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Images (c) by James L. Reveal, Norton-Brown Herbarium, University of Maryland, unless otherwise credited.
BSCI 124 Lecture NotesDepartment of Plant Biology, University of Maryland
LECTURE 35 - TERRESTRIAL BIOMES
Montane coniferous forest near Kebler Pass, Colorado
I. Introduction
The North American continent is the home of a diverse array of plants and animals all occupying a multitudeof ecological sites in a variety of climatic regimes. The biota of North America - the sum total of its livingcreatures - when considered in relation to climatic, soil and physiographic features allows biologists torecognize grand associations that are termed biomes.
The purpose of the two lectures on biomes is to provide the student with an awareness of life from the arcticto the tropics. Our goal is to make you, the young men and women who are the future, cognizant of theliving creatures, the land, and the environment of the planet.
To understand the present flora, it is useful to understand in broad terms the fate of the flora over the last18,000 years. The flora of North America has changed significantly insofar as its distribution is concernduring this short period of time in the earth's history. A large mass of ice dominated much of the northernthird of the continent. Unglaciated regions in Alaska allowed not only numerous plants and animals tosurvive in refugia, but provided a broad avenue for people to enter onto a new land. Much of the native florawas compressed in front of the ice sheet, the vast taiga of today was little more than a narrow strip along thefront and down the backbone of the Appalachian Mountains.
The eastward expansion of the eastern coast of the United States onto the Atlantic ocean shelf, andespecially around Florida, proved to be an escape route for species to survive. In the West, deserts weremore southerly, and the grasslands more compact.
By 8,000 years ago, a vast warming trend had significantly reduced the size of the ice sheet, with the tundraand taiga expanding rapidly northward as the ice retreated. On the Great Plains, the grasslands movednorthward, the southern tip being equally rapidly replaced by desert conditions. In the West, cold desertvegetation expanded northwardly to a degree, but mainly elevation up slope and, in the Great Basin, ontothe floors of the now dried pluvial lake beds.
Present-day biomes were rapidly establishing starting some 5,000 years ago as the climate cooled to itspresent norm. The tundra continued to move northward, expanding onto the Arctic slope as the icecontinued to melt. The taiga proved to be an effective barrier to the northward expansion of both thegrasslands of the Great Plains and the deciduous forest in the East.
In the west, the Chihuahuan and Mojave deserts became established in their present position, and thenorthward expansion of the Sonoran Desert was halted by a combination of cooling climates andtopography. The rapid desertification in the West, coupled with the survival of plants and animals in smallrefugia or nunataks resulted in a diverse modern flora.
Diversity in terms of species is far greater in the American West and the Deep South, where the sheer forceof the ice sheet was less compared to that in the Northeast and most of Canada. The geologically ancientflora of the Southeast survived by virtue of its position on the continent; that of the West underwent rapidand profound speciation resulting in a multitude of kinds.
Biome map of the world from Missouri Botanical Garden
For a map of the biomes of North America, see this site
II. Definitions & Role of Climate
DefinitionBiogeography: the study of animal and plant distributions; known as zoogeography and phytogeography,respectively.
1.
Biome: any one of the several major ecosystems which may be characterized by the presence of specificplants and animals, climate, and soil conditions in a specific geographic setting. In terms of area, it iscomposed of several plant communities and ecosystems. The boundary between biomes is termed anecotone and may be important in our understanding of speciation and dispersal. Many plants in a given
2.
A.
biome may be an endemic, that is found no where else in the world; biological diversity differsconsiderably between biomes.The biomes of North America are: (1) tundra, (2) taiga, (3) montane forests, (4) temperate rain forests, (5)mixed conifer and sclerophyllous hardwood forests, (6) temperate deciduous forests, (7) chaparral, (8)grasslands, (9) deserts, (10) tropical forests.
3.
The world as a whole is often divided into six biogeographic kingdoms:Boreal kingdoma.Paleotropical kingdomb.Neotropical kingdomc.South African kingdomd.Australian kingdome.Antarctic kingdomf.
4.
Role of ClimateBiomes controlled by climate: extremes of temperatures and precipitation more significant than averages.1.Daily and seasonal cycles influence prevailing winds.
Climate is global and is ever changing.a.Important features include the jet stream and the associated cloud patterns as well as ocean currents;the seasons of the year are determined by the tilt of the earth.
b.
Weather moves west to east in North America.c.Precipitation influenced by physiographic features - distribution, size and height of mountain ranges,locations of oceans, etc., the amounts differing from biome to biome.
d.
2.
ElevationBiomes at higher elevations in more southern latitudes.a.With sufficient elevation, numerous biomes can be found on a single mountain range.b.Often subdivided into "life zones".c.
3.
Change over timeClimatic changes over last 21.000 years.a.Tectonic plate movement over long periods of time.b.
4.
Frozen tarn pond in alpine tundra near Dillon, Colorado
B.
III. Tundra
Location:A.
Northernmost and circumpolar in northern hemisphere.1.Northern Alaska and Canada, all of Hudson Bay in east.2.
Features:Dry: (6-14 in or 15-35 cm) as summer and fall cold rains.1.Cold: Freezing temperature can occur any day of the year and temperatures rarely exceed 15° C even duringthe warmest of months. The growing season varies from 60 to 100 days a year.
2.
Soils: Wet, shallow, often frozen or with permafrost; shallow lakes, known as polygons3.One physical feature of the region (both here and in the montane biome) is the force of glaciation caused bya glacier. Glaciers are particularly impressive and massive in Antarctica. The consequences of past glaciationmay be seen in the Sierra Nevada of California - see image.
4.
Vegetation:Low shrubs and herbs, mostly graminoids - grass-like plants.1.Some 700 species.2.Defined by a distinct tree line3.
5.
