The proportions of biomass across different components vary among species, developmental stages and growth environments, reflecting their allometric patterns. Allometric equations are widely used to estimate biomass, primarily based on diameter at breast height (DBH) and tree height. However, when developing generic equations for multiple species and environmental conditions, wood density becomes a key variable to consider. This study evaluated four hybrid clones of Eucalyptus species, aged between 97 and 110 months, in two regions of Minas Gerais, Brazil. Five trees per genetic material and region were sampled to determine aboveground biomass (stem, branches, bark and leaves) and average basic density. Biomass components and total biomass were estimated using different model fitting approaches: independent fitting, simultaneous fitting using non-linear seemingly unrelated regressions (NSUR) and weighted NSUR (WNSUR). Three modelling procedures were applied: (1) DBH and height; (2) DBH, height and basic density; and (3) DBH, height, basic density, and dummy variables for region and clone. The hypothesis tested was 'Integrating basic density with clone and region effects through dummy variables improves predictive performance and estimator efficiency compared to systems based solely on allometric variables. The simultaneous fitting techniques, NSUR and WNSUR, proved to be efficient in developing accurate and high-quality equation systems. The inclusion of wood density enhanced the predictive performance of generic biomass equations and accounted for the effect of clone identity. The site effect was most pronounced in clone C1.
This study evaluated the biological resistance of wood-plastic composites (WPCs) to deterioration caused by xylophagous fungi (Gloeophyllum trabeum and Trametes versicolor) and drywood termites (Cryptotermes brevis). Eight treatments were applied using different proportions of Eucalyptus sp. particles (50%, 70%, 85% and 95%) and recycled low-density polyethylene plastic (5%, 15%, 30% and 50%), bonded with either 100% tannin-based adhesive or a combination of tannin and lignosulfonate (80%-20%). The samples were hot-pressed under 3.92 MPa pressure at 160 degrees C for 10 min. To assess fungal resistance, samples measuring 2.5 cm & times; 2.5 cm & times; 1.25 cm (length & times; width & times; thickness) were exposed for 12 weeks and mass loss was analysed. In the termite tests, samples measuring 5.0 cm & times; 5.0 cm & times; 1.25 cm were exposed for 45 days, and both sample mass loss and termite mortality rate were determined. Composites with higher plastic content exhibited less fungal deterioration and lower termite consumption, together with higher insect mortality rates. Adding lignosulfonate contributed to increased biological resistance, especially in formulations containing 30% plastic. In contrast, treatments with a higher proportion of wood and 100% tannin adhesive were more susceptible to deterioration. Formulating WPCs with tannin- lignosulfonate adhesive enhances their durability against xylophagous organisms.
Preserving and managing plantation forests requires detailed information on growing stock volume (GSV) at different spatial scales. In this study, we demonstrated the potential of integrating field inventory and remotely sensed data to enhance large-scale predictions of GSV in small-scale forest plantations in the Southern Highlands of Tanzania. A total of 32 small-scale forest plantation farms/stands were selected within the area of interest (AOI). In each stand, one to three circular plots of 10 m radius were established, making a total of 63 field plots within the AOI. Within each field plot, the diameter at breast height of all trees were measured and for three sample trees the total tree height was measured. The GSV was then computed for each plot. Sentinel-2 remotely sensed data covering the AOI were downloaded and processed using the Google Earth Engine platform. For each field plot, remotely sensed predictor variables were extracted in the buffer corresponding with the field plot area. Three sets of predictor variables, comprising band values, vegetation indices and texture variables, were extracted. Statistical models incorporating GSV and the remotely sensed predictor variables were developed using ordinary least square (OLS) and Random Forest regression. The results showed that the OLS linear model fitted using texture-based variables was the best among the parametric models with a relative root mean square error (RMSEr) of 41.28%. Likewise, the Random Forest model fitted using the combination of all predictor variables was best among the nonparametric models with a RMSEr of 37.8%. Generally, the Random Forest model was the best model, which was used to produce cell-wise predictions across the entire AOI. The mean GSV for the entire AOI predicted using a Random Forest was 152 m3 ha-1 and the standard deviation was 53.9 m3 ha-1. The estimated mean GSV was similar to the field-measured mean GSV of 160.7 m3 ha-1. The standard deviation was relatively lower compared to the field-based value, which was 76.47 m3 ha-1. Thus, our study demonstrates that Sentinel-2 remotely sensed data can be used to develop a cost-effective method for GSV estimation in the small-scale plantations of Tanzania.
