Detection ofOlea europaeasubsp.cuspidataandJuniperus procerain the dry Afromontane forest of northern Ethiopia using subpixel analysis of Landsat imagery

Hishe, Hadgu; Giday, Kidane; Neka, Mulugeta; Soromessa, Teshome; Orshoven, Jos Van; Muys, Bart

doi:10.1117/1.jrs.9.095975

“…Desa'a forest is located 60 km northeast of Mekelle, the capital city of the Tigray region, Ethiopia. The total forest area is estimated to be 120,026 ha [30]. The forest is located in two administrative regions, namely Tigray and Afar, with the majority of the forest residing in the Tigray region ( Figure 1).…”

Section: Site Descriptionmentioning

confidence: 99%

Allometric Models for Predicting Aboveground Biomass of Trees in the Dry Afromontane Forests of Northern Ethiopia

Tetemke

¹

,

Birhane

²

,

Rannestad

³

et al. 2019

Forests

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Dry Afromontane forests form the largest part of the existing natural vegetation in Ethiopia. Nevertheless, models for quantifying aboveground tree biomass (AGB) of these forests are rare. The objective of this study was, therefore, to develop local multispecies and species-specific AGB models for dry Afromontane forests in northern Ethiopia and to test the accuracy of some potentially relevant, previously developed AGB models. A total of 86 sample trees consisting of ten dominant tree species were harvested to develop the models. A set of models relating AGB to diameter at breast height (DBH) or at stump height (DSH), height (H), crown area (CA), and wood basic density (ρ) were fitted. Model evaluation and selection was based on statistical significance of model parameter estimates, relative mean root-square-error (rMRSE), relative bias (rBias), and Akaike Information Criterion (AIC). A leave-one-out cross-validation procedure was used to compute rMRSE and rBias. The best multispecies model, which includes DSH, CA, and ρ as predictors, explained more than 95% of the variability in AGB. The best species-specific models for the two dominant species, with DBH or DSH as the sole predictor, also explained more than 96% of the variability in AGB. Higher biases from the previously published models compared to the best models from this study show the need to develop local models for more accurate biomass estimation. The developed models allow to quantify AGB with a high level of accuracy for our site, and they can potentially be applied in dry Afromontane forests elsewhere in Ethiopia if species composition and growing conditions are carefully evaluated before an application is done.

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“…1), between 39 4 0 E and 13 4 0 N, and has an area of approximately 154,000 ha. The area is reported as 120,000 ha in several studies (Hishe et al 2015a(Hishe et al , 2015b, which ignored a significant amount of forest area to the north.…”

Section: Study Areamentioning

confidence: 99%

Environmental and anthropogenic factors affecting natural regeneration of degraded dry Afromontane forest

Hishe

¹

,

Giday

²

,

Fremout

³

et al. 2021

Restoration Ecology

Self Cite

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Natural regeneration of trees may provide a cost‐effective way to restore degraded tropical dry forests, but the factors predominantly affecting natural regeneration success are poorly understood. We performed a multifactor analysis of natural regeneration in an Afromontane forest in Northern Ethiopia. Inventory plots of 400 m2, each with a nested 9 m2 subplot, were systematically established. All trees larger than 5 cm DBH and natural regeneration were identified and recorded in the plots and subplots, respectively. Variables describing climate, topography, soil, vegetation, and indications of local human degradation were collected. Determinants of regeneration presence and abundance were analyzed using Hurdle negative binomial regressions. Sixty‐nine woody species were represented in the regeneration, with an average regeneration density (SE) of 14,700 (51) ha−1. The presence of regeneration was positively associated with canopy cover (p < 0.001), distance to the road network (p = 0.04), precipitation (p = 0.003) and tree species diversity (p = 0.03), and negatively with Northing (p = 0.003). The regeneration abundance was positively associated with soil quality (p = 0.001), canopy cover (p = 0.04), and precipitation (p = 0.01). Including the abundance of dominant species in the tree canopy and regeneration layers in the regression model did not affect the presence of natural regeneration, but it clearly affected regeneration abundance. In such a model, the regeneration abundance was positively associated with Euclea racemosa seedlings abundance and negatively associated with the basal area of Dodonaea angustifolia (p = 0.02) and Rhus natalensis (p = 0.04). In this model, forest degradation (p = 0.01) negatively affected the late‐successional species regeneration but not the regeneration of the drought‐resistant light‐demanding species. The low representation of late‐successional trees species in the natural regeneration calls for active restoration intervention.

