The two files in this directory are: source_code file in c++ (Gmodel.cpp), and parameter_set file (twelve_paramCoex.dat) of tree-size and patch-age structured model of forest dynamics (Kohyama 2006). The parameter_set file is for twelve-species case of Kohyama (2006); one can change species parameters there, and also number of species; for that change "spn" of c++ code. (c) all right reserved by Takashi Kohyama kohyama@ees.hokudai.ac.jp. Anyone who uses this simulator/code should refer to the paper: Kohyama T (2006) The effect of patch demography on the community structure of forest trees. Ecological Research 21, 346-355..