Investigation of changes in soil properties in pure and mixed beech type in the western forests of Guilan

Classification of forest sites is one of the most basic tasks for optimal forest management, which has practical and long-term concepts, such as regulating the structure of forests, increasing forest productivity, selecting fast-growing species suitable for afforestation, afforestation. The most productive methods are increasing the yield of wood to facilitate the relationship between supply and demand, revitalizing forests, increasing access to forest resources, and also fulfilling the ecological function of forests. In recent years, the use of different factors to classify habitats has become more and more widespread. This research aims to investigate the changes of the most important soil characteristics in beech habitats in Nav-e-Islam region.

This study was carried out in the series 3 Nav Asalem and in parcels 318, 320, 336 and 350. The desired parcels are located at two heights of 1100 and 1700. Parcel 320 was considered as a control parcel. In order to investigate and determine the types of trees in the surveyed parcels, 84 square samples with dimensions of 20 x 20 meters were taken randomly with a statistical grid of 200 x 150 meters. In each sample plot, in addition to recording the characteristics of slope, aspect and height above sea level, the variables of species type, height and diameter at the breast height of all tree species were taken. Then, the tree types of the target samples were determined using two-way analysis of indicator species (TWINSPAN). To determine the location of the soil profiles, a map of the shape of the land was prepared and considering the variety of habitat features and the area of the shape of the land, 35 sample plots were determined in homogeneous units, and the profiles were dug in these units and soil samples were taken. The soils were collected from horizons A and B. After digging each profile in the desired types, the vertical section of each profile was divided into different parts based on distinguishing features such as color, texture or soil structure. The preliminary analysis of soil profiles was done in nature and then soil samples were taken from each of the separated horizons A and B and transferred to the laboratory. Then, in a dry laboratory environment, after pounding, it was passed through a 2 mm sieve and the most important characteristics of the soil were investigated. To investigate the relationship between soil characteristics and tree types, conventional comparative analysis (CCA), one-way analysis of variance (ANOVA) and Duncan's test were used.

Based on the results of the TWINSPAN analysis, the area is divided into five types of trees, including pure Fagus (F), mixed Fagus –Acer velutinum (FA), mixed Carpinus-Fagus followed Alnus (CF), mixed Fagus-Carpinus (FR1) and mixed Fagus-Acer cappadocium (FR2) was classified. Based on the ranking results, clay percentage, carbon deposition and height above sea level in A horizon have a significant correlation with the positive direction of the first region, and organic carbon, accessible phosphorus and exchangeable potassium and carbon deposition have a correlation with the negative direction of the second region. It showed significant. In B horizon, the percentage of sand and height above sea level showed a significant correlation with the positive direction of the first axis and the percentage of clay, carbon, accessible phosphorus, exchangeable potassium and carbon deposition with the negative direction of the second factor. All five tree types were affected by altitude and clay percentage in A horizon. But (F), (FR2) and (FR1) were affected by clay percentage in B horizon and carbon deposition in both horizons and potassium in A horizon. (FR1), (FR2) and (FA) were influenced by the percentage of sand in both horizons and accessible phosphorus and exchangeable potassium in both horizons. The results of analysis of variance of physical and chemical properties of soil in tree types showed that there is a significant difference between bulk density, percentage of clay, percentage of sand, base saturation, acidity, organic carbon, accessible phosphorus, exchangeable potassium and so on. There is carbon sequestration among the tree types, no significant difference was observed between the characteristics of silt percentage and porosity percentage among the tree types. Also, the results showed that there is a significant difference between the percentage of organic carbon, exchangeable phosphorus and available potassium in two soil horizons, while there is a significant difference between the differences related to appearance, percentage of clay, percentage of silt, percentage of sand, percentage There is no saturation, porosity percentage, acidity and carbon deposition in two soil horizons.

The variety of topographical conditions in the forests of northern Iran and in the studied area is the cause of many changes in plant types and soil characteristics. According to the results of this research, in the types where the beech species is more dominant, the soil conditions are not very suitable, and the mixed types of beech are settled in the habitats with more slope and lower altitude, and the shallowness of the soil and Lack of nutrients is one of the main conditions of the soils of these habitats. The presence of different types in the forest is the result of the interaction of many factors, and it has been shown in this research that soil is one of the most important environmental conditions, and its significant relationship with tree types has been confirmed. Therefore, soil can be used as a suitable indicator to distinguish forest types.