Animals:Migratory birds, especially water birds.1.Predators: wolves, arctic fox, weasels, owls, etc.2.Large mammals: bear, caribou (New World) or rain deer (Old World), musk oxen, polar bear and Dallsheep.
3.
Small mammals: voles, lemmings4.Insects: Black flies, mosquitoes, gnats5.Low diversity and productivity6.
6.
History:Most (but not all) of the area dominated by last continental ice sheet ("Laurentide Ice Sheet"); effectsended about 4000 years ago.
1.
Vegetation moved northward forming "high" and "low" tundra.2.
7.
Exploitation:Habitat destruction due to exploitation of natural resources.1.This "frozen" or "polar desert" requires centuries to recover.2.Possible impact from global warming which is having a greater impact in the tundra than elsewhere.3.Threat of pollution.4.
8.
Southern Taiga Forest or Boreal Forest - Michigan
IV. Taiga
Introduction: The boreal (meaning northern) forest region occupies about 17 percent of the Earth's landA.
B.
surface area in a circumpolar beltLocation:
Circumpolar in northern hemisphere.1.Alaska and Canada to northeastern and Great Lakes region of the United States.2.Area often characterized as "boreal forest", "northern coniferous forest" or "Cold Climate Forest".3.
B.
Features:Forest dominated by densely arranged dark evergreen conifers; an effective "carbon sink".1.Little moisture (17-20 in or 40-50 cm) mostly as summer rains.2.Freezing temperature, extreme cold (-100° F are not uncommon). The temperature rarely exceeds 85°F in the summer. The growing season is 90 to 120 days per year. Snow is common.
3.
Shallow soils, wet, deep permafrost; nutrient poor.4.Fire is an occasional factor.5.
C.
Vegetation:Northern edge defined by a timberline1.Trees include both softwoods (conifers) and hardwoods (flowering plants)2.Other plants: Shrubs include willows and members of the heath family (Ericaceae) but not Erica thetrue heath.
3.
Graminoids (mainly grasses), lichens and bryophytes (Sphagnum).4.Succession: Shallow ponds or lakes to peat bogs to graminoids to shrubs to trees.5.About 1800 species of vascular plants6.
D.
Animals:Large mammals: Elk, caribou, deer, bear (brown, grizzly).1.Predators: Wolves, bear, lynx, wolverine, fox.2.Birds: Migratory and some resident birds, especially song birds.3.Insects: black flies, midges, gnats and mosquitoes4.
E.
History:Most of the biome covered by repeated series of continental ice sheets, the most recent being theWisconsin Ice Sheet which reached its height about 25,000 years ago, persisted until about 12,000years ago, and declined over the period 10,000-7,000.
1.
Ancient Lake Agassiz existed before the present-day Great Lakes2.Refugia (sing. refugium): areas where plants and animals escaped the effects of glaciation; landbridge across the Bering Straits between Siberia and Alaska, "islands" as in central Alaska and the"driftless" area of Wisconsin, and escape routes along the Pacific coast of Alaska.
3.
Nunataks: Isolated mountain tops or ridges that were unglaciated; resulted in many endemic anddisjunct populations
4.
F.
Exploitation:Hunting is leading to a loss of many species, especially fur-bearing animals.1.Mineral exploitation resulting in habitat loss and pollution.2.Fire: mainly natural and part of the succession process.3.Lumbering: may be a threat in the near future.4.Productivity limited by cold and varies greatly throughout the region5.
G.
Montane Coniferous Forest, Wind River Mountains -- Wyoming
V. Montane Forests
General featuresMost complex biome in North America; widespread in the world.1.Fragmented in three major montane cordillera, each with a distinct fauna and flora; composed ofmany subcommunities or associations.
Appalachian Mountainsa.Rocky Mountainsb.Sierra Nevada-Cascade Rangesc.
2.
General trending north/south, high elevation.3.Moist west slope, dry eastern slope - rain shadow effect.4.Influenced by recent glacial events; refugia and/or escape routed.5.Composed primarily of conifer species; often with some hardwoods6.Fire is often a major factor.7.Temperatures warmer than tundra, but often as cold and much more windy.8.
A.
Appalachian MountainsLocation: Higher mountains and ridges stretching from Vermont and New Hampshire to the SmokyMountains of Tennessee and North Carolina.
1.
Features:Conifers and deciduous hardwoods.a.Elevations most 2600-6000 ft (800-1800 m)b.Cool; average winter temperature is about 23° F, average high for the warmest month around60° F. Extremes can reach -30° F and more than 100° F.
c.
Precipitation 60-100 in (150-255 cm); snow and rain; summer snow rare.d.Soils shallow and often over bedrock.e.
2.
B.
Rocky MountainsLocation: A massive complex from northern Alberta, Canada, to New Mexico, defined by the GreatPlains in the east, western edge less sharply demarcated. North of South Pass, Wyoming, termed the"Canadian Rockies" to the south "Colorado Rockies." Includes isolated ranges in Idaho and Utah.
1.
Features:Numerous conifers and some deciduous hardwoodsa.Numerous ranges over 13,000 ft (4000 m) in elevation; "parks" - broad valley bottoms - occurabove 9000 ft (2750 m).
b.
2.
C.
Well-marked timberline.c.Precipitation (15-60 in or 40-150 cm) falls mainly as winter snow. Dry summers with lighteningstorms
d.
Variable soils.e.Heavily glaciated with localized ice caps; glaciers and snow fields present today; numerousrefugia and nunataks formed.
f.
Timberline has changed latitudinally and elevationally over time.g.Hot, rapid fires have played a major role; "crown fires" can created their own fire storm.h.
Sierra Nevada-Cascade RangesLocation:
Sierra Nevada: continuous mountain range restricted to California and the Lake Tahoe region ofNevada.
a.
Cascade Ranges: southern Oregon to British Columbia as a series of fragmented, volcano-dominated montane islands; transitional ranges join the two in northern California.
b.
