Association of Species and Their Relationship to Microtopography Within Old Fields

Abstract

The relationship of vegetational pattern to edaphic environment was examined within the old—field—prairie ecotone of a central Wisconsin drained marsh. Examination of several soil factors established significant correlations between the elevation gradient (with a range of 1.5 m) and organic matter content and moisture. Several species showed definite peaks of frequency and density across the elevation gradient with the invading prairie species predominating on the low ridges and wetland species largely restricted to depressions. Old—field species, such as Poa pratensis and Linaria vulgaris, were present on all topographic positions but appeared to be yielding to competition with the above species groups at the extremes of the elevation gradient. Pattern of species groups was further investigated by the use of normal association analysis. Environmental differences were tested between the resulting subdivisions of this analysis; this further documented the influence of microtopography on the distribution of the vegetation. In addition, organic matter levels were shown to be important in species distribution where differences in elevation were not in control. Normal association analysis and environmental correlation are considered in regard to the continual nature of plant distribution.