Turnover of grassland roots in mountain ecosystems revealed by their radiocarbon signature: role of temperature and management

PLoS One. 2015 Mar 3;10(3):e0119184. doi: 10.1371/journal.pone.0119184. eCollection 2015.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agriculture
  • Altitude
  • Carbon / chemistry*
  • Carbon Cycle*
  • Carbon Radioisotopes
  • Climate Change
  • Europe
  • Grassland
  • Humans
  • Models, Statistical*
  • Plant Roots / chemistry
  • Plant Roots / metabolism*
  • Poaceae / chemistry
  • Poaceae / metabolism*
  • Soil / chemistry*
  • Temperature

Substances

  • Carbon Radioisotopes
  • Soil
  • Carbon

Grants and funding

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). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.