Strong seedling recruitment does not limit mangrove vulnerability to harvest

Ecological studies on the impacts of timber harvesting contributed to inform sustainable management strategies of tropical forests. However, these studies rely strongly on two major assumptions: (i) strong seedlings recruitment predispose for positive population dynamics, and (ii) more adult trees is a guarantee for a strong reproductive capability of the population. These assumptions are applied without accounting for the life history of the harvested species. Here, we revisit these assumptions in light of the life history theory, which predicts different responses of short- and long-lived species to perturbation. We predict that harvesting adults, rather than reducing seedling recruitment of long-lived species, would have greater impact on population dynamics. We tested our prediction on three mangrove species in South Africa. First, we reconstructed the projection matrices for three mangrove species in the Mngazana Estuary of Eastern Cape province of South Africa. Next, we simulated a range of harvest intensities for different life stages and explored how harvesting influences population dynamics. Finally, we examined the age-specific mortality trajectories for all three species. We found that populations of all three species were closer to their stable stage distribution. Contrary to popular belief, we found that changes in seedling recruitment will have minimal effects on mangrove long-term population dynamics, a finding consistent with the life history theory. However, contrary to expectation, simulating harvest of adults had minimal effect on population dynamics. This is due to low reproductive values for these late stages. Our analysis of age-specific mortality trajectories further provided evidence for positive senescence particularly for Avicennia which was the least resilient to harvest. Our findings cast doubt on the traditional forest management strategies that rely strongly on seedling density as a metric of sustainability and forbid unquestionably harvesting large individuals. We call for caution while generalizing forest management strategies irrespective of the life history of the species at hand

Social-ecological alignment and ecological conditions in coral reefs

Complex social-ecological interactions underpin many environmental problems. To help capture this complexity, we advance an interdisciplinary network modeling framework to identify important relationships between people and nature that can influence environmental conditions. Drawing on comprehensive social and ecological data from five coral reef fishing communities in Kenya; including interviews with 648 fishers, underwater visual census data of reef ecosystem condition, and time-series landings data; we show that positive ecological conditions are associated with ‘social-ecological network closure’ – i.e., fully linked and thus closed network structures between social actors and ecological resources. Our results suggest that when fishers facing common dilemmas form cooperative communication ties with direct resource competitors, they may achieve positive gains in reef fish biomass and functional richness. Our work provides key empirical insight to a growing body of research on social-ecological alignment, and helps to advance an integrative framework that can be applied empirically in different social-ecological contexts

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

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. 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. 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 long-term 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. 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 long-term and short-term population dynamics to develop more realistic management plans

Khaya_MeanMatrices_2004_2007

This file includes mean matrices for 12 populations of Khaya senegalensis surveyed in Benin (West Africa) from 2004 to 2007. For each population, I averaged three yearly transition matrices (2004-2005, 2005-2006, 2006-2007). These matrices were built using demographic data was collected from the 12 populations using 1-ha plots for each population (two adjacent subplots of 0.5 ha, separated by the river bed when the population was in a gallery forest

Plant Diversity Increased Arthropod Diversity and Crop Yield in Traditional Agroforestry Systems but Has No Effect on Herbivory

Improving agricultural production in response to the increasing food demand remains a major challenge in agroecology. The world has made significant efforts to meet this issue by developing several cultivation techniques, such as the use of chemical fertilizers and arable land conversion into agricultural land. However, most of these techniques have caused a significant loss of biodiversity and ecosystems services. Recent data suggest that biological conservation within and around agroforestry systems are potential solutions that can both reduce biodiversity loss and guarantee crop production. This logic is based on the hypothesis that increasing plant diversity in and around agricultural systems can limit the pest attack rate and increase crop yield. We tested this hypothesis using structural equation modeling on empirical data collected in agroforestry systems around the Pendjari biosphere reserve in West Africa. We measured crop diversity, crop yield, arthropod pest diversity, abundance, the rate of crop herbivory, and the diversity of plants in surrounding natural vegetation in 32 permanent plots. We estimated arthropod diversity and abundance using pitfall traps. We found a direct positive effect for plant diversity and a direct negative effect of arthropod herbivory on crop yield. The diversity of plants in surrounding natural vegetation had a direct positive effect on arthropod pest diversity but a marginal negative direct effect on the rate of crop herbivory. We found no significant direct or indirect effect for crop diversity. Our findings underline the important role of biodiversity conservation in agricultural production improvement. We suggest that the conservation of plant diversity around agroforestry systems may be an effective option to control herbivory damage. Its combination with other pest control techniques may further limit crop depredation and ensure the long-term conservation of wildlife

Data from: 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

Prestige and homophily predict network structure for social learning of medicinal plant knowledge.

Human subsistence societies have thrived in environmental extremes while maintaining biodiversity through social learning of ecological knowledge, such as techniques to prepare food and medicine from local resources. However, there is limited understanding of which processes shape social learning patterns and configuration in ecological knowledge networks, or how these processes apply to resource management and biological conservation. In this study, we test the hypothesis that the prestige (rarity or exclusivity) of knowledge shapes social learning networks. In addition, we test whether people tend to select who to learn from based on prestige (knowledge or reputation), and homophily (e.g., people of the same age or gender). We used interviews to assess five types of medicinal plant knowledge and how 303 people share this knowledge across four villages in Solomon Islands. We developed exponential random graph models (ERGMs) to test whether hypothesized patterns of knowledge sharing based on prestige and homophily are more common in the observed network than in randomly simulated networks of the same size. We found that prestige predicts five hypothesized network configurations and all three hypothesized learning patterns, while homophily predicts one of three hypothesized network configurations and five of the seven hypothesized learning patterns. These results compare the strength of different prestige and homophily effects on social learning and show how cultural practices such as intermarriage can affect certain aspects of prestige and homophily. By advancing our understanding of how prestige and homophily affect ecological knowledge networks, we identify which social learning patterns have the largest effects on biocultural conservation of ecological knowledge

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 (λλ 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, λλ s increased with decreasing harvesting pressure in the dry region but, surprisingly, declined in the moist region toward λλ 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

<b>A phylogenetic evaluation of non-random medicinal plants selection around an African</b><b> </b><b>biosphere reserve</b>

This contains data to reproduce the analyses from A phylogenetic evaluation of non-random medicinal plants selection around an African biosphere reserve. </p

Cyrtandra_dentata_matrices_2010_2014

This file contains mean transition matrices from 2010–2011, 2011–2012, 2012–2013, and 2013–2014 from a geographically isolated population of a long lived shrub, Cyrtandra dentata, from the Kahanahāiki Management Unit (36 ha), located in the northern Wai‘anae Mountain Range, on the island of O‘ahu (21° 32’ N, -158°12’ W