Effects of Rising Nitrogen Deposition on Forest Carbon Sequestration

and N losses in the Delaware River Basin 

Yude Pan, John Hom, Richard Birdsey, Kevin McCullough 

USDA Forest Service, Newtown Square, PA 19073, USA

Delaware River Basin Collaborative Environmental Monitoring and Research Initiative (CEMRI)

A Pilot Program of the National Environmental Monitoring Initiative (NEMI)

USDA Forest ServiceUSGSNational Park Service

Delaware River Basin 1991 MRLC LULC

2%

57%

25%

1%

5% 9%1%Water

Developed

Open

Forest

Agriculture

Grasses

Wetland

Scientific issues Scientific issues

How does the increased atmospheric N How does the increased atmospheric N deposition interact with other stressors to affect deposition interact with other stressors to affect forest carbon sequestration in the Delaware forest carbon sequestration in the Delaware River Basin?River Basin?

What is the potential capacity of the forests What is the potential capacity of the forests retaining the atmospheric N deposition and how retaining the atmospheric N deposition and how much of nitrate is lost annually from forests to much of nitrate is lost annually from forests to surface water in the Delaware River Basin?surface water in the Delaware River Basin?

1. Gross photosynthesis2. Foliar respiration3. Transfer to mobile C4. Growth and maintain resp.5. Allocation to buds6. Allocation to fine roots7. Allocation to wood8. Foliar production9. Wood production10. Soil production11. Precipitation12. Interception13. Snow-rain partition14. Snowmelt15. Fast flow16. Water uptake17. Transpiration18. Drainage19. Wood litter20 Root litter21. Foliar litter22. Wood decay23. Mineralization24. N uptake25. To soil solution

Diagram of PnET Model

Water

Wood C/N

Wood

DeadWood

Soil

FineRoot

Plant C/N

Carbon/Nitrogen

BudC/N

NH4NO3

Soil Water

FoliarCanopy

10

9

19

22

20

23

6

7

4

24

5 8

3

21

25

16

18

15

Snow

12 1712

11

13

14

Model concepts Process-based, mechanistic models. Simulate carbon, nitrogen and water cycles, pools and fluxes based on mass-balance. We can more successfully predict the variables in terrestrial ecosystems if we model the basic processes controlling them. Methodology differs from classic statistical based empirical relationships. Feedbacks and constraints on fluxes and pools affect the ecosystem as a whole.  

1. Gross photosynthesis2. Foliar respiration3. Transfer to mobile C4. Growth and maintain resp.5. Allocation to buds6. Allocation to fine roots7. Allocation to wood8. Foliar production9. Wood production10. Soil production11. Precipitation12. Interception13. Snow-rain partition14. Snowmelt15. Fast flow16. Water uptake17. Transpiration18. Drainage19. Wood litter20 Root litter21. Foliar litter22. Wood decay23. Mineralization24. N uptake25. To soil solution

Diagram of PnET Model

Water

Wood C/N

Wood

DeadWood

Soil

FineRoot

Plant C/N

Carbon/Nitrogen

BudC/N

NH4NO3

Soil Water

FoliarCanopy

10

9

19

22

20

23

6

7

4

24

5 8

3

21

25

16

18

15

Snow

12 1712

11

13

14

Model Experiments under Different Atmospheric Chemistry Scenarios (version 3)

Model Run /input N deposition CO2 Ozone Inter-

action Running

years Run1, control No N input (0.0 g/m2) Fixed, 280 ppmv No No 200 yrs up to 2000 Run 2, scenario Ramped up to N deposition level of 2000 Fixed, 280 ppmv No No 200 yrs up to 2000 Run 3, scenario No N input (0.0 g/m2) Ramped (280-366 ppmv) No No 200 yrs up to 2000 Run 4, scenario Ramped up to N deposition level of 2000 Ramped (280-366 ppmv) No No 200 yrs up to 2000 Run 5, scenario Ramped up to N deposition level of 2000 Ramped (280-366 ppmv) Yes Yes 200 yrs up to 2000 Run 6, scenario Doubled N input by 2000 Fixed, 280 ppmv No No 200 yrs up to 2000 Run 7, scenario Doubled N input by 2000 Ramped (280-366 ppmv) Yes Yes 200 yrs up to 2000 Run 8, scenario Ramped to N deposition level of 2000, then

continue to increase linearly Ramped up to 600 ppmv Yes Yes 300 yrs up to 2100

Run 9, scenario Ramped up to N deposition level of 2000, then level off

Ramped up to 366 ppmv in 2000, then fixed

Yes Yes 300 yrs up to 2100

Run 10, scenario Ramped up to N deposition level of 2000, then level off

Fixed, 280 ppmv No No 250 yrs up to 2050

Run 11, scenario Ramped to N deposition level of 2000, then continue to increase linearly

