BIOL 4120: Principles of Ecology
Lecture 5: Biome Concept in
Ecology
Dafeng Hui
Room: Harned Hall 320
Phone: 963-5777
Email: dhui@tnstate.edu

5.1 Climate is the major determinant of plant growth form and distribution
5.2 Climate determine the boundaries of terrestrial biomes
5.3 Walter climate diagrams distinguish the major climate biomes
5.4 Temperate climate zones have average annual temperature between 5 and 20oC
5. 5 Boreal and polar climate zones have average temperatures below 5oC
5. 6 Climate zones with tropical latitudes have average temperatures exceeding 20oC
5.7 Biome concept must be modified for freshwater aquatic systems
5.8 Marine aquatic systems are classified principally by water depth

Concept of Biomes:
F.E. Clements and V.E. Shelford, 1939
Combining broad-scale distribution of both plants and associated animals into a single classification
Biomes: classified according to the predominant plant types
Campbell 1996: the world's major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment.

Three general plant forms: trees, shrubs, and grasses.
Why are there consistent patterns in the distribution and abundance of three dominant plant life forms that relate to climate and physical environment?

These three forms represent different patterns of carbon allocation and morphology
Grasses: less C to production of supporting tissue (stem) than do wood plants (shrubs and trees), more to photosynthetic tissues (leaves)
Woody plants: shrubs allocate lower percentage to stem than trees.
Trees: more to stem, advantage of height and access to light, cost more for maintenance and respiration.
As environmental conditions become adverse for photosynthesis (dry, low nutrient, cold T), trees will decline in both stature and density until they are no longer able to persist as a component of the plant community.

Within broad classes of forest and woodland ecosystem (trees are dominant or co-dominant), leaf form is another plant characteristic.
Based on longevity of leaf
Deciduous (live for only one year or growing season)
• Winter-deciduous (temperate regions, low winter T)
• Drought-deciduous (subtropical and tropical, leaf shed on dry periods)
Evergreen (live beyond a year)
• Broadleaf-evergreen (tropic rainforest, no distinct growing season, year-round photosynthesis)
• Needle-leaf evergreen (growing season is short or nutrient availability constrains photosynthesis and plant growth)
Economic model to explain adaptation of leaf form: cost to produce leaf and gain from photosynthesis.

Concept of Biomes:
Major terrestrial biome types (eight , nine, and varies):
Tropical forest, temperate forest, conifer forest
(taiga and boreal forest), tropical savanna, temperate grasslands, chaparral (shrublands), tundra, and desert.

Since organisms are adapted to the physical environments of their biomes, ranges of species are limited by these physical conditions
In terrestrial environments, temperature and moisture are the most important variables, particularly for plants.

Related species may differ in their ecological tolerances, and distribute Differently

5.2 Climate defines the boundaries of terrestrial biomes
(Walter)

Robert Whittaker,
Cornell Uni.
Biomes and climate
Boundaries between biomes are broad and often indistinct
Other factors: topography, soils, and exposure to disturbances such as fire

Mean temperature: 14.9 oC, annual precipitation: 122.3 cm
Source: US Climate Data
Temperate seasonal forest

Robert Whittaker,
Cornell Uni.
Biomes and climate
Boundaries between biomes are broad and often indistinct
Other factors: topography, soils, and exposure to disturbances such as fire

BIOL 4120: Principles of Ecology
Lecture 5: Biome Concept in
Ecology
Dafeng Hui
Room: Harned Hall 320
Phone: 963-5777
Email: dhui@tnstate.edu

Climate and soil
Soil profile, soil weathering process, soil order
Biomes
Climate is the major determinant of plant growth form and distribution
Climate determine the boundaries of terrestrial biomes

5.3 Walter climate diagrams distinguish the major terrestrial biomes
Precipitation and temperature interactively determine biomes
To permit ecologically meaningful comparisons of climates between localities,
Walter developed a climate diagram to illustrate seasonal periods of water deficit and abundance.

Each climate zone has a typical seasonal patterns of T and P.

