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The study of spatial distribution of forest changes tin the northern forests of Iran
 M. P. Bavaghar A. A. Darvishsefat, M. Namiranian RS & GIS laboratory, Faculty of Natural Resources, University of Tehran, Karaj, Iran Tel: +98 261 2223044, Fax: +98 261 2227765 Email: mahtab_bavaghar@yahoo.com, adarvish@chamran.ut.ac.ir, namirani@nrf.ut.ac.ir Introduction The broad leaved forests of the north of Iran related to the third geological period having particular genetic diversity are the most important renewable natural resources in Iran. These forests with a rich biodiversity are said hyrcanian forests. More than 80 tree species and 50 shrub species exist in these forests with an area of 1.9 million hectares. Therefore, these forests have unique economical and environmental characteristics, so it is necessary to protect them, seriously. Decreasing of forests area in the north of Iran is one of the important problems in recent years. According to the information represented by Forest and Ranges Organization (FRO) of Iran and also by comparing the maps of forests of the years 1967 and 1994, the forest area in the north of Iran was decreased about 141572 hectares (7.1% of the total area) in this period. Comprehensive protection planning in these forests needs to be aware of the main factors causing deforestation and decreasing forests area. Since there are valuable data (digital topographic-thematic maps for the years 1967 and 1994) about these forests, it is necessary to analyze them quantitatively. This will provide important information about forest changes and spatial distribution of these changes related to different environmental factors. The possibility of analyzing environmental data using a GIS approach is a very useful assistance in forest management. Puzzola and Folving studied the forests spatial distribution in Mt Etna in relationship with some environmental characteristics, such as topographic, geological and climatic parameters. In this study GIS techniques were used for the analysis. Cropper et al. (1999) investigated the factors, which affect the location of deforestation in northern Thailand. The authors presented a model to predict where deforestation is likely to occur and examined the effects of two government policies – road building and establishment of protected areas – on this likelihood. The aim of our study in Iran was to provide a description of spatial distribution of forest changes related to environmental parameters including slope, aspect, elevation above sea level and distance from roads and residential areas in 4 watershed basins. Methodology 1. Study area The study area is situated in eastern Gilan province in southwestern of Caspian sea (Fig. 1). The research was performed in 4 watershed basins while 113 watershed basins cover the hyrcanian forests totally. These 4 watershed basins cover approximately 1033 km2. Elevation ranges from 0 to 2900 meters above sea level and slope varies from 0 to 320%. This region has a temperate climate and rainfall is distributed throughout the year. The study area is flat at the north and rugged mountains cover southern parts. The most important forest species are Fagus orientalis, Carpinus betulus, Quercus castaneifolia, Zelkova carpinifolia, Acer velutinum, Gleditschia caspica, Alnus subcordata, Alnus glutinosa, Diospyros lotus, Parrotia persica, Ulmus glabra, Taxus baccata, Populus caspica.
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