4)Impacts a)Ecological Conceptual model: From Walker & Smith in Lukens & Thieret (1997)...

4) Impactsa) Ecological

Conceptual model: From Walker & Smith in Lukens & Thieret (1997)• Invasive species affect:

Nutrient & water availability

4) Impactsa) Ecological

Conceptual model: From Walker & Smith in Lukens & Thieret (1997)• Invasive species affect:

Nutrient & water availabilityPrimary productivity

4) Impactsa) Ecological

Conceptual model: From Walker & Smith in Lukens & Thieret (1997)• Invasive species affect:

Nutrient & water availabilityPrimary productivityDisturbance regimes

4) Impactsa) Ecological

Conceptual model: From Walker & Smith in Lukens & Thieret (1997)• Invasive species affect:

Nutrient & water availabilityPrimary productivityDisturbance regimesCommunity dynamics

3) Impactsa) Ecological

i) Species replacement• Direct competition From Sherer-Lorenzen in Mooney & Hobbs

(2000)Moist, nutrient rich, disturbed sites in central Europe

3) Impactsa) Ecological

i) Species replacement• Direct competition From Sherer-

Lorenzen in Mooney & Hobbs (2000)Moist, nutrient rich, disturbed

sites in central EuropeTypically dominated by native

herb Urtica dioica (stinging nettle)

Helianthus tuberosus (Jerusalem artichoke) invading

Urtica (native)Helianthus (invasive)

3) Impactsa) Ecological

i) Species replacement• Direct competition From Sherer-

Lorenzen in Mooney & Hobbs (2000)Moist, nutrient rich, disturbed

sites in central EuropeTypically dominated by native herb

Urtica dioica (stinging nettle)Helianthus tuberosus (Jerusalem

artichoke) invadingHelianthus undermines and

outshades Urtica, displacing it

Urtica (native)Helianthus (invasive)

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002) Ecological Applications 12:1434-14443 coastal habitats in SF Bay AreaInvasive = Delairea odorata (Cape

ivy) evergreen vine native to South Africa

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002)Cape ivy invading coastal habitatsDecreases species richness for

natives (36%)

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002)Cape ivy invading coastal habitatsDecreases species richness for

natives & non-natives (37%)

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002)Cape ivy invading coastal habitatsDecreases species richness for

natives & non-natives and species diversity (31%)

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002) Cape ivy invading coastal habitatsFewer native & non-native speciesDecreases occur across all habitat

types

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002)Cape ivy invading coastal habitatsFewer native & non-native species

across all habitats and for all plant life forms

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002)Cape ivy invading coastal habitatsFewer native & non-native speciesExperimentally removed Cape ivy:

Control = no removalDisturbance = insert pitchfork

into soil to simulate soil disturbance that accompanies plant removal

Reduction = hand weeded Cape ivy

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002)Cape ivy invading coastal habitatsFewer native & non-native speciesExperimentally removed Cape ivy:

Natives richness ↑ (10%)

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002) Cape ivy invading coastal habitatsFewer native & non-native speciesExperimentally removed Cape ivy:

Natives richness ↑ (10%)Non-natives richness ↑ (43%)

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002)Cape ivy invading coastal habitatsFewer native & non-native speciesExperimentally removed Cape ivy:

Natives richness ↑ (10%)Non-natives richness ↑ (43%)Diversity ↑ (32%)

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements

From Alvarez & Cushman (2002)Cape ivy invading coastal habitatsFewer native & non-native speciesExperimentally removed Cape ivy:

Other species recover,especially forbs (other life

forms NS)

3) Impactsa) Ecological

i) Species replacement• Direct competition• Large scale species displacements• Interacting factors

