Laboratory Tests on the Durability of American Woods—I

Abstract

Our present knowledge of the relative durability of American woods has been, for the most part, derived from service or field tests carried out by engineers or agriculturalists. Certain of the larger wood users, such as railroads, telephone and telegraph companies, have for several years past kept records on the durability of ties, poles and other timbers as a basis for the selection of durable material or for determining the expediency of applying wood preservatives. Similar data have been secured through the experimental work of the United States Forest Service and the Agricultural Experiment Stations. The conditions governing such tests can not be kept uniform or in any way put under control. Hence, even for a single species of timber, the data secured will be highly variable, depending upon the character of the soil, drainage, air and soil temperature, precipitation, atmospheric humidity, and any other factors which may influence the growth of wood-rotting fungi. Since environmental factors offer great variations between different regions of the United States, we can readily see why the natural durability of timber in warm, humid regions, for instance, frequently falls short of its resistance to decay in cooler, less moist localities. The question of the presence or absence of certain of the more destructive species of fungi in a given locality also influences natural durability. In regions long free of forests the soil may, for instance, be comparatively free of wood-rotting fungi. The relative great abundance of decay-producing species and individuals in the tropics is one factor in the rapid deterioration of timber in those regions. It is but Nature's way in maintaining the proper 80