Year Established: 2014 Start Date: 2014-03-01 End Date: 2015-02-28
Total Federal Funds: $33,227 Total Non-Federal Funds: $67,927
Principal Investigators: Andrew Baldwin, Stephanie Yarwood
Abstract: Problem: Spread of the non-native lineage of Phragmites australis (common reed) in wetlands is of major concern and the subject of costly management efforts in Maryland and across the U.S. east coast. However, there is a native lineage of Phragmites that most managers and landowners are unaware of that could be valuable in restored and water treatment wetlands. Nitrogen (N) availability likely plays a key role in the growth and competitive performance of both lineages, but underlying mechanisms are not understood. Native Phragmites tends to produce more lateral roots and may support more arbuscular mycorrhizal (AM) fungi than invasive Phragmites, suggesting that it is a superior competitor under low-nutrient conditions. Excess N, on the other hand, promotes aboveground growth of invasive Phragmites, allowing it to shade out other species and form dense monocultures. Localized N-limiting conditions might be created in marsh soils by adding a carbon (C) source (e.g. wood shavings or sawdust) to increase N immobilization by microbes and promote growth of plants adapted to low-nutrient conditions, a technique successfully applied in other ecosystems. Increasing the carbon-to-nitrogen (C:N) ratio of soils via C addition could give native Phragmites and other species a competitive advantage over invasive Phragmites, but to our knowledge no one has tried this approach. Objectives: Obj. 1: Under controlled greenhouse conditions, examine the effects of experimental C:N ratio treatments on aboveground and belowground growth, ecophysiology, and competitive performance of native and invasive Phragmites planted in soil from restored and natural wetlands. Obj. 2: Quantify AM fungi colonization of roots of native and invasive Phragmites. Obj. 3: Determine N and C mineralization rates in soils from restored and natural wetlands subjected to soil C:N ratio treatments. Methods: Obj.1: In a 14-wk greenhouse experiment, native and invasive Phragmites will be planted in soils from restored and natural tidal freshwater marshes and subjected to three C:N ratio manipulations: increased, decreased, or unaltered C:N ratio (4 replicates per treatment per soil type). Soils will be amended with wood shavings to increase C:N ratio or urea fertilizer (46% N) to decrease C:N ratio. Plantlets propagated from genetically confirmed native and invasive Phragmites plants will be planted in mixture and monoculture so that competition effects can be detected. Measurements will be made of biomass allocation, morphology, physiology, and tissue C and N composition, parameters related to aboveground and belowground competition for resources (light and nutrients, respectively). Obj. 2. Abundance and composition of AM fungi will be determined on lateral roots using microscopy and DNA extraction and analysis. Obj. 3. Soil incubations will be used to confirm that C and N amendments changed mineralization rates, determined via measurements of ammonium, nitrate, carbon dioxide, and methane over time. Statistical testing of hypotheses will be performed using ANOVA and multivariate techniques. Benefits: Research findings could lead to (1) adoption of C:N manipulations for management of invasive Phragmites and (2) use of native Phragmites in restoration projects and water treatment wetlands. The project would also support entry of a new research scientist (co-PI Yarwood) into the water resources field and training and education of undergraduate and graduate students. In addition to dissemination of results via scientific presentations and journal articles, findings will be communicated to pesticide applicators, environmental managers, restorationists, and the general public via outreach materials, workshops, and management conferences supported by a recently funded research-extension project.