The single largest component in the calculation of
net CO2 flux from mid-latitude deciduous forests is the flux from forest
floor and soil respiration; however, accurate measurements and partitioning of
this flux into heterotrophic and autotrophic components are difficult. In recent years, there has been increased
interest in measuring and modeling soil respiration as various ecosystem-level
carbon dynamics studies have continued to identify the importance of this
flux. Estimates of seasonal soil
respiration rates for 2005 made by direct measurement using an automated
chamber system in trenched (heterotrophic only respiration) and untrenched (total soil CO2 efflux) plots are
compared with estimates of whole ecosystem respiration generated by eddy
covariance flux measures. This research
was conducted at the AmeriFlux site in the
Morgan-Monroe State Forest (MMSF). MMSF
is predominately secondary successional broadleaf
forest. There are a wide variety of tree
species present in this region, as it is located within the transition zone between
the maple-beech and oak-hickory associations of the Eastern Deciduous Forest. We estimate an annual partitioning ratio for heterotrophic
versus autotrophic respiration to be ~1:1.
Estimates of total ecosystem respiration by the flux tower are
consistently lower than estimates of total soil CO2 efflux though
these should be higher during the growing season. However, trenched, untrenched
and whole ecosystem respiration measurements were similar during the non-growing
season, as expected.