Emiru Birhane

The Potential Role of Arbuscular Mycorrhizal Fungi in the Restoration of Degraded Lands.

Experiences worldwide reveal that degraded lands restoration projects achieve little success or fail. Hence, understanding the underlying causes and accordingly, devising appropriate restoration mechanisms is crucial. In doing so, the ever-increasing aspiration and global commitments in degraded lands restoration could be realized. Here we explain that arbuscular mycorrhizal fungi (AMF) biotechnology is a potential mechanism to significantly improve the restoration success of degraded lands. There are abundant scientific evidences to demonstrate that AMF significantly improve soil attributes, increase above and belowground biodiversity, significantly improve tree/shrub seedlings survival, growth and establishment on moisture and nutrient stressed soils. AMF have also been shown to drive plant succession and may prevent invasion by alien species. The very few conditions where infective AMF are low in abundance and diversity is when the soil erodes, is disturbed and is devoid of vegetation cover. These are all common features of degraded lands. Meanwhile, degraded lands harbor low levels of infective AMF abundance and diversity. Therefore, the successful restoration of infective AMF can potentially improve the restoration success of degraded lands. Better AMF inoculation effects result when inocula are composed of native fungi instead of exotics, early seral instead of late seral fungi, and are consortia instead of few or single species. Future research efforts should focus on AMF effect on plant community primary productivity and plant competition. Further investigation focusing on forest ecosystems, and carried out at the field condition is highly recommended. Devising cheap and ethically widely accepted inocula production methods and better ways of AMF in situ management for effective restoration of degraded lands will also remain to be important research areas.

Land Use and Land Cover Change, and Woody Vegetation Diversity in Human Driven Landscape of Gilgel Tekeze Catchment, Northern Ethiopia

Land use and land cover (LULC) change through inappropriate agricultural practices and high human and livestock population pressure have led to severe land degradation in the Ethiopian highlands. This has led to further degradation such as biodiversity loss, deforestation, and soil erosion. The study examined woody vegetation diversity status and the impact of drivers of change across different LULC types and agroecological zones in Gilgel Tekeze catchment, northern Ethiopian highlands. LULC dynamics were assessed using GIS techniques on 1976, 1986, and 2008 satellite images. Vegetation data were collected from 135 sample plots (20 m × 20 m) from five LULC types, namely, forest, shrub-bush, grazing, settlement, and cultivated land, in the three agroecological zones; Kolla, Weyna-Dega, and Dega. Differences in vegetation structure and composition and their relationship to agroecological zones were tested using two-way ANOVA and PCA technique. The results show that vegetation structure and composition significantly differed across all LULC types in different agroecological zones particularly in sapling density, tree height, and shrub height and in each agroecological zone between forest land, shrub-bush land, and settlement area. Overall, Weyna-Dega agroecological zone and the shrub-bush land had more structural and compositional diversity than the other agroecological zones and LULC types.

Climatic controls of ecohydrological responses in the highlands of northern Ethiopia

Climate variability and recurrent droughts have a strong negative impact on agricultural production and hydrology in the highlands northern Ethiopia. Since the 1980s, numerous mitigation and land rehabilitation measures have been implemented by local and national authorities to reduce these impacts, are often poorly effective. As underlying reason may be that controlling relationships between climate and ecohydrology at medium-sized catchments (10-10,000km2) of semi-arid highlands are not well known. We investigated trends and relationships in precipitation, temperature, streamflow, and net primary productivity (NPP). The results were mixed, with both significant increasing and decreasing trends for temperature and streamflow. Precipitation time series did not show a significant trend for the majority of stations, both over the years and over each season, except for a few stations. A time series indicated a significant abrupt increase of NPP in annual, seasonal and monthly timescale. Cross-correlation and regression analysis indicate precipitation and maximum temperature were the dominant climatic variables in the Geba catchment for streamflow and NPP. In view of these results, also land use and land cover change over the past three decades was analysed as a possible factor of importance, as human intervention, may affect streamflow and NPP. Factors that mainly correlate with streamflow and NPP are precipitation and maximum temperature. Important interventions that appear beneficial for these responses are construction of micro-dams, soil and water conservation and ecological restoration measures. The awareness that interactions can be quite different in semi-arid and semi-humid regions, as well as in upstream and downstream areas, should be reflected in management aimed at sustainable water and land resources use.

