Estimating litter and soil carbon stocks on managed

forest land in Alaska, USAGrant M. Domke1, Andrew Gray2, Brian Walters1, Charles Perry1, Lucas Nave4, Stephen Ogle3, Brendt Mueller2

1Northern Research Station, USDA Forest Service; 2Pacific Northwest Research Station, USDA Forest Service; 3Natural Resource

Ecology Laboratory, Colorado State University; 4University of Michigan Biological Station

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Importance of C in soils

Largest terrestrial sink

UNFCCC reporting

Much is in forests

Influences biological, chemical, and

physical soil functions

…much uncertainty exists

Jandl, R., Rodeghiero, M., Martinez, C., Cotrufo, M. F., Bampa, F., van Wesemael, B., Harrison, R.B., Guerrini, I.A., deB Richter Jr., D., Rustad, L., Lorenz, K., Chabbi, A., Miglietta, F. 2014. Current status, uncertainty and future needs in

soil organic carbon monitoring. Science of the Total Environment, 468, 376-383.

Lal, R. 2005. Forest soils and carbon sequestration. Forest Ecology and Management, 220(1), 242-258.2

Why the change in litter and SOC methods?

Smith, James E. et al. 2006. Methods for calculating forest ecosystem and harvested carbon with standard estimates for forest types of the United States. Gen. Tech. Rep. NE-343. Newtown Square, PA: U.S. Department of Agriculture,

Forest Service, Northeastern Research Station. 216 p

Amichev, B. Y., & Galbraith, J. M. 2004. A revised methodology for estimation of forest soil carbon from spatial soils and forest inventory data sets. Environmental Management, 33(1), S74-S86.

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Domke, G.M., Walters, B.F., Perry, C.H., Woodall, C.W., Russell, M.B., Smith, J.E. 2016. Estimating litter carbon stocks on forest land in the United States. Science of the Total Environment 557-558: 469-478.

Domke, G.M., Perry, C.H., Walters, B.F., Woodall, C.W., Nave, L., Swanston, C. 2017. Toward inventory-based estimates of soil organic carbon in forests of the United States Ecological Applications.

NFI sampling frame

Core field

1 plot per 2,430 ha

Intensive field

1 plot per 38,880 ha

Prefield analysis

Bechtold W.A. and Patterson, P.J. 2005. The enhanced Forest Inventory and Analysis program—national sampling design and estimation procedures. Gen. Tech. Rep. SRS-80. 85 p.

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Managed forest land in Alaska

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NFI plot design

Bechtold W.A. and Patterson, P.J. 2005. The enhanced Forest Inventory and Analysis program—national sampling design and estimation procedures. Gen. Tech. Rep. SRS-80. 85 p.

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NFI litter and soil sampling

ucftBDCSOC iiiFIA

USDA Forest Service 2011. Phase 3 Field Guide – Soil Measurements and Sampling, Version 5.1. Last accessed: 08/10/2015. http://www.fia.fs.fed.us/library/field-guides-methods-proc/docs/2012/field_guide_p3_5-

1_sec22_10_2011.pdf

O’Neill, K.P., Amacher, M.C., Perry, C.H. 2005. Soils as an indicator of forest health: a guide to the collection, analysis, and interpretation of soil indicator data in the Forest Inventory and Analysis program. Gen. Tech. Rep. NC-258. St.

Paul, MN: US Department of Agriculture, Forest Service, North Central Research Station. 53 p.

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NFI sampling and reporting depth

Belowground C without coarse roots but

including fine roots and all other organic

carbon not included in other pools, to a

depth of 1 m.

Smith, James E.; Heath, Linda S.; Skog, Kenneth E.; Birdsey, Richard A. 2006. Methods for calculating forest ecosystem and harvested carbon with standard estimates for forest types of the United States. Gen. Tech. Rep. NE-343.

Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 216 p

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NFI and ISCN data

SOIL_ORDER FIA profiles ISCN profiles Measurements

Alfisol 840 558 5895

Andisol 135 154 1256

Aridisol 129 9 281

Entisol 234 127 1190

Gelisol 0 10 63

Histosol 58 171 1203

Inceptisol 577 250 2614

Mollisol 588 200 2451

ORDER_NOT_FOUND 0 265 2254

Oxisol 0 13 82

Spodosol 407 246 2583

Ultisol 686 311 3553

Vertisol 13 11 114

TOTAL 3667 2325 23539

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NFI and ISCN data

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lm fits

DepthISOC 1010 loglog

Soil order Intercept Slope r2 F-statistic p value

All 1.1795 -0.8228 0.56 29646.79 <0.001

Alfisols 1.1122 -0.8330 0.64 10657.50 <0.001

Andisols 1.3837 -0.8425 0.49 1185.78 <0.001

Aridisols 0.2065 -0.1300 0.02 6.55 0.011

Entisols 0.9300 -0.7207 0.39 752.34 <0.001

Histosols 1.6227 -1.0109 0.59 1724.22 <0.001

Inceptisols 1.1631 -0.7331 0.52 2833.00 <0.001

Mollisols 1.0163 -0.6214 0.51 2569.03 <0.001

Spodosols 1.4262 -0.9801 0.61 4097.61 <0.001

Ultisols 1.1576 -0.8867 0.68 7450.16 <0.001

Vertisols 0.5145 -0.2427 0.08 9.58 0.002

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Domke, G.M., et al. 2017. Toward inventory-based estimates of soil organic carbon in forests of the United States. Ecological Applications

Predicted profiles

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Domke, G.M., et al. 2017. Toward inventory-based estimates of soil organic carbon in forests of the United States. Ecological Applications

From 448 plots to 3816 plots…

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Modeling approaches

LAT, LON, ELEV, SLOPE, ASPECT, WATERCD, FORTYPGRP, STDAGE, PHYSCLCD, SITECLCD, STDORGCD, DISTURB,

TRTMNT, BALIVE, SDI, REL_DENS, AGLT_C_MGHA, WORLDCLIM (many), GMI, YSD, SOIL_ORDER, SURF_NAME,

SURF_DEPTH, FIRE_PERIMETER, PCT_GELISOL, PERMAFROST_CLASS, NDVI (many), LANDFIRE (many), among

others

Breiman L. 2001. Random forests. Machine Learning. 45(1):5-32.

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Pruning and variable selection

),,max,,,,,,()( surfgeoordergmitpptfortypgrpelevlonlatfSOCP

RMSE: 34.9 on 1091 DF,

R2: 0.38,

F-stat: 536 on 1 and 1091 DF,

p-value: < 0.0001

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Domke, G.M., et al. 2017.. Toward inventory-based estimates of soil organic carbon in forests of the United States. Ecological Applications

Model comparisons for coastal AK

The estimates (NFI observations) and predictions (RF predictions) were statistically equivalent

Wellek, S. 2003. Testing Statistical Hypotheses of Equivalence. Chapman & Hall, London, England.

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Soil carbon

Litter carbon

Take aways… The contribution of litter and soil C in forests has

been grossly underestimated in recent NIRs in the

US

Preliminary estimates of litter C stocks on

managed forest land in AK = 985 ± 153 MMT C –27% of all litter C on managed forest land in the

US

Preliminary estimates of soil C stocks (30 cm) on

managed forest land in AK = 3762 ± 513 MMT C –12% of all soil carbon stocks in the US

Improvement but much variability and substantial

uncertainty 17

Thanks!

Grant Domke: gmdomke@fs.fed.us

FIA carbon: http://www.fia.fs.fed.us/forestcarbon/

FIA program: www.fia.fs.fed.us

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