Impacts
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Impacts. Impacts. Some observations: Measuring impact is complex What should be measured and how?. Impacts. Some observations: Measuring impact is complex What should be measured and how? For individual plant, individual species, or multiple species?. Impacts. Some observations:

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Impacts

  • Impacts


Impacts

  • Impacts

  • Some observations:

  • Measuring impact is complex

    • What should be measured and how?


Impacts

  • Impacts

  • Some observations:

  • Measuring impact is complex

    • What should be measured and how?

    • For individual plant, individual species, or multiple species?


Impacts

  • 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?


Impacts

  • Impacts

  • Some observations:

  • Measuring impact is complex

  • Lack of comprehensive data


Impacts

  • Impacts

    • Ecological

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

  • Invasive species affect different community & ecosystem processes


Impacts

  • Impacts

    • Ecological

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

  • Invasive species affect:

    • Nutrient & water availability


Impacts

  • Impacts

    • Ecological

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

  • Invasive species affect:

    • Nutrient & water availability

    • Primary productivity


Impacts

  • Impacts

    • Ecological

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

  • Invasive species affect:

    • Nutrient & water availability

    • Primary productivity

    • Disturbance regimes


Impacts

  • Impacts

    • Ecological

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

  • Invasive species affect:

    • Nutrient & water availability

    • Primary productivity

    • Disturbance regimes

    • Community dynamics


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition From Sherer-Lorenzen in Mooney & Hobbs (2000)

    • Moist, nutrient rich, disturbed sites in central Europe


Impacts

  • Impacts

    • Ecological

Urtica (native)

Helianthus (invasive)

  • i)Species replacement

  • Direct competition From Sherer-Lorenzen in Mooney & Hobbs (2000)

    • Moist, nutrient rich, disturbed sites in central Europe

    • Typically dominated by native herbUrtica dioica (stinging nettle)

    • Helianthus tuberosus(Jerusalem artichoke) invading


Impacts

  • Impacts

    • Ecological

Urtica (native)

Helianthus (invasive)

  • i)Species replacement

  • Direct competition From Sherer-Lorenzen 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements From Alvarez & Cushman (2002)

    • Cape ivy invading coastal habitats

    • Decreases species richness for natives (36%)


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements From Alvarez & Cushman (2002)

    • Cape ivy invading coastal habitats

    • Decreases species richness for natives & non-natives (37%)


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements From Alvarez & Cushman (2002)

    • Cape ivy invading coastal habitats

    • Decreases species richness for natives & non-natives and species diversity (31%)


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements From Alvarez & Cushman (2002) Cape ivy invading coastal habitats

    • Fewer native & non-native species

    • Decreases occur across all habitat types


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements From Alvarez & Cushman (2002)

    • Cape ivy invading coastal habitats

    • Fewer native & non-native species across all habitats and for all plant life forms


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements From Alvarez & Cushman (2002)

    • Cape ivy invading coastal habitats

    • Fewer native & non-native species

    • Experimentally removed Cape ivy:

      • Natives richness ↑ (10%)


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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%)


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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%)


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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)


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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?


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements

  • Interacting factors From D’Antonio et al. (2000)

    • Do fires favor invasives across elevational gradient?

    • Measured cover of native species


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements

  • Interacting factors From D’Antonio et al. (2000)

    • Do fires favor invasives across elevational gradient?

    • Measured cover of native and exotic species


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements

  • Interacting factors From D’Antonio et al. (2000)

    • Do fires favor invasives across elevational gradient?

    • Measured cover of native and exotic speciesin adjacent unburned and burned sites along gradient


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements

  • Interacting factors From D’Antonio et al. (2000)

    • Do fires favor invasives across elevational gradient?

    • Measured cover of native and exotic speciesin adjacent unburned and burned sites along gradient

Individual sites


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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

Individual sites


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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

Individual sites


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements

  • Interacting factors From D’Antonio et al. (2000)

    • Do fires favor invasives across elevational gradient?

    • Submontane: Many natives ↓ & many exotics ↑ with fire

Individual sites


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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 ↑

Individual sites


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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

Individual sites


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies displacements

  • Interacting factors From D’Antonio et al. (2000)

    • Do fires favor invasives across elevational gradient?

      • Yes, but not uniformly

Individual sites


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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

Individual sites


Impacts

  • Impacts

    • Ecological

  • i)Species replacement

  • Direct competition

  • Large scalespecies 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

Individual sites


Impacts

  • Impacts

    • Ecological

  • ii)Ecosystem functions

  • Overview

    • From Walker & Smith in Lukens & Thieret (1997)

    • Summarized: Typical effects of invasive on specific processes


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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)


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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)


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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

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>


Impacts

  • Impacts

    • 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

>

>


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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)


Impacts

  • Impacts

    • 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%)


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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%)


Impacts

  • Impacts

    • Ecological

  • ii)Ecosystem functions

  • Overview

  • Specific examples: General compilation

    • From Crooks (2002)


Impacts

  • Impacts

    • Ecological

  • Ecosystem engineers:

    • Alter ecosystem physical processes

    • (water use, N cycling)

    • Change habitat structure (more

    • complexity, less complexity)

    • Effects cascade through community

  • ii)Ecosystem functions

  • Overview

  • Specific examples

    • From Crooks (2002)


Impacts

  • Impacts

    • Ecological

  • iii)Threatened & endangered species

  • Overview

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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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)


Impacts

  • Impacts

    • 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)


Impacts

  • Impacts

    • Ecological

  • iii)Threatened & endangered species

  • Overview

  • Specific examples: Hawaii

    • 80-90 native plant species extinct

    • 270 plant species listed as threatened or endangered


Impacts

  • Impacts

    • 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


Impacts

  • Impacts

    • 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)


Impacts

  • Impacts

    • 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)


Impacts

  • Impacts

    • 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)


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