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“…It touches Atsbi-Womberta and Enderta districts from Tigray and Kuneba and Abala from Afar regional states. e total area of the forest is about 120,026 ha [27].…”

Section: Study Sitementioning

confidence: 99%

Carbon Stock and Soil Characteristics under Expansive Shrubs in the Dry Afromontane Forest in Northern Ethiopia

Haile

¹

,

Birhane

²

,

Rannestad

³

et al. 2021

International Journal of Forestry Research

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Increased presence of expansive plant species could bring about various ecological influences on biomass carbon, soil organic carbon, and the physical and chemical properties of the soils. However, their impacts on these ecological parameters could differ due to a wide range of life forms, plant communities of the invaded ecosystems, and abiotic conditions. This work was conducted to examine the impacts of Cadia purpurea and Tarchonanthus camphoratus cover on carbon stock in vegetation and soil and soil physicochemical properties in Desa’a forest, northern Ethiopia. Vegetation and soil data were collected from a total of 150 sampling plots (size 20 m × 20 m) from uninvaded and invaded vegetation conditions. The soil samples were collected from topsoil (0–15 and 15–30 cm) of the uninvaded and invaded vegetation conditions. The statistical difference in carbon stock and soil characteristics P < 0.05 of both invaded and uninvaded vegetation conditions were tested using an independent t-test using an R-software. The mean above- and below-ground biomass carbon stocks of the uninvaded vegetation condition (17.62 Mg·C/ha and 4.14 Mg·C/ha, respectively) were found to be significantly higher than those of the invaded vegetation condition (4.73 Mg·C/ha and 1.11 Mg·C/ha, respectively). The mean soil organic carbons (SOC) were significantly higher P < 0.01 in the uninvaded (122.83 Mg·C/ha) than in the invaded (90.13 Mg·C/ha) vegetation condition. The total carbon stock estimates were significantly higher P < 0.01 in the uninvaded vegetation condition (144.59 Mg·C/ha) than in the invaded vegetation condition (95.97 Mg·C/ha). Furthermore, the result revealed that most of the soil characteristics were significantly lower P < 0.05 under the expansive shrubs invaded vegetation conditions except for significantly high sand content P < 0.05 . Silt, nitrogen, phosphorus, calcium, copper, and zinc did not significantly change with the cover of the expansive shrubs. Our results suggest that increased presence of the expansive species decreased carbon trapping and affected most of the soil nutrients within the forest. Hence, to enhance the carbon storage potential and to maintain the soil nutrient status of the forest, proper conservation, monitoring, and management of the existing PNV and controlling a further expansion of the expansive shrubs are required. Further studies will be required on the factors responsible for the difference in carbon stocks and soil nutrients in each vegetation condition in addition to the impacts of the expansive shrubs expansion.

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Detection ofOlea europaeasubsp.cuspidataandJuniperus procerain the dry Afromontane forest of northern Ethiopia using subpixel analysis of Landsat imagery

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Cited by 9 publications

References 16 publications

Allometric Models for Predicting Aboveground Biomass of Trees in the Dry Afromontane Forests of Northern Ethiopia

Allometric Models for Predicting Aboveground Biomass of Trees in the Dry Afromontane Forests of Northern Ethiopia

Environmental and anthropogenic factors affecting natural regeneration of degraded dry Afromontane forest

Carbon Stock and Soil Characteristics under Expansive Shrubs in the Dry Afromontane Forest in Northern Ethiopia

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