Download Invasive Species Disrupt Ecosystem Processes in North America

Invasive Species Disrupt Ecosystem
Processes in North America
Jeffrey S. Dukes
Department of Forestry and Natural Resources
& Department of Biological Sciences
Invasive species and ecosystem
processes
Nutrient cycling
Disturbance
regime
Atmospheric
composition
Ecosystem process impacts
Geomorphology
Production and
decomposition
Hydrology
Invasive species and ecosystem
processes
✔
Nutrient cycling
✔
Atmospheric
composition
Disturbance
regime
Ecosystem process impacts
Geomorphology
Hydrology
✔
Production and
decomposition
Invasive species and ecosystem
processes
✔
Nutrient cycling
✔
Atmospheric
composition
Disturbance
regime
Ecosystem process impacts
Geomorphology
Hydrology
✔
Production and
decomposition
Invasive species and disturbance regimes
• Animals
– Rooting, burrowing, direct disturbance
• Plants
– Fire regime, flood regimes
Invasive animals and disturbance
• Rooting
– Feral pigs in Hawaii, California
• Burrowing
– Earthworms; Isopod in San Francisco Bay;
nutria in eastern US
• Direct disturbance
– Feral grazers, e.g., on Santa Cruz islands in
California -> erosion
Invasive plants and disturbance regimes
• Fire
– Altering fire regimes
• Invasive grasses replace shrublands in the West
– Cheatgrass, red brome, buffelgrass, others
Cheatgrass accelerates fire return interval
Balch et al. 2013 GCB
Invasive plants and disturbance regimes
• Fire
– Altering fire regimes
• Other species in the East
– Cogongrass: Holzmueller & Jose 2012, etc.
– Japanese stiltgrass: Wagner & Fraterrigo 2015
Estrada & Flory 2015
Invasive plants and disturbance regimes
• Flood regimes
– Clogging riparian corridors; intensifying floods
– Example: Arundo donax in West?
Invasive species and disturbance regimes
• Gaps / Challenges
– Plant-driven disturbances are typically rare
events; few impacts on disturbance regimes
(fire, floods) have been reliably measured
Invasive species and geomorphology
• Plants
– Invasive grasses changing dune morphology
in the West (e.g., Ammophila)
– Invasive shrubs changing geomorphology of
rivers and streams (e.g., Tamarix)
– Invasive Spartina species colonizing mud flats
in West Coast estuaries
• Note: all are in dynamic geomorphic
settings
Invasive species and geomorphology
• Gaps / challenges
– Hard to quantitatively synthesize; no common
unit of measure
– What about microbes?
Fei et al. 2014 AREES
Invasive species and hydrology
• Plants
– Tamarix, Arundo, and water use in West
– Invasive grasses, forbs and water use in
California
Invasive species and hydrology
• No clear effect across invasive species
Mean effect size of alien plants, from Vila et al. 2011
Do invader’s traits resemble natives’?
Le Maitre et al.
2015 AoB Plants
Do invader’s traits resemble natives’?
Le Maitre et al.
2015 AoB Plants
Do Tamarix invasions dry up rivers?
• Some controversy…
Do Arundo invasions dry up rivers?
• Arundo invasions in Neuces River, Texas
Jain et al. 2015 Hydrology
California, invasions, and hydrology
• Originally dominated (?) by perennial grasses
• Annual grasses altered grassland phenology
and water use patterns
• Native woody species disadvantaged
• Centaurea solstitialis has invaded many
grasslands, taking advantage of new water
availability
Gordon & Rice 1993, Holmes & Rice 1996, Dyer & Rice 1999,
Gerlach 2004, Dukes 2001, Enloe et al. 2004
Invasive species and hydrology
• Challenges / gaps
– Few studies reliably quantify impacts
– Short-term studies may not capture long-term
patterns
– How does impact scale with density of
invasion? Do thresholds exist?
Pests and pathogens!
• Invasive insects and pathogens have transformed
ecosystem processes in many regions by
removing / suppressing dominant species
– Obvious examples: Chestnut blight, hemlock woolly
adelgid, etc.
– Impacts depend on dominance, traits of affected
plants
• Animals can also affect productivity and nutrient
cycling (e.g., zebra mussels, Asian clams, probably
Asian carp)
Climate change will alter some
impacts
Hellmann et al. 2008
Climate change will alter some
impacts
Hellmann et al. 2008
Climate change will alter some
impacts
Hellmann et al. 2008
Thank you
Thanks to many unacknowledged
photographers…