Fixed, 280 ppmv No No 250 yrs up to 2050

Wet+dry

Year

Scenarios of Atmospheric Chemistry

Year

Elevated

CO

2 (pp

mv)

N d

e po s

iti o

n (

Kg /

ha )

Scenarios of Atmopsheric N Deposition

Year

1900 1925 1950 1975 2000 2025 2050

N d

epo

siti

on

(K

g/h

a)

0

4

8

12

16

20

241 x N2 x N1 x N increase1 x N regulation

An

nu

al N

PP

(g/

m2 )

+22% +12% +47% +25%

Annual NPP under Different Scenarios(Delaware River Basin )

Annual NPP under N deposition scenarios(Delaware River Basin)

An

nu

al N

PP

(g

/m2/y

r)

0

200

400

600

800

1000

1200

Control1X N 2 x N1 x N regulation

+22% +25% +24%

Forest Biomass under Different ScenariosB

iom

ass

(Mg

/ha)

+11% +18% +38% +4%

Forest biomass under N deposition scenariosB

Iom

ass

(Mg

/ha)

0

50

100

150

200

250

300

Control1x N 2 x N1 x N regulation

+11% +4% +10%

Soil Organic Matter under Different Scenarios S

oil o

rgan

ic m

atte

r (M

g/h

a)

+22% +5% +28% +34%

Soil mass under N deposition scenariosS

oil

mas

s (

Mg

/ha

)

0

20

40

60

80

100

120

140

160

180

Control1x N2 x N1 x N regulation

+22% +34% +39%

Soil N leaching under N deposition scenarios

N le

ach

ing

loss

(k

g/h

a)

0

2

4

6

8

10

Control1xN 2 x N1 x N regulation

Retention rates:

85%

75%

79%

Table 2a. The predictions of the forest N exports to streams and N retention rates in the Delaware River Basin. Current N Scenario (Mean N deposition = 11.5 kg N ha-1 yr-1 ) Tree Forest area Total N loss Min Max Mean STdev N retention Groups (km2) (Mg N) (kg N ha-1 yr-1) (%) N. Hardwood 3,455 649.56 0.813 4.478 1.879 0.350 84 Oak-hickory 11,919 175.43 0.508 4.066 1.474 0.486 87 Pine 1,242 314.50 0.665 12.340 2.530 2.654 75 Oak-pine 1,075 316.20 0.569 10.770 2.938 1.406 74 Region 17,695 3037.91 0.508 12.340 1.716 0.990 85

Doubled N Scenario (Mean N deposition = 23.1 kg N ha-1 yr-1) Tree Forest areas Total N loss Min Max Mean STdev N retention Groups (km2) (Mg N) (kg N ha-1 yr-1) (%) N. Hardwood 3,455 2292.10 1.702 20.310 6.632 3.239 71 Oak-hickory 11,919 5589.62 0.990 21.280 4.689 3.526 80 Pine 1,242 1316.06 3.965 22.500 10.587 3.193 47 Oak-pine 1,075 844.32 2.407 25.190 7.846 3.038 65 Region 17,695 10043.13 0.990 25.190 5.675 3.810 75

Table 2b. The predictions of the forest N exports to streams and N retention rates in the Delaware River Basin. Current N Scenario (Mean N deposition = 11.5 kg N ha-1 yr-1 ) Tree Forest area Total N loss Min Max Mean STdev N retention Groups (km2) (Mg N) (kg N ha-1 yr-1) (%) N. Hardwood 3,455 649.56 0.813 4.478 1.879 0.350 84 Oak-hickory 11,919 175.43 0.508 4.066 1.474 0.486 87 Pine 1,242 314.50 0.665 12.340 2.530 2.654 75 Oak-pine 1,075 316.20 0.569 10.770 2.938 1.406 74 Region 17,695 3037.91 0.508 12.340 1.716 0.990 85

