EFFECTS OF FERTILIZATION ON GROWTH AND NUTRIENT USE BY CHAMAEDAPHNE CALYCULATA IN A RAISED BOG

Biomass and flower production, shoot growth, and shoot N, P, and K concentrations of Chamaedaphne calyculata were determined in a bog in central Maine. Two separate field experiments were used to compare growth, reproductive output, and shoot nutrient contents of Chamaedaphne: (i) over two seasons under ambient conditions and following addition of N, P, and K individually and in combination; and (ii) during one season using a complete factorial design with three levels of both N and P. Biomass production and shoot length doubled following 1 year of N-P or N-P-K addition, whereas 2 consecutive years of addition tripled these characteristics. Growth responses were accompanied by an increase in tissue N, P, and K concentrations. The most striking response was a fivefold increase in the mass of flower buds produced per plant at the highest levels of N-P and N-P-K addition. The effects of N and P were interactive, and both the absolute quantity and ratio of N:P added were important in terms of the magnitude of the responses. Responses to N were typically curvilinear, whereas responses to P were both curvilinear and linear. Although Chamaedaphne is adapted to low levels of nutrient supply, it responds to the addition of nutrients by increasing the production of vegetative and reproductive tissue and by increasing the content of P in shoots. Without additional supplies of N, P, and K, growth by Chamaedaphne in bogs may be restricted by competition for nutrients with Sphagnum.