Performance of seedlings of the invasive alien tree Schinus molle L. under indigenous and alien host trees in semi-arid savanna

We assessed the importance of host trees in influencing invasion patterns of the alien tree Schinus molle L. (Anacardiaceae) in semi-arid savanna in South Africa. Recruitment of S. molle is dependent on trees in its invaded habitat, particularly Acacia tortilis Hayne. Another leguminous tree, the invasive alien mesquite (Prosopis sp.), has become common in the area recently, but S. molle rarely recruits under canopies of this species. Understanding of the association between these species is needed to predict invasion dynamics in the region. We conducted experiments to test whether: (i) seedling survival of S. molle is better beneath A. tortilis than beneath mesquite canopies; (ii) growth rates of S. molle seedlings are higher beneath A. tortilis than beneath mesquite. Results showed that growth and survival of S. molle did not differ significantly beneath the native A. tortilis and the alien Prosopis species. This suggests that microsites provided by canopies of mesquite are as good for S. molle establishment as those provided by the native acacia. Other factors, such as the failure of propagules to arrive beneath mesquite trees, must be sought to explain the lack of recruitment beneath mesquite.Centre of Excellence for Invasion Biolog

Beyond timber: balancing demands for tree resources between concessionaires and villagers

Extensive areas of the Congo Basin forest are allocated to timber concessionaires. These forests also harbour and support village populations, including indigenous Baka people, who depend on forest foods obtained directly from trees (fruits, oils and caterpillars). Most food-producing tree species are harvested by concessionaires for timber. We documented the availability and abundance of three food tree species around four villages and in two neighboring timber concessions in Cameroon. Data was used to determine the importance of timber concessions as sources of food for local people to provide a foundation for governance arrangements that consider local needs for foods from timber trees. Discussions with concessionaires revealed that some of them have voluntarily refrained from extracting timber species of interest to villagers for their nontimber products. This is either to avoid conflict with villagers, or because regulations have been promulgated to safeguard these resources. The interplay between internal village dynamics, regulations and their implementation by forest guards, and the actions of timber concessions create a complex arena for addressing rights to forest resources. This paper provides information on the accessibility and availability of multiple use timber species as a foundation for negotiations and governance arrangements between concessionaires and local communities

Seed set of the invasive tree Schinus molle (Anacardiaceae) in semi-arid savanna, South Africa: The role of pollinators and selfing

This study investigates the extent to which seed production in Schinus molle is dependent upon pollinators and outcrossing with the objective of understanding whether pollination and seed set could be a barrier to the spread of S. molle in arid savannas of South Africa. Pollination experiments demonstrated that seed set was greater in female flowers exposed to natural pollinators than in those from which pollinators were excluded. However, the fact that a few seeds were also found in treatments protected from pollinators and not treated with pollen may indicate that some S. molle flowers might be bisexual and capable of self-pollination. The results suggest that S. molle fruit set is mainly affected by insect pollination, but there is also the possibility of self-pollination and apomixis. © 2009 Elsevier Ltd. All rights reserved.Articl

Soil type, microsite, and herbivory influence growth and survival of Schinus molle (Peruvian pepper tree) invading semi-arid African savanna

Naturalization of Schinus molle (Anacardiaceae) has been observed in semi arid savanna of the Northern Cape Province of South Africa. However, with high dispersal ability, the species is expected to achieve greater densities and invade more widely. The study involved a field manipulation experiment over 14 months using a factorial block design to examine transplanted seedlings in different savanna environments. The experiments examine the effects of soil type (sandy and clay), microsite, and herbivores on seedling performance (establishment, growth and survival). Seedlings were grown in a greenhouse and individually transplanted into four treatment groups: in open grassland, under tree canopies, and with and without cages to exclude large herbivores (cattle and game). The same experiment was repeated in two different soil types: coarse sand and fine-textured clay soil. Results suggest that protection provided by canopies of large indigenous Acacia trees facilitates S. molle invasion into semi-arid savanna. In the field, S. molle seedlings performed considerably better beneath canopies of indigenous Acacia trees than in open areas regardless of soil type. Whether exposed or protected from large herbivores, no seedlings planted in open grassland survived the first winter. Although, seedlings grew better and had higher survival rates beneath tree canopies than in the open sites, exposure to large herbivores significantly decreased heights and canopy areas of seedlings compared with those protected from large herbivores. The effect was greater on clay soil than on sandy soil. The results suggest that low temperature (frost), and possibly inter-specific competition with grasses, may limit S. molle seedling establishment, survival and growth away from tree canopies in semi arid savannas. Low soil nutrient status and browsing may also delay growth and development of this species. The invasive potential of S. molle is thus greatest on fertile soils where sub-canopy microsites are present and browsing mammals are absent. © 2008 Springer Science+Business Media B.V.Articl

Performance of seedlings of the invasive alien tree Schinus molle L. under indigenous and alien host trees in semi-arid savanna

We assessed the importance of host trees in influencing invasion patterns of the alien tree Schinus molle L. (Anacardiaceae) in semi-arid savanna in South Africa. Recruitment of S. molle is dependent on trees in its invaded habitat, particularly Acacia tortilis Hayne. Another leguminous tree, the invasive alien mesquite (Prosopis sp.), has become common in the area recently, but S. molle rarely recruits under canopies of this species. Understanding of the association between these species is needed to predict invasion dynamics in the region. We conducted experiments to test whether: (i) seedling survival of S. molle is better beneath A. tortilis than beneath mesquite canopies; (ii) growth rates of S. molle seedlings are higher beneath A. tortilis than beneath mesquite. Results showed that growth and survival of S. molle did not differ significantly beneath the native A. tortilis and the alien Prosopis species. This suggests that microsites provided by canopies of mesquite are as good for S. molle establishment as those provided by the native acacia. Other factors, such as the failure of propagules to arrive beneath mesquite trees, must be sought to explain the lack of recruitment beneath mesquite. © 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd.Articl

Contemporary wild meat hunting, consumption, and trade in Africa

Guest editorial for special issu

Livelihoods, economic contribution and sustainability of the bush mango (Irvingia gabonensis) value chain from three provinces of Gabon

In the Congo Basin, the economic, social and environmental value of non-timber forest products (NTFPs), such as bush mango (Irvingia gabonensis) is widely acknowledged. However, knowledge of the volumes traded, extent and distribution of revenues along the value chain is limited while little is known about the chain's sustainability. The survey of the value chain was followed by field observations and semi structured interviews with 174 stakeholders in Estuaire, Nyanga and Ngounié provinces of Gabon. Women dominate in the bush mango value chain. Most bush mango sold in urban and rural markets came from neighbouring countries. There is skewed distribution of revenues, with traders and processors earning higher incomes than harvesters. Deforestation, lack of harvesting standards and poor management of resources, according to the stakeholders, represent the main factors threatening the sustainability of the chain. Long-term socio-economic and environmental sustainability of the chain calls for raising the political visibility of the chain, training and collective action