The Impact of Non-Passive Monitor Behavior on Developing Tree Ring Elemental Concentration Based Chronologies of Environmental Change
Abstract
Most temperate tree species contain visibly distinct annual growth rings. These individual rings contain distinct isotopic and elemental compositions from pith to bark. As these individual rings can be dated to specific growth years, it is tempting to interpret these variations as directly reflecting temporal changes in the geochemical environment. However, tree physiology, in addition to changes in elemental bioavailability can effect the elemental composition of the growth ring. The viability of variations in tree ring elemental concentration as a proxy for changing environmental conditions is dependent on whether they are passive monitors of element bioavailability or their active incorporation can be characterized and properly considered during interpretation. We measured elemental concentrations in tree rings from red and white oak trees at sites across Southern Ontario, Canada, to determine whether they passively record changes in geochemical cycling in the presence of environmental stress. Periods of stress were defined as sustained intervals with elevated δ13C values in tree rings relative to contemporaneous atmospheric carbon dioxide. In some trees, nutrient concentrations (Ca, Mg, Mn) were highly variable during periods of stress while chemically similar non-nutrients (Ba, Sr) and the anthropogenic pollutant Pb were not. The concentration of Ca and Sr in the tree rings were related to bedrock type and leachable concentration in the soil, while Mn, Ba and Pb were not, but were inversely related to soil pH. The erratic behavior of nutrients during periods of stress suggests that although they are not always passive monitors of bioavailability, their variation may have environmental significance. The application of analytical techniques such as laser ablation ICP-MS to micro- sample across individual rings and around the bole will likely lead to the application of dendrochemistry to study environmental questions of a spatial or sub-annual nature. Although seldom an entirely straightforward passive monitor of changes in bioavailability, variations in tree ring chemistry seem to record geochemical conditions with some temporal resolution.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMPP52A..05B
- Keywords:
-
- 3344 Paleoclimatology (0473;
- 4900);
- 4870 Stable isotopes (0454;
- 1041);
- 4900 PALEOCEANOGRAPHY (0473;
- 3344)