Latewood Width, Maximum Density, and Stable Carbon Isotope Ratios of Pine as Climate Indicators in a Dry Subalpine Environment, French Alps

Abstract

Pine latewood width, density, and stable carbon isotope ratios were measured at two sites, separated in altitude by 400 m, close to the forest limit on a south-facing slope in the western French Alps. The signal to noise ratio in the δ13C series from each site is higher than that of either of the growth proxies. When the sites are combined, the high-frequency climate signal in the δ13C series is enhanced, whereas in both the ring width and density series it is weakened. Because regional climate dominates over local site conditions, δ13C ratios from long pine chronologies will provide a better indicator of past climate than either ring widths or densities. At dry Alpine sites, δ13C values are controlled mainly by stomatal conductance, which is linked to summer moisture stress and thus antecedent precipitation.