https://www.ajol.info/index.php/sfjfs/issue/feed Southern Forests: a Journal of Forest Science 2021-06-25T14:06:50+00:00 Publishing Manager publishing@nisc.co.za Open Journal Systems <p><em>Southern Forests: a Journal of Forest Science</em><span> is one of the leading forestry journals in the Southern Hemisphere. The journal publishes scientific articles in forest science and management of fast-growing, planted or natural forests in the Southern Hemisphere and the tropics. Papers are also encouraged on related disciplines such as environmental aspects of forestry, social forestry, agroforestry, forest engineering and management as well as the goods and services that are derived from forests as a whole. Articles published by the journal are of value to foresters, resource managers and society at large. The journal particularly encourages contributions from South America, Africa and tropical/subtropical Australasia and Asia. Publication of the journal is supported by the Southern African Institute of Forestry.</span></p><p>Read more about this journal <a href="http://www.nisc.co.za/products/17/journals/southern-forests-a-journal-of-forest-science" target="_blank">here</a>. </p> https://www.ajol.info/index.php/sfjfs/article/view/209458 Natural regeneration status and soil seed bank composition in IITA Forest Reserve, Ibadan, Oyo State, Nigeria 2021-06-25T13:05:06+00:00 Bright Danso Appiagyei dansob64@gmail.com Akinyele O. Adejoke dansob64@gmail.com <p>The International Institute of Tropical Agriculture (IITA) Forest Reserve is a secondary rainforest that has been protected since 1965. It&nbsp; serves as a refuge for many species that were once common but have declined, due to urbanisation and population pressure. The study was conducted to assess the natural regeneration status and soil seed bank composition of the Forest Reserve. Two transects of 500 m were laid out using systematic line transect sampling technique. Ten sample plots of 25 m × 25 m (625 m2) on each line transect were used to identify tree species. Subplots of 5 m × 5 m for shrub and climber species, as well as 1 m × 1 m for herb species were demarcated at the<br>corners and centre of the main plots for identification. Quadrats (15 × 15 cm) were laid out at the corners of the plots and at the centre for soil collection at depths of 0–5 cm, 5–10 cm and 10–15 cm. The regeneration status of species was determined based on sample size of seedlings, saplings and mature trees. Floristic compositions in the Forest Reserve included 58 tree, 26 shrub, 19 climber and 6 herb&nbsp; species. The natural regeneration status of the Forest Reserve was good with high numbers of seedlings (465/ha; 37.05%) and saplings (431/ha; 34.34%) compared with mature trees (359/ha; 28.61%). The families observed to be most abundant in the regeneration were Malvaceae, Moraceae and Apocynaceae. A total of 21 species was recorded using the seedling emergence technique. There were 11 herbs, six climbers, one shrub and three tree species. Similarity between standing vegetation and seed bank was low (0.067). The study revealed a poor soil seed bank composition, suggesting that regeneration of woody species from the persistent seed bank would be hampered if the standing vegetation is degraded.</p> <p><strong>Keywords:</strong> forest regeneration, species composition, systematic transect </p> 2021-06-25T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/sfjfs/article/view/209462 Developing a satellite-based frost risk model for the Southern African commercial forestry landscape 2021-06-25T13:11:14+00:00 Riyad Ismail riyad.ismail@sappi.com Jacob Crous riyad.ismail@sappi.com Giovanni Sale riyad.ismail@sappi.com Andrew Morris riyad.ismail@sappi.com Kabir Peerbhay riyad.ismail@sappi.com <p>Frost is a sporadic meteorological event affecting the productivity of commercial forests in South Africa. Severe frost occurrences may cause irreversible damage to forest stands, slowing down tree growth or leading to tree mortality. Using the Moderate Imaging Spectrometer (spatial resolution: 1 km by 1 km, swath: 1 200 km by 1 200 km) night-time land surface temperatures between 2002 and 2011, this study mapped frost risk classes using six satellite-derived variables at the landscape level. These variables included calculated thresholds of minimum temperature, probability of frost occurrence, mean temperature, total number of frost days, frost duration and the<br>frost severity index. Results show that, using an unsupervised random forest approach with partitioning around medoids, clustering was successful in mapping frost risk using eight optimal clusters. The methodology developed in this study contributes to building a robust frost-risk model to manage and mitigate forest frost damage.