Katharina Schumann

Impacts of land-use on West African savanna vegetation: a comparison between protected and communal area in Burkina Faso

Biodiversity matters in many aspects for human well-being by providing timber and non-timber products. The most important ecosystems providing these products in West Africa are savannas. In the context of land-use changes, there is an urgent need to understand the impact of land-use on savanna vegetation and biodiversity. This study assesses the impact of land-use on savannas by comparing protected and communal areas. Vegetation relevés were performed in the W National Park and its surrounding communal area in Burkina Faso. Vegetation types were established using ordination and clustering methods. We analyzed to find which environmental factors determine the occurrence of the vegetation types and whether land-use has a specific effect on diversity of vegetation types occurring in both areas. Furthermore, we tested the effect of land-use on vegetation structure and the occurrence of life forms and highly valued tree species. Our results reveal five vegetation types occurring in both areas. Elevation and soil characteristics played the most important role for the occurrence of the vegetation types. Land-use had an effect on vegetation structure, diversity, and the occurrence of life form and highly valued species. Our findings suggest that traditional human land-use does not automatically lead to loss of species and degradation of savanna habitats and that combination of communal and protected areas may be of great importance for the conservation of broad spectrum of biodiversity. Our study demonstrates the complexity of land-use impact on biodiversity patterns and provides insights on what kind of management activities may be most appropriate in both areas.

Uses, management, and population status of the baobab in eastern Burkina Faso

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 intensification, 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 knowledge 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 importance 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 strategies 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.

Human impact on population structure and fruit production of the socio-economically important tree Lannea microcarpa in Burkina Faso

Non-timber forest products (NTFPs) are of high socio-economic value for rural people in West Africa. Main factors determining the status of the populations of socio-economically important tree species providing those NTFPs are human activities. This study assesses the impact of human population density, land use, and NTFP-harvesting (pruning and debarking) on population structure and fruit production of the socio-economically important tree Lannea microcarpa that is normally conserved by farmers on fields. We compared L. microcarpa stands of protected sites with those of their surrounding communal sites in two differently populated areas in Burkina Faso. Our results reveal an opposed land use impact on the population structure of L. microcarpa in the two areas. In the highly populated area, the species population was more stable in the protected site than in the communal site, while the opposite was observed for the less populated area. Trees of the communal sites bore more fruits than trees of the protected sites. Debarking and pruning had a negative impact on fruit production of the species. We conclude that low intensity of human impact is beneficial for the species and that indirect human impact facilitates fruit production of L. microcarpa. In contrast, in the densely populated area, human impact has reached an intensity that negatively affects the populations of L. microcarpa. While the extent of protecting L. microcarpa on fields still seems to be enough to guarantee the persistence of this important species in the less populated area, it is no longer sufficient in the densely populated area.

Effects of climate, habitat and land use on the cover and diversity of the savanna herbaceous layer in Burkina Faso, West Africa

Herbaceous plants account for more than three-fourths of the total biomass in savanna ecosystems. However, which environmental factors mainly drive the biodiversity of herbaceous species is still under debate. In this study, we investigated the influence of climate, habitat and land use on species richness and cover in the West African savanna ecosystems of Burkina Faso. For a broader understanding, we analysed responses of the most important taxonomical groups of the herbaceous layer (Poaceae, Cyperaceae, Fabaceae s.l. and juvenile woody species) to the above mentioned environmental factors. We found light limitation by trees or shrubs and nutrient availability to be the variables that were mainly able to explain the differences in species richness, whereas precipitation and soil water-holding capacity, in general, drive species cover. However, specifically which environmental parameters influenced species richness and cover differed between taxonomical groups. Species richness of Cyperaceae species depended on water availability, while high Cyperaceae cover was found in soils with high water-holding capacity. Cyperaceae species are able to tolerate stagnant water. By contrast, Poaceae species cover was higher in dry habitats, and species richness declined with higher mean annual precipitation. Fabaceae species richness and cover were both higher in communal areas and sandy soils. This study revealed that both species richness and species cover, important aspects to describe the community composition, should be examined, as they are driven by sometimes different environmental conditions. Differentiating between the most important taxonomical groups of the savanna ecosystem increases the understanding in the important ecological processes that effect the herbaceous vegetation composition.

Factors affecting primary succession of glacier foreland vegetation in the European Alps

Vegetation succession on glacier forelands has been well-studied. However, most of the studies investigated only one or few glacier forelands. We studied regional variations in vegetation succession on 16 glacier forelands in the European Alps. To improve our understanding of how vegetation succession is regulated by environmental conditions, we took edaphic and climatic factors into account. We collected vegetation data in three stages (early; middle; late) along a successional gradient on glacier forelands in the Eastern and Western European Alps. The progressions of species richness, vegetation cover and composition during primary succession were compared between these two regions. In addition, the effects of climatic and edaphic factors and grazing were tested. Our results reveal that the vegetation from the early stage did not differ between the regions and different elevations. With progressing time, and especially in the late successional stage, several vegetation differences emerged. The forelands of the Western Alps already developed to open shrubland, while the forelands of the Eastern Alps so far only developed toward grassland. Surprisingly, these differences cannot be explained by different precipitation amounts, but possibly by different regional species pools and elevations of the treelines. We conclude that a complex of edaphic factors closely related to terrain age, regional differences in the species pool, and the different elevation of the treeline in the eastern and western Alps mostly influenced later stages of primary succession on glacier forelands.