Impacts

1

• Impacts

2

• Impacts

• Some observations
• Measuring impact is complex
• What should be measured and how?

3

• 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?

5

• Impacts

• Some observations
• Measuring impact is complex
• Lack of comprehensive data

6

• Impacts
• Ecological

• Conceptual model From Walker Smith in Lukens
  Thieret (1997)
• Invasive species affect different community
  ecosystem processes

7

• Impacts
• Ecological

• Conceptual model From Walker Smith in Lukens
  Thieret (1997)
• Invasive species affect
• Nutrient water availability

8

• Impacts
• Ecological

• Conceptual model From Walker Smith in Lukens
  Thieret (1997)
• Invasive species affect
• Nutrient water availability
• Primary productivity

9

• Impacts
• Ecological

• Conceptual model From Walker Smith in Lukens
  Thieret (1997)
• Invasive species affect
• Nutrient water availability
• Primary productivity
• Disturbance regimes

10

• Impacts
• Ecological

• Conceptual model From Walker Smith in Lukens
  Thieret (1997)
• Invasive species affect
• Nutrient water availability
• Primary productivity
• Disturbance regimes
• Community dynamics

11

• Impacts
• Ecological

• i) Species replacement
• Direct competition From Sherer-Lorenzen in Mooney
  Hobbs (2000)
• Moist, nutrient rich, disturbed sites in central
  Europe

12

• 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

13

• 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

14

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements From Alvarez
  Cushman (2002) Ecological Applications
  121434-1444
• 3 coastal habitats in SF Bay Area
• Invasive Delairea odorata (Cape ivy) evergreen
  vine native to South Africa

15

• Impacts
• 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)

16

• Impacts
• 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)

17

• Impacts
• 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)

18

• Impacts
• 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

19

• Impacts
• 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

20

• Impacts
• 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

21

• Impacts
• 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)

22

• Impacts
• 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)

23

• Impacts
• 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)

24

• Impacts
• 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)

25

• Impacts
• Ecological

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

26

• Impacts
• Ecological

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

27

• Impacts
• Ecological

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

28

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio et al. (2000)
• Do fires favor invasives across elevational
  gradient?
• Measured cover of native species

29

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio et al. (2000)
• Do fires favor invasives across elevational
  gradient?
• Measured cover of native and exotic species

30

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio et al. (2000)
• Do fires favor invasives across elevational
  gradient?
• Measured cover of native and exotic species in
  adjacent unburned

31

• Impacts
• Ecological

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

32

• Impacts
• Ecological

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

Individual sites
33

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio 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
34

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio 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
35

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio et al. (2000)
• Do fires favor invasives across elevational
  gradient?
• Submontane Many natives ? many exotics ? with
  fire

Individual sites
36

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio 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
37

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio 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
38

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio et al. (2000)
• Do fires favor invasives across elevational
  gradient?
• Yes, but not uniformly

Individual sites
39

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio 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
40

• Impacts
• Ecological

• i) Species replacement
• Direct competition
• Large scale species displacements
• Interacting factors From DAntonio 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
41

• Impacts
• Ecological

• ii) Ecosystem functions
• Overview
• From Walker Smith in Lukens Thieret (1997)
• Summarized Typical effects of invasive on
  specific processes

42

• 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

43

• 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

44

• 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

45

• 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

46

• 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

47

• 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

48

• Impacts
• Ecological

• ii) Ecosystem functions
• Overview
• Specific example Ecosystem C storage
• From Jackson et al. (2002) Nature 418623-626
• Woody plant invasion into grasslands thought to
  increase amount of C stored
• If so, then woody plant invasions are good for C
  sequestration

49

• 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)

50

• 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

51

• 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

52

• 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
• (gt1 means more SOC in woody)

53

• 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

54

• 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

55

• Impacts
• Ecological

• ii) Ecosystem functions
• Overview
• Specific example Soil N change
• From Vitousek Walker (1989) Ecological
  Monographs 59247-265
• 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

56

• 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 gt10
  years
• UB Upper Byron kept free of Myrica

gt
?
?
gt
57

• 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

gt
?
?
gt
58

• Impacts
• Ecological

• ii) Ecosystem functions
• Overview
• Specific examples Fire effects
• From DAntonio in Mooney Hobbs (2002)
• Compiled 20 examples from around the world where
  invaders have altered fire regimes

59

• Impacts
• Ecological

• ii) Ecosystem functions
• Overview
• Specific examples Fire effects
• From DAntonio 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)

60

• Impacts
• Ecological

• ii) Ecosystem functions
• Overview
• Specific examples Fire effects
• From DAntonio 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)

61

• Impacts
• Ecological

• ii) Ecosystem functions
• Overview
• Specific examples Fire effects
• From DAntonio 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

62

• Impacts
• Ecological

• ii) Ecosystem functions
• Overview
• Specific examples Fire effects
• From DAntonio 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)

63

• Impacts
• Ecological

• ii) Ecosystem functions
• Overview
• Specific examples General compilation
• From Crooks (2002)

64

• 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)

65

• Impacts
• Ecological

• iii) Threatened endangered species
• Overview
• 400 of 958 federally listed species (42) are
  because of invasives (includes plants plus other
  organisms)

66

• 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

67

• 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

68

• 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)

69

• 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)

70

• Impacts
• Ecological

• iii) Threatened endangered species
• Overview
• Specific examples Hawaii
• 80-90 native plant species extinct
• 270 plant species listed as threatened or
  endangered

71

• 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

72

• 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)

73

• 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)

74

• 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)