Notes on the forest soil respiration measurement by a Li-6400 system

Abstract

The correct method used in forest soil respiration measurement by Li-6400 is a premise of data quality control. According to the study in a larch plantation, collars should be inserted at 12 hours in advance to efficiently reduce the influence of CO₂ spring-out. Moreover, collar insertion depth substantially affected soil respiration measurement, i.e., when collar was shallowly inserted into soil, transversal gas diffusion and the CO₂ re-spring-out caused by unstable collars in the measurement could lead to overestimating soil respiration rate; however, when collar was deeply inserted into soil, root respiration decline caused by root-cut and the most active respiratory of the surface soil separated by the inserted collars could lead to underestimating soil respiration rate. Furthermore, an error less than 5% could be guaranteed in typical sunny day if the target [CO₂] was set to the mean value of ambient [CO₂] in most time of the day, but it should be carefully set in early morning and late afternoon according to changing ambient [CO₂]. This protocol of measurement is useful in real measurement.

Keywords

Li-6400 / Soil respiration / Collar insertion depth / CO₂ / spring-our effect / Gas transversal diffusion / Factory parameter selection / S151.91 / A

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