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Notes:
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Root turnover is an important carbon flux component in grassland ecosystems because it
replenishes substantial parts of carbon lost from soil via heterotrophic respiration and leaching.
Among the various methods to estimate root turnover, the root’s radiocarbon signature
has rarely been applied to grassland soils previously, although the value of this approach is
known from studies in forest soils. In this paper, we utilize the root’s radiocarbon signatures,
at 25 plots, in mountain grasslands of the montane to alpine zone of Europe.We place the
results in context of a global data base on root turnover and discuss driving factors. Root
turnover rates were similar to those of a subsample of the global data, comprising a similar
temperature range, but measured with different approaches, indicating that the radiocarbon
method gives reliable, plausible and comparable results. Root turnover rates (0.06–1.0 y-1)
scaled significantly and exponentially with mean annual temperatures. Root turnover rates
indicated no trend with soil depth. The temperature sensitivity was significantly higher in
mountain grassland, compared to the global data set, suggesting additional factors influencing
root turnover. Information on management intensity from the 25 plots reveals that root
turnover may be accelerated under intensive and moderate management compared to low
intensity or semi-natural conditions. Because management intensity, in the studied ecosystems,
co-varied with temperature, estimates on root turnover, based on mean annual temperature
alone, may be biased. A greater recognition of management as a driver for root
dynamics is warranted when effects of climatic change on belowground carbon dynamics
are studied in mountain grasslands.
KB received support from the Swiss National Science Foundation, project 200021-115891 (www.snf.ch). SM received support from the Swiss State Secretariat for Education and Research, project C07.0031 (www.sbfi.admin.ch). MTS received support from the Spanish Ministry of Science and Innovation, (project CAPAS, CGL2010-22378-C03- 01) (www.idi.mineco.gob.es). |