Accurate estimation of timber volume is crucial for successful forest management. In tropical forests, high species diversity and the variability of tree biometric attributes increase the difficulty of developing highly accurate generic and/or specific models. One potential solution is the development of species-specific or species-group volumetric models based on similar structural characteristics. This study aimed to fit multispecific volumetric models and to compare the performance of the same models when applied to groups of species with similar characteristics and, finally, to individual species, in order to predict the tree volume of Hymenaea courbaril L. (Jatob & aacute;) and Piptadenia suaveolens Miq. (Timborana) in a Forest Management Area in the Brazilian Amazon. Ten volumetric models were tested, with and without the inclusion of commercial height. The dataset was divided into two subsets: 70% for parameter estimation and 30% for validation of model generalisation. The best model was selected using statistical criteria, such as the adjusted coefficient of determination, residual standard error, Akaike information criterion, and the prediction residual error sum of squares. Residual normality, homoscedasticity and independence were assessed using diagnostic plots and statistical tests, while multicollinearity was evaluated using the variance inflation factor. The logarithmic Husch and Schumacher-Hall models showed the best fit and satisfied the assumptions of linear regression, and thus are recommended for predicting the individual tree volume for these species. However, the Husch model is more practical and introduces less bias, as it relies solely on diameter as the predictor variable.
This study aimed to evaluate distance-dependent and distance-independent competition indices and their effect in modelling the periodic annual increment in diameter (PAId) of five tree species in a Mixed Ombrophilous Forest. Data were recorded from permanent plots installed and monitored every 3 years in the period 2002-2017 in the National Forest of Irati, Paran & aacute;, Brazil. Ten distance-dependent and distance-independent competition indices were evaluated based on Spearman's correlation coefficient between each index and the periodic annual increment in diameter over the study period (15 years), evaluating the selection range of competing neighbours in the distance-dependent competition indices. Individual tree models were also developed to estimate the PAId of each species and for all forest species with four different approaches (depending on the competition indices tested) by the 'stepwise' procedure. All distance-independent indices generally showed moderate correlation with the growth of individual trees, with an emphasis on the Stage, Corona and Ferrara, Glover and Hool, and Lorimer indices. The distance- dependent competition indices showed stronger correlations with PAId using radii of 10, 15, 17 and 20 m. The PAId models, derived from 3-year monitoring periods and incorporating intermediate diameter as an input variable, consistently produced superior estimates compared to the other models, although their practical application is difficult. This study provides insights into the inclusion of competition indices in diameter increment models in the context of individual tree-level modelling in Mixed Ombrophilous Forest.
Manual planting methods remain the primary way of regenerating forest stands in southern Africa, but mechanised planting machines are attracting increasing interest due to their reduced labour requirements, better ergonomics and safety. This study analyses the performance of the first fully mechanised planter deployed in the region and offers information on the productivity, work quality and tree performance (survival and growth at 3, 6, 9 and 12 months) achieved with a single-head excavator-based planting machine in Eswatini. The machine was run alternately by two operators and tested on 17 plots distributed across two study sites while planting Eucalyptus smithii seedlings at 1 667 stems ha-1. Time and motion studies were used to gather and analyse productivity (plants planted per productive machine hour (PMH)), followed by post-planting assessments to rate mechanised work quality. Productivity averaged 165 plants PMH-1, excluding delays. Mechanical availability was 71% and machine utilisation was 56%. Machine productivity was higher on the site with a low residue load. Operator 1 achieved 30% higher productivity than Operator 2 on the site with a higher residue load. The mechanised planting cost was US$1 015 ha-1. Half of the seedlings were planted correctly. Initial tree survival was lower than that of manually planted trees, but differences evened out after 12 months. Tree growth was higher on the site with a higher residue load. The study serves as a baseline for future mechanised planting performance assessments in the southern African region.
Understanding the radial and longitudinal variation in wood density provides insights into the physiological properties of xylem tissue, particularly hydraulic conductivity. This study aimed to assess the functional characteristics of xylem, including anatomical, hydraulic and physicochemical properties, in both radial (heartwood and sapwood) and longitudinal positions within tropical trees. Samples were collected from a managed forest area in Amazonas, Brazil. The study hypothesised that functional traits would differ among species from distinct ecological groups (medium and high wood density). The results indicated a reduction in wood density in both radial and longitudinal directions. Aqueous extractive content ranged from 3.75% to 17.22%, with no significant differences between density groups, heartwood and sapwood, or bottom and top positions. Vessel diameter ranged from 94.45 & micro;m to 247.71 & micro;m. Hydraulic conductivity was highest in the medium density group (0.50-0.70 g cm-3), indicating a potential trade-off between water transport efficiency and mechanical resistance. The elucidated relationships between chemical characteristics (aqueous extractives) and anatomical traits (vessel diameter) provide insight about classifying tropical tree species according to their wood density.
