Transcript Weeds and Exotics - Powerpoint for May 22.

Weeds and Exotics
Dandelion
What is a weed?
• a plant in the wrong place
• a plant out of place
• a plant whose virtues are yet to be
discovered
• one person’s weed is another person’s
herbarium specimen
What is an exotic?
• Exotic or alien species are species that are
not native the area in question – i.e. an
exotic in Illinois would be a species that did
not occur here naturally and was somehow
introduced to Illinois by human activity
Norway maple and orchard grass –
exotic in Illinois, native to Eurasia
Black locust and osage-orange – exotic
in Illinois, native to North America
Exotic Species
• Conservation biologists typically call
introduced species “exotic species” species which live outside their natural
range
• Botanists typically refer to exotic plants as
alien species
• Other terms you may see include biological
invaders, introduced species, invasive
species, non-indigenous species, non-native
species (my preferred term)
What is a weed?
• In general, we consider weeds to be exotic
or alien plants which have somehow
become problem plants –
• Problem plants typically have the following
two characteristics –
• 1) the plant has achieved a threshold level
of abundance, and
• 2) someone is concerned about the plant
Perspectives on Weeds
• There appear to be three dominant
perspectives on weeds: agriculturalranching, suburban, and ecological.
Agricultural-Ranching Perspective
• The agricultural perspective considers any
plant a weed if it competes with crops for
the available nutrients and moisture in a
field. Such plants can lower crop yield or
cause crop failure.
• The ranching perspective considers any
plant a weed if it presents a threat to
livestock or reduces the quality of forage
that is otherwise available.
Suburban Perspective
• The suburban perspective considers any
plant a weed if it invades the lawns and
gardens of suburban homeowners and other
managed landscapes of mainstream society,
which includes the lawns and gardens of
banks, schools, churches, malls,
government buildings, industrial parks, etc.
Suburban Perspective
The ideal plant of the managed landscape in suburbia
has the following characteristics:
1) It is often an introduced species that is poorly
adapted to the surrounding environment.
2) It is a sterile hybrid or patented cultivar.
3) It is difficult to maintain and often short-lived.
4) It doesn't spread readily to places where it
doesn't belong.
5) It has obvious aesthetic or culinary properties.
6) It has to be purchased at a store or through a
catalog (although heirloom plants may be passed
from one gardener to another).
Suburban Perspective
• The weediness of a plant is defined by the
absence of the preceding characteristics.
Thus, suburbia considers any plant a weed
that is well-adapted to its environment,
prone to reproduce itself and spread,
requires little or no effort to maintain, and
has no obvious aesthetic or culinary
properties.
Ecological perspective
• One ecological perspective considers any plant a
weed if it is a pioneer species that thrives in a
degraded habitat with a history of disturbance
through human agency. Such weeds may be native
or introduced.
• There are also superweeds that have the capacity
to invade high quality natural areas. Superweeds
are usually introduced plants with few natural
enemies in the area of invasion. Some ecologists
are only concerned with superweeds.
Fireweed (Epilobium angustifolium) in
London post bombing
Another way to think about weeds
Problem invasive species
Not native to ecosystem.
Increase and spread in ecosystem,
offspring easily dispersed.
Lead to decline in native species via
negative interactions such as competition,
predation or parasitism.
Cause changes in ecosystem properties
such as hydrology, nutrient cycles, energy
flow, fire regime.
Tolerant of human disturbance regimes.
Problem native species
Native to ecosystem.
Effects are ecologically similar to
problem invasive species.
Frequently they are edge species tolerant
of human disturbance.
Another way to think about weeds
Non-problem native species
Non-problem non-native species
Native to ecosystem.
Populations exhibit minor fluctuations in
size and distribution.
Presence enhances other native species.
Maintain ecosystem properties.
Frequently sensitive to human
disturbance regimes.
Not native to ecosystem.
Reproduce and survive in ecosystem.
Populations exhibit minor fluctuations in
size and distribution.
Presence at least is not leading to decline
in native species abundance or
distribution.
Do not lead to changes in ecosystem
properties.
Have potential to become problematic as
climate changes.
Alfalfa (Medicago sativa) – good
crop or weed?
