Inhibitory activity of bacterial lipopeptides against Fusarium oxysporum f.sp. Strigae.

This study investigated the influence of bacterial cyclic lipopeptides (LP; surfactins, iturins, fengycins) on microbial interactions. The objective was to investigate whether the presence of bacteria inhibits fungal growth and whether this inhibition is due to the release of bacterial metabolites, particularly LP. Selected endophytic bacterial strains with known plant-growth promoting potential were cultured in the presence of Fusarium oxysporum f.sp. strigae (Fos), which was applied as model fungal organism. The extracellular metabolome of tested bacteria, with a focus on LP, was characterized, and the inhibitory effect of bacterial LP on fungal growth was investigated. The results showed that Bacillus velezensis GB03 and FZB42, as well as B. subtilis BSn5 exhibited the strongest antagonism against Fos. Paraburkholderia phytofirmans PsJN, on the other hand, tended to have a slight, though non-significant growth promotion effect. Crude LP from strains GB03 and FZB42 had the strongest inhibitory effect on Fos, with a significant inhibition of spore germination and damage of the hyphal structure. Liquid chromatography tandem mass spectrometry revealed the production of several variants of iturin, fengycin, and surfactin LP families from strains GB03, FZB42, and BSn5, with varying intensity. Using plate cultures, bacillomycin D fractions were detected in higher abundance in strains GB03, FZB42, and BSn5 in the presence of Fos. Additionally, the presence of Fos in dual plate culture triggered an increase in bacillomycin D production from the Bacillus strains. The study demonstrated the potent antagonistic effect of certain Bacillus strains (i.e., GB03, FZB42, BSn5) on Fos development. Our findings emphasize the crucial role of microbial interactions in shaping the co-existence of microbial assemblages.

The role of landscape management practices to address natural resource degradation and human vulnerability in Awash River basin, Ethiopia.

Landscape management practices (LMP) support addressing the vulnerability of small-scale producers (SSPs) through providing a means of sustaining and strengthening community livelihoods and building their resilience and the environment. However, addressing the vulnerability of SSPs through the implementation of LMP requires meaningful community engagement and assessing the benefits and costs from the perspective of local communities. This study was conducted in two watersheds, Maybar-Felana and Gelana, in the Awash River basin, Ethiopia. The study assessed the links between natural resource degradation and the vulnerability of SSPs, local communities' opinion on the benefits and costs of LMP and the implications of implementing LMP for addressing vulnerability. It gathered and analyzed data through key informant interviews (KII), focus group discussions (FGDs) and GIS and remote sensing techniques. Diverse LMP such as afforestation/reforestation, exclosures, terrace and bunds and crop- and soil-based soil amendments were adopted in the studied watersheds. These practices contributed to the improvement of natural resources such as forests and the services they provide. Over the last 21 years (2000-2021), forest cover increased by 11.5 and 42.5% in Maybar-Felana and Gelana watersheds, respectively, while shrublands increased by 41.1% in Maybar-Felana. In line with this, the SSPs identified multiple benefits of LMP including the restoration of degraded vegetation, reducing runoff and soil loss, improving access to water for multiple uses and increasing agricultural productivity. The adopted LMP contributed to reducing livelihood vulnerability through reducing incidents of weather extremes such as flood and drought, improving food and water security, enhancing resource availability, and building livelihood assets. The SSPs also identified multiple economic and social costs of LMP, suggesting that addressing the economic and social costs through balancing short-term economic losses with long-term environmental benefits of interventions is crucial to sustaining the LMP and the benefits they provide.

Exclosures improve degraded landscapes in the sub-humid Ethiopian Highlands: the Ferenj Wuha watershed.

Land resources in developing countries are facing intense degradation due to deforestation and subsequent loss of organic matter from continuous tillage that causes soil erosion and gulley formation. The Ethiopian highlands are especially and severely affected. One of the land and water management practices to counteract this problem, fenced areas to prevent livestock access (called exclosures), has been in practice for the last few decades in the semi-arid highlands of Ethiopia but its effect on degraded landscapes has not been well researched -- especially in the sub-humid and humid highlands. The aim of this study is to evaluate the effects of exclosures on improving degraded landscapes in the sub-humid highlands. The research was carried out in the Ferenj Wuha watershed, in the northwestern sub-humid Ethiopian highlands, where land and water management practices were implemented starting in 2011. Vegetation was inventoried and aboveground biomass, carbon and nutrient stock determined for communal grazing land, exclosures and for other uses. In addition, soil samples were collected for nutrient analysis. Our results show that exclosures have a richer and more diverse set of plant species compared to communal grazing land. Establishment of an exclosure also enhanced organic carbon, total nitrogen and available phosphorus. Over a six-year period, aboveground biomass increased by 54 Mg ha-1 (or 81%) at the watershed scale because of the conversion of communal grazing land to exclosures. The improvement in soil nutrients due to exclosures, in turn, increased carbon and nutrient stock. The results support regeneration of degraded landscapes by restoring vegetation, soil fertility, carbon and nutrient stocks in the Northwestern highlands of Ethiopia. However, additional research is required to more accurately quantify these improvements because current research efforts that sample only the surface soils seem to indicate that the capacity of exclosures to increase soil carbon storage is decreasing when annual rainfall is increasing.

