Frequency of Fires in the Miombo Woodland of the Gilé National Park. Province of Zambezia

Fires occur in a widespread manner in various types of vegetation cover at national level, and are often associated with human hunting, grazing and above all the practice of itinerant agriculture. With the purpose to propose the map of frequency of fire, remote sensing data was collected from 2014 to 2018, using the Moderate Resolution Image Spectroradiometer (MODIS) of the burned area (MCD64A1), which allowed the construction of the map of frequency and intensity of fires, associated with data collected in 59 plots on field. It was observed that the Gilé National Park (PNAG) records an average fire frequency of 0.38 times/year and the return interval of 5.38 years, and an average fire return interval of 2.62 years. During the study period, the PNAG burned 92.8% of the area, which means that on average for each year it burned about 18.56% of its area, there are no significant differences in relation to the area burned per year (p> 0.942037) but there are significant differences in relation to the area burned per month (p <1.24e-07).

CROWN MORPHOMETRY FOR TWO VALUABLE TIMBER SPECIES FROM MIOMBO WOODLAND IN MOZAMBIQUE

Pterocarpus angolensis DC and Bobgunnia madagascariensis (Desv.) J. H. Kirkbr. & Wiersema are two hardwood species found in Miombo woodland. Crown size, being closely related to the photosynthetic capacity of a tree, is an important parameter in studies of the growth of individual trees. In this sense, the present study aimed to study the morphometric relationships of P. angolensis and B. madagascariensis as a resource to describe the morphometric features of these species. Data were sampled in 60 rectangular plots of 20 x 50 m, systematically distributed within the forest. In each plot, the diameter at breast height (DBH), height (h), crown insertion point (cih) and four crown radii of all trees with DBH ≥ 10 cm were measured. Results indicated that crown diameter and crown length of P. angolensis grow as DBH and height increase, the larger the crown, the greater the trees dimensions; as for B. madagascariensis, crown features have shown low correlation when considering DBH. It was concluded that crown features influence on tree growth and are important measures of description and planning of silvicultural activities to be performed in natural forests. The results are of interest to forest managers since they make decisions about silvicultural operations. Keywords: crown dimensions; prediction models; umbila; pau-ferro; forest management.

Edaphic factors controlling soil organic matter and C storage in miombo woodlands, Zambia

Soil organic matter (SOM) is a key component of forest productivity and soil organic carbon stock. However, little is known about SOM and C variability in miombo woodlands which is a significant ecosystem in sub-Sahara African forests and vital for REDD+ strategies. In this study, nine edaphic factors were measured and used to analyse the variability of SOM in miombo woodland sites with different tree structures in Luanshya, Zambia. The findings showed a large variability of SOM stocks at different soil depths: 36.67 to 113.89 Mg ha-1 at 0–10 cm depth, 28.67 to 79.56 Mg ha-1 at 10–20 cm depth, and 31.89 to 98.56 Mg ha-1 at 20–30 cm depth. These SOM values at different depths also varied between miombo woodland sites of different successional stages, notably that areas affected by recent tree clearance had higher than average SOM content per layer (0–10 cm: +5.57%; 10–20 cm: +4.20%; 20–30 cm: +4.30%). Canonical correspondence analysis (CCA) revealed that the most significant environmental factors influencing SOM were woodland thinning by clearance, and silt content within soils. This study highlights that CCA can be used to show the relative importance of different forest successional stages as a function of management practices, as well as edaphic factors, in determining miombo soil SOM content. The results of this study are particularly relevant for addressing current REDD+ reforestation and management strategies that are aimed at increasing carbon stocks in the tropical forests of sub-Saharan Africa.

Density responses of lesser-studied carnivores to habitat and management strategies in southern Tanzania’s Ruaha-Rungwa landscape

Compared to emblematic large carnivores, most species of the order Carnivora receive little conservation attention despite increasing anthropogenic pressure and poor understanding of their status across much of their range. We employed systematic camera trapping and spatially explicit capture-recapture modelling to estimate variation in population density of serval, striped hyaena and aardwolf across the mixed-use Ruaha-Rungwa landscape in southern Tanzania. We selected three sites representative of different habitat types, management strategies, and levels of anthropogenic pressure: Ruaha National Park’s core tourist area, dominated by Acacia-Commiphora bushlands and thickets; the Park’s miombo woodland; and the neighbouring community-run MBOMIPA Wildlife Management Area, also covered in Acacia-Commiphora. The Park’s miombo woodlands supported a higher serval density (5.56 [Standard Error = ±2.45] individuals per 100 km2) than either the core tourist area (3.45 [±1.04] individuals per 100 km2) or the Wildlife Management Area (2.08 [±0.74] individuals per 100 km2). Taken together, precipitation, the abundance of apex predators, and the level of anthropogenic pressure likely drive such variation. Striped hyaena were detected only in the Wildlife Management Area and at low density (1.36 [±0.50] individuals per 100 km2), potentially due to the location of the surveyed sites at the edge of the species’ global range, high densities of sympatric competitors, and anthropogenic edge effects. Finally, aardwolf were captured in both the Park’s core tourist area and the Wildlife Management Area, with a higher density in the Wildlife Management Area (13.25 [±2.48] versus 9.19 [±1.66] individuals per 100 km2), possibly as a result of lower intraguild predation and late fire outbreaks in the area surveyed. By shedding light on three understudied African carnivore species, this study highlights the importance of miombo woodland conservation and community-managed conservation, as well as the value of by-catch camera trap data to improve ecological knowledge of lesser-studied carnivores.

Stable isotope signatures of soil nitrogen on an environmental–geomorphic gradient within the Congo Basin

Nitrogen (N) availability can be highly variable in tropical forests on regional and local scales. While environmental gradients influence N cycling on a regional scale, topography is known to affect N availability on a local scale. We compared natural abundance of 15N isotopes of soil profiles in tropical lowland forest, tropical montane forest, and subtropical Miombo woodland within the Congo Basin as a proxy to assess ecosystem-level differences in N cycling. Soil δ15N profiles indicated that N cycling in the montane forest is relatively more closed and dominated by organic N turnover, whereas the lowland forest and Miombo woodland experienced a more open N cycle dominated by inorganic N. Furthermore, we examined the effect of slope gradient on soil δ15N within forest types to quantify local differences induced by topography. Our results show that slope gradient only affects the soil δ15N in the Miombo forest, which is prone to erosion due to a lower vegetation cover and intense rainfall at the onset of the wet season. Lowland forest, on the other hand, with a flat topography and protective vegetation cover, showed no influence of topography on soil δ15N in our study site. Despite the steep topography, slope angles do not affect soil δ15N in the montane forest, although stable isotope signatures exhibited higher variability within this ecosystem. A pan-tropical analysis of soil δ15N values (i.e., from our study and literature) reveals that soil δ15N in tropical forests is best explained by factors controlling erosion, namely mean annual precipitation, leaf area index, and slope gradient. Erosive forces vary immensely between different tropical forest ecosystems, and our results highlight the need for more spatial coverage of N cycling studies in tropical forests, to further elucidate the local impact of topography on N cycling in this biome.