Under the direction of Dr. Katherine Spielmann, Melissa Kruse-Peeples will conduct investigations of ancient agricultural systems in the Perry Mesa region of Central Arizona. Perry Mesa, located 90 miles north of Phoenix, was occupied by prehistoric farmers living in large aggregated villages from approximately A.D. 1275-1450. Agricultural land use focused on runoff, a strategy in which fields are placed in locations that receive additional inputs of water from runoff flowing down gentle hillslopes during intense storms. The construction of small terraces perpendicular to the slope maximizes water retention and renews fertility by capturing organic debris and sediments washing down slope. The region abounds with the remains of these prehistoric farming systems. It is not clear whether the extensiveness of agricultural fields on Perry Mesa reflects high agricultural potential or the fact that farming was difficult, requiring significant investment in the landscape to improve its productivity. In addition, the density of prehistoric fields could indicate that these farmers needed to practice a land-extensive cultivation strategy that involved frequent rotation of fields to maintain soil fertility. Using the prehistoric occupation of Perry Mesa as a case study, Kruse-Peeples will take an interdisciplinary approach, drawing on archaeology and ecology to understand the long-term productivity and sustainability of agriculture in arid regions.
This project integrates archaeological investigations of the prehistoric settlements and farming systems with ecological methods of soil nutrient analysis and soil moisture measurements. Analyses include (1) investigation of how effective terrace systems are at capturing and retaining surface runoff, (2) determination of the soil fertility and renewal through nutrient analysis of agricultural soils and runoff , (3) a simulation model to determine the dynamics of soil fertility over time as crops extract nutrients and management of surface runoff renews fertility, (4) a GIS analysis to document the distribution of landscape modifications on Perry Mesa, and (5) reconstruction of the prehistoric population based on the size of archaeological sites to determine the amount of land required to support these communities. Together, these analyses will provide a characterization of the agricultural potential of the Perry Mesa landscape that assesses how technologies such as terracing and practices such as management of runoff relate to agricultural productivity. Kruse-Peeples will use this information to determine if the agricultural landuse in the Perry Mesa region was sustainable, and if potential landscape depletion was a factor in why the area was eventually abandoned after less than 200 years of occupation.
This study will contribute to graduate student training and continue on-going interdisciplinary collaborations between archaeologists and ecologists focused on understanding the long-term consequences of prehistoric landuse in the Southwest, and sustainable solutions for contemporary arid land agriculture. An undergraduate student will participate in the research as a field assistant and will gain interdisciplinary training in archaeology and soil ecology. Additionally, a public symposium about the research will be organized to disseminate the results to federal land managers of the Perry Mesa area (Bureau of Land Management and the US Forest Service) as well as Native American communities affiliated with the region.
Agricultural potential plays an important role in explanations of regional settlement and abandonment across the prehistoric North American Southwest. This study focused on the Perry Mesa area in central Arizona (ca. A.D. 1275-1450), a region where extensive agricultural terracing of the landscape has been documented. However, the long-term sustainability of agriculture and the potential improvements terracing provided to productivity has not previously been assessed. Specifically, this research addressed how the construction of agricultural terraces altered key parameters (water and nutrients) necessary for successful agriculture in an arid region, and how these parameters, particularly soil nutrients, changed with prolonged use of fields. The project integrated field data collection with simulation modeling. All project fieldwork was completed with undergraduate students from Arizona State University in collaboration with the Bureau of Land Management, the land managers for the region. Students were training in archaeological field mapping, soil sampling and nutrient analysis, and report writing. The project addressed two key questions: 1) how long can cultivated fields, particularly those that are terraced, be farmed before soil fertility is depleted; and 2) was there sufficient arable land available to maintain soil fertility, given the known climatic trends and land requirements based on estimated population density. Results indicate that terracing was essential to capture sediments displaced by intense thunderstorms. These sediments, when retained, would improve fertility prolonging field use life. These benefits would have been most pronounced during wet climatic regimes and necessary to sustain farming during dry periods when soil fertility declined much quicker. Ultimately, however, the drying climatic trends of the mid-1400s made cultivation difficult due to decline precipitation and fast depleting soil fertility factoring into regional abandonment and depopulation of Perry Mesa. This project integrated archaeological data about human manipulation of the landscape and ecological data about the effects of this manipulation on water and nutrients available to crops to understand the prehistoric agroecostyem of Perry Mesa. The results of this research are applicable to other archaeological and contemporary contexts providing a long-term perspective on agricultural productivity of subsistence farming in arid regions, a topic which is increasingly important due to climate change. Substantial numbers of people are concentrated in arid regions that contribute to local and global food supplies. This research provides a methodological approach and framework for assessing the sustainability of arid land agriculture in general.