Restoration of degraded landscapes for ecosystem services in North-Western Ethiopia.

Establishing exclosures has become common in Ethiopia, especially in the central and northern highlands, where they serve as a response to persistent forest degradation, affecting forest resources and ecosystem services. We investigated changes in vegetation composition, aboveground biomass and soil properties after establishing an exclosure on degraded communal grazing land in Aba-Gerima watershed, North-Western Ethiopia. We selected 4-yr-old exclosure and paired the selected exclosure with an adjacent communal grazing land. In the exclosure, we recorded 46 plant species representing 32 families, whereas we recorded 18 plant species representing 13 families in the adjacent communal grazing lands. Most of the identified woody species are economically important. We observed significant differences between the exclosure and adjacent grazing land in woody species richness, diversity and evenness. Exclosure displayed higher woody species density, basal area and aboveground woody biomass compared to the adjacent grazing land. Landscape position influenced vegetation composition, richness and diversity in the exclosure and adjacent grazing land. Significant differences between the exclosure and adjacent grazing land in soil properties were detected. The influence of landscape positions on soil properties was not consistent. At foot slope position, in the 0- to 15-cm and 15- to 30-cm depths, soil organic carbon and nitrogen content detected in exclosure were significantly higher when compared to the values observed in the adjacent grazing land. However, differences at mid and upper slope positions were not significant. The results support that the establishment of exclosures on degraded lands could support the restoration of degraded native vegetation and soil properties, which consequently enhance the ecosystem services that can be obtained from degraded lands.

Dynamics of land change: insights from a three-level intensity analysis of the Legedadie-Dire catchments, Ethiopia.

Earlier studies on land change (LC) have focused on size and magnitude, gains and losses, or land transfers between categories. Therefore, these studies have failed to simultaneously show the complete LC processes. This paper examines LCs in the Legedadie-Dire catchments in Oromia State, Ethiopia, using land-category maps with intensity analysis (IA) at three points in time. We comprehensively analyze LC to jointly encompass the rate, intensity, transition, and process. Thirty-meter US Geological Survey (USGS) Landsat imagery from 1986, 2000, and 2015 (< 10% cloud) is processed using TerrSet-LCM and ArcGIS. Six categories are identified using a maximum likelihood classification technique: settlement, cultivation, forest, water, grassland, and bare land. Then, classified maps are superimposed on the images to statistically examine changes with an IA. Considerable changes are observed among categories, except for water, between 1986-2000 and 2000-2015. Overall land change occurred quickly at first and then slowly in the second time interval. The total land area that exhibited change (1st ≈ 54% and 2nd ≈ 51%) exceeded the total area of persistence (1st ≈ 46% and 2nd ≈ 49%) across the landscape. Cultivation and human settlements were the most intensively increased categories, at the expense of grassland and bare ground. Hence, when grassland was lost, it tended to be displaced by cultivation more than other categories, which was also true with bare land. Annual intensity gains were active for forest but minimal for cultivation, implying that the gains of forest were associated with in situ reforestation practices and that the gains in cultivation were caused by its relatively large initial area under a uniform intensity concept. This study demonstrates that IA is valuable for investigating LC across time intervals and can help distinguish dormant vs. active and targeted vs. avoided land categories.

Impacts of Soil and Water Conservation Practices on Crop Yield, Run-off, Soil Loss and Nutrient Loss in Ethiopia: Review and Synthesis.

Research results published regarding the impact of soil and water conservation practices in the highland areas of Ethiopia have been inconsistent and scattered. In this paper, a detailed review and synthesis is reported that was conducted to identify the impacts of soil and water conservation practices on crop yield, surface run-off, soil loss, nutrient loss, and the economic viability, as well as to discuss the implications for an integrated approach and ecosystem services. The review and synthesis showed that most physical soil and water conservation practices such as soil bunds and stone bunds were very effective in reducing run-off, soil erosion and nutrient depletion. Despite these positive impacts on these services, the impact of physical soil and water conservation practices on crop yield was negative mainly due to the reduction of effective cultivable area by soil/stone bunds. In contrast, most agronomic soil and water conservation practices increase crop yield and reduce run-off and soil losses. This implies that integrating physical soil and water conservation practices with agronomic soil and water conservation practices are essential to increase both provisioning and regulating ecosystem services. Additionally, effective use of unutilized land (the area occupied by bunds) by planting multipurpose grasses and trees on the bunds may offset the yield lost due to a reduction in planting area. If high value grasses and trees can be grown on this land, farmers can harvest fodder for animals or fuel wood, both in scarce supply in Ethiopia. Growing of these grasses and trees can also help the stability of the bunds and reduce maintenance cost. Economic feasibility analysis also showed that, soil and water conservation practices became economically more viable if physical and agronomic soil and water conservation practices are integrated.