What limits the height of trees? Is it the fraction of their photosynthetic energy they devote to productive new leaves? Or is it their ability to hoist water hundreds of feet into the air, supplying the green, solar-powered sugar factories in those leaves?
Both factors, resource allocation and hydraulic limitation, might play a role and a scientific debate has arisen as to which factor (or what combination) actually sets maximum tree height, and how their relative importance varies in different parts of the world.
Thomas Givnish, a professor of botany at the University of Wisconsin-Madison, attempts to resolve this debate by studying how tree height, resource allocation and physiology vary with climate in Victoria, Australia. Most studies of tree height have focused on finding the tallest trees and explaining why they live where they do, Givnish says. “This study was the first to ask, ‘How does the maximum tree height vary with the environment, and why?’”
