Since the time of the earliest humans, people have attempted to understand the natural environment. We have observed our surroundings and searched for explanations for natural phenomena. Yet despite our persistence over thousands of years, many basic questions remain to be answered. Although we understand core processes such as photosynthesis, we do not have a full understanding of issues such as how plants maximize their photosynthetic capacity.
Specific leaf area, or SLA, plays a prominent role in ecological theories that attempt to provide explanations for plant and ecosystem function. SLA, a measurement of the total leaf area to dry mass, has been found to correlate with the potential for light-resource use, the relative growth rate of a plant, and differences in essential nutrient demand and habitat preference.
Scientists also have observed that the SLA of individual leaves varies within a single plant, and this measurement often correlates with leaf maturation and position within the canopy. More recently, scientists have discovered that, as a tree increases in size, its total canopy SLA decreasesthat is to say, its total leaf surface area fails to keep pace with increases in total leaf mass.
What causes this decrease in SLA as tree size increases has remained a mystery, but recent research by Cornell University scientists Karl Niklas and Edward Cobb published in the January issue of the American Journal of Botany (http://www.amjbot.org/cgi/content/full/97/1/27) provides an explanation for this decrease in SLA with an increase in tree size.
"The traditional explanation for the size-dependent decrease in SLA was never very satisfying," Niklas said. "We wanted to look at this phenomena in greater details with more care, and we found a totally different answer to a classic ecological question."
The commonly accepted hypothesis has be
|Contact: Richard Hund|
American Journal of Botany