Research Articles (Forest and Wood Science)

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Aboveground biomass and carbon in a South African mistbelt forest and the relationships with tree species diversity and forest structures
(MDPI, 2016) Mensah, Sylvanus; Veldtman, Ruan; Du Toit, Ben; Kakai, Romain Glele; Seifert, Thomas
ENGLISH ABSTRACT: Biomass and carbon stocks are key information criteria to understand the role of forests in regulating global climate. However, for a bio-rich continent like Africa, ground-based measurements for accurate estimation of carbon are scarce, and the variables affecting the forest carbon are not well understood. Here, we present the first biomass study conducted in South Africa Mistbelt forests. Using data from a non-destructive sampling of 59 trees of four species, we (1) evaluated the accuracy of multispecies aboveground biomass (AGB) models, using predictors such as diameter at breast height (DBH), total height (H) and wood density; (2) estimated the amount of biomass and carbon stored in the aboveground compartment of Mistbelt forests and (3) explored the variation of aboveground carbon (AGC) in relation to tree species diversity and structural variables. We found significant effects of species on wood density and AGB. Among the candidate models, the model that incorporated DBH and H as a compound variable (DBH2 × H) was the best fitting. AGB and AGC values were highly variable across all plots, with average values of 358.1 Mg·ha−1 and 179.0 Mg·C·ha−1, respectively. Few species contributed 80% of AGC stock, probably as a result of selection effect. Stand basal area, basal area of the ten most important species and basal area of the largest trees were the most influencing variables. Tree species richness was also positively correlated with AGC, but the basal area of smaller trees was not. These results enable insights into the role of biodiversity in maintaining carbon storage and the possibilities for sustainable strategies for timber harvesting without risk of significant biomass decline.
Agroforestry : an appropriate and sustainable response to a changing climate in Southern Africa?
(MDPI, 2020-08-21) Sheppard, Jonathan P.; Reckziegel, Rafael Bohn; Borrass, Lars; Chirwa, Paxie W.; Cuaranhua, Claudio J.; Hassler, Sibylle K.; Hoffmeister, Svenja; Kestel, Florian; Maier, Rebekka; Mälicke, Mirko; Morhart, Christopher; Ndlovu, Nicholas P.; Veste, Maik; Funk, Roger; Lang, Friederike; Seifert, Thomas; Du Toit, Ben; Kahle, Hans-Peter
ENGLISH ABSTRACT: Agroforestry is often discussed as a strategy that can be used both for the adaptation to and the mitigation of climate change e ects. The climate of southern Africa is predicted to be severely a ected by such changes. With agriculture noted as the continent’s largest economic sector, issues such as food security and land degradation are in the forefront. In the light of such concerns we review the current literature to investigate if agroforestry systems (AFS) are a suitable response to the challenges besetting traditional agricultural caused by a changing climate. The benefits bestowed by AFS are multiple, o ering ecosystem services, influence over crop production and positive impacts on rural livelihoods through provisioning and income generation. Nevertheless, knowledge gaps remain. We identify outstanding questions requiring further investigation such as the interplay between trees and crops and their combination, with a discussion of potential benefits. Furthermore, we identify deficiencies in the institutional and policy frameworks that underlie the adoption and stimulus of AFS in the southern African region. We uphold the concept that AFS remains an appropriate and sustainable response for an increased resilience against a changing climate in southern Africa for the benefit of livelihoods and multiple environmental values.
