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Nitrogen and carbon source–sink relationships in trees at the Himalayan treelines compared with lower elevations

Nitrogen and carbon source–sink relationships in trees at the Himalayan treelines compared with... ABSTRACT No single hypothesis or theory has been widely accepted for explaining the functional mechanism of global alpine/arctic treeline formation. The present study tested whether the alpine treeline is determined by (1) the needle nitrogen content associated with photosynthesis (carbon gain); (2) a sufficient source–sink ratio of carbon; or (3) a sufficient C–N ratio. Nitrogen does not limit the growth and development of trees studied at the Himalayan treelines. Levels of non‐structural carbohydrates (NSC) in trees were species‐specific and site‐dependent; therefore, the treeline cases studied did not show consistent evidence of source/carbon limitation or sink/growth limitation in treeline trees. However, results of the combined three treelines showed that the treeline trees may suffer from a winter carbon shortage. The source capacity and the sink capacity of a tree influence its tissue NSC concentrations and the carbon balance; therefore, we suggest that the persistence and development of treeline trees in a harsh alpine environment may require a minimum level of the total NSC concentration, a sufficiently high sugar:starch ratio, and a balanced carbon source–sink relationship. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Cell & Environment Wiley

Nitrogen and carbon source–sink relationships in trees at the Himalayan treelines compared with lower elevations

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References (59)

Publisher
Wiley
Copyright
© 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd
ISSN
0140-7791
eISSN
1365-3040
DOI
10.1111/j.1365-3040.2008.01848.x
pmid
18643956
Publisher site
See Article on Publisher Site

Abstract

ABSTRACT No single hypothesis or theory has been widely accepted for explaining the functional mechanism of global alpine/arctic treeline formation. The present study tested whether the alpine treeline is determined by (1) the needle nitrogen content associated with photosynthesis (carbon gain); (2) a sufficient source–sink ratio of carbon; or (3) a sufficient C–N ratio. Nitrogen does not limit the growth and development of trees studied at the Himalayan treelines. Levels of non‐structural carbohydrates (NSC) in trees were species‐specific and site‐dependent; therefore, the treeline cases studied did not show consistent evidence of source/carbon limitation or sink/growth limitation in treeline trees. However, results of the combined three treelines showed that the treeline trees may suffer from a winter carbon shortage. The source capacity and the sink capacity of a tree influence its tissue NSC concentrations and the carbon balance; therefore, we suggest that the persistence and development of treeline trees in a harsh alpine environment may require a minimum level of the total NSC concentration, a sufficiently high sugar:starch ratio, and a balanced carbon source–sink relationship.

Journal

Plant Cell & EnvironmentWiley

Published: Oct 1, 2008

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