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

• Published in: Plant, Cell & Environment
• Main Authors: LI, MAI‐HE, XIAO, WEN‐FA, SHI, PEILI, WANG, SAN‐GEN, ZHONG, YONG‐DE, LIU, XING‐LIANG, WANG, XIAO‐DAN, CAI, XIAO‐HU, SHI, ZUO‐MIN
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2008
• Subjects: Arctic; The Needle
• Online Access: http://dx.doi.org/10.1111/j.1365-3040.2008.01848.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-3040.2008.01848.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3040.2008.01848.x

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.