Orou G. Gaoue

Fulani Knowledge of the Ecological Impacts of Khaya senegalensis (Meliaceae) Foliage Harvest in Benin and its Implications for Sustainable Harvest

Fulani Knowledge of the Ecological Impacts ofKhaya senegalensis(Meliaceae) Foliage Harvest in Benin and Its Implications for Sustainable Harvest. An improved understanding of how local people view their impacts on the resources they exploit and how they perceive that their resources are affected by other factors can provide insight into reasons some resources are overexploited and into strategies to conserve them. In West Africa, various tree species are heavily harvested by indigenous herders for foliage to feed their cattle. The reported declines in populations of several of these species have both biological and cultural implications, as cattle are an integral part of indigenous cultures and livelihoods. In this study we investigated Fulani herders’ practices, knowledge, and perceptions of the ecological impacts of harvesting foliage of African mahogany, Khaya senegalensis, in Benin, and we tested some of the factors that may influence them. Fulani herders have detailed ecological knowledge of their impacts on the resources they depend on, and this is finely tuned to local ecological conditions. This knowledge is also widely spread across different sectors of Fulani communities and is highly congruent with scientific findings. However, due to the open-access context of K. senegalensis populations, detailed knowledge of sustainability does not translate into sustainable practices. Fulani perceptions of threats to populations differ significantly between ecological regions and provide key insights for locally relevant resource management plans. Traditional Fulani practices such as the sopoodu provide a basis for sustainable management of proposed Fulani-owned K. senegalensis plantations. This study illustrates how the assessment of local ecological knowledge, practices, and perceptions can play a key role in the design of culturally-appropriate conservation plans.

Dendrometric characteristics as indicators of pressure of Afzelia africana Sm. dynamic changes in trees found in different climatic zones of Benin

Afzelia africana is a forest species used by local inhabitants for various purposes, especially as forage to feed cattle, as medicinal plant and its wood is used to make furniture or for cooking. Its utilisation in its current form constitutes a threat to this species. However, the lack of data on this species is a hindrance towards drawing up an efficient program for its sustainable management. In order to fill in some gaps in the knowledge of A. africana tree populations, dendrometric characteristics of this species were studied within different climatic zones where it occurs in Benin. Data collected on each of them included height and diameter, and with regard to the levels of pressure, five categories were defined namely: null, weak, moderate, severe and very severe. As far as diameter is concerned every size was taken into consideration in all the climatic zones. However, average diameter and height of the A. africana individuals varied significantly according to climatic zones. Anthropogenic pressure increased while moving from the humid zone towards the drier zone. Moreover, there was a noticeable significant change in the level and quality of pressure between trees found in the different climatic zones in the sense that the lower the height of the trees, the more severe the level of pressure exerted. Such a relationship was not significant when one considers tree diameter in accordance with the climatic zones in the country.

Effects of Harvest of Nontimber Forest Products and Ecological Differences between Sites on the Demography of African Mahogany

The demographic impacts of harvesting nontimber forest products (NTFP) have been increasingly studied because of reports of potentially unsustainable harvest. Nevertheless, our understanding of how plant demographic response to harvest is altered by variation in ecological conditions, which is critical for developing realistic sustainable-use plans, is limited. We built matrix population models to test whether and how variation in ecological conditions affects population responses to harvest. In particular, we examined the effect of bark and foliage harvest on the demography of populations of African mahogany (Khaya senegalensis) in two contrasting ecological regions of Benin, West Africa. K. senegalensis bark and foliage harvest significantly reduced its stochastic population growth rates, but ecological differences between regions had a greater effect on population growth rates than did harvest. The effect of harvest on population growth rates (Deltalambda) was slightly stronger in the moist than in the drier region. Life-table response experiments revealed that the mechanism by which harvesting reduced lambda differed between ecological regions. Lowered stasis (persistence) of larger life stages lead to a reduction in lambda in the drier region, whereas lowered growth of all life stages lowered lambda in moist region. Potential strategies to increase population growth rates should include decreasing the proportion of individuals harvested, promoting harvester-owned plantations of African mahogany, and increasing survival and growth by promoting no-fire zones in gallery forests. Our results show how population responses to harvest of NTFP may be altered by ecological differences across sites and emphasize the importance of monitoring populations over the climatic range in which they occur to develop more realistic recommendations for conservation.

Defoliation and bark harvesting affect life-history traits of a tropical tree.

