Hurd, T.M., A.R. Brach, and D.J. Raynal. 1998. Response of understory
vegetation of Adirondack forests to nitrogen additions. Canadian Journal
of Forest Research 28:799-807.
Abstract: The influence of N pulses in the form of experimental
additions of HNO3 at two times ambient and (NH4)2SO4
at two and four times ambient on the herbaceous and woody understory plants
in three Adirondack Mountain hardwood forests was evaluated. Addition
of (NH4)2SO4 decreased cover of dominant
herbs and woody seedlings at Woods Lake, a site in the western Adirondacks.
Tissue N concentrations of combined herbs and ferns at Woods Lake increased
with addition of NH4 at both levels (9% at two times ambient;
13% at four times ambient) and increased with all three N treatments at
Huntington Forest, a central Adirondack site (14% with NO3 and
NH4 at two times ambient; 22% with NH4 at four times
ambient). Seedlings of American beech (Fagus grandifolia Ehrh.)
increased foliar N concentration 7-8% with NH4 treatments at
Huntington Forest, but did not respond to N addition at Woods Lake and
Pancake Hall Creek, a western Adirondack site. In general, greatest
plant nutrient response to N addition occurred at Huntington Forest, where
atmospheric inputs of N are lower than at Woods Lake and Pancake Hall Creek.