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

3.4 Coarse woody debris (CWD) CO 2 effluxEquipment: IRGA and SRC, PVC collars (5 cm long and of a diameter to fit the SRC-1, see Appx. II), plasticsheet, strong adhesive tape, callipers, weighing balance (0.01 g resolution), drying ovenTake these measurements every two months (usually at the same time as the survey in §4.2). Collect 5representative wood pieces (~5 cm long, i.e. small enough to fit into a PVC collar without sticking out) of eachdecomposition category from each plot (5 pieces per category * 5 categories = 25 pieces per ha), and place inappropriately marked sealed plastic bags (site, plot, date, piece number). Seal one side of a plastic collar with aplastic sheet secured with tape. Then place each individual piece of wood into the collar, place the SRC firmlyonto the collar and commence IRGA measurement (Appx. II). Now measure for each wood piece: (1) wetweight, (2) dry weight, after drying to constant mass at 80 o C, (3) diameter and (4) length. Ensure that theidentity of each individual piece is noted, so that these measurements can be matched to the correspondingefflux value from the same piece.Decomposition Level (following Harmon et al.1995 71 )1 (little decay: bark cover extensive and leavesand fine twigs present)2 (logs and snags relatively undecayed but withno leaves and few fine twigs and bark has startedto fall off)3 (logs and snags with no bark and only a fewbranch stubs remaining; although in this class thesapwood is decaying, the heartwood is relativelyundecayed, and branch stubs do not move whenpushed or pulled)4 (no branches or bark cover; outer portions ofthe wood are often casehardened and the innerwood is decomposing)5 (logs are elliptical in cross-section (indicativeof advanced decay) and often the wood isscattered across the soil surfac)LeavespresentFinetwigspresentIntactbarkFirmwoodSoftwoodyes yes yes yes no nono no yes yes no nono no no yes no nono no no no yes nono no no no no yesVerysoftwoodThe mean difference between wet and dry weight for each decomposition category will provide a woodmoisture correction necessary for the previous section. Estimate the surface area of each piece using (2 *3.1416 * ((diameter/2) 2 )) + (2 * 3.1416 * (diameter/2) * length). Dry weight and surface area can then be usedto calculate CO 2 efflux per unit dry mass and surface area using the approach described above (also see Appx.II). These values may be scaled up to a per ha estimate of CO 2 flux using estimates of ground coarse litter massand surface area (see §4.2).71 n.b. these categories differ slightly from those in Baker & Chao (2011).61