Effect of Forest and Non-Forest Land Covers on Soil Organic Matter, Fulvic and Humic Acids

Nowadays the effective role of organic matter has been proven in improving soil productivity. Regarding to sensitivity of sustainable organic matter component to different land use practices in addition to the organic matter, investigation of changes in its compound is important. Determining the evaluation of organic matter and amount of carbon stabilization in soil system, and their quality and quantity will be varied according to the type of land use.

Due to extensive land use in the north of Iran, present study focused on effect of these uses on the content of organic matter and its humic components. In this regard a study was carried out in five land use including: beech forest, Fraxinus plantation, black pine plantation, degraded forest and agriculture in Tajan watershed. Eight points were selected in each site and soil samples were taken at a 25 × 25 area to a depth of 15 cm.

Highest of organic matter (4.68 %), fulvic acid (668.750 mg/100 gr soil) and humic acid (976.620 mg/100 gr soil) were observed in agriculture land cover. Some soil physical, chemical and biological features were also measured. Whole of studied soil characters were significantly different among land covers, except silt content.

Though as for the results, highest contribution of organic compounds were observed in agriculture land, according to the PCA analysis, soil nutrition condition and microbial activity were more appropriate in forest stands. More quality of debris along the favorable environmental condition and presence of microbial activity can be attributed to a reduction in rate of accumulation of remains following the process of organic matter decomposition and mineralization in forest stands. The findings of this study suggest that protecting of natural forest is very important. In addition, in degraded areas of northern Iran, planting of Fraxinus excelsior species can be considered due to improvement of soil quality and health.