Abrupt growth changes in conifers

Abstract

Abrupt changes in growth (reduction or recovery) persisting for a number of years and evident in annual ring sequences from conifers are visually identified, dated, and related to crown condition, site, region, and ecological factors. Analysis of several thousand trees shows that radial growth is only very loosely related to the density of needles in the crown. In those regions of Switzerland studied, the different species react differently to environmental conditions, each having its own indicator value. The frequency of growth reductions is governed by climatic conditions and other, unidentifiable factors. Only in a few areas is pollution the probable cause.