Can 13C stable isotope record of Norway spruce tree rings display the effect of environmental conditions?

Abstract

The Bohemian Forest Mts. (Šumava) were exposed to heavy atmospheric pollution in the last century. A possible negative effect of atmospheric pollution on tree physiology has been studied using the isotopic composition, Δ13C, of tree rings. The wood is depleted of 13C relative to the air due to isotopic discrimination against 13C and preferred uptake of 12C during photosynthesis. The ratio 13C/12C (Δ13C) reflects the relative magnitudes of net assimilation and stomatal conductance that relate to demand and supply of CO2. Carbon-13 data are thus a useful index for assessing intrinsic water use efficiency (mark period of drought or root system damages) and also could indicate assimilation organ injure (needle damage caused due to acid rain etc.). A decrease in Δ13C implies a negative effect of environmental conditions on tree physiology. Presumably, changes in soil pH and aluminium content as an indirect effect of atmospheric pollution could have an impact on tree physiology. Our results showed that the isotopic signal varied around the average, but the Δ13C signal was decreasing from the 1950s to 1980s and then increasing again starting in the 1990s. This trend is in accordance with the monitored atmospheric pollution and soil solution pH changes.

Keywords

• δ
• 13c
• air pollution
• tree physiology
• bohemian forest mts.
• soil ph
• aluminium
• soil acidification