From D’Antonio et al. (2000) Austral Ecology 25: 507-522Series of 14 study sites (#’s) from eastern coastal lowlands to

seasonal submontane zone on Big Island, Hawaii

3) Impactsa) 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, HawaiiLowlands: warm tropical zone with 1500-2000 mm yr-1, but dry

summers; elevation from sea level to 400 mSubmontane: several °C cooler, but similar amount and

seasonality of precipitation; 400 – 1200 m elevation

3) Impactsa) 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, HawaiiLowlands: warm tropical zone with 1500-2000 mm yr-1, but dry

summers; elevation from sea level to 400 mSubmontane: several °C cooler, but similar amount and seasonality

of precipitation; 400 – 1200 m elevationIn both zones, fires occur; most ignited by lava or by humansDo fires consistently favor invasives across this elevational

gradient?

3) Impactsa) 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

3) Impactsa) 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

3) Impactsa) 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

3) Impactsa) 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

3) Impactsa) 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

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3) Impactsa) 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?For seasonal submontane:

For 26 of 35 (74%) occurrences, native had ↓ cover in burned areas

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3) Impactsa) 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?For seasonal submontane:

For 26 of 35 (74%) occurrences, native had ↓ cover in burned areas

For 28 of 41 (68%) occurrences, exotics had ↑ cover

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3) Impactsa) 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?Submontane: Many natives ↓ & many exotics ↑ with fire

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3) Impactsa) 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?Submontane: Many natives ↓ & many exotics ↑ with fireFor coastal lowlands:

14 of 26 (54%) natives ↓6 of 29 (29%) of exotics ↑

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3) Impactsa) 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?Submontane: Many natives ↓ & many exotics ↑ with fireLowlands: Fewer natives ↓ & fewer exotics ↑ with fire

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3) Impactsa) 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?Yes, but not uniformly

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3) Impactsa) 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?Yes, but not uniformlyNot due to differences in rainfall amount or seasonality

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3) Impactsa) Ecological

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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 uniformlyNot due to differences in rainfall amount or seasonalityAppears to be due to differences in native species

composition: some of the species in coastal lowlands appear to be fire tolerant

3) Impactsa) Ecological

ii) Ecosystem functions• Overview

From Walker & Smith in Lukens & Thieret (1997)

Summarized: Typical effects of invasive on specific processes

3) Impactsa) Ecological

ii) Ecosystem functions• Overview

From Walker & Smith in Lukens & Thieret (1997)

Summarized: Typical effects of invasive on specific processesAnd how this change on a specific process then feeds back and affects community function or structure

3) Impactsa) Ecological

ii) Ecosystem functions• Overview

From Walker & Smith in Lukens & Thieret (1997)

Summarized: Typical effects of invasive on specific processesAnd how this change on a specific process then feeds back and affects community function or structure

3) Impactsa) Ecological

ii) Ecosystem functions• Overview

From Walker & Smith in Lukens & Thieret (1997)

Summarized: Typical effects of invasive on specific processesAnd how this change on a specific process then feeds back and affects community function or structure

3) Impactsa) Ecological

ii) Ecosystem functions• Overview

From Walker & Smith in Lukens & Thieret (1997)

Summarized: Typical effects of invasive on specific processesAnd how this change on a specific process then feeds back and affects community function or structure

3) Impactsa) Ecological

ii) Ecosystem functions• Overview• Specific example: Ecosystem C storage

From Jackson et al. (2002) Nature 418:623-626Woody plant invasion into grasslands thought to increase

amount of C storedIf so, then woody plant invasions are good for C sequestration

3) Impactsa) 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)

3) Impactsa) 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

3) Impactsa) 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 gradientMeasured total soil organic carbon

in soil profileCalculated total soil organic C for

0-3 m depth for both grass &invaded sites

3) Impactsa) 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 gradientPlot proportion of total soil organic C

in woody invaded / grass(>1 means more SOC in woody)

3) Impactsa) 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 gradientPlot proportion of total soil organic C

in woody invaded / grassvs. precipitation

3) Impactsa) 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, ↑ onlyfor dry sites

