Edaphic Controls of Tree Species in Presettlement Indiana
1965
Crankshaw, William B. | Qadir, Syed A. | Lindsey, Alton A.
A quantitative analysis of the soil relations of the tree species of Indiana was made using the General Land Office original survey records and the Indiana soil survey reports. The bearing trees recorded on the GLO records were located on modern county soil maps to identify the soil upon which each bearing tree was situated. Eleven soil characteristics of probable influence on trees were studied: thickness of the A and B horizons and solum, amount of nitrogen, pH, textural proportions, depth of leaching, available water capacity, and water intake rate. These factors were determined for the sites of 70,240 bearing trees. The random pairs and closest individual methods were applied to determine species and stand attributes. A separate multiple regression was run by computer for three dependent variables (importance value, basal area per acre, and mean basal area) for each of 45 tree species using the 11 soil characteristics as independent variables. The results of the regressions were interpreted by using a Deletion—probability Index, the average of the step at which a variable was deleted in the regression and the probability level at deletion. The indices were plotted on circular graphs which showed the relative influence of each soil factor on each species. For tree species in general, the most influential soil attributes proved to be depth of the soil horizons, percentage of nitrogen, and percentage of clay, in that order.
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