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Accueil du site → Doctorat → Autriche → Ecological impact evaluation of eucalyptus plantations in comparison with agricultural and grazing land-use types in the highlands of Ethiopia.

Universitaet fuer Bodenkultur Wien (2002)

Ecological impact evaluation of eucalyptus plantations in comparison with agricultural and grazing land-use types in the highlands of Ethiopia.

Hailu Zerfu

Titre : Ecological impact evaluation of eucalyptus plantations in comparison with agricultural and grazing land-use types in the highlands of Ethiopia.

Auteur : Hailu Zerfu

Akad. Grad : Thesis.Doctoral 2002

Université de soutenance : Universitaet fuer Bodenkultur Wien ; Institut fuer Waldoekologie

Descriptif
This study was conducted in the Central and Northwestern Highlands of Ethiopia where two Eucalyptus species namely E. globulus and E. camaldulensis are progressively integrated in the farming systems. The main intention of the study was to observe if there exists an adverse effect on soil properties in the upper most 50 cm due to land-use changes from agricultural uses to Eucalyptus plantations. In view of the hypothesis, that Eucalyptus plantations change the soil properties as compared to agricultural use, four soil types in two agro-ecological systems at different locations under three different land-uses were analysed. The data were scrutinized by two steps of statistical analysis. In the first step, a one way analysis of variance was calculated to observe whether or not significant differences between physical and chemical properties of the soils of the different land-use types could be detected. In the second step the mean values obtained were compared to each other using Scheffe’s multiple contrast test. In both cases the level of significance used was 0.05. Taking into account soil bulk density for physical properties comparison, this study revealed that there are no pronounced changes in the physical properties of soils due to land-use change from agricultural land-use to Eucalyptus plantations in all soils and sites evaluated. Looking at soil acidity, in Vertic Luvisols and Luvic Phaeozems, higher level of active acidity was found under E. globulus plantations in comparison to adjacent agricultural land. But there were no significant differences in exchangeable acidity in both soil types. In Humic Alisols and Rhodic Nitisols active acidity was found to be similar under E. camaldulensis plantations in comparison with other land-use types. However, in Humic Alisols and Rhodic Nitisols there are inconsistent indication of higher level of exchangeable acidity in some of the geometric sample horizons under E. camaldulensis plantations in comparison to adjacent agricultural land. Considering total macronutrients content of the soils, the results of this study show that land-use change from an agricultural use to Eucalyptus plantation doesn’t have an adverse impact on total soil nitrogen, phosphorus and sulphur content at least up to the age of 14.5 years. The case of potassium is variable. Soil potassium content in Vertic Luvisols under E. globulus plantations and in Humic Alisols under E. camaldulensis plantations was lower than the content in the agricultural lands. However, in Luvic Phaeozems and Rhodic Nitisols, it was found similar content of potassium under Eucalyptus plantation and adjacent agricultural lands. In the case of total soil calcium, it was found that both land-use practice and site quality have influential effect on total calcium content in Humic Alisols and Rhodic Nitisols where E. camaldulensis is the main plantation species. However, in Luvic Phaeozems and Vertic Luvisols, where E. globulus is the main plantation species, there is no adverse effect of land-use change from an agricultural use to Eucalyptus plantation on total soil calcium content. There is an adverse effect of land-use change from an agricultural use to Eucalyptus plantation on total soil magnesium content in Humic Alisols based on plantation management. Because densely planted site was found depleted than less densely planted site. In Luvic Phaeozems, Rhodic Nitisols and Vertic Luvisols there is no adverse effect of land-use change from agricultural use to Eucalyptus plantations on total soil magnesium content. Regarding exchangeable cations, exchangeable potassium content in Humic Alisols, Rhodic Nitisols and in Luvic Phaeozems was found to be similar between Eucalyptus plantations in comparisons with adjacent agricultural land. However, in Vertic Luvisols exchangeable potassium content was significantly higher in the agricultural land than adjacent Eucalyptus plantations. Therefore, there is no adverse effect of land-use change from an agricultural use to Eucalyptus plantations on exchangeable potassium content in Humic Alisols, Rhodic Nitisols, and Luvic Phaeozems at least up to the age of 14.5 years. However, in Vertic Luvisols there is an adverse effect of land-use change from an agricultural use to Eucalyptus plantation on exchangeable potassium content. An adverse effect was found on exchangeable calcium content due to land-use changes from an agricultural use to Eucalyptus plantation in Vertic Luvisols and Humic Alisols. However, the adverse effect of E. camaldulensis plantation in Humic Alisols seems because of density of trees planted and the continuous effect of litterfall raking from the plantation site. Because densely planted site was found depleted than less densely planted site. In Luvic Phaeozems and Rhodic Nitisols it was similar between soils under Eucalyptus plantations and adjacent agricultural land. Hence, both the land-use practice and site quality has influential effect on exchangeable calcium content. Exchangeable magnesium remained similar in Vertic Luvisols, Luvic Phaeozems and Rhodic Nitisols under Eucalyptus plantations and the adjacent agricultural land. However, in Humic Alisols, like that of exchangeable calcium, the contents of exchangeable magnesium significantly lower in densely planted site. Therefore, it is the management practice that influences the content of exchangeable magnesium. Studying the cation exchange capacity, in Vertic Luvisols, it was significantly higher in the agricultural land than the adjacent Eucalyptus plantations in the lower three (30-50 cm), sections. In Luvic Phaeozems cations exchange capacity was significantly higher in the agricultural land than the adjacent Eucalyptus plantations in the second (10-20 cm), and in the last (40-50 cm), sections. In Humic Alisols, cation exchange capacity remained similar in soils under Eucalyptus plantations and the adjacent agricultural land in all section evaluated except the first (0-10 cm) section. Similarly in Rhodic Nitisols (Ker Jarso site) it remained similar in soils under Eucalyptus plantations and the adjacent agricultural land in all soil section evaluated except the first (0-10 cm) section. However, in Rhodic Nitisols (Jufi-2 research site) cation exchange capacity remained similar between soils under Eucalyptus plantations and the adjacent agricultural land in all section evaluated in this study. In all sites similarity out weight differences, indeed complete similarity in some sites, in different geometric soil sample horizons. Therefore, statistically, there is no an absolute gradient that indicates an adverse effect on cations exchange capacity due to land-use changes from an agricultural use to Eucalyptus plantation. However, taking into account the absolute values, cation exchange capacity of soils under the agricultural lands were found better than under Eucalyptus plantations. This could be because of different reasons. The first one could be due to depleted site allocation for plantations at the very beginning or due to intensive litterfall raking through the life of the plantation that deplete the sites. An other possible reason could be better care for the soils under agricultural use than soils under Eucalyptus plantation.

Mots clé : Eucalyptus camaldulensis / Eucalyptus globulus / Austauschbare Kationen / Kationenaustauschkapazitaet / Bulkdichte — Eucalyptus camaldulensis / Eucalyptus globulus / Exchangeable cations / Cation exchange capacity / Bulk density

Présentation : Österreichische Dissertationsdatenbank

Page publiée le 27 mai 2008, mise à jour le 13 mars 2019