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Impact of season, stem diameter and intensity of debarking on survival and bark re-growth pattern of medicinal tree species, Benin, West Africa

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Abstract

Bark is a greatly coveted non-timber forest product (NTFP). Its overexploitation from medicinal tree species threatens an essential source of medication for rural populations. Despite the relevance of bark, not much information is available on the ecological impact of bark harvesting. In Benin, West Africa, we investigated how various harvesting techniques affect the bark re-growth of 12 tree species and the survival of debarked trees. Trees were debarked following a combination of three factors: (i) season of bark harvesting (dry or rainy season), (ii) size class of the tree (three stem diameter classes) and (iii) intensity of debarking (seven different percentages of trunk circumference debarked). Measurements of edge growth and survival were taken every 6 months during 2 years. Ring-barking (100% of trunk circumference debarked) did not allow the sustainable exploitation of any species, while all trees with 75% of debarked circumference remained alive and produced edge growth. Whatever the bark harvesting technique, 5 out of the 12 species had a bark recovery rate below 1 cm/year, rendering the wound closure very unlikely. On the other hand, five species showed good to very good bark recovery rates (>7 cm/year) and for these species the combination of debarking factors (season, dbh and intensity) allowing the highest edge growth was determined. This experimental bark stripping revealed the complexities involved in decision-making for sustainable tree management. Studying the patterns of bark recovery rates provides a relevant tool to assess for each species the delay for achieving closure of a specific wound area.

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... Among the many methods that are used to remove bark of these plants, we highlight the direct methods, in which extractors collect the bark of living parts of individuals, more precisely from the trunks (Filizola and Sampaio 2015). In order to perform a sustainable harvesting of this resource, not only the collection method must be evidenced, it is also necessary to determine a maximum limit to be removed (Delvaux et al. 2010). Cunningham and Mbenkum (1993), studying Prunus africana (Hook. ...
... were selected. These individuals had to be within the minimum criterion for inclusion of diameter, greater than or equal to 30 cm at 1.3 m height, which is the minimum viable measure for regeneration studies (see Delvaux et al. 2010). Individuals were monitored from June 2013 to May 2015 (24 months), assessing the time of regeneration of bark under the influence of collection intensity and rainfall. ...
... To set up the experiment, the bark and inner bark of the individuals, that comprise the rhytidome and the secondary phloem, were removed. After collection of the bark, it has been drawn fixed points on both sides of the scar, in a horizontal direction, from which measurements of the regenerated barks were monthly taken (Delvaux et al. 2010). To obtain complete regeneration, the average value of the three measurements taken from both sides of the scar were calculated. ...
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The growing commercial demand for products with medicinal use has caused overexploitation of several plant species worldwide. To prevent the decline of these populations, the collection of these resources should be done in a sustainable way considering the time of its replacement in natural stocks. This study was designed to identify the relationship between different intensities of extraction of bark from the trunk of Stryphnodendron rotundifolium Mart. and its regeneration speed. For this, we selected two areas of Cerrado in the Northeast of Brazil, where a monitoring experiment with duration of 24 months was performed. This experiment consisted in simulating different extractive damage to assess the regeneration of bark. In each area, we selected 20 individuals, among which four treatments with five repetitions were implemented. The data showed that in both study areas, the trees regenerated their shells faster when subjected to higher collection intensities. However, this regeneration was not related to variations in rainfall in the environment.
... Similarly in Africa, and important for understanding bark production and allied post-harvesting resilience, few studies have assessed bark regeneration following wounding (anthropogenic or herbivory), and the rates thereof (Twine, 2008;Delvaux et al., 2009Delvaux et al., , 2010Cunningham, 2014;Wigley et al., 2019), and corresponding tree growth data are usually not available (Ngubeni, 2015). Studies that have been conducted are often short-term and/or not sample or species rich. ...
... Studies that have been conducted are often short-term and/or not sample or species rich. However, research by Delvaux et al. (2009Delvaux et al. ( , 2010 on bark recovery over two years for 925 trees from 12 species in Benin is some of the most comprehensive for the continent. And, Twine's (2008) unpublished thesis evaluating the ecological sustainability of bark harvesting in savanna woodlands in South Africa offered rare insights into wound recovery and regeneration ecology, but unusually in conjunction with factors that included inferred relative growth rates. ...
... And, Twine's (2008) unpublished thesis evaluating the ecological sustainability of bark harvesting in savanna woodlands in South Africa offered rare insights into wound recovery and regeneration ecology, but unusually in conjunction with factors that included inferred relative growth rates. Since tree growth and wound occlusion (wound closure through bark regrowth) rates are likely to be positively correlated, wounds in faster growing and/or younger trees are thus more likely to occlude quicker, depending on the species (Neeley, 1988;Twine, 2008;Delvaux et al., 2010;Ngubeni, 2015). ...
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Sustainable management strategies for trees are informed by research on growth rates and regeneration. In a 1998 study of bark thickness and tree size, six species (all used for traditional medicine) were sampled by removing 5 cm-diameter bark disks at four height intervals on 210 stems at 15 sites in South Africa. An impromptu revisit to one site in 2003 revealed that wounds for one species exhibited very little wound occlusion. These observations prompted a 2004 study on wound occlusion and stem growth for five of the species at six sites (Albizia adianthifolia, Balanites maughamii, Elaeodendron transvaalense, Searsia chirindensis, Warburgia salutaris), where 84 stems were re-measured. There were species-specific stem growth and wound occlusion rates. In general, annual lateral stem growth at 1.3 m was inversely related to stem size (corroborated by lateral widening responses of the original wound edges). There was also a tendency for smaller and/or faster growing stems to exhibit more wound occlusion and faster rates of bark regrowth – except in W. salutaris, where smaller individuals exhibited comparatively lower rates of occlusion compared to bigger individuals. All wound occlusion was by bark edge growth (typically <3 mm y⁻¹); only A. adianthifolia showed complete wound closure, whereas B. maughamii showed the least (17%±19%). An inverse relationship existed between density (timber and bark) and stem growth, wound occlusion and lateral widening of the old scar edges – except for S. chirindensis. Hence trees with softer wood and bark generally grew quicker and exhibited more wound occlusion than trees with harder wood and bark.
... Depending on the harvesting intensity, bark harvesting can be injurious and dangerous to the survival of trees, because a simple debarking can easily disrupt the physiological functioning of a tree (Geldenhuys, 2004;Vermeulen, 2006) and may lead to progressive or instant death. This is particularly important given that bark regrowth, either edge or sheet growth following harvesting, is species-specific (Delvaux, 2009;Delvaux et al., 2010). ...
... The ability of trees to recover from debarking varies among species (Delvaux, 2009;Delvaux et al., 2010). For instance, in a dry forest in Benin, West Africa, only two species, Khaya senegalensis and Lannea kerstingii, out of 12 species were reported to recover completely by edge regrowth whereas only one species, Maranthes polyandra, showed good sheet regrowth two years following total bark harvesting (Delvaux, 2009). ...
... This produces tyloses in the vessel's lumen and accumulation of phenolic substances in the parenchyma to cover the debarked area (Haines et al., 2018). This protective mechanism may enhance the survival of trees at least for the first six months even after high-intensity debarking (Delvaux et al., 2010). ...
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Unregulated harvest of tree bark for medicinal purposes has led to overexploitation and extinction of some valuable tree species. The study assessed bark recovery rates of four medicinal tree species and determined their regenerative abilities, stress shoot production and susceptibility to wood borers. A total of 192 trees of Bombax buonopozense, Mangifera indica, Azadirachta indica and Blighia sapida were randomly selected outside protected forests in the Moist Semi-deciduous (MSD) and Guinea Savannah (GS) ecological zones of Ghana. The trees were harvested using three harvesting intensities, 25%, 50%, and 75% bark removal. Edge and sheet re-growth, stress shoot production and wood borer attack were recorded for each tree in twelfth months. Our results show that the bark of B. buonopozense (29.4% at MSD and 21.4% at GS), M. indica (22.3% at MSD and 16.1% at GS) and A. indica (13.5% at MSD and 12.8% at GS) showed higher regeneration percentage compared to B. sapida (3.8% at MSD and 3.7% at GS), while stress shoot growth percentage was limited to only B. buonopozense (4.7% at MSD and 25% at GS). Though no tree died during the study period, borer attack was recorded for all the species except A. indica. We recommend that forest managers should allow minimum harvesting of B. sapida as they showed slow recovery, while rotation period for repeated harvest can also be prescribed for B. buonopozense and M. indica. Moreover, the coppicing ability of B. buonopozense needs to be examined since it produced a higher number of stress shoots.
... In species harvested for bark, the definition of a maximum sustainable harvesting limit for the bark is necessary to ensure the persistence of individuals and populations (Delvaux et al. 2010). Overall, it is important to consider the response of bark regeneration not only under several intensities of debarking but also in different environments. ...
... In Myracrodruon urundeuva (Anacardiaceae), a medicinal species whose bark is exploited in the Brazilian dry forest (Caatinga), no significant correlation was found between the monthly percent regeneration and the average monthly precipitation (Monteiro et al. 2011). However, Delvaux et al. (2010), assessing the bark regrowth patterns of 12 species in Benin, found that the rate of regeneration was higher during the spring. Other species in which bark recovery is influenced by the season are Terminalia arjuna (Combretaceae) and Litsea glutinosa (Lauraceae), a highly exploited Indian medicinal tree (Pandey and Mandal 2012). ...
... The absence of differences among groups with different percentages of debarking and the lack of signs of morbidity in the trees with approximately 100 % removal of the bark represents a contrast with the results of several previous studies on bark harvesting. In many species studied to date, overexploited individuals died shortly following the exploitation, most likely due to the disruption of water and/or nutrient flows (Cunningham and Mbenkum 1993;Borges Filho and Felfili 2003;Geldenhuys et al. 2007;Guedje et al. 2003Guedje et al. , 2007Delvaux et al. 2010). ...
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Bark and exudates are widely commercialized non-timber forest products. However, the ecological impacts of the harvesting of these products have seldom been studied. The aim of this study is to investigate the relationship of tree resilience to harvesting intensity in Himatanthus drasticus, a tree that is highly exploited in the Brazilian savanna (Cerrado) for its medicinal latex. Although the traded product is the latex, the traditional harvesting systems involve the removal of the bark of the trees to allow exploitation. A 3-year experiment was conducted in two different Cerrado ecosystems (open savanna and savanna woodland). Trees were debarked at four debarking intensities to simulate the effects of traditional management systems. Measurements of bark growth were taken every 6 months, and quantitative and qualitative indexes of bark regeneration were obtained. The mortality of the debarked trees was low and could not be related to the intensity of harvesting. No signs of attack by fungi or insects were recorded. Compared with other species exploited for bark, H. drasticus is very resilient to harvesting; however, bark regeneration is relatively slow. In both analyzed ecosystems, the regeneration indexes showed higher values in the controls than in the treatments, indicating that 3 years is not sufficient for total recovery of the rhytidome. Bark regeneration occurred primarily by sheet growth and was more rapid in open savanna than in savanna woodland. No differences in the rate of bark recovery were found among management treatments. Based on the results, sustainable harvesting guidelines are suggested for the species.
... Bark removal alone, however, can also seriously affect tree populations. In Benin, K. senegalensis individuals with a diameter at breast height (dbh) > 30 cm were said to be scarce, even in protected areas (Delvaux et al., 2010). This is a remarkable contrast, as saplings of this species are considered as locally abundant with ca. ...
... pollinator is missing), competitive exclusion by other species, inaccessibility due to geographical or (a)biotic barriers, or overharvesting by humans (Araújo and Peterson, 2012). To find out whether the commercial collection of wood, roots or seeds is a destructive activity, field studies on species' abundances, and the impact of different extraction methods on the survival, growth and reproduction of the harvested individuals remain essential (Delvaux et al., 2010;Gaoue and Ticktin, 2007b). Bark harvesting, for example, may be sustainable as long as trees are not ring-barked or felled and species are able to recover quickly. ...