</p> <p><strong>Keywords:</strong> MODIS LST, frost risk, unsupervised random forests, PAM clustering </p> 2021-06-25T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/sfjfs/article/view/209463 Solid wood property variations in early-age Acacia plantation trees grown in southern Vietnam 2021-06-25T13:17:08+00:00 David Blackburn Daniel.Mendham@csiro.au Vu Dinh Huong Daniel.Mendham@csiro.au Nguyen Duc Thanh Daniel.Mendham@csiro.au Daniel Mendham Daniel.Mendham@csiro.au <p>A high demand for woodchips has encouraged smallholder farmers in Vietnam to invest in short-rotation Acacia plantations to produce pulpwood that has a relatively quick, though often low, income return. Because of an expanding export furniture industry, the Vietnam Government has sought to increase sawlog production and, at the same time, improve returns to smallholder farmers. However, currently the quality and therefore market value of the timber from acacias under differing management strategies has not been well quantified. Acacia auriculiformis, both in its pure form and its hybrid with A. mangium (Acacia hybrid) are grown in plantations in Vietnam to produce<br>merchantable timber, though the inferior mechanical properties of juvenile wood at an early age has impeded access to higher-value&nbsp; product markets. However, with thinning, there may be improvements in wood properties that could enhance sawlog values. This study examined how the wood properties of plantation grown Acacia hybrid change with stand age, explored differences in wood properties between Acacia hybrid and A. auriculiformis following different thinning treatments, and determined which of the two species is the most favourable for solid wood products. The potential to supply logs to produce sliced veneer for the furniture industry was also investigated. Logs from A. hybrid trees aged eight years could be processed to manufacture structural products, and at age five years for manufacturing utility furniture. Acacia auriculiformis thinned to 833 stems per hectare at age 4 years had mechanical wood properties indicating a potential for durable flooring products that can command a high value in the market. Because of dead knots, most sliced veneer samples were not acceptable for face veneer, though visual assessments indicated that with pruning, an attractive high-value product could potentially be produced. Tree species rather than age or thinning treatment had the most influence on wood properties.</p> <p><strong>Keywords:</strong> income, machinability, sawlogs, smallholder, strength, thinning </p> 2021-06-25T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/sfjfs/article/view/209466 An analysis of South African sawmilling competitiveness 2021-06-25T13:22:22+00:00 S. Grobbelaar schalk.grobbelaar@up.ac.za J.K. Visser schalk.grobbelaar@up.ac.za <p>The South African sawn timber market supply and demand are in equilibrium and significantly associated with the local residential&nbsp; construction market. During the great financial crisis (GFC), the local residential construction market contracted. This caused a reduction in sawn timber demand, price and margin. Subsequently, the competition between sawmillers increased and led to the closure of 41 mills. This study included a sawmilling competitiveness analysis for South African sawmills taking part in the Crickmay Intermill comparison from 2004 to 2017. The Crickmay Intermill comparison assumes that nett margin is the measurement for competitiveness. Spearman correlation tests were used to compare performance measurements with nett margin. This and other studies found significant associations between the implementation of value-adding strategies and competitiveness. Sawmills that effectively create more value from the raw material tend to be more competitive. In contrast with other studies, our research determined that people costs are significantly associated with competitiveness. However, like other studies, it was confirmed that labour productivity is not associated with competitiveness. This study argues that South African sawmillers can increase competitiveness by implementing value-adding strategies, implementing competitive remuneration policies and increasing the sawn timber usage intensity in South Africa.</p> <p><strong>Keywords:</strong> people costs, productivity, value recovery, volume recovery </p> 2021-06-25T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/sfjfs/article/view/209467 Models for predicting slenderness coefficient from stump diameter for <i>Tectona grandis</i> stands in south-western Nigeria 2021-06-25T13:27:00+00:00 Onyekachi Chukwu onye20042000@yahoo.com <p>Illegal logging has continued to be a major cause of depletion of the tropical forests in developing countries. However, empirical means of estimating the growth characteristics of a removed tree, which will facilitate the conviction of illegal loggers in judicial proceedings, are&nbsp; lacking. This study aimed at developing a model that can predict individual tree slenderness coefficients (SC) from stump diameter (Ds) for Tectona grandis stands in Omo Forest Reserve, Nigeria, for timber valuation in case of illegal felling. Diameter at breast height (DBH; cm), Ds (cm) and total height Ht (m) were measured from all <em>T. grandis</em> stands with a DBH ≥ 5.0 cm, within 35 temporary sample plots (TSPs) randomly laid out in 6 age series (26, 23, 22, 16, 14 and 12 years). The least squares regression method was used to model tree SC from Ds. Six SC-Ds models were fitted and evaluated. The relationship was best described by the single logarithmic function which gave best-fit values for the adjusted coefficient of determination, the Furnival’s index and the standard error of the estimate. This study showed that&nbsp; tree SC estimations were possible even when the only information available was the Ds. The single logarithmic model was validated using independent data and was found to be suitable for estimating the SC of <em>T. grandis</em> stands in Omo Forest Reserve, south-western Nigeria. Future studies should consider developing models for predicting other tree growth variables from Ds.