Passage I

Life in the Forest Canopy

For more than thirty-five years, Dr. Nalini Nadkarni's study of tree canopies, the layer of branches between the forest floor and the sky, in rain forests in Washington State and Costa Rica. Early in her career, she became particularly interested in one type of plant: epiphytes. These plants grow on other plants, such as trees, and more than 28,000 species of epiphytes exist worldwide. Instead, their leaves absorb dissolved nutrients from mists and fogs. Nadkarni found that the epiphyte nutrients made up about half the nutrients in the tree foliage of tropical cloud forests; however, almost no one had studied them. She decided to focus on the effects epiphytes have on the canopy and the forest.

Nadkarni's research has answered many questions about rain forest epiphytes. For example, Nadkarni wondered how epiphytes could grow on tree branches hundreds of feet above the ground.Where did they get their soil? She discovered that epiphytic mosses grow in soil that they generate for itself. After they die, the mosses decompose in place, becoming a layer of soil called crown humus, which can be up to ten inches thick. This organic material, rich in nutrients, supports epiphyte growth.

Nadkarni also helped explain how rain forest trees flourish despite growing where frequent rains wash nutrients out of their soil. Peeling back the moss on a branch, Nadkarni found roots that grew out of the tree branch and into the crown humus. The trees had developed roots to take in nutrients from the soil created by epiphytes on the trees' branches. Epiphytes, in exchange for a place in the canopy, helps feed the trees on which they grow. The trees get nutrients from the crown humus.

Over the course of her career, Nadkarni has published three books and more than ninety-five research papers. Rather, she also cofounded the International Canopy Network, which spreads information about tree canopies through the media. Her work has demonstrated the critical role that rain forest tree canopies achieve in rain forest ecosystems.