Effects of silvicultural practices on forest soil metabolism
Claire PhillipsFS 533
Winter 2007
“Soil Respiration”
Mixture of CO2 produced by roots, mycorrhizae, and soil decomposition
Generally the single largest efflux of CO2 from forests
>70% of ecosystem respiration in temperate forests
Explanatory VariablesSoil Temperature
F = F0eT
Soil Moisture
Biomass
Microbial respiration:Litter Quality, C:N
Root respiration: Nutrient Limitations Phenology
Silvicultural Practices:
Thinning
Rotation Length
ThinningMixed-conifer forest, Sierra Nevada (Tang et al. 2005)• Overall, no net effect of thinning on soil respiration• Thinning increases soil temperature and moisture • For a given temperature and moisture level respiration is
lower under thinned treatment
Rotation LengthDoes soil respiration correspond with
aboveground productivity?
Chronosequence studies show relationship with fine root biomass (Ewel 1987, Bond-Lamberty 2004, Howard 2004)
(Howard 2004)
Root biomass differs from aboveground biomass
Conclusions
• Short term effects of silvicultural treatments mediated by changes in temperature, moisture, live root biomass
• Long term effects mediated by fine root growth
• Fine root biomass not predictable from aboveground biomass or growth
• General trends lack predictive power
