Grazing increases albedo of savanna grasslands
Abstract: Earlier studies done in the north have shown that grazing increases surface albedo by reducing shrub height and abundance, and thus have the potential to cool down the local climate. But what about effect of grazing in other systems? In African savanna grasslands some grazers are able to transform grass swards into a lawn-like state by regular grazing. The grazing excludes tall-grass colonizers and the spread of lawn grasses is thus promoted by grazing. A characteristic of savanna ecosystems is the tree-grass coexistence. Field experiments have indicated that in the absence of herbivory and fire, woody plant encroachment in savannas can be high, but grazing lawns seem to be resistant to shrub invasion. I investigate how the creation of grazing lawns affects the albedo of savanna grasslands. By comparing albedo between grazing lawns, bunch grass and woody shrubs. I also quantify the extent of grazing lawns across the. I show that grazing lawns have a significantly higher albedo than both bunch grass and grass encroached by woody plants and that albedo increased during the growing season. Albedo decreased when the amount of bare soil increased, and albedo increased with more grass. The assessment of grazing lawn distribution in the park showed that lawns in some parts cover 20% of the transect area. This study shows that grazing lawns, and by extension grazers, could affect the local climate on African savannas, through a higher albedo.
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