Transcript Slide 1

4) Impacts
4) Impacts
Some observations:
• Measuring impact is complex
What should be measured and how?
4) Impacts
Some observations:
• Measuring impact is complex
What should be measured and how?
For individual plant, individual species, or multiple species?
4) Impacts
Some observations:
• Measuring impact is complex
What should be measured and how?
For individual plant, individual species, or multiple species?
Over what time frame?
4) Impacts
Some observations:
• Measuring impact is complex
• Lack of comprehensive data
4) Impacts
a) Ecological
Conceptual model: From Walker & Smith in Lukens & Thieret (1997)
• Invasive species affect different community & ecosystem
processes
4) Impacts
a) Ecological
Conceptual model: From Walker & Smith in Lukens & Thieret (1997)
• Invasive species affect:
Nutrient & water availability
4) Impacts
a) Ecological
Conceptual model: From Walker & Smith in Lukens & Thieret (1997)
• Invasive species affect:
Nutrient & water availability
Primary productivity
4) Impacts
a) Ecological
Conceptual model: From Walker & Smith in Lukens & Thieret (1997)
• Invasive species affect:
Nutrient & water availability
Primary productivity
Disturbance regimes
4) Impacts
a) Ecological
Conceptual model: From Walker & Smith in Lukens & Thieret (1997)
• Invasive species affect:
Nutrient & water availability
Primary productivity
Disturbance regimes
Community dynamics
4) Impacts
a) Ecological
i) Species replacement
• Direct competition From Sherer-Lorenzen in Mooney & Hobbs
(2000)
Moist, nutrient rich, disturbed sites in central Europe
4) Impacts
a) Ecological
i) Species replacement
• Direct competition From ShererLorenzen in Mooney & Hobbs
(2000)
Moist, nutrient rich, disturbed
sites in central Europe
Typically dominated by native
herb Urtica dioica (stinging
nettle)
Helianthus tuberosus
(Jerusalem artichoke)
invading
Helianthus (invasive)
Urtica (native)
4) Impacts
a) Ecological
i) Species replacement
• Direct competition From ShererLorenzen in Mooney & Hobbs
(2000)
Moist, nutrient rich, disturbed
sites in central Europe
Typically dominated by native herb
Urtica dioica (stinging nettle)
Helianthus tuberosus (Jerusalem
artichoke) invading
Helianthus undermines and
outshades Urtica, displacing
it
Helianthus (invasive)
Urtica (native)
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002)
Ecological Applications 12:1434-1444
3 coastal habitats in SF Bay Area
Invasive = Delairea odorata (Cape
ivy) evergreen vine native to
South Africa
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002)
Cape ivy invading coastal habitats
Decreases species richness for
natives (36%)
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002)
Cape ivy invading coastal habitats
Decreases species richness for
natives & non-natives (37%)
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002)
Cape ivy invading coastal habitats
Decreases species richness for
natives & non-natives and species
diversity (31%)
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002) Cape
ivy invading coastal habitats
Fewer native & non-native species
Decreases occur across all habitat
types
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002)
Cape ivy invading coastal habitats
Fewer native & non-native species
across all habitats and for all plant
life forms
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002)
Cape ivy invading coastal habitats
Fewer native & non-native species
Experimentally removed Cape ivy:
Control = no removal
Disturbance = insert pitchfork
into soil to simulate soil
disturbance that
accompanies plant removal
Reduction = hand weeded Cape
ivy
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002)
Cape ivy invading coastal habitats
Fewer native & non-native species
Experimentally removed Cape ivy:
Natives richness ↑ (10%)
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002) Cape
ivy invading coastal habitats
Fewer native & non-native species
Experimentally removed Cape ivy:
Natives richness ↑ (10%)
Non-natives richness ↑ (43%)
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002)
Cape ivy invading coastal habitats
Fewer native & non-native species
Experimentally removed Cape ivy:
Natives richness ↑ (10%)
Non-natives richness ↑ (43%)
Diversity ↑ (32%)
4) Impacts
a) Ecological
i) Species replacement
• Direct competition
• Large scale species displacements
From Alvarez & Cushman (2002)
Cape ivy invading coastal habitats
Fewer native & non-native species
Experimentally removed Cape ivy:
Other species recover,
especially forbs (other life
forms NS)
4) Impacts
a) Ecological
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors
From D’Antonio et al. (2000) Austral Ecology 25: 507-522
Series of 14 study sites (#’s) from eastern coastal lowlands to
seasonal submontane zone on Big Island, Hawaii
4) Impacts
a) Ecological
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors
From D’Antonio et al. (2000)
Series of 14 study sites (#’s) from eastern coastal lowlands to
seasonal submontane zone on Big Island, Hawaii
Lowlands: warm tropical zone with 1500-2000 mm yr-1, but dry
summers; elevation from sea level to 400 m
Submontane: several °C cooler, but similar amount and
seasonality of precipitation; 400 – 1200 m elevation
