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Elizabeth Waring and A. Scott Holaday Texas Tech University

Seasonal change effects on photosynthesis, nitrogen metabolism and soil nitrogen in competing invasive Phalaris arundinacea  and native  Carex stricta. Elizabeth Waring and A. Scott Holaday Texas Tech University. Why study physiology in invasive species?. Environment. Soil Nitrogen

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Elizabeth Waring and A. Scott Holaday Texas Tech University

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  1. Seasonal change effects on photosynthesis, nitrogen metabolism and soil nitrogen in competing invasive Phalarisarundinacea and native Carexstricta Elizabeth Waring and A. Scott Holaday Texas Tech University

  2. Why study physiology in invasive species? Environment Soil Nitrogen Seasonal Changes Metabolic Adaptations Physiological Processes Growth Reproduction Performance

  3. Wetlands and Invasion • Wetlands are particularly likely to be invaded1 • Sinks in hydrological systems • Seeds and plant parts are easily dispersed by water • Nitrogen sinks • Increasing from anthropogenic changes • Phalaris arundinacea/Carex stricta model 1 Zedler and Kercher 2004

  4. Phalaris arundinacea L. • “Reed Canarygrass” • Few native populations in North America • Mostly hybrid of native European and Asian populations • Increased biomass with increased nitrogen

  5. Carex stricta Lam • “Tussock Sedge” • Native east of Great Plains • Biodiversity

  6. Research Questions • (1) Do the species differ with respect to nitrogen assimilation that affects photosynthetic processes? • (2) Is there a relationship between seasonal changes in physiological processes and available soil nitrogen?

  7. Nitrogen Assimilation Plant Soil NR NiR NH4+ NO2- NO3- NH4+ Building Amino Acids

  8. Leaf Nitrogen, Protein Content and Photosynthesis • First step of Calvin-Benson Cycle catalyzed by Rubisco • Strong relationship • Link carbon and nitrogen metabolism • Leaf N – mg/g leaf tissue – CE Elantech • Protein by Bradford Assay1 Wright et al. 2004 1 Bradford 1976

  9. Photosynthesis Ci (ppm)

  10. Soil Probes • Cation and anion • Trap moving nitrogen • In soil for 3 weeks • 4 blocks of 4 pairs per site • Analyzed in at Western Ag labs in ND

  11. Data were collected seasonally in 2012 • Leaf N from 2011 • Tissue samples collected in May, July, October

  12. Site 1 (“Phalaris site”) Phalaris dominated Some Carex species mixed Low Biodiversity

  13. Site 1 (“Phalaris site”) Phalaris dominated Some Carex species mixed Low Biodiversity

  14. Site 1 (“Phalaris site”) Phalaris dominated Some Carex species mixed Low Biodiversity

  15. Site 2 (“Carex site”) Some Phalaris on East side High Biodiversity

  16. Site 2 (“Carex site”) Some Phalaris on East side High Biodiversity

  17. Site 2 (“Carex site”) Some Phalaris on East side High Biodiversity

  18. SLA

  19. Statistical Analysis • Seasons to Julian date • Mixed Effects Linear Regression Model in R • Nested by individual (repeated measurements) • Followed by ANOVA

  20. Mixed effects model nested by individual (n=4) spp p<0.05 and dateXspp p <0.05

  21. Mixed effects model nested by individual (n=4) spp p<0.05 and dateXspp p <0.05

  22. 2011 data Mixed effects model nested by individual (n=4) spp p<0.05 and date p <0.05

  23. Mixed effects model nested by individual (n=6) Spp, date, and site p<0.05 and dateXspp p <0.0001 and dateXsppXsite p<0.05

  24. Mixed effects model nested by individual (n=6) spp p<0.005 and date p <0.0001

  25. Mixed effects model nested by individual (n=6) Site p<0.1 and date p <0.0001

  26. Nitrate: Site p<0.005 Ammonium Site p<0.05 Date p<0.005 DateXSite p<0.05

  27. Conclusions • (1) Do the species differ with respect to nitrogen assimilation that affects photosynthetic processes? • Yes. Although mostly in Carex • (2) Is there a relationship between seasonal changes in physiological processes and available soil nitrogen? • Carex No • Phalaris Possibly. Few traits varied between sites, but appears Phalaris increased dominance with increased nitrate?

  28. Future Directions • Expand sampling sites • Use proxies • Leaf N • Soil N • Protein content • >20 sites sampled in May

  29. Acknowledgements • HasithaGuvvala and Yuanhua Wang • Moore-Kucera lab • The Wetland Foundation • Department of Biological Sciences • VPR Office

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