1.
Features:Large conifers of numerous and diverse kinds, many deciduous hardwoods.a.Many peaks over 14,000 ft (4270 m).b.Cool, moist winters and seasonable summers.c.Precipitation mainly as winter snows, 10-50 in (25-125 cm).d.Variable soils; granitic and volcanic soils common.e.Great diversity of plants and animals, many endemics.f.Fire a significant factor with many species adapted to fire.g.Gentle, moist western slope; steeper, drier eastern slope.h.Numerous volcanic peaks (e.g., Mount Rainier and Mount St. Helens).i.
2.
D.
VegetationMostly dense stands of conifers with scattered hardwoods1.Many shrubs mainly in moist areas2.Scattered meadows with a diversity of graminoids.3.
E.
ExploitationLogging, especially in the Appalachian Mountains, most climax forests now cut1.Recreation pressures increasingly a threat, especially to the herbaceous flora2.
F.
VI. Temperate Rain Forest
Location: Pacific Coast from southern Alaska to central California.A.Features:
Mostly coastal and in low mountains (less than 9,000 ft)1.Abundant precipitation, rain and snow; 25-160 in (65-400 cm).2.Cool temperatures, rarely below 5° F or above 100° F; moister and cooler in the north. Fog animportant component.
3.
Soils are deep and rich but mineral poor.4.Fire can be significant albeit usually not devastating to larger trees.5.A fair diversity of plants and animals.6.
B.
Vegetation:Diversity of conifers and hardwoods, many tall and old. Pines, fir, spruce, redwood and Douglas fir.Old growth forest was common; now reduced to about 10% of original.
1.
Numerous species of shrubs and wild flowers. Many endemic.2.
C.
Animals:Numerous resident birds and animals.1.Some fur-bearing species (seal and otter) were common.2.
D.
History:Ancient, relictual forest, many "living fossils" - plants whose ranges were once much more widelydistributed.
1.
Many related plants also found in Southeast Asia.2.Position of forest not affected by Pleistocene glaciation3.Many species adapted to slow burning fires (thick bark of redwood).4.
E.
Exploitation:Lumbering has dramatically reduced the extent of the forest; "clear-cutting" generally no longerpracticed.
1.F.
Fire suppression in recent years has increased losses due to wild fire.2.
VII. Mixed Conifer and Sclerophyllous Hardwood Forests
Location: mountains of northern Mexico, and most notably that found in the Sierra Madre Occidental and SierraMadre Oriental.
A.
Features:Warm seasonal rains, some snow; mostly 30-50 in (75-150 cm)1.Moderate temperatures, but freezing temperatures in arid alpine zones atop volcanic peaks in the "trans-volcanic belt"
2.
B.
Vegetation:Mixture of numerous species of conifers and hardwoods1.Many hardwoods and large shrubs (to 30 ft high) with small ("microphyllous"), leathery ("sclerophyllous"),often evergreen leaves.
2.
C.
Animals: Mixture of temperate and subtropical forest and desert species.D.Exploitation: Historically an area of small farms and limited grazing with some mining (generally without erosionor pollution control); now being intensively cut for timber.
E.
Fall foliage near the University of Maryland Campus, Maryland
VIII. Temperate Deciduous Forests
Location: Eastern portion of North America. Bounded on the east by the coastal plain along the Atlantic Ocean,the Great Plains on the West, the taiga in north and the Gulf of Mexico in the south.
A.
Features:Composed of numerous, well-defined vegetation associations dominated by deciduous trees and shrubs.1.Variable climate, warmer and wetter in the south
Precipitation 30-60 in (75-150 cm) annually, mostly as raina.Growing season of 120 (Canada) to 250 (Florida) days.b.Temperature extremes can be significant: -20 to -40° F to 100 to 110° F.c.Hurricanes and freezing rain can cause considerable physical damage to the vegetation.d.Soils more acid and fertile in north.e.
2.
B.
Composed primarily of hardwoods with a mixture of conifers.3.Fire a major factor in maintaining the forest and diversity of herbs and shrubs on the forest floor4.Biome once wide spread across all of North America and Eurasia; flora similar to that of China today.5.
Vegetation:Variety of hardwoods: Quercus (oak), Acer (maple), Fagus (beech), Tilia (basswood), Castanea (chestnut),and Carya (hickory). Tulip poplar (Liriodendron) also common.
1.
Scattered conifers mostly pines.2.Numerous shrubs, many of the heath family (e.g., Rhododendron (left), Kalmia; blueberries (Vaccinium)also common.
3.
Numerous grasses and wild flowers throughout the growing season.4.
C.
Animals:Mammals: Deer; moose and bear were common; historically buffalo in the area. Raccoon and opossumcommon, so are skunks.
1.
Predators: Fox common; bobcat or lynx rare; wolves and mountain lion extirpated.2.Birds: Resident and migratory; numerous song birds and waterfowl.3.
D.
History:Only northern section directly glaciated; vegetation pushed southward into northeastern Mexico and outonto what is now the continental shelf as sea levels were lower than at present.
1.
Southeast flora not subject to extensive extinction so many relictual genera and species still persist.2.Chesapeake Bay and Great Lakes began to form some 10,000 years ago.3.Pine Barrens of New Jersey not affected by glacial epoch and flora remained in place.4.Isolated pockets of montane forest vegetation on coastal plains.5.
E.
Exploitation:No undisturbed forest present today due to extensive logging.1.Introduction of Chinese chestnut into New York Zoological Garden resulted in a fungal disease thatdestroyed the American chestnut.
2.
Clear-cutting of forest for farming coupled with introduction of exotic weed species has fundamentallyaltered the flora.
3.
