现代环境研究室知识库

The stable isotope composition of tree rings is known to contain valuable information of past climatic and environmental changes, which may be used as a complement to tree ring width and maximum latewood density in climate reconstructions. In this study we examine the character and strength of the climate signal captured in the delta(18)O and delta(13)C values of Scots pine (Pinus sylvestris L.) trees growing at the tree-line in the central Scandinavian Mountains. Between 4 and 14 trees were pooled to produce annual records of carbon and oxygen isotope ratios from tree ring cellulose, spanning the period AD 1736-2006. Weather conditions of the current growing season most strongly influenced the carbon and oxygen isotope ratios in a given tree ring. Both records showed positive correlations with temperature, sunshine and air pressure, and negative associations with precipitation. The overall climate signal in delta(13)C appeared to be slightly stronger than that of delta(18)O. Spatial correlation analysis with gridded instrumental data demonstrated that the carbon series captured the summer temperature signal in a broad region of mid-west Sweden and the eastern part of Norway, greatly exceeding the spatial coverage of the signal derived from pine ring widths growing in the central Scandinavian mountains. A weak relationship between delta(13)C and precipitation and a much stronger temperature and sunshine dependence may imply that photosynthetic rate rather than stomatal conductance is more important in controlling the inter-annual tree ring delta(13)C variability in the area.