The Puzzling C Source that is WLEF

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The Puzzling C Source that is WLEF

• P. Bolstad, B. Cook, J. Martin, K. Davis

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When do two negative numbers equal a positive
number?
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When do two negative numbers equal a positive
number?
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Hypotheses

• Upland source clearcuts, blowdowns
• Weaker upland sink lower stocking, poorer sites,
  different species
• Wetland source
• Flux tower error

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Approach 1 Measure / model the fluxes
Ecosystem respiration
Gross photosynthesis
Microbial respiration (decomp-osition)
Plant respiration
Leaf fall
Soil carbon
Fine root turnover
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Land Cover
Upland 55-70 Wetland 30 42 Urban 0 2
WLEF
upland
wetland
water
urban
25 km
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Approach 2 Change in Pools
Two primary pools wood and soils
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Approach 2 Estimate Changes in Pools Bin
landscape into small number of classes Estimate
change in pool size for each class Expand by
area for estimate of net flux What rates would
be required of disturbed uplands to create a
regional source? Note preliminary estimates to
identify the most likely candidate for our tower
contradiction
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Estimate C Pools (1st approximation)

• Net flux S delta pools
• Main pools
• Detrital C
• Soil C
• Woody C

• Simplifying Assumptions
• Soil C changes at slow rates
• Aboveground woody C most important, most times
• Belowground woody C is a fixed function of
  aboveground woody C,
• Detrital C tied to woody C production, mortality
• All these may be estimated, given dominant
  species, age, and stocking

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Accrual
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Loss
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Upland forests Long growth phase
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Burroughs, 2002
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Growth f(age,site,stocking)
Schlaegel, 1971
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TM to LAI LAI to ANP
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LAI based on reflectance
0
8.2
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Stocking
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Stand C Net Loss Early Post Disturbance
Questions disturbance rates and detrital
trajectories
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Land Cover image time series
1987
1996
2003
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Transitions harvest and regrowth
1996
2003
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Detrital production
CWD At a given age, larger diameter trees less
likely to die Death rate increases with
age Foliar and fines Increases to balanced
state higher for conifers than broadleaves
Zavitkovski et al., 1991
www.efi..fi
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Observations

• Cleared areas lt2/year beneath WLEF
• Based on eight upland forest classes (4 ages, two
  productivity classes) unimaginably high detrital
  pools and soil losses due to clearing for flux to
  be negative based on uplands alone

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Lacuna

• Poor characterization of variability in forest
  structure, growth
• Poor characterization of detrital pools,
  trajectories
• Soil losses in non-disturbed forests?

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Improved landcover
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150 Inventory Plots FIA Design

• Measurements
• species
• diameter
• height
• radial growth
• age
• CWD
• physiographic position
• standing dead
• site
• crown density
• disturbance
• hydric status

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