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. Environmental change in alpine - primarily “indirect:”
climate, N deposition, stratospheric ozone degredation (↑UV)
locally most immediate threat is N deposition
William Bowman slide

4. GLOBAL PROBLEM: N DEPOSITION INCREASES

5. Regional Problem:Colorado ranks 3rd in U. S
Regional Problem:Colorado ranks 3rd in U.S. population growth, with most of the increase in the Front Range urban corridor:
source: William Travis
CU Geography

7. NITROGEN 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

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

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

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

12. NIWOT RIDGE NADP

14. 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

16. 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

17. Where in the alpine landscape is change most probable?
Snow is an effective reservoir of atmospheric N inputs
Moist meadows- elevated N
inputs due to topographic location
William Bowman slide

18. IONIC PULSE

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

20. 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

21. 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?

22. } 15N labeling experiment: + responder to N non responders
William Bowman slide

23. Implications of differential N uptake by alpine vegetation:
change in plant species composition ("weedy" native species)- may already be occurring
change in ecosystem properties:
> enhancement of N cycling (net N mineralization and nitrification) rates- loss of N from terrestrial to aquatic ecosystems
> greater climatic control (lower biological control) over variation in primary production
William Bowman slide