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Sustaining irrigation agriculture for the long-term: lessons on maintaining soil quality from ancient agricultural fields in the Phoenix Basin and on the north coast of Peru

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Irrigation agriculture has been heralded as the solution to feeding the world's growing population. To this end, irrigation agriculture is both extensifying and intensifying in arid regions across the world

Irrigation agriculture has been heralded as the solution to feeding the world's growing population. To this end, irrigation agriculture is both extensifying and intensifying in arid regions across the world in an effort to create highly productive agricultural systems. Over one third of modern irrigated fields, however, show signs of serious soil degradation, including salinization and waterlogging, which threaten the productivity of these fields and the world's food supply. Surprisingly, little ecological data on agricultural soils have been collected to understand and address these problems. How, then, can expanding and intensifying modern irrigation systems remain agriculturally productive for the long-term? Archaeological case studies can provide critical insight into how irrigated agricultural systems may be sustainable for hundreds, if not thousands, of years. Irrigation systems in Mesopotamia, for example, have been cited consistently as a cautionary tale of the relationship between mismanaged irrigation systems and the collapse of civilizations, but little data expressly link how and why irrigation failed in the past. This dissertation presents much needed ecological data from two different regions of the world - the Phoenix Basin in southern Arizona and the Pampa de Chaparrí on the north coast of Peru - to explore how agricultural soils were affected by long-term irrigation in a variety of social and economic contexts, including the longevity and intensification of irrigation agriculture. Data from soils in prehispanic and historic agricultural fields indicate that despite long-lived and intensive irrigation farming, farmers in both regions created strategies to sustain large populations with irrigation agriculture for hundreds of years. In the Phoenix Basin, Hohokam and O'odham farmers relied on sedimentation from irrigation water to add necessary fine sediments and nutrients to otherwise poor desert soils. Similarly, on the Pampa, farmers relied on sedimentation in localized contexts, but also constructed fields with ridges and furrows to draw detrimental salts away from planting surfaces in the furrows on onto the ridges. These case studies are then compared to failing modern and ancient irrigated systems across the world to understand how the centralization of management may affect the long-term sustainability of irrigation agriculture.

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  • 2013

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Innovation in context: the process of stylistic change among Hohokam potters in the Phoenix Basin, A.D. 800-1300

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The causes and consequences of stylistic change have been a concern of archaeologists over the past several decades. The actual process of stylistic innovation, however, has received less attention. This

The causes and consequences of stylistic change have been a concern of archaeologists over the past several decades. The actual process of stylistic innovation, however, has received less attention. This project explores the relationship between the process of stylistic innovation on decorated pottery and the social context in which it occurred in the Hohokam area of south-central Arizona between A.D. 800 and 1300. This interval was punctuated by three episodes of reorganization, each of which was characterized to varying degrees by significant shifts in ideology, economics, and politics. Each reorganization episode was also accompanied by a rapid profusion of stylistic innovation on buff ware pottery. The goal of this study was to build a framework to understand the variation in the process of innovation as a response to different incentives and opportunities perceived in the changing social environment. By bringing stylistic analyses and provenance data together for the first time in Hohokam red-on-buff studies, I investigated how the process of innovation was variously influenced by social reorganizations at three different periods of time: the 9th, 11th, and 12th centuries A.D. Four variables were used to evaluate the process of innovation at each temporal period: 1) The origin of a stylistic invention, 2) the rate of its adoption, 3) the pattern of its adoption, and 4) the uniformity of its adoption among all buff ware potting communities. To accomplish the task, stylistic innovations and provenance were recorded on over 3,700 red-on-buff sherds were analyzed from 20 sites in the Phoenix Basin. The innovation process was found to vary with each reorganization episode, but often in different ways than expected. The results revealed the complexity and unpredictability of the process of stylistic innovation among the Hohokam. They also challenged some assumptions archaeologists have made regarding the scale and extent of the changes associated with some of the reorganization episodes. The variables utilized to measure the innovation process were found to be effective at providing a composite picture of that process, and thus warrant broader application to other archaeological contexts.

