A Method for Estimating Annual Cumulative Soil/Ecosystem Respiration and CH4 Flux from Sporadic Data Collected Using the Chamber Method

Abstract

Measurements of greenhouse gas fluxes over many ecosystems have been made as part of the attempt to quantify global carbon and nitrogen cycles. In particular, annual flux observations are of great value for regional flux assessments, as well as model development and optimization. The chamber method is a popular approach for soil/ecosystem respiration and CH4 flux observations of terrestrial ecosystems. However, in situ flux chamber measurements are usually made with non-continuous sampling. To date, efficient methods for the application of such sporadic data to upscale temporally and obtain annual cumulative fluxes have not yet been determined. To address this issue, we tested the adequacy of non-continuous sampling using multi-source data aggregation. We collected 330 site-years monthly soil/ecosystem respiration and 154 site-years monthly CH4 flux data in China, all obtained using the chamber method. The data were randomly divided into a training group and verification group. Fluxes of all possible sampling months of a year, i.e., 4094 different month combinations were used to obtain the annual cumulative flux. The results showed a good linear relationship between the monthly flux and the annual cumulative flux. The flux obtained during the warm season from May to October generally played a more important role in annual flux estimations, as compared to other months. An independent verification analysis showed that the monthly flux of 1 to 4 months explained up to 67%, 89%, 94%, and 97% of the variability of the annual cumulative soil/ecosystem respiration and 92%, 99%, 99%, and 99% of the variability of the annual cumulative CH4 flux. This study supports the use of chamber-observed sporadic flux data, which remains the most commonly-used method for annual flux estimating. The flux estimation method used in this study can be used as a guide for designing sampling programs with the intention of estimating the annual cumulative flux.

Soil carbon flux research in the Asian region: Review and future perspectives

“…However, the development of a compact and commercially feasible CH 4 analyser has enabled continuous field measurements for soil CH 4 flux. At present, such analysers have employed laser-based technology e.g., cavity ring-down spectroscopy for use in field measurement for soil GHG flux for several natural ecosystems Dhandapani et al, 2019 . In addition, several recent studies in the Asian region have conducted continuous measurements of soil CH 4 flux using the CH 4 analyser and AOCC systems Sakabe et al, 2015;Ueyama et al, 2015;Ishikura et al, 2019 . To fully utilise the sporadic measurement data to estimate the annual cumulative flux of soil CH 4 , Yang et al 2019a developed equations using 154 site-years monthly CH 4 flux data measured using the chamber methods in China. Such an approach will contribute to the improved estimation of the regional and global soil CH 4 flux.…”

“…For this analysis, we used open data sources Wang and Fang, 2009;Bond-Lamberty and Thomson, 2018;Feng et al, 2018;Steele and Jian, 2018;Mei et al, 2019;Yang et al, 2019a . In arid and semi-arid environments, biological soil crusts significantly influence ecological processes, including soil C flux.…”

“…Of all ecosystem types, the greatest number of observations on C flux have been made in these forests. Measurements using the chamber method from 174 sites have produced approximately 468 annual R s records Bond-Lamberty and Thomson, 2018;Steele and Jian, 2018;Yang et al, 2019a . Although there are a lower number of CH 4 flux observations compared to their CO 2 counterparts, at least 230 annual records may be obtained from the published literature Morishita et al, 2007;Wang et al, 2014c;Ni and Groffman, 2018;Yang et al, 2019a . As shown in , Tian et al, 2015 . An evaluation of the temporal variation suggests that the R s in temperate forests in Asia was higher in the 1960s and 1970s and decreased to the lowest rate in the 1990s Table 5 .…”

Carbon Dynamics in Rewetted Tropical Peat Swamp Forests

“…The flux rate was calculated from the concentration change rate in the chamber headspace, determined by the slope of a linear regression of gas concentration and converted to a mass unit using the ideal gas equation [44]. The R h and CH 4 fluxes from the measurement were converted into annual cumulative data using equations for two months of data [49]. The CH 4 flux data were only collected from the non-trenched plot.…”

Comparing GHG Emissions from Drained Oil Palm and Recovering Tropical Peatland Forests in Malaysia

“…These variables were measured from July 2017 to September 2018 at the OP and NF sites, and from July 2017 to October 2018 at the RF site. Greenhouse gases were sampled using the static closed-chamber method [52] every two weeks, between 11:00 and 14:00 h on each sampling day, from July 2017 to December 2018 at the OP and RF sites and from July 2017 to September 2018 at the NF site because, after that date, the sampling site became inaccessible due to flooding. The static closed-chamber method has a clear advantage over other methods in that it is the only operational method that can obtain temporal measurements of trace gas fluxes at a large number of plots spread across a large area, as well as yielding information on the short-distance spatial variability of trace gas fluxes [53].…”