Low-cost chamber design for simultaneous CO2 and O2 flux measurements between tree stems and the atmosphere

Abstract

Tree stem CO2 efflux is an important component of ecosystem carbon fluxes and has been the focus of many studies. While CO2 efflux can easily be measured, a growing number of studies have shown that it is not identical with actual in situ respiration. Complementing measurements of CO2 flux with simultaneous measurements of O2 flux provides an additional proxy for respiration, and the combination of both fluxes can potentially help getting closer to actual measures of respiratory fluxes. To date, however, the technical challenge to measure relatively small changes in O2 concentration against its high atmospheric background has prevented routine O2 measurements in field applications. Here we present a new and low-cost field-tested device for autonomous real-time and quasi-continuous long-term measurements of stem respiration by combining CO2 (NDIR based) and O2 (quenching based) sensors in a tree stem chamber. Our device operates as a cyclic closed system and measures changes in both CO2 and O2 concentration within the chamber over time. The device is battery-powered with a > 1 week power independence and data acquisition is conveniently achieved by an internal logger. Results from both field and laboratory tests document that our sensors provide reproducible measurements of CO2 and O2 exchange fluxes under varying environmental conditions.

Development of a lightweight, portable, waterproof, and low power stem respiration system for trees

“…This in turn reduces the CO 2 efflux and can therefore lead to underestimates of CO 2 efflux rates. Moreover, the method assumes a complete leak free enclosure where ambient air is prevented from entering the chamber by sealing the chamber to the stem with various glues [10] . However, small leaks, which are difficult to detect and quantify in the field, reduce the rate at which CO 2 accumulates in the stem chamber, and quickly become more significant with time as the CO 2 concentration inside the chamber rapidly increases above ambient air levels.…”

A Modeling Approach to Investigate Drivers, Variability and Uncertainties in O2 Fluxes and the O2 : CO2 Exchange Ratios in a Temperate Forest

“…The vegetation at the site is an even-aged managed beech stand (Fagus sylvatica L.) with an age of approximately 130 years (Tamrakar et al, 2018). The mean annual temperature was 8.3 ± 0.7 °C and the average cumulative annual precipitation was 600 ± 150 mm between 2002and 2016(Braden-Behrens et al, 2019.…”

“…Studies obtaining exchange ratios of O2 and CO2 via chamber measurements at the soil-or stem-scale often state the socalled apparent respiratory quotient (ARQ), which is defined as the ratio of CO2 efflux to O2 uptake (Angert et al, 2012;Helm et al, 2021;Hilman and Angert, 2016;Hilman et al, 2022). Thus, ARQ could be compared to our ERsoil or ERstem by taking the inverse of ARQ, which is the CO2:O2 conductance ratio, following Hilman and Angert (2016).…”

“…Studies obtaining exchange ratios of O2 and CO2 via chamber measurements at the soil-or stem-scale often state the socalled apparent respiratory quotient (ARQ), which is defined as the ratio of CO2 efflux to O2 uptake (Angert et al, 2012;Helm et al, 2021;Hilman and Angert, 2016;Hilman et al, 2022). Thus, ARQ could be compared to our ERsoil or ERstem by taking the inverse of ARQ, which is the CO2:O2 conductance ratio, following Hilman and Angert (2016). However, ARQ is also influenced by biotic and abiotic non-respiratory processes such as dissolution and refixation of respired CO2 in the xylem sap (Angert et al, 2012;Hilman and Angert, 2016;Hilman et al, 2022), so we expect differences between the various quantities.…”

Monitoramento da poluição do ar relacionado ao tráfego com o uso de sensores de baixo custo e estimativa da carga de poluentes inalada por ciclistas na cidade de São Paulo

“…O sensor de umidade e temperatura é o modelo SHT85 da marca Sensirion (Suíça) e é citado em alguns artigos (Helm et al, 2021;Salamone et al, 2022;Cowell et al, 2022), apresentando as características de resposta rápida e boa precisão. A Figura 48 mostra o sensor e suas dimensões (em mm).…”