Effects of warming and altered precipitation on plant and nutrient dynamics of a New England salt marsh.

Salt marsh structure and function, and consequently ability to support a range of species and to provide ecosystem services, may be affected by climate change. To better understand how salt marshes will respond to warming and associated shifts in precipitation, we conducted a manipulative experiment in a tidal salt marsh in Massachusetts, USA. We exposed two plant communities (one dominated by Spartina patens-Distichlis spicata and one dominated by short form Spartina alternifora) to five climate manipulations: warming via passive open-topped chambers, doubled precipitation, warming and doubled precipitation, extreme drought via rainout shelter, and ambient conditions. Modest daytime warming increased total aboveground biomass of the S. alterniflora community (24%), but not the S. patens-D. spicata community. Warming also increased maximum stem heights of S. alterniflora (8%), S. patens (8%), and D. spicata (15%). Decomposition was marginally accelerated by warming in the S. alternifora community. Drought markedly increased total biomass of the S. alterniflora community (53%) and live S. patens (69%), perhaps by alleviating waterlogging of sediments. Decomposition was accelerated by increased precipitation and slowed by drought, particularly in the S. patens-D. spicata community. Flowering phenology responded minimally to the treatments, and pore water salinity, sulfide, ammonium, and phosphate concentrations showed no treatment effects in either plant community. Our results suggest that these salt marsh communities may be resilient to modest amounts of warming and large changes in precipitation. If production increases under climate change, marshes will have a greater ability to keep pace with sea-level rise, although an increase in decomposition could offset this. As long as marshes are not inundated by flooding due to sea-level rise, increases in aboveground biomass and stem heights suggest that marshes may continue to export carbon and nutrients to coastal waters and may be able to increase their carbon storage capability by increasing plant growth under future climate conditions.

[1]  P. Hanson,et al.  A six-year study of sapling and large-tree growth and mortality responses to natural and induced variability in precipitation and throughfall. , 2001, Tree physiology.

[2]  H. L. Miller,et al.  Climate Change 2007: The Physical Science Basis , 2007 .

[3]  S. K. Allison.  The influence of rainfall variability on the species composition of a northern California salt marsh plant assemblage , 1992, Vegetatio.

[4]  R. Thunell,et al.  Modelling river discharge and precipitation from estuarine salinity in the northern Chesapeake Bay: application to Holocene palaeoclimate , 2006 .

[5]  C. S. Milan,et al.  Below-ground biomass in healthy and impaired salt marshes , 2004, Ecological Research.

[6]  David G. Williams,et al.  The influence of soil texture and vegetation on soil moisture under rainout shelters in a semi-desert grassland , 2005 .

[7]  G. Henry,et al.  Open‐top designs for manipulating field temperature in high‐latitude ecosystems , 1997 .

[8]  W. Parton,et al.  Ecosystem Responses to Warming and Interacting Global Change Factors , 2007 .

[9]  B. Drake,et al.  Seventeen years of elevated CO2 exposure in a Chesapeake Bay Wetland: sustained but contrasting responses of plant growth and CO2 uptake , 2005 .

[10]  T. E. Minchinton.  Precipitation during El Niño correlates with increasing spread of Phragmites australis in New England, USA, coastal marshes , 2002 .

[11]  A. Austin,et al.  Plant litter decomposition in a semi-arid ecosystem controlled by photodegradation , 2006, Nature.

[12]  Joel D. Cline,et al.  SPECTROPHOTOMETRIC DETERMINATION OF HYDROGEN SULFIDE IN NATURAL WATERS1 , 1969 .

[13]  F. Chapin,et al.  Decomposition of litter produced under elevated CO2: Dependence on plant species and nutrient supply , 1997 .

[14]  L. Leonard,et al.  The effect of standing biomass on flow velocity and turbulence in Spartina alterniflora canopies , 2006 .

[15]  Betsy Haskin,et al.  A 5‐yr Record of Aerial Primary Production and Stand Characteristics of Spartina Alterniflora , 1990 .

[16]  Anne F. Lightbody,et al.  Prediction of velocity profiles and longitudinal dispersion in salt marsh vegetation , 2006 .

[17]  E. Davidson,et al.  Effects of an experimental drought on soil emissions of carbon dioxide, methane, nitrous oxide, and nitric oxide in a moist tropical forest , 2004 .

[18]  F. Chapin,et al.  Global Warming and Terrestrial Ecosystems: A Conceptual Framework for Analysis , 2000 .

[19]  J. Varekamp,et al.  Relative sea‐level rise and climate change over the last 1500 years , 1992 .

[20]  I. Mendelssohn,et al.  The influence of vegetation, salinity, and inundation on seed banks of oligohaline coastal marshes , 1996 .

[21]  J. Teal.  Energy Flow in the Salt Marsh Ecosystem of Georgia , 1962 .

[22]  P. V. Sundareshwar,et al.  RESPONSES OF COASTAL WETLANDS TO RISING SEA LEVEL , 2002 .

[23]  J. Nestler.  Interstitial salinity as a cause of ecophenic variation in Spartina alterniflora , 1977 .

[24]  Alfred C. Redfield,et al.  Development of a New England Salt Marsh , 1972 .

