MOUNTAINS AT RISK

Alpine areas: early warning Alpine areas: early warning indicatorsindicatorsOrganisms on edge of environmental

toleranceSame processes as downstream

forested and grassland ecosystemsLess capacity! Less “buffering”Snow: moderates soil temperature,

stores water and chemical, released at once

PROBLEM:N DEPOSITION INCREASES

NITROGEN CYCLENITROGEN CYCLE

Plants are usually nitrogen limited Plants can only use inorganic nitrogen

– Nitrate (NO 3-)

– Ammonium (NH4) Lots of nitrogen around

– Air is mostly nitrogen– Soils have lots of organic nitrogen

However, hard to convert organic N to inorganic N.

Thus, usually no nitrate in streams

AlbionAlbion

Green Lake 4Green Lake 4

Saddle StreamSaddle Stream

Como CreekComo Creek

NADP Site

Green Lake 4: View southwest towards Green Lake 4: View southwest towards Arikaree Peak (4008 m) from the shore Arikaree Peak (4008 m) from the shore near the outlet in late September.near the outlet in late September.

Niwot Ridge NADP collector after a large snow storm.

NIWOT RIDGE NADP

IS INCREASING N DEPOSITIONCAUSING CHANGES IN ECOSYSTEMS?

WHAT KIND OF CHANGES SHOULDWE BE LOOKING FOR?

WHERE WILL WE SEE THOSECHANGES FIRST?

STREAMS ARE ONE PLACE TO LOOK

STREAM WATERS AT RISKSTREAM WATERS AT RISK

Episodic acidification is occurringLow alkalinity associated with high

nitrateOccurs on the rising limb of the

hydrographRelease of nitrate in the form of an ionic

pulse in snowmelt increases problem of nitrogen in rain and snow

IONIC PULSE

IONIC PULSE: solute concentrations inmeltwater greater than snowpack

SNOW ENHANCES POLLUTIONSNOW ENHANCES POLLUTION

Stores pollutants for 6-8 months Pollutants released in several weeks Pollutants released as an ionic pulse– Concentrations in meltwater 5-10 greater than

average concentrations in snowpack

Snowmelt saturates subsurface, reducing infiltration

Pollution pulse goes directly into streams

ALPINE AREAS AT RISKALPINE AREAS AT RISK

Current levels of nitrogen deposition in the Colorado Front Range are causing changes in stream water quality

Nitrate values in streamwater may be a good indicator of ecosystem health

Are there terrestrial changes caused by nitrogen deposition?