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Temperature and moisture dependence of daily growth of Scots pine ( Pinus sylvestris L.) roots in Southern Finland

Authors
  • Ding, Yiyang1
  • Schiestl-Aalto, Pauliina1, 2, 3
  • Helmisaari, Heljä-Sisko1
  • Makita, Naoki4
  • Ryhti, Kira1, 2
  • Kulmala, Liisa1, 2, 5
  • 1 Department of Forest Sciences, Finland , (Finland)
  • 2 Institute for Atmospheric Sciences and Earth System Research (INAR)/Forest sciences, Finland , (Finland)
  • 3 Department of Forest Ecology and Management, Sweden , (Sweden)
  • 4 Faculty of Science, Japan , (Japan)
  • 5 Finnish Meteorological Institute, Finland , (Finland)
Type
Published Article
Journal
Tree Physiology
Publisher
Oxford University Press
Publication Date
Dec 20, 2019
Volume
40
Issue
2
Pages
272–283
Identifiers
DOI: 10.1093/treephys/tpz131
PMID: 31860713
PMCID: PMC7048678
Source
PubMed Central
Keywords
License
Unknown

Abstract

Scots pine ( Pinus sylvestris L.) is one of the most important conifers in Northern Europe. In boreal forests, over one-third of net primary production is allocated to roots. Pioneer roots expand the horizontal and vertical root systems and transport nutrients and water from belowground to aboveground. Fibrous roots, often colonized by mycorrhiza, emerge from the pioneer roots and absorb water and nutrients from the soil. In this study, we installed three flatbed scanners to detect the daily growth of both pioneer and fibrous roots of Scots pine during the growing season of 2018, a year with an unexpected summer drought in Southern Finland. The growth rate of both types of roots had a positive relationship with temperature. However, the relations between root elongation rate and soil moisture differed significantly between scanners and between root types indicating spatial heterogeneity in soil moisture. The pioneer roots were more tolerant to severe environmental conditions than the fibrous roots. The pioneer roots initiated elongation earlier and ceased it later than the fibrous roots. Elongation ended when the temperature dropped below the threshold temperature of 4 °C for pioneer roots and 6 °C for fibrous roots. During the summer drought, the fibrous roots halted root surface area growth at the beginning of the drought, but there was no drought effect on the pioneer roots over the same period. To compare the timing of root production and the aboveground organs’ production, we used the CASSIA model, which estimates the aboveground tree carbon dynamics. In this study, root growth started and ceased later than growth of aboveground organs. Pioneer roots accounted for 87% of total root productivity. We suggest that future carbon allocation models should separate the roots by root types (pioneer and fibrous), as their growth patterns are different and they have different reactions to changes in the soil environment.

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