Forest types of Gzoo Taxus baccata L. researve and the analysis of vegetation in relation to environmental variables (Savadkooh, Mazandaran)

Taxus baccata is one of the few native needleleave species of north and northwest forests of Iran, distributed as a single tree or sometimes in spots. The Gazoo Yew reserve is one of the most valuable habitats of Taxus baccata in north of Iran, which has not been studied sufficiently. This study aimed to investigate the vegetation and the forest types as well as the effects of the environmental variables on the distribution of Taxus. The sampling was carried out using transects with regular intervals and randomized start point. 30 plots with a size of 20*20 m2 were taken. The TWINSPAN and cluster analysis methods were used to discriminate the vegetation types. The statistical comparisons were performed using ANOVA analysis and the relationships of species-environment were investigated using CCA (Canonical Correspondence Analysis). According to the results, three vegetation types including Taxus baccata-Carpinus betulus, Fagus orientalis-T. baccata and pure Fagus orientalis were identified in the region. Soil texture and pH were the most important factors in distinguishing vegetation types of the region. Soil texture and pH were the most important factor to separate vegetation types. The Taxus types had lower values of pH comparing pure Fagus one. Furthermore, the Taxus-Carpinus type was observed in the heavier soil (sand, clay loamy) comparing to pure Fagus (sandy loamy). The Fagus-Taxus type had soil texture conditions intermediary of two above mentioned forest types. Moreover, the soil organic carbon and total nitrogen were higher in pure Fagus type rather than Fagus-Taxus and Taxus-Carpinus types. None of investigated environmental factors showed a significant relationship to health and vigor of Taxus trees, however, increasing slope was accompanied by decreasing mean diameter of Taxus trees.