Effect of Eucalyptus globulus Plantations on Soil Physicochemical Properties in the Upper Blue Nile, Ethiopia

Abstract

In recent years, there has been a substantial conversion of croplands and grasslands to short rotation Eucalyptus globulus plantations in the northern highlands of Ethiopia. This has raised concerns among researchers, policymakers, and environmentalists regarding potential adverse effects on soil fertility. To address these concerns, a study was conducted to evaluate the impact of Eucalyptus globulus plantations on selected soil physicochemical properties in the region. The study involved four land-use types, comprising two age groups of Eucalyptus globulus plantations (4-year-old and 9-year-old), as well as areas designated for grasslands and croplands. Soil sampling was carried out in 10 m × 10 m subplots within each experimental plot, and standard methods were employed for soil analysis. The soil laboratory results were statistically analyzed using Two-way ANOVA and Pearson’s correlation coefficients in R software version 4.1.0. The findings revealed significant variations ($p<0.05$) in soil bulk density, soil organic carbon, and soil $\text{pH\hspace{0.17em}between\hspace{0.17em}the\hspace{0.17em}}4$-year-old and 9-year-old Eucalyptus globulus plantations and the grasslands. A notable difference ($p<0.05$) in exchangeable acidity was observed between the 4-year-old and 9-year-old E. globulus plantations, with the latter exhibiting the highest mean exchangeable acidity (6.20 ± 0.76). However, no significant differences ($p<0.05$) were observed between the Eucalyptus plantations and the grasslands in available phosphorus (Av.P), exchangeable calcium (Ca2+), sodium (Na+), and magnesium (Mg2+) concentrations, as well as cation exchange capacity (CEC). The study results has, therefore, implied that Eucalyptus globulus plantations induced changes in specific soil properties with varying stand ages in the study area. Nonetheless, it was emphasized that further long-term research is necessary to comprehend the effects of these plantations on soil properties.