In the central and northern highlands of Ethiopia, native forest and forest biodiversity is almost confined to sacred groves associated with churches. Local communities rely on these 'church forests' for essential ecosystem services including shade and fresh water but little is known about their region-wide distribution and conservation value. We (1) performed the first large-scale spatially-explicit assessment of church forests, combining remote-sensing and field data, to assess the number of forests, their size, shape, isolation and woody plant species composition, (2) determined their plant communities and related these to environmental variables and potential natural vegetation, (3) identified the main challenges to biodiversity conservation in view of plant population dynamics and anthropogenic disturbances, and (4) present guidelines for management and policy. The 394 forests identified in satellite images were on average ~2ha in size and generally separated by ~2km from the nearest neighboring forest. Shape complexity, not size, decreased from the northern to the central highlands. Overall, 148 indigenous tree, shrub and liana species were recorded across the 78 surveyed forests. Patch α-diversity increased with mean annual precipitation, but typically only 25 woody species occurred per patch. The combined results showed that >50% of tree species present in tropical northeast Africa were still present in the 78 studied church forests, even though individual forests were small and relatively species-poor. Tree species composition of church forests varied with elevation and precipitation, and resembled the potential natural vegetation. With a wide distribution over the landscape, these church forests have high conservation value. However, long-term conservation of biodiversity of individual patches and evolutionary potential of species may be threatened by isolation, small sizes of tree species populations and disturbance, especially when considering climate change. Forest management interventions are essential and should be supported by environmental education and other forms of public engagement.

Farmers in Northern Ethiopia integrate legumes in their cropping systems to improve soil fertility. However, biological nitrogen fixation (BNF) potentials of different legumes and their mineral nitrogen (N) and phosphorus (P) demands for optimum BNF and yields are less studied. This study aimed to generate the necessary knowledge to enable development of informed nutrient management recommendations, guide governmental public policy and assist farmer decision making. The experiment was conducted at farmers’ fields with four N levels, three P levels, and three replications. Nodule number and dry biomass per plant were assessed. Nitrogen difference method was used to estimate the amount of fixed N by assuming legume BNF was responsible for differences in plant N and soil mineral N measured between legume treatments and wheat. The result revealed that the highest grain yields of faba bean (2531 kg ha⁻¹), field pea (2493 kg ha⁻¹) and dekeko (1694 kg ha⁻¹) were recorded with the combined application of 20 kg N ha⁻¹ and 20 kg P ha⁻¹. Faba bean, field pea and dekeko also fixed 97, 38 and 49 kg N ha⁻¹, respectively, with the combined application of 20 kg N ha⁻¹ and 20 kg P ha⁻¹; however, lentil fixed 20 kg ha⁻¹ with the combined application of 10 kg N ha⁻¹ and 10 kg P ha⁻¹. The average BNF of legumes in the average of all N and P interaction rates were 67, 23, 32 and 16 kg N ha⁻¹ for faba bean, field pea, dekeko and lentil, respectively. Moreover, faba bean, field pea, dekeko and lentil accumulated a surplus soil N of 37, 21, 26 and 13 kg ha⁻¹, respectively, over the wheat plot. The application of 20 kg N ha⁻¹ and 20 kg P ha⁻¹ levels alone and combined significantly (p < 0.05) increased the nodulation, BNF and yield of legumes; however, 46 kg N ha^-1 significantly decreased BNF. This indicated that the combination of 20 kg N ha⁻¹ and 20 kg P ha⁻¹ levels is what mineral fertilizer demands to optimize the BNF and yield of legumes. The results of this study can lead to the development of policy and farmer guidelines, as intensification of the use of legumes supplied with starter N and P fertilizers in Northern Ethiopian cropping systems has the multiple benefits of enhancing inputs of fixed N, improving the soil N status for following crops, and becoming a sustainable option for sustainable soil fertility management practice.

Due to the nature of available land as one of the main attractions for investment, land lease marketing in Sub-Saharan Africa is appearing on policy agenda. This paper describes critical land-related institutional and governmental frameworks that have shaped the contemporary land governance and land lease contracts in Ethiopia. It also examines the effectiveness of the land lease process regarding economic, social, and environmental expectations from agricultural outsourcing. Both qualitative and quantitative data analyses were used and results showed that the size of the land cultivated by investors is significantly lower than the agreed-upon size in the contract. Besides, the supply of land to large-scale commercial investors in Ethiopia is made without adequate land use planning, land valuation, and risk analysis. Furthermore, limitations in monitoring systems have contributed to meager socio-economic gains and led to deforestation. Accordingly, the study concludes that supplying vast tracts of farmland to large-scale agricultural investors requires integrated land use planning, land valuation and governance, monitoring systems, and a capacity to implement the various social and environmental laws in coordination with other sectors. Improving rural infrastructure, particularly road, is also indispensable to enhance the level of performance of commercial farms. Last but most importantly, the customary land holding rights of residents should be respected and institutionally recognized.

