The effect of nitrogen and phosphorus enrichment on salt marsh community structure

Fertilization of a Batis maritima and Salicornia virginica dominated salt marsh in Florida, with a combined nitrogen and phosphorus fertilizer applied at four rates (50:8; 100:16; 150:24 and 200:32 kg/ ha/yr N:P) produced the following responses: 1) dominance shifted to Batis, 2) Batis aerial biomass increased from 428 g/m2 (control) to 1062 g/m² (highest rate) while Salicornia showed no positive response to fertilization, 3) highest fertilization plots had a 9% higher decomposition rate than control plots (.00728/day versus .00668/day), 4) no luxury consumption of nutrient was measured, 5) Batis stem biomass reached an asymptote of 750 g/m² (295 g/m2 control) after 2 years fertilization at 150:24 and 200:32 kg/ha/yr N:P, 6) Batis leaf biomass at 328 g/m² (133 g/m² control) had not reached an asymptote after two years fertilization. Measurement of initial changes in snail numbers and periphyton biomass and species composition, in response to fertilization could not be repeated,probably due to a drying trend in the marsh and a drastic reduction in snail and periphyton numbers.