Dynamic variation in agricultural practices during the Classic period in the Tonto Basin, Arizona

Abstract

The Classic period farmers living in the Tonto Basin, Arizona faced a diverse and rapidly fluctuating physical and social environment. The archaeological evidence is presented for changing adaptive strategies implemented by the inhabitants.The resulting account of variation in prehistoric agricultural practices depicts the range of options available to farmers in the Tonto Basin during the Classic period,to farmers in the Tonto Basin during the Classic period,explores the choices they made, and examines the results and consequences of those choices. The core of the research is the niacrobotanical analysis of 617 flotation samples from 54 archaeological sites. At least 62 different plant taxa were identified, including I I cultigens and 51 gathered wild plants. Three very different crop systems were identified, the warm-season annuals, cool-season grasses, and agave, a succulent rosette perennial. Each of these has a distinct, yet complementary growth history. Two fundamental adaptive strategies were identified, upland dry farming and irrigated alluvial terrace agriculture. Plant production dominated the subsistence economy throughout the Classic period. During the time span covered by the study, alternating droughts and heavy floods struck the basin around A.D. 1275, 1320, 1380, and 1455. A review of botanical, environmental, and settlement data indicated that the farmers began to depend more heavily on irrigation agriculture as the population grew. Variation in agricultural practices was reduced as emphasis was placed on irrigation agriculture. The commitment to a single adaptive strategy destabilized the agricultural system. During the first periods of environmental disaster, the populations aggregated around integrative architecture. The last period, however, resulted in the collapse of the communities and permanent abandonment of farming villages in Tonto Basin.