Summary 1. Selectively harvesting whole individuals in managed populations (e.g. fisheries, hunting) has substantial effects on life expectancy and age at maturity. Although demographic rates of trees are impacted by recurrent harvest of plant organs (e.g. fruit, leaf, bark) known as non-timber forest products, the effect of such harvesting on life-history traits is less explored. 2. Here, we investigate how different strategies of foliage and bark harvest by local people affect life expectancy and age at maturity of Khaya senegalensis across two climatic regions in West Africa. We compare elasticities of life expectancy to perturbation of vital rates to the elasticities of population growth rate, emphasizing how the two kinds of elasticity address distinct biological issues and management goals. 3. Life expectancy was shorter and reproduction delayed in the dry than in the moist region, indicating a cost of drought to life-history traits. Harvesting at constant rates only affects (increased) life expectancy in the moist region and (reduced) age at first reproduction in the dry region. 4. Models in which harvest intensity varies stochastically over time show results similar to those with constant harvesting rate. However, there is an interactive effect of harvest on life-history traits between regions. Increasing harvesting pressure accelerates maturity and reduces life expectancy in the dry region but delays reproduction and increases life expectancy in the moist region. This indicates that stochasticity magnifies the effect of harvesting on life-history traits. 5. With the notable exception of heavily harvested populations in the moist region, life expectancy is more elastic to survival of early rather than late life stages. This pattern contrasts with the elasticity of population growth rate; the latter is more elastic to survival of late rather than early life stages. 6. Synthesis. Our results suggest that plant harvesting can affect life-history traits but in different ways across an environmental gradient. Failure to account for stochasticity in harvesting rate can mask some of these effects. Our results also indicate that processes driving plant life expectancy, at least for long-lived species, may differ from those driving population dynamics.

Non‐timber forest product harvest in variable environments: modeling the effect of harvesting as a stochastic sequence

With increasing reports of overexploitation of wild plants for timber and non-timber forest products, there has been an increase in the number of studies investigating the effect of harvest on the dynamics of harvested populations. However, most studies have failed to account for temporal and spatial variability in the ecological conditions in which these species occur, as well as variability in the patterns of harvest intensity. In reality, local harvesters harvest at variable rather than fixed intensity over time. Here we used Markov chains to investigate how different patterns of harvesting intensity (summarized as return time to high harvest) affected the stochastic population growth rate (lambda(s)) and its elasticity to perturbation of means and variances of vital rates. We studied the effect of bark and foliage harvest from African mahogany Khaya senegalensis in two contrasting ecological regions in Benin. Khaya populations declined regardless of time between harvests of high intensity. Moreover, lambda(s) increased with decreasing harvesting pressure in the dry region but, surprisingly, declined in the moist region toward lambda(s) = 0.956. The stochastic elasticity was dominated by the stasis of juveniles and adults. The declining growth rate with decreasing harvest pressure in the moist region was mainly driven by the declining mean survival rates of juveniles and adults. Our results suggest that modeling the temporal variability of harvest intensity as a Markov chain better mimics local practices and provides insights that are missed when temporal variability in harvest intensity is modeled as independent over time and drawn from a fixed distribution.

Theories and Major Hypotheses in Ethnobotany

Ethnobotany has evolved from a discipline that largely documented the diversity of plant use by local people to one focused on understanding how and why people select plants for a wide range of uses. This progress has been in response to a repeated call for theory-inspired and hypothesis-driven research to improve the rigor of the discipline. Despite improvements, recent ethnobotanical research has overemphasized the use of quantitative ethnobotany indices and statistical methods borrowed from ecology, yet underemphasized the development and integration of a strong theoretical foundation. To advance the field of ethnobotany as a hypothesis-driven, theoretically inspired discipline, it is important to first synthesize the existing theoretical lines of research. We review and discuss 17 major theories and hypotheses in ethnobotany that can be used as a starting point for developing research questions that advance our understanding of people–plant interactions. For each theory or major hypothesis, we identify its primary predictions and testable hypotheses and then discuss how these predictions have been tested. Developing research to test these predictions will make significant contributions to the field of ethnobotany and create the critical mass of primary literature necessary to develop meta-analyses and to advance new theories in ethnobotany.

Transient dynamics reveal the importance of early life survival to the response of a tropical tree to harvest

Summary 1. Exploitation of non-timber forest products can contribute to the alleviation of poverty. However, overexploitation can also lead to species decline. Studies on the sustainability of harvest often use stationary population growth rates to assess harvesting effects. For such frequently harvested systems, transient analysis can provide new insights into the response of populations to harvest. 2. To test the prediction that the effect of harvest differs between transient and asymptotic phases, I used four years of demographic data to compare the impact of harvesting bark and foliage on the short- and long-term dynamics of African dry zone Mahogany Khaya senegalensis in West Africa. 3. The effect of harvest was stronger in the short term than in the long term, particularly in the moist region. Patterns of transient elasticities also differed from the elasticities of longterm growth rates to perturbation of vital rates. Survival at early life stages was more important for short-term dynamics than for long-term population dynamics. 4. Synthesis and applications. This study illustrates that using the asymptotic growth rates to assess the impact of harvest may underestimate the short-term effects of harvest. Short-term management plans based on the elasticity analysis of long-term growth rates will be suboptimal given the relative importance of the survival of non-reproductive stages for population dynamics in the near term. Managers should use results from elasticity analysis of both longterm and short-term population dynamics to develop more realistic management plans.

