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 km2) and estuarine system (60 km2) 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

• rganic matter (MEM III by Jim Morris, USC).

Depth+Below+MHW+ Aboveground+ Biomass+

Marsh+Equilibrium+model+

Mean high water MSL Elevation MARSH PLATFORM Mean low water

• S. alterniflora

Morris+et+al.+(2002)+

Surface+Eleva1on+Table+(SET)+

SETs: 2-6 mm/y sedimentation rates at PIE RSLR: 2.6 mm/y long term average (Boston)

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50

Spring 2003 Fall 2003 Spring 2004 Fall 2004 Spring 2005 Fall 2005 Spring 2006 Fall 2006 Spring 2007 Fall 2007 Spring 2008 Fall 2008 Spring 2009

cm Law's SET Cumulative change averages

Law's Point 2 alterniflora Law's Point 3 patens

Fig.:+USGS+

Spa1al+variability+ Belowground+produc1on+

Plum+Island+2011+ Marsh+Organ+Experiment+ CT+images+ + Coarse+roots+>/=+1mm+<+2mm,+ structures+are+yellow;+ + Rhizomes+>/=+2+mm,+ structures+are+orange_red+

A&new&use&for& CT&scans!&&& Understanding& roots&and& rhizomes&

Ongoing+work+by+K.+ Wigand+and+J.+Morris+

Catchment+scale+Carbon+budget+

Ongoing+work+by+I.+Forbrich+(MBL)+and+P.+Raymond,+Y.+Zhao+(Yale)+ Plum+Island+2012:+Eddy+covariance+ measurements+of+CO2++++++++++++++++++++++++ High+resolu1on+measurements+of+Q,+ DOC,+DIC+

Atmosphere_ecosystem+CO2+exchange+

+++++++++++++++++++++++++++++++++FCO2+‘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.

Mean High Water Level (cm) 140 142 144 146 148 150 Net Aboveground Primary Production (g m-2 yr-2) 200 400 600 800 1000 1200 1400 1600

r2=0.47 p<.07 slope=124 g/cm

• S. alterniflora NPP

200 400 600 800 1000 1200 1400 1600 1999 2000 2001 2002 2003 2004 2005 2006 2007 gdw/m2/y

There are large interannual differences in the production of the marsh grass Spartina alterniflora which appear to be related to interannual variations in sea level

• rise. At Plum Island, higher rates of

sea level rise might at least temporarily change the marsh from

• ne that is mainly salt marsh hay to
• ne with more cordgrass