Stem and branch respiration of beech: from tree measurements to estimations at the stand level
Résumé
- Stem and branch respiration of 30-yr-old Fagus sylvatica trees was measured in a temperate forest for 1 yr to estimate the annual flux at the stand level. - The seasonal response of respiration to air temperature was determined using infra-red gas analysis (IRGA) systems. Annual respiration was derived from half-hourly temperature recording and allometric relations established for the same forest. - The basal respiration rate at 15 C (R15) increased greatly during the growing season. On a volume basis, monthly means of R were higher for branches than for stems. For stems, Q was relatively constant throughout the year, with an annual average of 1.7. Estimated annual respiration was approx. 325 g C m ground with 50% of this amount attributed to growth respiration. - Stem and branch respiration played a major role in the annual carbon balance of the beech stand. It represented approx. one third of the ecosystem-level carbon loss from respiration. The magnitude of crown respiration makes it obvious that information on branch respiration characteristics is required for reliable estimations at the stand level.