A Vegetational Description of a Mid-Missouri Forest Using Gradient Analysis Techniques

Several gradient analytical techniques were used to pro- vide rigorous ecological description of 75 forest plots in the Ashland Wild- life Area (AWA), Missouri. Tetrachoric correlation was used to construct a comparison matrix of the tree species. Gradients were then extracted from the comparison matrix using a principal components analysis. The model produced from the principal components analysis displayed vege- tational patterns evident in the area. The species principal component values were weighted, independently, by density, basal area and impor- tance value, to position the plots along the dimensions of the model. All three weighting variables yielded highly similar plot positions along a theoretical moisture gradient. Application of differential weighting to quantify direction and rate of compositional change, expressed as a vector, provided evidence that the forest composition of the Ashland Wildlife Area is becoming more mesic. A number of environmental variables were used as the third dimension on graphs of the plot posi- tions. Several environmental variables bear a definite relationship to species compositional patterns. A principal components model of the sapling and shrub species shows a few species shifting from xeric to more mesic conditions as compared to the tree model. This is verified by com- paring sapling densities of the dominant species. Acer saccharum is the leading sapling dominant in the Ashland Wildlife Area; and it appears likely that this species will eventually come to dominate the overstory of the present oak forests.

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