Abstract
Soil and water conservation (SWC) practices in the northern highlands of Ethiopia have important implications for land restoration and biodiversity recovery. The present study determined soil macroinvertebrate (SMI) abundance and diversity in response to spatial conditions i.e., generated by different conservation practices, soil depth, and temporal seasonality with the wet and dry season. The SWC practices considered were exclosure + terrace, exclosure alone, terraces, and non-conserved grazing lands. Each SWC measure was selected in three sites that were considered as replications due to low heterogeneity in terms of human and livestock disturbances and biophysical factors. Soil macroinvertebrates were collected using a monolith according to tropical soil biology and fertility (TSBF) method. The highest density (55%) of SMI was found in exclosures followed by terraces 26%. Non-conserved communal grazing lands account for only 19% of the total. Shannon diversity index was significantly (P < 0.05) higher (1.21) in the exclosures supported with terraces and the lowest (0.9) was observed in the non-conserved communal grazing lands. Diversity was also significantly (P < 0.05) higher (1.26) in wet than dry season (0.70). The highest (41%) Sorensen similarity index among SMI was found between exclosures with terraces and exclosures alone during the wet season. The lowest (20%) Sorensen similarity index was found between terraces alone and exclosures with terraces in dry season. Soil macroinvertebrate abundance was higher in upper (0–10 cm) than lower (10–20 and 20–30 cm) soil depth. Soil macroinvertebrate abundance was positively and strongly correlated with soil moisture (R2 = 0.85) and soil organic carbon stock (R2 = 0.95). However, it was negatively (R2 = −0.71) correlated with bulk density. Generally, the abundance and diversity of SMI increased as exclosures and communal grazing lands are supported with terraces.
Highlights
Land degradation is a common problem in Ethiopian highlands [1]
The lowest abundance (19%) of soil macroinvertebrate (SMI) was found in non-conserved communal grazing lands (Table 3)
Soil macroinvertebrate abundance increased with plantation or vegetation cover [13]
Summary
Land degradation is a common problem in Ethiopian highlands [1] It is manifested in the form of soil erosion and decline of biodiversity resources in Tigray highlands, northern Ethiopia [2]. It is mainly the result of clearing the natural vegetation and includes deterioration in soil physical, biological, and chemical properties [1]. Agronomy 2018, 8, 56 common problem in the region This free grazing contributed to land degradation [3]. It was found that restoring degraded drylands is technically promising when using area exclosures [3] They are important biological measures to combat land degradation and to increase biomass production [8]
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