High temporal resolution tracing of photosynthate carbon from the tree canopy to forest soil microorganisms
New Phytologist: 2008 177:220-228
Abstract
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Half of the biological activity in forest soils is supported by recent tree photosynthate, but no study has traced in detail this flux of carbon from the canopy to soil microorganisms in the field. |
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Using 13CO2, we pulse-labelled over 1.5 h a 50-m2 patch of 4-m-tall boreal Pinus sylvestris forest in a 200-m3 chamber. |
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Tracer
levels peaked after 24 h in soluble carbohydrates in the phloem at a
height of 0.3 m, after 2–4 d in soil respiratory efflux, after 4–7 d in
ectomycorrhizal roots, and after 2–4 d in soil microbial cytoplasm.
Carbon in the active pool in needles, in soluble carbohydrates in
phloem and in soil respiratory efflux had half-lives of 22, 17 and
35 h, respectively. Carbon in soil microbial cytoplasm had a half-life
of 280 h, while the carbon in ectomycorrhizal root tips turned over
much more slowly. Simultaneous labelling of the soil with |
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These observations highlight the close temporal coupling between tree canopy photosynthesis and a significant fraction of soil activity in forests. |