[25]  J. Zedler,et al.  Variable rainfall limits the germination of upper intertidal marsh plants in Southern California , 2001 .

[26]  R. Delaune,et al.  Marsh vertical accretion via vegetative growth , 2006 .

[27]  Carlos M. Duarte,et al.  The fate of marine autotrophic production , 1996 .

[28]  R. Delaune,et al.  Subsidence. accretion. and sea level rise in south San Francisco Bay marshes , 1990 .

[29]  J. Teal,et al.  Production and Dynamics of Salt Marsh Vegetation and the Effects of Experimental Treatment with Sewage Sludge. Biomass, Production and Speies Composition , 1975 .

[30]  H. Mooney,et al.  Shifting plant phenology in response to global change. , 2007, Trends in ecology & evolution.

[31]  Corinne Le Quéré,et al.  Climate Change 2013: The Physical Science Basis , 2013 .

[32]  E. Davidson,et al.  Effects of an experimental drought on soil emissions of carbon dioxide, methane, nitrous oxide, and nitric oxide in a moist tropical forest , 2004 .

[33]  A. Giblin,et al.  Biogeochemical effects of seawater restoration to diked salt marshes , 1997 .

[34]  B. Anderson,et al.  Past and future changes in climate and hydrological indicators in the US Northeast , 2007 .

[35]  B. L. Howes,et al.  Nitrogen incorporation into decomposing litter of Spartina alterniflora , 1994 .

[36]  Mark D. Bertness,et al.  Latitudinal and climate-driven variation in the strength and nature of biological interactions in New England salt marshes , 2002, Oecologia.

[37]  R. Emson.  The Ecology of Atlantic Shorelines. , 2000 .

[38]  R. Howarth,et al.  Sulfate reduction in a New England salt marsh1 , 1979 .

[39]  R. Torres,et al.  Rainfall effects on marsh sediment redistribution, North Inlet, South Carolina, USA , 2002 .

[40]  H. Nepf,et al.  Prediction of velocity profiles and longitudinal dispersion in emergent salt marsh vegetation , 2005 .

[41]  A. Gray,et al.  Climate impacts on pioneer saltmarsh plants , 2001 .

[42]  K. Dunton,et al.  Freshwater inundation effects on emergent vegetation of a hypersaline salt marsh , 2002 .

[43]  John C. Field,et al.  Climate change impacts on U.S. Coastal and Marine Ecosystems , 2002 .

[44]  P. Montagna,et al.  Decomposition ofSpartina alterniflora in different seasons and habitats of a Northern Massachusetts salt marsh, and a comparison with other Atlantic regions , 1980 .

[45]  R. Torres,et al.  Properties of intertidal marsh sediment mobilized by rainfall , 2003 .

[46]  John Sabo,et al.  Morris, W. F., and D. F. Doak. 2003. Quantitative Conservation Biology: Theory and Practice of Population Viability Analysis. Sinauer Associates, Sunderland, Massachusetts, USA , 2003 .

[47]  M. Bertness,et al.  Anthropogenic modification of New England salt marsh landscapes , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[48]  J. Teal,et al.  Decomposition in salt marsh ecosystems: The phases and major factors affecting disappearance of above-ground organic matter , 1985 .

[49]  M. Loebl,et al.  Is spread of the neophyte Spartina anglica recently enhanced by increasing temperatures? , 2006, Aquatic Ecology.

[50]  J. L. Gallagher,et al.  Morphological and physiological responses to increased salinity in marsh and dune ecotypes ofSporobolus virginicus (L.) Kunth , 1991, Oecologia.

[51]  I. Anderson,et al.  Effects of sea level induced disturbances on high salt marsh metabolism , 2001 .

[52]  A. Lee Foote,et al.  Decomposition of saltmeadow cordgrass (Spartina patens) in Louisiana coastal marshes , 1997 .

[53]  R. Callaway,et al.  Effects of variable precipitation on the structure and diversity of a California salt marsh community , 1994 .

[54]  R. Wiegert,et al.  Carbon balance in a salt marsh: Interactions of diffusive export, tidal deposition and rainfall-caused erosion , 1985 .

[55]  G. Chmura,et al.  Controls on salt marsh accretion: A test in salt marshes of Eastern Canada , 2004 .

[56]  C. Gregory Knight,et al.  The potential impacts of climate change on the mid-Atlantic coastal region , 2000 .

[57]  M. Rabenhorst,et al.  Modeling of Carbon Sequestration in Coastal Marsh Soils , 2004 .

[58]  J. Donnelly.  A Revised Late Holocene Sea-Level Record for Northern Massachusetts, USA , 2006 .

[59]  T. Whitledge,et al.  Response of estuarine marsh vegetation to interannual variations in precipitation , 2001 .

[60]  Mark E. Harmon,et al.  Global-Scale Similarities in Nitrogen Release Patterns During Long-Term Decomposition , 2007, Science.

[61]  M. Bertness,et al.  Rapid shoreward encroachment of salt marsh cordgrass in response to accelerated sea-level rise , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[62]  W. Niering,et al.  Vegetation Change on a Northeast Tidal Marsh: Interaction of Sea‐Level Rise and Marsh Accretion , 1993 .