Tree canopy height is one of the most important indicators of aboveground biomass density, productivity and ecosystem structure in forests. The newest released global canopy height models as of 2023 are the 10 m spatial resolution High Resolution Canopy Height Model of the Earth (HRCH) and the first Global Map of Tree Canopy Height (GMTCH) at 1 m spatial resolution. The accuracy of both maps was mostly assessed with independent airborne laser scanning (ALS) data in boreal and temperate forests of the USA, Europe and Oceania, with limited validation datasets in tropical regions. This study aimed to provide an accuracy assessment of high and very high spatial resolution global canopy height maps in Andean Patagonian forests by comparing them with independent unmanned aerial vehicle (UAV)-mounted LiDAR datasets. The mean error of HRCH showed a positive vertical offset within a 2.7-6.6 m range, and the root mean square error (RMSE) values varied from 4.4 m to 8.8 m. In the more complex broadleaf native forests with dense canopies and steep slopes, HRCH underestimated canopy heights. Mean errors of GMTCH indicated a negative vertical offset from -2.1 m to -13.3 m at all study sites, and RMSE values ranged from 4.0 m to 14.9 m. HRCH tended to overestimate the height of low canopies and underestimate the tall ones, whereas GMTCH strongly underestimated the height of all canopies, regardless of their height. Global canopy height models represent a significant advancement in mapping forest attributes and offer new opportunities to obtain deeper insight into forests worldwide. According to the findings, we recommend using both global maps for height estimates as ancillary information at a regional level. The increased availability of ALS and UAV-mounted LiDAR databases in poorly surveyed areas, especially in South America and Africa, will strengthen the robustness of accuracy assessments for global canopy height models.
Plantation forestry in Tanzania is expanding to meet the growing demand for timber for construction, transmission poles and other wood products. However, limited site-specific information constrains the selection of suitable eucalypt species for different environments. This study assessed the growth performance and yield of 40 eucalypt entries, comprising 38 pure species/provenances and two hybrid clones (Eucalyptus grandis & times; E. camaldulensis from Green Resources Ltd; GRL) as a control group, 8 years after planting at Wino Forest Plantation in the Ruvuma region, southern Tanzania. Measurements included survival rate, diameter at breast height (DBH) and total height, from which basal area and volume were derived. Significant variation was observed among entries. The hybrid GC15_GRL achieved the highest survival (98%), while E. urophylla (South African Pulp and Paper Industries; SAPPI) exhibited the largest mean DBH (23.2 cm) and the highest standing volume (539.9 m3ha-1). The hybrid GC584_GRL attained the greatest height (28.0 m). An integrated performance ranking identified GC584_GRL, E. urophylla (SAPPI), GC15_GRL, E. grandis (Merensky) and E. saligna (Republic of South Africa) as the most productive and reliable entries. These results provide critical, locally validated evidence to guide species selection for sustainable plantation forestry in the southern Highlands of Tanzania and similar subtropical highland environments.
The Southern African Development Community (SADC) responded to global calls to address environmental challenges such as high greenhouse gas (GHG) emissions through the use of liquid biofuels. This study assessed the potential of liquid biofuel production in the SADC region with data collected in Malawi, Mozambique, South Africa and Zimbabwe. The results showed that the liquid biofuel industry is struggling. Countries do not have enough resources to support the industry effectively and there is overreliance on international sponsors. In terms of policy and regulatory frameworks most countries are doing well. However, these policies are not implemented effectively. Most countries use sugar-cane to produce bioethanol. Over the years countries, such as Malawi, have attempted to incorporate crops such as cassava (Manihot esculenta) and castor bean (Ricinus communis). Although the industry is not performing well it has contributed massively to livelihood development in all the region.
Most South African planted forests occur in high wildfire risk regions, with firebreaks used to minimise the risk of run-away fires. Desiccant herbicides together with burning are used for firebreak preparation in a stepwise manner. In late summer, 1-2 m wide tracer-lines are sprayed on either side of the proposed firebreak. Once desiccated, the vegetation in the tracer-lines is burned, with the green vegetation remaining between the tracer-lines and outside of the firebreak preventing the spread of fire. In autumn, following the seasonally induced die-back of vegetation (due to frosts and reduced rainfall), the vegetation remaining between these tracer-lines is burned, thus creating a larger buffer (firebreak), free from combustible material for the management of unplanned fires. To test the efficacy of pelargonic acid as a replacement for paraquat (highly hazardous due to acute toxicity and high bioaccumulation), four trials were implemented. In addition to a no-spray control and the use of paraquat (current standard), different rates of pelargonic acid (6/8/10%) with, or without ammonium sulfate were tested to determine the most robust treatment across different vegetation types. Glufosinate-ammonium was included for comparative purposes. Paraquat resulted in the highest degree of desiccation 7-8 days after application, with glufosinate-ammonium being the least effective. Desiccation was further increased at higher rates of pelargonic acid application (10 > 8 > 6%), with glufosinate-ammonium improving desiccation further. Pelargonic acid applied at 10% with the addition of ammonium-sulphate was most similar to that of paraquat.
