Long term effects of deforestation on soil attributes: case study, Northern Iran

Abstract

The objective of this study was to investigate the effects of land use change on soil properties in six different sites of Guilan province, northern Iran. The study sites were deforested approximately 40 years ago and changed to tea farms. Soil samples from 0 to 30 cm depth were collected in June 2016 and analyzed for total Nitrogen -N-, soil organic C -OC-, available phosphorus, pH, electrical conductivity -EC-, exchangeable Ca, Mg, Na, K, and Al, Mean weight diameter -MWD- of aggregates, water stable aggregates -WSA- and bulk density. Soil properties of two soil land uses were compared. The results showed that after land use change from natural forest to tea farms, soil physical and chemical characteristics changed. Land use change resulted in significant decreases in organic carbon, available potassium and pH. Reduction of annual organic matter input to soil as a result of deforestation and also rapid oxidation of organic matter in deforested places were responsible for a significant decrease in OC. Soil microbial respiration -SMR- also decreased significantly, following deforestation and decreasing the organic carbon. Changes in soil exchangeable Ca, Mg and available P in two land uses were not significant. The results indicated that tea farming for 40 years was not affects soil structural indicators -BD, MWD and WSA-. Also decreasing the soil pH increased soil Al, so that the exchangeable Al in forest soils was 1.16 ppm, while in tea farm soils it was 1.9 ppm, which Al toxicity is an important issue in this region.