Wood structure and growth ring width of vital and non-vital Douglas fir (Pseudotsuga menziesiij from a single stand in the Netherlands

Abstract

A comparison was made of diameter growth and wood structure in 26 trees of Douglas fir of different vitality cJasses in a decJining, c. 50-years old stand in De Peel (southeastern Netherlands). Ring width patterns agree cJosely but not perfectly with vitality cJasses as estimated by external appearance of the crown. The 'diseased' vitality cJasses all show growth reductions over the last 20 to 30 years. In the most diseased cJass no wood had been formed at all at the stern base over the last 4 to 10 years. The onset of growth reduction may be connected with the effect of air pollution in the last 40 to 50 years. The most striking result was the inverse relationship between growth rate in the first 10 to 15 years of growth, and growth rate in the last decades: all trees which are healthy at present showed slow radial growth when young, and all diseased to dead trees exhibited fast growth in their youth. Sapwood area in trees of reduced vitality was less than in vigorous trees. Wood anatomical differcnces between vital and non-vital trees are only minor. Tracheid length showed a slight reduction in the last 5 years. Percentage vol-urne of cell wall material in earlywood and latewood are the same, but the percentage of earlywood is slightly higher in the latest formed narrow rings of the least vital (to dying) trees. The results are discussed with reference to data for other species and forest regions in Europe.