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Reading assignments: ecological impacts

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Biological invasions by exotic grasses, the grass-fire cycle, and global change. ... federally listed endangered plant Ambrosia cheiranthefolia (south Texas ambrosia) ... – PowerPoint PPT presentation

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Title: Reading assignments: ecological impacts


1
Reading assignments ecological impacts
  • Invasives and fire
  • DAntonio and Vitousek 1992. Biological invasions
    by exotic grasses, the grass-fire cycle, and
    global change. Annual review of Ecology and
    Sytematics 2365-87.
  • Brooks et al. 2004. Effects of invasive alien
    plants on fire regimes. BioScience 54 677-688.
  • Ecosystem changes
  • Crooks 2002. Characterizing ecosystem-level
    consequences of biological invasions the role of
    ecosystem engineers. Oikos 97153-166.

2
  • Impacts
  • Ecological

ii) Ecosystem functions Ecosystem engineers What
are they?
3
  • Impacts
  • Ecological
  • ii) Ecosystem functions
  • Ecosystem engineers What are they?
  • Alter ecosystem physical processes (water use, N
    cycling)
  • Change habitat structure (more complexity, less
    complexity)
  • Effects cascade through community

4
  • Impacts
  • Ecological
  • ii) Ecosystem functions
  • Overview
  • Specific examples General compilation
  • From Crooks (2002)

5
Effects on Nitrogen
N loss
Invasive plants
Fire
Altered composition
Altered litter quality Altered microbial
activity Altered root exudation N fixation
Altered microclimate Altered microbial
community Altered NPP Altered timing of uptake
N cycling and pools
Modified from DAntonio and Hobbie in Sax et al.
2005
6
  • Impacts
  • Ecological
  • iii) Threatened endangered species
  • Overview
  • 409 animals and 598 plants are federally listed
    species in US

7
  • Impacts
  • Ecological
  • iii) Threatened endangered species
  • Overview
  • 409 animals and 598 plants are federally listed
    species in US
  • 294 (29) threatened by direct effects of
    invasive species (IUCN)

8
  • Impacts
  • Ecological
  • iii) Threatened endangered species
  • Overview
  • Effects can be by
  • Direct species replacement
  • Indirect through effects on community structure
    or function

9
  • Impacts
  • Ecological
  • iii) Threatened endangered species IUCN
    database
  • Overview
  • Effects can be by
  • Direct species replacement
  • Indirect through effects on community structure
    or function
  • Worldwide
  • Extinctions 104 records of extinctions directly
    due to invasives
  • 88 animals (many birds, NZ and HI)
  • 16 plants
  • Endangered and vulnerable 1317 directly due to
    invasives

10
  • 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

11
  • 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)

12
  • 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)

13
  • Impacts
  • Ecological
  • iii) Threatened endangered species
  • Overview
  • Specific examples Hawaii
  • 80-90 native plant species extinct
  • 270 plant species listed as threatened or
    endangered
  • 94 noxious weeds, many more alien species

14
  • Impacts
  • Ecological
  • iii) Threatened endangered species
  • Overview
  • Specific examples California
  • Seabloom et al (2006) examined distribution of
    834 exotic plants in CA. Multivariate analyses
    (CCA, SEM)

15
  • Impacts
  • Ecological
  • iii) Threatened endangered species
  • Overview
  • Specific examples California
  • Seabloom et al (2006) examined distribution of
    834 exotic plants in CA. Multivariate analyses
    (CCA, SEM)
  • exotic/invasive species tightly linked to
    distribution of imperiled species (regression,
    CCA)

16
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17
  • Impacts
  • Ecological
  • iii) Threatened endangered species
  • Overview
  • Specific examples California
  • Seabloom et al (2006) examined distribution of
    834 exotic plants in CA. Multivariate analyses
    (CCA, SEM)
  • exotic/invasive species tightly linked to
    distribution of imperiled species (CCA)
  • Human activities facilitate initial invasion but
    exotics spread ahead of front of human
    development into areas with high numbers of
    threatened plants (SEMs)

18
  • Impacts
  • Ecological
  • iii) Threatened endangered species
  • Not a lot of evidence for extinctions (Gurevitch
    and Padilla 2004)
  • But Winners and Losers in anthropogenic biotic
    homogenization (McKinney and Lockwood 1999)
  • Invasive plants are winners
  • losers are species whose numbers/range decline
  • Geographically restricted natives with specific
    habitat requirements high extinction rates

19
  • Impacts
  • Ecological
  • iii) Threatened endangered species
  • Not a lot of evidence for extinctions (Gurevitch
    and Padilla 2004)
  • But Winners and Losers in anthropogenic biotic
    homogenization (McKinney and Lockwood 1999)
  • Invasive plants are winners
  • losers are species whose numbers/range decline
  • Geographically restricted natives with specific
    habitat requirements high extinction rates
  • Traits of winners
  • r selected
  • Widespread
  • Rapid dispersal
  • High variability
  • Generalist
  • Human commensalism
  • Traits of losers
  • K selected
  • Rare
  • Slow dispersal
  • Low variability
  • specialist
  • Maladapted to humans

20
  • Impacts
  • Ecological
  • Summary
  • Only a small percentage (0.1) of introduced
    plants become a problem

21
  • Impacts
  • 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

22
  • Impacts
  • 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)

23
  • Impacts
  • 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)

24
  • Impacts
  • 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)
  • Loss of native species (threatened or endangered
    species)
  • Often in conjunction with human-caused habitat
    change

25
  • Impacts
  • 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)
  • Loss of native species (threatened or endangered
    species)
  • Often in conjunction with human-caused habitat
    change
  • Especially on islands
  • Especially rare/specialized species
  • More evidence for population reduction than for
    extinction (e.g. Harrison et al 2006)
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