community ecology virginia forest
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Community Ecology
The Community as an Ecological UnitCommunity Development
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Plant Communities
Communitiesare composed of populations of
many species living together in the same
location at the same time.
Similar communities tend to occur under similarenvironmental conditions.
Associationshave a consistent species composition and
habitat
But, composition can vary considerably from one
location to another.
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Examples of Communities
Chesapeake Bay
shallow water
community
Bog
Piedmont forest
Salt marsh
Alpine community
Dune community
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Some Characteristics of Plant Communities
1. Architecture (for example forest layers)2. Species composition (native , invasive)
3. Species diversity
4. Nutrient cycling (demand, storage capacity)
5. Development over time (succession)
6. Productivity (Biomass)
7. Microenvironments
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Plant Communities:
The Piedmont Forest
1. Part of the temperate deciduous biome
a. Precipitation relatively high
b. Soils rich in organic matterc. Broad-leaf trees that lose their leaves seasonally
dominate
2. The piedmont is defined as the plateau
between the coastal plain and theAppalachian mountains.
The foothills of the Appalachian Mountains
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1. Coastal Plain
2. Piedmont Province
a. Upland
b. Lowland
3. Ridge/Valley Province:Middle
4. Appalachian PlateauProvince:
Allegheny Mountain section
Maryland Biogeography
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The Piedmont Forest
How old is the Piedmont region? Underlying geology dates billions of years old.
Granite, gneiss, mica-schist, gabbro, marble, and serpentine
Soil types: Loams and clay Loamy: contains sand, silt, and clay
Holds water, but also drains well Good aeration
Clay: packs tightly, little water retention, little aeration
Land-use history Deforestation beginning in the colonial period
Primarily agricultural until the late 20thcentury
Chestnut-Oak forests until 1930s chestnut blight
Oak-Pine or Oak-Hickory forests
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Layers of the Forest
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Layers of the Forest
1. Canopy
2. Understory
5. Forest Floor
4. Herbaceous plants
3.Shrubs
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The Forest Community
The Canopy the leafy crowns of the trees
most of the forests food is made here(photosynthesis)
feeding ground for many animals
just below the surface of the upper most layer of leaves
leaf eaters: beetles, bugs and caterpillars, leaf hoppers,aphids etc.
Song birds and predatory insects (spiders) feed on theinsects
Squirrels (eastern gray squirrel)
protection for the forest below
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Canopy Trees of the
Piedmont Forest Several
species of Oak
BitternutHickory
Buckeye
Red Maple
Beech
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The Understory
Smaller trees make up theunderstory
Young trees (same species ascanopy trees)
Low-growing trees(dogwoods)
Many birds and animalsspend most of their lives inthe understory.
Good for nesting, protectionfrom hawks, owls, andstormy weather
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Understory Trees of the
Piedmont Forest
Dogwood
Redbud
Paw-Paw
Service Berry
Musclewood
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Shrub Community
Shrubs are woody plants with many stems A characteristic canopy will harbor a characteristic
shrub community
Oak-Hickory forest
Spicebush Blueberry
Witchhazel
Huckleberry (Dangle berry)
Rarely greater than 7 feet in height
Effect of a closed forest canopy/ open forestcanopy on the shrub community
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Spicebush
Blueberry
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Shrub Community
Protective cover for smallmammals
shrews
mice chipmunks
Nesting sites for Robins (inshrubs)
Berries and seeds for manymammals and birds
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Herbaceous Layer
Emerges during the spring before the canopy isfully leafed-out
Ferns and mosses
Lichens
Wild flowers Spring Beauties
Violets
Orchids
Lilies
The herbaceous layer dies out by mid-summer,existing underground as bulbs & rhizomes
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Spring BeautyClaytonia virginica
Northern VioletViola sp.
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Lichens and
Mosses
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Forest Floor
The wastebasket for all thelayers of the forest above
leaves, petals, fruits, seeds,
twigs, limbs, whole tree trunks,feathers, fur, feces, animal
carcasses
estimated 2000-3000 lbs/acrein the fall
in various stages of decay
Yellow coral mushroom
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a handful of dirt viewed with amagnifying glass reveals
earthworms, other nematodes
mites, spiders, black ants, and manyother insects
many more organisms are
microscopic The plants and animals on one acre
may out number the entire humanpopulation by 106to one!
