Introduction: Climate change will either improve, reduce, or shift its appropriate climatic habitat of a particular species, which could result in shifts from its geographical range. Predicting the potential distribution through MaxEnt modeling has been developed as an appropriate tool for assessing habitat distribution and resource conservation to protect bamboo species. Methods: Our objective is to model the current and future distribution of Oxytenanthera abyssinica (A. Richard) based on three representative concentration pathways (RCP) (RCP2.6, RCP4.5, and RCP8.5) for 2050s and 2070s using a maximum entropy model (MaxEnt) in Northern Ethiopia. For modeling procedure, 77 occurrence records and 11 variables were retained to simulate the current and future distributions of Oxytenanthera abyssinica in Northern Ethiopia. To evaluate the performance of the model, the area under the receiver operating characteristic (ROC) curve (AUC) was used. Results: All of the AUCs (area under curves) were greater than 0.900, thereby placing these models in the “excellent” category. The jackknife test also showed that precipitation of the coldest quarter (Bio19) and precipitation of the warmest quarter (Bio18) contributed 66.8% and 54.7% to the model. From the area of current distribution, 1367.51 km² (2.52%), 7226.28 km² (13.29%), and 5377.26 km² (9.89%) of the study area were recognized as high, good, and moderate potential habitats of Oxytenanthera abyssinica in Northern Ethiopia, and the high potential area was mainly concentrated in Tanqua Abergele (0.70%), Kola Temben (0.65%), Tselemti (0.60%), and Tsegede (0.31%). Kafta Humera was also the largest good potential area, which accounts for 2.75%. Compared to the current distribution, the total area of the high potential regions and good potential regions for Oxytenanthera abyssinica under the three RCPs (RCP2.6, RCP4.5, and RCP8.5) would increase in the 2050s and 2070s. However, the total area of the least potential regions under the three RCPs (RCP2.6, RCP4.5, and RCP8.5) in 2050s and 2070s would decrease. Conclusion: This study can provide vital information for the protection, management, and sustainable use of Oxytenanthera abyssinica, the resource to address the global climate challenges.

Trees on agricultural landscape play a vital role in ecosystem services including food security that supports human livelihood. They can further offer synergy between adaptation and mitigation in addressing climate change impact. Understanding aboveground tree biomass and soil organic carbon stocks along the altitudinal gradient provide opportunities for better management of the carbon pools. However, little is known on how altitudinal gradient influences on carbon stock of woody biomass and soil of scattered trees on farmland, particularly in a dry area. The study area were stratified in to five class (500–1000, 1000–1500, 1500–2000, 2000–2500, and 2500–3000 m a.s.l). Quadrats (100 m × 50 m) were randomly selected from each of stratified altitudinal gradients. At every sampling point, one composite soil sample was taken at 60 cm soil depth for soil organic carbon analysis. For the purpose of woody biomass estimation, allometric equations developed for a similar area were used. Finally, aboveground biomass carbon (AGC), belowground biomass carbon (BGC), soil organic carbon (SOC), and total carbon stock (TC) status were estimated and variables were compared using one-way analysis of variance (ANOVA). The result indicated that AGC, BGC, SOC, and TC varied significantly (p < 0.05) along with an altitudinal gradient. The upper altitude (2500–3000 m a.s.l) AGC, BGC, SOC, and TC stock was estimated as 17.97 Mg C ha⁻¹, 6.53 Mg C ha⁻¹, 23.09 Mg C ha⁻¹, 47.59 Mg C ha⁻¹ respectively, and significantly higher than the other altitudinal gradient. We conclude that scattered trees on farmland hold a high potential of carbon storage which may greatly contribute to the climate resilience green economy strategy and their conservation should be promoted.