N regulation Scenario (Mean N deposition = 11.5 kg N ha-1 yr-1) Tree Forest areas Total N loss Min Max Mean STdev N retention Groups (km2) (Mg N) (kg N ha-1 yr-1) (%) N. Hardwood 3,455 893.08 0.803 10.200 2.584 1.423 78 Oak-hickory 11,919 2223.31 0.507 10.880 1.865 1.337 84 Pine 1,242 655.51 1.768 12.310 5.273 2.145 48 Oak-pine 1,075 433.27 1.003 12.880 4.026 1.597 65 Region 17,695 4205.67 0.507 12.880 2.376 1.737 79

Selected FIA sites(mature) forvalidation (n=98)

FIA derived biomass (Mg/ha)

0 100 200 300 400

Mo

del

ed v

eg b

iom

ass

(Mg

/ha)

0

100

200

300

400

N. PineS. PineOak-pineOak-hickoryAsh-elmN. Hardwood

n=318

FIA derived biomass (Mg/ha)

0 100 200 300 400

Mo

del

ed v

eg b

iom

ass

(Mg

/ha)

0

100

200

300

400

N. PineS. PineOak-pineOak-hickoryAsh-elmN. Hardwood

n=318

Conclusions:Conclusions:

The modeling results suggest that chronic N increases in The modeling results suggest that chronic N increases in the past 70 years has increased forest productivity by the past 70 years has increased forest productivity by 22%, forest biomass of 11% and soil organic matter of 22%, forest biomass of 11% and soil organic matter of 22%.  Overall, the interactive effects of rising N 22%.  Overall, the interactive effects of rising N deposition and CO2 caused remarkable C gains in deposition and CO2 caused remarkable C gains in forest living biomass (38%) and soil mass (28%). The forest living biomass (38%) and soil mass (28%). The forest regrowth in the region only counted for about forest regrowth in the region only counted for about 62% of the carbon sequestrated in the forest 62% of the carbon sequestrated in the forest ecosystems. ecosystems.

Forests in the Basin seem close to N saturation status Forests in the Basin seem close to N saturation status under current N deposition level. 2X N deposition under current N deposition level. 2X N deposition resulted in similar increases in annual NPP, and lower resulted in similar increases in annual NPP, and lower forest biomass with respect to 1X N.forest biomass with respect to 1X N.

The current N leaching loss from the forested land of the The current N leaching loss from the forested land of the DRB is 1.7 Kg/ha, and N retention rate is 85%. DRB is 1.7 Kg/ha, and N retention rate is 85%.

With 2X N deposition scenario, the N retention rate will With 2X N deposition scenario, the N retention rate will drop to 75% and the total N export to stream water drop to 75% and the total N export to stream water would nonlinearly increase by 330%. would nonlinearly increase by 330%.

Extending the current 1X N regulation for another 50 Extending the current 1X N regulation for another 50 years, leveling off N deposition at the current level years, leveling off N deposition at the current level would lower retention to 79% from 85%, and the total N would lower retention to 79% from 85%, and the total N export would increase by 38%, suggesting there will export would increase by 38%, suggesting there will eventually be N saturation at current deposition levels.eventually be N saturation at current deposition levels.

Future Work:Future Work:

Explore the effects of zone and calcium depletion on forest Explore the effects of zone and calcium depletion on forest productivity.productivity.

Improve the modeling predictions at the basin level by incorporating Improve the modeling predictions at the basin level by incorporating information of forest fragmentation and land-use types. information of forest fragmentation and land-use types.

Refine the modeling work with the MODIS vegetation classes and the Refine the modeling work with the MODIS vegetation classes and the new parameterization. new parameterization.

Explore the effects of climatic variations and interactions with other Explore the effects of climatic variations and interactions with other

global change factors. global change factors.

Project the forest conditions under the 2100 scenario with multiple Project the forest conditions under the 2100 scenario with multiple stressors. stressors.

Thank You !