Nitrogen Impacts on Carbon Storage and Fluxes in Wetlands - - PowerPoint PPT Presentation

▶

Nov 29, 2023 326 likes •576 views

Nitrogen Impacts on Carbon Storage and Fluxes in Wetlands Anthropogenic Nitrogen Enrichment in Coastal Ecosystems N load (kg N ha -1 4000 3000 2000 1000 0 y -1 ) Lawns & Turf Chesapeake Connecticut R. 2 Capitalizing on Coastal Blue

SLIDE 1

Nitrogen Impacts on Carbon Storage and Fluxes in Wetlands

SLIDE 2

Capitalizing on Coastal Blue Carbon Conference | May 12-13, 2015

Anthropogenic Nitrogen Enrichment in Coastal Ecosystems

1000 2000 3000 4000

Lawns & Turf Chesapeake Connecticut R.

N load (kg N ha-1 y-1)

SLIDE 3

Groundwater-borne Nitrogen Yields from Coastal Watersheds

Sewered

SLIDE 4

Isotopic evidence for anthropogenic N in estuarine food webs

Cole et al. 2004

NLM: Land Use Based Model Supported by Groundwater N Isotopic Data

SLIDE 5

“Moderate” loads with major effects in estuaries

SLIDE 6

IMPACT OF NITROGEN

Capitalizing on Coastal Blue Carbon Conference | May 12-13, 2015

SLIDE 7

1 2 3 4

Surprising shift: N2O sink to source in response to a nitrogen pulse

= Nitrate added = Control July ‘09 April ‘10 June ‘10

Moseman-Valtierra et al. 2011. Atmospheric Environment

Plots received single pulses of nitrate (0.5L of 300 m M)

m mol N2O m-2 h-1

SLIDE 8

The “Grand Experiment” N gradient in Narragansett Bay RI

Fox Hill: *10 kg N ha-1 y-1 Passeonkquis: *2418 kg N ha-1 y-1 *=Wigand et al. 2004

High N loading Low N loading

SLIDE 9

Narragansett Bay marshes

1 2 3 4 5

m mol CO2 m-2 s-1

20 40 60 80

m mol CH4 m-2 h-1

0.1
0.05

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

m mol N2O m-2 h-1 = high N load (Pass.) = low N load (Fox)

50 100 150 200

Porewater ammonium (m M)

SLIDE 10

N2O emissions vs marsh nitrogen load

50 100 150 200 250 300 50 100 150 200 250

nmol N2O m-2 h-

1 N load (g N m-2 y-1)

Waquoit Bay, MA Narragansett Bay, RI Passeonkquis Cove Average Fall 2012 N2O emissions

SLIDE 11

Nitrogen loads in our experiments

50 100 150 200 250 300 50 100 150 200 250 nmol N2O m-2 h-1

N load (g N m-2 y-1)

Phragmites experiments (Mozdzer)

Waquoit Bay, MA Narragansett Bay, RI Passeonkquis Cove Jamaica Bay, NY Plum Island TIDES Wigand (EPA) mesocosms Winyah Bay (NC) 365

SLIDE 12

IMPACT OF NITROGEN

Capitalizing on Coastal Blue Carbon Conference | May 12-13, 2015

SLIDE 13

CH4 GPP C stocks R N F(L) NECB = dC/dt = GPP – R – F(CH4) – F(L)

Quantify carbon credit: Net Ecosystem Carbon Balance (NECB = dC/dt)

CH4 GPP C stocks R F(L) NEP

SLIDE 14

CO2 fluxes across N gradient

50 100 150 200 250 300 350 400

Flux (฀mol m-2s-1)

5 10

NEP GPP R Hamblin Pond

DOY

50 100 150 200 250 300 350 400

5 10 NEP GPP R

Flux (฀mol m-2s-1)

Great Pond

DOY

50 100 150 200 250 300 350 400

5 10 NEP GPP R

Flux (฀mol m-2s-1)

Eel Pond

DOY

50 100 150 200 250 300 350 400

5 10 NEP GPP R

Flux (฀mol m-2s-1)

Low N High N

SLIDE 15

DOY 50 100 150 200 250 300 350 400

Flux (nmol m-2s-1)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 CH4

DOY

50 100 150 200 250 300 350 400 2 4 6 8 CH4

Flux (nmol m-2s-1)

DOY

50 100 150 200 250 300 350 400 0.0 0.5 1.0 1.5 2.0 2.5 3.0 CH4

Flux (nmol m-2s-1)

DOY

50 100 150 200 250 300 350 400 0.0 0.5 1.0 1.5 2.0 2.5 3.0 CH4

Flux (nmol m-2s-1)

CH4 fluxes across N gradient

Low N High N

Sage Lot Hambin Great Pond Eel Pond

SLIDE 16

Adding time：11:50-11:55 am High tide started Marsh platform was flooded

Short-term N addition experiment: N2O fluxes responding to 1.4 gN/m2

SLIDE 17

Aboveground biomass gC ≈ g biomass/2

SLIDE 18

0.00 1.00 2.00 3.00 4.00 5.00 0-10 10-20 20-30 30-40 40-50 Average Dry Weight (g)

Eel Pond (N = 4)

Roots Rhizomes 0.00 1.00 2.00 3.00 4.00 5.00 0-10 10-20 20-30 30-40 40-50 Average Dry Weight (g) Soil Depth (cm)

Sage Lot Pond (N = 9)

Roots Rhizomes 0.00 1.00 2.00 3.00 4.00 5.00 0-10 10-20 20-30 30-40 40-50 Average Dry Weight (g)

Hamblin Pond (N = 4)

Roots Rhizomes 0.00 1.00 2.00 3.00 4.00 5.00 0-10 10-20 20-30 30-40 40-50 Average Dry Weight (g) Soil Depth (cm)

Great Pond (N=3)

Roots Rhizomes

Root and Rhizome biomass

SLIDE 19

Above- and belowground biomass

High N High N Low N Low N

SLIDE 20

Preliminary conclusions

Small amounts of N loading (1-10 gN m-2y-1) did not

change the carbon fluxes, likely because N loaded via groundwater was primarily used by microbes and

phytoplankton. Salt marsh and GHG emissions may be

significantly changed when N loading increased to a threshold level.

N2O fluxes are not significant in these salt marshes, but

adding N may result in high N2O fluxes.

Higher belowground biomass were found in relatively

high N loading marshes, but not seen for aboveground biomass.

SLIDE 21

IMPACT OF NITROGEN LOADING ON CARBON BURIAL

Capitalizing on Coastal Blue Carbon Conference | May 12-13, 2015

SLIDE 22

There is a moderate nitrogen loading gradient to Waquoit Bay marshes.

Capitalizing on Coastal Blue Carbon Conference | May 12-13, 2015

Core locations

12.6 6.3 2.9 0.5

Great Pond Sage Lot Pond Hamblin Pond Eel Pond 0.5 N Loading g/m2/year

SLIDE 23

Nitrogen isotopes indicate anthropogenic additions are increasing across the salt marshes.

Capitalizing on Coastal Blue Carbon Conference | May 12-13, 2015

R² = 0.66 1 2 3 4 5 5 10 15 d15N organic matter 1950-present Nitrogen load (g m-2 y-1)

SLIDE 24

There is no difference in carbon burial across the nitrogen gradient within Waquoit Bay.

Capitalizing on Coastal Blue Carbon Conference | May 12-13, 2015

50 100 150 200 250 2 4 6 8 10 12 14 Carbon burial 1950-present (g m-2 y-1) Nitrogen load (g m-2 y-1)

High Marsh