Abstract
Savannahs provide valuable ecosystem services and contribute to continental and global carbon budgets. In addition, savannahs exhibit multiple land uses, e.g., wildlife conservation, pastoralism, and crop farming. Despite their importance, the effect of land use on woody aboveground biomass (AGB) in savannahs is understudied. Furthermore, fences used to reduce human–wildlife conflicts may affect AGB patterns. We assessed AGB densities and patterns, and the effect of land use and fences on AGB in a multi-use savannah landscape in southeastern Kenya. AGB was assessed with field survey and airborne laser scanning (ALS) data, and a land cover map was developed using Sentinel-2 satellite images in Google Earth Engine. The highest woody AGB was found in riverine forest in a conservation area and in bushland outside the conservation area. The highest mean AGB density occurred in the non-conservation area with mixed bushland and cropland (8.9 Mg·ha−1), while the lowest AGB density (2.6 Mg·ha−1) occurred in overgrazed grassland in the conservation area. The largest differences in AGB distributions were observed in the fenced boundaries between the conservation and other land-use types. Our results provide evidence that conservation and fences can create sharp AGB transitions and lead to reduced AGB stocks, which is a vital role of savannahs as part of carbon sequestration.
Highlights
Savannahs are characterized by scattered tree cover and continuous coverage of grass-dominated herbaceous plants [1,2]
Our results reveal a significant difference (P < 0.05) in woody aboveground biomass (AGB) among the land cover and land-use classes in the studied landscape
Taita Hills lowland savannah landscape, similar to other typical African savannah biomes, exhibits multi-use functionality, which results in heterogeneous land cover
Summary
Savannahs are characterized by scattered tree cover and continuous coverage of grass-dominated herbaceous plants [1,2]. On the African continent, savannahs and woodlands play a large role in the carbon cycle, and wildlife and biodiversity conservation, while providing livelihoods for a huge human population [3]. The area covered by savannahs is roughly three times larger than that of forests, corresponding to approximately 50% of the total area of the African continent. Savannahs represent a major carbon stock in Africa despite having a lower carbon density compared to forests [4,5,6]. Another significant feature of the African carbon cycle is that emissions caused by land-use change are greater than fossil fuel emissions [7,8].
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