The study of factors affecting on vegetation in sand beaches of the Boujagh National Pa-rk, Guilan Province

This paper concerns itself with the study of sand beaches of the Boujagh National Park with an area of 3477 ha. The purposes of this study include the determination of the plant species diversity and plant groups. In ad-dition, the determination of the impact of environmental and specific variables on the presence or absence of certain species and their communities is another aim that the study follows. In order to attain those purposes, 52 plots across 6 transects of the district were used. In each plot, the materials were identified and abundance-dominance of species by using Braun-Blanquet criteria were obtained and their life forms were determined according to Raunkiaer clas-sification. To determine the plant groups, a Two-way analysis of significant modified species (Modified TWINSP-AN) was utilized. Detrended Canonical Analysis (DCA) was used to determine factors affecting plant groups. The results showed that four plant groups exist in this district: Convolvulus persicus-Crepis foetida subsp. Foetida grou-p, Argusia sibirica group, Eryngium caucasicum-Juncus acutus group and Rubus sanctus group. The first and seco-nd groups consist of higher percentages of therophytes and spread in areas where the soil contains more sand. Plants in the third and fourth groups spread in areas with stabilized sand and high percentage of silt. DCA analysis results showed that soil factors (texture, OC, Na, K, N, Ca, Mg) have significant relation with plant groups were studied. Among the plant groups, the percentage of silt and sand, species richness and life forms of therophytes and geop-hytes show significant relations. Therefore it can be concluded that these factors affect on the separation and distri-bution of plant groups.