Effects of enclosure management on carbon sequestration, soil properties and vegetation attributes in East African rangelands

Abstract

The use of enclosures has globally gained popularity as an effective strategy to enhance soil carbon sequestration, but empirical evidence is lacking particularly in arid and semi-arid rangelands of Africa. This study addressed the effectiveness of long-term (15–37years old) enclosures in enhancing soil carbon sequestration in a semi-arid rangeland of Southern Ethiopia. We tested for differences in soil properties and vegetation characteristics between enclosures and adjacent open-grazed areas, while accounting for effects of age of enclosures and soil depths. Three enclosures age categories (<20, 20–30 and >30years) each paired with adjacent open-grazed areas were selected. We collected soil samples at three soil depths (0–5cm, 5–15cm and 15–30cm), and vegetation attributes from 90 plots within 9 enclosures and adjacent open grazing sites. The results showed that soil properties did not differ significantly (P>0.05) between the two management systems across the three soil depths. However, relatively higher soil organic carbon content and stock was recorded in the enclosures than open-grazed lands. We recorded an overall mean of soil organic carbon stock of 39.6±3.5Mgha−1 in enclosures of <20years old, 40.8±3.4Mgha−1 in enclosures of 20–30years old and 51.0±4.4Mg ha−1 in enclosures of >30years old. The soil organic carbon stock for the adjacent open-grazed areas ranged from 34.4±2.5 to 47.9±5.1Mgha−1. The age of enclosures did not show any significant effect on soil organic carbon stocks. However, enclosure management had a significant (P≤0.05) effect on vegetation attributes. We concluded that enclosure had a significant role in terms of soil carbon sequestration and adaptation to climate change.