Modeling distribution of forest types of Armardeh forests at Baneh, using logistic regression method

This research was carried out to predict potential distribution of Armardeh forests types (16482.44 hectares). Determination and classification of forest types was made, based on data of 448 circular sample plots (0.1 hectare area). Eight forest types were identified, in which four types, including “Quercus infectoria- Quercus brantii”, “Quercus brantii-other species, mixed with Quercus infectoria”, “Quercus brantii, Quercus libani mixed with other species” and“Quercus brantii” were modeled using physiographical factors. Modeling was performed by both logistic regression and stepwise methods (likelihood ratio), using 70% of the samples for modeling and 30% of them for model validation. Results showed that the achieved models for the forest types with limited distribution range, had more accuracy than the other types. According to ROC curve test, the greatest precision was allocated to models related to “Q .brantii”, “Q. brantii, Q. libanii mixed with other species”, “Q. brantii -other species, mixed with Q. infectorai” and “Q. infectoria- Q. brantii” forest types, respectively. Furthermore, due to presence of aspect in most of the models, it was distinguished as an important physiographical parameter in local forest type's distribution. Overall, according to positive and negative correlation between presence of each forest type with variables which take part in the logistic model process, its accordance with results obtained from forest type map adaptation with other studied parameters, and further similar research results, it might be concluded that logistic regression is an appropriate method to study effects of different factors on spatial distribution of various forest types. Forest types predicted probability maps, could be used as a management tools for development and rehabilitation of forest ecosystems

Effect of conversion of rangelands to planted forests on some physical and chemical soil properties

So far it is well known that the conversion of degraded rangelands to planted forests through afforestation practices affects soil properties. Therefore, we selected one rangeland and two planted forest area to study the physical and chemical properties of soil in different land uses in Hassanabad region of Sanandaj in Kurdistan province. Physical soil characteristics such as the percentage of water content and soil bulk density were sampled in two-week intervals during 2012 to 2013 at three points in each area. In addition, a set of double rings was conducted to measure infiltration rate at three points within each area. The saturated hydraulic conductivity was computed using the experimental infiltration data. The soil samples for measuring chemical properties (e.g. pH, EC, organic carbon content, phosphorus and total nitrogen) were taken from 3 points in each area at the depth of 20 cm with six repeated measurements. The results showed that converting degraded rangelands to tree plantations has resulted in enhancing the quality of soil physical characteristics, whereas only a portion of the chemical characteristics (organic carbon content, phosphorus and total nitrogen) were positively affected

A quantitative study of pollarding process in silvopastoral systems of Northern Zagros, Iran

Aim of study: This research attempts to quantitatively describe the pollarding process in the northern Zagros, western Iran.Material and methods: An inventory of all trees was conducted in three representative stands in the pollarded section (DBH ≥ 5 cm): DBH, total height, trunk height and crown diameters were measured. At the time of pollarding, 10% of the foliage stacks were randomly selected and weighed. The positions of each store tree (i.e. special trees capable of enduring the weight of a certain number of leafy branches (average 600 kg)) and horizontal distance of pollarded trees associated with each store tree was recorded.Main results: The number and weight of foliage stacks resulting from pollarding of each tree correlated (0.48 and 0.43, respectively) with their crown diameter. The average dry weight of leaf biomass was 1,525.6 ±108.1 kg/ha and there was a significant difference between the selected stands. The average pollarded area and the average number of trees in the pollarded area of each store tree was 501.1±210.4 m2 and 9.4±3.5 trees, respectively.Research highlights: The number of pollarded trees associated with each store tree and the weight of stored foliage stacks on them are determined by the distance between pollarded trees and store trees, the number of trees around the store trees and the ability of selected store trees to bear the weight of foliage stacks

Response of Gall oak (Quercus infectoria Oliv.) to pollarding in northern Zagros

This study aimed to investigate the response of Gall oak (Quercus infectoria Oliv.) to pollarding. Therefore, a less-disturbed stand (1.4 ha) and a pollarded stand (1.7 ha) were selected. Five rectangular plots (20×30 m) were established in each selected stand by random sampling. In each plot, tree species, diameter at breast height (DBH), total height, trunk height and crown diameter for all trees (DBH ≥ 5 cm) were recorded. In addition, 18 tree samples were taken in each studied stands to assess the diameter increment of Gall oak. A pair of increment cores per sample tree was taken 50 cm above ground level, in which annual radial increment was measured and further multiplied by 2 to derive the annual diameter increment. Then, the diameter increment distribution of Gall oak trees in identical diameter classes was determined for the period of 1984-2010. The mean radial increment of two cores extracted from each sample tree was used in the calculations. The results showed that the average diameters, total height, trunk height, crown height and crown area were significantly lower (p < 0.01) in pollarded stands. Moreover, the averagee diameter increment in less disturbed and pollarded stands was estimated 1.32 and 2.08 mm per year, respectively. The results indicated that average diameter increment of Gall oak trees across he identical diameter classes during the studied period was significantly different between the examined stands