How do rain, sea salts, dust, plants, climate and time affect the chemistry of soil? At what threshold, for example, does the role of rain dramatically change the soil chemistry? What is the nature of the relationships between soil development and ecosystem change?

These and similar questions relating to the behavior of rock-derived nutrients and the accumulation of toxic elements in relation to ecosystem age and climate will be explored at the Hawaii Ecosystems Project, thanks to a three-year, $500,000 grant from The Andrew W. Mellon Foundation. Louis A. Derry, assistant professor of geological sciences at Cornell University, will receive $150,000 of the half million dollar award and will work in collaboration with Oliver Chadwick, a geologist at the University of California-Santa Barbara, and Jon Chorover, an agronomist at Pennsylvania State University.

"The Hawaiian Islands are a model ecosystem for this kind of study because the number of variables are so limited there," says Derry. "Their geological history provides an unusually well characterized progression of substrate ages and limited variation in substrate composition. For example, the islands have only one type of rock and not very many species of plants."

The research team will use the grant to complete their work on characterizing the substrate and soil properties in Hawaii. Specifically, they plan to study changes in soil nutrient sources in relation to climate (such as leaching intensity and oxidation-reduction) and topographic position (such as windward, leeward and height above sea level). They also will examine how acid soils are generated and what the ecosystem implications are of an accumulation of toxic levels of aluminum and manganese.

Their work will help provide insight into how acidic soils develop and to what extent soil acidification is a reversible process. For example, if acid rain is decreased by emissions controls, will acidic soil recover naturally, and how long is it likely to take? They will also address the feedback between plant uptake of mineral nutrients and recycling these elements back into the soil: How important are plants in driving changes in soil chemistry with time?

"Although the ecological literature is filled with references to many different kinds of soils, we don't fully understand the relations among them. For example, in nature, do different kinds of soils grade into each other smoothly in space and time so that the boundaries between them are difficult to define, or are the transitions between various states of soils sharp, reflecting few if any transitional conditions," says Derry.

"This grant allows us think about transitions in a new way and to link our observations about nutrient sources and availability and toxic elements into a conceptual whole that will make a significant contribution to biogecochemical theory," Derry says.

Other related websites:

• Louis Derry: http://www.geo.cornell.edu/geology/faculty/Derry.html
• The Andrew W. Mellon Foundation: http://www.mellon.org/