A landscape-scale approach to management of a major invasive species, Phragmites australis, in Chesapeake Bay tidal wetlands Dennis Whigham1, Eric Hazelton1,2, Melissa McCormick1, and Karin Kettenring1,2 1Smithsonian Environmental Research Center 2Utah State University Saltonstall. 2002. PNAS 99: 2445-2449 Rhode River 1970 Rhode River 2009 A fundamental question in ecology What drives the (rapid) spread of invasive species? Characteristics Characteristics of environment of invader Subestuaries of Chesapeake Bay studied as part of EPA-funded Atlantic Slope Consortium project Jones Falls Back Gwynns Falls Bird Patapsco Langford Curtis Southeast Magothy Corsica Severn South Wye Rhode Miles Tred Avon Battle King, R.S., W.V. Deluca, D.F. Whigham, Wicomico St. Clements St. Leonards and P.P. Marra. 2007. Threshold effects of Mill C coastal urbanization on Phragmites Breton h Manokin St. Mary's e australis (Common Reed) abundance and s Nomini a foliar nitrogen in Chesapeake Bay. p e Totuskey a Estuaries and Coasts 30: 469-481. k e Piankatank B a y Ware LANDUSE Agricultural Developed Warwick Forested Pagan Mixed-Ag Mixed-Dev Elizabeth . Kilometers 0 12.5 25 50 75 100 Have environmental factors driven the spread of Phragmites in recent years? Phragmites seedling emergence higher in disturbances (p<0.001) in some plant communities (p<0.001). Rhizome emergence was low and not related to disturbances control 40 aboveground disturbance belowground disturbance b b b b 30 b ab 20 (mean ± 1 SE)±1 (mean a a % seedling emergence seedling % 10 a a a a 0 Iva Schoenoplectus Spartina/Distichlis Typha Phragmites seedlings (but not rhizomes) growth higher under elevated nitrogen (p=0.003) and plants were taller and produced more stems 2.5 c 0 g m-2 yr-1 bc 9 g m-2 yr-1 18 g m-2 yr-1 2.0 bc 35 g m-2 yr-1 70 g m-2 yr-1 1.5 ab 1.0 a Total biomass (mean ± 1 SE)±1 (mean Total biomass 0.5 0.0 More florets (p=0.006) and inflorescences (p<0.001) are produced per plant with elevated nutrients 4000 ambient nutrients elevated nutrients 3000 2000 (mean ± 1 SE)±1 (mean Number of Number florets 1000 0 14 ambient nutrients elevated nutrients 12 10 8 6 (mean ± 1 SE)±1 (mean 4 Number of Number inflorescences 2 0 Kettenring, McCormick, Baron, and Whigham, J. Appl. Ecol. 2011 CO2 + N experiment at the SERC Global Change Research Wetland Mozdzer TJ, Megonigal JP (2012) Jack-and-Master trait responses to elevated CO2 and N: A comparison of native and Introduced Phragmites australis. PLoS ONE 7(10): e42794. doi:10.1371 Have biological factors driven the spread of Phragmites in recent years? How does Phragmites reproduce and spread? Rhizomes - Clonal (asexual) propagation Shoots - Clonal (Rooting at nodes) Seeds - Sexual reproduction (outcrossing) Substantial genetic variation within and among patches: 91% of patches had >1 genotype McCormick, Kettenring, Baron, and Whigham. 2010. Wetlands # of genotypes per patch increased with watershed development 4 p=0.035 r2=0.145 1SE) 1SE) 3 + 2 1 # of genotypes per patch (of 4 possible; mean 0 Forested Mixed- Developed Developed Watershed Class McCormick, Kettenring, Baron, and Whigham J. Ecology 2011 Kettenring, McCormick, Baron, and Whigham, J. Applied Ecology Increased local genetic diversity positively related to viable seed production Seeds and leaves 2 collected R2=0.26, P=0.0003 0 -2 -4 -6 Proportion viable seeds mean) Proportion of (logit -8 -6 -5 -4 -3 -2 Bruvo genetic diversity (natural log transformed) Kettenring, McCormick, Baron, and Whigham J. Applied Ecology . 2011 Where do the seeds establishing patches on hardened shoreline come from? 1.0 Rhode River Chesapeake Bay – 9 subestuaries 0.8 +SE) +SE) 0.6 Similarity 0.4 100m 500m (meanMoran's I 0.2 0.0 0 1000 2000 3000 4000 5000 0 500 1000 50,000 Mean distance separating sample pairs (m) The majority of dispersal is local and within subestuaries McCormick, Kettenring, Baron, and Whigham Wetlands 2010, J. Ecology 2011 Conceptual Model Based on Recent Findings Feedback Current Project (Focus: three types of subestuaries) Shoreline Structures • Genetic diversity • Dispersal Phragmites Removal Experiment • Water quality • Fish and invertebrates transects • Transects • Each quadrat (n = 405): – Plant Community – Nutrients – Salinity – Phragmites vigor – Phragmites clonal diversity – Phragmites flowering density – Phragmites herbivore density – Seed bank Shoreline disturbances Shoreline hardening promotes more genetically diverse Phragmites patches 6 shoreline P=0.005 Forested watershed P<0.001 Agriculture 5 shore x w-shed P=0.335 Developed 4 se) + 3 Genotypes (mean 2 1 0 Natural Riprap* Bulkhead Shoreline Type Why are patches associated with hardened shorelines more diverse? •Wave action deferred by bulkheads may cause repeated disturbances or may concentrate dispersing seeds at the edges. •Riprap may provide places for seeds to lodge. •Areas targeted for hardening may be those with the greatest fetch and/or disturbance and so might have the most (and most diverse) Phragmites anyway. Herbicide application (glyphosate) over three years At each site • Native • Phragmites removed • Phragmites control Patapsco River (Developed) Native outlier likely Iva Removal Native Control St. Leonard River (Forested) Control Native Removal Outlier is open water Wye River (Agricultural) Native Control Removal Is there any hope that effective management can happen? Hazelton, E.L.G., Mozdzer, T.J., Burdick, D. Kettenring, K.M. and Whigham, D.F. 2014. Phragmites australis management in the United States: 40 years of methods and outcomes. AoB Plants, doi:10.1093/aobpla/plu001 Implications For Management • Without an effective management strategy, the non-native genotype potentially could occupy all brackish wetlands and, potentially, the majority of tidal freshwater wetlands •Effective long-term management can only be done at the scale of entire subestuaries (removal of primary sources of seeds) •Following removal, management can focus on periodic inspections and removal of any new invasions. •Efforts should be made to identify important subestuaries where most of the uplands are forested and few or relatively few patches of the non- native genotype occur. Complete removal and periodic inspections and follow-up are required. •Some areas (e.g., around Baltimore and Norfolk) are so heavily invaded that removal and management are too expensive. Rock Hall Patapsco St. Leonard Creek Patch History 1970 – 1 patch Mid-1990s – 1 shoreline patch (VIMS) 2013 – 12 patches Parkers Creek Battle Creek Fairhaven: Community action Jay O’Neill – Head Technician, Plant Ecology lab, SERC Matt Sievers – SERC intern Heather Baron – SERC intern. MS - Oregon State Jared Staap – SERC intern. MS University of Maine Liza McFarland – SERC intern. MS – U. Maryland Hope Brooks – SERC intern. Senior at Penn State Funding sources: EPA – STAR program NOAA – Chesapeake Bay office Smithsonian Institution Karin and Jay NOAA Smithsonian Institution Hope Melissa Heather Matt Jared Liza .