Analysing taxonomic structures and local ecological processes in temperate forests in North Eastern China
(BioMed Central, 2017) Fan, Chunyu; Tan, Lingzhao; Zhang, Chunyu; Von Gadow, Klaus
Background: One of the core issues of forest community ecology is the exploration of how ecological processes affect community structure. The relative importance of different processes is still under debate. This study addresses four questions: (1) how is the taxonomic structure of a forest community affected by spatial scale? (2) does the taxonomic structure reveal effects of local processes such as environmental filtering, dispersal limitation or interspecific competition at a local scale? (3) does the effect of local processes on the taxonomic structure vary with the spatial scale? (4) does the analysis based on taxonomic structures provide similar insights when compared with the use of phylogenetic information? Based on the data collected in two large forest observational field studies, the taxonomic structures of the plant communities were analyzed at different sampling scales using taxonomic ratios (number of genera/number of species, number of families/number of species), and the relationship between the number of higher taxa and the number of species. Two random null models were used and the “standardized effect size” (SES) of taxonomic ratios was calculated, to assess possible differences between the observed and simulated taxonomic structures, which may be caused by specific ecological processes. We further applied a phylogeny-based method to compare results with those of the taxonomic approach. Results: As expected, the taxonomic ratios decline with increasing grain size. The quantitative relationship between genera/families and species, described by a linearized power function, showed a good fit. With the exception of the family-species relationship in the Jiaohe study area, the exponents of the genus/family-species relationships did not show any scale dependent effects. The taxonomic ratios of the observed communities had significantly lower values than those of the simulated random community under the test of two null models at almost all scales. Null Model 2 which considered the spatial dispersion of species generated a taxonomic structure which proved to be more consistent with that in the observed community. As sampling sizes increased from 20 m × 20 m to 50 m × 50 m, the magnitudes of SESs of taxonomic ratios increased. Based on the phylogenetic analysis, we found that the Jiaohe plot was phylogenetically clustered at almost all scales. We detected significant phylogenetically overdispersion at the 20 m × 20 m and 30 m × 30 m scales in the Liangshui plot. Conclusions: The results suggest that the effect of abiotic filtering is greater than the effects of interspecific competition in shaping the local community at almost all scales. Local processes influence the taxonomic structures, but their combined effects vary with the spatial scale. The taxonomic approach provides similar insights as the phylogenetic approach, especially when we applied a more conservative null model. Analysing taxonomic structure may be a useful tool for communities where well-resolved phylogenetic data are not available.
Assessing biological dissimilarities between five forest communities
(SpringerOpen (part of Springer Nature), 2019-06-06) Hao, Minhui; Corral-Rivas, J. J.; Gonzalez-Elizondo, M. S.; Ganeshaiah, K. N.; Nava-Miranda, M. G.; Zhang, Chunyu; Zhao, Xiuhai; Von Gadow, Klaus
Background: Dissimilarity in community composition is one of the most fundamental and conspicuous features by which different forest ecosystems may be distinguished. Traditional estimates of community dissimilarity are based on differences in species incidence or abundance (e.g. the Jaccard, Sørensen, and Bray-Curtis dissimilarity indices). However, community dissimilarity is not only affected by differences in species incidence or abundance, but also by biological heterogeneities among species. Methods: The objective of this study is to present a new measure of dissimilarity involving the biological heterogeneity among species. The “discriminating Avalanche” introduced in this study, is based on the taxonomic dissimilarity between tree species. The application is demonstrated using observations from five stem-mapped forest plots in China and Mexico. We compared three traditional community dissimilarity indices (Jaccard, Sørensen, and Bray-Curtis) with the “discriminating Avalanche” index, which incorporates information, not only about species frequencies, but also about their taxonomic hierarchies. Results: Different patterns emerged for different measures of community dissimilarity. Compared with the traditional approaches, the discriminating Avalanche values showed a more realistic estimate of community dissimilarities, indicating a greater similarity among communities when species were closely related. Conclusions: Traditional approaches for assessing community dissimilarity disregard the taxonomic hierarchy. In the traditional analysis, the dissimilarity between Pinus cooperi and Pinus durangensis would be the same as the dissimilarity between P. cooperi and Arbutus arizonica. The dissimilarity Avalanche dissimilarity between P. cooperi and P. durangensis is considerably lower than the dissimilarity between P. cooperi and A. arizonica, because the taxonomic hierarchies are incorporated. Therefore, the discriminating Avalanche is a more realistic measure of community dissimilarity. This main result of our study may contribute to improved characterization of community dissimilarities.
Atomic force microscopy to determine the surface roughness and surface polarity of cell types of hardwoods commonly used for pulping
(Academy of Science for South Africa, 2007) Meincken, M.
