Factors Influencing Soil Formation and Evolution in Banaft Region "Kasilian Mazandaran Watershed"

Extended abstract 1- Introduction Climate, terrain condition, vegetation coverage, parent materials, and time are among the factors that affect the soil formation and contribute to such soil properties as porosity, apparent and actual specific gravities, and clay and carbonate contents. The forest soils have been consistently regarded for their high content of organic matter and suitable structure. In the meantime, changes in the management scheme, land use, and soil treatment procedures can significantly alter the organic matter content and other physical and chemical properties of the soil (Hagedorn et al., 2001; Stoate et al., 2001; Dawson and Smith, 2007). The organic matter greatly contributes to improved crop yield by directly affecting the physical and chemical properties of the soil. Considering the importance of the soil and its properties for many managerial programs, the present research aims at investigating the reasons behind the formation of various soil types within the Kasilian Area, Mazandaran Province, Iran. Similar areas can be observed in other places across the so-called Hyrcanian Forests by Quick review of the satellite images. Accordingly, the findings of the present research are important for similar forest areas and forest settlements. 2- Methodology The watershed area range was delineated based on satellite images and topographic maps. The area was then surveyed by selecting and studying a number of soil sections where the soil variations were relatively large across an acceptably large extent. The extents of different formations were identified and the land components were determined by using geological maps. By considering the available geological and geomorphological data and interpretation of the satellite images combined with terrestrial observations and profile descriptions of the profiles and the land component sections, different land components were distinguished. The land components were considered as relatively homogeneous work units, and the pedological studies were focused on these units. The units were relatively identical in terms of the soil, physiography, climate, and the parent materials, with an attempt made to take into consideration about the relation between the transacts and the soil evolution. Seven soil profiles were selected by the studied profiles and sections, as to control for which the experimental results and classification outcomes were presented. 3- Results The climatic condition was almost the same across the entire study area, so that its impact on the soil was similar in different parts of the area. The more important factor that mitigated the impact on the climatic condition and contributed to the formation of various soil types across the region was the versatility of the geological formations and the terrain over the study area. So the present-day variations in the soil classification can be greatly linked to the changes in the Mollic horizon thickness. In this research, the maximum organic carbon content was observed in the samples taken from the forest lands, with its value significantly dropped in the deforested areas, especially the farmed lands. Variations of the organic carbon content of the soil is an important indicator of the soil quality for investigating the effects of managerial operations in the farmed and forest lands. The soils formed on top of the Lar (L1J), Delichay (jd), and Shemshak Formations (TR3.JS) were found to be residual soils. Although the Lar and Delichay formations are dominantly composed of lime, their evolution has been interrupted in the region due to the very high slopes to which the formation has been exposed, making the corresponding soils classified as Inceptisol. This is while the Shemshak Formation has been exposed to a relatively slower slope, so that the forest vegetation coverage and more limited horizontal displacement of the soil have provided enough time to form the Mollic horizon and the Mollisols. In the sediments located within the valleys between the quaternary hills and mounts, which were previously covered by forests and now are turned into low-slope pastures, the Mollic horizon has been appropriately preserved, with the lime content of the parent materials transported to underlying horizons to form a calcite horizon. This part of the land is covered by Mollisols that were generally classified as calciudolls considering the moisture regime of the soil. In the sloping lands, as a result of the erosion of the surface soil, the Mollic horizon was degraded, which made the soil classified under Entisols and the great class of Udorthents. On such lands, upon erosion of the overlying soil, the underlying rocks along the soil profile are exposed. 4- Discussion & Conclusions A Comparison of soils in Bare lands with forest lands showed a dramatic declining trend in the soil properties. In this respect, the farmlands were dominantly covered by Entisols while the pastures were most often covered by Inceptisols and the forests were dominated by Mollisols; these showed the soil variations under similar natural conditions as a result of changes in the land use. It is recommended to set the scene not only to limit the deforestation process, but also to suit the pastures for natural forestation in an attempt to prevent further erosion of the invaluable soil and preserve the even more valuable natural resources.