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Vegeta&on Change: A River Runs Through It Riparian Successional Change as a Posi&ve Feedback Loop to Climate Change By Connor LewisSmith 1
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Vegeta&on Change: A River Runs Through It
Riparian Successional Change as a Posi&ve Feedback
Loop to Climate Change
By Connor Lewis-‐Smith
1
Riparian Ecosystem 2
What is the Riparian Ecosystem? • A biological feedback into
river geomorphology and hydrology
(Bendix and Hubb 2000). 3
• Riparian vegeta&on succession is an ecological feedback to climate change
CO2 Concentra&ons
Flow Regime Change
Riparian Vegeta&on
Weather PaSerns
4
Floods
WeSer winters Increased flooding
Projected to con&nue to increase in severity. 5
Projected returns of present 100 year flooding
Hirabayahi et al. 2008
6
Historic Flooding In South Carolina
“Floodwaters break through a walkway in Columbia, S.C., Monday, Oct. 5, 2015. A]er a week of steady rain, the showers tapered off Monday and an inundated South Carolina turned to surveying a road system shredded by historic flooding” (AP Photo/Chuck Burton)
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Far Reaching and Felt
• On the Skagit River (WA), the magnitude of 50-‐year-‐return flood events is projected to increase 15% by the 2040s (compared to 1916-‐2006) (Tillmann and Siemann 2011).
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Vegeta&on's Rela&onship to Floods
• flood veloci&es may be substan&ally decreased as vegeta&on grows
• or abruptly increased if the vegeta&on is destroyed (Bendix and Hubb 2000).
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• Shi] plant communi&es towards species with less ability to stabilize sediments
• More intense, destruc&ve floods
Vegeta&on's Rela&onship to Floods
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Basal Area of Three most abundant pioneer trees in semiarid riparian zone
Stromberg et al. 2010 collected data from San Pedro River basin in both wet and dry seasons Younger plants present in areas of higher intensity floods, dry sites have more exo&cs than na&ves. 11
Populus fremon-i Fremont coSonwood
(hSp://www.fireflyforest.com/flowers/2182/populus-‐fremon&i-‐fremont-‐coSonwood/)
Salix gooddingii Goodding Willow
(hSp://www.mswn.com/plants/database/plant/salix-‐gooddingii/)
Tamarix sp. Salt Cedar
(hSp://www.streamwebs.org/invasive-‐species-‐list/saltcedar-‐tamarix-‐ramosissima)
Na&ves to SW USA
Invasive to SW USA
Three Common Woody Species of the Riparian Environments in the SW USA
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Shi]s in Vegeta&on Type
Stromberg et al. 2010 13
Droughts
Drier summers Decreased flow
Projected to con&nue to increase in severity.
14
Future Drought Projec&ons
Hirabayahi et al. 2008 15
• Stream water sources threatened: – Snow pack dependent – Ground water/runoff dependent
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Perry et al. 2013 • Will posi&ve effects of climate change on riparian vegeta&on offset nega&ve effects?
• Increased CO2 (+) • Increased Water Stress (-‐)
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Perry et al. 2013 Methods • five of the most abundant western United States woody species:
• Two na&ves (Populus deltoides spp. monilifera, Salix exigua)
• Three exo&c (Elaeagnus angus-folia, Tamarix spp., Ulmus pumila).
• Grown in a CO2-‐controlled glasshouse • Different water-‐table decline rates to test the species response to drought under current and increased CO2 concentra&ons.
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Results of CO2 and Water Decline
• Elevated [CO2] increased mean total biomass by 15%
• faster water-‐table decline rates on seedling biomass (70–97%)
• Hindered na&ves more than exo&cs
Perry et al. 2013 19
Model of direct and indirect effects of climate change on flow regime
Tillmann and Siemann 2011
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• Riparian vegeta&on succession is an ecological feedback to climate change
CO2 Concentra&ons
Flow Regime Change
Riparian Vegeta&on
Weather PaSerns
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Riparian vegeta&on change is occurring, but how will it con&nue?
Modeling 22
Riparian Succession Model
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Computer Based Modeling
• Computer Aided Simula&on Model for In-‐stream Flow and Riparian vegeta&on model: CASiMiR-‐vegeta&on model
• Modeling Succession Phase vs. Site Specific Features.
