Vitousek BioGeoChemistry Lab

The Vitousek Group and colleagues carry out research related to nutrient cycling, most notably nitrogen and phosphorus, throughout the range of environments and ecosystems. The Hawaiian Islands are the focus of the majority of studies. Our group has looked at nutrient dynamics in the soil profile, litter, native forest ecosystems, forest and grassland systems affected by invasive species and agricultural systems. Studies have documented how an invasive grass has changed the fire frequency and suppressed the ability of the native forest to return. How an invasive nitrogen fixing tree changes the nutrient dynamics in the soil and facilitates further encroachment by other non-native plants.

Hawaii is a unique place for such studies being so isolated. We have set up a chain of study sites spanning the major islands we call the Long Substrate Age Gradient, or LSAG. This substrate age gradient makes use of the increasing age of Hawaiian volcanoes with increasing distance from the hot spot, from southeast to northwest across the islands. Originally, much of the gradient was developed by Ralph Riley for a study of the regulation of nitrogen trace gas emissions; it was later refined by Tim Crews, Darrell Herbert, Kanehiro Kitayama, and Peter Vitousek to consist of six sites that range in age from ~300 to ~4.1 million years. These include the 0.3 ky (ky = 1000 years) Thurston site on Kilauea Volcano, the 2.1 ky Ola'a site on Mauna Loa, the 20 ky Laupahoehoe site on Mauna Kea, the 150 ky Kohala site on Kohala Volcano, the 1400 ky Kolekole site on East Molokai volcano, and the 4100 ky Koke'e site on Kaua'i.

Additionally we are looking at how the early Hawaiians practiced agriculture on both dry and wet irrigated field systems. Our goal is to increase scientific understanding of long-term co-evolutionary interactions between people and their environments, and to advance the use of past dynamics as explanatory models for contemporary global environmental change. In the course of our work, we have made a systematic effort to reach out to the Hawaiian public, and particularly to Native Hawaiians, with our findings. The extent and intensity of precontact dryland agriculture are not widely appreciated in Hawai‘i – and where they are understood, the contemporaneous scarcity of agriculture as intensive in the continental tropics is little recognized. Our outreach has been direct (through numerous public talks), through the educational system (through talks to Native Hawaiian programs at the University of Hawai’i (Manoa and Hilo) and at Kamehameha Schools (a multi-campus K-12 school for Native Hawaiians), and through the media.