... Previously untouched individuals of K. senegalensis in Bénin showed very good bark recovery rates and complete wound closing after 24 months (Delvaux and Sinsin, 2009). Because of its resilience to debarking and its fast growth in open areas, K. senegalensis is said to have the potential to support sustainable bark harvesting (Delvaux et al., 2010). However, this tree is frequently harvested simultaneously for its bark and leaves by local herders to feed their livestock, which negatively affects seedling and sapling densities (Gaoue and Ticktin, 2007a). ...
... Bark harvest can have a high negative impact as it alters the structure and physiological continuity of adult woody plants, thus threatening their survival [2][3][4]. Because medicinal barks are some of the most traded NTFPs, there is a need to determine their maximum sustainable harvest rates as key elements for their long-term management and conservation for these species [5][6][7]. ...
... Post-harvest bark regeneration varies across species and is affected by a range of factors, including [5,6,13,14]: the amount of bark harvested, incision depth, harvest season, plant physiology, microclimate and exudate presence [15][16][17]. However, how bark regeneration is affected by these factors varies between species and ecosystems, thus broad recmmendations for sustaining bark harvests are not possible. ...
... For example, for 12 tree species of a tropical forest of Benin, West Africa, low debarking intensity (without damage in the vascular cambium) increased bark regeneration rates and survival, reducing the mortality caused by predatory insects [5]. In a follow-up study, the mortality of those 12 tree species increased with 100% debarking in the wet season, whereas bark regeneration rate was associated with larger tree diameter and bark harvest intensities during wet season [6]. In contrast, in the Caatinga forests of Brazil, bark regeneration rates of Myracrodruon urundeuva Allemão [13] and Stryphnodendron rotundifolium Mart. ...
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Commercial harvests can threaten tree species harvested for their bark. Amphipterygium adstringens is a dioecious tree, endemic to the tropical dry forests of Mexico, where it is intensively harvested for its medicinal bark. Limited information hinders developing sustainable management strategies for A. adstringens. We assessed bark regeneration for male and female trees, and evaluated the effect of tree sex and diameter, debarking treatments and cutting seasons on bark regeneration and tree survival rates. Bark regeneration was higher for wet season harvested trees (vs. dry), regardless of their sex. Bark regeneration was higher on female than on male trees. There were significant interactions of harvest season, harvest treatment and tree sex diameter on bark regeneration and survival. Overall, the highest bark regeneration rates occurred in female trees with ≥20.1 cm diameter that were wet season harvested with a 50% debarking intensity. Consequently, wet season and intermediate intensity harvests appear to foster sound management, but we recommend against targeting exclusively a single demographic group (i.e., large female trees) due to potential negative impacts on species demography and bark supply. A grounded strategy for sustaining bark harvest would also need to take into account relevant aspects of local socio-ecological context, including harvest interactions with other land uses.
... Although both products could be available at all seasons, previous studies on Prunus africana and Parkia biglobosa exploitation showed that bark peeling was easier in the rainy season and bark harvesting during the In the column, means with same letter(s) are not significantly different at base on the probability level presented. dry season, resulted in susceptibility to pests and diseases and poor regrowth (Nkeng et al., 2009;Delvaux et al., 2010). The selection criteria for exploitable trees mainly depend on the bark thickness and size of the tree. ...
... Usually, big size trees (with Diameter at Breast Height (DBH) greater than 30 cm) are preferred due to high yield, bark thickness and concentration of active ingredient. Previous studies had shown that the bark thickness and yield are positively correlated to tree Diameter at breast height Delvaux et al., 2010). Moreover, these bigger diameter trees show little damages and better recovery capacity after exploitation than those at younger stages (Nkeng et al., 2009;Delvaux et al., 2010;Kamatenesi et al., 2014;Guedje et al., 2016). ...
... Previous studies had shown that the bark thickness and yield are positively correlated to tree Diameter at breast height Delvaux et al., 2010). Moreover, these bigger diameter trees show little damages and better recovery capacity after exploitation than those at younger stages (Nkeng et al., 2009;Delvaux et al., 2010;Kamatenesi et al., 2014;Guedje et al., 2016). ...
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A study was conducted in the western highland region of Cameroon with the aim to assess sustainability of Gnidia glauca exploitation in its natural habitat. In 33 plots of 40x40m, the unexploited, exploited and dead trees were evaluated or vitality using amulti-criteria vulnerability assessment method. An ethnobotanical survey was conducted with 60 respondents in six villages around Mount Oku area. Data were submitted to ANOVA and means separated using Duncan test. The results revealed that 95 % of G. glauca trees were unexploited and only 3.92% showed signs of exploitation, among which 1.08% were dead. Among the exploited stems, 18% showed a completely dead crown, whereas 73% were described to be regular and healthy. Wood (29%) and bark (28%)were the main products being exploited. However, the species’ bark was the most frequently harvested product (64%). G glauca was shown to be more vulnerable in forests (2.6) than in savanna (2.4). The motivating factors for the species’ domestication were the fragility of its habitat, the potential high future demand for its products and the unsustainable exploitation techniques being applied. It is therefore recommended to promote the species uses, conservation and cultivation within its national distribution range for local livelihood improvement.
... Botha et al. (2004) compared the status of populations in protected and nonprotected areas in Mpumalanga, South Africa. Mirroring the situation with many tree species that are subjected to high demand for bark, ring-barking (peeling of a bark strip embracing the whole stem circumference [Delvaux et al. 2010]) is common among W. salutaris populations. Recently, Dludlu et al. (2017) surveyed the status of populations throughout Swaziland, reporting widespread ring-barking, even in protected areas, but they also discovered several hitherto unknown populations. ...
... This is because ring-barking results in removal of all the cambium, impeding the regrowth of living tissue around the wound that results in bark regeneration. With the removal of the inner bark, transportation of photosynthates from the leaves to the roots is blocked, ultimately causing plant death (Delvaux et al. 2010). Appropriate harvesting techniques can limit damage to the inner bark, allowing for bark regeneration (Pandey 2015;Stewart 2009). ...
... Appropriate harvesting techniques can limit damage to the inner bark, allowing for bark regeneration (Pandey 2015;Stewart 2009). For example, regeneration of six medicinal tree species in India was improved if the inner bark was not harvested (Pandey 2015), as was the case with 12 species in Benin (Delvaux et al. 2010). This is because shallow damage to the bark is unlikely to affect the cambium (Baldauf et al. 2014;Romero 2014), and thus, still allows the flow of sugars from the leaves to the roots. ...
Article
Uses, Knowledge, and Management of the Threatened Pepper-Bark Tree (Warburgia salutaris) in Southern Mozambique.Warburgia salutaris, the pepper-bark tree, is one of the most highly valued medicinal plant species in southern Africa. Due to its popularity in folk medicine, it is overexploited in many regions and is deemed threatened throughout its range. We identified cultural and social drivers of use, compared knowledge distribution, determined management practices, and explored local ecological knowledge related to the species in the Lebombo Mountains, Tembe River, and Futi Corridor areas in southern Mozambique. Stratified random, semistructured interviews were conducted (182), complemented by 17 focus group discussions in the three study areas. W. salutaris was used medicinally to treat 12 health concerns, with the bark being the most commonly used part. Knowledge of the species varied between the three areas, but not with respondent gender or age. Harvesting was mostly through vertical bark stripping (71% of informants). To promote sustainable use of the species, we suggest multiple conservation approaches, including the use of alternative species with the same application, substitution of bark by leaves, and increases in alternative sources of plant material through cultivation. Additional information on species demography, harvest impact, and post-harvest bark recovery rate area is required. Information obtained in this work can contribute to management guidelines and plans for the species in Mozambique.
... Similar harvesting periods were reported in Mali (Dhillion and Gustad 2004). The fact that the bark is harvested at any time of the year and not only during the rainy season is a cause of concern as bark regeneration depends in general on humidity as the moisture content of the exposed wound is the most important factor allowing the start of the bark recovery process (Delvaux et al. 2010). Poor bark regeneration leads to poor quality fibers, leading to debarking from other parts of the baobab tree, causing an increase in the level of injury to the tree (Dovie 2003;). ...
... This avoids infections and other adverse effects on the physiology of the tree. CUC (2010) declared that the best period to harvest the bark is at the end of the rainy season as the moisture content of the exposed wound is the most important factor allowing the start of the bark recovery process (Delvaux et al. 2010). Furthermore, some baobab seedlings and saplings should be spared and protected by local people on croplands in order to promote successful recruiting of the baobab in the future. ...
Article
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Many cash-poor households in the semi-arid tropics strongly depend on non-timber forest products (NTFPs) for livelihood. Increasing threats on NTFP-providing tree species, due to land-use intensi-fication, require ecological studies as well as additional information about species' uses and management provided by local people. The objectives of our study were to (i) document uses and management of the baobab (Adansonia digitata L.), (ii) investigate knowl-edge distribution among genders and different villages, and (iii) assess the population status of the baobab in eastern Burkina Faso. We conducted an ethnobotanical survey among Gulimanceba people and performed a quantitative analysis using different measures of knowledge. Interviews reveal that the baobab is harvested by local people for 25 use-types. The fruits are the most important plant part and baobab products are of special importance for nutritional uses. Local management of baobab seems to be so far sufficient to maintain baobab populations. The fact that we found some differences in uses and management of baobab between genders and villages emphasizes the impor-tance of gender-and region-related management recommendation. People are able to use and manage the baobab in a relative sustainable way as human population density is relatively low and as they have relatively good access to the forest compared to other regions of Burkina Faso. However, in the light of land-use and climate changes, adapted management strat-egies are required. We conclude that ethnobotanical studies on a small-scale level are of high importance in order to develop management strategies that are reliable in a specific region.
... Além disso, nem sempre a sustentabilidade econômica assegura a sustentabilidade ecológica e vice-versa (Homma 1993). Dependendo da frequência, intensidade ou parte da planta coletada, bem como das perturbações causadas ao ambiente, o extrativismo de PFNM pode alterar, em diferentes níveis, os processos biológicos da espécie explorada (Hall & Bawa 1993, Ticktin 2004, afetando as taxas vitais dos indivíduos (Guedje et al. 2007, Ghimire et al. 2008, Schumann et al. 2010) e comprometendo os parâmetros demográficos (Dhillion & Gustad 2004, Guedje et al. 2007Rist et al. 2010, Delvaux et al. 2010) e genéticos das populações (Shaanker et al. 2004, Ticktin 2004. ...
... O conhecimento do comportamento demográfico da população é uma excelente ferramenta para a elaboração de técnicas que visem à conservação e o uso sustentável dos recursos naturais (Hall & Bawa 1993, Ticktin 2004, Escalante et al. 2004 Padoch 1992), a coleta desses produtos, dependendo da intensidade, frequência e parte da planta coletada, pode alterar em diferentes níveis os processos ecológicos da espécie alvo (Hall & Bawa 1993, Ticktin 2004, Varghese & Ticktin 2008, Delvaux et al. 2010. ...
... Stem bark wound is a direct biomass removal of an important plant tissue that induces shift in internal resource allocation patterns and often leads to a decrease in tree growth (Bazzaz et al. 1987), even if compensatory growth may sometimes occur when bark removal is not recurrent (Gaoue et al. 2011). However, the wounded organ can recover through several internal mechanisms (Ryan and Yoder 1997) depending on the debarking intensity and the intrinsic recover ability of the species (Gaoue and Ticktin 2007;Delvaux et al. 2010). ...
... Similar results have been found in Khaya senegalensis, where the tree can quickly recover from partial debarking (Gaoue and Ticktin 2007) while the 100 % ringbarked trees will die (Delvaux et al. 2009) suggesting that the intensity of bark removed affects plant responses to debarking. Afzelia africana is one of the tropical species that exhibited the highest ecological resilience to debarking under stressful arid and semi-arid climate in Benin (Delvaux et al. 2010), and this may explain its wide distribution across disturbance and climate gradient in Benin (Orwa et al. 2009;Mensah et al. 2014). The lack of clear and significant effect of debarking on tree growth may suggest that current bark harvesting intensities might be sustainable (N'Dri 2012; Amahowe et al. 2017). ...
