Assessment of stocking, productivity, and aboveground biomass of tree species used as fuelwood in Rwanda's agricultural landscapes

Abstract

Tree-based systems (TBS) in the agricultural landscape of Rwanda do supply considerable amounts of fuelwood to the local communities. However, there needs to be more information on the available stocking, aboveground biomass (AGB), and productivity of the trees used for fuelwood. The study aims to assess the common tree species used for fuelwood and quantify the biomass stock across various TBS in the agricultural landscape. The study used a systematic sampling design, establishing 130 band transects, each measuring 2 km x 5 m. The transects were systematically distributed across the Bugesera and Musanze Districts, representing low and high-altitude regions. In Bugesera District, the common tree species for fuelwood use were Grevillea robusta, Eucalyptus spp., Senna spectabilis, and Markhamia lutea. The results indicated that the mean stem density and AGB of Eucalyptus spp. and S.spectabilis were substantially higher than other species. Across all TBS categories, trees covered an average stem density of 50 stems/ha and an AGB of 2.07t/ha. The stem density and AGB were substantially higher in boundary plantings and mixed cropping than in other TBS. Most trees in all TBS categories had a DBH ranging from 1 to 5 cm, except for the woodlot, where trees had a DBH ranging between 5.1–10 cm. In Musanze District, the common tree species for fuelwood use were G.robusta, Eucalyptus spp., Alnus acuminata, and M.lutea. The mean stem density, standing AGB, and productivity of Eucalyptus spp. were substantially higher than those of the other species. Across all TBS, trees covered an average stem density of 109 stems/ha and AGB of 5.38t/ha. The number of stems and AGB were substantially higher in boundary plantings and woodlots than in mixed cropping, live fences, and home gardens. Furthermore, the results on fuelwood supply indicated that S.spectabilis in Bugesera and Eucalyptus spp. in Musanze have a higher potential to produce higher biomass in short rotation.