Measuring Fine Root Turnover in Forest Ecosystems |
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Authors: | Hooshang Majdi Kurt Pregitzer Ann-Sofie Morén Jan-Erik Nylund Göran I Ågren |
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Institution: | (1) Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences, P.O. Box 7072, SE-750 07 Uppsala, Sweden;(2) Department of Forest Products and Markets, Swedish University of Agricultural Sciences, P.O. Box 7060, SE-750 07 Uppsala, Sweden;(3) School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, Michigan 49931, USA |
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Abstract: | Development of direct and indirect methods for measuring root turnover and the status of knowledge on fine root turnover in
forest ecosystems are discussed. While soil and ingrowth cores give estimates of standing root biomass and relative growth,
respectively, minirhizotrons provide estimates of median root longevity (turnover time) i.e., the time by which 50% of the
roots are dead. Advanced minirhizotron and carbon tracer studies combined with demographic statistical methods and new models
hold the promise of improving our fundamental understanding of the factors controlling root turnover. Using minirhizotron
data, fine root turnover (y−1) can be estimated in two ways: as the ratio of annual root length production to average live root length observed and as
the inverse of median root longevity. Fine root production and mortality can be estimated by combining data from minirhizotrons
and soil cores, provided that these data are based on roots of the same diameter class (e.g., < 1 mm in diameter) and changes
in the same time steps. Fluxes of carbon and nutrients via fine root mortality can then be estimated by multiplying the amount
of carbon and nutrients in fine root biomass by fine root turnover. It is suggested that the minirhizotron method is suitable
for estimating median fine root longevity. In comparison to the minirhizotron method, the radio carbon technique favor larger
fine roots that are less dynamics. We need to reconcile and improve both methods to develop a more complete understanding
of root turnover. |
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Keywords: | minirhizotron radio carbon technique root mortality root production root turnover soil cores statistical analysis |
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