4) Impacts
a) Ecological
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors
From D’Antonio et al. (2000)
Series of 14 study sites (#’s) from eastern coastal lowlands to
seasonal submontane zone on Big Island, Hawaii
Lowlands: warm tropical zone with 1500-2000 mm yr-1, but dry
summers; elevation from sea level to 400 m
Submontane: several °C cooler, but similar amount and seasonality
of precipitation; 400 – 1200 m elevation
In both zones, fires occur; most ignited by lava or by humans
Do fires consistently favor invasives across this elevational
gradient?
4) Impacts
a) Ecological
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Measured cover of native species
4) Impacts
a) Ecological
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Measured cover of native and exotic species
4) Impacts
a) Ecological
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Measured cover of native and exotic species in adjacent
unburned
4) Impacts
a) Ecological
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Measured cover of native and exotic species in adjacent
unburned and burned sites along gradient
4) Impacts
a) Ecological
Individual sites
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Measured cover of native and exotic species in adjacent
unburned and burned sites along gradient
4) Impacts
a) Ecological
Individual sites
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
For seasonal submontane:
For 26 of 35 (74%) occurrences, native had ↓ cover in
burned areas
4) Impacts
a) Ecological
Individual sites
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
For seasonal submontane:
For 26 of 35 (74%) occurrences, native had ↓ cover in
burned areas
For 28 of 41 (68%) occurrences, exotics had ↑ cover
4) Impacts
a) Ecological
Individual sites
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Submontane: Many natives ↓ & many exotics ↑ with fire
4) Impacts
a) Ecological
Individual sites
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Submontane: Many natives ↓ & many exotics ↑ with fire
For coastal lowlands:
14 of 26 (54%) natives ↓
6 of 29 (29%) of exotics ↑
4) Impacts
a) Ecological
Individual sites
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Submontane: Many natives ↓ & many exotics ↑ with fire
Lowlands: Fewer natives ↓ & fewer exotics ↑ with fire
4) Impacts
a) Ecological
Individual sites
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Yes, but not uniformly
4) Impacts
a) Ecological
Individual sites
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Yes, but not uniformly
Not due to differences in rainfall amount or seasonality
4) Impacts
a) Ecological
Individual sites
i)
•
•
•
Species replacement
Direct competition
Large scale species displacements
Interacting factors From D’Antonio et al. (2000)
Do fires favor invasives across elevational gradient?
Yes, but not uniformly
Not due to differences in rainfall amount or seasonality
Appears to be due to differences in native species
composition: some of the species in coastal lowlands
appear to be fire tolerant
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
From Walker & Smith in Lukens &
Thieret (1997)
Summarized: Typical effects of
invasive on specific processes
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
From Walker & Smith in Lukens &
Thieret (1997)
Summarized: Typical effects of invasive
on specific processes
And how this change on a specific
process then feeds back and
affects community function or
structure
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
From Walker & Smith in Lukens &
Thieret (1997)
Summarized: Typical effects of
invasive on specific processes
And how this change on a specific
process then feeds back and affects
community function or structure
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
From Walker & Smith in Lukens &
Thieret (1997)
Summarized: Typical effects of invasive
on specific processes
And how this change on a specific
process then feeds back and
affects community function or
structure
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
From Walker & Smith in Lukens &
Thieret (1997)
Summarized: Typical effects of invasive
on specific processes
And how this change on a specific
process then feeds back and
affects community function or
structure
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
From Walker & Smith in Lukens &
Thieret (1997)
Summarized: Typical effects of invasive
on specific processes
And how this change on a specific
process then feeds back and
affects community function or
structure
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
From Walker & Smith in Lukens &
Thieret (1997)
Summarized: Typical effects of invasive
on specific processes
And how this change on a specific
process then feeds back and affects
community function or structure
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific example: Ecosystem C storage
From Jackson et al. (2002) Nature 418:623-626
Woody plant invasion into grasslands thought to increase
amount of C stored
If so, then woody plant invasions are good for C sequestration
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific example: Ecosystem C storage
From Jackson et al. (2002)
Does woody plant invasion increase C sequestration?
Examined 6 sites along precipitation gradient (200 – 1100 mm)
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific example: Ecosystem C storage
From Jackson et al. (2002)
Does woody plant invasion increase C sequestration?
Examined 6 sites along precipitation gradient (200 – 1100 mm)
that had similar age of woody plant invasion
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific example: Ecosystem C storage
From Jackson et al. (2002)
Does woody plant invasion increase C sequestration?
Sites along precipitation gradient
Measured total soil organic carbon
in soil profile
Calculated total soil organic C for
0-3 m depth for both grass &
invaded sites
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific example: Ecosystem C storage
From Jackson et al. (2002)
Does woody plant invasion increase C sequestration?
Sites along precipitation gradient
Plot proportion of total soil organic C
in woody invaded / grass
(>1 means more SOC in woody)
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific example: Ecosystem C storage
From Jackson et al. (2002)
Does woody plant invasion increase C sequestration?
Sites along precipitation gradient
Plot proportion of total soil organic C
in woody invaded / grass
vs. precipitation
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific example: Ecosystem C storage
From Jackson et al. (2002)
Does woody plant invasion increase C sequestration?
Contrary to expectations, ↑ only
for dry sites
As precipitation ↑, get less SOC
in woody invaded areas
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific example: Soil N change
From Vitousek & Walker (1989) Ecological Monographs 59:247-265
Myrica faya small evergreen tree native to Canary Islands &
other islands in North Atlantic Ocean
Actinorhizal N-fixer
Brought to Hawaii, where is invading young lava flows that
had been dominated by natives
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific example: Soil N change
From Vitousek & Walker (1989)
Exotic Myrica faya, actinorhizal N-fixer, greatly ↑ annual N
input into young lava flows
LB = Lower Byron; high density of Myrica for >10 years
UB = Upper Byron; kept free of Myrica
>


>
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific example: Soil N change
From Vitousek & Walker (1989)
Exotic Myrica faya, actinorhizal N-fixer, greatly ↑ annual N
input into young lava flows
High N facilitates the invasion of other exotic plants
>


>
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific examples: Fire effects
From D’Antonio in Mooney & Hobbs (2002)
Compiled 20 examples from around the world where invaders
have altered fire regimes
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific examples: Fire effects
From D’Antonio in Mooney & Hobbs (2002)
20 examples where invaders have altered fire regimes
Majority involve perennial grasses (13 of 20 = 65%)
4 (20%) involve annual grasses – All are in arid West
Other 3 are trees / shrubs (Florida, South Africa)
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific examples: Fire effects
From D’Antonio in Mooney & Hobbs (2002)
20 examples where invaders have altered fire regimes
Majority involve perennial grasses (13 of 20 = 65%)
4 (20%) involve annual grasses – All are in arid West
Other 3 are trees / shrubs (Florida, South Africa)
Majority of invaders represent new life form (14 of 20 = 70%)
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific examples: Fire effects
From D’Antonio in Mooney & Hobbs (2002)
20 examples where invaders have altered fire regimes
Majority involve perennial grasses (13 of 20 = 65%)
4 (20%) involve annual grasses – All are in arid West
Other 3 are trees / shrubs (Florida, South Africa)
Majority of invaders represent new life form (14 of 20 = 70%)
Majority ↑ fire frequency (14; 70%)
Only 2 (10%) ↓ frequency
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific examples: Fire effects
From D’Antonio in Mooney & Hobbs (2002)
20 examples where invaders have altered fire regimes
