Comparisons of δ13C of photosynthetic products and ecosystem respiratory CO2 and their responses to seasonal climate variability

摘要: This study investigated the relationship between δ13C of ecosystem components, soluble plant carbohydrates and isotopic signature respired CO2 (δ13CR) during seasonal changes in soil atmospheric moisture a beech (Fagus sylvatica L.) forest central Apennine mountains, Italy. Decrease increase air vapour pressure deficit summer correlated with substantial leaf phloem sap sugars. Increases were linearly related to increases sugar (r2=0.99, P≤0.001) (r2=0.981, P≤0.01), indicating that major proportion was derived from recent assimilates. The slopes best-fit lines differed significantly (P≤0.05), however, about 0.86 (SE=0.04) for sugars 1.63 (SE=0.16) Hence, transferred respiration forest, while sugars, relatively small δ13C, must have slower turnover rate or significant storage component. No variation observed bulk dry matter various components (including leaves, bark, wood, litter organics). apparent coupling associated large disequilibria. Values δ13CR consistently more depleted by 4‰ relative 2‰ compared Since no combination measured pools could produce signal over entire season, discrimination against 13C might be short-term respiration. However, these differences also explained contributions other not carbon (e.g., lipids) linked footprint area Keeling plots carbohydrate sampling. Linking inter-annual variations isotope composition respiratory should applicable cycle models help understanding biospheric sink strength.