The measurement of soil respiration with the enclosure-based methods, such as the accumulation chamber, is carried out using cameras that are opaque to solar radiation when only the component deriving from the biochemical reactions of the soil is to be measured, excluding the contribution of the photosynthetic activity. In nature, photosynthesis is a process used by plants and other organisms that allows for the synthesis of carbohydrates via use of the atmospheric carbon dioxide, water and energy provided by the Photosynthetically Active component of Solar Radiation (PAR).
The photosynthesis activity absorbs carbon dioxide and releases oxygen into the atmosphere with an overall balance of one mole of 02 for each mole of CO2 absorbed. In order to obtain an accurate assessment of the overall respiration of the soil and the plants it is necessary for the chamber to be as far as possible transparent to solar radiation in the PAR range between 400 and 700 nm. The WEST Systems accumulation chamber is made of poly (methyl methacrylate) (PMMA), a material that offers much greater transparency than any other material, such as glass or polycarbonates.
This chamber, which uses an innovative gas-mixing system internally without relying on any moving parts, incorporates a sensor for measuring the temperature, relative humidity and barometric pressure inside the chamber. The interface between the ground and the accumulation chamber has been designed to guarantee an absolute seal, with the use of an AISI 316 steel collar fitted with a toroidal gasket.
The collar is designed in such a way as to minimise the section protruding from the ground and therefore limit the projecting of shadows inside the measurement area even in the arctic areas where the sun is always low on the horizon.
Chamber height: 100 mm
Internal diameter: 290 mm
For the assessment of the overall respiration of the soil-vegetation system it is recommended to use a Portable FluxMeter in Enhanced configuration, with the measurement of the CO2, CH4, H2O, O2 and optionally VOC (Volatile Organic Compounds) flux rates. By using optional sensors, the Enhanced Portable Fluxmeter is also able to measure soil temperature, soil water content via the TDR technique, and the PAR component of the solar radiation, in addition to the total and net solar radiation.