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Understanding how trees mediate the effects of chronic anthropogenic disturbance is fundamental to developing forest sustainable management strategies. The role that intraspecific functional diversity plays in such process is poorly understood. Several tree species are repeatedly defoliated at large scale by cattle breeders in Africa to feed livestock. In addition, these tree species are also debarked for medicinal purposes. These human-induced disturbances lead to biomass loss and subsequent decline in the tree growth. The main objective of this work is to investigate how functional traits mediate tree response to chronic anthropogenic disturbance. We used a unique dataset of functional traits and growth rate of 503 individual tree of Afzelia africana. We collected data on leaf mass per area (LMA), wood density (WD) and growth rate, and recorded history of human disturbances (debarking, pruning) on individual tree from 12 populations of Afzelia africana distributed in two ecological zones in Benin (West Africa). We tested the effect of disturbances on absolute growth rate across ontogenetic stages, assessed the role of intraspecific trait variability on growth and tested the role of tree functional strategy on the tree growth response to debarking and pruning. We found that debarking did not affect stem growth, suggesting a fast compensatory re-growth of bark wounded. Moreover, tree response to debarking was independent of the functional strategy. By contrast, we found that pruning reduced tree absolute growth, however, trees with low WD were more strongly affected by pruning than trees with high WD. Our results emphasize the importance for plant functioning of the interplay between the availability of leaves for resource acquisition and a resilience strategy by mobilizing stored resources in stem wood to be reinvested for growth under severe disturbances.
... Tree bark provides protection against desiccation, fire, insects and diseases, and plays a key role in the transportation of nutrients from leaves to roots through the phloem tissues, thus bark harvesting may induce internal tree stress and increase vulnerability to external agents [6– 10]. In fact, bark extraction has been reported to alter tree survival, growth and reproduction in a range of species worldwide456710]. However, little is known about the impacts of bark harvesting on tree vulnerability to fire, which is especially relevant in the light of current changes in climate and fire regimes. ...
... size [32,33], fire behaviour26272829303132 and environmental conditions (e.g. precipitation, season) that influence tree vigour and phenology [7,9]. Specifically, the aims of this paper are: ...
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Forest ecosystems where periodical tree bark harvesting is a major economic activity may be particularly vulnerable to disturbances such as fire, since debarking usually reduces tree vigour and protection against external agents. In this paper we asked how cork oak Quercus suber trees respond after wildfires and, in particular, how bark harvesting affects post-fire tree survival and resprouting. We gathered data from 22 wildfires (4585 trees) that occurred in three southern European countries (Portugal, Spain and France), covering a wide range of conditions characteristic of Q. suber ecosystems. Post-fire tree responses (tree mortality, stem mortality and crown resprouting) were examined in relation to management and ecological factors using generalized linear mixed-effects models. Results showed that bark thickness and bark harvesting are major factors affecting resistance of Q. suber to fire. Fire vulnerability was higher for trees with thin bark (young or recently debarked individuals) and decreased with increasing bark thickness until cork was 3-4 cm thick. This bark thickness corresponds to the moment when exploited trees are debarked again, meaning that exploited trees are vulnerable to fire during a longer period. Exploited trees were also more likely to be top-killed than unexploited trees, even for the same bark thickness. Additionally, vulnerability to fire increased with burn severity and with tree diameter, and was higher in trees burned in early summer or located in drier south-facing aspects. We provided tree response models useful to help estimating the impact of fire and to support management decisions. The results suggested that an appropriate management of surface fuels and changes in the bark harvesting regime (e.g. debarking coexisting trees in different years or increasing the harvesting cycle) would decrease vulnerability to fire and contribute to the conservation of cork oak ecosystems.
... Cette flore sert de nourriture, de produits sanitaires, de matériels de construction, d'outils domestiques, de sources d'énergie et contribue à diversifier les sources de revenus [3]. Cependant, malgré l'importance des formations végétales, elles sont menacées par des attaques catastrophiques dues aux variations climatiques et aux activités anthropiques [4]. Au cours de la période 1990 à 2005, une estimation moyenne donne un taux de déforestation de 20,7 % pour l'Afrique de l'Ouest, avec une légère augmentation pour la Côte d'Ivoire [5]. ...
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La présente étude dont l'objectif est d'évaluer l'intérêt de la zone de conservation de biodiversité du barrage hydroélectrique de Soubré pour les populations riveraines a été conduite dans une perspective d'élaboration d'un plan de gestion durable. De façon spécifique, il s'agit d'identifier les espèces utilitaires présentes et d'évaluer leur disponibilité. La méthodologie de collecte de données a combiné des inventaires botaniques et une enquête ethnobotanique. Les résultats montrent que la flore est riche de 346 espèces. Parmi ces espèces, 84 sont citées par les populations comme plantes utilitaires. Les catégories d'usage sont, par ordre d'importance, l'usage médicinal, l'usage alimentaire, l'artisanat, le bois d'oeuvre et service. Les organes recherchés sont principalement les feuilles dans la pratique de la médecine traditionnelle, les fruits en alimentation et la tige en artisanat, bois d'oeuvre et service et bois énergie. Sur l'ensemble des espèces utilitaires, 13 sont d'une importance capitale pour les populations. Parmi celles-ci, 6 sont moins abondantes dans la zone. C'est le cas notamment de Ricinodendron heudelotii, Carpolobia lutea G. Don. Ces résultats permettraient d'accorder une place importante aux espèces utilitaires et surtout celles à haute valeur d'importance dans la suite de l'aménagement de la zone afin de contribuer durablement au bien-être des populations. Abstract Availability of useful plants in the biodiversity conservation area of the Soubré hydroelectric dam, South West, Côte d´Ivoire The present study, whose objective is to assess the interest of the biodiversity conservation area of the Soubré hydroelectric dam for local residents, was carried out with a view to developing a sustainable management plan. More specifically, it involves identifying the useful species present and assessing their availability. The data collection methodology combined botanical inventories and an ethnobotanical survey. The results show that the flora is rich in 346 species. Among these species, 84 are cited by populations as useful plants. The categories of use are, in order of importance, medicinal use, food use, crafts, lumber and 66 Afrique SCIENCE 16(6) (2020) 65-74 Yao Jean-Clovis KOUADIO et al. services. The organs sought are mainly the leaves in the practice of traditional medicine, the fruits in food and the stalk in crafts, wood and services and wood energy. Among all the useful species, 13 are of paramount importance for populations. In these, 6 are less abundant in the region. This is particularly the case for Ricinodendron heudelotii, Carpolobia lutea G. Don. These results would make it possible to give an important place to useful species and especially those with high value of importance in the further development of the area in order to contribute sustainably to the well-being of the populations.
... These results indicate that these four species have different levels of resistance to deer browsing, with the highest being shown by A. carpinifolium. Similar findings were obtained in several previous studies based on simulated experiments of browsing and debarking (Noel 1970;Bergström and Danell 1987;Delvaux et al. 2010). The high resistance of A. carpinifolium is considered to be due to its high rates of adventitious bud production and regrowth of bark, including the cambium layer and phloem, after browsing and debarking. ...
Book
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This open access book presents and analyzes the results of more than 30 years of long-term ecological research in riparian forest ecosystems with the aim of casting light on changes in the dynamics of riparian forests over time. The research, focusing on the Ooyamazawa riparian forest, one of the remaining old-growth forests in Japan, has yielded a number of interesting outcomes. First, it shows that large-scale disturbances afford various trees opportunities for regeneration and are thus the driving force for the coexistence of canopy trees in riparian forests. Second, it identifies changes in reproductive patterns, highlighting that seed production has in fact quantitatively increased over the past two decades. Third, it describes the decline in forest floor vegetation caused by deer grazing and reveals how this decline has affected bird and insect populations. The book illustrates the interconnectedness of phenomena within an ecosystem and the resultant potential for cascade effects and also stresses the need for long-term ecological studies of climate change impacts on forests. It will be of interest to both professionals and academics in the field of forest science.
... The authors have conjectured that wound closure is hastened through hormonal activity stimulated by stress in order to restore water conductivity. Working with ten different medicinal tree species, Delvaux et al. (2010) have concluded that species that were able to rapidly produce vessels with original density and size (similar to before wounding) show better tangential re-growth. In another study, Delvaux et al. (2013) have also shown that that the "width of the phloem tissue" is the key factor in the rapid wound recovery and shown that the presence of sclereids within the conducting phloem zone was negatively correlated with the bark recovery rate. ...
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Though Cinnamomum zeylanicum is a very important commercial aromatic bark yielding and oldest known tree spice of India, there are hardly any studies to understand the nature of wound healing and bark recovery. Further, optimal number of sprouts to be retained under coppice system to maximize the bark yield per tree in C. zeylanicum is not yet standardized. The present investigation was carried out to understand the influence of patch geometry and application of post-bark-extraction-protection treatments on bark regeneration in mature trees as well as to standardize an optimal number of sprouts to be retained under coppice system to maximize the bark yield per tree. In general, wound healing in C. zeylanicum occurred from the edge of the blaze and was quicker in the narrower patch than the broader patch; application of Bordeaux paste or neem seed kernel extract on the blazed area immediately after the bark extraction, resulted in significantly higher mean percent bark recovery and higher bark oil content than control. Allowing seven coppice sprouts per stem resulted in higher dry mass of bark per plant and higher bark oil than other treatments under coppice system. The results of the study would enable formulation of management strategies specifically for sustainable bark harvesting in Cinnamomum species.
... This has important implications for the population of A. leiocarpa because the impact of harvesting on populations depends on which size class is mostly harvested (Ticktin, 2004). In regard to debarking, Delvaux et al. (2010) found for 12 savanna species that the bark recovery rate after bark harvesting is size-dependent. Thus, bark recovery after debarking should be investigated for the different size classes of A. leiocarpa to evaluate the sustainability of this debarking pattern. ...
Article
Non-timber forest products (NTFPs) strongly contribute to livelihood security in the semi-arid tropics. Main factors determining the populations of NTFP-providing species are human activities. This study examined the impact of land-use, combined with rates and patterns of debarking and chopping on a NTFP-providing tree (Anogeissus leiocarpa) in Burkina Faso. We compared stands in a protected area (W National Park) with those of its surrounding communal area (fallows, croplands) in order to (i) obtain an indication on the status of the population, (ii) assess its harvesting tolerance, (iii) estimate the sustain-ability of present management, and (iv) derive which additional management strategies may foster its conservation. Our results reveal that the stands of A. leiocarpa are in healthy states in fallows and in the park. In croplands, the absence of saplings gives evidence of a declining population. Nearly all indi-viduals of A. leiocarpa were harvested in croplands and fallows, while the number of harvested individ-uals in the park was negligible. Intensity of debarking and chopping was tree size-specific. The sprouting ability significantly increased with higher chopping intensity. We conclude that despite the land-use impact and the intense harvesting, stands of A. leiocarpa are still well preserved due to the species life history (fast growing and high sprouting) and due to indirect positive influences of human activities by providing better environmental conditions for its recruitment. Thus, the population of A. leiocarpa is not at risk to over-harvesting and land-use even though it is not protected.
... The results revealed that bark regeneration was faster in younger and middle aged trees which corroborates with the findings of Delvaux, Sinsin, and Van Damme (2010) in which they reported that trees of Pseudocedrela kotschyi had similar responses to bark harvesting-i.e., medium sized trees (21-30 cm diameter at breast height [DBH]) had a faster bark recovery than the other studied DBH classes. ...
