Investigating the relationship between tree stem respiration and growth rate

Abstract

This study was conducted at the Maliau Basin Conservation area (4.747°, 116.970°) in an old-growth forest, the Belian plot. The sample consisted of ten trees of variety of species and a range of growth rates. Sampling took place over 3 consecutive days (18/02/2020 - 20/02/2020) to compile a 24-hour cycle due to logistical constrains impeding continuous measurement. Stem Respiration was measured hourly using a closed chamber EGM-4 Infrared Gas Analyser. Each tree has a 5cm long PVC collar with a 10.6cm internal diameter sealed with glue at 1.1m height. For each measurement, the chamber was flushed and collar fanned to remove stagnant air. The chamber was then sealed onto the PVC collar and Rs measured for 120 seconds. The raw measurements provides CO2 concentration (ppm), the results were then downloaded and filtered to remove initial stabilisation period and outliers using the R package "egm_r_tools" (see https://github.com/davidorme/egm_r_tools), with the ideal measurement being a linear slope with minimal residuals. The filtered efflux slope for each tree was then scaled to hourly and summed to give a daily total per tree. Out of the 24-hour period, two hour slots were missing (14:00 and 04:00) due to logistical constraints .

This study was conducted at the Maliau Basin Conservation area (4.747°, 116.970°) in an old-growth forest, the Belian plot. The sample consisted of ten trees of variety of species and a range of growth rates. Sampling took place over 3 consecutive days (18/02/2020 - 20/02/2020) to compile a 24-hour cycle due to logistical constrains impeding continuous measurement. Stem Respiration was measured hourly using a closed chamber EGM-4 Infrared Gas Analyser. Each tree has a 5cm long PVC collar with a 10.6cm internal diameter sealed with glue at 1.1m height. For each measurement, the chamber was flushed and collar fanned to remove stagnant air. The chamber was then sealed onto the PVC collar and Rs measured for 120 seconds. The raw measurements provides CO2 concentration (ppm), the results were then downloaded and filtered to remove initial stabilisation period and outliers using the R package "egm_r_tools" (see https://github.com/davidorme/egm_r_tools), with the ideal measurement being a linear slope with minimal residuals. The filtered efflux slope for each tree was then scaled to hourly and summed to give a daily total per tree. Out of the 24-hour period, two hour slots were missing (14:00 and 04:00) due to logistical constraints .