Impacts of Invasive Plant
Species
Carla Bossard
St. Mary’s College of California
Less than 1.5% of non-natives are invasive,
but those have very real, very serious impacts
Impacts of invasive plant species
I. Dominate habitat displacing natives
II. Hybridize
III. Dominate and change the physical
conditions of the habitat
I. Habitat Dominance with
Displacement of Native Species
a. Out competing native
species
b. Suppress recruitment
c. Alter community
structure
d. Degrade habitat for
native animals
e. Provide resources for
undesirable nonnative animals
Many invasive plant species do several of the above.
a.
Why can
invasive species
outcompete
natives?
• Local herbivores
and diseases do not
effect them but do
effect the natives
• Little to control their
population growth
Broom in UK above
and CA below
a.
Why? cont. Suite of traits
Many natives are
stress tolerators,
slow-growing
specialist species;
invasives tend to
be opportunists
with high
reproductive
allocation, good
dispersal of long
viable seeds, high
RGR, broad
tolerance ranges
b.
Recruitment of
natives suppressed
(- light, -water)
c. Alter community structure
d.
Less
forage
Degrade food and
shelter for native fauna
Decreased
nesting sites
Can change feeding
relationships
Too much
cover
Too little
cover
e.
Provide resources for undesirable
non-natives
II.
Invasives hybridize with native
species
III. Some invasives cause
ecosystem effects … transformers
Impact by changing:
a. Nutrient cycling
b. Soil chemistry
c. Intensity and frequency of fire
d. Hydrologic cycles/ Sediment deposition
e. Erosion/topography
a.
Nutrient
cycling
b.
Soil
chemistry
alteration
c.
Fire cycle
disruption
-water
+salinity
Hydrologic cycle/sedimention rate
d.
change
e.
Erosion/ topography
If invasive plant species are not
controlled and removed will
diverse native biological
communities continue to exist?