Saturday, 15 July 2006

Study of Physical and Chemical Soil Properties Variations in Relation to Forest Types and Some Topographic Factors in the North of Iran.

Ali Salehi, Natural Resources Faculty, Guilan Univ, Somesara, 1144, Iran and Ghavamoudin Zahedi Amiri, Natural Resources Faculty, Tehran Univ, Karadj, Iran.

The main aim of this research was studying of variations of physical and chemical soil properties in relation to forest types and some topographic factors in the north of Iran. The area of the study site is about 750 hectares and it is located in the north of Noshahr, Mazandaran province. To determine of forest types, square plots of 50 * 50 m (2500 m2) were established and on each plot, all trees more than 7.5 cm diameter at breast height were measured. The basal area for each tree species in each sample was calculated and using these variables, classification of the samples was carried out by TWINSPAN (Two Ways Indicator Species Analysis). On the base of this method four tree groups or forest types were determined. In order to select sites for soil sampling, forest types considered and on the other hand the forest was stratified into “landform units” based on differences in altitude, slope and aspect. In this way, 82 sample plots were selected for soil profiles from the original 325 tree plots. All of the soil profiles were described in the forest and pH, soil texture, bulk density, percentage of organic carbon, total of nitrogen, phosphorous and lime were analyzed in the soil laboratory. The soils were classified based on U.S.D.A. Soil Taxonomy (key of 1998). In order to determine the most important soil characteristics varied between soil profiles, Principle Component Analysis (PCA) was used. Among the soil properties, clay and silt content in A2 horizon, percentage of organic Carbon, total of nitrogen, C/N ratio and phosphorus in A1 horizon was the most important soil variables varied between the soil profiles. In order to study of relationships between soil properties and variations of trees composition and topographic conditions One-way ANOVA, Deternded Correspondence Analysis (DCA) and Canonical Correspondence Analysis were used. The results identified there are four main forest types (tree ecological group) in the study site. Among soil properties, percentage of organic carbon, C/N ratio and phosphorus in A1 horizon, soil texture, soil bulk density in A1 horizon was the most significant factors varied between forest types. Percentage of organic carbon and C/N ratio has the highest amount in Fagus-Carpinus and is the lowest in Carpinus-Ouercus forest type. The heavy soils can be finding in Quercus-Carpinus type, as the lightest soils belong to Fagus-Carpinus forest type. The amount of Phosphorus was the highest on Fagus-Tilia and there is a significant difference between forest types of Fagus-Carpinus and Fagus-Tilia on the base of it. On the other hand the results showed altitude was the most important topographic factor varied in relation to distribution of Fagus orientalis and Carpinus betulus, and also in relation to the variations of percentage of organic carbon as well as C/N ratio in the study site. Keywords: Nam-Khaneh district, Physical and chemical soil properties, tree ecological groups (forest types), PCA, DCA, CCA, ANOVA.

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