Alpine Vegetation

reference: Körner, Ch. 1999. Alpine Plant Life. Springer Verlag, Berlin

Some slides courtesy of Bill BowmanMountain 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

Boulder County: 1550 species(50% of flora of Colorado)

Weld County: ~600 species

Regional scale plant diversity in S. Rockies; the influence of mountains:

Nival

Alpine

treelineSubalpine

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

"Krummholz”: crooked woodslow growth (few inches trunk)

”Flag trees”

Windsnow

Forest-tundra transition: TREE ISLANDS

• Trees grow into bands

• form microsites -- reproduction occurs

Windward side:wind

Lee side:snow

World’s highest tree?

Quenual, up to 4,800m

Nival

Alpine

treeline

Subalpine

Montane

Elevation of treeline corresponds

with:1) minimum growing season

temperature around 6 °C

2) wind zone

3) geomorphic disturbance- avalanches

Global distribution of treeline

large variation in altitude at mid-latitudes

associated with continentality- treelines lower in moist, maritime locations

from Körner, 1999

Nival

Alpine

treelineSubalpine

Montane

Alpine Tundra: 11,200 to 12,000 ft

• Definition:

windswept, treeless area found at highest altitudes in the mountains

Niwot Ridge in May

cold (<0 deg C)

temperatures may change rapidly

windy (mainly temperate zone) 100 mph at Niwot Ridge!

Precipitation as snow

Alpine environmental conditions: CLIMATE

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

Cushion plants – Coropuna, Peruvian altiplano

Incas used them asfuel source

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

Note the leaves

Alpine environment summarized:

Cold + windysnowy!short growing seasonlow nutrient availabilityHigh 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

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.

Adaptation:•start to grow as soon as the snows melts•store food during the summer months•pollination strategies?

Summary

• 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

LIMITATIONS ADAPTATION