Botany LS 1203 - Plant Biology
Biomes
Population:
group of individuals of a single species in a particular
location, generally viewed as capable of interbreeding
Community:
the various populations that share a particular location
Ecosystem:
the community members + abiotic factors (light, temperature,
precipitation, soil) that interact with each other in a particular location
the biotic components are usually categorized into trophic
levels of a food web: producers (autotrophs: photosynthesis,
chemosynthesis), consumers (heterotrophic: dining on producers, other
consumers, or both), decomposers (heterotrophic: break down organic
matter to a form from which elements can be re-assimilated by the producers).
Approximately 10 % of the energy (organic carbon) transferred between trophic
levels goes into the next level. The remaining energy leaves the biotic
component of the ecosystem as heat. Therefore, the most efficient use
of food energy
in a food web is to eat “low on the food chain” so as to minimize the number
of energy transfer steps. This strategy also reduces biological magnification.
Plant Successions
Plant communities change over time, with certain communities generally following each other because of the nature of the abiotic factors. These gradual changes in plant communities as environmental factors change over long spans of time result in successions.
Primary Succession: an area that has not been occupied before is colonized by organisms. The first organisms that establish themselves on either a bare substrate or in water form a pioneer community. The members of the pioneer community initiate soil formation. As these organisms grow and change their environment, they are replaced by successive communities called seral stages. Eventually, a long lasting community called a climax community can be reached. The climax community replenishes itself rather than giving way to another community as time goes by. Two types of primary successions are recognized: xerosere and hydrosere.
Primary succession in the Uinta Mountains in the present day Hudsonian Life Zone (timberline forest of Subalpine Fir and Engelmann Spruce) might be diagrammed like this:
Xerosere Primary Succession:
Rock --> Lichens (Pioneer Community) --> Mosses --> Annual Grasses --> Perennial Grasses and Forbes --> Shrubs --> Spruce/Fir (Climax Community)
Moisture: xeric to mesic
Hydrosere Primary Succession:
Glacial Lake --> Phytoplankton (Pioneer Community) --> Floating Aquatic Macrophytes --> Water Lilies --> Sedges/Rushes --> Grasses --> Shrubs --> Spruce/Fir (Climax Community)
Moisture: hydric to mesic
Secondary successions occur when a climax community is disturbed (fire, bulldozer, etc.) The plant community that arises following the disturbance will be of one of the earlier seral stages. A climax community is generally reached faster in a secondary succession than in a primary succession, often with some seral stages skipped. Also, the populations that make up the climax community might not be exactly the same in a secondary succession compared to a primary succession.
Biome:
a collection of similar ecosystems covering a large area
often found on more than one continent
limited in distribution by abiotic factors, esp. climate;
results in widespread areas of major plant forms as result of succession; therefore, biomes usually contain climax communities
classified by (and often named for) the plant communities
that are present; the specific plant species vary from place to place within
the biome and in other locations of the biome, but the vegetation types (conifer,
hardwood, grass, etc.) are characteristic of a specific biome
there are no clear boundaries between the biomes = overlap,
transition areas, altitude effects
usually limited to classification of terrestrial areas
7-17 recognized; you need to know these North American
biomes:
Tundra
Taiga (Northern Coniferous Forest, Boreal Forest)
Moist Coniferous Forest
Temperate Deciduous Forest
Southern Pine Forest (Southern Coniferous
Forest)
Grasslands (Prairie)
Mountain Forest Complex
elevation Life Zones:
Lower Sonoran Life Zone, Upper Sonoran Life Zone, Transitional
Life Zone, Canadian Life Zone, Hudsonian Life Zone, Alpine Life Zone
Desert (Hot and Cold)
Chaparral (Mediterranean Scrub)
Tropical Rain Forest.
For each Biome and Life Zone, you will be responsible for knowing vegetation
types, a few specific plants, climate factors, and location in North America.
You need to be able to indicate the locations of these biomes on a map of
North America. (to get an outline map of North America, go to
http://www.eduplace.com/ss/maps/pdf/n_america_nl.pdf)
For further information on biomes, visit the one prepared by Dr. Susan L.
