1. MOUNTAINS AT RISK

2. Alpine areas: early warning indicators Organisms on edge of environmental tolerance Same processes as downstream forested and grassland ecosystems Less capacity! Less “buffering” Snow: moderates soil temperature, stores water and chemical, released at once

3. PROBLEM: N DEPOSITION INCREASES

5. NITROGEN CYCLE Plants are usually nitrogen limited Plants can only use inorganic nitrogen –Nitrate (NO 3 - ) –Ammonium (NH 4 ) 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

7. Albion Green Lake 4 Saddle Stream Como Creek NADP Site

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

9. Niwot Ridge NADP collector after a large snow storm.

10. NIWOT RIDGE NADP

12. IS INCREASING N DEPOSITION CAUSING CHANGES IN ECOSYSTEMS? WHAT KIND OF CHANGES SHOULD WE BE LOOKING FOR? WHERE WILL WE SEE THOSE CHANGES FIRST? STREAMS ARE ONE PLACE TO LOOK

14. STREAM WATERS AT RISK Episodic acidification is occurring Low alkalinity associated with high nitrate Occurs on the rising limb of the hydrograph Release of nitrate in the form of an ionic pulse in snowmelt increases problem of nitrogen in rain and snow

15. IONIC PULSE

16. IONIC PULSE: solute concentrations in meltwater greater than snowpack

17. SNOW 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

18. ALPINE 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?