Soil erosion and depletion has made it difficult for some species to re-invade disturbed sites.4.Erosion has resulted in silting and deposition in wetlands; some 90% of the wetlands in Maryland have beendestroyed.
5.
Numerous species of plants and animals have gone extinct or have been extirpated over significant portionsof their native range.
6.
F.
IX. Chaparral
Location: Coastal southern California and northern Baja California, Mexico. Widely scattered elsewhere in theworld: southern Europe and northern Africa, Cape Region of southern Africa.
A.
Features:Dominated by microphyllous (small), sclerophyllous (e.g. leathery), xerophytic (dry) evergreen shrubs anda mixture of low conifers and hardwood trees.
1.
Climate: Cool and wet in winter; hot and dry otherwise.Precipitation as rain in late Nov to early Apr, 14-29 in (35-75 cm); falls as rain or rarely as snow.a.Seasonally warm in winter, hot in summer, frost infrequent, can exceed 110° F.b.
2.
Slope and exposure critical; moist north-facing, dry south-facing; slopes usually steep.3.Hot winds and fire frequently occur in late fall at end of dry season.4.Generally poor soils, shallow and rocky.5.Fire climax community.6.
B.
Vegetation:Dominant shrubs are chamise (Adenostoma fasciculatum), California buckwheat (Eriogonum fasciculatum),various species of manzanita (Arctostaphylos), and (at higher elevations) species of ceanothus (Ceanothus).
1.
Dominant trees are oaks (Quercus) and pines (Pinus).2.Many endemic species of wildflowers; flowers most common from March to June.3.Many species have volatile oils in the leaves meaning that they burn rapidly.4.Many species specially adapted to repeated burning (e.g., root crowns ("lignotuber") from which new shrubscan grow; cones of pines ("cone serotiny") that require high heat to open.
5.
C.
Animals:Diversity of birds, especially ground birds, deer and small mammals.1.Many species of both plants and animals are narrowly endemic.2.
D.
History:Chaparral a more southern biome, moved to its present position during Pliocene and Pleistocene times,becoming less expansive.
1.
Formed as a result of drying trend over last 10 million years.2.Frequent fires have done much to maintain biome.3.
E.
Exploitation:Intensively grazed has resulted in some extinction.1.Fire suppression is resulting in larger and hotter fires that kill plants otherwise adapted to fire.2.Population growth coupled with urban expansion is fragmenting the vegetation.3.
F.
Mid-grass prairie near Ottawa, Kansas
X. Grasslands
Location: Major grasslands are widely scattered, covering nearly a quarter of the landed surface: North America("prairie") Russia ("steppes"), South Africa ("veld"), Argentina ("pampas").
A.
Several grasslands are found in North America:Great Plains1.Palouse Prairie2.California grasslands3.
B.
Features:Dominant plants are members of the grass family (Poaceae), several genera and species common but usuallywith one or two dominate.
1.
Most grasses are rhizomatous (possessing rhizomes) and are wind pollinated.2.Moderate temperature but notable extremes: -20° F to 110° F common, and even colder temperatures in thenorth.
3.
Variable precipitation: 6-40 in (15-100 cm).4.Soils generally fertile, deep and rich; variable5.Growing season of 120-200 days.6.Generally flat to rolling topography cut by stream drainages where there is a riparian or river-bank habitat.7.Scattered rain and lightening common in summer months ("convection storms") with more general rains andsnows in winter months.
8.
Fire a major factor in maintaining biome.9.
C.
The Great Plains:Location: Alberta, Saskatchewan and Manitoba in southern Canada southward to northern Mexico from1.
D.
eastern Chihuahua to Tamaulipas.Features: Divided into three associations
Short-grass Prairie - western unit with short grasses.a.Mid-grass Prairie - central unit with mid-sized grasses.b.Tall-grass Prairie - eastern unit with tall grassesc.Climatic zones with grasslands drier in the west and much wetter in the east.d.
2.
Animals: Dominated by grazing animals (deer, antelope, buffalo - once common but now rarely native to therange) and song birds that sing on the wing. A common animal is the prairie dog. The black-footed ferret is anotable rare species.
3.
History:Northern third extensive glaciated.a.Grassland pushed well to the south (where the Chihuahuan Desert is today) during last ice age, movednorthward during Late Pleistocene and Early Holocene.
b.
Grazed by migratory animals; these eventually hunted by humans.c.Numerous Indian tribes occupied the grasslands.d.
4.
Exploitation:Majority of tall- and mid-grass prairie now farmland.a.Short-grass prairie grazed, some areas now overgrazed.b.
5.
Palouse Prairie:Location: Eastern Washington and portions of adjacent Idaho and Oregon. Scattered elsewhere as in parts ofnorthern Utah.
1.
Features: Short grasses, diverse, lots of wild flowers; mixed with shrubs.2.Vegetation: Mixed grasses and shrub, especially sagebrush (Artemisia tridentata).3.Animals: Deer and antelope today; buffalo, camels, horses and mammoth along with an array of predatorssuch as great cats and wolves into early Holocene.
4.
History: Always small but now invaded by desert species.5.Exploitation: Dry-land farming and grazing.6.
E.
California Grasslands:Location: Two areas: Central Valley and coastal California.1.Features:
Central Valley: dry, dense grasses and scattered hardwoods on margins.a.Coastal: moist, fog-influenced, meadow-like with shrubs.b.
2.
Vegetation:a. Central Valley: Grasses and scattered trees.b. Coastal: Grasses: Grasses and scattered shrubs.
a.3.
Animals: Deer, antelope, elk and buffalo were common, only deer still common. Numerous birds includingmany species of waterfowl.
4.
History: Long-term areas with little or no impact from recent glaciation.5.Exploitation: Central Valley grassland almost totally converted into farm land. Coastal grasslands beinginvaded by expanding urbanization. Grazing and exotic weeds major problems in some areas.
6.
F.
