Grantee Research Project Results
Final Report: Elevated Temperature and Land Use Flood Frequency Alteration Effects on Rates of Invasive and Native Species Interactions in Freshwater Floodplain Wetlands
EPA Grant Number: R833837Title: Elevated Temperature and Land Use Flood Frequency Alteration Effects on Rates of Invasive and Native Species Interactions in Freshwater Floodplain Wetlands
Investigators: Richardson, Curtis J. , Flanagan, Neal , Ho, Mengchi
Institution: Duke University , Nicholas School of the Environment and Earth Sciences
EPA Project Officer: Packard, Benjamin H
Project Period: April 1, 2008 through March 31, 2011 (Extended to March 31, 2012)
Project Amount: $598,107
RFA: Ecological Impacts from the Interactions of Climate Change, Land Use Change and Invasive Species: A Joint Research Solicitation - EPA, USDA (2007) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Aquatic Ecosystems , Climate Change
Objective:
The primary objective of this study is to assess how predicted climate and land use driven changes in hydrologic flux and temperature regimes of floodplain ecosystems affect plant communities in terms of their vulnerability to the establishment and spread of invasive species, and in turn ecosystem functions and services. Future climate scenarios for the southeastern United Staes predict that surface water temperatures will warm (in concert with air temperature) and that stream flows will likely decrease, with a greater proportion of annual watershed hydrologic yield occurring during major storm events (IPCC 2001, Alcamo et al. 2003, Millennium Ecosystem Assessment 2005, Webster et al. 2005). Land use changes (urban vs. forested etc.) have been shown to also raise water temperature and increased pulsed water releases during storms (LeBlanc et al. 1997; Walsh 2000; Hester and Doyle 2011). We analyzed a series of riparian wetland sites along existing gradients of temperature and hydrology produced on dammed and undammed rivers to find the relative importance of a suite of environmental variables describing temperature, hydrology, soil characteristics, and watershed land use composition.
Summary/Accomplishments (Outputs/Outcomes):
Our results indicate the invasibility of riparian plant communities is driven by a combination of factors that determine the success or failure of invasive species establishment—most notably hydrology and temperature. A major objective of this study was to examine the environmental variables that are likely to be altered in future climate change scenarios and to relate these variables to our indicators of diversity and productivity at our sites. We found significant linear relationships between accumulated heat as measured by soil growing degree days (SGDD) and various facets of hydrology (flood power, duration, depth, frequency) and all of our diversity indicators (Shannon diversity, species richness, invasive abundance, and invasive biomass) indicating temperature is a significant driver of community composition at our sites. To assess the predictive power of the environmental variables that we monitored in this study, we developed a series of multivariate models that rank the importance of environmental forcing functions in structuring emergent plant communities. We consistently found the most important environmental predictors of our community indices were those that described aspects of temperature and hydrology with variables describing local soils and watershed land use characteristic typically being less important. Relationships between temperature and species richness have been studied since the founding of ecology as a discipline (Merriam 1894). The relationships between species richness and temperature we see in our study (Figures 1 and 2) are consistent with those seen in classic studies of biogeography where links are found between species and latitude. In recent years, researchers are seeing indications of latitudinal shifts of species distribution in response to climate change (Allen et al. 2002; Walther et al. 2002; Parmesan 2003; Clarke and Gaston 2006). The diversity-temperature trends observed in our study echo the diversity latitude trends seen in many studies of global scale biogeography (where higher latitude is equated with lower temperature). The richness of naturalized alien species decreased as one moves the mid-latitude temperate zone to sub-tropical and finally tropical zone (Holdgate 1986; Sax 2001; Pyšek and Richardson 2006).
Figure 1. The importance of independent variables in explaining measures of site
alphy diversity including: a) Species richness (Psudeo-R2 = 51.26), b) Shannon
(Psudeo-R2 = 41.94), c) Percent invasive by count (Psudeo-R2 = 62.94). Importance
values are produced by procegure Random Forest.
