Alpine Vegetation- patterns of biodiversity and response to environmental change Bill Bowman- Ecology and Evolutionary Biology Mountain Research Station, INSTAAR reference: Körner, Ch Alpine Plant Life. Springer Verlag, Berlin

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

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 large variation in altitude at mid- latitudes associated with continentality- treelines lower in moist, maritime locations from Körner, 1999

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

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

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

Dominant sedgesCommon grasses Greenhouse experiment- artificial imposition of N limitation amount of growth is biologically constrained in some species

Alpine is an extensive biome- globally distributed

How has Pleistocene glaciation influenced alpine diversity and plant distribution?

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

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

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

Global Plant Diversity

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

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

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

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

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

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

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

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

 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 Implications of differential N uptake by alpine vegetation: