for forest managers and water resource planners. One of these, the 3-PG model (Physiological Principles in Predicting Growth) is assessed here for its ability to predict growth and water use of <i>Pinus patula</i> at four widely separated test sites. Model parameter values are fixed according to available field data, reported data for other species of pines, or as a result of a fitting process to match simulated to observed patterns of growth and water use in four diverse stands of this species. Simulation results are very encouraging, and a further phase of model testing on a wider range of test sites is recommended to improve parameter estimates and demonstrate the usefulness of the model.
Source: Southern African Forestry Journal 2001, pp 65 –74 (2001)More Less
Community surveys were conducted through the use of participatory community meetings and a questionnaire in the Butterworth area of the Eastern Cape. The objectives of these surveys were to determine the needs and perceptions of communities regarding woodlots and wood utilisation. From the surveys it is clear that woodlots do play an important role in the livelihoods of communities in the Butterworth area, but that the role varies according to geographic location of the woodlot and urbanisation levels of the community. Sociological / anthropological socio-economic differences must be considered in community forestry extension work and future strategic and policy considerations.
Author Anders AalbaekSource: Southern African Forestry Journal 2001, pp 75 –88 (2001)More Less
This article examines the effects of insufficient availability of planting material on farmers' tree planting in the southern highlands of Tanzania. Patterns in scale of farmers' tree planting, species preferences, and experienced availability of planting material are investigated and compared with past sources of germplasm and with existing local nursery capacity. Different aspects of insufficient access to germplasm and possibilities for improving the germplasm supply situation are discussed. The study is based on interviews in 38 villages of 356 farmers and 161 key-informants and visits to nine nurseries. Most farmers in the southern highlands of Tanzania plant significant numbers of trees and tree planting is an integral part of farming systems. Main purposes of tree planting are fuelwood, timber in a broad sense, and fruit production. People want to plant well-known species, which in most cases are exotics, and many species, popular among professionals, e.g. indigenous and multipurpose trees, are not requested by farmers. Lack of planting material is the main constraint to tree planting, and although small private or village-based nurseries are now being established, they are still few and capacities are far below demands. Nurseries mainly raise species with seed locally available, and many species, preferred by farmers, especially fruit trees, are not produced. Currently, most nursery owners are not able or willing to pay for seed. An improved supply of seedlings and seed must be economically sustainable at local level and there is a need for widespread promotion of low-tech, low-input nursery production and an improved seed supply based on local seed sources.
Author Reino PulkkiSource: Southern African Forestry Journal 2001, pp 89 –96 (2001)More Less
One of the cornerstones of sustainable forestry is the wise use of wood resources to achieve maximum value or benefit for society, while not jeopardizing the future. At the same time forest companies must compete on an international scale, otherwise they themselves risk becoming non-sustainable. Supply chain management (SCM) is a business management approach which strives to achieve the wise use of inputs, while ensuring the health of a company in tough international competition, through breaking down barriers of communication and information flow within and between organizations and companies. In SCM the decision focus is the entire supply chain stretching from the raw materials, right through to final consumption. In this way sub-optimization of lower-level operations and processes does not put the overall objectives of the organization at risk or limit future opportunities. The concept of SCM is not new and is also known, for example, as logistical management, total system costing, holistic approach and total production management. The objectives of this paper are to outline what SCM is, show why SCM has emerged as an important field in wood procurement and finally give some examples of how a wider view of wood procurement can influence the wise use of wood resources.