Life Above the Trees

Sky Islands: treeline, alpine tundra, and life in the mountains

Jeffrey TaylorScience Instructor

Olympus High School

Get Your High School Diploma Online

13,000 foot Wheeler Peak, Great Basin NP, NV

Life Is Tough in the Mountains

Aletsch Glacier, Switzerland

Strong Winds, Cold Temperatures, Frozen Soil, Deep Snow, Summer Heat, UV radiation all take its toll…

Grand Ridge, Olympic NP, WA

Two Main Factors Affect Vegetation

Moisture and Temperature

Two Factors Affect Moisture and Temperature

Elevation and Aspect

Effect of Elevation: Topographic Lifting• As air rises over the mountains, it cools

• Cooler air causes water vapor to condense into clouds

• Clouds then drop rain or snow on the mountains

Rainshadow Effect

Rainshadow Effect

Coastal rainforests

Ocean

Windward

Drier intermountain trough

Leeward

Rainshadow Desert

Water From The Sky

West MauiWailuku at sea level gets 19” of rain while Puʻu Kukui at 5,300 feet gets 380” of rain!

5 miles 19”380”

Rainforests of Hawaii

Moloka’i Rainshadow

From Kamakou Peak at 4

The Effect of Topographic Lifting• Alpine Tundra Ecosystems• Desert Sky Islands• Ice Age Refugia• Snowpack Water Storage and Glaciers

Factors That Affect Treeline

For there to be alpine tundra, something has to prevent trees from growing

• There are 3 primary reasons trees can not grow;

• Snow Depth (summer growing season too short)

• Temperature (too cold)• Moisture (too dry)

Aspect and TreelineComparing the reasons why forests give way

to alpine tundra meadows

Aspect• The direction a slope faces.• North aspects are in the shadows all winter and thus stay

colder than south aspects.

South Aspect

North Aspect of the Trees in the Shade

Winter Solstice

Winter Solstice

Notice the long shadows and the valley in the dark all day

Spring Equinox

Spring Equinox

Shadows are not as long

Summer Solstice

Summer Solstice

With the sun directly overhead, there are almost no shadows

An Autumn Day

Shadows in October

The shadows are growing again

The Effects of Aspect

The snow is piling up on the northern side of the ridge

These trees are buried

Wind blows snow

The Effects of Aspect

Same spot in mid-summer, notice the lingering snow on north slope

North Versus South Aspect on High Divide in July

Forest growing on south-slopeBare on the north-slope

High Divide Other Side in July

The Build Up of Winter SnowpackFirst Snows in Early October

Late November

Early Winter AccumulationsLate December

Maximum Snowpack in Early SpringLate March

Late March

The Lingering Summer SnowpackEarly June

Early SummerMid-July

Mid-August

Late September

The Effect of Aspect on Treeline

Snowbank

Treeline

Dry Meadows

Wet Meadows

5500 feet

4500 feet

Tree Island

Pacific NorthwestSouthNorth

Sea Level

A Cross-Section of a Pacific Northwest Valley

Lowland ForestDouglas fir/western hemlock/grand fir

western red cedar/Sitka spruce

Montane Forestssilver fir/mountain hemlock/Douglas fir

Subalpine Forestsubalpine fir/yellow cedar

Alpine meadows

Lowland ForestSea Level to 2000 ft

Douglas fir/western hemlock/grand firwestern red cedar/Sitka spruce

Montane Forests2000 to 4000 ft

silver fir/mountain hemlock/Douglas fir

Subalpine Forest4000-5000 ft

subalpine fir/yellow cedar

Alpine meadows

5000-6500 ft

Glacier

Riparian Forestmaple/alder/willow

> 6500”Rock/Ice

Life in the Subalpine Environment

Subalpine Meadows

Subalpine Firs at the Edge

Subalpine Tree Islands

Other Factors Affecting Treeline

• TemperatureSome places are too cold for trees to grow

• MoistureSome places are too dry for trees to grow

1000

5000

10000-

15000

1000

5000

10000

15000

Arctic

Alpine/Tundra

Washington Oregon Central California Arizona Central MexicoSE Alaska

Deserts/semi-arid shrublands

Forests

Glaciers and Ice

Treeline Elevations of Western North America

treeline

Arctic Tundra

Alaska’s North Slope above the Arctic Circle

Treeline in the Arctic

Denali, Alaska

Treeline in the Rocky Mountains

-40° winter temperature line 12,000 feet

Notice no trees in the valley?

Treeline in the Rocky Mountains

Cold Air Sinks

Treeline in the Rocky Mountains

Cold Air Sinks

Low Treelines of the East

Cold Air Sinking Down from Canada

White Mountains, NH

Treeline in the Northern AppalachiansWhite Mountains in New Hampshire at 4,000 feet

Treeline in the Northern Appalachians

Mount Mansfield, VT at 4,000 feet

Treeline in the Southern Appalachians?

Mount Mitchell, NC is 6,700 feet

Predicted treeline would be nearly at 8,000 feet

Southern Appalachian BaldsRoan Highlands, NC at about 6,000 feet

Treeline in the Tropics

17,000 feet Mount Kenya at the Equator

Páramo in Colombia at 10,000 feet

Hawaiian TreelineClouds condense at 5,000 feet and above 8,000 feet it is like a desert

Mauna Kea and Mauna Loa 13,700 feet

Treeline on Mexican Volcanoes

Matlalceuitl Volcano, Mexico at 13,000 feet

Grazing Pressure on Treeline

Treeline is about 1,500 feet lower than it would be naturally

Monti Sibillini, Italy

Treeline in ItalyNorthern Apennines, Tuscany, Italy

4,500 feet

Treeline Elevations in the Northern Hemisphere

Desert Southwest Sky Island

Treeline

Montane Forest

Pine, Fir, and Spruce

Pinyon Pine – Juniper Zone

High Desert – Sagebrush Zone

Low Desert

SouthNorthSea Level

2000 ft

3500 ft

4500 ft

6000 ft

7000 ft

8500 ft

11500 ft

Desert Sky Islands

Spruce/Fir Forests at 9,000 feet

Sonoran Desert at 2,000 feet

Aspect in the Desert Southwest

Mount Graham at 10,000 feet

North Aspect in the Desert SouthwestLingering snow on Mount Graham’s north slope

South Aspect in the Desert Southwest

Snow is gone on south slope

Desert Sky IslandsView down to the desert from Mount Graham

Ice Age Refugia

Mount Graham Red Squirrel, AZ

Ancient Bristlecone PinesRed Spruce Forest in North Carolina

6,000 feet

11,000 feet

9,000 feet

Mountain Goats

Alpine Wildflowers

Thanks For Joining Me!

Mount Ellinor, Olympic Mountains, WA