Role of Deforestation on Spatial Variability of Soil Nutrients in a Hyrcanian Forest

Studying forest degradation through evaluation of soil nutrient concentrations, which reveals soil functioning within the ecosystem, is necessary for sustainable management of land resources. This research was conducted to understand the changes of soil nutrient, resulting from exploitive management using some soil features and their spatial pattern. In the mid-summer of 2014, two sites were selected consisting of an undisturbed forest site (FS) and a completely deforested site (DS); both sites were in lowland part of Khanikan forests located in Mazandaran Province, north of Iran. Within each site 50 soil samples were obtained from 0-30cm depth along two sampling lines with 500 meter length thus resulting in 100 soil samples for each site. The interval between samples along lines and also the distance between lines were selected 10 m. The mean pH was lower at the DS (5.70) than FS (6.58). The mean of soil organic carbon (SOC) was significantly higher at FS (2.78 %) when compared with DS (0.56 %). Total nitrogen (N) also followed the same trend having significantly higher values at FS (0.28%) than DS (0.16%). Mean available phosphorus (P) values were significantly higher at the FS (17.33 mg kg-1) than at the DS (7.24 mg kg-1). The amounts of available potassium (K) were significantly higher at the FS (148.15 mg kg-1) than DS (84.14 mg kg-1). A geostatistical analysis revealed that deforestation changed the spatial variability models and fractal dimension of soil features. As a conclusion, the spatial variability of soil pH and SOC were more imposed by deforestation compared to the other soil features. Our results suggest that deforestation should be regarded as an effective factor on variability of soil nutrient that are tied to forest ecosystem management.