Black wattle (Acacia mearnsii) was introduced to southern Brazil in the 1930s without any documented history of microbial inoculation. This study tested the hypothesis that black wattle introduction does not harm indigenous arbuscular mycorrhizal fungi (AMF) communities or reduce soil AMF inoculum potential, probably because the species readily associates with a diverse range of native AMF. Soil samples were collected from areas with different land uses (native forest fragments, native pasture and black wattle plantations) and used in two greenhouse experiments. Experiment 1 assessed the inoculum potential of soils from different land uses by evaluating AMF root colonisation in Brachiaria (Urochloa brizantha) seedlings. Experiment 2 used Brachiaria and black wattle seedlings as trap plants to assess AMF spore diversity in the soil samples. AMF species were identified based on spore morphotypes. Results indicated that black wattle plantations did not significantly alter soil inoculum potential or AMF spore diversity, except in cases where soil P content was substantially affected by the plantation. Black wattle readily formed symbioses with diverse AMF communities upon introduction to a new environment. The most frequently observed AMF morphotypes in the black wattle rhizosphere were Claroideoglomus etunicatum and Rhizoglomus clarum, followed by Archaeospora trappei, Acaulospora colombiana, Acaulospora mellea, and two unidentified Glomus species. These findings align with the observation that black wattle has successfully adapted to the AMF diversity of southern Brazilian ecosystems.
Talbotiella gentii Hutch. & Greenway is an endemic, severely threatened and fragmented species in Ghana. Though it is a highly valued non-timber product, it faces the threat of extinction from wildfire, and exploitation for charcoal and fuelwood, agriculture and building purposes. Efforts made by the Forestry Commission of Ghana to protect Talbotiella have focused on populations in reserves only while off-reserve populations are at the mercy of local farmers. The first updated data set of Talbotiella was collected in 2004. An entirely new Talbotiella population with about 197 trees near Okpe river and believed to belong to the river god was discovered at Anum Boso in the Eastern region of Ghana in 2006. Protection solely by the river god has safeguarded the population against wildfire, removal for fuelwood and charcoal production. Despite unique morphological characteristics that the population possesses, including tree size and height, no studies have been done on its genetic diversity. This study therefore investigated uniqueness in genotypes of the Okpe river Talbotiella population alongside four other best recorded genotypes of Talbotiella populations. Six out of 10 primers tested revealed 44 polymorphic bands. A PHIst value of 0.941 revealed by analysis of molecular variance (AMOVA) indicated limited gene flow and high risk of inbreeding among individuals. Squared Euclidean distances clearly showed that Okpe Talbotiella is closest to the best recorded genotypes and is therefore recommended for seed collection for conservation of Talbotiella in Ghana through in situ and ex situ methods.
The aim of this study was to investigate the morphophysiology of young eucalypt clones in response to different water regimes and paclobutrazol (PBZ) concentrations applied to the soil. The experiment was conducted in a greenhouse environment at the Federal University of Acre, Rio Branco, Brazil. Commercial clones of Eucalyptus urophylla x E. camaldulensis hybrid were planted in 11 l pots using a randomised block design in four blocks arranged at a 5 x 3 factorial scheme. Five PBZ concentrations were applied through substrate - 0.0 (control), 1.0, 2.0, 4.0 and 8.0 mg plant-1 - and three water regimes were used (40%, 70% and 100% field capacity (FC)). Results indicated that PBZ promoted morphological changes in the investigated species without affecting its physiological features. Eucalypt clones recorded increased root dry mass and decreased shoot/root ratio (S:R) after the application of 8.0 mg plant-1 of PBZ. Treatment conducted with 100% FC may have contributed to the hypoxic condition of the roots, and the limited plant height and S:R ratio. The 70% FC water regime increased plant height, stem diameter, leaf area, dry mass accumulation and CO2 partial pressure, and plants subjected to 40% FC recorded higher carboxylation and water use efficiency.