ATOMIC FORCE MICROSCOPY CAN BE USED to determine the surface roughness and surface polarity of different cell types originating from hardwood species. This analytical method allows images representing the topography and polarity of a surface to be captured simultaneously at a molecular (nanometre) resolution. The distribution of hydrophilic (polar) groups on these cell surfaces influences the subsequent processing of woodpulp in paper manufacture. These surface properties of fibres, vessel elements and parenchyma cells were investigated for Acacia mearnsii, Eucalyptus grandis, E. dunnii and E. macarthurii. A clear distinction was observed between the cell types and the species in terms of polarity and surface roughness. All four species are currently being used for paper manufacture in South Africa, but not with equal success. This study may help to explain the differences in pulp quality obtained for the various species.
Bioenergy use and food preparation practices of two communities in the Eastern Cape Province of South Africa
(Energy Research Centre, 2010) Chirwa, Paxie W.; Ham, Cori; Maphiri, Stella; Balmer, Marlett
A study was undertaken in two communities that use firewood in the Keiskammahoek area of the Eastern Cape Province of South Africa to understand their behaviour with regard to energy use during food preparation as well as the extent of practising efficient cooking habits. The results showed that despite the high level of electrification, firewood was used in most households (B 60%) for cooking while electricity was mostly used (B 90%) for lighting. Firewood is also preferred for cooking food that takes a long time to prepare, while more convenient sources of energy such as electricity is used for short periods of cooking and re-heating of food. Secondary sources of energy used for cooking included paraffin, dung, leaves and twigs. The study found that there was some deliberate use of energy saving techniques in both communities, although limited and not necessarily practiced with a view to saving energy. Less than half of the respondents soaked hard grains and beans before cooking; while all of them cut food into smaller pieces before cooking commenced. A third of respondents had utensils ready before cooking commenced in one village while two thirds placed utensils and food together before they commenced food preparations in the other village. Pots were covered with lids and water was added in small amounts as required. The heat from fire was not monitored, but fires were extinguished after use. The greatest potential for improvement exists around cooking appliances; where all households were found to be using threelegged pots on open fires when cooking with biomass energy. Open fires are highly inefficient and the use of efficient biomass cook stoves would increase efficiency. It is recommended that in order to reduce the use of biomass-derived energy consumption and expenditure in low-income households, the use of multiple energy sources and portable energy efficient firewood stoves should be promoted. In addition, there should be an aggressive dissemination of information on further processing of fuelwood into forms that can easily be stored and used; and various forms of pre-treatment of hard foods.
Characteristics of selected non-woody invasive alien plants in South Africa and an evaluation of their potential for electricity generation
(University of Cape Town, Energy Research Centre, 2017) Melane, Mandlakazi; Ham, Cori; Meincken, Martina
ENGLISH ABSTRACT: Alien invasive plants (AIPs) pose a threat to the existence of plant and animal biodiversity in the ecosystems they invade. They need to be cleared, monitored and eventually eradicated from the landscape. The potential and the economic viability to supply non-woody AIP biomass for electricity generation were assessed in this study, which was conducted on samples from 13 common non-woody AIPs in South Africa, namely: Arundo donax (giant reed), Lantana camara (lantana), Pontederia cordata (pickerel weed), Ricinus communis (castor-oil plant), Opuntia ficus-indica (sweet prickly pear), Solanum mauritianum (bugweed), Atriplex nummularia (saltbush), Cestrum laevigatum (inkberry), Senna didymobotrya (peanut butter cassia), Chromoleana odorata (chromoleana), Eichhornia crassipes (water hyacinth), Cerus jamacaru (queen of the night) and Agave sisilana (sisal plant). Proximate and ultimate analysis was made in order to assess the suitability of the biomass for different thermo-chemical conversion techniques for electricity generation. A financial evaluation of the costs to supply biomass to the plant gate was performed by combining the harvesting, chipping and transport costs. The results showed that the biomass of giant reed, lantana, bugweed, saltbush, inkberry, cassia and Chromoleana may be used to generate electricity through combustion, although the total average cost was approximately 50% higher than that of woody biomass feedstock, requiring a ‘fuel cost subsidy’ to justify their utilisation for energy production.
