The Boreal Limits of Conifers

Abstract

There are 4 limits of a given sp. of tree as it approaches n. latitudes. The economic limit of forest is that beyond which commercial cutting endangers natural afforestation, the biological limit is the limit of continuous forest; the tree-line is the absolute polar, maritime or vertical limit of a sp. in tree-form and the limit of sp. is the line of most advanced outposts attained by a sp. irrespective of its type of growth. The polar limits are shown, plotted on circumpolar maps, for spp. in Picea, Abies, Pinus, Larix, Juni-perus, and Thuja. The polar limit of conifers is a phytogeographic boundary which is determined by the same general conditions that determine the boundaries of other spp. As the limit is approached a marked decrease in the edaphic amplitude of all spp. is noted. || ABSTRACT AUTHORS: W. W. Judd