High temporal resolution tracing of photosynthate carbon from the tree canopy to forest soil microorganisms.
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. Using (13)CO(2), we pulse-labelled over 1.5 h a 50-m(2) patch of 4-m-tall boreal Pinus sylvestris forest in a 200-m(3) chamber. 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 (15)NH(+)(4) showed that the ectomycorrhizal roots, which were the strongest sinks for photosynthate, were also the most active sinks for soil nitrogen. These observations highlight the close temporal coupling between tree canopy photosynthesis and a significant fraction of soil activity in forests.
Högberg
P
P
Department of Forest Ecology and Management, SLU, SE-901 83 Umeå, Sweden.
Högberg
M N
MN
Department of Forest Ecology and Management, SLU, SE-901 83 Umeå, Sweden.
Göttlicher
S G
SG
Department of Forest Ecology and Management, SLU, SE-901 83 Umeå, Sweden.
Betson
N R
NR
Department of Forest Ecology and Management, SLU, SE-901 83 Umeå, Sweden.
Keel
S G
SG
Department of Forest Ecology and Management, SLU, SE-901 83 Umeå, Sweden.
Metcalfe
D B
DB
Department of Forest Ecology and Management, SLU, SE-901 83 Umeå, Sweden.
Campbell
C
C
Department of Plant Physiology and Umeå Plant Science Centre, University of Umeå, SE-901 87 Umeå, Sweden.
Schindlbacher
A
A
Department of Forest and Soil Science, University of Natural Resources and Applied Life Sciences, BOKU, Peter Jordan-Strasse 82, A-1190 Vienna, Austria.
Hurry
V
V
Department of Plant Physiology and Umeå Plant Science Centre, University of Umeå, SE-901 87 Umeå, Sweden.
Lundmark
T
T
Unit for Field-based Forest Research, SLU, Vindeln Experimental Forests and Svartberget Research Station, SLU, SE-922 91 Vindeln, Sweden.
Linder
S
S
Southern Swedish Forest Research Centre, SLU, PO Box 49, SE-230 53 Alnarp, Sweden.
Näsholm
T
T
Department of Forest Genetics and Plant Physiology and Umeå Plant Science Centre, SLU, SE-901 87 Umeå, Sweden.
D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes; D017753:Ecosystem; D009584:Nitrogen / Q000378:metabolism; D009587:Nitrogen Isotopes; D041605:Pinus sylvestris / Q000378:metabolism; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D013997:Time Factors; D014197:Trees / Q000378:metabolism*
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen