Baseline Subsoil CO2 Gas Measurements and Micrometeorological Monitoring: Above Canopy Turbulence Effects on the Subsoil CO2 Dynamics in Temperate Deciduous Forest

Didi Adisaputro,Laurent Saint-Andre,Philippe De Donato,Catherine Galy,Marion Derrien,Médéric Piedevache,Odile Barres,Gilles Nourrisson

doi:10.3390/app11041753

Abstract

Accurate and continuous measurement of the subsoil CO2 is critical to better understand the terrestrial and atmosphere gas transfer process. This work aims to develop and field test a specific flow system to continuously measure the soil gas concentration (χc) and understand its main physical drivers. Hourly data measured in situ were collected through two dedicated wells at 1 m and 6 m depth coupled with micrometeorological measurement. Our study shows that χc at -1 m was at the lowest in winter and highest in summer. Meanwhile, the seasonal variation of χc at -6m is somewhat unclear. While it is inevitable that temperature plays a significant role, this factor related to biological activity cannot fully explain the variation. The decrease in χc at both depths in summer coincides with an increase of friction velocity, especially during dry periods with R2 of 0.68, which shows strong empirical evidence that wind turbulence plays a significant role in driving the deep soil CO2. A monitoring strategy for gas measurement combining borehole and micrometeorological measurement offers excellent long-term monitoring possibilities to derive the vertical distribution of CO2 and better understand the main physical drivers of gas exchange.

Highlights

Adequate and trustworthy monitoring strategies of natural gas exchange will help understand the local variability of gas concentration in the soil, e.g., in anticipation of the CO2 injection [4,5]
The main objectives of this study are three-fold; (i) To develop and field test a specific flow system equipped with a membrane probe to continuously measure the soil gas concentration and auxiliaries data; (ii) to combine borehole with micrometeorological monitoring; (iii) to understand the main physical drivers of gas exchange in a deep soil layer (−6 m) and a shallow soil layer (−1 m) regardless of the water saturation conditions
1. 06x calibration procedure consists of 11 measurement for

Summary

Introduction

The gas exchange between the atmosphere and terrestrial ecosystem represents a large proportion of CO2 and CH4 atmospheric budgets [1]. Soil CO2 budget and efflux due to land-use change averaged globally from 2009–2018 were estimated at 5496–8793.6 PgCO2 and 5.49 PgCO2 yr−1 respectively [2], as for the comparison, the emission due to fossil fuel combustion and the cement industry is around 33.4 PgCO2 yr−1 [3]. Promote public acceptability [6], or for ecological studies on terrestrial greenhouse gases emissions [3,7,8,9]. GHG (Greenhouse gasses) emissions from the soils 4.0/). The most widely used approaches in this context are chambers methods (soil-air interface) [1,10,11,12], micrometeorological eddy covariance method (vegetation-atmosphere interface) [9,13,14,15], and the gradient method (subsoil gas transport) [1,12,16,17,18,19]

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Conclusion