Area exclosure as a strategy to restore woody plant species diversity and soil fertility status in degraded land: case study in mitija watershed, souhern Ethiopia

Abstract

Land degradation is revealed in the form of vegetation and soil fertility degradation. It is becoming a major ecological and agricultural problem in Ethiopia. To overcome the problems of land degradation area exclosure is used as strategy to restore degraded lands in Hulbarag Wereda, Siltie Zone, SNNPRS. The general objective is to assess and evaluate the usefulness of exclosure technique in enhancing rehabilitation of degraded ecosystem and thereby increase the natural capital in the area. Woody plant species and soil samples were collected with the transects from area exclosure for eight year and adjacent degraded land with similar landscape positions. Both soil and woody plant species were collected from transects by systematic sampling plot design technique. The woody plant species were identified by using a field guideline. The woody species diversity was determined by Shannon diversity. To determine soil fertility status of area exclosure and adjacent degraded soil, samples were analyzed for soil organic carbon (SOC), cation exchange capacity (CEC), total nitrogen (TN), pH, electrical conductivity (EC), available phosphorus (Av. P), exchangeable bases (K+ , Na+ , Ca+ , Mg2+), soil texture, moisture content and bulk density (BD). Comparative assessment result of woody plant species analysis showed that the density of woody species in the exclosure and degraded site were 778 and 222 individuals per hectare, respectively. A total of 16 woody species, representing 12 families were recorded in the study site. Out of the 12 families, all were recorded in the exclosure while 5 were recorded in the degraded site. Out of the 16 species, 15 were recorded in the exclosure while six were in the degraded site. A total of 10 species were recorded in the exclosure, which were absent in the degraded site. Similarly a species was recorded in the degraded sites, which were not present in the exclosure. Exclosed areas had significantly (P<0.05) different values for all soil parameters except for bulk density, EC and pH. The higher bulk density, sand, EC, and pH were recorded in the degraded site, whereas the rest of soil properties were high in exclosure. The present study indicated that, the mean values for degraded and exclosure sites in soil of OC, TN and Av.P were 2.21 and 1.61, 0.19 and 0.14, and 7.92 and 5.88, respectivily. Apart from increasing woody plant species and soil fertility improvement, these local communities has benefited from the exclosure by collecting of forage for livestock via cut-and-carry system and farmland protection from clotting with silt and mud from the upper catchments. This has enabled this local community to develop a positive attitude towards exclosure development. Generally, area exclosure has a great contribution to restore woody plant species and soil fertility status in the study area. Therefore, to improve the livelihood of the local community area exclosure practices should be expanded to other degraded watersheds and private farmlands.