Wood anatomical variation in relation to latitude anf altitude

The wood anatomical variation within 17 eurytherm hardwood genera in relation to altitude and latitude has been studied using wood samples from 52 species. With increasing latitude a miniaturization of secondary xylem elements (shorter vessel members, narrower vessels, shorter and sometimes narrower fibres, lower rays) is reported, together with an increase in vessel frequency and frequency and expression of helical thickenings to the vessel walls. Increasing altitude has similar but much weaker effects, and none on vessel grouping or helical thickenings. The number of bars per perforation plate in genera with partly or exclusively scalariform perforations is in general not correlated with altitude or latitude. In the softwood genus Podocarpus tracheid length and diameter and ray height decrease with increasing altitude. An analysis of the wood anatomical variation within 2 species with a wide latitudinal and 5 with a wide altitudinal range did not reveal correlations between the above mentioned features and latitude or altitude. The results are discussed with reference to previous interpretations of latitudinal and altitudinal variation in wood (Baas, 1973), stressing the significance for phylogenetic wood anatomy.