• Inputs: grid-‐based topography, max. annual discharge shear stress, flood dura&on and mean/base water table eleva&on files. Rivaes et al.
2014 24
Rivaes et al. 2014
25
CASiMiR-‐Vegeta&on Model
Rivaes et al. 2014
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Feedback to Climate Change Riparian vegeta&on will sequester
less carbon
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No riparian vegeta&on to sequester carbon
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Woody Riparian Vegeta&on Stores More CO2
Data from San Pedro River Basin March-‐December (primary growing season) totals of NNE were -‐63, -‐212, and -‐233 g C m-‐2 in the grassland, shrubland, and woodland, respec&vely
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Net Ecosystem CO2 exchange based on Vegeta&on Type ScoS et al. 2006
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Riparian Vegeta&on's Power as a Sink
• Restoring and refores&ng such riparian zones to mature forest would increase carbon storage and improve water quality.
• The carbon deficit along 57,700 km headwater Coastal Plain streams in North Carolina is equivalent to – 25TgC in 30-‐m-‐wide riparian buffer zones – 50TgC in 60-‐m-‐wide buffer zones.
Rheinhardt et al. 2012 31
Biomass of Riparian Vegeta&on in North Carolina
Rheinhardt et al. 2012
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0
50
100
150
200
250
300
Mature Forest Regenera&ng Forest Perennial Herb Shrub/Sapling Annual Rowcrops
MgC/ha
CO2
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Rivers as Sources of Atmospheric CO2
• Emiqng 97 (+/-‐32) TgC per year
• Posi&vely correlated with annual precipita&on
Butman et al. 2011 34
• Riparian vegeta&on succession is an ecological feedback to climate change
CO2 Concentra&ons
Flow Regime Change
Riparian Vegeta&on
More Floods and Droughts
Stress / destruc&on
Geophysical altera&ons
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Butman, D. and P.A. Raymond. 2011. Significant efflux of carbon dioxide from streams and rivers in the United States. Nature Geoscience. 16 October 2011.
Hirabayashi, Y., Kanae, S., Emori, S., Oki, T. and M. Kimoto. 2008. Global projec&ons of changing risks of floods and droughts in a changing climate. Hydrological Sciences Journal 53(4) 754-‐772
Kernan, M. R., R. W. BaSarbee, and Brian Moss. 2010. Climate Change Impacts on Freshwater Ecosystems. Chichester, West Sussex, UK: Wiley-‐Blackwell, 2010.
Perry, L.G., Shafroth, P.B., Blumenthal, D.M., Morgan, J.A. and D.R. LeCain. 2013. Elevated CO2 does not offset greater water stress predicted under climate change for na&ve and exo&c riparian plants. Phytologist 197: 532-‐543
Rheinhardt, R.D., Brinson, M.M., Meyer, G.F. and K.H. Miller. 2012. Carbon storage of headwater riparian zones in an agricultural landscape. Carbon Balance Manag. 7:4
Stromberg, J.C., Lite, S.J. and M.D. Dixon. 2010. Effects of Stream Flow PaSerns on Riparian Vegeta&on of a Semiarid River: Implica&ons for a Changing Climate. River Research and Applica-ons. 26: 712-‐729
Tabacchi, E., Correll, D.L., Hauer, R., Pinay, G., Planly-‐Tabacchi, A.M. and R.C. Wissmar. 1998. Development, Maintenance and role of riparian vegeta&on in the river landscape. Freshwater Biology 40, 497-‐516
Tillmann, P. and D. Siemann. 2011. Climate Change Effects and Adapta&on Approaches in Freshwater Aqua&c and Riparian Ecosystems in the North Pacific Landscape Conserva&on Coopera&ve Region. Na-onal Wildlife Federa-on
Rivaes, R.P., Rodrıguez-‐Gonzalez1, P.M., Ferreira, M.T., Pinheiro, A.N., Poliq, E., Egger G., Garcıa-‐Arias A. and F. Frances. 2014. Modeling the Evolu&on of Riparian Woodlands Facing Climate Change in Three European Rivers with Contras&ng Flow Regimes. Ecohydrology Vol 9. No. 10
Bibliography
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Ques&ons?
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