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- Title
The carbon charging of pines at the climatic treeline: a global comparison.
- Authors
Hoch, Günter; Körner, Christian
- Abstract
The carbon charging of pines across the treeline ecotone of three different climatic zones (Mexico 19°N Pinus hartwegii, Swiss Alps 46°N P. cembra and northern Sweden 68°N P. sylvestris) was analyzed, to test whether a low-temperature-driven carbon shortage can explain high-elevation tree limits, and whether the length of the growing season affects the trees' carbon balance. We quantified the concentrations of non-structural carbohydrates (NSC) and lipids (acylglycerols) in all tree organs at three dates during the growing seasons across elevational transects from the upper end of the closed, tall forest (timberline) to the uppermost location where groups of trees ≥3 m in height occur (treeline). Mean ground temperatures during the growing season at the treelines were similar (6.1±0.7°C) irrespective of latitude. Across the individual transects, the concentrations of NSC and lipids increased with elevation in all organs. By the end of the growing season, all three species had very similar total mobile carbon (TMC) concentrations at the treeline (ca. 6% TMC in the aboveground dry biomass), suggesting no influence of the length of the growing season on tree carbon charging. At a temperate lowland reference site P. sylvestris reached only ca. 4% TMC in the aboveground dry biomass, with the 2% difference largely explained by higher lipid concentrations of treeline pines. We conclude that carbon availability is unlikely to be the cause of the altitudinal tree limit. It seems rather that low temperatures directly affect sink activity at the treeline, with surplus carbon stored in osmotically inactive compounds.
- Subjects
CARBOHYDRATES; LIPIDS; CONIFERS; GYMNOSPERMS; MOUNTAIN plants; PLANT growth
- Publication
Oecologia, 2003, Vol 135, Issue 1, p10
- ISSN
0029-8549
- Publication type
Article
- DOI
10.1007/s00442-002-1154-7