RAINFOR GEM Intensive Plots Manual (pdf) - University of Oxford

To measure stem CO 2 efflux (commonly called “stem respiration” 58 ), place the SRC firmly onto thecollar, maintain pressure on the chamber and commence IRGA measurement (Appx. II). For eachmeasurement, carefully check the CO 2 accumulation curve to ensure that any initial CO 2 flush period is notincluded in the calculation of fluxes.Record CO 2 efflux with the IRGA and SRC system from each collar every month 59 (or as often asresources allow) (Appx. II).Equipment: 50 PVC collars (5 cm long and of a diameter to fit the SRC-1, see Appx. II; perhaps also a coupleof spares), Fix-All sealant 60 (one 290 ml sealant tube can do 6-7 stems; if Fix-All is not available, use fume-freeimpermeable putty), an applicator/sealant gun (and two spares because they break easily), strong scissors,compass, map, perhaps a metal spoon (if possible; not necessary because you can smooth the sealant using afinger), a rag for removing excess sealant and a list of the tree numbers to be used.Time required: estimate a day to do a 1 ha plot in a team of two.CO 2 efflux measurements provide a mean value for each plot of CO 2 flux per unit area of stem surface (abovethe bark). To derive a rough estimate of stand-scale stem CO 2 efflux, per unit ground area, first calculate stemsurface area for each individual tree (A stem in m 2 , which is the surface area of all above-ground wood exceptsmall twigs, not just the bole surface area A bole ) with either the equation for the surface area of a cylinder (forpalms, tree ferns and other branchless tree forms):DPOMAstem= Abole= 3.1416 * * H100or for all other stems use equation 10 of Chambers et al. (2004) 61 :boleA stem23−0.105−0.686X + 2.208 X −0.627X= 10where X=log 10 (DPOM in cm)where DPOM is the diameter at the POM of the tree and H bole is the bole height of that stem (in m; i.e. up to thefirst major branch point except for palms where it is up to the base of the lowest living leaf sheath- see §1.5) 62 .Then sum (1) the surface areas of every stem >10 cm diameter and (2) 25 * the average over the ‘small trees’subplots of surface areas for small tree stems