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Terminalia arjuna (“Arjuna”) in the family Combretaceae is a well-known medicinal tree whose bark is extensively used in Ayurvedic medicine, particularly as cardiac tonic. Demand for Arjuna bark, both in India and abroad has been growing rapidly for over a decade. Litsea glutinosa (“Maida”) in the family Lauraceae is a medium size tree. Its bark is used to treat joint pain, fracture, sprain, arthritis, back pain and indigestion. Presently the bark of Arjuna and Maida is being extracted through unscientific and destructive harvesting practices. This is the first study on development of sustainable harvesting practices of Arjuna and Maida bark. The stages of bark recovery varied from tree to tree. Age of tree, harvesting method and season of harvest influenced bark regeneration. This study recommends that for sustainable harvest, mature bark from only ¼ to ⅓ of the total girth of the tree should be stripped by removing only outer and middle bark, leaving the inner bark for regeneration. However, strip harvesting was found to be the best method in younger trees having GBH less than 60 cm. Sustainable bark harvesting can be done after every two years for Arjuna and one year for Maida by removing opposite quarters of trunk bark.
... A review of important fruit species for the local economy and diet, regularly consumed in the region surrounding Iquitos, Peru (Vasquez and Gentry, 1989), revealed that out of 193 fruit species used, 120 were exclusively wild‐harvested and 19 additional species originated from both wild and cultivated sources. However, the availability of several of the most popular fruit species had decreased markedly and destructive harvesting techniques and increasing market pressures were rapidly depleting wild populations (Sundriyal and Sundriyal, 2004; Delvaux et al., 2010). This highlights the need to take measures to manage the threat of overexploitation in any attempt to extract forest food products. ...
... The distance from the road was measured using a measuring tape for distances less than 10 meters and GPS for distances of more than 10 meters. Tree height and tree diameter were measured using a haga meter and diameter tape, respectively [19]. ...
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Trees in an urban environment play an important role. Studies have shown that the presence of trees can improve human physical and mental health. People in Kupang, Nusa Tenggara Timur Province, Indonesia, harvest Sterculia quadrifida R.Br. (faloak) bark for medicinal decoction for hepatitis and energy booster. Hepatitis cases in Kupang City continue to increase, from 40 cases in 2016 to 147 cases in 2017 and 220 cases in 2018. This study aimed to assess S. quadrifida bark harvesting intensity and its utilization in Kupang City. This study was conducted in five sub-districts in Kupang, namely Alak, Kelapa Lima, Kota Raja, Maulafa, and Oebobo. In each district, 20 faloak trees were selected to be observed. Parameters observed included: diameter, height, trees that were recently debarked and have recovered bark, distance from the road, and the presence of seedlings around the tree. The data were tabulated and analyzed descriptively. There were 98 trees observed because, in Kota Raja, only 18 faloak trees were found. The recently debarked trees in Kota Raja, Alak, and Maulafa were 54.12%, 49%, and 41.05%, respectively. Meanwhile, trees with recovered bark were found mainly in Kelapa Lima (50%), Oebobo (38.95%), and Kota Raja (31%). Most debarked faloak trees were those closest to roads and settlements with a diameter ranging from 10.38 to 89.17 cm. The distance from the road to the trees was 1-203 m. A large number of debarked faloak trees indicates a high demand for faloak bark.
... In contrast, all our analyses suggest that the traditional 'late' harvest of golden-grass flower stalks has little effect on population dynamics. The timing of harvest has been shown to affect the impacts of harvest in other systems (Delvaux et al., 2010;Joyal, 1996) and strongly determines the ecological impacts of goldengrass harvesting. ...
Article
Sustainable harvest of non-timber forest products (NTFPs) can play an important role in biodiversity conservation and livelihoods. However, harvesting policy intended to promote conservation are frequently either ineffective or too complicated. Successful policies should consider ecological impacts, local ecological knowledge and management practices, but NTFP policies are rarely based on these elements. Syngonanthus nitens (Eriocaulaceae, ‘golden-grass’) is one of the most valuable NTFPs from the Brazilian savanna. The handicrafts made from this species’ flower stalks are traditional to the Jalapão region, Tocantins state, but have expanded over a much larger area in recent years. We combined ethnoecological interviews, seed phenology surveys over a large geographical area and harvest experiments in nine sites over 3 years to assess local ecological knowledge and management of golden-grass and its long-term effects on population dynamics. Although handicrafting activities are rapidly expanding, local ecological knowledge associated with harvest or management has not been transferred or created outside of Jalapão. Matrix population models illustrate that harvest according to traditional management practices had no impact on golden-grass population dynamics. Earlier harvest of golden-grass, as practiced by new artisans, leads to population decline due to plant uprooting. Local policies for golden-grass harvest are consistent with traditional management, limit the timing but not the quantity of harvest, and are appropriate over a wide geographical scale. Golden-grass and other wild harvested species with similar characteristics hold high potential to help conserve threatened habitat.
... As a first step, ethnobotanical interviews were conducted with traditional healers and local people in order to learn their preferences regarding the tree species used for health care (Bockx, 2004). Subsequently, 12 of the most frequently used trees species were chosen for a study of bark recovery (Table 1) over a two-year period following bark harvesting (Delvaux et al., 2009(Delvaux et al., , 2010. As the results of these studies showed a wide diversity of responses by trees to bark harvesting, we concentrated on the same 12 species from the Forêt Classée des Monts kouffé to collect samples. ...
... Indeed, tree wounds caused from bark stripping by red deer (Cervus elaphus) and moose (Alces alces) in Scottish and Lithuanian forest stands, respectively, have been found to persist for >14 years (Vasiliauskas 1998;Welch et al. 1997). Similarly, in a bark stripping experiment of tropical medicinal trees, 5 of 12 species had healing rates (i.e., bark replacement) of <30 cm 2 /year (Delvaux et al. 2010). For comparison, mean gouge hole area in our data set was 194.1 cm 2 . ...
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Resource distribution shapes many aspects of primate behavioral ecology. Though the spatial patterning of fruits, leaves, and insects has been explored among primate foods, comparatively less is known about exudate distributions. Tree exudates are a renewable resource, provide long-term evidence of exploitation, and may be selectively exploited to manipulate spatial distribution. We assessed the spatial patterning of trees gouged by common marmosets (Callithrix jacchus) to determine if they exhibit a uniform, random, or clumped distribution. We also asked whether marmosets selectively gouge trees in home range centers, which may afford them exclusive access to exudates. We explored whether spatial or physical characteristics of trees predict how intensely gouged trees were exploited. The mean nearest neighbor distance of gouged trees was significantly closer than expected for a random distribution and Ripley’s K-function showed that gouged trees were clumped across all spatial scales in our study area. Clumping may enable marmosets to reduce day and home ranges and facilitate repeated gouging of trees. Gouged trees were not closer to marmosets’ home range centers than peripheries, nor were centrally located trees more intensely gouged. Increased gouging intensity was associated with larger tree circumferences, although this effect was primarily driven by interspecific differences in circumference. Although marmosets may benefit from exploiting clumped exudates, they do not concentrate gouging in areas where they are more likely to gain exclusive access. Species-specific tree characteristics such as exudate quality and/or bark properties may play a larger role in determining gouging patterns than intergroup feeding competition.
... However, the availability of several of the most popular fruit species had decreased markedly. Furthermore, destructive harvesting techniques and increasing market pressures were rapidly depleting wild populations [102,103]. Conflict between different uses of trees for timber and NWFP can pose additional threats. ...
Article
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With the growing demands from a population expected to reach 9 billion people by 2050, it is unclear how our current global food system will meet future food needs. Ensuring that all people have access to adequate and nutritious food produced in an environmentally and socio-culturally sustainable manner is one of the greatest challenges of our time. ―Sustainable diets‖ have been proposed as a multidimensional framework to address the need for nutritious and adequate food in the context of the many challenges facing the world today: reducing poverty and hunger, improving environmental health, enhancing human well-being and health, and strengthening local food networks, sustainable livelihoods and cultural heritage. This paper examines the contribution of forests and trees to sustainable diets, covering among others, nutritional, cultural, environmental and provisioning aspects. The literature reviewed highlight major opportunities to strengthen the contribution of forest and tree foods to sustainable diets. However, several constraints need to be removed. They relate to: cultural aspects, sustainable use of non-wood forest products, organization of forest food provisioning, limited knowledge of forest food composition, challenges in adapting management of forests and trees to account for forest foods, and in integrating forest biodiversity into complex landscapes managed for multiple benefits. Finally, the paper identifies research gaps and makes recommendations to enhance the contribution of forest foods to sustainable diets through increased awareness and better integration of information and knowledge on nutritious forest foods into national nutrition strategies and programs.
... However, the availability of several of the most popular fruit species had decreased markedly. Furthermore, destructive harvesting techniques and increasing market pressures were rapidly depleting wild populations [102,103]. Conflict between different uses of trees for timber and NWFP can pose additional threats. ...
Article
Full-text available
With the growing demands from a population expected to reach 9 billion people by 2050, it is unclear how our current global food system will meet future food needs. Ensuring that all people have access to adequate and nutritious food produced in an environmentally and socio-culturally sustainable manner is one of the greatest challenges of our time. ―Sustainable diets‖ have been proposed as a multidimensional framework to address the need for nutritious and adequate food in the context of the many challenges facing the world today: reducing poverty and hunger, improving environmental health, enhancing human well-being and health, and strengthening local food networks, sustainable livelihoods and cultural heritage. This paper examines the contribution of forests and trees to sustainable diets, covering among others, nutritional, cultural, environmental and provisioning aspects. The literature reviewed highlight major opportunities to strengthen the contribution of forest and tree foods to sustainable diets. However, several constraints need to be removed. They relate to: cultural aspects, sustainable use of non-wood forest products, organization of forest food provisioning, limited knowledge of forest food composition, challenges in adapting management of forests and trees to account for forest foods, and in integrating forest biodiversity into complex landscapes managed for multiple benefits. Finally, the paper identifies research gaps and makes recommendations to enhance the contribution of forest foods to sustainable diets through increased awareness and better integration of information and knowledge on nutritious forest foods into national nutrition strategies and programs.
... Influenced by climatic conditions, vascular cambium shows great variation in the period and intensity of activity (Fahn 1985), which impacts on wound recovery and tree response to damage inflicted on tree bark during different seasons (Kozlowski et al. 1991, Schmitt and Liese 1992, Delvaux et al. 2010a. The way and the rate that new secondary tissue differentiate are further influenced by the type of tissue exposed by wounding and the ambient conditions during wound closure (Dickison 2000). ...
Article
Tree bark is commonly used for traditional medicine in southern Africa and further afield. Increasing demand and commercialisation have resulted in the overexploitation of many species, posing a major challenge to forest managers to develop mechanisms for sustainable resource use. An experimental bark harvesting research project was initiated in the southern Cape, South Africa, to inform best practices for bark harvesting based on tree response to bark stripping. The species selected for the study, Ocotea bullata, Curtisia dentata and Rapanea melanophloeos, are much sought after and well represented in southern Cape forests. The treatment entailed removing vertical strips of bark, 1 m in length and of different strip widths, covering the full range of tree size classes ≥10 cm DBH. The treatments were applied during two seasons, winter and summer. Evaluations were done every six months to assess tree response to bark stripping in terms of bark regrowth through phellogen edge and sheet development, and susceptibility to insect and fungal damage. The results show a differential response of tree species in terms of phellogen edge and sheet growth, as well as susceptibility to fungal and insect attack. Rapanea melanophloeos was the most vulnerable to fungal and insect damage and displayed little bark regrowth following wounding. Curtisia dentata showed best bark regrowth through sheet development. Only O. bullata, though, showed adequate bark regrowth (through edge development) to allow for sustainable strip harvesting. Bark regrowth is influenced by season of stripping, although this is difficult to define considering the wide range of environmental and other factors affecting tree response to bark removal. Smaller trees are more vulnerable to bark stripping, especially with a wide strip, with poorer bark regrowth than bigger trees.
