GROWTH OF CHAMAEDAPHNE-CALYCULATA AT 2 PEATLAND SITES IN RELATION TO NUTRIENT AVAILABILITY

Biomass production, length of current-season shoots, number of new shoots produced per plant, reproductive effort, and tissue-nutrient concentrations of the ericaceous evergreen Chamaedaphne calyculata (leatherleaf) were determined at two acidic peatland sites. Measurements were made under unfertilized conditions and following the addition of NPK over two consecutive years. The ''shrub'' site, a poor fen, had a deeper aerobic zone during most of the growing season, larger pools of N, P, K, Ca, and Mg within the surface peat (0-30 cm) and the leatherleaf biomass, and greater amounts of extractable P and K within the peat. At the poor fen, taller leatherleaf shrubs had significantly more biomass and longer shoots, and more flowers and fruits were produced. At the ''open'' site, a bog, leatherleaf plants doubled biomass productivity, shoot length, and allocation to reproductive structures, and increased the concentration of N, P, and K in current shoots in response to the addition of NPK. In contrast, leatherleaf at the poor fen site responded to the addition of NPK by only increasing the concentration of N, P, and K in the current shoots. These results suggest that the growth of leatherleaf may be limited by the availability of N, P, and/or K in bogs but not in poor fens.