Relationships Between Characteristics of Plant Communities and Climatic Conditions at Qara Soo Catchment Area, Gorgan

Abstract

In order to understand the relationships be tween climatic factors and the biological variables of plant communities in the Qara Soo Catchment Area, a systematic sampling of natural plant community variables such as crown closure, diversity, reproduction rate and crown height has been taken. Information about physical components of the ecosys- tems such as climatic elements, soil propert ies and topographic char acteristics was also collected for each plant community. By us ing the Numerical Taxonomy Model suggested by Sneath and Sokal (1963), the plant communities were classified and sorted according to a “development index” which indicates th e plant community development toward the climax stage of ecosystem. Then the relationships between ecosystem physical components and the biological variables of communities (d evelopment index) were understood by us- ing a multiple regression model. It was concluded that climatic elements are the dominant factor affecting on the formation, distribut ion, reproduction and stability of plant com- munities in the area. It was further conc luded that the Numerical Taxonomy Model, which has been commonly used by social scientists , is a suitable tool for system analysis in plant communities and natural ecosystems.