... The results revealed that bark regeneration was faster in younger and middle aged trees which corroborates with the findings that trees of Pseudocedrela kotschyi had similar pattern, i.e., medium sized trees (21-30 cm dbh) had a faster bark recovery than the other studied dbh classes. [16] Strip harvesting (method III) showed faster bark regeneration in all the GBH groups in both the species because in this method only small portion of bark was removed, resulting in smaller wound. Moreover, bark regeneration was also faster during initial 6 months due to plant wound closure mechanisms that occur during initial few months after wounding. ...
Article
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Holarrhena antidysenterica R. Br. Sans (Kutaj) belonging to family Apocyanaceae is a small tree or shrub. Its bark is used as an astringent, anthelmintic, stomachic, febrifuge, diuretic, and also useful in piles, dyspepsia, chest infections, amoebic dysentery, and other gastric disorders. Increasing demand and destructive harvesting of bark has led to the depletion of this valuable medicinal tree. A study was conducted to standardize sustainable harvesting practices of stem bark and suitability of alternative plant parts. Different bark harvesting methods were experimented. In these methods tree girth was divided into three or four equal parts and the bark was extracted from one part and harvesting was done by removing longitudinal strips from the main trunk of the tree. Alternate/opposite strips were also experimented in younger/thinner trees. The harvested bark samples and different plant parts like twig bark, wood, flowers and leaves were analysed for tannins, total phenols, total alkaloids and total flavonoids. Phytochemical analysis revealed that the active ingredients in trunk bark were comparatively higher, i.e., total phenols (7.51±0.12%), total flavonoids (0.19±0.09%), total alkaloids (2.25±0.06%), and tannins (8.61±0.10%) than other plant parts studied. Strip harvesting was found to be the best method for harvesting and by this method the bark can be harvested on sustainable basis after every 18 months. Bark should be harvested by removing only outer and middle bark leaving the inner bark for regeneration.
... Additional observations are needed to confirm these familial differences between cambial dieback extent, although the variation observed in these data sets is consistent with findings from outside the coring literature. It can be concluded that post-wounding dieback and bark recovery can differ markedly and consistently among species (Romero & Bolker, 2008;Delvaux, Sinsin & Van Damme, 2010). ...
Article
Trees are natural repositories of valuable environmental information that is preserved in the growth and structure of their stems, branches and roots. Dendrochronological analyses, based on the counting, crossdating and characterisation of incrementally formed wood rings, offer powerful insights for diverse fields including ecology, climatology and archaeology. The application of this toolset is likely to increase in popularity over coming decades due to advances in the field and a reduction in the cost of analyses. In research settings where the continued value of living trees subject to dendrochronological investigation is important, the use of an increment bore corer to extract trunk tissue is considered the best option to minimise negative impacts on tree health (e.g. stress and fitness). A small and fragmented body of literature, however, reports significant after-effects, and in some cases fatal outcomes, from this sampling technique. As it stands, the literature documenting increment bore coring (IBC) impacts lacks experimental consistency and is poorly replicated, making it difficult for prospective users of the method to assess likely tree responses to coring. This paucity of information has the potential to lead to destructive misuse of the method and also limits its safe implementation in circumstances where the risk of impacts may be appropriate. If IBC is to fulfil its potential as a method of choice across research fields, then we must first address our limited understanding of IBC impacts and provide a framework for its appropriate future use. Firstly, we review the historical context of studies examining the impacts of IBC on trees to identify known patterns, focal issues and biases in existing knowledge. IBC wound responses, particularly those that impact on lumber quality, have been the primary focus of prior studies. No universal treatment was identified that conclusively improved wound healing and few studies have linked wound responses to tree health impacts. Secondly, we build on literature insights using a theoretical approach to identify the most important factors to guide future research involving implementation of IBC, including innate tree characteristics and environmental factors. Thirdly, we synthesise and interrogate the quantitative data available through meta-analysis to identify risk factors for wound reactions. Although poor reporting standards, restricted scopes and a bias towards temperate ecosystems limited quantitative insight, we found that complete cambial wound closure could still harbour high rates of internal trunk decay, and that conditions favouring faster growth generally correlated with reduced indices of internal and external damage in broadleaved taxa. Finally, we propose a framework for guiding best-practice application of IBC to address knowledge gaps and maximise the utility of this method, including standardised reporting indices for identifying and minimising negative impacts on tree health. While IBC is an underutilised tool of ecological enquiry with broad applicability, the method will always incur some risk of negative impacts on the cored tree. We caution that the decision to core, or not to core, must be given careful consideration on a case-by-case basis. In time, we are confident that this choice will be better informed by evidence-based insight. © 2015 Cambridge Philosophical Society.
... However, the harvesting of bark can be ecologically sustainable (Stanley et al. 2012). For example, Delvaux et al. (2010) showed that Carapa procera can survive directory debarking. Unfortunately, in many cases, bark is exploited unsustainably (Ticktin 2004;Schmidt et al. 2011). ...
Article
Abstract Boswellia dalzielii Hutch. is a valuable West African native frankincense tree species. The stem bark has a high traditional medicinal value throughout its range. The resin has great economic potential even though it is little exploited in West Africa, making it one of the neglected and underutilized species. Current anthropogenic pressure on natural habitats coupled with climate change are serious threats to the species. As such, gathering and synthesizing existing information on the species are necessary for its sustainable management. Thus, this study aims to synthesize existing knowledge on B. dalzielii and to identify priorities for future research. Articles were searched in Google Scholar, Web of Science, Scopus, and Open-Thesis. One hundred and eight (108) publications were recorded and analyzed. Results showed that more than half (51 %) of the studies were conducted in the last four years (2017-2020). The majority (57 %) of the studies focused on medicinal properties and 20 % specifically on phytochemistry, with a wide variety of therapeutic properties and traditional medicinal uses identified. The species is widely distributed throughout sub-Sahel and Sudanian regions of Africa, typically occurring in low-density stands with populations concentrated in Burkina Faso, Cameroon, and Nigeria. However, natural regeneration is often limited, with poor seed fertility and reduced seedling recruitment in stands. Given the socioeconomic value and regeneration concerns, research is urgently needed on the species population biology and ecology, its population genetics, effective propagation methods, and sustainable resin harvesting practices and management. Keywords: Boswellia, Non-timber forest products, medicinal species, review, propagation, semi-arid area.
... Local communities all over the world have harvested NTFPs for centuries and their use for subsistence has not really put a high burden on the natural resource base, except in special situations such as civil wars, etc. (Arnold and Pérez 2001; Sundriyal and Sundriyal 2004). However, when NTPF markets are developing and demand is growing, many local communities experience diminishing resource availability due to overexploitation and unsustainable harvest practices to obtain immediate financial gains (Delvaux et al. 2010;Sundriyal and Sundriyal 2004). According to the typology of Ruiz-Pérez et al. (2004), cases ...
... L'Afrique dispose d'une diversité biologique très élevée, à tel point que l'avenir de notre planète dépend de sa survie. Mais cette survie se voit menacée par des attaques catastrophiques dues aux variations climatiques provoquées ou non et aux interventions humaines contrôlées ou non ( Adjanohoun et al., 1999 ;Delvaux et al., 2010). ...
Article
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Southern-Benin has a mosaic of ecological conditions that have contributed to the development of its vast forest heritage. The combination of a number of parameters or indices (use value, diversity index, and equitability and citation frequency) is an effective way of identifying the most important plants for preservation. The objective was to carry out the checklist of the plants used around the classified forests of Ahozon and Lama and the botanical reserve of Pobè in Southern-Benin, with information on their use, threats and relations between the targeted habitats and the listed plants on the one hand and the knowledge associated with them and the socio-professional characteristics of the populations on the other. The data (user identity, plants used, plant organs collected, uses, plant threats) were collected from 113 individuals interviewed individually during an ethnobotanical study in 20 villages distributed around the three vegetation formations. The results showed that 59 plant species are useful for the populations surrounding the formations. The most important in terms of use value are Zanthoxylum zanthoxyloides (VUT = 7.86), Irvingia gabonensis (VUT = 7.84), Dialium guineense (VUT = 7.69), Khaya senegalensis (VUT = 7.46), Prosopis africana (VUT = 7.06), Ceiba pentandra (VUT = 7.01), and Synsepalum dulcificum (VUT = 6.98). The indices of Diversity and Equitability of the respondents reveal that knowledge on plant species is not homogeneously distributed (ID = 0.430, IE = 0.451 <0.5) and maximum information on species is held by a part of the population. Pruning (40%) is the main source of species threats. Plantation, agrosystems, sensitizing populations on good methods of harvest could help to preserve the main plants useful for the populations of Southern Benin.
... These results indicate that these four species have different levels of resistance to deer browsing, with the highest being shown by A. carpinifolium. Similar findings were obtained in several previous studies based on simulated experiments of browsing and debarking (Noel 1970;Bergström and Danell 1987;Delvaux et al. 2010). The high resistance of A. carpinifolium is considered to be due to its high rates of adventitious bud production and regrowth of bark, including the cambium layer and phloem, after browsing and debarking. ...
Chapter
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Over the last few decades, population increases of sika deer (Cervus nippon) have become a major issue in various forest ecosystems across temperate regions; however, the influences of deer browsing on riparian forests are less known. In this chapter, we illustrate the herbivore–forest vegetation relationships over a long term from the past when deer was absent to the current when deer became overabundant in an old-growth riparian forests of Ooyamazawa, the Chichibu Mountains of central Japan. We revealed that (1) the browsing activity of deer has a negative influence on riparian forests, (2) the damage of these species is mainly induced by easiness to browsing by deer resulting from small tree size structure, and (3) the resistance to the deer browsing differs among tree species. Thus, small mature trees (i.e., shrub species) with low browsing resistance should be primarily protected for effective management of riparian forests.
... Tree bark provides protection against desiccation, fire, insects and diseases, and plays an important role in the progression of nutrients between leaves and roots via the phloem tissue. Thus debarking may infer stress for trees and amplify vulnerability to external agents, such as insects (Delvaux, Sinsin, & Damme, 2010;Gaoue & Ticktin, 2010;Purohit, Maikhuri, Rao, & Nautiyal, 2001). In fact, bark harvesting has been reported to alter tree survival, growth and reproduction in a range of species worldwide (Botha et al., 2004;Purohit et al., 2001). ...
Article
We studied the impact of debarking of medicinal tree species on the diversity of xylophagous beetles in Lama Forest Reserve, in Lokoli swampy forest and in crop fields surrounded Lokoli forest. A total of 108 interception traps were set up on debarked and nondebarked trees covering nine medicinal plants that are Anogeissus leiocarpa, Dialium guineense, Khaya senegalensis in Lama Forest; Nauclea diderrichii, Ficus trichopoda, Syzygium owariense in swampy forest; and Parkia biglobosa, Bridelia ferruginea, Pterocarpus erinaceus in crop fields. A total of 116 beetle species were collected belonging to 19 coleoptera families with higher xylophagous beetles than predators. Specific richness and individual abundance of xylophagous beetles were significantly higher in crop fields than in forests. Furthermore, in all habitats, debarked‐tree species were more attractive to xylophagous beetles than control trees and were significantly more attacked in crop fields than forests. The most vulnerable medicinal trees to debarking were P. biglobosa, D. guineense, F. trichopoda and P. erinaceus. Three groups of indicator insects according to habitat type, debarking and tree species have been distinguished. Our results clearly imply that by exploiting natural resources humans can impact on the abundance and specific richness of xylophagous beetles by modulating their resources. Nous avons étudié l'impact de l’écorçage des espèces d'arbres médicinaux sur la diversité des coléoptères xylophages dans la Forêt Classée de la Lama, dans la forêt marécageuse de Lokoli et dans les champs cultivés autour de la forêt de Lokoli. Un total de 108 pièges d'interception ont été installés sur des arbres écorcés et non écorcés couvrant neuf plantes médicinales qui sont Anogeissus leiocarpa, Dialium guineense, Khaya senegalensis dans la Forêt de la Lama; Nauclea diderrichii, Ficus trichopoda, Syzygium owariense dans la forêt marécageuse et Parkia biglobosa, Bridelia ferruginea, Pterocarpus erinaceus dans les champs cultivés. Au total, 116 espèces de scarabées appartenant à 19 familles de coléoptères ont été collectées affichant des taux de coléoptères xylophages plus élevés que les prédateurs. La richesse spécifique et l'abondance individuelle des coléoptères xylophages étaient significativement plus élevées dans les champs de culture que dans les forêts. De plus, dans tous les habitats, les espèces d'arbres écorcés étaient plus attractives pour les coléoptères xylophages que les arbres témoins et étaient beaucoup plus attaquées dans les champs cultivés que dans les forêts. Les arbres médicinaux les plus vulnérables à l’écorçage étaient P. biglobosa, D. guineense, F. trichopoda et P. erinaceus. Trois groupes d'insectes indicateurs ont été distingués en fonction du type d'habitat, de l'écorçage et des espèces d'arbres. Nos résultats laissent clairement entendre qu'en exploitant les ressources naturelles, les humains peuvent influer sur l'abondance et la richesse spécifique des coléoptères xylophages en modulant leurs ressources.