Arbuscular mycorrhiza and water and nutrient supply differently impact seedling performance of dry woodland species with different acquisition strategies

Background: Arbuscular mycorrhizal (AM) fungi increase seedling survival and performance through enhancement of nutrient and water uptake under stress conditions. Acacia etbaica, A. senegal and Boswellia papyrifera dominate large areas in African drylands where both moisture and nutrients are limited. Aims: We evaluated the effects of AM, drought and soil quality on carbon gain (growth), gas exchange and nutrient contents of seedlings of these three dry woodland species. Methods: We used a greenhouse experiment with a fully factorial design of two levels of AM, two levels of soil and four levels of water availability, on the carbon gain, gas exchange and nutrient content of seedlings of the three species. Results: AM symbiosis enhanced the acquisition of water and nutrients and increased gas exchange resulting in increased Acacia and Boswellia seedling biomass. The rapidly growing Acacia species (acquisitive strategy) showed larger mycorrhizal benefit at higher water availability. The slow-growing Boswellia (conservative strategy), in contrast, showed larger mycorrhizal benefit at lower water availability. Conclusions: This study showed that different species of dry woodlands benefit from AM in different ways depending on the resource use strategy under stress conditions. The inclusion of the mycorrhizal habit in trait-based approaches increases understanding of functional differences of coexisting tree species.

Transformation of degraded farmlands to agroforestry in Zongi Village, Ethiopia

The interaction of human land use, steep slopes and erosion has been a serious threat to Ethiopia’s ecosystems. Community’s initiated land rehabilitation programmes such as tree regeneration on farm lands, hill-side planting and exclosures have been established to rejuvenate debilitated lands. To characterize, map out and monitor such transformations, this study was carried out in Zongi, Tigray Region of northern Ethiopia. The study used an integration of remote sensing data, field observations and information from key informants and randomly selected respondents to analyse the land-use/land cover (LULC) changes from 1984 to 2013. Conventional method of supervised image classification was used for landsat image of 2013 while hybrid method of unsupervised and supervised classification was employed for landsat images of 1984 and 1999. The results revealed significant modifications and conversion of LULC types over the multi-dates. Analysis of the 29-year change matrix revealed that 78.5% of the land underwent significant changes in LULC. The major changes to agroforestry land use(LU)types between 1984 and 2013 were conversion of intensively cultivated land to moderately cultivated land (32.1%) and sparsely cultivated land (11.8%). The drivers of changes were linked to the introduction of land rehabilitation initiatives, government consensus (via agricultural extension) with the community, which were complemented by growing awareness of landowners. This study corroborates the necessity of community involvement and participation to improve their land use systems for environmental sustainability and sustainable livelihood.

Predicting suitable habitats of endangered Juniperus procera tree under climate change in Northern Ethiopia

ABSTRACT Juniperus procera is the most preferred tree in Ethiopia. It is an endangered tree species enumerated in IUCN red list. Accordingly, this study investigates the future suitable habitat of the J. procera under climate change in northern Ethiopia. Three occurrence districts were visited and 124 presence observations were taken. The records, altitude, and 19 bio-climatic variables were used to run a species distribution model to account for the climate change effect on the species. Maxent, Diva-GIS, and ArcGIS were used to evaluate the outputs. Future suitable habitats were projected into mid and end-century time frames with two Representative Concentration Pathways (RCP2.6 and 8.5) under one General Circulation Model, namely the Climate Community System Model Version-4. Our results showed that minimum temperature of the coldest month and altitude are main predictors of the distribution of the species. Suitable habitats of the species will be decreased by 79.84%, 91.17%, 75.31%, and 96.25% in Mid-century RCP2.6, Mid-century RCP8.5, End-century RCP2.6, and End-century RCP8.5 when compared with current distributions, respectively. This indicates that climate change will affect the future distribution of the species. The results of the study indicate that appropriate management strategies must be taken to ensure the long-term survival of J. procera.

