Root Distribution and Environment in a Maple-Oak Forest

The relationship of the Bellefontaine silt loam soil profile, with its inclusions, to the root development of the native species in the maple-oak forest at Wychwood, Lake Geneva, Wisconsin, was studied during the summers of 1938-1940. Stations were selected to obtain a cross-section of the varying conditions in the forest. 2. Sixteen station types were investigated by the trench method of root-distribution sampling. In six of the station types a new, square method of trenching afforded more accurate measurement of the heterogeneous root distribution than did the rectangular trenches most commonly employed. 3. Root systems of herbaceous and woody seedlings in the various station types were excavated and their relation to the upper horizons noted. Large specimens of sugar maple, red oak, and white oak also were partially excavated. Root volumes were obtained from surface cubic-foot samples in each station type. Cicada and earthworm activity was observed. 4. Greatest concentration of the smallest roots, 0.1-1.0 mm. in diameter, was in the A1 horizon. Larger roots did not show an increase in numbers per unit horizon surface below the A horizons. Greater numbers of dead roots occurred in lower horizons. 5. On root number and percentage root-area basis, horizons A1, A2, B1, B2, and C1 generally showed successive decrease in suitability for root development. On the same basis there were marked decreases, with two exceptions, of root numbers and area with successive 1-foot increases in depth to 3 feet. 6. Areas with sparse ground cover showed low root numbers and comparatively high percentage root areas. Stations with more abundant ground cover were characterized by larger root numbers and smaller percentage root areas. 7. Earthworm and cicada activities, particularly the former, were important factors in the soil environment. Such activities were more or less uniform throughout the woodland. 8. In all cubic-foot root-volume samples, the 0-8 inch level contained 80 per cent or more of the total root volume present in the sample. When the sample lacked roots > 1/2 inch in diameter there were successive decreases in volume in passing into the 0-4, 4-8, and 8-12 inch levels.