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Climate, nutrient availability, and the distribution of pre-contact dryland agriculture in Hawai'i.
Vitousek, Peter*,1, Chadwick, Oliver2, Ladofoged, Thegn3, Graves, Michael 4, Hotchkiss, Sara5, Kirch, Patrick6, Matson, Pamela1, Tuljapurkar, Shripad1, 1 Stanford University, Stanford, CA, USA2 University of California - Santa Barbara, Santa Barbara, CA, USA3 University of Washington, Seattle, WA, USA4 University of Hawaii - Manoa, Honolulu, HI, USA5 University of Wisconsin - Madison, Madison, WI, USA6 University of California - Berkeley, Berkeley, CA, USA
ABSTRACT- Hawaiians developed and maintained intensive dryland agricultural systems for hundreds of years prior to European contact. One such system occupied 55 kilometers squared on the leeward flank of Kohala Volcano, the oldest volcano on the island of Hawai'i. This leeward slope supports one of the steepest rainfall gradients on Earth, from <200 to >3000 mm/yr in less than 15 km, and remains of the Kohala field system fill the area receiving between 750 and 1500 mm/yr. As part of an effort to understand relationships among soil fertility, agricultural intensification, human effects on ecosystems, and the development of social and cultural complexity in Hawaiian society, we determined soil characteristics along several transects across the field system. The soils of areas above (wetter than) the field system are infertile, with low base saturation and available P averaging 3.9 ug/g. Within the field system, soil P concentrations are much greater, averaging 124 ug/g, while soils in dry sites below the field system have high base saturation and intermediate available P (26 ug/g). Intensive agriculture here appears to have been poised between conditions that are too wet (and so infertile) and too dry (and so water-limited).
Key words: nutrient cycling, soil fertility, agricultural intensification, hawai'i