- Allen, Howard Lee, Jr.
The Graduate School, University of Maine
Sixty-four sample plots established in even-aged spruce-fir stands in northern Maine were used to determine the effect of soil, topographic, and stand factors upon site productivity. Site productivity was expressed as ten growth parameters including four measures of site index, two measures of bole-wood volume growth per unit area, height growth of the overstory trees, and basal area growth of the overstory trees per unit area. The soil and topographic factors included measures of the pH of the O1, O2, A, B, and C horizons, bulk densities of the O2, A, B, and C horizons, texture and coarse fraction percentages of the mineral soil horizons, thicknesses of all major horizons, depth to the pan, depth to mottling, rooting depth, drainage classification, slope, aspect, and interactions and transformations of the above variables. Stand factors included measures of density and age. Each of the ten productivity measures was first regressed on the 49 soil and topographic factors, and then on the 49 soil and topographic factors plus 13 stand factors.
The site productivity-soil equations developed are of little practical use in predicting site productivity in view of the low coefficients of determination and the inclusion of dynamic organic pad variables.
The effect of organic pad properties on site productivity emphasizes the need for further study of both the chemical and physical properties of the organic pad and their relationship to the growth of spruce and fir.