As precipitation ↑, get less SOCin woody invaded areas

3) Impactsa) Ecological

ii) Ecosystem functions• Overview• Specific example: Soil N change

From Vitousek & Walker (1989) Ecological Monographs 59:247-265Myrica faya small evergreen tree native to Canary Islands &

other islands in North Atlantic OceanActinorhizal N-fixerBrought to Hawaii, where is invading young lava flows that

had been dominated by natives

3) Impactsa) 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

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3) Impactsa) 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 flowsHigh N facilitates the invasion of other exotic plants

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3) Impactsa) 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

3) Impactsa) Ecological

ii) Ecosystem functions• Overview• Specific examples: Fire effects

From D’Antonio in Mooney & Hobbs (2002)20 examples where invaders have altered fire regimesMajority involve perennial grasses (13 of 20 = 65%)

4 (20%) involve annual grasses – All are in arid WestOther 3 are trees / shrubs (Florida, South Africa)

3) Impactsa) Ecological

ii) Ecosystem functions• Overview• Specific examples: Fire effects

From D’Antonio in Mooney & Hobbs (2002)20 examples where invaders have altered fire regimesMajority involve perennial grasses (13 of 20 = 65%)

4 (20%) involve annual grasses – All are in arid WestOther 3 are trees / shrubs (Florida, South Africa)

Majority of invaders represent new life form (14 of 20 = 70%)

3) Impactsa) Ecological

ii) Ecosystem functions• Overview• Specific examples: Fire effects

From D’Antonio in Mooney & Hobbs (2002)20 examples where invaders have altered fire regimesMajority involve perennial grasses (13 of 20 = 65%)

4 (20%) involve annual grasses – All are in arid WestOther 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

3) Impactsa) Ecological

ii) Ecosystem functions• Overview• Specific examples: Fire effects

From D’Antonio in Mooney & Hobbs (2002)20 examples where invaders have altered fire regimesMajority involve perennial grasses (13 of 20 = 65%)

4 (20%) involve annual grasses – All are in arid WestOther 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%) ↓ frequencyMajority ↑ fire size or intensity (11; 55%)

3) Impactsa) Ecological

ii) Ecosystem functions• Overview• Specific examples: General compilation

From Crooks (2002)

3) Impactsa) Ecological

iii) Threatened & endangered species• Overview

~400 of 958 federally listed species (~42%) are because of invasives (includes plants plus other organisms)

3) Impactsa) Ecological

iii) Threatened & endangered species• Overview

~42% are because of invasivesEffects can be by:

Direct species replacementIndirect through effects on community structure or function

3) Impactsa) 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 seedlong growing seasontolerates heavy grazingfair forage qualityforms dense sod in mature pastures

3) Impactsa) 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 speciesSeeded extensively (for example, ~2 million acres in western

OK)

3) Impactsa) 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 speciesSeeded extensivelyBut extremely invasive:

Spread along highways into native areas (cemetaries, native grasslands)

Difficult to controlThreatens federally listed endangered plant Ambrosia

cheiranthefolia (south Texas ambrosia)

3) Impactsa) Ecological

iii) Threatened & endangered species• Overview• Specific examples: Hawaii

80-90 native plant species extinct270 plant species listed as threatened or endangered

3) Impactsa) Ecological

Summary• Only a small percentage (0.1%) of introduced plants become a

problem

3) Impactsa) Ecological

Summary• Only a small percentage (0.1%) of introduced plants become a

problem• Ecological impacts typically involve: (1) nutrients/water flow; (2)

primary production impacts; (3) alterations of disturbance regimes; and (4) changes in community dynamics

3) Impactsa) Ecological

Summary• Only a small percentage (0.1%) of introduced plants become a

problem• 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)

3) Impactsa) Ecological

Summary• Only a small percentage (0.1%) of introduced plants become a

problem• 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)

3) Impactsa) Ecological

Summary• Only a small percentage (0.1%) of introduced plants become a

problem• 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)