Climate as possible reproductive barrier in Pinus radiata (D. Don) interspecific hybridisation
(Marin Dracea National Research-Development Institute in Forestry, 2017) Ham, H.; Botha, A. M.; Kanzler, A.; Du Toit, B.
Historically, interspecific hybridisation with Pinus radiata D. Don had limited success. The effect of environmental conditions and position of pollination bags in the tree were investigated as possible hybridisation barriers. The study was conducted in a P. radiata seed orchard in the Southern Cape (South Africa). Field data were compared to the climatic conditions at natural and commercial provenances of seven Mesoamerican Pinus species identified as possible hybrid partners. In vitro pollen studies were used to confirm whether interspecific crosses with P. radiata might be feasible within predefined climatic parameters. The temperature ranges for both top and northern side of P. radiata pine trees in the seed orchard was similar to the natural distribution of P. radiata, P. elliottii Engelm. and P. taeda L. in the USA. Results suggested that pollen of P. elliottii and P. taeda might be more suited to result in the successful pollination of P. radiata than the other Mesoamerican pine species tested in this study. Furthermore, the combination of minimum temperature and precipitation also showed a closer correlation to successful hybridisation with P. radiata for both P. elliotii and P. taeda. However, pollen tube elongation studies did not support these results, suggesting that mean temperature might not be the only determining factor of hybridisation success. Three circadian temperature models that mimic natural conditions were developed for Karatara and Sabie (Tweefontein, Witklip and Spitskop). These models will be tested in future in vitro studies to further evaluate temperature fluctuations between day and night regimes as a possible reproductive barrier limiting hybridisation success between P. radiata and other Mesoamerican pine species.
Climate change effects in the Western Himalayan ecosystems of India : evidence and strategies
(SpringerOpen, 2017) Tewari, Vindhya Prasad; Verma, Raj Kumar; Von Gadow, Klaus
Background: The fragile landscapes of the Himalayan region are highly susceptible to natural hazards, and there is ongoing concern about current and potential climate change impacts. This study provides background information on India’s Western Himalayas and reviews evidence of warming as well as variability in precipitation and extreme events. Methods: Understanding and anticipating the impacts of climate change on Himalayan forest ecosystems and the services they provide to people are critical. Efforts to develop and implement effective policies and management strategies for climate change mitigation and adaptation requires particular new research initiatives. The various studies initiated and conducted in the region are compiled here. Results: Several new initiatives taken by the Himalayan Forest Research Institute in Shimla are described. This includes new permanent observational field studies, some with mapped trees, in high altitude transitional zones for continuous monitoring of vegetation response. We have also presented new strategies for mitigating potential climate change effects in Himalayan forest ecosystems. Conclusions: Assessment of the ecological and genetic diversity of the Himalayan conifers is required to evaluate potential responses to changing climatic conditions. Conservation strategies for the important temperate medicinal plants need to be developed. The impact of climate change on insects and pathogens in the Himalayas also need to be assessed. Coordinated efforts are necessary to develop effective strategies for adaptation and mitigation
Comparing Johnson’s SBB, Weibull and Logit-Logistic bivariate distributions for modeling tree diameters and heights using copulas
(Instituto Nacional de Investigacion y Tecnología Agraria y Alimentaria, 2016-04) Gorgoso-Varela, Jose J.; Garcia-Villabrille, Juan Daniel; Rojo-Alboreca, Alberto; Von Gadow, Klaus; Alvarez-Gonzalez, Juan Gabriel
Aim of study: In this study we compare the accuracy of three bivariate distributions: Johnson’s SBB, Weibull-2P and LL-2P functions for characterizing the joint distribution of tree diameters and heights. Area of study: North-West of Spain. Material and methods: Diameter and height measurements of 128 plots of pure and even-aged Tasmanian blue gum (Eucalyptus globulus Labill.) stands located in the North-west of Spain were considered in the present study. The SBB bivariate distribution was obtained from SB marginal distributions using a Normal Copula based on a four-parameter logistic transformation. The Plackett Copula was used to obtain the bivariate models from the Weibull and Logit-logistic univariate marginal distributions. The negative logarithm of the maximum likelihood function was used to compare the results and the Wilcoxon signed-rank test was used to compare the related samples of these logarithms calculated for each sample plot and each distribution. Main results: The best results were obtained by using the Plackett copula and the best marginal distribution was the Logit-logistic. Research highlights: The copulas used in this study have shown a good performance for modeling the joint distribution of tree diameters and heights. They could be easily extended for modelling multivariate distributions involving other tree variables, such as tree volume or biomass.
