Post on 20-Jan-2016
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.
3) Impactsa) Ecological
ii) Ecosystem functionsEcosystem engineers: What are they?
3) Impactsa) Ecological
ii) Ecosystem functionsEcosystem engineers: What are they?
• Alter ecosystem physical processes (water use, N cycling)
• Change habitat structure (more complexity, less complexity)
• Effects cascade through community
3) Impactsa) Ecological
ii) Ecosystem functions• Overview• Specific examples: General compilation
From Crooks (2002)
Modified from D’Antonio and Hobbie in Sax et al. 2005
Invasive plants
Altered litter quality
Altered microbial activity
Altered root exudation
N fixation
Altered microclimate
Altered microbial community
Altered NPP
Altered timing of uptake
N loss
Fire
Altered composition
N cycling and pools
Effects on Nitrogen
3) Impactsa) Ecological
iii) Threatened & endangered species• Overview
~409 animals and 598 plants are federally listed species in US
3) Impactsa) 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)
3) Impactsa) Ecological
iii) Threatened & endangered species • Overview
Effects can be by:Direct species replacementIndirect through effects on community structure or function
3) Impactsa) Ecological
iii) Threatened & endangered species : IUCN database • Overview
Effects can be by:Direct species replacementIndirect through effects on community structure or function
WorldwideExtinctions: 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
3) Impactsa) 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 seedlong growing seasontolerates heavy grazingfair forage qualityforms dense sod in mature pastures
3) Impactsa) 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 speciesSeeded extensively (for example, ~2 million acres in western
OK)
3) Impactsa) 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 speciesSeeded extensivelyBut extremely invasive:
Spread along highways into native areas (cemetaries, native grasslands)
Difficult to controlThreatens federally listed endangered plant Ambrosia
cheiranthefolia (south Texas ambrosia)
3) Impactsa) Ecological
iii) Threatened & endangered species• Overview• Specific examples: Hawaii
80-90 native plant species extinct270 plant species listed as threatened or endangered94 noxious weeds, many more alien species
3) Impactsa) 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)
3) Impactsa) 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)
3) Impactsa) 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)
3) Impactsa) 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
3) Impactsa) 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 selectedWidespreadRapid dispersalHigh variabilityGeneralistHuman commensalism
Traits of ‘losers’K selectedRareSlow dispersalLow variabilityspecialistMaladapted to humans
3) Impactsa) Ecological
Summary• Only a small percentage (0.1%) of introduced plants become a
problem
3) Impactsa) 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
3) Impactsa) 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)
3) Impactsa) 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)
3) Impactsa) 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
3) Impactsa) 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 changeEspecially on islandsEspecially rare/specialized speciesMore evidence for population reduction than for extinction (e.g.
Harrison et al 2006)