... Indeed adult trees of P. africana were few and scattered in all sites and may not provide adequate seeds to subdue its competitors [56]. Excessive debarking including ring barking of the stems lead to death of the tree in two years [57], increased canopy openings and subsequent invasion of S. mauritianum weed. Indeed [58] observed that S. mauritianum had established itself in Mau forest hence could have provided stiff competition to P. africana regenerations resulting in their poor establishment. ...
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Prunus africana has been severely exploited for its valuable products rendering it unstable and at risk of extinction. Studies were therefore carried out on its regeneration density and population structure across different human disturbance gradients in South West Mau Forest (SWMF) Kenya. Four study sites with {undisturbed, low, moderate and high} human disturbances were identified in SWMF. In each study site three line transects, 100 m apart and running up to 1 km inside the forest were established. Four sample plots 20 m x 50 m were laid at 250 m intervals along each line transect then divided further into 10 subplots each 10 m x 10 m and nested 5m x 5 m sub-subplots. At the centre of each sub-subplot, a 1 m x 1 m quadrant was laid. In each sub plot Diameter at Breast Height (DBH) of all adult trees and poles were measured while the number of saplings in each sub-subplot and seedlings in each quadrant were counted. Light screening efficiency was evaluated in all study sites as an indicator of canopy openings. One way Analysis of Variance (ANOVA) was used to test for significant differences of the studied variables, Tukey Post Hoc test was used in pairwise mean comparison and parametric Pearson correlation analysis was used to test for relationship between variables. Bar graphs and line graphs were used to depict trends in population structure and diameter-size distribution respectively. Animal trails, old charcoal production sites, tree harvesting and debarking of P. africana were found as significant human forest disturbances (p < 0.05) that negatively influenced its relative abundance (r =-0.077). Canopy openings as consequence of disturbance negatively influenced its regeneration density (r =-0.089). The relatively undisturbed site of the forest had a stable population structure for P. africana that followed reverse-J curve irrespective of the high debarking rate (90%) that decreased across the disturbance gradient. These findings suggest a need for designing sustainable management strategies that will lead to rehabilitation, restoration and monitoring of P. africana population dynamics in SWMF.
... Removal of bark can negatively impact the growth of trees (Delvaux et al. 2010;Tsen et al. 2016) and makes trees susceptible to rotting, infection and death (Shigo 1986;Dujesiefken et al. 1999). The current methods employed by local harvesters to examine trees for the presence of ebony heartwood are highly destructive. ...
Article
Ebony wood, the black heartwood of trees in the genus Diospyros, is a high-value commodity of many Pacific Islands. The revenue earned from the sale of ebony carvings is important for many low-income rural communities, resulting in high harvesting pressure and reported declines of ebony-producing species. This study investigates the impact of ebony wood harvesting on species of Diospyros on Vangunu Island, Western Solomon Islands. Diospyros samoensis, locally known as ‘rihe’, was the main source of ebony wood, with D. vera occasionally harvested but producing poorer quality wood. For D. samoensis, we investigated the existing ethnobotanical knowledge and harvesting dynamics using questionnaires and surveyed 11 populations using five 15 � 15 m plots. Although D. samoensis was common throughout the study area, trees with harvestable ebony heartwood were considered rare. The sale of ebony carvings contributed substantially to the livelihood of carvers. Harvesting practices cause considerable damage to the stem and appeared to alter population structure, with fewer seedlings found in stands with higher harvesting intensities (r 1⁄4 –0.704, P 1⁄4 0.008). Therefore, populations of D. samoensis appear to be negatively impacted by current harvesting practices, which should be modified to (1) cause less damage to individual trees and populations, and (2) protect larger and older trees to help regeneration. Therefore, the increasing rarity of ebony heartwood in the Pacific may not equate to dangerous declines in Diospyros species and implementing low-impact harvesting practices could help improve the health and long-term persistence of Diospyros populations.
... Such exploitation of baobab parts emphasizes the role of the baobab as a multi-purpose species (Schumann et al., 2010). According to Delvaux et al. (2009), harvesting of vegetative structures (like leaves and bark) significantly threatens the survival of plant populations as the plant parts that affect photosynthesis are damaged or removed. This corroborates with the findings of Peters (1996) that when bark, fruit, wood and other parts of a species are harvested for various uses, there may be significant impacts on the population structure and distribution of the species. ...
Article
The baobab (Adansonia digitata L.) tree has multiple uses and is highly valued in Southern Africa, particularly in the rural communities where people depend on this resource for their livelihoods. However, few studies have been conducted on the usefulness of this high value plant species in Namibia. The aim of this study was to document the biology and local uses of baobab populations in Outapi and Onesi sites in Omusati Region, Namibia. A comparison of densities, distribution patterns, structure, phenology, stem conditions and uses of baobabs between the two sites was done. Road transects were used to identify focal trees which in turn were used to determine the placement of circular plots. In each plot, diameter at breast height (dbh) of adult and sub-adult trees, height of adults, sub-adults and saplings and their stem conditions, number of fruits on each fruiting baobab tree, occurrence data and the land-use types where baobabs occurred were recorded. The results revealed significant differences in the dbh-size and height classes between the two study sites. The bell-shaped distribution curve in dbh size-classes in the two sites suggests poor recruitment. The results revealed that Onesi villagers made more use of the baobab tree than Outapi urban residents. Some of the common uses of baobabs in both study sites included the use of baobab fruit for human consumption and the use of the baobab bark and leaves as livestock fodder. Additionally, the people of Outapi and Onesi use the baobab fruit and bark to treat certain ailments such as cold, flu and diarrhea.
... The high demand for medicinal plants fuels the non-sustainable harvesting of medicinal plant species. 18,19 This will consequently lead to loss and depletion of wild-harvested medicinal plant species, which in turn will threaten the health care not only in Njeru-Uganda but also worldwide. 20,21 This is due to lack of a proper strategy of conservation and organizing the commercial trade of the plants and integrating the development from production to consumption. ...
... Open Access ring-barking often leads to the death of the tree and thus extensive harvesting of bark may lead to a decrease in tree density (e.g. Delvaux, Sinsin & Van Damme 2010). There were few indications of ring-barking in the Pirie forest (E.J.O., M.I.C., N.P.M. pers. ...
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Forests in South Africa are harvested by local communities for multiple purposes and this affects the animals that inhabit them. The tree hyrax (Dendrohyrax arboreus) has a restricted distribution and utilises various tree species as dens and a source of food. In this article, we determined, through a series of interviews in the communities surrounding the Pirie forest, which plant species are harvested by local people and whether these overlap with those used by the tree hyrax. In addition, we determined the extent to which tree hyraxes are hunted by these communities. Of the trees used by the hyrax as dens in the Pirie forest, Afrocarpus falcatus, Schotia latifolia, Andrachne ovalis, Teclea natalensis and Apodytes dimidiata are important resources for local communities. But as these are harvested at relatively low levels, it is unlikely that current harvesting has a large impact on the tree hyrax. Opportunistic hunting occurs, but the hyrax is not targeted by hunters. Very limited commercial harvesting of A. falcatus has been taking place in the Pirie forest since 1975, but its impact on the hyrax population, although undetermined, is also unlikely to be high. We recommend that the Pirie forest tree hyrax population should be monitored by forest management in order to ascertain the impact of both commercial and community harvesting over the past quarter-century. Conservation implications: Tree hyrax populations in the Pirie forest should be actively monitored by management on an annual basis.
... The ecological impacts of bark harvest can be detrimental to some non-resistant species (Chungu et al., 2007). Effects may also depend on management practices, harvest intensity, and climatic conditions (Delvaux et al., 2010;Gaoue and Ticktin, 2010). Medicinal trees can be subjected to multiple modes of harvests when different plant parts are used for different purposes including non-medicinal NTFP uses (Gaoue and Ticktin, 2007;Ticktin et al., 2012). ...
Article
Medicinal plants support the healthcare needs of the most vulnerable human populations, including the rapidly increasing urban poor in developing countries. However, little is known about the role of urban forests in supplying traditional herbal remedies compared to those in rural areas. Different parts of medicinal species could be used to supply different forest products, and multiple uses may exacerbate impacts to the species. We focused on the debarking and cutting of woody species harvested for medicine and fuelwood in an urban forest in Nairobi, Kenya. Since informal harvest was common, we surveyed the signs of harvest (i.e., stem debarking and cutting) in the forest rather than conducting household interviews. The survey covered a total of 14,993 stems of 93 species, of which 9,169 were standing and 5,824 were cut. Among those standing, 172 stems of nine species were debarked. The barks of most of the nine species were known to be used as traditional medicine in the region. Debarking was concentrated on Warburgia ugandensis and Elaeodendron buchananii, which were also affected by cutting, and we analyzed them in detail. Debarking occurred primarily on larger stems of W. ugandensis and E. buchananii, and cutting more frequently involved smaller W. ugandensis stems. Debarking and cutting of E. buchananii was concentrated near the low-income housings adjacent to the forest. Patrolling nearly failed to protect either species from debarking and cutting. We discussed management options of the urban forest including reformed patrolling strategy and planting of useful species in degraded areas, and demonstrated how our approach could aid the management of informal and multiple uses of urban forest products.
... To the best of our knowledge, no scientific literature is available about the variation in the frequency of these utilization types by taxon and diameter category. However, the type and extent of wounds can affect the ability of trees to survive and regenerate (Delvaux et al., 2010;Vacek et al., 2020). Foraging intensity, as well as taxon and diameter selectivity, are also influenced by the distance from the water, according to the optimal and the central-place foraging strategy (Jenkins, 1980), so the beaver impact varies on a small spatial scale. ...
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1. Herbivore species can either hinder or accelerate the invasion of woody species through selective utilization. Therefore, an exploration of foraging decisions can contribute to the understanding and forecasting of woody plant invasions. Despite the large distribution range and rapidly growing abundance of beaver species across the Northern Hemisphere, only a few studies focus on the interaction between beavers and invasive woody plants. 2. We collected data on the woody plant supply and utilization at 20 study sites in Hungary, at two fixed distances from the water. The following parameters were registered: taxon, trunk diameter, type of utilization, and carving depth. Altogether 5401 units (trunks and thick branches) were identified individually. We developed a statistical protocol that uses a dual approach, combining whole-database and transect-level analyses to examine foraging strategy. 3. Taxon, diameter, and distance from water all had a significant effect on foraging decisions. The order of preference for the four most abundant taxa was Populus spp. (softwood), Salix spp. (softwood), Fraxinus pennsylvanica (invasive hard-wood), and Acer negundo (invasive hardwood). The diameter influenced the type of utilization, as units with greater diameter were rather carved or debarked than felled. According to the central-place foraging strategy, the intensity of the foraging decreased with the distance from the water, while both the taxon and diameter selectivity increased. This suggests stronger modification of the woody vegetation directly along the waterbank, together with a weaker impact further from the water. 4. In contrast to invasive trees, for which utilization occurred almost exclusively in the smallest diameter class, even the largest softwood trees were utilized by means of carving and debarking. This may lead to the gradual loss of softwoods or the transformation of them into shrubby forms. After the return of the beaver , mature stages of softwood stands and thus the structural heterogeneity of
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The article discusses the contributions of forest foods to sustainable diets. Traditionally, policy-makers have focused on energy-rich staple crops such as wheat, rice and maize in the quest for national and global food security. Forest foods such as wild fruits, nuts, vegetables, mushrooms and animal products contribute in many ways to food security. The dietary quality of many forest foods is high. Many of the micronutrients provided by forest foods have important health and developmental functions, and their absence in diets therefore has important health implications. Even though the nature of much of the available evidence is circumstantial, a growing body of data indicates that increased agricultural and forest biodiversity leads to a more varied diet, which in turn improves human health. Animal-based foods supply many important micronutrients in much higher amounts or with higher bioavailability than most plant-based foods.
