A Survey of Soil Carbon Stocks and Effective Soil Properties in Almond Orchards of Borujerd, West of Iran

Increasing soil carbon stocks (SCS) is one of the most important strategies for reducing carbon dioxide emissions and can substantially alleviate the adverse effects of climate change. In this regard, it is important to understand the relationship of soil CS with effective factors such as tree cover, soil texture, and land slope. The present study aimed to evaluate the effects of soil properties on SCS in almond orchards in Borujerd, Iran. Twenty almond orchards located in floodplains and/or piedmont plains were selected randomly and soil samples were taken at three depths (0-20, 20-40, and 40-60 cm) of both under tree canopies and bare soil. The soil physicochemical properties were determined in laboratory. The results showed that, on average, mean carbon sequestration rates were higher both under tree canopies and on bare ground in floodplains than piedmont plains and increased at greater depths in both regions. SCS had a negative relationship with soil bulk density and sand percentage but positive relationships with clay and silt percentages. However, increases in saturation moisture and nitrogen contents of the soils had a positive effect on SCS. In general, the higher SCS under trees than bare soil, and in fine-textured than coarse-textured soils, indicate the importance of establishing almond plantations, especially in sloping lands, to mitigate soil erosion and enhance carbon sequestration.