Woodward of the Radford University (Radford, VA) Department of Geography :
http://www.runet.edu/~swoodwar/CLASSES/GEOG235/biomes/main.html
For more information on forest biomes, visit
http://www.cnr.vt.edu/dendro/Forsite/biomes.htm
The Biomes of North America
Tundra
found in the most northern reaches of Canada
permafrost: prevents water drainage; causes formation
of many shallow ponds and lakes; makes the ground marshy in the summer
very short growing season (2-3 months)
vegetation is usually evergreen; grasses, mosses, sedges,
lichens, small flowering herbaceous plants, low shrubs; usually treeless
Taiga (Northern Coniferous Forest, Boreal Forest)
Southern Canada and northern United States (Minnesota,
Wisconsin, Michigan, Maine)
still have some permafrost areas
long, cold winters with heavy snow
dominant vegetation: relatively small conifers -
generally <50 ft tall, 2 ft diameter - (spruce, fir, pine); hardwoods
(birch, aspen, willow, alder) in wet areas (lakes, ponds); very little undergrowth;
grasses, sedges, shrubs in open meadow areas
soil usually acidic and nutrient poor
short growing season, but longer than tundra (3-5 months)
Moist Coniferous Forest
Pacific Northwest (from Alaska down to northern California)
dominant vegetation: conifers, much taller than
in taiga: redwood, Douglas fir, Sitka spruce, lots of undergrowth.
fog provides a significant portion of the moisture needed
to support plant life
Temperate Deciduous Forest
from the Great Lakes south to the Gulf Coast states, from
the Mississippi River to the Atlantic Coastal plain
Hardwoods: oak, hickory, ash, maple, buckeye, sweet
gum (and formerly chestnut, elm). These trees are generally 60-100
ft tall. Smaller trees: dogwood, redbud. Lots of understory
and open meadows with grasses, annuals, shrubs (azaleas, rhododendrons)
abundant, year round precipitation: snowy winters,
wet springs and summers
generally moderate temperatures (compared to the Northern
Coniferous Forest Biome) with distinct seasons
soil: lots of humus from the leaf drop. was
very easy for settlers to clear (compared to the grasslands where they needed
to bust the sod)
Southern Pine Forest (Southern Coniferous Forest)
in many biome lists, this occurs as a region of the Temperate
Deciduous Forest
often viewed as not being the climax community that the
area is capable of supporting
essentially found in the southern states of the USA along
the Gulf Coast (including east Texas) and the Atlantic Coast from New Jersey
to Florida
milder winters than in the Temperate Deciduous Forest;
more humid as well
pine species; a few other conifers; some mixed pine-hardwood
areas. The collections of pines vary within the general region of the
biome: loblolly and shortleaf pines in the Piedmont, longleaf and slash
pines along the Gulf of Mexico
Grasslands (Prairie)
Mid-continent from southern Canada to north Texas
Tall grass prairie in the east; short grass in the west;
trees along waterways
sod = spread by rhizomes; more common in humid grasslands
bunch grass = spread by seeds; more common in drier grasslands
excellent soil with high organic matter; some of the richest
soil in the world
relatively light rainfall; therefore, soil nutrients are
not leached out
basically, too dry for trees and too wet for a desert
On other continents: veld (Africa), steppe (Eurasia),
pampas (South America)
Mountain Forest (Rocky Mountain Forest Complex)
Rocky Mountains, Sierra Nevada Mountains
different collections of tree types and species as climate
changes with elevation, therefore describe Life Zones: Lower Sonoran
Life Zone, Upper Sonoran Life Zone, Transitional Life Zone, Canadian Life
Zone, Hudsonian Life Zone, Alpine Life Zone
precipitation increases with elevation
1889. C. Hart Merriam. Described Life Zones based on patterns
of plant communities. Tried to correlate elevation and latitude; that
didn’t work out. Mostly used today for elevation vegetation patterns;
it works particularly well with plant communities in the Mountain West, since
this is the area Merriam based his system on.
Lower Sonoran Life Zone:
the hot deserts of the southwest United States and northwest
Mexico (Mojave, Sonoran, and Chihuahuan Deserts). Creosote bush, desert
shrubs, succulents. Found at elevations of 100 to 3,500-4,000 ft.
(see the Desert Biome below)
The other Life Zones are well described for the Uinta Mountains from the
field trip information packet. The pertinent information is repeated
below. See http://www.runet.edu/~swoodwar/CLASSES/GEOG235/lifezone/merriam.html#arcalp
for a description of the Life Zones as seen in northern Arizona.
