Above- and below-ground characteristics of persistent forest openings in the New Jersey Pinelands

Openings in the pitch pine (Pinus rigida Mill.) forests of southern New Jersey may persist for decades. In five such openings, ranging in size from 22 to 223 m(2), and their surrounding forest matrix, we characterized the vegetation, the forest floor, root biomass, soil chemistry and soil fungi. There was a much greater disparity between the openings and the forest matrix in the density of small ericad shrubs than in the number or basal area of the canopy trees, and this disparity was mirrored in the thickness of the litter and organic horizons, and in the total small root biomass. The matrix:gap ratios of total root biomass and of total soil fungal length were similar to the ratios for tree and large shrub densities. Extractable NH4-N, Bray-P, pH, and soil moisture did not differ between the openings and matrix, but extractable NO3-N was higher in the openings than the intact forest. We suggest that the shrubs may be an important factor in maintaining the differences between the openings and the matrix, by trapping litter, maintaining high root biomasses, and inhibiting decomposition. If the organic horizon is destroyed in a locally intense disturbance, the slow rate of invasion and growth of the shrubs into mineral soil may help perpetuate the opening for long periods of time.