A simple technique to measure stem respiration using a horizontally oriented soil chamber

This paper introduces a simple technique, the horizontally oriented soil chamber (HOSC), to measure stem and branch respiration easily and accurately. We extend the function of the LI-6400-09 soil CO2 flux chamber by attaching a custom-built polyvinyl chloride (PVC) collar to the stem surface. For small trees and branches we use pipe bushings to connect the chamber to stem surface. Using this technique we measured stem respiration in a young ponderosa pine (Pinus ponderosa Dougl. ex Laws.) plantation in the Sierra Nevada Mountains near Georgetown, Calif., from June to December 1998. The diurnal and seasonal variations in respiration rate correlate well with the corresponding stem temperature variation. The Q10 values varied from 1.9 to 2.8, which are within the range of Q10 values (1.3-3.3) reported in previous studies. The range of our stem respiration results (3.5-7.2 µmol·m-2·s-1) compares favorably with previous studies on young ponderosa pine trees. This technique provides an alternative to measure stem respiration, which employs widely used, commercially available, portable respiration measurement equipment and requires almost no additional equipment, especially for current owners of LI-6400 systems. Thus, the HOSC technique is appropriate for examining spatial variation of stem respiration.