Defoliation by pastoralists affects savanna tree seedling dynamics by limiting the facilitative role of canopy cover

Recurrent tree defoliation by pastoralists, akin to herbivory, can negatively affect plant reproduction and population dynamics. However, our understanding of the indirect role of defoliation in seedling recruitment and tree-grass dynamics in tropical savanna is limited. In West African savanna, Fulani pastoralists frequently defoliate several fodder tree species to feed livestock in the dry season. We investigated the direct and indirect effects of recurrent defoliation of African mahogany (Khaya senegalensis) by Fulani people on seedling (< 2 cm basal diameter) and sapling dynamics in West Africa using four years of demographic data on seedling and sapling density, growth, and survival, coupled with fruit production and microhabitat data over the same time period. Tree canopy cover facilitated seedlings but had negative effects on sapling growth possibly via intraspecific competition with adult plants. Interspecific competition with grasses strongly reduced seedling survival but had a weak effect on sapling growth. Fire reduced seedling survival and weakly reduced growth of seedlings and saplings, but did not affect sapling survival. These results indicate that the effect of fire on seedlings and saplings is distinct, a mechanism suitable for an episodic recruitment of seedlings into the sapling stage and consistent with predictions from the demographic bottleneck model. Defoliation affected seedling density and sapling growth through changes in canopy cover, but had no effect on seedling growth and sapling survival. In the moist region, sapling density was higher in sites with low-intensity defoliation, indicating that defoliation may strengthen the tree recruitment bottleneck. Our study suggests that large-scale defoliation can alter the facilitative role of nurse trees on seedling dynamics and tree-sapling competition. Given that tree defoliation by local people is a widespread activity throughout savanna-forest systems in West Africa, it has the potential to affect tree-grass coexistence. Incorporating the influence of large tree defoliation into existing models of savanna dynamics can further our understanding of tree-grass coexistence and improve management. A rotating harvest system, which allows seedlings to recruit episodically, or a patchwork harvest, which maintains some nursery trees in the mosaic, could help sustain seedling recruitment and minimize the indirect effects of harvest.

Microsatellites for mahoganies: Twelve new loci for Swietenia macrophylla and its high transferability to Khaya senegalensis

PREMISE OF THE STUDY A new set of 12 microsatellite markers was developed and characterized for big-leaf mahogany (Swietenia macrophylla King, Meliaceae) and its transferability assayed in the African mahogany, Khaya senegalensis (Desr.) A. Juss. (Meliaceae), to study population and conservation genetics of these threatened tropical timber species. METHODS AND RESULTS Using an enriched library approach twelve novel microsatellite loci were identified for S. macrophylla. The number of alleles per locus ranged from 5 to 14 and mean observed and expected heterozygosities were 0.819 and 0.822, respectively. Twenty microsatellite loci developed for S. macrophylla (12 from this study and eight previously published) were tested for K. senegalensis and 10 polymorphic were characterized. CONCLUSIONS The results show the highly informative content of the new SSR loci for Swietenia macrophylla and the high effectiveness of these microsatellites for population genetics, gene flow, and mating system studies in Khaya senegalensis.

Towards a mechanistic understanding of the synergistic effects of harvesting timber and non‐timber forest products

Summary Classic theories of resource harvest assume logistic growth and incorporate harvest through an additional loss term. This methodology has been applied successfully in forest products harvesting such as timber logging. However, modelling harvest through a loss term is not appropriate for non-timber forest products (NTFP) since harvesting in this case does not always require the complete removal of individual plants. Empirical evidence suggest that NTFP harvest affects plant population growth rates. Additionally, timber and NTFP harvest can have synergistic effects on population dynamics. We develop and analyse a simple model that incorporates non-lethal harvest implicitly through the population growth rate of plants and lethal harvest explicitly through permanent removal of whole plants, with additional synergistic effects on population growth rate. To capture transient dynamics, we model the growth rate of plants explicitly as a dynamic variable affected by harvesting. Transient dynamics results indicate that populations have delayed response to discrete harvesting. We demonstrate exactly how the sustainability of lethal harvest, non-lethal harvest or both types of harvests depends on the demographic effect of each type of harvest on the population growth rate. Finally, we identify a threshold parameter , such that combined lethal and non-lethal harvest results in plant population sustainability when 1 and extinction when 1.