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| Biomass below ground
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| Definition |
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The amount of living substance in a defined sample.
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| Rationale |
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The Biomass above and below ground are key variables in annual and long-term changes in the global terrestrial carbon cycle, and in modelling carbon uptake and redistribution within the ecosystem. Experimental evidence indicates that changes in atmospheric chemistry and climate will change carbon allocation patterns between the pools above and below ground. These pools will therefore not change in parallel as a response to global environmental change. The currently large but unidentified terrestrial carbon sink proposed by climate modellers and oceanographers may well eventually be found to be in biomass below ground.
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| Users |
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Terrestrial ecologists, ecosystem modellers, and decision-makers (e.g., for calculating carbon taxes, etc.).
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| Assessment method |
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Tiers 1-3: sampling; video cameras (fine roots; experimental).
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| Units of Measure |
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g/m2 or kg/ha
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| Frequency of measurement |
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From annually to every 5 to 10 years. Seasonal or monthly measurements may be taken in the case of centre and land experiments.
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| Spatial resolution |
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Tiers 1, 2, 3 and 4
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| Accuracy/precision required |
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±10%
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| Associated measurements |
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Biomass above ground is closely associated to this variable, both are required to define biomass distributions and increments, while neither alone would be of much value in understanding the terrestrial carbon cycle.
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| Present status |
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Data on biomass below ground is only available from a few sites around the world, most of which are associated with one-time experiments or with research stations. This is wholly inadequate for global monitoring and modelling change purposes.
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| R and D needed |
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- At the present time, there is insufficient theory on carbon allocation in plants growing under chronic environmental changes to predict biomass below ground increments from other variables (i.e., temporal patterns). There is also not enough data to define current spatial patterns and their relationship to other spatial variables.
- Currently, biomass below ground is determined from labour-intensive techniques involving extraction, drying and weighing of all roots in a given unit area. Beyond these techniques, it is uncertain how biomass data can be obtained efficiently for the modelling efforts within the next 5 years. Measurement techniques need to be developed to measure current and changes in biomass distribution through time.
- Encourage R and D on biomass estimation using the currently highly experimental radar imagery techniques.
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