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The Niwot Ridge Mountain Biosphere Reserve:Tipping points in high-elevation ecosystemsin response to changes in climate an...
High-elevation areas are important  bellwethers of global change:   we need long-term research
Glaciatedvalley      SADDLE
External Drivers: Temperature Increasing air temperature since early 1980’s Summer air temps warming fastest Earlier la...
External Drivers: Precipitation Greater precipitation with increasing elevation Increases in the winter months (more sno...
External Drivers: N deposition• Increased rates of N deposition (wetfall)• N loading increases, despite drought
ARIKAREE         D1 CLIMATE     GLACIERROCKGLACIER                   GREEN                   LAKE 4                3,600 m
Earlier Snowmelt 2-6 days decade-1
Precipitation Effects on Streamflow   GL4               225-ha   MART               8-ha
Wet Year            vs.   Dry Year-Increasing subsurfacepathways.-- Snowmelt peak is notsnow – old, reacted water(talus + ...
Arikaree glacier is dying                              Drought                              Tipping pointArikaree Glacier:...
N dep + warming T = N saturation                  N Critical load:                  Aquatic                  4 Kg N/ ha/ y...
Stoichiometric controls on N-          cycling  Scatterplot of NO3- vs. DOC: NO3- ratio  for eight sites in Green Lakes Va...
Saddle site
how much N input does it take to produce a change in    species composition? (= N critical load using biotic              ...
species composition response:                      50    treatment x year P < 0.01                                        ...
Empirical estimation of N critical load for plant   species responses in alpine dry meadows       4    (% projected cover/...
Woody Willow Encroachment
Willow Encroachment Experiment             Factorial manipulation of N             (fertilizer), snow (snowfence),        ...
Shrub growth benefits fromincreased N, snow, and temperatureSalix growth in height after 2 years (cm)
Feedbacks to ecosystem processes Willow encroachment  increases litter, N availability,                                  ...
Summary• Disappearing glaciers• Snowmelt occurring earlier• Drought years little discharge because of  groundwater deficit...
QUESTIONS?
Remote sensing and isotopic analysis to determine the contribution of snow- and ice-melt to streamflow in the Nepal Himala...
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Remote sensing and isotopic analysis to determine the contribution of snow- and ice-melt to streamflow in the Nepal Himalaya [Mark Williams]

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Remote sensing and isotopic analysis to determine the contribution of snow- and ice-melt to streamflow in the Nepal Himalaya. Presented by Mark Williams at the "Perth II: Global Change and the World's Mountains" conference in Perth, Scotland in September 2010.

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Transcript of "Remote sensing and isotopic analysis to determine the contribution of snow- and ice-melt to streamflow in the Nepal Himalaya [Mark Williams]"

  1. 1. The Niwot Ridge Mountain Biosphere Reserve:Tipping points in high-elevation ecosystemsin response to changes in climate andatmospheric deposition Mark Williams, University of Colorado
  2. 2. High-elevation areas are important bellwethers of global change: we need long-term research
  3. 3. Glaciatedvalley SADDLE
  4. 4. External Drivers: Temperature Increasing air temperature since early 1980’s Summer air temps warming fastest Earlier lake ice-out dates 5ºC increase in 25 years
  5. 5. External Drivers: Precipitation Greater precipitation with increasing elevation Increases in the winter months (more snow) Summer drought starting in 2000
  6. 6. External Drivers: N deposition• Increased rates of N deposition (wetfall)• N loading increases, despite drought
  7. 7. ARIKAREE D1 CLIMATE GLACIERROCKGLACIER GREEN LAKE 4 3,600 m
  8. 8. Earlier Snowmelt 2-6 days decade-1
  9. 9. Precipitation Effects on Streamflow GL4 225-ha MART 8-ha
  10. 10. Wet Year vs. Dry Year-Increasing subsurfacepathways.-- Snowmelt peak is notsnow – old, reacted water(talus + baseflow) ispushed out by infiltratingsnow.-- Source of baseflowchanges and volumes arenot significantly different.
  11. 11. Arikaree glacier is dying Drought Tipping pointArikaree Glacier: Mass balance (Bn), cm water equivalent.
  12. 12. N dep + warming T = N saturation N Critical load: Aquatic 4 Kg N/ ha/ yrAnnual VWM concentrations of nitrate increase at all stream sites
  13. 13. Stoichiometric controls on N- cycling Scatterplot of NO3- vs. DOC: NO3- ratio for eight sites in Green Lakes Valley.
  14. 14. Saddle site
  15. 15. how much N input does it take to produce a change in species composition? (= N critical load using biotic response)Addressed experimentally inspecies rich dry meadow, usingadditions of 2, 4, 6 g N/m2/yr
  16. 16. species composition response: 50 treatment x year P < 0.01 Carex rupestris 40projected cover (%) N added: Carex rupestris 30 0 2 20 4 10 6 0 96 98 00 02 04 06 08 19 19 20 20 20 20 20 Treatment specific rate of change in cover similar response for Trisetum spicatum
  17. 17. Empirical estimation of N critical load for plant species responses in alpine dry meadows 4 (% projected cover/yr) change in Carex cover 3 2 1 0 -1 0 1 2 3 4 5 6 7 -2 -1 0.0 N input (g N m yr ) N Critical load: score (value /year) Change in DCA1 10-40 Kg N/ ha/ -2.5 yr -5.0 Whole community response -7.5 -1 0 1 2 3 4 5 6 7 -2 -1 N input (g N m yr )
  18. 18. Woody Willow Encroachment
  19. 19. Willow Encroachment Experiment Factorial manipulation of N (fertilizer), snow (snowfence), summer temperature (open- topped chambers), in all possible combinations + Addition of Salix glauca seedlings
  20. 20. Shrub growth benefits fromincreased N, snow, and temperatureSalix growth in height after 2 years (cm)
  21. 21. Feedbacks to ecosystem processes Willow encroachment increases litter, N availability, Net N mineralization (mg N/g soil/30 days) and snow depth. These effects may accelerate encroachment Absent Present Willows
  22. 22. Summary• Disappearing glaciers• Snowmelt occurring earlier• Drought years little discharge because of groundwater deficit• Increasing N deposition increases nitrate in streamflow• Critical loads for terrestrial veg 10 kg/ha/yr• Shrub invasion of alpine
  23. 23. QUESTIONS?
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