Dispersed trees such as Oxytenanthera abyssinica (A. Rich.) and Dalbergia melanoxylon (Guill. & Perr.) which are objectively maintained or planted on farmland provide a significant contribution to soil fertility improvement. However, there was no quantitative information on the level of soil nutrient additions of these trees to the soil system. This study was conducted on the farmers’ fields in Kafta Humera district, Tigray region (northern Ethiopia), where mature stands of O. abyssinica and D. melanoxylon trees exist. Radial distance-based soil sampling (under the canopy, near to canopy, and far from canopy) was adopted to quantify the role of these trees on soil fertility improvement. Soil parameters tested were soil reaction (pH), total nitrogen (TN), available phosphorus (AvP), electrical conductivity (EC), cation exchange capacity (CEC), and organic carbon (OC). There was a negative linear relationship between the radial distance of the O. abyssinica tree trunk and soil TN, OC, CEC, and AvP contents but not for pH. Similarly, negative linear relationship between distance from D. melanoxylon and TN, OC, and AvP was obtained. The average total nitrogen (0.26% and 0.13%), available phosphorus (7.21 ppm and 6.37 ppm), and organic carbon (1.73% and 1.02%) contents were respectively higher under the tree canopies of O. abyssinica and D. melanoxylon compared with the adjacent open canopies. The amount of soil OC, TN, AvP, and CEC under O. abyssinica tree species was also significantly higher by 69%, 100%, 13%, and 42% compared to that of D. melanoxylon tree species. However, the amount of EC and soil pH was significantly lower by 57% and 19%, respectively. In general, O. abyssinica and D. melanoxylon added a significant amount of nutrients to the soil. Thus, retaining these important tree species on farmland played a positive role in replenishing soil fertility for resource-constrained households so as to reduce chemical fertilizer amendments.

Parkland agroforestry can store carbon and conserves biodiversity. Studying the relationship between carbon stock and biodiversity is crucial in understanding the tradeoff between major benefits of the parkland agroforestry system, and way to achieve the optimum balance between them. Therefore, this study aims to estimate the biomass and SOC in community type, and explore the relationship between carbon stocks and diversity. Tree with DBH (Diameter at breast height) > 2 cm was measured and species were identified in 75 (50x100m) randomly located plots. Species richness (S), Species evenness (J), Shannon-weiner diversity index (H’) and Simpson diversity index (D) of the study area were 3.02, 0.81, 0.82 and 0.46 respectively. Similarly, the mean aboveground (AGC), belowground (BGC) and soil organic (SOC) carbon were 7.9, 3.03 and 20.07 Mg C ha-1 respectively. There was a liner and weakly significant correlation between AGC and tree J in plant community 2 (r = −0.558, P < 0.05) and 3 (r = −0.451, P < 0.05), and there was a negative correlation between J (r = −0.552, P < 0.05), D (r = −0.646, P < 0.05) and H’ (r = −0.643, P < 0.05) with TC (Total carbon) in plant community 2. However, there was no significant relationship between J, D and H’ with TC in plant communities 1 and 3. In these parkland agroforestry systems, the relationship tree species diversity with AGC and TC appeared to be highly variable; it indicates that parkland agroforestry systems have significantly improved the vegetation and SOC. However, forest carbon enhancement cannot assure the biodiversity conservation and promotion in a parkland agroforestry system.

The greatest human impact on the forest ecosystems such as loss of forest area, habitat fragmentation, and soil degradation leads to decline biodiversity. These impacts can be addressed by the integration of trees on the agricultural landscape and maintaining the existing forests. In order to determine woody species diversity and density of tree on farmland in relation to the altitudinal gradient, 75 sample quadrats having an area of 100 m × 50 m, 15 sample quadrats in each range of altitude were measured. The result indicates that a total of 42 woody species belongs to 23 families and Fabaceae were the dominant family. There was a significant difference (P < 0.05) in woody species diversity, richness, evenness, tree density and the basal area between the altitudinal gradient ranges. Woody species richness (4.00), diversity indexes (1.11) and tree density (21.34) were higher in the middle altitude (1500–2000 m a.s.l). However, woody species evenness index (0.91) and the basal area (0.80) were highest in the 2000–2500 and 2500–3000 m a.s.l, respectively. Acacia abyssinica subsp. Abyssinica, Croton macrostachyus, and Cordia Africana were found to have the highest IVI (importance value index). Boswellia papyrifera, Acacia abyssinica subsp. Abyssinica and Diospyros mespiliformis were found to have the highest density. It can be generally concluded that the indigenous agricultural practices have been one way of diversifying agroecosystem in a way that has positive effects on ecological stability and can conserve species diversity.