Cold desert of the Great Basin near Lunar Crater, Nevada
XI. Deserts
Introduction:Desert: characterized as regions of seemingly low, sparse vegetation with minimal precipitation andhumidity, high temperatures during some of the year, and great daily fluctuations in temperatures.
1.
Usually of temperate or subtropical regions.2.Desert formation a function of climate and topography.3.Deserts slow to recover from habitat damage; it is still possible to find wagon tracks from the 1840s innorthern Nevada. Indian encampments are often easy to spot because the vegetation has still not recovered.
4.
Numerous unusual plants and animals make the desert home, many of them are endemic.5.Three major types: cold, warm or hot depending upon overall annual temperature.
Cold Deserts: Arid regions where precipitation falls sparingly principally as snow and permafrost isnot a factor; vegetation is primarily xerophytic and sclerophyllous shrubs with scattered, low trees.
a.
Warm Deserts: Arid regions where precipitation falls seasonally principally as rain, some snow andfrost each year; vegetation is xerophytic and sclerophyllous shrubs with scattered trees or arborescentcacti.
b.
Hot Deserts: Arid regions with little or no annual precipitation, usually rain, no snow or frost;vegetation sparse and scattered, often limited to moist areas, or even lacking entirely except followingperiods of adequate regional moisture. Not found in North America
c.
6.
A.
Four deserts in North America:Intermountain Westa.Mojaveb.Sonoranc.Chihuahuand.
B.
Cold Desert
Location: In North America, the cold desert bounded by the Sierra Nevada on the west and Colorado Rockies onthe east, and by the Idaho batholith of central Idaho on the north and generally a vegetational line defined bycreosote bush (Larrea divaricata) - a warm desert species - and Great Basin sagebrush (Artemisia tridentata) inthe south.
A.
Features:Precipitation falls primarily as winter snow. Summer showers can be heavy and cause local "flash floods" inmany areas.
1.B.
Temperature cool (rarely below -15° F) in winter and warm in summer (rarely above 100° F).2.Soils variable, sandy to rocky, mostly volcanic or limestone in Great Basin, mostly sandstone inCanyonlands.
3.
Valley bottoms mostly above 4000 ft (1220 m).4.Numerous, isolated mountain ranges (Great Basin) or volcanic peaks (Canyonlands), many more than10,000 ft (3000 m).
5.
Vistas are dynamic and variable, even spectacular in places. Home to numerous national parks andmonuments.
6.
Fire is only moderately significant; does aid in the re-establishment of grasses.7.Vegetation:
Sagebrush is the dominate shrub; small trees such as pinyon (Pinus monophylla [Great Basin] or P. edulis[Canyonlands]) and juniper (Juniperus osteosperma) are the co-dominants.
1.
Saltbush (Atriplex) occurs where alkaline and generally dry; pickleweed (Salicornia) and greasewood(Sarcobatus) where moist and alkaline are dominant shrubs.
2.
Mountain slopes with pine, spruce (Picea), fir (Abies) and aspen (Populus tremuloides) and many generaand species of often large shrubs (e.g., mountain mahogany [Cercocarpus]).
3.
Grasses more common in Canyonlands than Great Basin.4.
C.
Animals:Mammals include deer, some bear, bobcats, coyote, fox and jackrabbita.Raptors include eagles, hawks and falcons. Many species of resident birds.b.
D.
History:Great Basin (proper) is a hydrographic basin; water does not flow to the sea. Canyonlands drained byGreen and Colorado rivers.
1.
Pluvial lakes formed during Pleistocene Ice Age in Great Basin with the vegetation pinched between themontane ice and pluvial lakes; plants escaped south onto what is now Mojave Desert.
2.
Canyonland vegetation thwarted from escaping southward by elevationally higher North Rim of the GrandCanyon; narrow escape (and invasion) route via the Colorado River.
3.
Great Basin newly formed as a desert; Canyonland long a desert (last 24 million years)4.Whole area the home of numerous endemic species of plants and animals.5.
E.
Exploitation:Widespread and intense grazing from 1870-1920 destroyed much of the palatable vegetation for sheep andcattle; invasion of poisonous plants and annual European grasses means much still unusable.
1.
Mining and some "off-road-vehicle" (ORV) traffic causing problems in certain areas.2.
F.
Boojum near Parador Punta Prieta, Baja California
Warm Deserts
Three desert regions classified as warm deserts in western North America.Mojave Desert: Southeastern California across southern Nevada to extreme southwestern Utah and intonorthwestern Arizona; smallest of the North American deserts.
1.
Sonoran Desert: Coastal mountains in southwestern California (and the Pacific Ocean in Baja California)east to the Chihuahuan Desert of New Mexico (in the north) and the Sierra Madre Occidental of Mexico (inthe south). A portion California is often defined as the Colorado Desert.
2.
Chihuahuan Desert: Southeastern Arizona, southern New Mexico and western Texas southward to the trans-volcanic belt of San Luis Potosí in north-central Mexico.
3.
A.
Features:Mojave Desert
Low, mostly treeless mountain ranges and broad, open valley bottoms.a.Extremes in elevation (-282 ft below sea level; near by Panamint Peak is 11,049 ft or -86 m to 3270m) and temperatures (Death Valley recorded the hottest temperature in the United States at over 126°F).
b.
Precipitation mostly Dec through Mar; 2-5 in (5-12.5 cm) annually; results in winter annuals - plantsthat flower and fruit in about 8 weeks (see right).
c.
Summer convection storms mean local flash flooding and summer annuals.d.Great diversity of annual species resulting in numerous endemics.e.
1.
Sonoran DesertMountains mostly low (except Sierra Juarez and San Pedro Mártir in Baja California).a.Precipitation biseasonal: falls during Dec through Mar and Jul through Sep; mostly as rain, rarely assnow.
b.
