Principles of Growth Partitioning Between Trees in Forest Stands Under Stress

Abstract

The focus is on the interindividual growth partitioning in forest stands under stress. We use (1) individual tree records of size and growth from about 100 long-term experimental plots under survey since 1871 in forest stands along an ecological gradient through South Germany, (2) annual measurements of the size–growth relationship, including the extremely dry years of 1976 and 2003, from a mixing experiment of spruce and beech, and (3) annual growth rates of spruces and beeches with and without double ambient ozone fumigation between 2000 and 2007. Low stress increases steepness and size-asymmetry of the size–growth relationship, i.e., it favors the superiority of tall trees at the smaller trees’ expense. High stress, no matter whether induced by competition, drought, or ozone, distinctly reduces the superior growth rate of tall trees. The causes for this behavior and the consequences for modeling stand dynamics and silvicultural treatment are discussed.