MLA-01 vertical and diurnal stem respiration campaign

Stem CO2 efflux, or stem respiration, measured vertically and diurnally within MLA-01 / Car-Bel, which is one of the SAFE Intensive Carbon Plots, part of the Global Ecosystem Monitoring (GEM) network, see http://gem.tropicalforests.ox.ac.uk/ located within Maliau Basin Conservation Area. Stem respiration was measured on 13 trees vertically and 18 trees diurnally during May 2023. The stem respiration data collected for this campaign can be linked to other data (census, species, traits) collected from the same stems by the stem tag number. For vertical measurements, stem respiration was measured by tree climbers using the static chamber technique. A 10 cm PVC collar with a 10.6 cm internal diameter was attached to the tree using ratchet straps and hose clips, and modelling clay was used to create an airtight seal around the collar. Stem respiration is then measured with an EGM-4 infrared CO2 gas analyser and SRC-1 respiration chamber (PP Systems) to the collar. Prior to commencing each measurement, the chamber was flushed, and collar fanned to remove stagnant air and the collar was checked for leakage. The chamber is then placed onto the collar and CO2 efflux is measured for 120 seconds. Over the 120 seconds, CO2 accumulates in the chamber and the uncorrected CO2 flux (ppm s-1) is calculated by the IRGA by fitting a linear regression between CO2 concentration and time (mean R2 = 0.954). Flux is calculated from the linear change in concentration in the chamber headspace, and corrected for collar height and air temperature, using the constants: 0.106 = Collar diameter, m 0.008824734 = Collar area, m2 0.10 = Collar height, m 0.0012287 = Chamber volume, incl. top part of the adapter (as in GEM manual) 0.000441237 = Extra airspace of the collar, m3 0.00211124 = Total chamber headspace, m3 101,325 = pressure 8.314472 = R (gas constant) 273.15 = Temperature to Kelvins 12.01 = Molar mass of carbon pV=nRT ideal gas law n=pV/(RT) n=m/M mass mole m=n*M m=MpV/(RT) For diurnal champaign, measurements were conducted over 48-hours per group, except for group A, which was measured for 72-hours. On each sampled stem, a 7 cm PVC collar with a 10.6 cm internal diameter was installed at 1.1 m height with silicone sealant. EA was measured every hour using a LiCOR Li8100A infrared gas analyser and LiCOR Li8150 multiplexer with 15 m extension cables, powered by a 100-ah car battery. The equipment was configured to operate as a closed, self-flushing multiplexed system. To create a closed system, plastic caps with a 11 cm diameter, fitted with in and out push fittings, were secured to the plastic collars, and connected to the LiCOR system using 15 m extension cables. Each measurement duration was 3-minutes, with 90-second dead band and flushed with ambient air between observations. Over the 3-minute interval, CO2 accumulates inside the system and the CO2 flux is calculated as the linear change in CO2 concentration within SoilFluxPro. During the diurnal campaign, temperature and humidity were measured continuously using Tinytag data loggers (TGP-4500; Gemini).

Authors

• Mills, Maria — University of Leicester
• Riutta, Terhi — University of Oxford, Imperial College London
• Shenkin, Alexander — University of Oxford, Norther Arizona University

Keywords

• Stem respiration
• diurnal respiration
• respiration vertical profile

Funders

• Central England NERC Training Alliance (NE/S007350/1)

Permits

• Research — Sabah Biodiversity Centre (SABC) (JKM/MBS.1000-2/2 JLD.16 (4))

Worksheets

Files

• 14408902_GEMINI.xml
• MLA-01_StemResp_Vertical_Diurnal.xlsx

Taxa

59 GBIF taxa, 0 sequence-derived taxa.