Winter temperature average above freezing; summer temperatures above 100° F common.c.More than 200 days growing season.d.
2.
Chihuahuan DesertLow, scattered and isolated, mostly limestone, short mountain ranges.a.Warm to hot summer temperatures, cold and often freezing temperatures in the winter.b.Precipitation as cold rain or snow Dec to Mar; warm rains Jul through Sep.c.Warm spring and fall means growing season of 200 or more days a year.d.
3.
B.
Vegetation:The dominant shrub is creosote bush (Larrea divaricata).1.Low, sclerophyllous hardwoods more common in southern deserts as are cacti.2.Arborescent plants include palms and yucca species. Most bizarre plant is the boojum tree (Fouquieriacolumnaris), a columnar trunk with leaves and a few branches at the very top some 50-65 ft (15-20 m)above the ground.
3.
Many annual plants flower after sufficient winter rains.4.
C.
Animals:Some deer, wild sheep (at higher elevations in isolated mountains), coyotes, jackrabbits, and a multitude ofmice (including the packrat), lizard (including the large chuckwalla and horned lizards or "horny toads"), andsnakes (e.g., sidewinder, a rattlesnake that moves with only a small portion of its body actually touching theground). Wild pigs occur in the southern deserts.
1.
Numerous birds, many ground-dwellers (quail and the roadrunner); large raptors; resident song birds.2.Several endemic species (even genera) of fish and reptiles in isolated, small ponds.3.
D.
History:Mojave Desert largely occupied by cold desert through much of the Pleistocene, forming over the last12,000 years.
1.
Sonoran Desert has expanded its range northward over last 12,0002.Chihuahuan Desert largely a rich grassland until about 12,000 years ago, then gradually becoming a desert3.
E.
Exploitation:Extensive, long-term overgrazing has resulting in many introduced weeds, most notably the Old Worldtumbleweed (Salsola spp) now found throughout the West.
1.
Some mining and limited logging especially in mountains.2.Off-road vehicle (ORV) damage significantly altering portions of the warm deserts.3.
F.
Tropical forest near El Real, southern Panama
XII. Tropics
Location: Central America, Caribbean islands, equatorial South America and western Africa, southeastern Asiafrom India to Malaysia, northern Australia, and many Pacific Islands. Forests cover about seven percent of theearth's surface, half of that is tropical. Restricted to southern Florida in the continental United States.
A.
Features:Vast number of densely spaced trees and enormous diversity of species.1.General lack of seasonality.2.Precipitation about 80-160 in (200-400 cm) or more in North America3.Mean average temperature is 70-80° F (22-27° C) for most of the region.4.Frost and freezing temperatures restricted to tropical mountains.5.High humidity, narrow temperature fluctuation, uniform day-length; growing season up to 365 days a year.6.Soils are geologically old and therefore generally poor in mineral nutrients.7.Fires common during dry season, mostly slow burning and not hot.8.
B.
Vegetation:Multiple layers in the canopy; significant biomass.1.Lianas (woody vines) and epiphytes (plants that live on other plants) are common, many can be parasitic orsemi-parasitic.
2.
Usually large smooth leaves with drip points to prevent water from accumulating on the blade.3.Extreme diverse array of species in small area4.
C.
Animals:Numerous species of mammals of diversity types: monkey, tapir, panther, sloth, etc.1.Many unique kinds of birds (e.g., parrots), home of numerous migratory song birds and water fowl.2.Incredible numbers of insects; a single tree can harbor some 30,000 different species.3.
D.
History:Much of the tropics in place over last million years although size variable due to changes in sea level.1.Rates of speciation high with limited selection pressure (unlike arid areas) so that numerous, distinct buthardly distinguishable species exist to increase diversity.
2.
E.
Exploitation:Cutting of forest to create large expanses of grazing land rapidly depleting tropical forests resulting in soildepletion, erosion and changes in local climates. It is estimated that approximate 80 acres a minute of rainforest are disappearing, roughly an area the size of the state of Colorado yearly.
1.
Mining and logging (for lumber and pulp) resulting in forest destruction and pollution, silting, and otherwater problems.
2.
Introduction of exotic species often resulting in loss of native species. It is estimated that nearly 50 speciesgo extinct each day in the tropics, largely due to human pressures.
3.
F.
Major subcommunities of Lowland Tropical Regions:Rain Forests: Plains or low mountain ranges in tropical regions of the world, almost always at lowelevations. Prolonged drought is rare or non-existence, and cold temperature do not occur. Complex foreststructure. Numerous species with epiphytes and lianas common.
1.
Evergreen Seasonal Forests: Dry season less than three months; precipitation (about 65 in or 180 cm), dryseason mostly less than 4 in (10 cm). Large scattered trees, epiphytes and lianas still common.
2.
Deciduous Seasonal Forests: Dry season about five months, two months when rainfall does not exceed 1 in(2.5 cm). Trees and shrubs in two distinct strata; trees nearly always deciduous and the shrubs evergreen.Lianas and epiphytes are rare.
3.
Tropical Savannas: Large open areas of tropical graminoids and scattered low trees and shrubs. Formed bycombination of dry, nutrient poor soils with possibly some influences by climate and human activities, thelatter two not well understood. Probably maintained by grazing animals (to Early Holocene) and fire.Savannas in Central America and parts of South America, more common in Africa. Considerable diversityand threat.
4.
G.
Major subcommunities of Montane Tropical Regions:Low Montane Rain Forest: Similar to rain forests but with better soil drainage only trees not as tall. Mostlybelow 800 ft (250 m) elevation. Epiphytes and lianas common.
1.
Montane Rain Forest: Mid-elevation. Humidity and increased amount precipitation augmented by fog orcloud. Cooler temperatures. Trees shorter, mostly less than 65 ft (20 m), with few lianas and epiphytes.Sub-canopy composed of small shrubs. In most of South and Central America the trees belong to a largenumber of plant families, but in Mexico, oak (Quercus) and pine (Pinus) more common.