A comparison of two methods of data collection for modelling productivity of harvesters : manual time study and follow-up study using on-board-computer stem records
(Marin Dracea National Research-Development Institute in Forestry, 2018) Brewer, J.; Talbot, B.; Belbo, H.; Ackerman, P.; Ackerman, S.
Abstract. Productivity of a mechanized P. patula cut-to-length harvesting operation was estimated and modelled using two methods of data collection: manual time study and follow-up study using StanForD stem files. The objective of the study was to compare the productivity models derived using these two methods to test for equivalence. Manual time studies were completed on four different machines and their operators. Two Ponsse Bear harvesters fitted with H8 heads, and two Ponsse Beaver harvesters, fitted with H6 heads, were included. All machines were equipped with Ponsse Opti2 information system. All four operators had approximately 1 year of experience working with their respective machines. The four machines worked in separate four-tree-wide harvesting corridors, and they each harvested 200 trees. Individual tree diameter at breast height (DBH), and height measurements were made manually. Subsequently, data on the trees in each study were extracted from the StanForD stem reports from each of the harvesters. Cycle times in the stem reports were determined based on the difference between consecutive harvest timestamps. The two methods were compared in terms of their abilities to estimate equivalent measures for tree DBH, volume, and productivity. In all four cases, significant differences were found between the DBH and volume measures derived using the two methods. Subsequently, the volume measures from the manual methods were used as the basis for productivity calculations. Results of the productivity comparisons found no significant differences between the models developed from the two methods. These results suggest that equivalent productivity models can be developed in terms of time using either method, however volume discrepancies indicate a need to reconcile bark and volume functions with the high variability experienced in the country.
Development and validation of a photo-based measurement system to calculate the debarking percentages of processed logs
(MDPI, 2019) Heppelmann, Joachim B.; Labelle, Eric R.; Seifert, Thomas; Seifert, Stefan; Wittkopf, Stefan
ENGLISH ABSTRACT: Within a research project investigating the applicability and performance of modified harvesting heads used during the debarking of coniferous tree species, the actual debarking percentage of processed logs needed to be evaluated. Therefore, a computer-based photo-optical measurement system (Stemsurf) designed to assess the debarking percentage recorded in the field was developed, tested under laboratory conditions, and applied in live field operations. In total, 1720 processed logs of coniferous species from modified harvesting heads were recorded and analyzed within Stemsurf. With a single log image as the input, the overall debarking percentage was calculated by further estimating the un-displayed part of the log surface by defining polygons representing the differently debarked areas of the log surface. To assess the precision and bias of the developed measurement system, 480 images were captured under laboratory conditions on an artificial log with defined surface polygons. Within the laboratory test, the standard deviation of average debarking percentages remained within a 4% variation. A positive bias of 6.7% was caused by distortion and perspective effects. This resulted in an average underestimation of 1.1% for the summer debarking percentages gathered from field operations. The software generally performed as anticipated through field and lab testing and offered a suitable alternative of assessing stem debarking percentage, a task that should increase in importance as more operations are targeting debarked products.
