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Figure 1.
Location of the study area in relation to the Horn of Africa. The blue circles refer to the regional forest areas where the occurrence points were taken. The green areas are used to indicate to forest stands (trees).
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Figure 2.
Erica arborea L. and its landscape around Embahasti – Alaje (a) and an Erica patch on the northern slopes of the Dabba Selama peak in Dogu'a Tembien (b).
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Figure 3.
Model performance ROC curve of the reconstructed Maxent model under current climatic simulation
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Figure 4.
Jackknife analysis of the importance of environmental variables in modelling the distribution of Erica
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Figure 5.
Predicted current potential distribution of Erica in Tigrai
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Figure 6.
Predicted future average potential distribution model of Erica (a) 2050 RCP4.5 (b) 2050 RCP8.5 (c) 2070 RCP4.5 (d) 2070 RCP8.5.
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Figure 7.
Suitability model of Erica predicted based on expert knowledge using five environmental variables and the current occurrence points. The green shaded area represents possible suitable areas for the growth of Erica. The red dots represent the actual presence data for Erica.
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Label Environmental variables Factor Unit bio1 Annual mean temperature 10 °C bio2 Mean diurnal range (mean of monthly (max temp – min temp)) 10 °C bio3 Isothermality (bio2/bio7)*(100) 100 − bio4 Temperature seasonality (standard deviation*100) 100 % bio5 Max temperature of warmest month 10 °C bio6 Min temperature of coldest month 10 °C bio7 Temperature annual range (bio5-bio6) 10 °C bio8 Mean temperature of wettest quarter 10 °C bio9 Mean temperature of driest quarter 10 °C bio10 Mean temperature of warmest quarter 10 °C bio11 Mean temperature of coldest quarter 10 °C bio12 Annual precipitation 1 mm bio13 Precipitation of wettest month 1 mm bio14 Precipitation of driest month 1 mm bio15 Precipitation of seasonality (coefficient of variation) 100 % bio16 Precipitation of wettest quarter 1 mm bio17 Precipitation of driest quarter 1 mm bio18 Precipitation of warmest quarter 1 mm bio19 Precipitation of coldest quarter 1 mm Altitude 1 m a. s. l Aspect 1 Degree Distance from sea 1 km Slope gradient 1 % • Those highlighted in bold refer to the selected environmental variable for the modelling; • Factor refers to the scale by which the environmental variable is multiplied for ease of storage in the raster. Table 1.
Environmental variables used for distribution modelling of Erica in Tigrai
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Variables Current Climatic scenario 2050 Climatic scenario2070 RCP4.5 RCP8.5 RCP4.5 RCP8.5 PC (%) PI (%) PC (%) PI (%) PC (%) PI (%) PC (%) PI (%) PC (%) PI (%) Altitude 29.6 45.2 27.3 56.9 32.2 49 33.8 56.1 29.1 43.7 Aspect 9.5 3.3 9.4 3.7 10.1 4.5 10.6 3.1 9 5.7 bio12 2.1 1.9 1.4 1.7 1.6 4 0.5 1 1.7 4 bio14 0.2 0.7 1.2 7.4 0 0.6 0.8 0.9 1.3 10.4 bio16 5.8 0.1 6.7 0.2 3.1 0.1 3.1 0 5.7 1.3 bio17 7.7 33.1 3.7 13.5 2.1 8.9 6.8 17.7 0.1 1 bio18 28.8 3.1 1.8 0.5 22.2 5.7 25.6 12.3 15.8 1.8 bio19 0.5 3 1.2 0.8 1.4 2 1.5 0.2 19.8 15.8 bio7 0.6 0.1 13.2 10.4 12.4 11.3 0.8 0.6 4.3 0.5 Distance 13.7 8.3 1 1.2 12.9 11.7 14.6 6.4 11.3 12.6 Slope 1.5 1.2 33.1 3.7 1.9 2.3 2.1 1.7 1.8 3 PC – Percent Contribution, PI – Permutation Importance, Distance – Distance from the sea Table 2.
Estimates of relative contributions and permutation importance of the predictor environmental variables to the SDMs.
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Suitability category Current Future scenario 2050 Future scenario 2070 RCP4.5 RCP8.5 RCP4.5 RCP8.5 Unsuitable 12855 13327 (+472) 13978 (+1123) 11909 (−946) 12473 (−382) Low suitable 1153 1321 (+158) 838 (−315) 1166 (+13) 420 (−733) Suitable 499 588 (+89) 490 (−9) 513 (+14) 171 (−328) Highly suitable 267 315 (+48) 274 (+7) 308 (+41) 142 (−125) Exceptionally suitable 178 186 (+8) 286 (108) 112 (−66) 265 (87) (+) refers to gain and (-) refers to loss in range areas (km2). Table 3.
Predicted changes (km2) in Erica ranges in the 2050s and 2070s under two climatic scenarios (RCP4.5 and RCP8.5) compared with the potential current distribution.
Figures
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Tables
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