© 2004 Heron Publishing—Victoria, Canada
Seasonal and annual changes in soil respiration in relation to soil temperature, water potential and trenching
M. B. Lavigne (1, 2), R. J. Foster (1) and G. Goodine (1)
1. Natural Resources Canada, Canadian Forest Service - Atlantic Forestry Centre, Fredericton, NB E3B 5P7, Canada / 2. Corresponding author (mlavigne@nrcan.gc.ca) / Received April 7, 2003; accepted September 13, 2003; published online February 2, 2004
Summary
Soil respiration (rs), soil temperature (Ts) and volumetric soil water content were measured in a balsam fir (Abies balsamea (L.) Mill.) ecosystem from 1998 to 2001. Seasonal variation in root and microbial respiration, and covariation in abiotic
factors confounded interpretation of the effects of Ts and soil water potential (Ψs) on rs. To minimize the confounding effect of temperature, we analyzed the effect of Ψs on rs during the summers of 1998–2000 when changes in Ts were slight. Soil respiration declined 25–50% in response to modest water stress (minimum Ψs of –0.6 to –0.2 MPa), and between years, there was substantial variation in the relationship between rs and Ψs. In the summer of 2000, 2-m2 plots were subjected to drought for 1 month and other plots were irrigated. The relationship between summertime rs and Ψs in the experimental plots was similar to that estimated from the survey data obtained during the same summer. In late spring
and early autumn of 2001, 2-m2 trenched and untrenched plots were subjected to drought or exposed to rainfall. It was dry in the early autumn and there
was severe soil drying (Ψs of –10 MPa in untrenched plots and –2 MPa in trenched plots). In spring, rs in untrenched plots responded more to modest water stress than rs in trenched plots, indicating that root respiration is more sensitive than microbial respiration to water stress at this
time of year. The response to abiotic factors differed significantly between spring and autumn in untrenched plots but not
in trenched plots, indicating that root activity was greater in early autumn than in late spring, and that roots acclimated
to the sustained, severe water stress experienced before and during the autumn.
Keywords:
Abies balsamea, abiotic control, interannual variation, seasonal variation, trenched plots.