At regional and global scales, Shannon diversity is strongly correlated with the number of species (Gentry 1988). This trend is opposite to the observed tendency for overall community species richness where the highest species richness is found in the tropics and decreases as one moves toward the poles (Fischer 1960; Pianka 1966; Stevens 1989).
Future climate scenarios predict alterations of both temperate and hydrology in southeastern riparian plant communities (IPCC, 2001). We found that environmental factors consistently explained half of the variation seen in plant community structure seen at our sites, and variables related to temperature and hydrology were consistently the most important predictor of community composition and diversity.
The invasive species most dominant at our sites are those that originate at high latitudes and are able to tolerate a wide range of climatic conditions. It is likely that the propagules of these species originate in the cooler conditions found in the mountainous headwaters of our study rivers. Thus, the invasive species at our study locations appeared to have a greater competitive advantage at our cold sites most likely due to their broader ecological temperature tolerance.
Agricultural land use was also a significant predictor of community composition at our sites (“Ag” in Figure 2). Thuiller (2007) found that land use and climate change were the most important drivers affecting biodiversity. Thus, management of land use may be a potential tool for mitigating the effects of climate change on hydrology and the sources of invasive species propagules (Miyawaki 2004). In addition, management of watershed land use may be an important tool to offset future increases in water temperature due to shading and effects on temperature, runoff during storms, and groundwater interactions in riparian zones (LeBlanc et al. 1997; Hester and Doyle 2011).
Figure 2. RDA ordination of site community similarity by treatment
(Warm, Cold and Reference) and zone (Emergent and Riparian).
Degrees of correlation of environmental variables with the axes
shown as vectors whose relative correlations wiht species space are
expressed by length (2008, 2009, 2010 community data). The sizes
of site symbols are scaled by relative species richness. POWER
(flood power) AGDO (Soil Growing Degree Days), AREA (watershed
Area), Ag (watershed proportion cultivated), FREQ (flood frequency),
DEPTH (flood depth), DUR (flood duration, CTP (soil total P).
The importance of hydrologic variables in our study suggests the importance of managing climate-linked alterations of riparian hydroperiod as a tool to mitigate the impact of invasive species on riparian communities. Duration of inundation (DUR) was the most import factor in our model of species richness (Figure 1a), likely due to the relationship between drawdown and seed germination. It is likely that larger storms and extreme flood events will increase the spatial extent of hydrochory on floodplains and cause greater physical disturbance of existing plant communities, thus increasing the likelihood that invasive species will become established (Diez et al. 2012).
Conclusions:
Our study indicates that both the direct effects of temperature and the indirect effects of hydrology are potential drivers of community response to climate change. There is some reason to believe that warmer water temperatures predicted in future climate scenarios may actually favor the native communities at our sites (Bradley et al. 2009). However, it seems likely that the lower dominance of invasive species at our warm sites is related to propagule dispersion as much as temperature. Hydrology on the other hand appears as a primary driver of community structure in every analysis we performed, and climate-induced changes in future hydrology (higher peak flows and lower base flows) are likely to increase the invasibility of southeastern riparian ecosystems.
References:
Alcamo , J., Döll, P., Henrichs, T., Kaspar, F., Lehner, B., Rösch, T. & Siebert, S. (2003) Development and testing of the WaterGAP 2 model of global water use and availability. Hydrol. Sci. J. 48 (3):317-337.
Allen, A. P., J. H. Brown, et al. (2002). "Global Biodiversity, Biochemical Kinetics, and the Energetic-‐ Equivalence Rule." Science 297(5586): 1545-1548.
Bradley, B. A., M. Oppenheimer, et al. (2009). "Climate change and plant invasions: restoration opportunities ahead?" Global Change Biology 15(6): 1511-1521.
Clarke, A. and K. J. Gaston (2006). "Climate, energy and diversity." Proceedings of the Royal Society B: Biological Sciences 273(1599): 2257-2266.
Diez, J. M., C. M. D'Antonio, et al. (2012). "Will extreme climatic events facilitate biological invasions?" Frontiers in Ecology and the Environment 10(5): 249-257.
Fischer, A. G. (1960). "Latitudinal variations in organic diversity." Evolution 14: 64-81.
Gentry, A. H. (1988). "Changes in Plant Community Diversity and Floristic Composition on Environmental and Geographical Gradients." Annals of the Missouri Botanical Garden 75(1): 1-34.
Hester, E. T. and M. W. Doyle (2011). "Human Impacts to River Temperature and Their Effects on Biological Processes: A Quantitative Synthesis1." JAWRA Journal of the American Water Resources Association 47(3): 571-587.
Holdgate, M. W. (1986). "Summary and Conclusions: Characteristics and Consequences of Biological Invasions." Philosophical Transactions of the Royal Society of London. B, Biological Sciences 314(1167): 733-742.
IPCC (2001). Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change [Houghton, J.T.,Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. Johnson (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 881pp.
LeBlanc, R. T., R. D. Brown, et al. (1997). "Modeling the Effects of Land Use Change on the Water Temperature in Unregulated Urban Streams." Journal of Environmental Management 49(4): 445-469.
Merriam, C. H. (1894). "Laws of temperature control of the geographic distribution of terrestrial animals and plants". Millennium Ecosystem Assessment (2005). Ecosystems and Human Well-being: Synthesis. Island Press, Washington, DC.
Miyawaki, S. (2004). "Invasive alien plant species in riparian areas of Japan : the contribution of agricultural weeds, revegetation species and aquacultural species." Global Environ. Res. 8: 89-101.
Parmesan, C. G. (2003). "A globally coherent fingerprint of climate change impacts across natural systems." Nature 421(6918): 37.
Pianka, E. R. (1966). "Latitudinal gradients in species diversity: a review of concepts." Am. Nat. 100: 33-46.
Pyšek, P. and D. M. Richardson (2006). "The biogeography of naturalization in alien plants." Journal of Biogeography 33(12): 2040-2050.
Sax, D. F. (2001). "Latitudinal Gradients and Geographic Ranges of Exotic Species: Implications for Biogeography." Journal of Biogeography 28(1): 139-150.
Stevens, G. C. (1989). "The Latitudinal Gradient in Geographical Range: How so Many Species Coexist in the Tropics." The American Naturalist 133(2): 240-256.
Thuiller, W. (2007). "Biodiversity: Climate change and the ecologist." Nature 448(7153): 550-552.
Walther, G.-R., P. Eric, et al. (2002). "Ecological responses to recent climate change." Nature 416(6879): 389.
Walsh, C. J. (2000). Urban impacts on the ecology of receiving waters: a framework for assessment, conservation and restoration. Hydrobiologia 431: 107-114.
Webster P.J., G.J. Holland, J.A. Curry, and H.R. Chang. (2005). Changes in tropical cyclone number, duration, and intensity in a warming environment. Science 309:1844-1846.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 9 publications | 2 publications in selected types | All 2 journal articles |
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Type | Citation | ||
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Flanagan NE, Richardson CJ, Ho M. Connecting differential responses of native and invasive riparian plants to climate change and environmental alteration. Ecological Applications 2015;25(3):753-767. |
R833837 (Final) |
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Ho M, Richardson CJ. A five year study of floristic succession in a restored urban wetland. Ecological Engineering 2013;61(Part B):511-518. |
R833837 (Final) |
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Supplemental Keywords:
RFA, Scientific Discipline, Air, Ecosystem Protection/Environmental Exposure & Risk, Hydrology, climate change, Air Pollution Effects, Monitoring/Modeling, Regional/Scaling, Environmental Monitoring, Atmospheric Sciences, Ecological Risk Assessment, Atmosphere, coastal ecosystem, biodiversity, environmental measurement, ecosystem assessment, meteorology, global change, anthropogenic, climate models, UV radiation, greenhouse gases, environmental stress, coastal ecosystems, water quality, habitat diversity, invasive species, ecological models, climate model, Global Climate Change, land use, regional anthropogenic stresses, atmospheric chemistry, stressor response model, climate variabilityRelevant Websites:
Duke University Wetland Center website Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.