A study of tree species diversity and flora in different altitudes and slopes of the Shirinrood river valley, Mazandaran, Iran

Study of tree diversity in forests is ecologically a fundamental issue. Shirinrood river flows as a main upstream toward Tadjan river in mountainous hyrcanian forests, Iran. The river itself, the rich, almost continuous vegetation cover in its valley, between lateral embankments. This study was carried out on forest vegetation distributed in 700 to 1700 m along the east and west river banks of Shirinrood, extended south-north, central Elborz, to identify diversity of the trees in relation to physiographic factors and to distinguish understory floristic composition. Certain 40×40 m2 plots were established and vegetation parameters and physiographic factors were recorded inside. The data were subjected to analyses by biodiversity software’s. Dominant vegetation type was Fagus-Carpinus-Acer. The highest species diversity and lowest evenness were obtained in the mid-elevation part of the river (1300-1700 m). Statistically equal diversity was found in east and west slopes. Similar moisture and temperature as a result of narrow deep valleys makes two aspects of the river similar in climatic condition and so in biodiversity. Furthermore, we suggest that lower diversity in low elevations is the consequence of the comparatively higher anthropogenic disturbances. Evenness in west slopes and middle elevations was low because of high dominance by Fagus orientalis. The results also revealed 111 plant species belonging to different life forms and chorotypes. Hemicryptophytes (46%), phanerophytes (26%) and geophytes (21%) were dominant life forms and Euro-Siberian elements were dominant chorotypes in this area. Such studies may provide a critical venue for conservation of both species and natural ecosystems.