North American Plant Distributions:
Yesterday, Today, and Tomorrow

Mapping North American Biomes

All plants need certain resources for survival. And plants differ in their ability to tolerate various environmental factors. The distribution of plants is largely determined by their response to environmental conditions.

In the previous activity you discovered that patterns of diversity are associated with latitude. Some broad patterns of plant distribution are also associated with latitude, because on a global scale climate varies with latitude. Tropical climates form a warm wide belt around the equator. Climates become increasingly frigid toward the poles. At the same latitude, however, climate conditions are variable due to regional factors.

Below are climate data for two cities in Oregon, Portland and Bend. Notice the average temperature is given in degrees Celsius, rainfall in millimeters. Why?

Portland, Oregon 45ºN 122ºW,
6 meters above sea level
Month Temperature
(ºC)		 Precipitation
(mm)
January 4.2 133
February 6.4 105
March 8.5 92
April 10.5 61
May 13.9 53
June 17.5 38
July 20.1 15
August 20.3 23
September 17.3 41
October 12.5 76
November 7.8 135
December 4.5 149
Bend, Oregon 44ºN 121ºW,
1115 meters above sea level
Month Temperature
(ºC)		 Precipitation
(mm)
January 0.0 43
February 2.0 28
March 3.7 21
April 6.3 16
May 10.0 25
June 14.4 24
July 17.4 11
August 17.1 11
September 13.0 11
October 8.5 20
November 3.2 38
December 0.0 46


Plot these data in the climate diagrams provided. Then predict biomes for these regions.
Climate diagram for Portland, Oregon
ºC J F M A M J J A S O N D mm
23                         150
21.5                         140
19                         130
17.5                         120
16                         110
14.5                         100
13                         90
11.5                         80
9                         70
7.5                         60
6                         50
4.5                         40
3                         30
1.5                         20
0                         10
Climate diagram for Bend, Oregon
ºC J F M A M J J A S O N D mm
23                         150
21.5                         140
19                         130
17.5                         120
16                         110
14.5                         100
13                         90
11.5                         80
9                         70
7.5                         60
6                         50
4.5                         40
3                         30
1.5                         20
0                         10

Biome: _____________________ Biome: _____________________

Check your predictions against a biome map. How did you do?

It takes about 3.5 hours to drive from Portland to Bend, located in central Oregon. What regional factors make the climates of these relatively nearby cities different?

List at least 2 plant species that are characteristic of the biome in each region and adaptations of these plants to their environment.

Think about biomes a bit more...

Arctic tundra covers about 19% of North America. How do plants survive at such low temperatures and with such short growing seasons? Plants in alpine regions also face environmentally harsh conditions. How are conditions at high latitudes and high elevations similar?

There are three major desert formations in North America: the Mojave Desert, the Sonoran Desert, and the Chihuahuan Desert. Desert scrub also extends through the Great Basin region. Map the 3 major deserts and identify some plants common to each desert. Do the plants show similar adaptations to desert conditions? How do the deserts differ? Compare, for example, their rainfall patterns.

Grasslands of central North America are often called prairies. Do tallgrass and shortgrass prairies differ in ways other than height?

How does the temperate rainforest in the Pacific Northwest differ from a tropical rainforest? In what other parts of the world are temperate rainforests found?