Temperature Number One Driver of Tree's Height
Temperature, and particularly temperature stability, is the biggest driver of a tree's height, according to a new report published in the journal New Phytologist.
Led by Markku Larjavaara, a researcher from the University of Helsinki, the study found that the tallest specimens of the world's nine tallest tree species were discovered in climates with uniquely limited seasonal temperature variation.
These regions of relative climatic calm accounted for just 2.1 percent of global land area - not including Antarctica - and differed significantly from one another in terms of other possible factors. For example, their distances from the equator ranged from 2,400-3,400 miles and their altitude from 164-5,740 feet. Furthermore, the distance between the most distant localities ranged from 870-1,680 miles in western North America and Australia, respectively.
"Forest biomass is widely studied because the carbon stored in trees could add to atmospheric carbon dioxide," Larjavaara, who teaches in the Department of Forest Sciences, wrote in the study. "However, biologically, tree height is more meaningful than biomass because it directly relates to competitive fitness." Taller trees receive more sunlight on their leaves, meanwhile blocking it from those around it. Height also means the tree's pollen and fruits that are dispersed by the wind can travel farther.
Knowing what drives tree growth is critical, Larjavaara notes, if researchers are to make accurate predictions of climate change given trees' important role in absorbing carbon dioxide emitted into the atmosphere. The bigger a tree is, the more CO2 it's able to absorb.
"It is amazing how little we know about the causes of global tree size variation even though not knowing current variation makes predicting climate change caused changes difficult or impossible," Larjavaara said. "If trees will get bigger in the future they will store more carbon than they do now and would therefore mitigate climate change."