Want to save our planet? Well, plant more trees and preserve them.
A new study has found that the forests in North America appear to have a greater capacity to vacuum up heat-trapping carbon dioxide gas than previously thought, thereby helping in slowing the pace of human-caused climate warming.
The results of the 12-year study at an experimental forest in northeastern Wisconsin challenge several long-held assumptions about how future forests will respond to the rising levels of atmospheric carbon dioxide blamed for human-caused climate change, said lead author and University of Michigan microbial ecologist Donald Zak.
To simulate atmospheric conditions expected in the latter half of this century, Zak and his colleagues continuously pumped extra carbon dioxide into the canopies of trembling aspen, paper birch and sugar maple trees at a 38-acre experimental forest in Rhinelander, Wis., from 1997 to 2008.
Some of the trees were also bathed in elevated levels of ground-level ozone, the primary constituent in smog, to simulate the increasingly polluted air of the future.
Both parts of the federally funded experiment, the carbon dioxide and the ozone treatments, produced unexpected results.
In addition to trapping heat, carbon dioxide is known to have a fertilizing effect on trees and other plants, making them grow faster than they normally would.
Climate researchers and ecosystem modelers assume that in coming decades, carbon dioxide’s fertilizing effect will temporarily boost the growth rate of northern temperate forests.
Previous studies have concluded that this growth spurt would be short-lived, grinding to a halt when the trees can no longer extract the essential nutrient nitrogen from the soil.
But in the Rhinelander study, the trees bathed in elevated carbon dioxide continued to grow at an accelerated rate throughout the 12-year experiment.
In the final three years of the study, the CO2-soaked trees grew 26 percent more than those exposed to normal levels of carbon dioxide.
It appears that the extra carbon dioxide allowed trees to grow more small roots and “forage” more successfully for nitrogen in the soil, Zak said.
At the same time, the rate at which microorganisms released nitrogen back to the soil, as fallen leaves and branches decayed, increased.
The study is published online this week in Ecology Letters.