STANDARDIZED STATIC-CHAMBER PROTOCOL FOR MEASURING SOIL CO₂, CH₄, AND N₂O FLUXES IN TROPICAL ENVIRONMENTS

Abstract

Static chambers are widely used to quantify soil–atmosphere exchanges of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), but methodological inconsistencies can affect flux estimates and data comparability. This Technical Note describes and standardizes the protocol adopted by the Laboratory of Research in Environmental Biogeochemistry (LAPBio, INPE) for greenhouse gas measurements in tropical soils using non-flow-through, non-steady-state static chambers. The procedure integrates chamber design and installation, discrete gas sampling at 1, 10, 20, and 30 min after closure, chromatographic determination, multipoint calibration, chamber-specific flux calculation, and quality-control criteria. Fluxes are estimated by least-squares regression using actual elapsed sampling times and corrected according to effective headspace volume, enclosed soil area, atmospheric pressure, and chamber-headspace temperature. Regression diagnostics, chromatographic performance, field records, and gas-specific minimum detectable fluxes are jointly considered during validation. The protocol provides a standardized and traceable methodological reference for future studies of soil CO₂, CH₄, and N₂O fluxes under tropical field conditions.