REGROW: a computer model simulating the early successional process of a disturbed northern hardwood ecosystem.
The relationships between the growth of individual plants and the availability of essential resources were explored using a spatially explicit simulation model - REGROW. The current version of REGROW was developed to simulate the dynamics of five dominant tree species (pin cherry, Prunus pensylvanica; the maples Acer saccharum and A. pensylvanicum; beech, Fagus grandifolia; and yellow birch, Betula alleghaniensis) in the early stage of regrowth following clear cutting of northern hardwood forest at Hubbard Brook Experimental Forest, New Hampshire. REGROW was calibrated and verified using information from a sub-set of permanent plots established following whole-tree harvest of a catchment at Hubbard Brook. Validation was performed using field survey data from another sub-set of these permanent plots. The model adequately tracked plant growth and changing community composition through 6 years of vegetation recovery on the study area. The results illustrated the importance to plants growing on severely disturbed soils of gaining access to adjacent, more fertile locations. Predictions of mortality under high-density conditions were inaccurate and reflected a general problem with the current version of REGROW in which most species parameters are either time invariant or vary in only a simple way. Differentiation in the size structure of populations and in the overall community increased markedly when simulations included both spatial variation in the site and mixed species populations. Other simulations illustrated the potential value of REGROW for analysing the factors influencing plant community dynamics on disturbed sites, but improvement in model performance will require more detailed information on the autecology and synecology of vegetation.