Timber features as an important commodity in the trade portfolio of some African countries as it is accessible, lucrative, and necessary for construction and development. For these reasons, the supply of timber has implications for sustainable development. This research evaluated the determinants of the supply of timber in Cameroon. Since time series data were employed, an econometric technique via the Autoregressive Dynamic Lag approach was used to establish the relationship between annual hardwood harvest and observed economic conditions. The conditional unrestricted equilibrium correction model showed a positive and significant correlation between timber supply and prices, and between income and road infrastructure. The findings captured the dynamic nature of the country's forest sector and enumerated the drivers of a sustainable timber supply. There is a need for policies and programmes aimed at enhancing and guiding timber harvest rates and supply, and for investments in road infrastructure and other broad-based interventions that ensure guided access to concession sites.
Accurately quantifying stump volume on post-harvested sites is required to assess potential volume gains for biomass utilisation. The relatively uniform distribution and shape of stumps across such sites makes them well-suited for detection using machine learning (ML) algorithms. Recent developments in the analysis of Digital Aerial Photogrammetry (DAP) data acquired by unmanned aerial vehicles (UAVs) have enabled the reliable identification of stumps via advanced ML methods. Furthermore, the processed outputs from these algorithms provide estimates of stump diameter and height, facilitating calculations of biomass volume. This integration of UAV-based photogrammetry and ML techniques presents a promising approach for enhancing forest management and biomass assessment. In this study, we trained three different ML model types: Faster Region-based Convolutional Neural Network (R-CNN), Single Shot Multibox Detector (SSD) and You-Only-Look-Once (YOLO). The data for the virtual stump detections came from two Norwegian sites, with stumps of Picea abies (L.) H.Karst., and three South African sites, with stumps of Pinus patula Schiede ex Schltdl. & Cham. We assessed the detection rates of each model and compared metrics by using similarly annotated images. The resultant encapsulating bounding boxes of detected stumps were used to calculate diameters and compared to field measurements. Each bounding box is rectangular in shape, and the average of the height and width was calculated to get an estimated diameter value. Virtual stump heights were determined from the Digital Surface Model (DSM) by subtracting the mean height of the surrounding area from the mean height of the stump. The calculated heights of the stumps can be used to assess potential loss of wood volume due to inefficient harvesting techniques. Similarly, the calculated wood volume can be used to estimate residual biomass, and therefore assist Foresters in deciding how best to utilise these stumps. Visible stumps on post-harvested sites could be detected with high rates of accuracy, with almost perfect precision from some object detection models, albeit at low levels of recall. Overall, all three model types had an F1-score of above 73% with the best model attaining an F1-score of 89%. Stump diameters were generally overestimated and this was not found to be related to stump size. Stump heights were underestimated in most cases.
This study employs Landsat satellite imagery, interpolated meteorological data and the Surface Energy Balance Algorithm for Land (SEBAL) to estimate the energy balance and evapotranspiration (ET) within the Itupararanga Environmental Protection Area (Itupararanga EPA), located in the Atlantic Forest biome of Brazil. The results indicate that urban areas show the lowest average daily evapotranspiration (ET24) values, whereas water bodies and vegetated areas have the highest ET24 values. Urban areas also recorded the highest surface albedo (alpha) values across all years analysed. While there was a general trend of increasing net radiation values over time - leading to higher evapotranspiration rates, with peak values observed in 2021 - this trend does not suggest a direct correlation between net radiation and ET. This underscores the critical role of land cover in modulating water fluxes. Zonal statistical analysis revealed that agricultural areas contributed more to ET than pastures, whereas forests and forestry areas exhibited similar impacts on ET. Land-use changes were found to significantly influence ET; urban areas, in particular, retained more heat and had reduced energy availability for evapotranspiration. This research enhances the understanding of the energy balance within the Itupararanga EPA and provides valuable data to support water resource management and environmental conservation efforts.
Melanterius is a large genus of small weevils that primarily feed on the seeds of Acacia species occurring in their native range in Australia. In the latter part of the 20th century, five seed-feeding Melanterius species were released against several weedy Acacia species in South Africa as biological control agents. In early 2024, Melanterius weevils were detected damaging the vegetative plant tissues of trees in a commercial black wattle (Acacia mearnsii) compartment in the KwaZulu-Natal, South Africa. Morphological identification and DNA sequencing revealed that the weevils represent the species Melanterius inconspicuus, which is not one of the five species introduced in South Africa. This finding represents the first record of this Melanterius species outside of its native range in Australia and infesting black wattle, as well as the first record of a Melanterius species infesting vegetative tissues.
