Manfred Finckh

Social and ecological constraints on decision making by transhumant pastoralists: a case study from the Moroccan Atlas Mountains

Transhumant pastoralism is an important activity in southern Morocco. Migration pattern of transhumant pastoralists can be affected by physical factors (e.g. droughts and diseases) or socioeconomic factors (e.g. schooling options for children and migration costs). We studied the spatio-temporal rangeland usage of the three tribes Ait Mgoun, Ait Zekri, and Ait Toumert in the south-central Atlas region with a two-fold approach. First, we tracked the migration movements of one representative transhumant herd using the Advanced Research and Global Observation Satellite (ARGOS) collars, which record coordinates from satellite signals. Second, we interviewed herders to obtain information about general grazing practices of the respective tribe and to gain more direct information on motivations underlying decisions. For each tribe we observed small-, medium- and large-scale movements. We found that the most important drivers of migration decisions were seasonal fodder availability and weather conditions in combination with herd-specific risk and cost assessment, as well as personal factors. In conclusion, general migration patterns vary in time, both between and within the tribes, but according to a regulatory framework. Moreover, it appears that both the customary rules and its flexible adaptation to physical constraints are generally beneficial in terms of conservation of the arid and semiarid rangeland resources.

Evaluating the trade-off between food and timber resulting from the conversion of Miombo forests to agricultural land in Angola using multi-temporal Landsat data.

The repopulation of abandoned areas in Angola after 27years of civil war led to a fast and extensive expansion of agricultural fields to meet the rising food demand. Yet, the increase in crop production at the expense of natural resources carries an inherent potential for conflicts since the demand for timber and wood extraction are also supposed to rise. We use the concept of ecosystem services to evaluate the trade-off between food and woody biomass. Our study area is located in central Angola, in the highlands of the upper Okavango catchment. We used Landsat data (spatial resolution: 30×30m) with a bi-temporal and multi-seasonal change detection approach for five time steps between 1989 and 2013 to estimate the conversion area from woodland to agriculture. Overall accuracy is 95%, users accuracy varies from 89-95% and producers accuracy ranges between 92-99%. To quantify the trade-off between woody biomass and the amount of food, this information was combined with indicator values and we furthermore assessed biomass regrowth on fallows. Our results reveal a constant rise in agricultural expansion from 1989-2013 with the mean annual deforestation rate increasing from roughly 5300ha up to about 12,000ha. Overall, 5.6% of the forested areas were converted to agriculture, whereas the FAO states a national deforestation rate for Angola of 5% from 1990-2010 (FAO, 2010). In the last time step 961,000t per year of woodland were cleared to potentially produce 1240t per year of maize. Current global agro-economical projections forecast increasing pressure on tropical dry forests from large-scale agriculture schemes (Gasparri et al., 2015; Searchinger and Heimlich, 2015). Our study underlines the importance of considering subsistence-related change processes, which may contribute significantly to negative effects associated with deforestation and degradation of these forest ecosystems.

Tree Species Diversity and Composition of Miombo Woodlands in South-Central Angola: A Chronosequence of Forest Recovery after Shifting Cultivation

The study was carried out in the Cusseque area of the Municipality of Chitembo in south-central Angola. Our objectives were to assess the floristic diversity, the species composition, and stand structure of Miombo woodlands during regeneration after shifting cultivation. A total of 40 plots of 1000 m2 were surveyed and analyzed, corresponding to mature forests/woodlands and three fallow types of different age. The analyses were based on plot inventories of all trees with DBH ≥ 5 cm. A total of 51 woody species, 38 genera, and 19 families were recorded. The dominant family was Fabaceae, with subfamily Caesalpinioideae being very abundant. Shannon Diversity and Evenness were highest in mature forests and young fallows, while the mature forest stands showed the highest species richness. A Principal Coordinates Analysis (PCoA) showed many species shared between the intermediate fallow types, but only few species were shared with young fallows. Mature forests formed a clearly distinct group. This study shows potential pathways of forest recovery in terms of faster regeneration after agricultural abandonment and, thus, the results presented here can be used in future conservation and management plans in order to reduce the pressure on mature forests.

