Soil organic carbon physical fractions and aggregate stability influenced by land use in humid region of northern Iran

Abstract

The present study was executed in order to examine the influences of land use change on aggregate stability and soil organic carbon fractions in the humid region of the north of Iran. The study area featured three land uses which included natural Hyrcanian forest, tea plantation and paddy rice cultivation. One hundred soil samples were taken from the 0-10 cm layer in a grid pattern to allow for variations in the study area as much as possible in summer 2016. The results revealed that land use change significantly altered the physical and chemical characteristics of the soil, as the highest values of soil organic carbon and complexed organic carbon, and the lowest values of pH, calcium carbonate equivalent and bulk density, were observed in the natural forest. The greatest percentage of macro-aggregates was found in the natural forest followed by the tea plantation. Particulate organic carbon and soil organic carbon associated with clay and silt particles as well as soil organic carbon associated with all aggregate fractions showed the following trend: natural forest > tea plantation > rice cultivation. Overall, our results confirmed the importance of forest soils in C sequestration and the vital role played by soil organic carbon in soils to improve soil quality indicators and aggregation. K e y w o r d s: Hyrcanian forest, tea plantation, paddy rice, complexed organic carbon

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