Seasonal patterns of carbon allocation to respiratory pools in 60-yr-old deciduous (Fagus sylvatica) and evergreen (Picea abies) trees assessed via whole-tree stable carbon isotope labeling

• Published in: The New phytologist 2011-07, Vol.191 (1), p.160-172
• Main Authors: Kuptz, Daniel, Fleischmann, Frank, Matyssek, Rainer, Grams, Thorsten E. E.
• Format: Article
• Language: English
• Subjects: Beech; Canopies; Carbon; carbon allocation; Carbon dioxide; Carbon Dioxide - metabolism; Carbon Isotopes; carbon sequestration; carbon sinks; Cell Respiration; Efflux; Fagus - metabolism; Fagus sylvatica; Fagus sylvatica (European beech); Forest canopy; growth (RG) and maintenance (RM) respiration; Isotope composition; isotope labeling; Isotopic labeling; Phloem; phloem sugars; Photosynthates; Photosynthesis; Picea - metabolism; Picea abies; Picea abies (Norway spruce); Pine trees; Plant roots; Respiration; roots; seasonal variation; Seasonal variations; seasonality; Seasons; Spring; Spring (season); stable carbon isotope labeling; stable isotopes; Stores; Summer; Translocation; Tree trunks; Trees; trunk and coarse‐root CO2 efflux
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2011.03676.x

• The CO₂ efflux of adult trees is supplied by recent photosynthates and carbon (C) stores. The extent to which these C pools contribute to growth and maintenance respiration (RG and RM, respectively) remains obscure. • Recent photosynthates of adult beech (Fagus sylvatica) and spruce (Picea abies) trees were labeled by exposing whole-tree canopies to ¹³C-depleted CO₂. Label was applied three times during the year (in spring, early summer and late summer) and changes in the stable C isotope composition (δ¹³C) of trunk and coarse-root CO₂ efflux were quantified. • Seasonal patterns in C translocation rate (CTR) and fractional contribution of label to CO₂ efflux (FLabel-Max) were found. CTR was fastest during early summer. In beech, FLabel-Max was lowest in spring and peaked in trunks during late summer (0.6 ± 0.1, mean ± SE), whereas no trend was observed in coarse roots. No seasonal dynamics in FLabel-Max were found in spruce. • During spring, the RG of beech trunks was largely supplied by C stores. Recent photosynthates supplied growth in early summer and refilled C stores in late summer. In spruce, CO₂ efflux was constantly supplied by a mixture of stored (c. 75%) and recent (c. 25%) C. The hypothesis that RG is exclusively supplied by recent photosynthates was rejected for both species.