Problem Plants
• Perennial herbs – many examples are found
in wetlands like purple loosestrife and
grasslands like Canada Thistle and our
woods like garlic mustard (a biennial)
Perennial Herb Problems
Purple Loosestrife
Garlic Mustard
Perennial Herb Problems
Canada thistle – Cirsium arvense
Field of Canada Thistle
Problem Plants
• Perennial grasses – replace native grasses in
grazed rangeland and pose a serious fire risk to
native trees in forest ecosystems. Perennial
grasses pose a double fire hazard: 1) they produce
much greater bulk of flammable material than was
produced by native plants and thus lead to more
intense fires, and 2) the timing of their
flammability is different than native plants so that
fires occur at times of the year for which native
plants are not adapted – Smooth Brome and Reed
Canary Grass (Phalaris arundinacea)
Perennial Grass Problems
Smooth Brome
Phalaris arundinacea
Problem Plants
• Vines – Serious pests in woods and
disturbed habitat – field bindweed and
kudzu
Vine Problems
Field Bindweed
Kudzu
Problem Plants
• Shrubs – Very serious problems in most
climates – often become severe problems in
areas where native vegetation has been
overgrazed – multiflora rose
Shrub Problems
Multiflora Rose
Problem Plants
• Trees – trees are potentially disastrous for
nature conservation and watershed
management. Often invasive trees do well
in disturbed, edge habitat and become the
canopy dominants, out-competing native
trees – among our problem trees are autumn
olive (small, almost a shrub), black locust,
tree-of-heaven
Tree Problems
Autumn Olive
Black Locust
Tree of Heaven
Illinois Noxious Weed Act
Section 220.10 Duty of Every Person
a) It shall be the duty of every person to
control the spread of and to eradicate all
noxious weeds on lands owned or
controlled by him in the State of Illinois.
b) All noxious weeds shall be controlled or
eradicated by methods approved and
adopted pursuant to the Act and these rules.
Illinois Noxious Weeds
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Section 220.60 Noxious Weeds
The following plants within the
sovereign territory of the State of
Illinois are designated and declared
noxious weeds:
a) Marihuana (Cannabis sativa L.);
b) Giant Ragweed (Ambrosia
trifida L.) within the corporate
limits of cities, villages, and
incorporated towns;
c) Common Ragweed (Ambrosia
artemisiifolia L.) within the
corporate limits of cities, villages,
and incorporated towns;
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d) Canada Thistle (Cirsium
arvense);
e) Perennial Sowthistle (Sonchus
arvensis);
f) Musk Thistle (Carduus nutans);
g) Perennial members of the
sorghum genus, including
johnsongrass (Sorghum halepense),
sorghum almum, and other
johnsongrass X sorghum crosses
with rhizomes; and
h) Kudzu (Pueraria labata).
(Source: Amended at 26 Ill. Reg.
14644, effective September 23,
2002)
Cannabis sativa
Giant Ragweed
Common Ragweed
Canada Thistle
Perennial Sowthistle
Musk or Nodding Thistle
Johnson Grass
Kudzu
Are weeds of some positive value?
1) Some weedy species are pioneers of
degraded landscapes where the soil is wornout or nearly destroyed. Such weedy species
are necessary to the healing process of the
landscape, as their decaying organic matter
improves the quality of the soil and the sets
the stage for the succession of non-weedy
plants – alfalfa, red clover
Red Clover
Are weeds of some positive value?
2) Some weedy species are pioneers of
disturbed landscapes where the soil is high
quality, but exposed to erosion by wind and
water. Such weedy species quickly cover
the exposed soil and prevent erosion from
occurring until they are replaced by nonweedy plants – annual ryegrass
Annual Ryegrass
Are weeds of some positive value?
3) Weedy plants are often important sources
of food and cover to various kinds of
wildlife, including mammals, birds, and
insects. For example, the caterpillars of
Papilio polyxenes asterias (Black
Swallowtail butterfly) feed on Daucus
carota (Wild Carrot) and Pastinaca sativa
(Wild Parsnip).
Wild Carrot and Wild Parsnip
Black Swallowtail
European goldfinch on Canada thistle
Autumn olive along roadside
Autumn olive fruits
Are weeds of some positive value?
4) Weedy plants are potentially important sources of
food, medicines, herbicides, and other products to
modern society. For example, our major food
crops are almost all weeds in terms of being exotic
species for the Midwest and some of them such as
apples can survive outside of cultivation. A
powerful herbicide has been derived from
Centaurea biebersteinii (Spotted Knapweed),
while the fiber of Cannabis sativa (Marijuana) can
be used to make paper, rope, or clothing.
Spotted Knapweed
Cannabis/Hemp Fibers
Cannabis/Hemp Fibers