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 herbUrtica 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 12:1434-1444 • 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 scalespecies 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 scalespecies 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 scalespecies 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 scalespecies 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 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

20. 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

21. 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%)

22. 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%)

23. 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%)

24. 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)

25. 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

26. 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

27. 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?

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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

36. 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

37. 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

38. 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

39. 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

40. 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

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 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

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