Nitrogen and carbon source-sink relationships in trees at the Himalayan treelines compared with lower elevations.
Plant Cell Environ
; 31(10): 1377-87, 2008 Oct.
Article
em En
| MEDLINE
| ID: mdl-18643956
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 sugarstarch ratio, and a balanced carbon source-sink relationship.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Árvores
/
Carbono
/
Altitude
/
Nitrogênio
País/Região como assunto:
Asia
Idioma:
En
Ano de publicação:
2008
Tipo de documento:
Article