Spatial and temporal variations of soil microbial respiration under native and exotic tree species

Lameck Davie Nyirenda1, James Majamanda, Anas Khalif, Mana Kanjanamaneesathian
Corresponding email: [email protected]


Different tree species can directly or indirectly affect soil conditions. They influence soil microbial diversity and abundance and hence soil respiration. Trees and soil respiration have a complex relationship that is poorly understood, as does the seasonal and spatial variation that naturally occurs in them. This study was therefore conducted to evaluate soil respiration processes under two native tree species, Msuku (Uapaca kirkiana) and Mtondo (Julbernardia paniculata), and one introduced tree species, Malaina (Gmelina arborea). In 2019 (March and October), soil samples were taken at 0.5m, 1.5m, 2.5 m, and 3.5m intervals from the trunks of the chosen tree species at depths of 0–10 cm and 10–20 cm. Using the alkali absorption method, soil respiration was assessed. The findings demonstrated that respiration decreased with the increase in horizontal distance from the trunk of both indigenous species. On the contrary, soil respiration increased with the increase in horizontal distances from the trunks of introduced tree species. The findings also demonstrated that respiration was higher at 0–10 cm than at 10–20 cm soil depths in both March and October under all three tree species. The higher microbial soil respiration in the surface layer could be attributed to better soil aeration, as opposed to the sub-surface soil. Furthermore, soil respiration was higher for soils collected in March than soils collected in October, probably because March is associated with the rainy season in which soil moisture content is higher than October. It can be concluded that different tree species strongly influence spatial and vertical soil respiration differently. This calls for proper selection of tree species to be utilised in agroforestry. Therefore, knowledge of nutrient uptake of various tree species and the influence of tree species on soil processes, but also microbial population effects on nutrient cycling linked to various tree species is essential.

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