Freezing Effects on
Carbon and Nitrogen Cycling in Northern Hardwood Forest
Soils
Caroline B. Neilsen, Peter M. Groffman,*
Steven P. Hamburg, Charles T. Driscoll,
Timothy J. Fahey, and Janet P. Hardy
Abstract
We evaluated the effects of freeze–thaw
events on soil respiration,nitrogen mineralization,
nitrification, and nitrous oxide production in soils
from a northern hardwood-dominated forest in New Hampshire,
USA. Soil samples from three horizons (Oe,
Oa, A) from nearly mono specific stands
of sugar maple (Acer saccharum Marshall)
and yellow birch (Betula alleghaniensis Britton) were
placed in 200-mL incubation vessels (microlysimeters),
subjected to severe (-13oC) and mild (-13oC)
freeze treatments for 10 d, and then incubated at
laboratory temperature (20–25oC)
for 3 wk. Evolution of CO2 and N2O
and concentrations of leachable NH4+ and
NO3-
3 were measured at weekly intervals. Freezing increased
rates of C and N cycling in these soils, but the effects
varied with species, horizon, and freeze treatment.
Whereas severe freezing stimulated respiration, N2o
flux, and mineralization, mild freezing had very few
effects. Nitrification did not appear to be affected
by either freeze treatment, but increases in denitrification
may have masked freeze effects on this process. Freeze
effects were much more marked in maple than in birch
soils and in the Oa and A horizons. Maple
consistently had higher rates of nitrification and
N2o production than did birch. The species
and horizon differences were likely driven by higher
levels of available C in the birch soils and Oe horizon
at both sites. These results suggest that changes
in climate and snow cover that influence soil freezing
ecosyscould
increase N and C losses from northern hardwood forest
ecosystems with potential effects on soil fertility
and carbon storage, receiving water quality, and atmospheric
chemistry.
Keywords:Acer
saccharum Marshall, Betula alleghaniensis Britton,N2O,Nitrogen
Cycling, Organis farming.
