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