photo: F Delventhal
Ecologists working at the Smithsonian Environmental Research Center studying the rate of growth over hardwood forests in Maryland over the past 20 years have determined that trees there are growing faster than they have in the past 225 years:Growing 2-4 Times Faster Than Baseline Growth
The research shows that on average the forests they studied are putting on an additional 2 tons of biomass per acre annually. The Smithsonian's blog says that's the equivalent of one more tree with a 2-foot diameter growing to full height every year.
Assessing how a forest is changing is no easy task. Forest ecologists know that the trees they study will most likely outlive them. One way they compensate for this is by creating a "chronosequence"--a series of forests plots of the same type that are at different developmental stages. At SERC, Parker meticulously tracks the growth of trees in stands that range from 5 to 225 years old. This allowed Parker and [research assistant Sean] McMahon to verify that there was accelerated growth in forest stands young and old. More than 90% of the stands grew two to four times faster than predicted from the baseline chronosequence.
Combination of Climate Factors Accelerating Tree Growth
Report author Geoffrey Parker says that the main driver is climate change--measurements show that trees growing faster is a recent phenomenon.
Over the past two decades CO2 levels have risen by 12%, mean temperatures have increased a third of a degree, and there's been a week increase in the growing season.
Parker says a combination of these is likely at play, and that the faster growth rates will level off over time.
Results of their research will be published in the Proceedings of the National Academy of Sciences
[ed. note: the Smithsonian says that link to the original research should be valid shortly, but was not at the time of this writing]
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