An integrated agroforestry-bioenergy system for enhanced energy and food security in rural sub-Saharan Africa.

Most people in rural sub-Saharan Africa lack access to electricity and rely on traditional, inefficient, and polluting cooking solutions that have adverse impacts on both human health and the environment. Here, we propose a novel integrated agroforestry-bioenergy system that combines sustainable biomass production in sequential agroforestry systems with biomass-based cleaner cooking solutions and rural electricity production in small-scale combined heat and power plants and estimate the biophysical system outcomes. Despite conservative assumptions, we demonstrate that on-farm biomass production can cover the household's fuelwood demand for cooking and still generate a surplus of woody biomass for electricity production via gasification. Agroforestry and biochar soil amendments should increase agricultural productivity and food security. In addition to enhanced energy security, the proposed system should also contribute to improving cooking conditions and health, enhancing soil fertility and food security, climate change mitigation, gender equality, and rural poverty reduction.

Evaluation of rangeland condition in miombo woodlands in eastern Tanzania in relation to season and distance from settlements.

Miombo woodlands sustainability in east and south-central Africa is threatened by human activities, including overgrazing. This study investigated seasonal variations in rangeland condition in three grazed areas in miombo woodlands in eastern Tanzania. Transect lines were established across the grazing areas, sampling points were identified and marked at every 10% of the length of transect line. Sampling points were categorised in different distances with respect to settlement. The line intercept method was used to collect data on vegetation cover and forage distribution, while herbaceous forage biomass was estimated using a disc pasture meter. A total of 118 different plant species were observed and grasses comprised 40.6% of all herbaceous species. Bothriochloa pertusa, Cynodon plectostachyus, Hyparrhenia rufa and Urochloa mosambicensis grass species dominated miombo grazed areas in various seasons and distances. These perennial grass species are desirable and indicated moderate grazing activities in miombo. Season affected grass cover, herbaceous forage biomass and nutritional composition. Grass cover and forage biomass were at the lowest during late dry season while forage nutritional quality was best during early dry season. Distance from settlement had no effect on grass cover and herbaceous forage biomass. Rangeland condition was generally fair, livestock stocking rate in continuously grazed drylands should be set at the lowest monthly forage biomass in order to ensure grazing land sustainability.

Pasture enclosures increase soil carbon dioxide flux rate in Semiarid Rangeland, Kenya.

BACKGROUND: Pasture enclosures play an important role in rehabilitating the degraded soils and vegetation, and may also influence the emission of key greenhouse gasses (GHGs) from the soil. However, no study in East Africa and in Kenya has conducted direct measurements of GHG fluxes following the restoration of degraded communal grazing lands through the establishment of pasture enclosures. A field experiment was conducted in northwestern Kenya to measure the emission of CO2, CH4 and N2O from soil under two pasture restoration systems; grazing dominated enclosure (GDE) and contractual grazing enclosure (CGE), and in the adjacent open grazing rangeland (OGR) as control. Herbaceous vegetation cover, biomass production, and surface (0-10 cm) soil organic carbon (SOC) were also assessed to determine their relationship with the GHG flux rate. RESULTS: Vegetation cover was higher enclosure systems and ranged from 20.7% in OGR to 40.2% in GDE while aboveground biomass increased from 72.0 kg DM ha-1 in OGR to 483.1 and 560.4 kg DM ha-1 in CGE and GDE respectively. The SOC concentration in GDE and CGE increased by an average of 27% relative to OGR and ranged between 4.4 g kg-1 and 6.6 g kg-1. The mean emission rates across the grazing systems were 18.6 µg N m-2 h-1, 50.1 µg C m-2 h-1 and 199.7 mg C m-2 h-1 for N2O, CH4, and CO2, respectively. Soil CO2 emission was considerably higher in GDE and CGE systems than in OGR (P < 0.001). However, non-significantly higher CH4 and N2O emissions were observed in GDE and CGE compared to OGR (P = 0.33 and 0.53 for CH4 and N2O, respectively). Soil moisture exhibited a significant positive relationship with CO2, CH4, and N2O, implying that it is the key factor influencing the flux rate of GHGs in the area. CONCLUSIONS: The results demonstrated that the establishment of enclosures in tropical rangelands is a valuable intervention for improving pasture production and restoration of surface soil properties. However, a long-term study is required to evaluate the patterns in annual CO2, N2O, CH4 fluxes from soils and determine the ecosystem carbon balance across the pastoral landscape.

Combining airborne laser scanning and Landsat data for statistical modeling of soil carbon and tree biomass in Tanzanian Miombo woodlands.

