PUBLICATIONS
April 2002 Issue
The Geographical Review
April 2002, Vol. 92 (2), pp. 180-191
Alpine Areas in the Colorado Front Range as Monitors of Climate Change and Ecosystem Response
Mark W. Williams, Mark V. Losleben, and Hillary B. Hamann
Keywords: bighorn sheep,
biogeochemistry shift, climate change, Colorado, nitrogen, water
acidification.
ABSTRACT:
The presence of a seasonal snowpack in
alpine environments can amplify climate signals. A conceptual model
is developed for the response of alpine ecosystems in temperate,
midlatitude areas to changes in energy, chemicals, and water, based
on a case study from Green Lakes Valley-Niwot Ridge, a headwater
catchment in the Colorado Front Range. A linear regression shows the
increase in annual precipitation of about 300 mm from 1951 to 1996 to
be significant. Most of the precipitation increase has occurred since
1967. The annual deposition of inorganic nitrogen in wetfall at the
Niwot Ridge National Atmospheric Deposition Program site roughly
doubled between 1985-1988 and 1989-1992. Storage and release of
strong acid anions, such as those from the seasonal snowpack in an
ionic pulse, have resulted in episodic acidification of surface
waters. These biochemical changes alter the quantity and quality of
organic matter in high-elevation catchments of the Rocky Mountains.
Affecting the bottom of the food chain, the increase in nitrogen
deposition may be partly responsible for the current decline of
bighorn sheep in the Rocky Mountains.
Keywords: bighorn sheep,
biogeochemistry shift, climate change, Colorado, nitrogen, water
acidification.
ABSTRACT:
The presence of a seasonal snowpack in alpine environments can amplify climate signals. A conceptual model is developed for the response of alpine ecosystems in temperate, midlatitude areas to changes in energy, chemicals, and water, based on a case study from Green Lakes Valley-Niwot Ridge, a headwater catchment in the Colorado Front Range. A linear regression shows the increase in annual precipitation of about 300 mm from 1951 to 1996 to be significant. Most of the precipitation increase has occurred since 1967. The annual deposition of inorganic nitrogen in wetfall at the Niwot Ridge National Atmospheric Deposition Program site roughly doubled between 1985-1988 and 1989-1992. Storage and release of strong acid anions, such as those from the seasonal snowpack in an ionic pulse, have resulted in episodic acidification of surface waters. These biochemical changes alter the quantity and quality of organic matter in high-elevation catchments of the Rocky Mountains. Affecting the bottom of the food chain, the increase in nitrogen deposition may be partly responsible for the current decline of bighorn sheep in the Rocky Mountains.