Exclosures backed up with community-based soil and water conservation practices increased soil organic carbon stock and microbial biomass carbon distribution, in the northern highlands of Ethiopia

Abstract

Background: Land degradation is a treat for natural resources in Tigray high lands of northern Ethiopia, where 30-50 percent of the soil productive capacity has been lost in the past 500 years. Restoration and management of degraded lands improve soil health through enhancing soil organic carbon (SOC) stock and microbial biomass carbon (MBC). The knowledge on SOC and MBC concentration and distribution is essential to refine soil management, thereby restoring the ecosystem. This paper quantified the effect of decades old community-based soil and water conservation (SWC) measures, mainly stone terraces, exclosure with and without stone terraces, and non-conserved communal grazing lands on the distribution of MBC and SOC stock.Methods: Soil sample collection was carried out using systematic sampling design. Transects parallel to each other and to the slope of the landscape were established. In each transect, three landscape positions (i.e., upper, middle, and foot slope) were formed. Composite soil samples were taken from four corners and center of 10 m × 10 m plot of each slope positions under the different SWC measures. Analysis of variance was used to determine the difference in SOC and MBC using SAS 9.2. Results:Total soil organic carbon concentration was significantly higher in exclosures as compared to terraces and non-conserved grazing lands. The highest mean value of SOC stock (29 Mg C ha ) was recorded in non-conserved communal grazing lands. Exclosures with terraces improved SOC stock by 64%, followed by exclosures without terraces by 37%, while terraces improved the SOC stock by 25% compared to non-conserved open communal grazing lands in the last 20 years. The upper (0-15 cm) soil depth had significantly (P < 0.05) higher (24 Mg C ha ). Microbial biomass carbon was the highest (640 mg kg −1 soil) in exclosures without terraces, followed by exclosures with terraces, (570 mg kg −1 soil), terraces (440 mg kg −1 soil), and non-conserved communal grazing lands (370 mg kg −1 soil). Conclusion:Exclosures supported with terraces improved and restored the SOC stock and microbial biomass carbon of degraded free grazing lands in the highlands.

Advances in quantifying soil organic carbon under different land uses in Ethiopia: a review and synthesis

“…The assessment indicated that removal of residues, total harvest, and leaching losses accounted for the major causes of nutrient losses under permanent and vegetable cropping while erosion accounted for the major causes of nutrient losses in under cereals and other annuals. Welemariam et al (2018) assessed the impact of exclosures and soil and water conservation (SWC) practices on SOC concentration, SOC stock, and microbial biomass carbon in the highlands of northern Ethiopia. They reported that exclosures with terraces gave the highest SOC stock (29 Mg/ha) followed by exclosures only (24 Mg/ha), terraces (21 Mg/ha), and non-conserved grazing lands (16 Mg/ha).…”

“…In Ethiopia, significant increase in SOC and improvement of ecosystem services has been achieved through the conversion of open grazing lands to exclosures (protected areas with zero grazing and prohibition of human activities) across different agro-ecological zones (Descheemaeker et al 2006a(Descheemaeker et al , 2006bCorral-Nuñez et al 2014;Assefa et al 2017;Welemariam et al 2018). For example, Corral-Nuñez et al 2014 studied the current and predicted SOM in northern Ethiopia and reported significant recovery of SOM ranging from 2.6 to 5.6% in exclosure after 20 years compared to 2.1% to 2.9% in cropland.…”

“…More so, Assefa et al 2017 reported that the conversion of a degraded open grazing land to exclosure significantly increased SOC stock in the topsoil layer (0-10 cm) by 42%. Similarly, Welemariam et al 2018 studied the impact of different land use and management practices on SOC and reported that exclosures backed up with community-based soil and water conservation practices increased SOC stock. Their result indicated that exclosure with terraces, exclosures alone, terraces, and non-conserved open grazing lands gave 29, 24, 21, and 16 Mg C/ha respectively.…”

Impact of Ex-Closure in above and below Ground Carbon Stock Biomass

“…Soil carbon change can happen in response to a broad range of environmental and management factors [73]. Livestock grazing is a vitally common issue that affects plant growth, plant species diversity, and soil carbon accumulation [74]. In 2010, between one-third and a half of the entire world's agricultural land was in a degraded condition, and a fifth was considered severely degraded.…”

The effect of exclosures on restoration of soil properties in Ethiopian lowland conditions

“…Studies conducted by authors [6][7][8][9][10][11][12] have shown the positive role of conversion of grazing lands to exclosures on restoration of soils that were previously degraded in the region. However, most of these studies focused in the mid (1500-2300 m above sea level) and highlands (> 2300 m above sea level) with limited focus to the lowlands (< 1500 m above sea level) such as the study area, Tselemti district.…”