Shrub and Herb Continua of Upland Forests of Northern New Jersey

Abstract

The shrub and herb strata of 55 upland forest stands in northern New Jersey were studied. For the herbs, frequency and cover data were gathered by means of 0.5 x 2 m quadrats; for the shrubs, cover and frequency data were gathered on 5-rn line transects. Data were obtained from 36 to 48 points in each stand. Importance values were so calculated based on relative cover and relative frequency for shrubs and herbs as to give a total of 200. Using the method of leading dominants, climax adaptation numbers (ranging from 1 to 10) were assigned to 194 herbaceous taxa and 45 shrub taxa. The terminal shrub species were Lindera benzoin (10) and Gaylussacia baccata (1). The terminal herb species were Arisaema triphyllum (10) and Gaultheria procumbens (1). A continuum index number was calculated for each stand, with a possible range of 10 to 100. The shrub continuum shows a wide range of stand composition reflecting the broad spectrum of habitat conditions in the area, the index numbers ranging from 33-100. The herb continuum did not show as broad a pattern as did the shrubs, the continuum index numbers for stands based on the herbaceous layer ranging from 19 to 69. This was interpreted as primarily the result of (1) persistence in mesic forests of clonal relicts representative of earlier successional stages, the result being a dilution' effect on the true mesophytic forest herb composition of a stand and (2) the frequent disturbance, characteristic of the forests of northern New Jersey principally through wind throw and drought, which results in establishment of herbaceous species more characteristic of earlier successional stages.