From the Uinta Mountains Field Trip information:
Zonation of vegetation:
1. The largest portion of the state of Utah, at 4,000 to 7,000 feet
elevation is the desert shrub and foothill forest of pinion-juniper
zone. In addition to sagebrush and Utah Juniper on well-drained
areas, it includes shadscale, greasewood, and other types of shrubs on
poorly drained and often salty or alkaline soils. This Life Zone is
called the Upper Sonoran Life Zone.
(the cold desert. See the Desert Biome below.)
2. A transitional zone of mountain brushland or chaparral is found
at higher elevations than 7,000 feet, consisting of scrub oak, big-tooth
maple, Mt. mahogany, serviceberry, and chokecherry. In the Uinta
Mountains this zone also contains Ponderosa Pine and Rocky Mountain
Juniper trees. The Ponderosa Pine forests of Utah are not extensive
enough and trees not large enough to supply much lumber. Forests in
Utah provide watershed, cover for wildlife, and overstory for other
types of vegetation. It is not surprising that this Life Zone is called
the Transition Life Zone.
3. The main forest belt (called the Canadian Life Zone) of our mountains,
the montane forest is typified by White Fir, Blue Spruce, and Quaking Aspen
trees. Other trees such as Douglas Fir and trees from lower and upper
forest zones may occur here also.
4. The timberline forest of Subalpine Fir and Engelmann Spruce is located
just above the montane of our mountains. It is often referred to as
the Hudsonian Life Zone. In the Uinta Mountains this forest belt also
includes the Lodgepole Pine. This tree is not found in other parts
of the state of Utah.
5. The treeless vegetation above timberline on our highest mountain
peaks is referred to as the Alpine Life Zone. The Alpine Zone has a
latitudinal counterpart in the Arctic Tundra. Both consist mostly of
herbaceous plants, such as sedges, grasses, broad-leaved flowering
plants, and a few small woody shrubs, which do not get higher than the depth
of insulating snows.
Weber State University is located in the Upper Sonoran Life Zone or Cold Desert Biome (below).
Desert
Cold: Great Basin Desert. northern Arizona,
Nevada, Utah. Sagebrush, often with rabbitbrush. See the description
of the Upper Sonoran Life Zone above.
Hot: Sonoran Desert. Arizona, western Mexico.
Cacti that grow as columns, like the Saguaro. Also prickly pear, chollas,
barrel cactus.
Chihuahua
Desert. continental interior: southern New Mexico, southwest
Texas, central Mexico. Shrubs (Creosote bush, acacia), agaves, yuccas
Mojave
Desert. California, Nevada. Joshua trees.
Vegetation: xerophytes, phreaotophytes, succulents
(generally only in hot deserts because of the freeze damage in cold deserts;
exception: prickly pear), ephemeral annuals, perennial forbs with underground
bulbs; cryptobiotic soil crusts (see your prior notes on
cryptobiotic soil crusts)
hot summers, low precipitation (winter). Hot deserts,
precipitation is as rain; cold deserts, precipitation is as snow
Chaparral (Mediterranean Scrub, Sclerophyll Forest)
Central and southern coastal California, Baja Peninsula
hot, dry summers; wet winters
plants grow in winter and spring; dormant in the heat
of summer; well adapted to fire
coast live oak, manzanita; evergreen shrubs with small, leathery
leaves, often aromatic
fire adapted vegetation
many consider this biome to not have reached a climax community;
in areas where fires are suppressed, live oaks become established
Tropical Rain Forest
southern tip of Florida, Gulf Coast of Mexico, Central
America
no conifers; woody angiosperms, epiphytes (orchids, bromeliads);
multi-story vegetation with woody vines and other climbing plants, but the
understory is usually sparse (low light); some heterotrophic plants (like
some of the orchids we covered earlier; see your notes on
fungi)
very poor soil (nutrients tied up in the abundant vegetation)
year-round growing season; high precipitation
greatest species diversity of all of the biomes
Video: Private Life of Plants: Plant Politics. Take notes!!
Additional Web Links
When you look up biomes on the various web links, you will probably encounter variations in the names. For example, Eastern Deciduous Forest, Temperate Deciduous Forest, and Temperate Broadleaf Deciduous Forest all refer to the same biome.
Wayne's Word: Ecological Principles #1
Wayne's Word: Major Biomes of North America
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28 November 2006. Links checked 20 March 2011.