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  • 2013

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The ancient agroecology of Perry Mesa: integrating runoff, nutrients, and climate

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Understanding agricultural land use requires the integration of natural factors, such as climate and nutrients, as well as human factors, such as agricultural intensification. Employing an agroecological framework, I use

Understanding agricultural land use requires the integration of natural factors, such as climate and nutrients, as well as human factors, such as agricultural intensification. Employing an agroecological framework, I use the Perry Mesa landscape, located in central Arizona, as a case study to explore the intersection of these factors to investigate prehistoric agriculture from A.D. 1275-1450. Ancient Perry Mesa farmers used a runoff agricultural strategy and constructed extensive alignments, or terraces, on gentle hillslopes to slow and capture nutrient rich surface runoff generated from intense rainfall. I investigate how the construction of agricultural terraces altered key parameters (water and nutrients) necessary for successful agriculture in this arid region. Building upon past work focused on agricultural terraces in general, I gathered empirical data pertaining to nutrient renewal and water retention from one ancient runoff field. I developed a long-term model of maize growth and soil nutrient dynamics parameterized using nutrient analyses of runoff collected from the sample prehistoric field. This model resulted in an estimate of ideal field use and fallow periods for maintaining long-term soil fertility under different climatic regimes. The results of the model were integrated with estimates of prehistoric population distribution and geographical characterizations of the arable lands to evaluate the places and periods when sufficient arable land was available for the type of cropping and fallowing systems suggested by the model (given the known climatic trends and land use requirements). Results indicate that not only do dry climatic periods put stress on crops due to reduced precipitation but that a reduction in expected runoff events results in a reduction in the amount of nutrient renewal due to fewer runoff events. This reduction lengthens estimated fallow cycles, and probably would have increased the amount of land necessary to maintain sustainable agricultural production. While the overall Perry Mesa area was not limited in terms of arable land, this analysis demonstrates the likely presence of arable land pressures in the immediate vicinity of some communities. Anthropological understandings of agricultural land use combined with ecological tools for investigating nutrient dynamics provides a comprehensive understanding of ancient land use in arid regions.

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  • 2013

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Identity and social transformation in the prehispanic Cibola world: A.D. 1150-1325

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This dissertation explores the interrelationships between periods of rapid social change and regional-scale social identities. Using archaeological data from the Cibola region of the U.S. Southwest, I examine changes in

This dissertation explores the interrelationships between periods of rapid social change and regional-scale social identities. Using archaeological data from the Cibola region of the U.S. Southwest, I examine changes in the nature and scale of social identification across a period of demographic and social upheaval (A.D. 1150-1325) marked by a shift from dispersed hamlets, to clustered villages, and eventually, to a small number of large nucleated towns. This transformation in settlement organization entailed a fundamental reconfiguration of the relationships among households and communities across an area of over 45,000 km2. This study draws on contemporary social theory focused on political mobilization and social movements to investigate how changes in the process of social identification can influence the potential for such widespread and rapid transformations. This framework suggests that social identification can be divided into two primary modes; relational identification based on networks of interaction among individuals, and categorical identification based on active expressions of affiliation with social roles or groups to which one can belong. Importantly, trajectories of social transformations are closely tied to the interrelationships between these two modes of identification. This study has three components: Social transformation, indicated by rapid demographic and settlement transitions, is documented through settlement studies drawing on a massive, regional database including over 1,500 sites. Relational identities, indicated by networks of interaction, are documented through ceramic compositional analyses of over 2,100 potsherds, technological characterizations of over 2,000 utilitarian ceramic vessels, and the distributions of different types of domestic architectural features across the region. Categorical identities are documented through stylistic comparisons of a large sample of polychrome ceramic vessels and characterizations of public architectural spaces. Contrary to assumptions underlying traditional approaches to social identity in archaeology, this study demonstrates that relational and categorical identities are not necessarily coterminous. Importantly, however, the strongest patterns of relational connections prior to the period of social transformation in the Cibola region largely predict the scale and structure of changes associated with that transformation. This suggests that the social transformation in the Cibola region, despite occurring in a non-state setting, was governed by similar dynamics to well-documented contemporary examples.

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  • 2011

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A multi-factor analysis of the emergence of a specialist-based economy among the Phoenix Basin Hohokam

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This project examines the social and economic factors that contributed to the development of a specialist-based economy among the Phoenix Basin Hohokam. In the Hohokam case, widespread dependence on the

