Comparison of nitrogen cycling between old growth forests and secondary forests
in the U.S. Mid-Atlantic
Jennifer McGarvey
Rebecca Walker [email protected] 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
14
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