BACKGROUND: Soil carbon and biomass depletion can be used to identify and quantify degraded soils, and by using remote sensing, there is potential to map soil conditions over large areas. Landsat 8 Operational Land Imager satellite data and airborne laser scanning data were evaluated separately and in combination for modeling soil organic carbon, above ground tree biomass and below ground tree biomass. The test site is situated in the Liwale district in southeastern Tanzania and is dominated by Miombo woodlands. Tree data from 15 m radius field-surveyed plots and samples of soil carbon down to a depth of 30 cm were used as reference data for tree biomass and soil carbon estimations. RESULTS: Cross-validated plot level error (RMSE) for predicting soil organic carbon was 28% using only Landsat 8, 26% using laser only, and 23% for the combination of the two. The plot level error for above ground tree biomass was 66% when using only Landsat 8, 50% for laser and 49% for the combination of Landsat 8 and laser data. Results for below ground tree biomass were similar to above ground biomass. Additionally it was found that an early dry season satellite image was preferable for modelling biomass while images from later in the dry season were better for modelling soil carbon. CONCLUSION: The results show that laser data is superior to Landsat 8 when predicting both soil carbon and biomass above and below ground in landscapes dominated by Miombo woodlands. Furthermore, the combination of laser data and Landsat data were marginally better than using laser data only.

Enclosing the commons: reasons for the adoption and adaptation of enclosures in the arid and semi-arid rangelands of Chepareria, Kenya.

The adoption and adaptation of enclosures in the arid and semi-arid rangelands of sub-Saharan Africa is driven and sustained by a combination of factors. However, reviews indicate that these factors cannot be generalized, as they tend to be case specific. A study was therefore conducted to explore the history and reasons for enclosure establishment in Chepareria, a formerly degraded communal rangeland in north-western Kenya. While Vi-Agroforestry Organization accounting for 52.5 % was the main source of knowledge on enclosure establishment; it has now emerged that rangeland enclosures among the Pokot pastoral community existed prior to land management interventions by Vi- Agroforestry. Results indicated that there are three categories of enclosures which were established for boundary demarcation, provide grazing reserves, enable proper land management, facilitate crop cultivation in a pastoral setup and to curb land degradation. The role of self-trigger [accounting for most of the spontaneous enclosures (73.5 %)] indicates the continued establishment and expansion of areas under enclosure management as private land ownership accounting for 51.7 % of enclosure tenure continues to gain momentum in Chepareria. While rangeland enclosures in Chepareria were mainly established for boundary demarcation, to alleviate pasture scarcity and enable proper management of formerly degraded areas; they have facilitated land restoration and rehabilitation by increasing flexibility in land, fodder and livestock management amongst agro-pastoralists in Chepareria over the last three decades. To ensure that rehabilitated areas do not revert to their previously degraded state; technical interventions are needed to allow for a more intensive use of rangeland resources within enclosed areas.

13C-discrimination during microbial respiration of added C3-, C4- and 13C-labelled sugars to a C3-forest soil.

We tested whether 13C-discrimination during microbial respiration, or during CO2 sampling in the field, can explain changes observed in the δ13C of emitted CO2 that follow the addition of C4-sucrose, as a microbial substrate, to the soil of a C3-ecosystem. We approached this problem by adding C3-glucose (δ13C=-23.4‰), C4-sucrose (-10.8‰) or 13C-labelled glucose (103.7‰) to the intact mor layer, the upper organic soil (-26.5‰, bulk soil organic matter), of a boreal Pinus sylvestris L. forest. If 13C-discrimination is significant, it should generate illusory differences in the calculated contributions from the added C and endogenous C3-C to total soil respiration, when C4-sucrose or 13C-labelled glucose is added. Further, if discrimination occurs, we should also be able to detect a shift in the δ13C of respired CO2 after the addition of C3-glucose. The addition of the three sugar solutions gave similar increases in soil respiration (up to a doubling 1 h after the additions), while the addition of water gave no increase in respiration. There was no change in δ13C of the emitted CO2 after additions of H2O or C3-glucose. In contrast, the addition of C4-sucrose and 13C-labelled glucose gave δ13C values of evolved CO2 that were 4.5‰ and 30.3‰ higher than the pre-sugar values, respectively. The calculated respiration rates of the added carbon sources, C4-C or 13C-labelled C, were very similar. Also, we found very similar sugar-induced increases in respiration of endogenous C3-C in the plots supplied with C4-sucrose and 13C-labelled glucose, accounting for about 50% of the total increase in respiration 1 h after addition. Our results confirm that any microbial 13C-discrimination during respiration is minor.