Drivers of seedling survival in a temperate forest and their relative importance at three stages of succession
(John Wiley & Sons Ltd., 2015-09-10) Yan, Yan; Zhang, Chunyu; Wang, Yuxi; Zhao, Xiuhai; Von Gadow, Klaus
Negative density dependence (NDD) and niche partitioning have been perceived as important mechanisms for the maintenance of species diversity. However, little is known about their relative contributions to seedling survival. We examined the effects of biotic and abiotic neighborhoods and the variations of biotic neighborhoods among species using survival data for 7503 seedlings belonging to 22 woody species over a period of 2 years in three different forest types, a half-mature forest (HF), a mature forest (MF), and an old-growth forest (OGF), each of these representing a specific successional stage in a temperate forest ecosystem in northeastern China. We found a convincing evidence for the existence of NDD in temperate forest ecosystems. The biotic and abiotic variables affecting seedlings survival change with successional stage, seedling size, and age. The strength of NDD for the smaller (<20 cm in height) and younger seedlings (1–2 years) as well as all seedlings combined varies significantly among species. We found no evidence that a community compensatory trend (CCT) existed in our study area. The results of this study demonstrate that the relative importance of NDD and habitat niche partitioning in driving seedling survival varies with seedling size and age and that the biotic and abiotic factors affecting seedlings survival change with successional stage.
Effect of ascorbic acid and yeast strain on sauvignon blanc wine quality
(South African Society for Enology and Viticulture, 2001) Swart, E.; Marais, J.; Britz, T. J.
Sauvignon blanc cultivar-typical aroma is affected by different components of which 2-methoxy-3-isobutylpyrazine and 4-mercapto-4-methylpentan-2-one are probably the most important. Climatic, viticultural and oenological conditions may have a prominent effect on the levels at which these impact aroma components occur in wine. Sauvignon blanc wines were produced from grapes from two climatically different regions. Different ascorbic acid/S02 combinations and different Saccharomyces cerevisiae yeast strains were used during the production of the wines. The wines were sensorially evaluated for specific wine characteristics, namely fruity/ester aroma intensity, grassy/green pepper aroma intensity, sulphur-like aroma intensity and overall wine quality. Significant differences were observed between treatments. A commercially available preparate (ascorbic acid/meta-bisulphite) and yeast strain VL3C produced sulphur-like, low-quality wines under the conditions of this investigation. The highest quality wines were produced from pure ascorbic acid/S02 treatments and fermentation by the yeast strain VIN 13.
Effects of density dependence in a temperate forest in northeastern China
(Springer Nature, 2016-09-08) Yao, Jie; Zhang, Xinna; Zhang, Chunyu; Zhao, Xiuhai; Von Gadow, Klaus
ENGLISH ABSTRACT: Negative density dependence may cause reduced clustering among individuals of the same species, and evidence is accumulating that conspecific density-dependent self-thinning is an important mechanism regulating the spatial structure of plant populations. This study evaluates that specific density dependence in three very large observational studies representing three successional stages in a temperate forest in northeastern China. The methods include standard spatial point pattern analysis and a heterogeneous Poisson process as the null model to eliminate the effects of habitat heterogeneity. The results show that most of the species exhibit conspecific density-dependent self-thinning. In the early successional stage 11 of the 16 species, in the intermediate successional stage 18 of the 21 species and in the old growth stage all 21 species exhibited density dependence after removing the effects of habitat heterogeneity. The prevalence of density dependence thus varies among the three successional stages and exhibits an increase with increasing successional stage. The proportion of species showing density dependence varied depending on whether habitat heterogeneity was removed or not. Furthermore, the strength of density dependence is closely related with species abundance. Abundant species with high conspecific aggregation tend to exhibit greater density dependence than rare species.
Essential environmental variables to include in a stratified sampling design for a national-level invasive alien tree survey
(Italian Society of Silviculture and Forest Ecology, 2020) Kotze , Johann D. F.; Beukes , Hein B.; Seifert , Thomas
ENGLISH ABSTRACT: There is a direct relationship between the abundance of biological invasions and their impact, which means that it is important to capture spatial patterns in their abundance and use this information to focus management actions. However, protocols to objectively determine invasive alien plant (IAP) distributions and abundance are lacking at a national level, resulting in the inability to determine and monitor changes in spatial extent and density over time. A complete inventory of IAP spatial distribution across an extensive area such as South Africa is not possible and so requires an efficient sampling approach. A simple random sampling design would not be efficient, so monitoring of IAP species at a national level requires an appropriate sampling design such as a stratified sampling. The selection of environmental variables to be included in such a stratification should be based on the relationship between IAP species and their physical environment to successfully summarize variance in their abundance within the different strata. A further objective is to obtain all possible combinations of environmental variables or a full rank design in the stratification to allow for the comparison of different strata based on actual field sampled data. This raises the question of which predictive environmental variables as well as how many to include in the stratification. For this purpose, three invasive tree species, namely Acacia cyclops, Acacia mearnsii and Prosopis glandulosa were selected as they cover the maximum possible area at the highest density with the least amount of geographic overlap. A total of 26 environmental variables that included climatic, soil and topographic type variables were tested with linear regressions against correlations with the abundance of those tree species. The results showed that a combination of average precipitation, soil depth, clay content in the B-horizon and terrain morphological units will serve as a suitable stratification at a national level to explain IAP abundance variation sufficiently well whilst retaining a full rank design. These results will be applied as the first phase in the formation of a regional level IAP monitoring programme for South Africa on a scientific basis.
