1. Mass and Nutrient Loss in Decaying Hardwood Boles at Hubbard Brook
Chris E. Johnson, Syracuse University
Thomas Siccama, Yale University
Daniel Vogt, University of Washington

2. Coarse Woody Debris Habitat for birds, reptiles, mammals.
Important substrate in the detrital food chain.
Significant pool of C and nutrients in forest ecosystems:
Hubbard Brook (Fahey et al. 2005):
Coarse Woody Debris: 468 g C m-2
Forest Floor Carbon: 2970 g C m-2
Above-ground Biomass: 9500 g C m-2
Few species-level data for decay rates and nutrient dynamics in northern hardwoods.

3. Objectives
Estimate exponential decay rate constants for yellow birch, sugar maple and American beech wood and bark under normal field conditions.
Determine the rate loss (or gain) for essential nutrients N, P, K, Ca, Mg in wood and bark.
[Study the changes in structural chemistry of wood and bark during decomposition using 13C NMR spectroscopy.]

4. Field Incubation

5. Measurement

6. Sampling Bark

7. Sampling Wood

8. Decomposition Rates

9. Rates and Half-Lives Sample km (yr-1) Half-Life (yr) Beech Boles
0.097 ± 0.009
7.18
Beech Wood
0.095 ± 0.009
7.30
Beech Bark
0.141 ± 0.029
4.92
Sugar Maple Boles
0.079 ± 0.007
8.76
Sugar Maple Wood
0.076 ± 0.008
9.17
Sugar Maple Bark
0.116 ± 0.009
6.00
Yellow Birch Boles
0.065 ± 0.006
10.7
Yellow Birch Wood
0.064 ± 0.006
10.9
Yellow Birch Bark
0.074 ± 0.007
9.35

10. C:N Ratios Decline During Decomposition

11. Changes in Nutrient Concentrations

12. Conclusions
Hardwood boles at Hubbard Brook decay with half-lives ranging from 7.2 to 10.7 years.
Concentrations of nitrogen and calcium increased, while potassium decreased, during decomposition.
Nutrient concentrations in fresh and decaying wood and bark are highly variable.
Despite the high variability, nutrient dynamics in coarse woody debris in Watershed 2 could be modeled using relationships derived from this study.

13. Acknowledgments