FINE-TEXTURED SOIL BANDS AND OAK FOREST PRODUCTIVITY IN NORTHWESTERN LOWER MICHIGAN, USA

The relationship between fine-textured soil bands and forest productiv ity was studied by comparing three mixed-oak (Quercus rubra L. and Que rcus alba L.) stands that had little or no fine-textured banding with three stands that had bands. The degree to which soil factors could ac count for differences in productivity between banded and unbanded stan ds was examined using two methods, one based on field observations (ba nding codes) and the other based on laboratory textural analysis. Beca use stand ages were not significantly different, overstory biomass was used as an index of productivity. Mean overstory biomass in the bande d stands was 312 Mg/ha, significantly greater than 170 Mg/ha measured in the unbanded stands. Mean percent clay + silt and mean banding code also were significantly higher in banded than in unbanded stands. Lin ear regression analysis indicated that mean percent clay + silt accoun ted for 57% of the variation in overstory biomass, whereas mean bandin g code accounted for 40% of the variation. In the oak stands we studie d, variation in productivity can be explained largely by differences i n soil texture associated with fine-textured bands. We also found a po sitive relationship between mean banding code and mean percent clay silt (r2 = 0.90), which suggests that the field method of quantifying banding can produce values that are highly correlated with soil textur e and, by extension, forest productivity.