ADULT RECRUITMENT AS A FUNCTION OF JUVENILE GROWTH-RATE IN SIZE-STRUCTURED PLANT-POPULATIONS

The recruitment of adults in size-structured plant populations will be sensitive to changes in juvenile growth rates when: 1) mortality is high, 2) growth rates are low, 3) the difference between seedling and adult size is large and 4) self-thinning among juvenile plants is negligible. This sensitivity can be quantified by a single parameter in a simple, general expression relating recruitment to growth. The model is demonstrated for the prediction of young spruce tree densities on small plots, and the calculation of the parameter is shown for two published demographic studies. The model can also predict features of population response to an environmental gradient, such as long tails or abrupt cut-offs, even when these features are not found in the physiological response to the gradient.