</p> <p><strong>Keywords</strong>: linear and non-linear models; tree stump; timber trespass; tree slenderness coefficient; tree stability index</p> 2021-06-25T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/sfjfs/article/view/209469 Analysing species site-specific tree growth, mortality and in-growth for miombo woodlands in Tanzania 2021-06-25T13:32:57+00:00 E.E. Njoghomi elisha.njoghomi@helsinki.fi S. Valkonen elisha.njoghomi@helsinki.fi K. Karlsson elisha.njoghomi@helsinki.fi <p>The silvicultural information base for the development of management regimes for Tanzanian miombo woodlands is underdeveloped. The limited and fragmented information on tree growth and stand dynamics has constrained the progress of sustainable management in these woodlands. Therefore, this study focused on analysing major components of tree growth, mortality, in-growth and stand dynamics on permanent sample plots in miombo woodlands. Empirical modelling within a species-grouping framework was applied to tree&nbsp; increment as a function of the species characteristics, tree size and stand conditions. An inversed J-shape diameter distribution of the stand indicated the presence of a working regeneration process, pointing towards sustainability in stand structures. The regulation of stand density is one of the key parameters in the sustainable management of miombo woodlands, providing a powerful tool for&nbsp; maximising in-growth, minimising mortality and enhancing tree growth and yield for a healthier miombo ecosystem.</p> <p><strong>Keywords</strong>: miombo woodlands; growth dynamics; increment models; mortality and in-growth; permanent sample plots; species grouping</p> 2021-06-25T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/sfjfs/article/view/209471 Estimating above-ground biomass of individual trees with terrestrial laser scanner and 3D quantitative structure modelling 2021-06-25T13:43:06+00:00 Tasiyiwa P. Muumbe tagwireyip@gmail.com Paradzayi Tagwireyi tagwireyip@gmail.com Pride Mafuratidze tagwireyip@gmail.com Yousif Hussin tagwireyip@gmail.com Louise van Leeuwen tagwireyip@gmail.com <p>This study explored the feasibility of using the terrestrial laser scanner (TLS) and quantitative structure modelling (QSM) to estimate the above-ground biomass (AGB) of individual trees in the tropical rainforest using data from the Ayer Hitam Forest Reserve, Malaysia. We also tested the influence of varying the runs, the cover set’s diameter and nmin values on the ABG derived. To achieve our objectives, we estimated diameter at breast height (DBH) and height of 100 trees from 26 plots using both TLS and QSM, and field measurements then AGB based on both methods. We observed a powerful positive linear correlation between TLS and field-measured DBH (R2 = 0.97) and between TLS and field-measured height (R2 = 0.77), and a moderately strong relationship between TLS and field-based AGB (R2 = 0.56). TLS and QSM overestimated AGB by 30% of field-based estimates. Varying the number of runs had no significant influence on the AGB derived from the TLS and QSM (one-way ANOVA, p &gt; 0.05) while increasing the cover set diameter led to an increase in the derived AGB (one-way ANOVA, p &lt; 0.05). The QSM was very sensitive to variations in the nmin (one-way ANOVA, p &lt; 0.05). Our study has demonstrated that the TLS and QSM can be used for estimation of AGB for individual trees but with varying reliability. Regardless, our study provides yet another non-destructive approach to the suite of methods for estimating carbon of individual trees for various applications, including Reducing Emissions from Deforestation and Forest Degradation.</p> <p><strong>Keywords</strong>: 3D reconstruction, allometric equation, forest carbon, point cloud data, REDD+ </p> 2021-06-25T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/sfjfs/article/view/209474 Tier 2 above-ground biomass expansion functions for South African plantation forests 2021-06-25T13:46:44+00:00 Steven Dovey steven.dovey@sappi.com Ben du Toit steven.dovey@sappi.com Jacob Crous steven.dovey@sappi.com <p>Carbon stocks estimated for greenhouse gas emission reporting in South African plantation forests require improvement for local&nbsp; relevance. We developed biomass expansion and conversion factor (BECF) models to convert enumeration data to above-ground biomass (AGB) for major genera. Local biomass data and allometric models were aggregated across major taxa and scaled to utilisable stem and non-utilisable (bark, branch, foliar) biomass on 1 735 permanent sample plots. Models were developed for each genus to estimate BECF from utilisable volume to overcome bracket stepping in the Intergovernmental Panel on Climate Change (IPCC) lookup tables. To enable more accurate biomass estimates for growers who record tree volume and bone-dry wood density, an alternative calculation was developed that capitalises on stem-wood