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Reading assignments: ecological impacts

Reading assignments: ecological impacts. Invasives and fire: D’Antonio and Vitousek 1992. Biological invasions by exotic grasses, the grass-fire cycle, and global change. Annual review of Ecology and Sytematics 23: 65-87 .

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Reading assignments: ecological impacts

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  1. Reading assignments: ecological impacts • Invasives and fire: • D’Antonio and Vitousek 1992. Biological invasions by exotic grasses, the grass-fire cycle, and global change. Annual review of Ecology and Sytematics 23:65-87. • 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 97:153-166.

  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 D’Antonio 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. 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)

  17. 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

  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 • 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

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

  20. 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

  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 • Effects observed as: • Species replacements (direct/individual or large scale, w/ or w/o interactions with other factors such as fire)

  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) • Ecosystem functions (C sequestration, N fixation, fire frequency/intensity)

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

  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 • 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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