Drought Leaves a Lasting Impression on Trees
In many forest ecosystems, the availability of water is the most important factor affecting year-to-year variation in tree growth. Alternating periods of wet and dry years are recorded in tree ring patterns around the world.
Forest Service scientists used a global tree-ring analysis to find out if trees recover to full growth rates immediately following the end of dry periods, or if there is a period of recovery during which growth remains below potential. They found a growth-lag effect,, especially in forests that are normally on the dry end of the precipitation scale and in pines as a group. The result means that over the long run, periodic lags in growth recovery following drought will add up and the forest will actually be less productive than anticipated without accounting for the lag. Although the effect may be small for a particular event, the effects accumulate over time, much like changing interest rates can affect the long-term yield of a bank account. Understanding this phenomenon is important to anyone who is interested in projecting future biomass of a forest or the rate of carbon sequestration, because accounting for it in projection models will bring the models closer to making realistic projections.
The study’s key findings are: Trees do not recover to normal growth rates immediately following drought; growth rates may take up to four years to recover.
The growth-lag effect does not affect all trees and forests equally. Normally dry forests and trees in the pine family show a larger effect than other types.The growth lag effect in trees is analogous to the effect of fluctuating interest rates on a bank account balance. The effects are compounded because the loss of potential growth during and after one drought reduces the potential growth in later periods by way of reduced living biomass; that is, future growth (interest) rates act on a smaller amount of live biomass (account balance).
|Pervasive drought legacies in forest ecosystems and their implications for carbon cycle models||(publication)|
Forest Service Partners