Chronosequence of soil respiration in ChEAS sites (sub-topic of spatial upscaling of carbon measurement) Jim Tang Department of Forest Resources University of Minnesota
Factors for simulating long-term forest carbon dynamics Natural variability and disturbance Human disturbance and management Climate change: T, precipitation… Increasing atmospheric CO 2 concentration and nitrogen deposition -- fertilization Forest succession
Why chronosequence Our knowledge in understanding the influence of forest succession on carbon dynamics is limited. Most long-term carbon simulation models do not consider forest succession as a variable.
Forest stands with different ages Old-growth Mature YoungClear-cut
Soil respiration measurement
Soil temperature
Chronosequence of soil respiration in response to temperature YA: Young aspen IA: intermediate aspen MH: mature hardwood OG: old- growth
Chronosequence of soil respiration
Chronosequence of soil carbon content, annual change of soil carbon, and nitrogen content
YA: young aspen, IA: intermediate aspen. MH: mature hardwood, OHD: old-growth hardwood, OHL: old-growth hemlock Tang et al., Agri. For. Met., in press Cumulative respiration and components
Odum, 1969, ScienceRyan et al. 1997, Ad. Eco. Res. Successional pattern of carbon flux: two conceptual models
Simulate long-term large-scale soil carbon Century model
Published work
Eddy Covariance vs. chamber measurements Tang et al., Agri. For. Met., in press
Sap flow vs. tower measurement of water flux Tang et al., J. Geophys. Res.- Biogeosciences E C = 65% E T in the growing season
Water use efficiency (WUE = GPP/E C ) response to D (VPD) Tang et al., J. Geophys. Res.- Biogeosciences
Work in progress
Diurnal patterns of soil respiration Year 2005 Validate nighttime eddy covariance data, and correspondingly, daytime GPP; Parameterize the soil respiration model. Year 2006