Date of this Version
A new method has been devised by which a complete sample of an entire root system may be taken from soil surface to maximum depth of penetration. The roots are separated from the soil without injury to them or displacement of individual roots from their natural position. They are examined in the laboratory in relation to the various horizons of the soil profile. Monoliths 12 inches wide, 3 inches thick, and 3-5 feet in depth are taken from the walls of trenches made in selected pure stands of each species. Roots are obtained from the monolith by a system of soaking and gentle washing. A special technique is used in mounting. Lighting for photographing is by electro-flash units. The root system is sectioned so as to obtain the oven-dry weight for each 6 inches or foot in depth as well as for each major soil horizon. A brief description of the method may be found in Science (7) and a comp]ete one in Ecological Monographs (8).
This new method, which permits the studying of the intimate relations of roots and soils and of measuring root production quantitatively at various soil levels, has been used extensively. Descriptions have been made of the profiles of twenty soil types, from which thirteen species (and about fifty monoliths) have been taken. The chief purpose of these studies was to examine soil-root relationships in various soil types (8). The present paper is concerned with results obtained by a modification of the method and its use in studying succession and degeneration of vegetation.