Journal Article

Linking carbon supply to root cell-wall chemistry and mechanics at high altitudes in <i>Abies georgei</i>

Marie Genet, Mingcai Li, Tianxiang Luo, Thierry Fourcaud, Anne Clément-Vidal and Alexia Stokes

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 107, issue 2, pages 311-320
Published in print February 2011 | ISSN: 0305-7364
Published online December 2010 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq237
Linking carbon supply to root cell-wall chemistry and mechanics at high altitudes in Abies georgei

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

The mobile carbon supply to different compartments of a tree is affected by climate, but its impact on cell-wall chemistry and mechanics remains unknown. To understand better the variability in root growth and biomechanics in mountain forests subjected to substrate mass movement, we investigated root chemical and mechanical properties of mature Abies georgei var. smithii (Smith fir) growing at different elevations on the Tibet–Qinghai Plateau.

Methods

Thin and fine roots (0·1–4·0 mm in diameter) were sampled at three different elevations (3480, 3900 and 4330 m, the last corresponding to the treeline). Tensile resistance of roots of different diameter classes was measured along with holocellulose and non-structural carbon (NSC) content.

Key Results

The mean force necessary to break roots in tension decreased significantly with increasing altitude and was attributed to a decrease in holocellulose content. Holocellulose was significantly lower in roots at the treeline (29·5 ± 1·3 %) compared with those at 3480 m (39·1 ± 1·0 %). Roots also differed significantly in NSC, with 35·6 ± 4·1 mg g−1 dry mass of mean total soluble sugars in roots at 3480 m and 18·8 ± 2·1 mg g−1 dry mass in roots at the treeline.

Conclusions

Root mechanical resistance, holocellulose and NSC content all decreased with increasing altitude. Holocellulose is made up principally of cellulose, the biosynthesis of which depends largely on NSC supply. Plants synthesize cellulose when conditions are optimal and NSC is not limiting. Thus, cellulose synthesis in the thin and fine roots measured in our study is probably not a priority in mature trees growing at very high altitudes, where climatic factors will be limiting for growth. Root NSC stocks at the treeline may be depleted through over-demand for carbon supply due to increased fine root production or winter root growth.

Keywords: Abies georgei; biomechanics; tensile resistance; cellulose content; non-structural carbon; root strength; Tibet–Qinghai; slope stability

Journal Article.  6895 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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