Decomposers of the forestecosystem break down the organicmatter and release inorganic matter(Nitrogen, O2, etc)
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Measuring Diversity in
Plant Communities
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Levels of Biodiversity
1. Genetic diversity: the gene pool within a
population
2. Species diversity: the number and types of
species in an area
3. Higher taxonomic diversity (Families,
Genera)
4. Community Diversity
5. Ecosystem diversity (Habitat diversity)
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Species diversity
has two components:
1. Species richness:how many different species
are present in a habitat2. Species abundance:total number of
individuals of each species present. Usually
expressed as %
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Defining Biodiversity:
Old growth forest in the Shenandoah Mountainsof Virginia
50,000 trees represented by 10 species.
Managed forest, recently clear cut
45,000 trees are maple and birch
Only 1/10thof the forest is represented by theremaining 8 species
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Species diversityhas two
components:1. Species richness:how
many different species
are present in a habitat
2. Relative abundance:total
number of individuals of
each species present
3. Which area is morediverse?
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Defined as the transition in speciescomposition over ecological time
Plants and animals appear and graduallyalter their environment as they carry ontheir normal activities.
The accumulation of waste, dead organic
matter, and abiotic factors such as light andwater availability further alters thecommunity.
Community Development:
Ecological succession
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1. Primary succession
Occurs in an area not previously inhabited
Areas that have been completely devastatedby disturbance
2. Secondary succession
Occurs where there is a pre-existingcommunity and well-formed soil
Community Development:
Ecological succession
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Mount St. Helens Eruption in 1980
Five explosive eruptions of Mount St Helens
in 1980 sent pumice and ash 6-10 miles into
the air.
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The Aftermath of Mount St. Helens Eruption
These trees were blown down by a lateral blast. This
is an example of where the process of primary
succession will begin to bring new life
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Primary Succession
Occurs on essentiallylifeless terrain
Volcanic eruptions
Retreat of glaciers
May take hundreds to
thousands of years
The first group oforganisms to appear
1. Autotrophic bacteria
2. Lichens
3. Mosses (organisms thatreproduce by spores)
4. Grasses, ferns, shrubs,pine trees
Lichens are a symbioticrelationship between Algae and
Fungi. They secrete acid thatturns rock into soil. Once thesoil is established, plants cancolonize
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Primary Succession
Iceland is a new country emergingfrom both the recent ice age andfrequent volcanic eruptions
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Primary
Succession in
Ponds and Lakes In the Northern US,
many ponds and lakes
are were left behind
by the receding
glaciers (10,000ybp)
Many ponds become
bogs.
have no streams
drainage, so they arefilled by precipitation
Grow smaller every
year because of
succession
Bogs
Algae carried in by birds andthe wind
They die and fall to the bottom
contributing to the organicmatter.
Duckweeds form at the edges
When nutrients, oxygen, pH,and temperatures are low
Peat mosses take over,forming a thick mat.
Woody shrubs and carnivorousplants grow on this substrate
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Bogs are an example of
Primary Succession
Peat moss
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Duckweeds occur early in succession
Under less acidic
conditions, duckweeds
are one of the 1stplants to
grow
Grass-like sedges become
established and form a
mat
Once a mat is formed,bushes, shrubs and trees
become established
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Secondary Succession Existing community has
been disturbed Soil is intact
Abandoned Agriculturalfields:
Old field succession Climax community can
become established afteronly decades
Disturbance colonizers:
weedy plant species1. a high reproductive rate,
2. good at dispersal
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1styear
Horseweed
Crabgrass
pigweed
2ndyear
Asters
Crab grass
3rd-18thyear
Young
Pine forest
19th
-30th
yearMature pine
Forest
Understory of
Young hardwoods
70th-100th
Pine to
Hardwood
transition
100thyear plusClimax
Oak-hickory
forest
Old Field Succession
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Disturbance1. Disturbance is a
natural part of thelife of a community:
2. Most communitiesare always inrecovery from
disturbance3. Humans, too, areagents ofdisturbance
TsunamisHurricanes
Storms
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The Nature of Disturbance
1. Damage communities2. Alter the resources available to organisms
Disrupt the food chain
3. Removing organisms!!
4. Opportunity for secondary succession torebuild community
5. Examples of Disturbancea. Storms, Hurricanes, Tsunamis
b. Ice storms
c. Flooding
d. Tornados
e. Fire
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Fire EcologyYellowstone fires of 1988
Fire is being used to manage marshes and forests
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