Evaluating management regimes for European beech forests using dynamic programming
(Spanish National Institute for Agricultural and Food Research and Technology, 2014-06-06) Torres-Rojo, Juan Manuel; Vilcko, Frantisek; Von Gadow, Klaus
Aim of study: This contribution describes a systematic search method for identifying optimum thinning regimes for beech forests (Fagus sylvatica L.) by using a combination of optimization heuristics and a simple whole stand growth prediction model. Area of study: Data to build the model come from standard and management forest inventories as well as yield tables from the Northern and Western part of Germany and from southern and central Denmark. Material and methods: Growth projections are made from equations to project basal area and top height. The remaining stand variables are recovered from additional equations fitted from forest inventory data or acquired from other authors. Mortality is estimated through an algorithm based on the maximum density line. The optimization routine uses a two-state dynamic programming model. Thinning type is defined by the NG index, which describes the ratio of the proportion of removed trees and basal area with respect to the same proportion before thinning. Main results: Growth equations fitted from inventory data show high goodness of fit with R2 values larger than 0.85 and high significance levels for the parameter estimates. The mortality algorithm converges quickly providing mortality estimates within the expected range. Research highlights: The combination of a simple growth and yield model within a Dynamic Programming framework in conjunction with NG values as indicators of thinning type yield good estimates of practical thinning schedules compared to thinning recommendations provided by diverse authors.
Evaluation of Irvingia kernels extract as biobased wood adhesive
(SpringerOpen, 2020-02-22) Alawode, A. O; Eselem-Bungu, P. S; Amiandamhen, S. O; Meincken, M.; Tyhoda, L.
Irvingia tree species have been earmarked for domestication in many countries due to their potential as raw materials for various applications, which include biodiesel, cosmetics, perfume, soap, etc. Presently, there is no information on the utilization of kernel seed extract as a potential source of green wood adhesive. This study is focused on investigating the properties of adhesives produced from kernel seeds of two Irvingia wood species i.e. Irvingia gabonensis (IG) and Irvingia wombolu (IW), as well as investigating the improved properties derived from the effect of modification using a few selected modifying agents including glutaraldehyde, glyoxal, epichlorohydrin (EPI) and an acid/base type process modification. Polyethylene (PE) was used along with the glutaraldehyde, glyoxal and epichlorohydrin modifiers in the modification process. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were conducted to study the effect of modification on adhesive properties. The glycosidic carbon of the unmodified extracts and that of the EPI modified sample were not sensitive to chain conformations. Principal components (PC) 1 and 2 explained 85.19 and 9.54%, respectively, of the total variability in FTIR spectra among the modified and unmodified adhesives. The unmodified samples for IG and IW exhibited one peak with crystallization temperatures of 18.7 and 14.4 °C, respectively, indicating only one component exhibits some low degree crystallinity. The adhesive properties of the modified extracts were tested on wood veneers according to ASTM standard. The shear strength of the modified adhesives ranged from 1.5 to 3.93 MPa and 1.7 to 4.05 MPa for IG and IW, respectively. The modified samples containing PE showed marked improvement in the shear strength. The highest values were about 63% higher than the shear strength of unmodified samples with least shear strength. The results indicated that the modification of Irvingia-based adhesives had a great contribution to their performance as natural wood adhesives.