Source of mycorrhizal inoculum influences growth of Faidherbia albida seedlings

Poor land use management and practice inhibit the growth and establishment of tree seedlings in dryland areas. We assessed arbuscular mycorrhizal fungi (AM) status of Faidherbia albida (Del.) A. Chev. trees grown on different land uses. We quantified the growth and nutrient uptake of F. albida seedlings inoculated with AM from different sources. These efforts were based on soil and fine root samples from the rhizosphere soils of F. albida trees. AM root colonization was determined using the gridline intersect method. Spores were extracted by the wet sieving and decanting method and identified to genus level. The seedling experiment had a completely randomized one-factorial design with four treatments and five replications. Faidherbida albida seedlings were grown in a greenhouse. All in situ F. albida trees were colonized by AM fungi. AM root colonization of F. albida trees was significantly higher (P < 0.0086) in area exclosures than on lands used for grazing or cultivation. Spore abundance was significantly higher (P < 0.0014) in area exclosures followed by cultivated land and grazing land. Glomus was the dominant genus in all land-uses. AM-inoculated F. albida seedlings grew better (P < 0.05) than non-inoculated controls. Seedlings inoculated with AM from area exclosure had significantly (P < 0.05) higher growth and nutrient uptake than those inoculated with AM from grazing and cultivated land. This emphasizes the importance of the native soil AM potential for better establishment of seedlings to achieve optimum plant growth improvement and assist in rehabilitation of degraded arid lands.

Performance of Some Agroforestry Trees in Reclamation of Salt-affected Soils in the Lowlands of Ethiopia

To determine the performance of some agroforestry trees in the reclamation of salt-affected soils in the lowlands of Ethiopia, we studied the effects of a series of soils with differing levels of salinity on three indigenous tree species, Balanites aegyptiaca, Tamarindus indica, and Acacia tortilis. We found that salinity had a significant effect on seedling performance. Increasing the soil salt levels caused a significant reduction in the height and in the dry stem and dry root weights of the three species tested. Based on seedling growth parameters, B. aegyptiaca was salt-tolerant even at a high level of salinity (12 dS m−1), while T. indica was moderately salt-tolerant. Salinity had a significant effect on soil compared with control soil in the trees’ response to soil chemical properties. At the seedling stage, B. aegyptiaca and T. indica were found to be the most efficient salt cleansers compared with A. tortilis. Salinity and the interaction between species and salinity level had a significant effect on all seedling growth parameters and soil chemical properties, indicating that salinity was a limiting factor for plant growth. Salinity had a significant effect on the productivity index. A. tortilis and B. aegyptiaca contributed more to soil productivity improvement than T. indica. Further, at the top (0–50 cm) soil depth, the base of the trees had a higher soil productivity index than other soil radii. A. tortilis was found to be the most salt-tolerant and this species showed the most potential for the improvement of soil productivity, followed by B. aegyptiaca and T. indica. Therefore, we suggest that A. tortilis and B. aegyptiaca are suitable for reclamation in arid and semi-arid areas where salinity affects crop development, in both agroforestry systems and strip tree plantings.

Biodiversity Conservation in Dryland Parkland Agroforestry Practice: A Review

The conservation of biodiversity has been mostly understood in terms of the management of protected areas and natural forests, ignoring the possible role of farm areas and the ways through which dryland communities have promoted biodiversity in their agroforestry system and/or practices. Dryland biodiversity have developed unique strategies to cope with low and erratic rainfall. They are highly resilient and recover quickly from existing disturbances against risks such as drought, disease, and crop failure. These attributes have great significance for the global system, especially in the context of climate change. Dryland people have adapted many agroforestry systems and/or practices, which help them to conserve biodiversity and improve their livelihood.