Modeling topographic factors affecting bracket fungi dispersal in district І of the Shastkolateh forest of Gorgan

Bracket fungi are among the important macroscopic wood decaying fungi in the forests. The aim of this study was to examine occurrence of bracket fungus with topographic factors and spatial distribution modeling of bracket fungus in district one of Shastkolateh Educational and Research forest of Gorgan province. Inventory of trees infected by bracket fungus was conducted using two strip transects and GPS data were recorded for the affected trees. Topographic map of primary and secondary factors associated with the presence of fungi including altitude, slope, aspect, solar radiation energy, amount of shade, wetness and landform by terrain analysis were developed on a digital elevation model. To evaluate frequency of bracket fungi, the Chi-square test and modeling spatial distribution of bracket fungus occurrence using logistic regression was performed. Predict map of the of bracket fungus presence were prepared and divided into different zones. Results showed that the highest fungi presences was mainly on the altitudes of above 700 m with 63.5% frequency, on the slopes of with 0-30 percent with frequency of 73.5 percent and western aspect with 36.4% frequency. The coefficients of the variables in the logistic regression model indicated that the variables of altitude, slope direction, solar radiation, humidity, topography and shape of the shelf fungi have a positive while, the slope and shadow variables have a negative effect. Generally, altitude and humidity are most important agents affecting occurrence of a shelf fungus.