PIE+LTER+ Coupled watershed (600 km 2 ) and estuarine system (60 km 2 - PDF document

Understanding+and+measuring+of+ accre1on+processes+in+1dal+salt+ marshes+ Inke+Forbrich+ The+Ecosystems+Center+ Marine+Biological+Laboratory+ PIE+LTER+ Coupled watershed (600 km 2 ) and estuarine system (60 km 2 ) Watershed – 38% urban + 45% forest Estuary – macrotidal (3m), salt marsh dominated

Sea+level+rise+ Fig.:+Rohde+(2006),+PraveLoni+(2009)+ Accre1on+processes+ Plant&Biomass:& • Trap+sediment+ • Grow+roots+&+rhizomes+++ + Marshes maintain equilibrium with sea level by trapping sediment and building soil organic matter (MEM III by Jim Morris, USC).

Marsh+Equilibrium+model+ Aboveground+ Biomass+ Depth+Below+MHW+ Mean high water MARSH PLATFORM Elevation MSL S. alterniflora Mean low water Morris+et+al.+(2002)+ Surface+Eleva1on+Table+(SET)+ Law's SET Cumulative change averages 4.50 4.00 Law's Point 2 alterniflora 3.50 Law's Point 3 patens 3.00 2.50 cm 2.00 1.50 1.00 0.50 0.00 Spring Fall Spring Fall Spring Fall Spring Fall Spring Fall Spring Fall Spring 2003 2003 2004 2004 2005 2005 2006 2006 2007 2007 2008 2008 2009 SETs: 2-6 mm/y sedimentation rates at PIE RSLR: 2.6 mm/y long term average (Boston) Fig.:+USGS+

Spa1al+variability+ Belowground+produc1on+ A&new&use&for& CT&scans!&&& Understanding& roots&and& rhizomes& Plum+Island+2011+ Marsh+Organ+Experiment+ CT+images+ + Coarse+roots+>/=+1mm+<+2mm,+ structures+are+yellow;+ + Rhizomes+>/=+2+mm,+ Ongoing+work+by+K.+ structures+are+orange_red+ Wigand+and+J.+Morris+

Catchment+scale+Carbon+budget+ Plum+Island+2012:+Eddy+covariance+ High+resolu1on+measurements+of+Q,+ measurements+of+CO2++++++++++++++++++++++++ DOC,+DIC+ Ongoing+work+by+I.+Forbrich+(MBL)+and+P.+Raymond,+Y.+Zhao+(Yale)+ Atmosphere_ecosystem+CO2+exchange+ +++++++++++++++++++++++++++++++++F CO2 +‘fingerprint’+ +++++++++++++Gap_filling+with+model:+NEE=GPP+Reco+ +++++++++++++submergence+effects+

Summary+ • Spa1al+variability+of+relief:+Sufficient+ sedimenta1on+rates+in+lower+areas+than+on+ high+marsh++ • Plant+produc1vity+especially+important+on+ high+marsh+ • New+methods+are+improving+our+(model)+ understanding+of+belowground+produc1on+ and+its+contribu1on+to+accre1on.+ Lateral&erosion&has&occurred&in&lower&estuary& 1953+vs+2001+shorelines+

But what about the larger spatial picture of the marsh? We see clear evidence for change – in some areas ponds are changing rapidly but in other areas of the marsh ponds are rarer and the marsh seems more stable. But even in areas where ponds appear to be common change is not in one direction, ponds form, drain and revert to Spartina alterniflora .

S. alterniflora NPP 1600 1400 1200 1000 gdw/m2/y 800 600 400 200 0 1999 2000 2001 2002 2003 2004 2005 2006 2007 There are large interannual differences in the production of the Net Aboveground Primary Production (g m-2 yr-2) 1600 marsh grass Spartina alterniflora r 2 =0.47 1400 p<.07 which appear to be related to slope=124 g/cm 1200 interannual variations in sea level 1000 rise. At Plum Island, higher rates of 800 sea level rise might at least 600 400 temporarily change the marsh from 200 one that is mainly salt marsh hay to 0 140 142 144 146 148 150 one with more cordgrass Mean High Water Level (cm)