Article
The little studied Mount Cameroon Francolin Pternistis camerunensis is endangered and strictly endemic to the undergrowth of Mount Cameroon’s primary forest. We surveyed the species in the Mount Cameroon National Park in July–August 2016 using call playback at 86 plots systematically placed along 17 transects in an attempt to assess the occupancy and conservation threats to the species. The study’s three main results are as follows. Firstly, Mount Cameroon Francolin occurred in the stratified vegetation types across the altitudinal range of 1,023–2,186 m. Secondly, the response rates of francolin were 15% in submontane forest (800–1,600 m altitude range); 80.8% in montane forest (1,600–1,800 m); 3.9% in montane scrub (1,800–2,400 m); and nil in the lowland forest (0–800 m). Thirdly, bird abundance significantly increased with latitude, ground vegetation height, presence of Prunus africana and tall grass cover but decreased with the density of small trees and disturbance caused by heavy Prunus exploitation, and also, based on indirect evidence, hunting. We recommend: (1) systematic use of call playback in monitoring the population status of francolins; (2) an increase in patrolling and law enforcement to control illegal hunting, land clearance and burning of the upper slopes; (3) promotion of sustainable harvesting of Prunus and agroforestry practices aimed at curbing land clearance in the park surroundings. Further research priorities and conservation strategies have been suggested based on this study’s emerging results.
Article
Our study assessed the effectiveness of species debarking in controlling species invasion and the change in seedling dynamics after application of the different treatments. A split plots design was used in two forest reserves to assess the effectiveness of three debarking treatments: complete ring debarking, partial ring debarking and a control (no debarking). The results reveal that ring debarking has the potential to be used to control invasive species such as Cecropia peltata L. and Broussonetia papyrifera (L.) Vent. The efficiency, however, was influenced by the extent of the wound created and the size of tree, especially if trees are partially debarked. The control method also stimulated natural regeneration of native species with higher regeneration of native species recorded compared to invasive species. Also, plots that had completely debarked trees had higher species diversity than the partially debarked and the control plots in one of the reserve. The fact that none of the trees in the control plots died is indication of the effectiveness of debarking in the control of invasive species considered here. The effectiveness of this method suggests it is a suitable option for killing small to medium size trees with little cost to the environment compared to the application of arboricides for instance and is therefore worth revisiting in silvicultural treatments where minimum environmental disturbance is required. We recommend more studies to compare the effectiveness of the control approaches on different invasive species and monitor how the native communities respond including in terms of species diversity and functional groups, since removal methods may impact differently on these plant community traits.
Chapter
There is growing knowledge about and appreciation of the importance of Non-timber Forest Products (NTFPs) to rural livelihoods in developing countries, and to a lesser extent, developed countries. However, there is also an assumption on the part of policy-makers that any harvesting of wild animal or plant products from the forests and other natural and modified ecosystems must be detrimental to the long-term viability of target populations and species. This book challenges this idea and shows that while examples of such negative impacts certainly exist, there are also many examples of sustainable harvesting systems for NTFPs. The chapters review and present coherent and scientifically sound information and case studies on the ecologically sustainable use of NTFPs. They also outline a general interdisciplinary approach for assessing the sustainability of NTFP harvesting systems at different scales. A wide range of case studies is included from Africa, Asia and South America, using plant and animal products for food, crafts, textiles, medicines and cosmetics.
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Hydro-geomorphic processes have significantly influenced the recent development of valley floors, river banks and depositional forms in mountain environments, have caused considerable damage to manmade developments and have disrupted forest management. Trees growing along streams are affected by the transported debris mass and provide valuable records of debris flow/flood histories in their tree-ring series. Dendrogeomorphic approaches are currently the most accurate methods for creating a chronology of the debris flow/flood events in forested catchments without any field-monitoring or a stream-gauging station. Comprehensive studies focusing on the detailed chronology of hydro-geomorphic events and analysis of meteorological triggers and weather circulation patterns are still lacking for the studied area. We provide a spatio-temporal reconstruction of hydro-geomorphic events in four catchments of the Hrubý Jeseník Mountains, Czech Republic, with an analysis of their triggering factors using meteorological data from four nearby rain gauges.
Article
Tree bark is widely used in traditional medicine in southern Africa. The growing demand for medicinal bark requires scientifically sound harvest systems for sustainable use. A conceptual framework and decision matrix are presented to aid forest managers in selecting the most appropriate system for the sustainable harvesting of particular species. The conceptual framework is based on the results of experimental bark harvesting of selected forest and woodland tree species in southern Africa, where tree response to bark stripping was assessed. The extent and rate of bark regrowth and the susceptibility of the exposed wood to fungal and insect damage, are of particular importance to assess harvest options. The decision matrix groups species based on tree response to bark stripping, and identifies the most appropriate harvest option for a particular species. Species-specific harvest prescriptions are formulated and alternatives to strip harvesting are identified where avoidance is advised. The conceptual framework and decision matrix were applied to forest woodland species on which experimental bark harvesting was conducted in Malawi, South Africa and Zambia. Of the 22 species studied, 10 have the potential for strip harvesting, based on extent of bark regrowth and susceptibility to fungal and insect damage. These were assessed further in terms of prescriptions for strip harvesting. For the remainder, full-tree harvesting in a single-tree selection system would be the most viable harvest option. Alternatives to strip and full-tree harvesting are also discussed.
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Many people in the semi-arid tropics strongly depend on non-timber forest products (NTFPs) for livelihood. Increasing threats on NTFP-providing tree species, due to land-use intensification and over-harvesting, require ecological studies as well as additional information provided by local people. One important NTFP-providing tree in West Africa is Anogeissus leiocarpa. Even though this species is highly used, ethnobotanical studies on A. leiocarpa are scarce and address mainly qualitative aspects. Our study investigates uses, perceptions of the population development, and management strategies of A. leiocarpa among the Gulimanceba people in eastern Burkina Faso. We conducted a quantitative ethnobotanical survey and investigated distribution of traditional ecological knowledge related to the species on a local scale, i.e. difference in knowledge between villages, genders, and generations. Interviews reveal that A. leiocarpa is harvested by local people for 18 different uses and emphasize its high importance for local people. Ethnobotanical knowledge of A. leiocarpa was mostly evenly spread between genders and generations, while it slightly differed between villages. Although local people did not actively protect A. leiocarpa, current local harvesting modes and management resulted in sustainable use. However, ongoing land-use intensifications require adapted management strategies to guarantee the persistence of this important species. Our results provide, in combination with ecological results of our previous study, appropriate management recommendations. Our study emphasizes the importance of ethnobotanical studies on a local scale level in order to develop management strategies that are reliable in the specific area under the specific circumstances.
Article
Theoretical models of allometric scaling provide an important framework for understanding and predicting how and why the morphology and function of organisms vary with scale. However, the predictions of ‘universal’ scaling models for vascular plants do not consider different environments and disturbance types which can reduce the predictive power of these models. One important source of disturbance in tropical regions is the harvesting of non-timber forest products, such as leaves, flowers, resins and barks. In this context, we examine the influence of bark harvesting and different light environments on scaling of the height and diameter of Himatanthus drasticus (Apocynaceae), an economically important tree species harvested by several local communities living in the Brazilian savanna. By considering this species as a model system and using Bayesian regression, we show that bark harvesting modifies tree allometry and that the empirical scaling exponents diverge from the theoretical predictions. In addition, the results of a mechanistic model of tree growth revealed that bark harvesting affects tree height and that this effect varies independently of the light environment. On the other hand, trees with higher bark harvesting levels presented lower height growth rates when compared to trees without bark harvesting or those with<50% of bark harvesting. Our results highlight the importance of including bark harvesting as a source of disturbance that can cause differences between the observed scaling relationships and those predicted by theoretical models. Finally, from the management perspective, we observed that high levels of bark harvesting could compromise the plant height growth of the debarked trees. Therefore, our recommendation for the management of this species is that the previously defined limits of 50% of bark harvesting should be maintained to avoid the negative effects of harvesting on the tree height over time.
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Bark products constitute nearly one third of plant material used in South African traditional medicine. Since the large majority of South Africans make use of traditional health care, bark is fundamental to the traditional pharmacopoeia. In this review we consider the status of bark resources, as reflected by the literature, and highlight the need for multi-disciplinary research to address the lack of available information on plant species used for their bark. The supply of bark to the medicinal plant trade has been rendered non-sustainable, due to increased user populations and reduced indigenous vegetation. Whilst conservation of the South African flora is paramount, natural resources cannot meet the current, nor foreseeable, demand for bark. Alternatives such as tree propagation and cultivation, strategic management and plant part substitution are discussed. Effective implementation of these action plans is reliant on the dissemination of existing and new knowledge. The prevailing scenario of a non-sustainable bark supply has impacted negatively on the quality of bark products available to the consumer, as problems of incorrect identification and purposeful adulteration arise. To facilitate monitoring and standardisation, phytochemical references should be established for bark authentication, and used in conjunction with morphological and anatomical characters for identification in the case of unknown specimens. The importance of bark in South African traditional health care warrants attention from all research sectors to conserve the country’s rich floral heritage, and the integrity of traditional health care.
Technical Report
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ABSTRACT The bark of the montane trees species, Prunus africana is utilised for the treatment of benign prostate hyperplasia, and has a current market value of around $150 million per annum. (Cunningham et al., 1997). Until 1992, the exploitation of Prunus bark was concentrated primarily in Cameroon, Kenya and Madagascar, Tanzania and, to a lesser extent, the Democratic Republic of Congo (ibid.). However, recent reports have indicated that the island of Bioko, Equatorial Guinea is becoming of increasing importance for the supply of Prunus bark to Europe and may become increasingly important as sources of supply from other countries become scarce or are subject to increased regulation. This report presents the findings of a field-based study of the exploitation of Prunus africana on Bioko in the latter part of 1998.
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Rising demand for medicinal plants has led to increased pressure on wild plant populations. This, combined with shrinking habitats, means that many species in South Africa are now facing local extinction. In 1997, a study was initiated to determine the extent of trade in medicinal plants in the South African Lowveld (the low lying plains to the east of the Drakensberg escarpment), and to investigate socio-economic factors influencing trade and resource management. Trade was not as extensive in the Lowveld as in major urban markets such as Durban or the Witwatersrand (Johannesburg and surrounding towns), either in terms of the quantity, number or range of species sold, or the numbers of people relying on the trade for an income. In markets assessed in Mpumalanga Province, 176 species were identified (71% of the vernacular names encountered in the market place), representing 69 plant families. In Limpopo, 70 different species were identified (84% of the vernacular names encountered in the market place), representing 40 families. Imports were significant in Mpumalanga (33% of the plants on offer), mainly from Mozambique. A detrended correspondence analysis showed substantial differences between species traded in Mpumalanga and those sold in Limpopo. There was little variation in the species stocked by vendors in Mpumalanga, regardless of the season, the attributes of the seller, or whether business was carried out in urban or rural areas. In contrast, there was considerable variation in the stock inventories of the Limpopo traders. Despite the lower levels of local trade, increased harvesting pressure is being experienced regionally, to meet demand in metropolitan centres such as the Witwatersrand. This study showed considerable local variation and complexities in the harvesting and marketing of medicinal plants, with both a national and an international dimension. This dual spatial scale presents both opportunities and challenges in the management of these plants, which need to be addressed simultaneously, particularly with respect to research requirements and development of predictive models and capacity. Cooperation in conservation strategies and policies is required at regional, national and international levels, while ensuring that management initiatives take into account local market conditions and the socio-economic realities facing both consumers and those who depend on the trade for their livelihoods.
