WRR, V 32, p 3175-3185, 1996
Mineral nitrogen transformations in and under seasonal snow
in a high-elevation catchment, Rocky Mountains, USA
Mark W. Williams
Department of Geography and
Institute of Arctic and Alpine Research
University of Colorado
Boulder, Colorado 80309
Paul D. Brooks
US Geological Survey
Fort Collins, CO
Kathy A. Tonnessen
National Park Service-Air Quality Division
In an effort to understand sources of nitrate
in surface waters of high elevation catchments,
nitrogen (N) transformations in and under seasonal snow were
investigated from 1993 to 1995 on Niwot Ridge,
an alpine ecosystem at 3,500m located
in the Colorado Front Range of the Rocky Mountains.
applied as non-conservative tracers to the snow showed
no evidence of nitrification in the snowpack.
movement through the amended snowpack was highly
correlated with a conservative chloride tracer
(r2 = 0.99).
In an unamended snowpack,
concentrations in meltwater before contact with the ground were highly
concentrations (r2 = 0.98),
consistent with no nitrification in the snowpack.
applied to the snowpack
was found in underlying soils,
released from snow can be rapidly immobilized.
Resin bag (mixed-bed ion-exchange resins)
measurements (N = 22) showed that
80% of the mobile inorganic N
in unamended subnivial soils was
Measurements of KCl-extractable inorganic N
from surface soils showed
that highest values were prior to the initiation
of snowmelt and lowest values were during the growing season.
abundance of unamended soils
was negative and ranged from -12 to -2,
suggesting that atmospheric deposition of
is an important component
of N cycling in these alpine soils.
These results suggest that soil mineralization under
seasonal snow, rather than snowmelt release of
concentrations in surface waters of high-elevation