THE VERNAL DAM - PLANT MICROBE COMPETITION FOR NITROGEN IN NORTHERN HARDWOOD FORESTS

Two days following isotope addition, microbial biomass represented the largest labile pool of N and contained 8.5 times as much N as Allium tricoccum biomass. Microbial immobilization of 15N was 10-20 times greater than uptake by A. tricoccum. Nitrification of 15NH4 + was 5 times lower in cores containing A. tricoccum compared to those without the spring ephemeral. Spring N retention within northern hardwood forests cannot be fully explained by plant uptake because microbial immobilization represented a significantly larger sink for N. Plant and microbial uptake of NH4 + may reduce the quantity of substrate available for nitrification and thereby lessen the potential for NO3 - loss via denitrification and leaching. -from Authors