5.4 Temperate climate zones have average annual temperature between 5 and 20 o C
Temperate seasonal forest biome (Climate zone VI)
Temperate rain forest biome (Climate zone V)
Temperate grassland/desert biome (Climate zone VII)
Woodland/shrubland biome (climate zone IV)
Subtropical desert biome (climate zone III)

Forest ecosystems dominate the wetter regions of the temperate zone
Deciduous forest covered large area of Europe and
China, but mostly converted to croplands, only exist in eastern China
North America, deciduous forests consist of a number of associations (next slide)
Southern Hemisphere, temperate evergreen forest become predominant
Asiatic broadleaf forest found in eastern China,
Japan, Korea is similar to the North American deciduous forest

Large scale distribution of temperate forest in eastern US

Rainfall is very important: 250 to 800 mm
Other factors: fire, and human activity
(convert grassland to desert by overgrazing)
Area: dropped from 42% to <12% of original size
Location: mid-latitudes in mid-continental regions
Typical: prairies of North America, steppes of central Eurasia

Tallgrass prairie
Big bluestem,
>1m
Mixed-grass prairie
Needlegrassgarma grass
Shortgrass prairie
Blue garma and buffalo grass
Grassland in
North
America a. Tallgrass prairie in
Iowa, b. mixedgrass prairie; c. shortgrass steppe

Aboveground primary productivity is related to MAP (52 grassland)
Grasslands are most productive when MAP>800 mm and MAT > 15oC

5.4 Temperate climate zones have average annual temperature between 5 and 20 o C
Temperate seasonal forest biome (Climate zone VI)
Temperate rain forest biome (Climate zone V)
Temperate grassland/desert biome (Climate zone VII)
Woodland/shrubland biome (climate zone IV)
Subtropical desert biome (climate zone III)

sclerophyllous: hard-leaved vegetation

Area: 25 to 35%
Location: latitudes between 15 and 30o
Cause: Global air mass circulation
T: High in summer, could be cold in winter
PPT: low, <150 mm
Typical examples: majority in Northern
Hemisphere, Sahara in Africa, Gobi in
Asia, western North America

Deserts are not the same everywhere
Cold desert: Great Basin of North America, the Gobi, Takla Makan, and
Turkestan deserts of Asia
Species: sagebrush, shadscale, chenopods, etc
Hot desert: Mojave, the Sonoran, and Chihuahuan
Vegetation: none to some combination of chenopods, dwarf-shrubs, and succulents

Hot desert: a. Chihuahuan
Desert, b. Great Victorian
Desert in Australia, c. Dunes in Saudi Arabian desert.

Survive of desert plants:
Adapted to scarcity of water, low primary productivity
Flowering only when moisture is present
Fast grow, flower, produce seeds and die
Deep-rooted (mesquite, taproots reach water table)
CAM pathway, special leaf structure
Survive of animals
Support a diversity of animal life (bettles, ants, locusts, lizards, snakes, birds and mammals)
Grazing herbivores: generalists, consume a wide range of species.
Desert carnivores, such as fox and coyotes, have mixed diet include leaves and fruits.

5. 5 Boreal and polar climate zones have average temperatures below 5 o C
Boreal forest biome (Climate zone VIII)
Tundra biome (Climate zone IX)

Black spruce in North America taiga (boreal forest)
Some coniferous forest. A. Norway spruce, b.
Rocky Mountaine subalpine forest, c. montane coniferous forest in Rocky Mountains

Tundra is treeless plain
Arctic tundra is a frozen plain, clothed in sedges, heaths, and willows, dotted with lakes, and crossed by streams
Cold Temperature and low precipitation
Two types:
Polar desert: dry soil, less than 5% plant cover
Wet tundra: up to 100% plant coverage, wet to moist soil
Unique conditions: permafrost: isolate and protect soil OM vegetation: simple form, slow growth, allocate more to roots.

Arctic tundra
Canada

Rocky
Mountains alpine tundra

5. 6 Climate zones with tropical latitudes have average temperatures exceeding 20 o C
Tropical rain forest biomes (Climate zone I)
Tropical seasonal forest/savanna biome
(Climate zone II)

Location: Equatorial zone between latitudes 10 oN and 10 oS
T: warm all year, monthly mean T>20 oC
PPT: Rainfall occurs daily, min. monthly>60mm
Typical example: Amazon basin of
South America

Climate zone with temperate climate zones have average temperatures between 5 and 20 oC
Boreal and polar climate zones have average temperatures below 5oC
Climate zones with tropical latitudes have average temperatures exceeding 20oC

Tropic rain forests in
Amazon (a), Malaysia (b), and Northeast Australia (c)
High net primary productivity (NPP)
High diversity of plant and animal life
7% land surface, >50% plant and animal species
10-km2 contain 1500 species of flowing plants and 750 tree species.
Richest area in Malaysia,
7900 species

