Intrinsic units in growth modeling

This study demonstrates the benefits of using units of age and size provided by trees (and other plants) themselves. When the age and size at the inflection point are employed to rescale the Richards equation, it becomes more simple and its parameters transparent. Because one of them is related to the ratio of two increments, both of which increase with site quality, it is possible to expect that this parameter is not affected by site quality. Existing modifications of the Richards equation that make it applicable to various site indices increase the number of parameters up to 10. The rescaled form of the equation applies to stands with any site quality, and requires no any additional parameters. The established link between the pattern of foliage distribution, which can be detected instantly, and the process of stand dynamics may facilitate growth predictions. The presented analysis identifies the growth stages (the age of inflection and the latest available age) that are most informative for growth modeling.