2.
High Montane Forest. Lower precipitation. Frost can occur, freezing temperatures on volcanic peaks inMexico and Central America and the upper reaches of the Sierra Madre Occidental and Sierra MadreOriental. Common trees include pines and firs (Abies) along with oak. Large shrubs include scrubby alder(Alnus) and maple (Acer). Understory much more tropical.
3.
Elfin Woodlands: Highest elevations of many tropical mountain ranges. Temperatures are cool but notfreezing. The is a constant cloud cover rather than periodic fogs. High humidity is common. Stunted trees,often gnarled and twisted, with heavy branches due to the occasional strong winds; covered with a multitudeof bryophytes and ferns along with numerous flowering epiphytes.
4.
Pármo: High mountain peaks in Central America and Caribbean Islands, common on the Andes of SouthAmerica. Cool temperatures, frost common. Can be at low elevations in North America and probablyformed by strong on-shore winds. Defined by a timberline in South America. Dominated by graminoids,some grasses but sedges (Cyperaceae) and pipeworts (Eriocaulaceae). Columnar, arborescent perennialsbelonging to sunflower family and lobelia portion of the bellflower family (Campanulaceae) common in theAndes.
5.
Alpine tundra: Top of volcanic peaks in Latin America and in the Andes. Freezing temperatures possibleevery month. Dominated by graminoids. Limited diversity.
6.
H.
Other sites of interestBiomes of the world: Excellent summaryBiogeography of North America by Jonathan AdamCritical ecoregions from the Sierra ClubLand Use History of North America: A major review, see in particular the report on the land-use history ofthe Baltimore-Washington area by Timothy ForesmanBaltimore Ecosystem StudyAlaska EcoregionsDesert USA: Excellent linksLiving EarthPrairie Restoration LinksDescription of the Ecoregions of the United States by Robert G. BaileyEcological Subregions of the United States by W. Henry McNab & Peter E. Avers"Effects of climate change on biological diversity in western North America: Losses and Mechanisms" byD.D. Murphy & S.B. Weiss (1992): Technical but most informativeEndangered Ecosystems of the United States: A Preliminary Assessment of Loss and Degradation: Atechnical report by Reed F. Noss, Edward T. LaRoe III & J. Michael ScottDesert Ecosystems Resource PageRainforest Action NetworkConservation and Planetary Survival: An essayExpanded PBIO 100 biome notes - extensive discussion and pictures of each biome- particularly good fordeserts
Back to BSCI 124 main page
Last revised: 19 Nov 2001 - Reveal
ZOO 2010 LECTURE NOTES
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ZOO 2010 FRED SEARCY, JR.
LECTURE NOTES I. AQUATIC ENVIRONMENTS
Approximately 71% of Earth’s surface is covered by
ocean. This area is termed the hydrosphere (hudor =
water, Gk.). The average depth of the ocean is 3.8 km
(2.5 m), and the ocean floor varies in thickness from 5
to 10 km.
The lithosphere (lithos = stone, Gk.) is the rocky
portion of Earth’s surface. The atmosphere (atmos =
vapor, Gk.) surrounds the lithosphere and the
hydrosphere.
Life can be found in the lower atmosphere, upper
lithosphere, and the hydrosphere. This 20-mile-deep
area, habitable by living organisms, is called the
biosphere.
The most stable of all of these environments is the hydrosphere. Organisms in an aquatic
environment are protected from extremes in temperature, physiological conditions, and size
restrictions of the organisms. For this reason, we will begin our study of zoology by looking at
aquatic environments. The first is the marine environment.
A. Marine
The marine environment is an aquatic environment with salt water of varying salinities. We
properly think of marine environments in terms of ocean, seas, gulfs, bays, and straights.
There are seven major subdivisions of the ocean:
1. Arctic 3. North Pacific 5. North Atlantic 7. Indian
2. Antarctic 4. South Pacific 6. South Atlantic
The salinity of marine environments varies due to the influx of fresh water. Thus, seas
bounded by land have low salinities if rivers flow into them, and high salinities if no fresh water
feeds them. The average sea water salinity is 33 parts per thousand of dissolved salts, mostly
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sodium chloride, or 3.3%.
The marine environment can be broken down into zones.
Notice that most of these zones are based somewhat loosely on depth or the presence or
absence of sunlight. The depth to which sunlight penetrates is a critical factor in determining
what type of marine life may be found. Life in oceans is regulated by food chains. Life is
divided into two categories of organisms: (1) producers, and (2) consumers.
MARINE ZONES
Littoral Zone: The littoral zone encompasses that area off shore to a depth of 5 to 10 meters. It
experiences tides and wave actions churning up the bottom. It therefore has high dissolved oxygen,
sunlight penetrates all areas, and it has abundant nutrients due to runoff from the shore. The species’
diversity is great.
Neritic Zone: This is a zone that is often equated with the continental shelf. Sunlight penetrates this
zone, and it is rich in nutrients due to proximity to land. There is no definite demarcation from littoral to
neritic.
Bathyal Zone: This zone extends from the edge of the continental shelf to a depth where water
temperature is 4 degrees Celsius. Little sunlight penetrates this area, and no photosynthesis is the
rule.
Abyssal Zone: This zone is usually at a depth of 2000 to 6000 m. It has extremely uniform
environmental conditions, no sunlight, and thus no photosynthesis. It is the graveyard of suspended or
free-floating organisms once they die. It is therefore rich in silicas, phosphorous, and nitrogen. Fauna
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is sparse.
Hadal Zone: This zone is found at a depth greater than 6000 m. Light is totally absent. Pressures
range from about 600 to 1100 atms. Environment is quite uniform.