Impact of Shifting Cultivation on Dense Tropical Woodlands in Southeast Angola

Dry tropical woodlands are the characteristic natural vegetation type of southeast Angola, where precipitation is seasonal and nutrient content of soils is very low. Subsistence farmers overcome the poor abiotic conditions by using shifting cultivation based on specific site selection. We describe the vegetation composition of a previously unstudied dense woodland tract, which is preferred for agriculture, comparing it to nearby open woodland. We placed 25 vegetation plots randomly in the two types of natural woodland vegetation (open and dense) as well as in fallows with three different durations of land use. In each plot the cover of all vascular plant species was recorded. Variables describing vegetation structure, including basal area and leaf area index, were recorded. We analyzed soil samples for texture, pH, conductivity and nutrients, and investigated the impact of land use duration on woodland regeneration. We found that species composition and vegetation structure of the dense woodland differed greatly from the surrounding open woodland. The dense woodland is preferable for agriculture because of its higher soil content of silt, clay and potassium, higher woody biomass, and more abundant soft litter. A longer duration of land use affects species composition and diversity of the regenerating vegetation as well as nutrient content in the soil. In the near future, the increasing demand for agricultural land is likely to change the structure and composition of the dense woodland.

Linking Land Surface Phenology and Vegetation-Plot Databases to Model Terrestrial Plant α-Diversity of the Okavango Basin

In many parts of Africa, spatially-explicit information on plant α-diversity, i.e., the number of species in a given area, is missing as baseline information for spatial planning. We present an approach on how to combine vegetation-plot databases and remotely-sensed land surface phenology (LSP) metrics to predict plant α-diversity on a regional scale. We gathered data on plant α-diversity, measured as species density, from 999 vegetation plots sized 20 m × 50 m covering all major vegetation units of the Okavango basin in the countries of Angola, Namibia and Botswana. As predictor variables, we used MODIS LSP metrics averaged over 12 years (250-m spatial resolution) and three topographic attributes calculated from the SRTM digital elevation model. Furthermore, we tested whether additional climatic data could improve predictions. We tested three predictor subsets: (1) remote sensing variables; (2) climatic variables; and (3) all variables combined. We used two statistical modeling approaches, random forests and boosted regression trees, to predict vascular plant α-diversity. The resulting maps showed that the Miombo woodlands of the Angolan Central Plateau featured the highest diversity, and the lowest values were predicted for the thornbush savanna in the Okavango Delta area. Models built on the entire dataset exhibited the best performance followed by climate-only models and remote sensing-only models. However, models including climate data showed artifacts. In spite of lower model performance, models based only on LSP metrics produced the most realistic maps. Furthermore, they revealed local differences in plant diversity of the landscape mosaic that were blurred by homogenous belts as predicted by climate-based models. This study pinpoints the high potential of LSP metrics used in conjunction with biodiversity data derived from vegetation-plot databases to produce spatial information on a regional scale that is urgently needed for basic natural resource management applications.

Impacts of Land Use on Habitat Functions of Old-Growth Forests and their Biodiversity

Based on a literature review we analysed the influence of historic and contemporary human impacts on the habitat function of old-growth forests in the boreal, the tropics and in selected temperate regions. Old-growth and late-successional forests are of singular relevance for many specialised plant and animal species. These forests possess complex structures. They exhibit spatiotemporal stability and environmental continuity on the larger scales and environmental heterogeneity at the micro-scale. These features appear to be preconditions for the occurrence of obligate old-growth biocenoses and the development of plant–animal interactions that are relevant for ecosystem functioning and biodiversity. Across the world, economic driving forces are exerting strong pressure on the remaining old-growth forests. Human impacts on forests are ubiquitous, and the area covered by intact forest landscapes is continuously decreasing. However, there is no scientific consent about a minimum threshold for acceptable human disturbances in old-growth forests that maintains the potential for a complete restoration of natural dynamics. The future will show to what degree old-growth biota will be able to cope with growing anthropogenic perturbations.

Volume–biomass functions reveal the effect of browsing on three Moroccan dwarf shrubs

We studied the effects of browsing on the plant architecture and volume-biomass relationships of three dominant dwarf shrubs – Artemisia herba-alba, A. mesatlantica and Teucrium mideltense – in a sagebrush steppe in the Central High Atlas Mountains, southern Morocco. For this purpose, we developed power-law volume-biomass functions based on nonlinear regressions for each of these species, under both browsed and unbrowsed conditions. These functions were then applied to individual-based annual monitoring data from inside and outside a browsing exclosure to calculate standing biomass for each of the years from 2004 to 2009. The biomass of the three species was well predicted by the allometric functions, and different functions for the browsed and unbrowsed conditions reflected changes in plant architecture. Browsing had a significant negative impact on biomass for A. herba-alba but not for A. mesatlantica, whereas its effects on T. mideltense were inconsistent between years. The fact that the latter two species hardly benefited from browsing exclusion might be because of increased competition from the more dominant A. herba-alba. During the study period, the standing biomass increased whether or not there was browsing, which might be because of the recovery of the shrubs after a preceding severe drought. Further studies are needed in order to investigate the generality of the findings.