© 2007 Heron Publishing—Victoria, Canada
No diurnal variation in rate or carbon isotope composition of soil respiration in a boreal forest
Nicholas R. Betson (1), Sabine G. Göttlicher (1), Marianne Hall (2), Göran Wallin (2), Andreas Richter (3) and Peter Högberg (1,4)
1. Section of Soil Science, Department of Forest Ecology, SLU, SE-901 83, Umeå, Sweden / 2. Department of Plant and Environmental Science, University of Göteborg, SE-405 30, Göteborg, Sweden / 3. Department of Chemical Ecology & Ecosystem Research, University of Vienna, A-1090 Vienna, Austria / 4. Corresponding author (peter.hogberg@sek.slu.se) / Received March 10, 2006; accepted June 7, 2006; published online February 1, 2007
Summary
Characterization of soil respiration rates and δ13C values of soil-respired CO2 are often based on measurements at a particular time of day. A study by Gower et al. (2001) in a boreal forest demonstrated
diurnal patterns of soil CO2 flux using transparent measurement chambers that included the understory vegetation. It is unclear whether these diurnal
patterns were solely the result of photosynthetic CO2 uptake during the day by the understory or whether there were underlying trends in soil respiration, perhaps driven by plant
root allocation, as recently demonstrated in Mediterranean oak savannah.
We undertook intensive sampling campaigns in a boreal Picea abies L. Karst. forest to investigate whether diurnal variations in soil respiration rate and stable carbon isotope ratio (δ13C) exist in this ecosystem when no understory vegetation is present in the measurement chamber. Soil respiration rates and
δ13C were measured on plots in which trees were either girdled (to terminate the fraction of soil respiration directly dependent
on recent photosynthate from the trees), or not girdled, every 4 h over two 48-hour cycles during the growth season of 2004.
Shoot photosynthesis and environmental parameters were measured concurrently.
No diurnal patterns in soil respiration rates and δ13C were observed in either treatment, despite substantial variations in climatic conditions and shoot photosynthetic rates
in non-girdled trees. Consequently, assessment of daily soil respiration rates and δ13C in boreal forest systems by single, instantaneous daily measurements does not appear to be confounded by substantial diurnal
variation.
Keywords:
Picea abies L., (diurnal) soil respiration, spatial variation, tree girdling.
