Abundance and occurrence of Danae racemosa growing in Hyrcanian forest understory about static and dynamic environmental variables

Danae racemosa L., an endangered species, is an erect, evergreen shrub that grows in the shaded forest understory in the Hyrcanian forests of Iran. Except for limited knowledge of the sporadic occurrence of D. racemosa in unique moist locations, there is not much information about its ecological preferences and environmental requirements. This study investigated the relationship of D. racemosa presence (abundance) and occurrence with static (soil properties and elevation from sea level) and dynamic (climate, precipitation, and human disturbance) variables. Plant and soil samples from 21 locations of occurrence (sites) of D. racemosa were collected along the Caspian Sea’s southern coastline. At each site of occurrence (site), three 100 m2 (10×10 m) plot was set up, and plant biometry and density were recorded. Soil samples were taken from depths of 0-25 cm and left to air dry in the lab. Later, dried soil samples were crust left to pass through a 2 mm mesh sieve and analyzed for different physicochemical properties. Meteorological data over the past 10 years (2009-2019) in the relevant area were obtained from Iran Meteorological Organization. Cluster analysis classified 21 sampling sites into four groups of habitats. Data were analyzed using Principal Component Analysis (PCA) methods and habitats are classified based on environmental factors. Correlation analysis between environmental factors and density showed that soil texture (clay content), precipitation, and human activity are the most important factors affecting the abundance of D.racemosa. The findings of this investigation are useful in developing D. racemosa habitat protection, restoration, and management guidelines as well as necessitate urgency of awareness-raising.