Impact of farm exclosure on woody species abundance and carbon stock in Tigray, Northern Ethiopia

Abstract Trees on farm provide numerous supporting and regulating services. Some services are biodiversity conservation and enhancement of carbon stock storage. This depends upon the exclusion of livestock intervention to farmlands. In Ethiopia, exclosure has been implemented on communal grazing lands which brought better abundance and enhanced carbon stock than open grazing lands. Recently, the idea of exclosure has been implemented on farmlands. This study investigated the impact of farm exclosures on woody species abundance, diversity and carbon stock. Two farm types, such as farm exclosure, where there is exclusion of livestock throughout the year, and open farms, where livestock freely graze in the winter, were selected in the districts of Hawzen and Hintalo Wajirat, Tigray, Ethiopia. Eighteen farm sample plots having an area of half a hectare (100*50) were chosen randomly from each farm type, totaling 36 plots. Height, diameter at breast height and diameter at stump height were recorded for trees and shrubs found in the sample plots. Fifteen woody species representing 10 families were recorded in farm exclosures and nine species representing seven families were recorded in the open farms. Higher abundance, basal area, vegetation biomass and vegetation carbon stock were observed in the farm exclosures. Mean abundance of all woody species was 21.34 and 13.44 trees ha−1; basal area, 0.55 and 0.18 m2 ha−1; species richness, 2.72 and 2.11; Shannon diversity, 1.64 and 1.74; and vegetation carbon stock, 4.57 and 1.18 ton ha−1, for farm exclosures and open farms, respectively. The result showed that there is a significant difference in mean abundance (p < 0.05), basal area (p < 0.01) and carbon stock (p < 0.01) between the farm exclosures and open farms. Thus, exclosures applied in farmlands have a considerable contribution in increasing woody species abundance, basal area and vegetation carbon stock.