comprising 70% to 90% of AGB at rotation age. AGB is the sum of utilisable stem and non-utilisable components. Stem mass can be calculated as the product of volume and wood density. Models to estimate non-utilisable biomass from utilisable volume were developed for each genus. Local models estimated lower hardwood biomass and marginally lower softwood biomass than IPCC estimates. Use of local estimates compared to default values result in lower carbon stock estimates and reduced fluxes using the stock change method. Developing further allometric models and BECFs at the species or hybrid level will have little value due to rapidly changing genetic deployment and current work has indicated non-significant differences between genotypes within each genus. Further work should focus on improved tree volume and wood density estimates as well as on below-ground biomass estimates.</p> <p><strong>Keywords:</strong> allometric, BECF/BCEF, carbon accounting, climate change mitigation, greenhouse gas (GHG) </p> 2021-06-25T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/sfjfs/article/view/209475 Perspectives and drivers of modernisation of silviculture re-establishment in South Africa 2021-06-25T13:51:35+00:00 Muedanyi Ramantswana muedanyi.ramantswana@mandela.ac.za Michal Brink muedanyi.ramantswana@mandela.ac.za Keith Little muedanyi.ramantswana@mandela.ac.za Raffaele Spinelli muedanyi.ramantswana@mandela.ac.za Paxie Chirwa muedanyi.ramantswana@mandela.ac.za <p>Efficient and cost-effective re-establishment practices are important parts of any sustainable forest re-establishment programme. Re-establishment activities include residue management (post-harvest slash), preparation of a planting position, planting, fertilisation and vegetation management. In South Africa, these activities are largely labour intensive, time-consuming and relatively costly. Although mechanisation of site preparation during afforestation was achieved in the mid to late 1990s, plantation re-establishment operations in South Africa have remained manually oriented. However, there have been notable technology developments over the past decade. Semi-structured interviews were conducted with 66 experts (grower company specialists, foresters, contractors and machine manufacturers) to get their perspectives on modernisation of re-establishment activities in South Africa. Frequency distribution and chi-square test analysis found that two-thirds of the experts believed that re-establishment activities had progressed in terms of technology over the past decade. This development was reported as primarily due to the need to improve health and safety (91%), increase production whilst reducing costs (89%), improve stand productivity (quality) (86%), mitigate social (mainly labour) risks (80%) and reduce prevalent negative environmental impacts (50%). Key barriers to modernisation were identified as the capital cost of equipment (65%), reduction in employment&nbsp; opportunities (44%) and low utilisation of equipment due to seasonality of silviculture work (18%). Experts indicated that the efficiency of mechanised re-establishment equipment can be affected negatively by residues, high stumps and compaction of the site after harvesting. The results of this study will assist forestry stakeholders to make informed decisions when planning and implementing modernised silviculture operations.</p> <p><strong>Keywords</strong>: experts, planting, technology </p> 2021-06-25T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/sfjfs/article/view/209477 Residual fertiliser and liming impacts in a long-term <i>Acacia mearnsii</i> trial 2021-06-25T13:55:44+00:00 Louis Titshall Louis.titshall@sugar.org.za <p>Sixth rotation growth measurements of an Acacia mearnsii fertiliser trial established to test the effect of nitrogen (N), phosphorus (P), potassium (K) and lime application on growth and bark production, showed that residual P and lime effects are present. First established in 1951, the trial was re-established a further five times. The sixth rotation was planted in late 2003 without the application of fertiliser or lime, but with treatment plot identities maintained to test the residual effects of these treatments into the sixth rotation. Soil properties, stocking, height, basal area, volume and bark yield were determined at rotation-end. There were significant positive effects of residual P on height, basal area and volume and significant negative effects of residual lime on stocking, basal area, volume and bark yield. The responses were significantly, though weakly, related to soil properties associated with residual treatment effects. Liming is not advocated in wattle plantations, while there are residual benefits of applied P. The lack of strong relationships, however, does not permit adjustment to current wattle fertiliser guidelines.</p> <p><strong>Keywords</strong>: bark yield, black wattle, lime, phosphorus, volume</p> 2021-06-25T00:00:00+00:00 Copyright (c) https://www.ajol.info/index.php/sfjfs/article/view/209479 Miombo woodlands in a changing environment: securing the resilience and sustainability of people and woodlands 2021-06-25T14:00:00+00:00 Almeida A. Sitoe almeidasitoe@gmail.com <p>No Abstract.</p> 2021-06-25T00:00:00+00:00 Copyright (c)