This project examines the social and economic factors that contributed to the development of a specialist-based economy among the Phoenix Basin Hohokam. In the Hohokam case, widespread dependence on the products of a few concentrated pottery producers developed in the absence of political centralization or hierarchical social arrangements. The factors that promoted intensified pottery production, therefore, are the keys to addressing how economic systems can expand in small-scale and middle-range societies. This dissertation constructs a multi-factor model that explores changes to the organization of decorated pottery production during a substantial portion of the pre-Classic period (AD 700 - AD 1020). The analysis is designed to examine simultaneously several variables that may have encouraged demand for ceramic vessels made by specialists. This study evaluates the role of four factors in the development of supply and demand for specialist produced red-on-buff pottery in Hohokam settlements. The factors include 1) agricultural intensification in the form of irrigation agriculture, 2) increases in population density, 3) ritual or social obligations that require the production of particular craft items, and 4) reduced transport costs. Supply and demand for specialist-produced pottery is estimated through a sourcing analysis of non-local pottery at 13 Phoenix Basin settlements. Through a series of statistical analyses, the study measures changes in the influence of each factor on demand for specialist-produced pottery through four temporal phases of the Hohokam pre-Classic period. The analysis results indicate that specialized red-on-buff production was initially spurred by demand for light-colored, shiny, decorated pottery, but then by comparative advantages to specialized production in particular areas of the Phoenix Basin. Specialists concentrated on the Snaketown canal system were able to generate light-colored, mica-dense wares that Phoenix Basin consumers desired while lowering transport costs in the distribution of red-on-buff pottery. The circulation of decorated wares was accompanied by the production of plainware pottery in other areas of the Phoenix Basin. Economic growth in the region was based on complementary and coordinated economic activities between the Salt and the Gila River valleys.

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  • 2013

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Craft production and socio-economic marginality: living on the periphery of urban Teotihuacan

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This dissertation investigates socio-economic strategies adopted by a small craftworking community situated on the edge of one of the earliest, largest and most complex cities in Mesoamerica. The focus of

This dissertation investigates socio-economic strategies adopted by a small craftworking community situated on the edge of one of the earliest, largest and most complex cities in Mesoamerica. The focus of investigation is San Jose 520, a hamlet located on the southeastern margin of Teotihuacan and occupied primarily during the Tlamimilolpa and Xolalpan phases (ca. A.D. 200-500). Its inhabitants were potters of low socio-economic status living in small, architecturally simple residential structures. The investigation complements much more numerous studies of higher-status groups residing in Teotihuacan's famous apartment compounds, much larger and architecturally more formal structures clustered primarily within built-up parts of the city. The founding residents of San Jose 520 might have initially been immigrants, arriving at Teotihuacan after most of the city was already filled in and occupied, and therefore settling in a spatially marginal area with limited potential for farming. Archaeological field and lab investigations demonstrate that they adopted ceramic production as a strategy of economic survival in a competitive urban system. They specialized in the manufacture of the outcurving bowl--a vessel widely used at Teotihuacan for food service and certain ritual activities. At smaller scales of production, these potters also made other types of serving and ritual vessels and figurines. Evidence relating to mortuary and domestic rituals indicates participation in a number of the rituals typical of other sectors of Teotihuacan society, but not all. The most general goal of this investigation is to improve understanding of how socially and spatially marginal peoples possessing low economic status developed and exploited viable economic niches in pre-industrial urban systems. The San Jose 520 potters appear dynamic in their economic adjustment--in part by enhancing their production system over time through the adoption of various specialized pot-making tools (some as yet undocumented for Teotihuacan), and to some extent by modifying their product line, they survived for many generations. Nevertheless, they never succeeded in significantly raising their economic status; at the time of their apparent disappearance sometime in the Xolalpan phase, these potters and their households continued to constitute a case study of urban poverty in a massive pre-industrial city.

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  • 2011

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Seasonality and ecosystem response in two prehistoric agricultural regions of central Arizona

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This thesis explores the independent effects of the manipulation of rocks into alignments, prehistoric farming, and season on soil properties in two areas with a history of prehistoric agriculture in

This thesis explores the independent effects of the manipulation of rocks into alignments, prehistoric farming, and season on soil properties in two areas with a history of prehistoric agriculture in central Arizona, Pueblo la Plata within the Agua Fria National Monument (AFNM), and an archaeological site north of the Phoenix basin along Cave Creek (CC). Soil properties, annual herbaceous biomass and the physical properties of alignments and surface soils were measured and compared across the landscape, specifically on: 1) agricultural rock alignments that were near the archaeological site 2) geologically formed rock alignments that were located 0.5-1 km away from settlements; and 3) areas both near and far from settlements where rock alignments were absent. At AFNM, relatively well-built rock alignments have altered soil properties and processes while less-intact alignments at CC have left few legacies.

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  • 2011