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CO2 enrichment alters diurnal stem radius fluctuations of 36-yr-old Larix decidua growing at the alpine tree line.

Authors
Type
Published Article
Journal
New Phytologist
1469-8137
Publisher
Wiley Blackwell (Blackwell Publishing)
Publication Date
Volume
202
Issue
4
Pages
1237–1248
Identifiers
DOI: 10.1111/nph.12742
PMID: 24571288
Source
Medline
Keywords
License
Unknown

Abstract

To understand how trees at high elevations might use water differently in the future, we investigated the effects of CO2 enrichment and soil warming (separately and combined) on the water relations of Larix decidua growing at the tree line in the Swiss Alps. We assessed diurnal stem radius fluctuations using point dendrometers and applied a hydraulic plant model using microclimate and soil water potential data as inputs. Trees exposed to CO2 enrichment for 9 yr showed smaller diurnal stem radius contractions (by 46 ± 16%) and expansions (42 ± 16%) compared with trees exposed to ambient CO2 . Additionally, there was a delay in the timing of daily maximum (40 ± 12 min) and minimum (63 ± 14 min) radius values for trees growing under elevated CO2 . Parameters optimized with the hydraulic model suggested that CO2 -enriched trees had an increased flow resistance between the xylem and bark, representing a more buffered water supply system. Soil warming did not alter diurnal fluctuation dynamics or the CO2 response. Elevated CO2 altered the hydraulic water flow and storage system within L. decidua trees, which might have contributed to enhanced growth during 9 yr of CO2 enrichment and could ultimately influence the future competitive ability of this key tree-line species.

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