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The sprouting response types of 1,151 cork oak (Quercus suber) trees one and half years after a wildfire in southern Portugal were character-ised. It was hypothesised that different response types should occur according to the following conceptual model: an increased level of damage (fire severity) on a sprouting tree that suffered a crown fire was expected to be reflected in a sequence of four alternative events, namely (a) resprouting exclusively from crown, (b) simultaneous resprouting from crown and base, (c) resprouting exclusively from base and (d) plant death. To assess whether the level of expected damage was influenced by the level of protection from disturbance, we explored the rela-tionships between response types and tree size, bark thickness and cork stripping, using an information-theoretic approach. The more common response type was crown resprouting (68.8% of the trees), followed by plant death (15.8%), simultaneous resprouting from crown and base (10.1%) and basal resprouting (5.3%). In agreement with the conceptual model, trees which probably suffered a higher level of damage by fire (larger trees with thinner bark; exploited for cork) died or resprouted exclusively from base. On the other hand, trees that were well protected (smaller trees with thicker bark not exploited for cork) were able to rebuild their canopy through crown resprouting. Simultaneous resprouting from the crown and base was determined mainly by tree size, and it was more common in smaller trees.
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Himalayan medicinal plants are threatened by large scale exploitation for trade. Research applicable to their sustainable use is largely lacking. We analyze the effects of different harvesting patterns on the population ecology of two highly threatened Himalayan medicinal plants, Nardostachys grandiflora (Valerianaceae) and Neopicrorhiza scrophulariiflora (Scrophulariaceae), in Shey-Phoksundo National Park and in its buffer zone in northwestern Nepal. We first documented local harvesting approaches of two major user groups, amchi (traditional doctors trained in Tibetan medicine), who harvest plants in a selective manner for local health care purposes, and commercial collectors, who harvest unselectively and at much higher intensity for trade. We then applied the selective harvesting approach of amchi in an experiment to test the effects of different harvesting levels on the population ecology of these two species. These experiments revealed a positive effect of low harvesting levels on plant density, but recruitment and survival rates decreased with increasing harvesting levels. We also analyzed the effect of high harvesting pressure for trade on the population ecology of N. grandiflora. Recruitment and survival rates were higher in N. scrophulariiflora than in N. grandiflora; the latter species is more vulnerable to harvesting than the former. The difference between them in sustainability of harvest is related to differences in their strategies of vegetative reproduction and in harvesting practices associated with these strategies. Management of Himalayan medicinal plants can be improved by taking harvesting patterns, plant life forms and growth patterns into consideration.
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Bark products constitute nearly one third of plant material used in South African traditional medicine. Since the large majority of South Africans make use of traditional health care, bark is fundamental to the traditional pharmacopoeia. In this review we consider the status of bark resources, as reflected by the literature, and highlight the need for multi-disciplinary research to address the lack of available information on plant species used for their bark. The supply of bark to the medicinal plant trade has been rendered non-sustainable, due to increased user populations and reduced indigenous vegetation. Whilst conservation of the South African flora is paramount, natural resources cannot meet the current, nor foreseeable, demand for bark. Alternatives such as tree propagation and cultivation, strategic management and plant part substitution are discussed. Effective implementation of these action plans is reliant on the dissemination of existing and new knowledge. The prevailing scenario of a non-sustainable bark supply has impacted negatively on the quality of bark products available to the consumer, as problems of incorrect identification and purposeful adulteration arise. To facilitate monitoring and standardisation, phytochemical references should be established for bark authentication, and used in conjunction with morphological and anatomical characters for identification in the case of unknown specimens. The importance of bark in South African traditional health care warrants attention from all research sectors to conserve the country's rich floral heritage, and the integrity of traditional health care.
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Demography, phenology and experimental harvesting of the fern Rumohra adiantiformis (G. Forst.) Ching were studied as a basis of sustained commercial frond harvesting from indigenous forest. The fern grows densely and produces large fronds on moist, well-drained sites. Numbers of frond buds peak during spring, and mature utilizable fronds in late summer. Growth rates for frond development stages varied with season. The period from the bud stage to mature utilizable fronds averaged 16weeks. The mature stage lasted 10–18 weeks during summer. Picking of all mature fronds on a 22-week cycle over 3years reduced frond size to 51% of the controls and on a 4,3-week cycle to 24%. Density of buds and mature fronds was significantly reduced by picking. Reduced frond size and density, and production of malformed fronds are attributed to depletion of the potassium and phosphorous reserves in the plant. Decreased harvest intensity, longer harvest cycle, improved monitoring and future research are recommended for better resource conservation. Guidelines are provided for cultivation of the fern.
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The formation of tyloses in vessels of Ro­ processed for transmi ssion electron micro­ binia p seudoacaci a L. after wounding was scopy, so that the outermost growth ring could investigated by transmission electron micro­ be investigated. scopy . Some tyloses in earlywood vessel s exhibit cell division. The young walls between Results mother and dau ghter tyloses with primary Wound-associated tyloses frequently oc­ wall-like appearance evince plasmodesmata : curred in earlywood vessels of the current pits develop simultaneously with wall thick­ growth ring within I week after wound ing. enin g. The intensity of tylosis formation depends on Key words : Robini a pseudoacacia, tyloses, the distance to the wound with only few tylos­ wounding. electron microscopy . es up to about 5 mm and a higher number up to 20 mm below the wound after 4 weeks. Most of the vessels in the more distant reac­ Introduction tion zone appear entirely occluded. Fine structural analyses on tylosis for­ Individnal tyloses develop by the protru­ ma tion have mainly been focused on initial sion of the parenchyma/ vessel pit membran e stages , i.e . protrusion from the parenchyma into the vessel lumen; simultaneously with cell into the vessel (Meyer 1967; Koran & modification, stretching, and final disin tegra­ Cote 1964 . 1965; Shib ata et al. 1980, 1981, tion of the pit membr ane the primary tylosis 1982; Van del' Molen et a1. 1987), and on their wall is formed. The subsequent enlarge ment wall archi tecture (Fos ter 1967; Sachs et al. of the rylosis bud is mainly related to the in­ 1970 ; Murm anis 1975 ; Parameswaran et al. crease of the volume of its vacuole; the cyto­ 1985). The investigations were concerned plasm becomes closely appressed to the cell with both natural tyloses due to agein g and wall. A nucleus and plastids with a large starch with artificially induced tylo ses. Wounding grain are then located in the young tyloses as an artificial cause generates vessel oc­ (Fig. I). With increa sing number of tyloses clusi ons by tyloses against the penetrati on of per vessel member. some of them exhibit di­ air and micro organisms. Thi s note describe s vision (Figs . 2 and 3). Th e initial cell-plate the formation of wound tyloses in tbe outer­ formation is indicared by the accumulation of most earlyw ood vesse ls of Robinia ps eudo­ numerous vesicles in the equatorial plane (Fig. a£·acia. 4). With time the cell-plate extends L aterally towards the wall of the mother cell. The new Materials and Methods wall resemble s a primary wall with loosely Bran ches (3-5 em in diameter) of Robi­ packed fibrils (Fig. 5). Plasmodesmata are nia pseudoacacia L. were wounded in June present (Fig. 6). The wall thick ens by incor­ 1992 perpendicular to the axis up to a maxi­ poration of material transporte d by dietyo ­ mum depth of I em (tor details see Schmitt some-derived vesicles. Prim ary pit fields & Lie se 1990). Af ter a response time from between mother and daugh ter cell develop 2 days to 4 weeks, small xylem parts up to simultaneously with secondary wall thicken­ 2 cm below the wound cut were dissected and ing (Fig. 7).
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lillp:l/www.oihitiilisclicii~lei,io~~r~~nl~lSIo~~ a by Urban & Fischer Verlag The formation of a ligno-suberised layer and necrophylactic periderm in beech bark (Fagus sylvatica L.) Summary Bccch (Ffiglrs ,sy/l,riricri L.) hark was wounded in early April of 1993 and tissue changes followed on days 7,. In 7 days, tissuc at the wouiid surPacc bccelne necrotic and discoloitred. In 14 days the walls of the parelichyma cclls i~nmediatcly underneath the necrotic tissuc bccanic tllickcncd and aflcr 21 days bccamc lignified. In 28 days thcsc lig~iificd cclls showed inlracellular subedsatioli. In 42 days the ligno-suberised laycr was coolinuoits willi the phellcm of the superficial periderm. In 35 days we first ]noted differentiation of tlie tiecropliyl:~clic phcllogcn untler the ligno-suberiscd laycr. In 49 days sitberised plicllcm of the necrophylactic perider~i~ dilTcrcnliatcd. At I12 days the pliellern of the nccropl~ylactic peridenn had coalesced witli that of the surf;lce periderm. In I40 days ahscissiot~ of the wou~ld rhytidomc began. The formation of a ligno-suhcrised layer and the necrop11yl;tctic periderm started in tlie nonconducting phloetn under the basal region of the wound and proceeded from there in two dircctioos: toward tlie tissue under the original periderm and along tlic sclerified rays toward the cambium. Sclcrificd phloe111 rays protruding inlo the xylem rays did not prevent the ihrmation of a ligno-suberised layer and oecropiiylactic periderm i i i hcech. 11 is supposcd tliitt the ligno-subcrised lnycr and llic necrophylactic periderm in Europcan bcech is generated fmol living cclls extali1 at the lime of wounding as well as from rccctit phloic deriva-tives of the vascular cambiuti~.
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Beech (Fagus sylvatica L.) bark was wounded in early April of 1993 and tissue changes followed on days 7, 14, 21, 28, 35, 42, 49, 56, 84, 112, and 140. In 7 days, tissue at the wound surface became necrotic and discoloured. In 14 days the walls of the parenchyma cells immediately underneath the necrotic tissue became thickened and after 21 days became lignified. In 28 days these lignified cells showed intracellular suberisation. In 42 days the ligno-suberised layer was continuous with the phellem of the superficial periderm. In 35 days we first noted differentiation of the necrophylactic phellogen under the ligno-suberised layer. In 49 days suberised phellem of the necrophylactic periderm differentiated. At 112 days the phellem of the necrophylactic periderm had coalesced with that of the surface periderm. In 140 days abscission of the wound rhytidome began.
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The bark of five healthy and six declining silver firs (Abies alba Mill.) was artficially wounded in July 1991. Structural changes were observed 6, 9, 16,23, and 40 days later. After 6-9 days, there was necrosis and deposition of polyphenols in the exposed tissues. Hypertrophy of the axial and ray parenchyma, and hyperplasia of the rays resulted in the formation of a parenchymatic zone below the necrotic tissues. The outermost cells of this zone just below the necrotic tissues exhibited thickening of walls and lignification in the corners of individual cells. Except in two apparently healthy trees and one strongly declining test tree, intracellular suberin was detectable in some lignified cells by day 16. By then polyphenols were visible in the axial parenchyma cells underneath the parenchymatic zone. Between 23 and 40 days after wounding, progressive suberisation resulted in the formation of a 'ligno-suberised zone', which fused with the phellem of the pre-existing periderm. By day 23, initiation of a new phellogen internal to the 'Iigno-suberised zone' was observed. By the end of the experiment, the necrophylac