Southern California doesn’t experience dramatic seasonal changes, but we still enjoy the benefits of fall foliage, from bright colors to extra garden mulch. If you’re inclined to complain about the extra raking, cheer up.
Through a long-term, large-scale experiment, two botanists measured the important role litterfall (leaf or plant litter) plays in providing nutrients to plant life.1 For five years, the researchers worked in a semi-evergreen tropical forest, adding or subtracting different amounts of plant litter to or from different subplots monthly. They tracked trunk growth, litterfall levels, and nutrient concentrations in leaves, litter, and soil.
Their data showed that plots with the greatest quantity of litterfall (up to the study’s maximum), received the greatest enrichment of inorganic nitrogen and nitrates—the keys to forest growth and health. Those plots most deprived of litterfall were also most deprived of these nutrients. Given that a forest’s vitality is directly proportional to the amount of nitrogen nutrients available, optimized litterfall means optimized biomass for the entire planet.
The study’s upper limit on the quantity of plant litter used reflects awareness that too much plant litter can be harmful, preventing seeds from reaching the soil and releasing chemical toxins that hinder bacterial nitrification of the soil.2 If controlled by natural forest fires, such as those caused by lightening, litterfall stays just below that harmful limit.
The fine-tuned abundance of leaf litter in Earth’s forests speaks of thoughtful, intentional design. It also adds one more piece of evidence for the anthropic principle, the observation that the universe and Earth were designed for human life.
Next time you rake the yard be sure to offer up thanks for the Creator’s loving design of trees and falling leaves for our benefit and pleasure.
- Emma J. Sayer and Edmund V. J. Tanner, “Experimental Investigation of the Importance of Litterfall in Lowland Semi-Evergreen Tropical Forest Nutrient Cycling,” Journal of Ecology 98 (September 2010): 1052–62.
- Peter D. Moore, “Fire Damage Soils Our Forests,” Nature 384 (November 28, 1996): 312–13.