Comparison of nitrogen cycling between old growth forests and secondary forests

in the U.S. Mid-Atlantic

Jennifer McGarvey

Rebecca Walker rhw6tp@virginia.edu CSS Fall Symposium

Oct. 29, 2014

Co-advisors: Dr. Howard Epstein; Dr. Aaron Mills

1

Land-use change in the eastern U.S. (1600 – Current)

S. Dunker 2011 1850-1900s

Early to mid 1600s

Albani et al. 2006

Earle and Hoffman 1980

2

S. Dunker 2011 1850-1900s

Early to mid 1600s

Albani et al. 2006

Earle and Hoffman 1980

Land-use change in the eastern U.S. (1600 – Current)

2

Current forest cover in the eastern U.S.

< 1% of eastern forests are

considered old growth (> 150 years) (Davis 1996).

Albani et al. 2006

2.6±0.8 PgC y-1

28% Calculated as the residual

of all other flux components

~ 70% of all Mid-Atlantic forests are 50 – 100 years old (Drummond

and Loveland 2010).

2

CO2

Soil Organic Matter

C:N = 25

NO3

NH4

N Deposition Vegetation

C:N = 50

Wood C:N = 200

Respiration

Litter fall/Decompositi

on

C and Nitrogen (N) cycling in Temperate Forests 3

Nitrogen through Succession

Updated from Schirkonyer et al. 2013

Top 5 cm Soil N v. Stand Age

4

Research Questions

Does the total nitrogen pool in the organic horizon increase with stand age in Mid-Atlantic forests? How do the dynamics of organic and inorganic nitrogen change as a forest transitions from secondary growth to old growth? Does a correlation exist between soil nitrogen characteristics and the amount of carbon stored within old growth forests of the Mid-Atlantic?

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87,383 km2

Methods: Study Area

25 productive stands

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Old Growth Definition

Large volume dead wood

High densities of old, large-diameter trees

Old growth is defined by 1) high densities of large-diameter trees, 2)

large dead wood volume, 3) associated canopy gaps, 4) multi-layer canopy, 5)

lack of human disturbance.

7

© John Chao © Hubbard Brook Experimental Forest

© Offwell Woodland and Wildlife Trust

Pools Sampled

Aboveground Live Biomass

Belowground Live Biomass

C

C C

Litter

X

C N

Aboveground Dead Biomass

Organic Horizon

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© John Chao © Hubbard Brook Experimental Forest

© Offwell Woodland and Wildlife Trust

Pools Sampled

Aboveground Live Biomass

Belowground Live Biomass

C

C C

Litter

X

C N

Aboveground Dead Biomass

Organic Horizon

10 tree cores in each stand from largest trees to estimate max stand age

Results & Discussion: N through Forest Succession

Does the N pool in the O horizon increase with stand age in Mid-Atlantic forests?

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Results & Discussion: N through Forest Succession 10

How do the dynamics of organic and inorganic N change as a forest transitions from secondary growth to old growth?

Results & Discussion: N through Forest Succession 11

R2 = 0.517 m = 0.971

R2 = 0.568 m = 0.973

R2 = 0.784 m =1.065

Results & Discussion: N through Forest Succession 12

Does a correlation exist between soil N characteristics and the amount of C stored within old growth forest stands of the Mid-Atlantic?

Results & Discussion: Soil Quality Indices and Carbon Storage

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Results & Discussion: Soil Quality Indices and Carbon Storage

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Conclusions

Suggests decrease in C sequestration potential in O-horizon in old growth stands and greater potential for leaching loss

Site specific characteristics that vary on

a regional level drive N dynamics

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• Mentors: Howard Epstein and Aaron Mills and Jennifeer McGarvey

• National Science Foundation • Uva College Science Scholars Progran • Charles Henry Leach, II Foundation; Wendy

R. Besien and Stephen M. Van Besien; Lois A. Fitton & W. Christopher Draper, Jr.; Sharon B. Parente & John W. Risner; The Jefferson Trust; Mary Baroody Lowe & Jeffrey A. Lowe; The UVa Parents Fund and Committee; J. Randolph and Rossie Carter Hutcheson; Entigence Corporation; Robert Atkinson

Acknowledgements 16