Facilitating the recovery of natural evergreen forests in South Africa via invader plant stands
(SpringerOpen, 2017) Geldenhuys, Coert J.; Atsame-Edda, Angeline; Mugure, Margaret W.
ENGLISH ABSTRACT: Contrary to general belief, planted and naturalized stands of introduced species facilitate the recovery of natural evergreen forests and their diversity. Forest rehabilitation actions are often performed at great cost: mature forest species are planted, while species with adaptations to recover effectively and quickly after severe disturbance are ignored; or stands are cleared of invasive alien species before native tree species are planted. By contrast, cost-effective commercial plantation forestry systems generally use fast-growing pioneer tree species introduced from other natural forest regions. Such planted tree stands often facilitate the recovery of shade-tolerant native forest species. This paper provides a brief overview of disturbance-recovery processes at landscape level, and how pioneer stands of both native and introduced tree species develop from monocultures to diverse mature forest communities. It uses one example of a study of how natural forest species from small forest patches of 3 ha in total invaded a 90-ha stand of the invasive Black wattle, Acacia mearnsii, over a distance of 3.1 ha at Swellendam near Cape Town, South Africa. The study recorded 329 forest species clusters across the wattle stand: more large clusters closer to and more smaller clusters further away from natural forest patches. The 28 recorded forest species (of potentially 40 species in the surrounding forest patches) included 79% tree and 21% shrub species. Colonizing forest species had mostly larger fleshy fruit and softer small seeds, and were dispersed by mostly birds and primate species. Maturing forest trees within developing clusters in the wattle stand became a source for forest regeneration away from the clusters, showing different expansion patterns. Four sets of fenced-unfenced plots in the wattle stand showed the impact of browsing by livestock, antelope, rodents and insects on the successful establishment of regenerating forest species, and the dramatic effect of excluding browsing. The results support the approach to rather selectively manipulate than clear invader plant stands in the natural forest environment. This approach invests in the natural succession process rather than planting. It protects developing seedlings against browsing by stacking invader plant debris around them, rather than protecting them by means of costly fencing. This forest recovery process through nurse stands of invasive species can be managed, with additional benefits: Indigenous tree species provide for better streambank stability; and the practice provides for local job creation over a 10-year period for harvesting poles and firewood from the manipulative conversion process.
Functional and phylogenetic diversity determine woody productivity in a temperate forest
(Wiley Open Access, 2018) Hao, MinHui; Zhang, Chunyu; Zhao, Xiuhai; Von Gadow, Klaus
ENGLISH ABSTRACT: Understanding the relationships between biodiversity and ecosystem productivity has become a central issue in ecology and conservation biology studies, particularly when these relationships are connected with global climate change and species extinction. However, which facets of biodiversity (i.e. taxonomic, functional, and phylogeneticdiversity) account most for variations in productivity are still not understood very well. This is especially true with regard to temperate forest ecosystems. In this study, we used a dataset from a stem- mapped permanent forest plot in northeastern China ex-ploring the relationships between biodiversity and productivity at different spatial scales (20 × 20 m; 40 × 40 m; and 60 × 60 m). The influence of specific environmental conditions (topographic conditions) and stand maturity (expressed by initial stand vol-ume and biomass) were taken into account using the multivariate approach known as structural equation models. The variable “Biodiversity” includes taxonomic (Shannon), functional (FDis), and phylogenetic diversity (PD). Biodiversity–productivity relation-ships varied with the spatial scales. At the scale of 20 × 20 m, PD and FDis significantly affected forest biomass productivity, while Shannon had only indirect effects. At the 40 × 40 m and 60 × 60 m scales, biodiversity and productivity were weakly correlated. The initial stand volume and biomass were the most important drivers of forest pro-ductivity. The local environmental conditions significantly influenced the stand vol-ume, biomass, biodiversity, and productivity. The results highlight the scale dependency of the relationships between forest biodiversity and productivity. The positive role of biodiversity in facilitating forest productivity was confirmed at the smaller scales. Our findings emphasize the fundamental role of environmental conditions in determining forest ecosystem performances. The results of this study provide a better understand-ing of the underlying ecological processes that influence specific forest biodiversity and productivity relationships.

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