Majority involve perennial grasses (13 of 20 = 65%)
4 (20%) involve annual grasses – All are in arid West
Other 3 are trees / shrubs (Florida, South Africa)
Majority of invaders represent new life form (14 of 20 = 70%)
Majority ↑ fire frequency (14; 70%)
Only 2 (10%) ↓ frequency
Majority ↑ fire size or intensity (11; 55%)
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific examples: General compilation
From Crooks (2002)
4) Impacts
a) Ecological
ii) Ecosystem functions
• Overview
• Specific examples
From Crooks (2002)
Ecosystem engineers:
• Alter ecosystem physical
processes
(water use, N cycling)
• Change habitat structure
(more
complexity, less complexity)
• Effects cascade through
community
4) Impacts
a) Ecological
iii) Threatened & endangered species
• Overview
~400 of 958 federally listed species (~42%) are because of
invasives (includes plants plus other organisms)
4) Impacts
a) Ecological
iii) Threatened & endangered species
• Overview
~42% are because of invasives
Effects can be by:
Direct species replacement
Indirect through effects on community structure or function
4) Impacts
a) Ecological
iii) Threatened & endangered species
• Overview
• Specific examples: King Ranch bluestem
Bothriochloa ischaemum (Caucasian bluestem) brought in to
southern Great Plains (NM, OK, TX) from Russia in 1929
C4 perennial bunchgrass:
establishes readily from seed
long growing season
tolerates heavy grazing
fair forage quality
forms dense sod in mature pastures
4) Impacts
a) Ecological
iii) Threatened & endangered species
• Overview
• Specific examples: King Ranch bluestem
Bothriochloa ischaemum (Caucasian bluestem) brought in to
southern Great Plains (NM, OK, TX) from Russia in 1929
C4 perennial bunchgrass: desirable forage species
Seeded extensively (for example, ~2 million acres in western
OK)
4) Impacts
a) Ecological
iii) Threatened & endangered species
• Overview
• Specific examples: King Ranch bluestem
Bothriochloa ischaemum (Caucasian bluestem) brought in to
southern Great Plains (NM, OK, TX) from Russia in 1929
C4 perennial bunchgrass: desirable forage species
Seeded extensively
But extremely invasive:
Spread along highways into native areas (cemetaries,
native grasslands)
Difficult to control
Threatens federally listed endangered plant Ambrosia
cheiranthefolia (south Texas ambrosia)
4) Impacts
a) Ecological
iii) Threatened & endangered species
• Overview
• Specific examples: Hawaii
80-90 native plant species extinct
270 plant species listed as threatened or endangered
4) Impacts
a) Ecological
Summary
• Ecological impacts typically involve: (1) nutrients/water flow; (2)
primary production impacts; (3) alterations of disturbance
regimes; and (4) changes in community dynamics
4) Impacts
a) Ecological
Summary
• Ecological impacts typically involve: (1) nutrients/water flow; (2)
primary production impacts; (3) alterations of disturbance regimes;
and (4) changes in community dynamics
• Effects observed as:
Species replacements (direct/individual or large scale, w/ or
w/o interactions with other factors such as fire)
4) Impacts
a) Ecological
Summary
• Ecological impacts typically involve: (1) nutrients/water flow; (2)
primary production impacts; (3) alterations of disturbance regimes;
and (4) changes in community dynamics
• Effects observed as:
Species replacements (direct/individual or large scale, w/ or w/o
interactions with other factors such as fire)
Ecosystem functions (C sequestration, N fixation, fire
frequency/intensity)
4) Impacts
a) Ecological
Summary
• Ecological impacts typically involve: (1) nutrients/water flow; (2)
primary production impacts; (3) alterations of disturbance regimes;
and (4) changes in community dynamics
• Effects observed as:
Species replacements (direct/individual or large scale, w/ or w/o
interactions with other factors such as fire)
Ecosystem functions (C sequestration, N fixation, fire
frequency/intensity)
Complete or nearly complete loss of native species
(threatened or endangered species)