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Harvard Forest Symposium Abstract 2007
- Title: Diel Trends in CO2 Efflux
- Primary Author: Kathleen Savage (Woods Hole Research Center)
- Abstract:
Diel patterns of soil respiration (SR) are clearly affected by the diel variation in soil temperature, but SR may also be affected by substrate supply that does not covary with soil temperature. Using an automated system, we collected high frequency temporal SR measurements in a well-drained deciduous stand at the Harvard forest, MA between May 17 and Nov 11, 2003 and in a well drained coniferous dominated stand at the Howland forest between May 4 and Nov 1, 2005. Our objective was to examine SR on a diel scale, focusing on trends in SR which covaryed with temperature and patterns in diel SR varying at a different diel trend. Using these observed SR data, we averaged hourly rates of SR over the sampling season to produce a diel trend in SR. We found that on a diel scale SR at both Harvard and Howland forest peaked in the early evening (~7-8pm), were at minimums in the early morning (~6-10am), and were not in sync with diel soil temperature patterns. Using a Q10 function derived from soil temperature at 10cm depth, we deconstructed the SR measurements into predicted SR, (SRp using the derived Q10 function) and residual SR (SRr which is SR-SRp). Patterns of diel SR, SRp and SRr were similar between the Harvard and Howland forest. There was a significant relationship between SRr and both air temperature and PAR when these variables were lagged 7-8 hrs at the Harvard forest and 8-12hrs lagged at the Howland Forest. It is suspected that this lag time, associated with SRr, is related to photosynthate transport time to the root systems. High frequency temporal SR measurements allow us to deconstruct the diel trend in SR into processes which 1. covary with soil temperature and 2. which appear to be linked to aboveground processes such as photosynthesis.
- Research Category:
