Impacts of Invasions • Measuring impact is complex – What should be measured and how? − For individual plant, individual species, or multiple species? − Over what time frame? − Lack of comprehensive data
Feb 25, 2016
Impacts of Invasions
• Measuring impact is complex– What should be measured and how?
−For individual plant, individual species, or multiple species?
− Over what time frame?
− Lack of comprehensive data
Impacts of Invasions
• Ecology– Species replacement – Ecosystem functions – Threatened & endangered species
• Economic– Total environmental damage estimates
• Social – Water quantity and quality – Human health
Conceptual model: Walker & Smith in Lukens & Thieret (1997)• Invasive species affect different community &
ecosystem processes
Ecological Impacts
Ecological Impacts
• Types of impacts (Parker et al. 1999)– Impacts on ecosystem properties– Impacts on community structure– Impacts on individual species
Ecological Impacts• Impacts on ecosystem properties
1. Disturbance regimes
D’Antonio in Mooney & Hobbs (2002)
Ecological Impacts• Impacts on ecosystem properties
2. Resource dynamics
Ehrenfeld (2003) Ecosystems 6: 503-523
Question: How is N cycling affected by exotic grass invasion?
Method: Examined rates of N mineralization & nitrification, and characterized soil microbial communities
Ecological Impacts: Nitrogen
Hawkes et al. (2005) Ecology Letters 8:976-985
Hawkes et al. (2005) Ecology Letters 8:976-985
Ehrenfeld (2003) Ecosystems 6: 503-523
Ecological Impacts: Carbon
Woody plant invasion into grasslands is thought to increase amount of C stored
Question: Does woody plant invasion increase C sequestration?
Method: Examined 6 sites along precipitation gradient
Ecological Impacts: Carbon
Jackson et al. (2002) Nature 418:623-626
Jackson et al. (2002) Nature 418:623-626
Jackson et al. (2002) Nature 418:623-626
Ehrenfeld (2003) Ecosystems 6: 503-523
Ladenburger et al. (2005) J. of Arid Env 65: 111-128.
Tamarix ramosissima
Kulmatiski et al. (2006) Plant & Soil 288: 271-284
Question: Does plant invasion shift timing of water use?
Method: Used stable isotope ratios in soil and plant tissue
Ecological Impacts: Water
Ecological ImpactsEcosystem engineers: species able to physically alter habitats (Crooks 2002)
•Alter ecosystem physical processes (sedimentation, water availability, N cycling)
•Change habitat structure (more or less complexity)
•Effects cascade through community
Crooks (2002) OIKOS 97: 153-166
Ecosystem Impacts: Transformers
• Question: What is the long-term impact of C. pubescence invasion on Galapagos vegetation?
• Methods: Monitoring permanent plots over 7 years
Jager et al (2009) J of Ecology 97:1252-1263
Jager et al (2009) J of Ecology 97:1252-1263
Jager et al (2009) J of Ecology 97:1252-1263