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Polynesians settled and farmed the leeward, relatively arid slopes of Haleakala Volcano beginning about ad 1400. Archaeological investigations at two sites revealed dense concentrations of conical impressions in a subsurface 20cm cinder layer that was previously undisturbed, interpreted as resulting from cultivation practices involving digging sticks. Ethnographic accounts of Hawaiian sweet potato and dryland taro cultivation techniques provide details on the use of such digging sticks. By puncturing this cinder layer, farmers created a loamy mixture of ash and cinder suited to root crop development. Archaeobotanical analyses suggest an intensive, short-fallow regime: macroscopic wood charcoal was absent (therefore no fallow sufficient for secondary re-growth of dryland forest) and evidence of disturbance-tolerant, weedy species is abundant. Geochemical analyses relying on stratigraphic relationships show that cultivation depleted nutrient levels in the digging-stick impressions, through harvest and leaching losses. Our findings provide evidence for repeated and intensive use of a landscape under a system of dryland cultivation. [ABSTRACT FROM AUTHOR]

We used measurements from airborne imaging spectroscopy and LiDAR to quantify the biophysical structure and composition of vegetation on a dryland substrate age gradient in Hawaii. Both vertical stature and species composition changed during primary succession, and reveal a progressive increase in vertical stature on younger substrates followed by a collapse on Pleistocene-aged flows. Tall-stature Metrosideros polymorpha woodlands dominated on the youngest substrates (hundreds of years), and were replaced by the tall-stature endemic tree species Myoporum sandwicense and Sophora chrysophylla on intermediate-aged flows (thousands of years). The oldest substrates (tens of thousands of years) were dominated by the short-stature native shrub Dodonaea viscosa and endemic grass Eragrostis atropioides. We excavated 18 macroscopic charcoal fragments from Pleistocene-aged substrates. Mean radiocarbon age was 2,002 years and ranged from < 200 to 7,730. Genus identities from four fragments indicate that Osteomeles spp. or M. polymorpha once occupied the Pleistocene-aged substrates, but neither of these species is found there today. These findings indicate the existence of fires before humans are known to have occupied the Hawaiian archipelago, and demonstrate that a collapse in vertical stature is prevalent on the oldest substrates. This work contributes to our understanding of prehistoric fires in shaping the trajectory of primary succession in Hawaiian drylands.