Alpine Vegetation patterns of biodiversity and response to

Alpine Vegetation- patterns of biodiversity and response to environmental change Bill Bowman- Ecology and Evolutionary Biology Mountain Research Station, INSTAAR (william. bowman@colorado. edu) reference: Körner, Ch. 1999. Alpine Plant Life. Springer Verlag, Berlin

What is the alpine? Is it tundra? Nival Alpine treeline Subalpine Montane

elevation of treeline corresponds with: 1) minimum growing season temperature around 6 °C 2) wind 3) geomorphic disturbance- avalanches krummholz- "twisted wood"

Global distribution of treeline from Körner, 1999 large variation in altitude at midlatitudes associated with continentalitytreelines lower in moist, maritime locations

Alpine is a globally distributed biomeplants have similar "growth forms: " graminoids (grasses, sedges) forbs (broad leaved herbaceous plants) prostrate shrubs

Alpine environmental conditions: Ø cold Ø temperatures may change rapidly Ø windy (mainly temperate zone) Ø soils often poorly weathered Ø low water and nutrient availability Ø high UV irradiance (although offset by cloud cover) Ø low p(CO 2) - dependent on elevation

Adaptations to the alpine environment include: Ø being short Øhigh investment into belowground biomass (high root: shoot ratio) Ø low growth rates Ø tolerance to low temperatures (= intolerance of high temperatures)

Alpine is an extensive biome- globally distributed

How has Pleistocene glaciation influenced alpine diversity and plant distribution?

Continuous and isolated alpine habitat: Colorado interglacial (present) Glacial (ca. 20 K BP)

Biogeographic trends in Rocky Mountain alpine plant diversity ~ same number species more Arctic species to north more endemic species to south

Biogeographic similarities (after Hadley 1987) Sørenson’s index Beartooth (50 -83) Absoroka Gros Ventre 51 Teton Big Horn Wind River 58 51 54 Uintah Medicine Bow 48 59 Indian Peaks 44 50 Needles San Fransisco Peaks 34 Sangre de Cristos

Global Plant Diversity

Regional scale plant diversity in S. Rockies; the influence of mountains: Weld County: ~600 species Boulder County: 1550 species (50% of flora of Colorado)

MOUNTAINS • Have the highest plant species diversity • High mountain environments have a high percentage of endemic plants • Alpine areas have a much high plant diversity than forested areas

Alpine Mesotopographic Gradient (After Billings) Prevailing wind Fellfield snow Snowbed Moist Meadow Wet Meadow Similarity of flora among communities (Sørenson’s index): 25 -77% Dry Meadow

What controls variation in diversity across the landscape? soil resources?

Alpine plant diversity relationship to soil N+P availability on Niwot Ridge other factors: v disturbance (climate & animal) v water availability

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

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

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

15 N labeling experiment: } + responder to N non responders

Implications of differential N uptake by alpine vegetation: F change in plant species composition ("weedy" native species)- may already be occurring F 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