Alpine Vegetation Some slides courtesy of Bill Bowman reference: Körner, Ch. 1999. Alpine Plant Life. Springer Verlag, Berlin Some slides courtesy of Bill Bowman Mountain Research Station, INSTAAR

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

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

Nival Alpine treeline Subalpine Montane

Mixed Aspen - Lodgepole Pine Forest : 8,500 to 10,000 feet yellow - green color foliage dense trees straight, pole-like Used by humans since prehistoric times light construction, finishing lumber, poles

Lodgepole pine needles attached to twigs in bunches paired, twisted long, green

Aspen only deciduous tree at this altitude grow in a variety of soil conditions from wet to dry

Subalpine Forest: 10,000 -11,000 ft spruce and fir dominate. narrow crowns dark green color cool,dark, humid E.g. Engelmann Spruce Humans have seldom used these forest due to their remoteness

Engelmann Spruce short needles attached to twigs rounded, spiky Spruce bark is reddish and outer layer flakes off

Rocky Mtn. Douglas Fir short needles attached to twigs; flat needles smooth bark

Forest- Tundra Transition: CLIMATE Situated between timberline and treeline (lower) (upper) Windier and colder mean annual soil temps ~ 0 deg. Snow covered

Forest-tundra transition: VEGETATION Wind snow "Krummholz”: crooked wood slow growth (few inches trunk) ”Flag trees”

Forest-tundra transition: TREE ISLANDS Trees grow into bands form microsites -- reproduction occurs Lee side: snow Windward side: wind

World’s highest tree? Quenual, up to 4,800m

Nival Alpine Subalpine Montane treeline

Elevation of treeline corresponds with: 1) minimum growing season temperature around 6 °C 2) wind zone 3) geomorphic disturbance- avalanches

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

Nival Alpine treeline Subalpine Montane

Alpine Tundra: 11,200 to 12,000 ft Definition: windswept, treeless area found at highest altitudes in the mountains Niwot Ridge in May

Alpine environmental conditions: CLIMATE cold (<0 deg C) temperatures may change rapidly windy (mainly temperate zone) 100 mph at Niwot Ridge! Precipitation as snow

Alpine environmental conditions: SOIL low nutrients in soil Rocky Thin soil cover low soil temperature ice present in the ground -- creates periglacial features “polygons”

Alpine Tundra distribution

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

Major life forms of alpine vegetation

Incas used them as fuel source Cushion plants – Coropuna, Peruvian altiplano

Note the leaves Puya Raimondi, Pastoruri (Peru) Blooms evey 40 years!

Alpine environment summarized: Cold + windy snowy! short growing season low nutrient availability High UV radiation How do plants survive in these conditions?

Plant adaptation to alpine environment (1) evolutionary adaptation (2) ontogenetic modifications, which are non-reversible during the life of an individual (3) reversible adjustment, often termed “acclimation”

4 things plants need: Liquid water nutrients warmth light Limiting factors in alpine and arctic tundra Limiting factor in arctic tundra only

Adaptations to cold 1) Cushion plants: grow in small, rounded humps conserve heat reduce wind chill

Adaptations to cold 2) Develop a blanket of white hairs protect them from cold at night White to reflect radiation during the day e.g. Giant Lobelia, in Kenya

Adaptations to cold 3) Keep dead leaves on the stem prevents ground from freezing e.g. Groundsel

Adaptations to cold 4) Grow short and small to avoid harsh winds and crushing snow the air temperature is warmer 10-15cm above the soil.

Adaptations to cold 5) Grow in balls that roll around w/frost heave, eg. Kenya moss deal w/expansion and contraction of soil due to freezing and thawing. Stone circles

Adaptations to cold 6) Rosette plants cabbage-like leaves surround a central bud winter: central bud is protected by the remaining vegetation.

More adaptations to cold high investment into belowground biomass (high root:shoot ratio) tolerance to low temperatures (= intolerance of high temperatures)

Cold-tolerant species examples Heaths: hard evergreen leaves that can withstand drying winds and cold temperatures. Common heaths: cranberries, blueberries, and rhododendrons

II. Adaptations to dry conditions Many high mountains plants are succulents, with water stored in thick leaves; minimize evaporation E.g. cactus

Adaptations to High UV irradiance Cover their leaves with white hairs (reflect the suns rays). Some plants contain a red pigment called anthocyanin which absorbs UV sunlight before it has a chance to damage the leaves.

Short growing season Cold nights short daylight hours 180 days/year Adaptation: start to grow as soon as the snows melts store food during the summer months pollination strategies? The Fireweed's seeds are plume- shaped. This allows them to ride on the wind before falling to the ground where they can take root.

Summary LIMITATIONS ADAPTATION Cold - grow short, close to ground - grow horizontally -cushion trees wind - grow in clumps (island trees) low nutrients -carnivorous UV -white hairs; antocyanin low growing seasons - grow fast; store nutrients; -pollination strategies dry -wax leaves