Land-use change and soil degradation: a case study, north of Iran.

Abstract

Deforestation in Iran has been more rapid in the past 50 years than at any time in Iran’s history. Intensive cultivation and mismamnagement have caused environmental problems and soil degradation. Soils which developed under natural forests in north Iran have been degraded by land-use changes. In this study it is hypothesized that deforestation and intensive agricultural activities with long-term inappropriate management caused significant soil degradation in the investigation area. The effects of long-term land-use changes and cultivation on soil degradation were quantified for two land-use systems including an undisturbed forest and a completely deforested area which were planted with tea after deforestation. Tea plantations with different duration after deforestation (10, 20, 30, and 40 years) were also investigated. Soil degradation was inferred by measuring the relative changes in soil properties. Results indicate that after deforestation and then long-term inappropriate cultivation activities in deforested areas, soil properies with respect to the different land use under different duration of plantation have significantly (P<0.01) changed. Cation exchange capacity, electrical conductivity, soil organic carbon, total nitrogen, and pH decreased in soil from forest to tea. Deforestation and subsequent tea plantation caused a significant increase of bulk density and a decline of the porosity of soil. The particle size distribution shows no significant differences (P<0.01) in clay, silt and sand fractions. Comparisons of soil properties under different duration of the tea plantation after deforestation indicated that time had a strong and significant effect on soil properties in the investigation area. Keyword: Soil degradation, Deforestation, Intensive cultivation, Soil properties, North of Iran