Soil Organic carbon (SOC) is vital to the soil’s ecosystem functioning as well as improving soil fertility. Slight variation in C in the soil has significant potential to be either a source of CO₂ in the atmosphere or a sink to be stored in the form of soil organic matter. However, modeling SOC spatiotemporal changes was challenging due to lack of data to represent the high spatial heterogeneity in soil properties. Less expensive techniques, digital soil mapping (DSM) combined with space-for-time substitution (SFTS), were applied to predict the present and projected SOC stock for temperature and rainfall projections under different climate scenarios represented by the four Representative Concentration Pathways (RCPs): RCP2.6, RCP4.5, RCP6, and RCP8.5). The relationship between environmental covariates (n = 16) and measured SOC stock (148 samples) was developed using a random forest model. Then, the temporal changes in SOC stock over the baseline were developed for the top 30 cm soil depth of the selected districts (Chiro Zuria, Kuni, Gemechis and Mieso) of West Hararghe Zone at 30 m resolution. The model validation using the random sample of 20% of the data showed that the model explained 44% of the variance (R²) with a root mean square error (RMSE) of 8.96, a mean error (ME) of 0.16, and a Lin’s concordance correlation coefficient (CCC) of 0.88. Temperature was the most important predictor factor influencing the spatial distribution of SOC stock. An overall net gain of SOC stock over the present C stock was expected in the study area by 2050. The gain in areas with the lower baseline SOC stock counterbalanced the loss in areas with the higher baseline stock. The changes in the SOC stock depended on land use land cover (LULC), soil type, and agro-ecological zones. By 2050, cropland is supposed to lose its SOC stock under all RCPs; therefore, appropriate decisions are crucial to compensate for the loss of C.

Soil erosion is a major driver of land degradation in mountainous semi-arid regions. In northern Ethiopia, integrated biophysical soil and water conservation (SWC) measures have been implemented to reduce erosion and improve soil quality. However, little is known about how these measures interact with slope position, soil depth, and proximity to conservation structures, limiting evidence-based strategies for optimizing SWC and promoting climate-resilient land management. This study assessed the effects of SWC on soil properties across slope positions, soil depths, and distances from SWC structures. 96 composite soil samples were collected using a factorial randomized complete block design: (i) management (treated vs. untreated) × slope position × soil depth × replication (48 samples) and (ii) distance from SWC structures × slope position × soil depth × replication (48 samples). Data analyzed using ANOVA with Tukey’s HSD in R (v4.2.3), at P < 0.05. Treated plots significantly improved key soil properties than untreated areas. Bulk density decreased by up to 6% in conserved plots (lowest 1.56 g/cm³ at lower slopes) versus untreated plots (highest 1.66 g/cm³ at upper slopes). Soil moisture content was 67% higher in treated lower-slope plots at 30–60 cm depth (7.99%) than in untreated upper-slope plots (4.77%). Water-stable aggregates increased by 28% in treated plots (64.03% at 0–30 cm depth) relative to untreated areas (50.16%). Interactions among management, slope, and soil depth were significant for moisture and aggregates (P < 0.001), indicating landscape-dependent SWC effectiveness. Soil organic matter correlated positively with available phosphorus (r = 0.648**, P < 0.01), total nitrogen, water-stable aggregates, and pH, and negatively with bulk density (r = -0.729**, P < 0.001). Results indicate that SWC plays a central role in improving soil fertility, structure, and water retention. These findings show that integrated SWC measures quantitatively enhance soil nutrient availability, reduce compaction, and improve moisture retention, providing a robust basis for vegetation recovery, productivity, and climate resilience in degraded hillside landscapes. While limited to short-term observations in selected sub-watersheds, longer-term monitoring across diverse sites, including biological, hydrological, and socio-economic factors, will strengthen evidence-based guidance for scalable, climate-resilient land management.

Faidherbia albida can enhance the bio-physicochemical fertility of inherently infertile Arenosols. Changes in the soil ammonium (NH₄⁺)-to-nitrate (NO₃⁻) ratio have agricultural, environmental, and ecological implications. Thus, the present study mainly examined the changes in Arenosol NH₄⁺/NO₃⁻ ratios, as influenced by varying Faidherbia albida tree age classes. We collected 40 composite soil samples (4 tree age classes^×2 soil depths^×5 replications) from 0 to 15 and 15 to 30 cm soil depths following core and auger sampling techniques. Analyses of variance have shown that the highest NH₄⁺/NO₃⁻ ratios for soil under the old tree canopies are followed by the medium age. In contrast, the significantly lowest NH₄⁺/NO₃⁻ ratios were recorded for soil out-of-canopy. Pearson correlation analysis revealed that the NH₄⁺/NO₃⁻ ratio was strongly and positively correlated with clay content, total nematode abundance, the fungi/bacterial biomass ratio, cation exchange capacity, microbial biomass carbon, total nitrogen, and soil organic carbon but negative for sand content, bulk density, and pH. The increment in the plant-available forms of nitrogen might be attributed to the accumulation of biologically fixed nitrogen by the Faidherbia albida tree–Rhizobium bacteria symbiosis. The NH₄⁺/NO₃⁻ ratio approached one in soil under the old Faidherbia albida trees. The findings suggest that (1) the ability of soil to retain NH₄⁺ increased and (2) the rate of nitrification might be decreased due to inhibition of nitrification by direct and indirect effects of the tree on the nitrifying group of bacteria. The increment in the NH₄⁺/NO₃⁻ ratio could also be due to the lowering of the soil’s pH in the older Faidherbia albida trees because lower pH is known to inhibit the activities of nitrifying bacteria. Moreover, maintaining older Faidherbia albida trees in farmlands could contribute to retaining nitrogen and trigger below- and above-ground communities’ successions and ultimately surpass the productivity of arid and semi-arid Arenosols.