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Avocado (Persea americana Mill.) is an important horticultural crop and proved to be a very profitable commercial crop for both local consumption and export. The physical characteristics of fruits are an important factor to determine the quality of fruit produced. On the other hand, estimation of fruit volume is time-consuming and impractical under field conditions. Thus, this study was conducted to devise cultivar-specific and generalized allometric models to analytically and non-destructively determine avocado fruit volume of five wildly distributed avocado cultivars. A significant relationship (P ≤ 0.01) was found between fruit diameter, length, and volume of each cultivar. Our best models (VM2 –for cultivar specific, and VM7-generalized model) has passed all the rigorous cross-validation and performance statistics tests and explained 94%, 92%, 87%, 93%, 94% and 93% of the variations in fruit volume of Ettinger, Fuerte, Hass, Nabal, Reed, and Multiple cultivars, respectively. Our finding revealed that in situations where measurements of volume would be inconvenient, or time-consuming, a reliable volume and yield estimation can be obtained using site- and cultivar-specific allometric equations. Allometric models could also play a significant role in improving data availability on avocado fruit physical appearance which is critical to assess the quality and taste of fresh products influencing the purchase decision of customers. Moreover, such information can also be used as a ripeness index to predict optimum harvest time important for planned marketing. More importantly, the models might assist horticulturists, agronomists, and physiologists to conduct further study on avocado production and productivity through agroforestry landuse system across Ethiopia. [ABSTRACT FROM AUTHOR]

The Modjo watershed has experienced significant land use/land cover (LULC) change and soil erosion. This study examines changes in surface runoff generation and soil erosion in response to the LULC dynamics. To simulate runoff and sediment yield, the geographic information system-interfaced Soil and Water Assessment Tool (SWAT) model was used. Model sensitivity, calibration and validation analyses were carried out, and the efficiency of the model was evaluated using simulated and measured discharge data. The two scenario model simulation goodness-of-fit measures verified that the SWAT model performed very well during calibration and validation periods for daily and monthly time steps (Nash-Sutcliffe efficiency > 0·79 and root mean square error-observation standard deviation ratio < 0·4). Although the computed values of per cent bias fulfilled a satisfactory standard (greater than −11·8%), the model results tended to overestimate discharge. Consequent to the LULC change, an overall increase in the amount of surface runoff (14·2%) and sediment yield (37%) was observed relative to the baseline (1973) simulation scenario. Mean annual soil loss rate was estimated at 24·2 Mg ha−1 y−1. Nearly 95·2% of the watershed is experiencing moderate to severe soil loss rates ranging from 14·7 to 37·5 Mg ha−1 y−1. In the remaining parts of the watershed, soil loss rates range from 4·4 to 14·7 Mg ha−1 y−1. Surface runoff generation and soil erosion varied widely by soil, LULC types and slope positions. The observed environmental change would lead to further land degradation, with negative implications on the livelihoods of local people unless appropriate conservation measures are implemented. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Extreme climatic events such as droughts are likely to result in huge and long-lasting effects on regional ecosystem health if large numbers of foundation tree species continue to die. Although deforestation is severe in the Ethiopian highlands, some remnants of dry afromontane forests still exist. However, the resilience of these forests under climate change scenarios is unknown. Therefore, we studied (1) the extent and spatial patterns of standing dead stems along an elevational gradient and (2) the effects of dieback on forest carbon sequestration potential and aboveground carbon stocks, in Juniperus procera and Olea europaea dominated dry afromontane forest in northern Ethiopia, using allometric models combined with tree ring analysis. Juniperus procera and Olea europaea constitute 67% of the total tree population. Tree dieback affected a quarter of the total population. This loss is critical because 92.2% of snags belong to J. procera and O. europaea , which are the foundation species of the study forest. The total estimated mean aboveground C-stock was 19.3 (±3.9) Mg C ha −1 . Of this estimate, snags contributed 34.5% of total C-stock. The estimated annual C-sequestration potential of the study forest was 0.33 (±0.03) Mg C ha −1 year −1 , which is 27% less when compared to the pre-tree dieback C-sequestration potential. We found a decreasing trend in tree dieback with increasing elevation, which implies that the aboveground C-stocks and climate change mitigation potentials of the forest, was highly affected at lower elevations which is the drier part of the landscape. Tree ring analysis showed that trees reach medium-sized stem diameter (i.e., 20–25 cm) after no less than 100 years, indicating that the effect of forest dieback on C-sequestration potential and ecosystem function is long-lasting. Our results provide information on the magnitude of tree dieback and its long-lasting impact on forest carbon fluxes and forest ecosystem services. Evidently, the results substantiate the importance of protecting such forest to maintain the quality of the environment and to reduce efforts and cost for forest restoration after major loss. Finally, the information gained by this study provides baseline information for comparison of future carbon sequestration estimates. [ABSTRACT FROM AUTHOR]