Producers synthesize new organic matter from inorganic material. Most producers are plants,
and the synthetic process is photosynthesis.
Consumers are organisms that feed on plants or each other to satisfy nutritional needs.
Producers are thus autotrophic, and consumers are heterotrophic.
The ultimate source of food in a marine environment is microscopic unicellular and
multicellular organisms called plankton. Plankton is divided into two categories:
(1) phytoplankton, and (2) zooplankton.
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Phytoplankton is microscopic plant life, and it is phytoplankton that is the producer of
marine environments.
Zooplankton is microscopic animal life, and they consume phytoplankton and each
other for nutrients.
Other forms of animal life that are microscopic feed on plankton.
A Typical Food Chain
→ → → → → phytoplankton → → → → → producers bacteria ↓ decompose eaten by zooplankton whales ↓ copepods, seals shrimp, etc. → → → → → → → fish → → → → → →
1000 pounds of phytoplankton will feed 100 pounds of zooplankton, and 100 pounds
of zooplankton will feed 10 pounds of fish.
It should be obvious from this that phytoplankton is the cornerstone of the food chain.
Phytoplankton is dependent on sunlight for photosynthesis. Wherever phytoplankton
is abundant, life is abundant; therefore, we may also break the marine environment
down into zones based on how deeply sunlight penetrates water.
In most marine
environments, sunlight
that will permit
photosynthesis will
penetrate only to a depth
of 80 m. This is called
the Euphotic Zone. In
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this zone, you find pelagic organisms.
These are free swimming or suspended in this zone.
From a depth of 80-200 m, you have a zone that sunlight will penetrate but which is
not sufficient for photosynthesis. This is called the Disphotic Zone. Pelagic
organisms are of the free-swimming kind. However, they will feed mostly in the
Euphotic Zone.
Below a depth of 200 m, no sunlight penetrates. No photosynthesis occurs here, and
any pelagic organisms find feed in the upper two zones or feed on benthic organisms
or bottom dwellers.
B. Fresh Water
Freshwater environments contain little concentrations of salt. With certain exceptions
(such as salmon), freshwater organisms would die once exposed to marine
environments. Organisms not tolerant of varying salinities are termed stenohaline
(stenos = narrow, Gk.; halite = salt, L.). Organisms capable of surviving varying
salinities are referred to as euryhaline (euru = wide, Gk.). Examples of euryhaline
animals include the salmon, eels, sharks, puffer fish, flounder, etc.
The critical factor is the water regulatory mechanism an animal uses in dealing with
euryhaline conditions. Marine organisms, especially marine invertebrates, are
isotonic with regard to their environment. Freshwater animals are in a hypotonic
environment. They are faced with retaining salt and pumping out excess water. To
balance this, they must be able to carry out osmoregulation. This usually involves
excretory organs or special secretory cells.
Those organisms that are euryhalines must also use osmoregulation to balance salt
and water flow. An example is the shore crab (Carcinus) that lives in both sea and
brackish water. In sea water, the crab is in an isotonic environment, but brackish
water is hypotonic to it. To maintain salt balance, cells on the crab’s gills remove salt
from the water and secrete it into the blood.
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Marine vertebrates as bony fishes have a reverse problem. They lose water to the
environment and are in constant danger of dehydration. To maintain water balance,
they constantly drink water and excrete salt through specialized cells in the gills.
Thus, freshwater fish don’t drink water, but saltwater fish must.
We will discuss various means of osmoregulation throughout the remainder of the
course.
II.FRESHWATER ENVIRONMENTS
Freshwater environments can be divided into zones:
A. Littoral Zone. From the shore to the influence
of waves and spray, to a depth where light is
sufficient for photosynthesis.
B. Sublittoral Zone. The deepest area of plant
growth.
C. Profundal Zone. Area of no plant growth.
Some lakes are so shallow as to not have aphotic regions and thus no sublittoral or
profundal zones.
A more interesting zonation occurs due to temperature variation. Oceans are fairly stable
as far as temperature, but rivers, lakes, and streams may undergo rapid changes in
temperature. There may be thermal stratification in fresh water. You know that in
summer, the warmer water is found near the surface, and colder water is just below the
surface. The lake is stratified or layered due to temperature. There are 3 vertical zones
of stratification.
A. Epilimnion Zone. (epi = on, over, upon, Gk.; limne = pool or lake, Gk.) is the
warmer, upper region of a lake.
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B. Metalimnion Zone. (meta = between, Gk.) is the middle portion where temperature
change with depth is greatest (the thermocline).
C. Hypolimnion Zone. (hypo = under or beneath, Gk.) is the deepest part of the lake.
This distribution of water is based on density at various temperatures.
The density of water is based on several factors: among the most important are
temperature and the particles dissolved in water. As an example, pure water has its
greatest density at 4ºC. Water in the solid form--ice--actually is less dense than water.
This property means that warm water is less dense than cold water.
In the winter, when water freezes, it is less dense and ice forms at the top of a lake.
Water at the bottom of a lake is at 4ºC. As water is warmed, it rises. As it is cooled, it
sinks. This sets up convection currents in the lake. The area of greatest change is the
thermocline.
Not only that, but the warmer the water is, the less gas (such as oxygen) is formed in the
water. That’s why fish seek deep water in lakes in the summer. The deeper the water,
the cooler it is, and more oxygen is present. On unusually hot days, shallow lakes lose
most of their oxygen, which can result in fish kills.
III. ESTUARIES
These are areas where salt water and fresh water meet. They have highly variable
salinities due to discharge of fresh water and the tide action.
IV. TERRESTRIAL ENVIRONMENTS
A. Biomes
Biomes are terrestrial and climatically controlled ecosystems characterized by
distinctive vegetation. In every biome there is an exchange of water, nutrients, gases
and biological components, including people. Depending on the source, there may be
