Carbon allocation between tree root growth and root respiration in boreal pine forest
Peter Högberg1, Anders Nordgren1, Göran I Ågren2
1Department of Forest Ecology, Section of Soil Science, SLU, 901 83, Umeå, Sweden.
Oecologia
|May 27, 2017
Summary
Soil respiration is a key part of ecosystem carbon balance. This study suggests tree root growth and turnover rates were overestimated in past research, with most carbon allocated to roots being respired, not used for growth.
Area of Science:
- Ecology
- Forestry
- Biogeochemistry
Background:
- Soil respiration significantly impacts ecosystem carbon budgets, encompassing respiration from mycorrhizal roots and decomposition by heterotrophic organisms.
- A long-standing paradigm suggested high tree fine root biomass turnover rates, limiting the perceived contribution of root respiration to the overall carbon balance.
Purpose of the Study:
- To re-evaluate the contribution of root respiration to ecosystem carbon budgets.
- To assess the accuracy of previous estimations of root growth and turnover in coniferous forests.
Main Methods:
- Combined data from a recent tree girdling experiment with the carbon budget from the Swedish Coniferous Forest (SWECON) project.
- Analyzed the relationship between root respiration and heterotrophic respiration.
Main Results:
- High root turnover rates, as previously estimated, necessitate an improbably high carbon use efficiency for root growth.
- A 1:1 ratio between root and heterotrophic respiration, observed in the girdling experiment, contradicts high root turnover estimates.
- Analysis indicates approximately 75% of carbon allocated to roots is respired, with only 25% used for growth.
Conclusions:
- Previous estimates of root growth and turnover in the SWECON project were likely significantly overestimated.
- Root respiration plays a more substantial role in ecosystem carbon cycling than previously assumed based on high turnover rates.
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