We present an intra-annual stable carbon isotope (δ13C) study based on a labeling experiment to illustrate differences in temporal patterns of recent carbon allocation to wood structures of two functional types of trees, Podocarpus falcatus (a late-successional evergreen conifer) and Croton macrostachyus (a deciduous broadleaved pioneer tree), in a tropical mountain forest in Ethiopia., Dendrometer data, wood anatomical thin sections, and intra-annual δ13C analyses were applied., Isotope data revealed a clear annual growth pattern in both studied species. For P. falcatus, it was possible to synchronize annual δ13C peaks, wood anatomical structures and monthly precipitation patterns. The labeling signature was evident for three consecutive years. For C. macrostachyus, isotope data illustrate a rapid decline of the labeling signal within half a year., Our δ13C labeling study indicates a distinct difference in carryover effects between trees of different functional types. A proportion of the labeled δ13C is stored in reserves of wood parenchyma for up to 3 yr in P. falcatus. By contrast, C. macrostachyus shows a high turnover of assimilates and a carbon carryover effect is only detectable in the subsequent year. [ABSTRACT FROM AUTHOR]

Abstract: Podocarpus falcatus is an indigenous evergreen conifer species of tropical mountain forests in southeastern Ethiopia, showing potential tree ages of around 500 years. To study the influence of seasonal climate on the growth pattern of P. falcatus, we combined high-resolution electronic dendrometer measurements with wood anatomical investigations of microcores from the outermost stem parts collected in monthly intervals. At any time of the year sufficient rain events are able to cause cambial activity in P. falcatus. This permanent growing readiness leads to irregular wood formation with the formation of intra-annual density fluctuations and missing rings. Wood anatomical studies of microcores collected around the circumference of a mature P. falcatus revealed locally different activity status of the cambium on different lobes of the stem. Tree-ring width measurements of stem disks resulted in tentative tree ages that were confirmed by radiocarbon dating of selected wood samples. Although our efforts to cross-date ring-width series from several stem disks were not successful, further sampling in areas with different rainfall regimes, additional radiocarbon dating and measurements of stable isotopes hopefully would enable the establishment of a multi-century-long tree-ring series for climate reconstruction. [Copyright &y& Elsevier]

Reforestation and afforestation either through natural regeneration, tree planting or both methods have been globally promoted to motivate ecological restoration of degraded lands and to improve livelihoods. However, moisture stress and infertile soils limit the survival and growth of trees planted for restoration in drier areas. Hence, understanding the factors that determine the restoration success of drylands through tree planting is critical. We conducted a factorial experiment in Tigray, Ethiopia to evaluate the survival, growth performance and biomass of planted seedlings of the multipurpose agroforestry tree species Acacia saligna over 24 months. The treatments were application of watering (W), mulching (M) and compost (C) separately and in combinations (WM, WMC). We established experimental plots on farmland and on a nearby hillside-exclosure to examine the role of planting niches on seedling performance. Seedlings treated with watering, mulching, and compost (WMC) revealed significantly greater height, root collar diameter (RCD), and dry biomass compared to the other treatments. Seedlings planted in farmland showed significantly greater height, RCD, and total dry biomass compared to those planted at the hillside-exclosure. Although the survival rate was slightly higher in farmland, we also found sufficient survival rates in the hillside-exclosures. Therefore, post-planting care and activities including mulching, watering and fertilization are crucial to enhance the survival and growth performance of A. saligna or other tree species so that efforts in reversing land degradation and restoration of drylands will be successful., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)