The influence of microhabitat variation on seedling recruitment ofChamaecyparis thyoides andAcer rubrum

Abstract

Chamaecyparis thyoides (Atlantic white-cedar) swamps are in decline in the New Jersey Pinelands, whileAcer rubrum (red maple) swamps are increasing. One possible reason for this occurrence may be differences in seedling recruitment of the two species. Seedling establishment of different species is expected to vary with physical conditions and requirements for safe sites. This study examined differences in seedling recruitment forC. thyoides andA. rubrum in the New Jersey Pinelands. A field survey of sixC. thyoides swamps found thatC. thyoides seedlings occur most often under an open orC. thyoides canopy on peaty, cedar needle covered soils or on mats ofSphagnum. In contrast,A. rubrum seedlings were most often found underA. rubrum canopies onSphagnum mats or grass-dominated bottom areas. A greenhouse experiment was conducted to determine whether differences in microhabitat occupation were related to differences in growth ofC. thyoides andA. rubrum seedlings. Seedlings were grown in different soil types (Sphagnum or peat) and at different water levels (inundated, saturated, or moist soil) typical of those found inC. thyoides swamps within the New Jersey Pinelands.Chamaecyparis thyoides experienced the greatest increase in height in moist soils and the least increase in height in inundated soils.Chamaecyparis thyoides achieved greater biomass thanA. rubrum in peat soil, whileA. rubrum had greater biomass inSphagnum. These results indicate thatC. thyoides andA. rubrum differ in conditions that are best for their seedling growth and that different management schemes may favor one species over the other.