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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)