90% of all primate species live in the tropical rain forest orangutan (an arboreal ape)
Gibbons, langurs, macaques
(Malaysian)
Gorillas, and chimpanzees
(Africa)
Lemurs
Beetles, butterflies

Vertical stratification of a tropic rain forest

Location: Equatorial zone between latitudes 30oN and 30oS, Dry tropic and subtropical.
T: warm all year, annual mean
T>18oC
PPT: distinct seasonality in rainfall, large interannual variation
Typical example: South America

Savanna: means the treeless areas of South America
Grassland with scattered trees.
Characteristics:
Occur on land surfaces of little relief, often on old plateaus, dissected by rivers, soil poor in nutrients, especially P
Dominant species are fire-adapted, subjected to recurrent fires.
Grass cover with or without wood vegetation is always present
Woody component is short-lived (less than a few decades).
Two-layer vertical structure (ground level grass + shrubs or trees)
Support a large and varies assemblage of herbivores, invertebrate and vertebrate, grazing and browsing.

Interaction between annual PPT and soil texture in defining biomes
Access by plants to soil moisture is more limited on the heavy textured soils (clay) than sandy oil.

Terrestrial biomes: classified by growth form of dominant vegetation reflects climate conditions.
Aquatic biomes: in many aquatic systems, there is no “vegetation” form, only algae
Classified primarily by physical characteristics such as salinity, water movement, and depth
Freshwater aquatic:

Flowing water: Streams and rivers



Standing water: lakes and ponds
Wetlands
Estuaries

Flowing water: streams and rivers
Lotic systems: flowing fresh waters, such as streams and rivers
Lack richness and diversity
Streams form wherever P exceeds ET, and excess water drains from the land.
Riffles: water runs rapidly over a rocky substratum
Pools: deeper stretches of more slowly moving water
Riparian zone: terrestrial veg influenced by seasonal flooding
Allochthonous: organic material that enters the aquatic system from the outside
Autochthonous: home grow its organic material.

Fluvial systems, as rivers are sometimes called

Standing water: lakes and ponds
Layers of lake:
Littoral zone
Liminetic or pelagic zone
Benthic zone
Lentic system: nonflowing water systems, such as lakes and ponds

Wetlands
Wetlands: terrestrial and aquatic communities come together
Lands consisting soil saturated with water and supports vegetation that specifically adapted.
Include swamps, marshes, bogs (fresh water), salt marshes and mangrove (associated with marine environments)
Plants can tolerate low O2
Important habits for a wide variety of animals, waterfowl, fish, invertebrates
Protect coastal areas from ravages of hurricanes
Wetland sediments immobilize potentially toxic or polluting substances dissolved in water and are thus natural water purifying plants.

Estuaries
Estuaries are found at the mouths of river
Mix of fresh and salt water
Extremely productivity systems

Human inputs into freshwater biomes
Acid rain and eutrophication
1. Acid rain: combustion of fossil fuels, sulfur dioxide, nitrogen oxides pH<4 in steams and rivers
2. Eutrophication: addition of limiting nutrients, such as N, P to aquatic ecosystems.
runoff: sewage, industrial wastes, fertilizers, animal wastes from agricultural lands.
Oxygen depletion

Variation in marine environments: temperature, salinity, depth (which influence light and pressure), currents, substrata and at the edges of ocean and tides.
Depth:
Littoral zone (intertide zone): extends between highest and lowest tidal water levels.
Neritic zone: extends to depth of 200m, high productivity.
Oceanic zone: below neritic, sparse nutrient, low production.

Benthic zone
Seafloor below oceanic zone.
Photic zone:
With sufficient light for photosynthesis
Aphotic zone: no light for photosynthesis

Open ocean === desert
But in:
Coral reefs: shallow water of warm ocean, T>20oC year around very productive and high diverse
Like tropical rain forest in terrestrial biome
Problem: global warming, coral bleaching

Winter-deciduous
Drought-deciduous

Broadleaf evergreen in tropic rain forest in
Australia
Needle-leaf evergreen in
Sierra Nevada, US

BIOL 4120: Principles of Ecology
Lecture 5: Biome Concept in
Ecology
Dafeng Hui
Room: Harned Hall 320
Phone: 963-5777
Email: dhui@tnstate.edu

Biomes, concept
Climate is the major determinant of plant growth form and distribution
Climate determine the boundaries of terrestrial biomes
Walter climate diagrams distinguish the major climate biomes
Temperate climate zones have average annual temperature between 5 and 20oC