Abstract

As global temperatures rise, cultivation of C3 and C4 crops in arid and semi-arid regions will face major challenges in producing biomass for billions of people. Conventional agricultural techniques that require copious irrigation will need to be complemented with dryland-farming techniques and drought-tolerant crops, such as those from the Agave genus, which use CAM photosynthesis. In the past and present, humans from arid and semi-arid regions of America have maintained a symbiotic relationship using and cultivating Agave (Agavoideae, Asparagaceae). In pre-Columbian times, Native Americans from arid regions relied on Agave cultivation as a subsistence crop to produce food, medicine, and fiber. The Hohokam in the Sonoran Desert cultivated Agave plants using rock mulching, also known as rock piles. This technique enabled the Hohokam to extensively cultivate Agave despite the limited rainwater available in the harsh Sonoran Desert. Although there are several decades of archaeological research for documenting the history of rock piles and Agave in the region beginning in the late 1970s, few studies have addressed the modern application of rock piles to cultivate Agave. Our research employed a multidisciplinary approach to bridge the historic use of rock piles to cultivate Agave with the potential application of rock piles for modern cultivation. In addition to summarizing what is known about the archaeology of Hohokam rock piles, we compiled an extensive review of the literature available on the agroecology, physiology, and natural history of Agave. We described key aspects associated with the hydrology and physical properties of Hohokam rock piles that can bolster Agave CAM photosynthesis in dry regions. We found that the use of rock piles is a feasible means of cultivating Agave under hot and dry conditions in arid regions. In addition, we used an ecological niche modeling approach and field data from Hohokam rock-pile sites and current Agave fields to assess the potential environments where rock piles could be used to cultivate Agave plants in Arizona, USA and Sonora, Mexico. We also combined an experimental archaeology approach with experimental plant physiology where we surveyed Hohokam rock-pile fields at archaeological sites to collect information about the composition of rock piles. We then created a rock-pile field where we evaluated and observed the effects of rock piles on Agave CAM utilization, mainly nocturnal CO2 uptake of Agave. Our results indicated that rock piles provide direct insulation to root systems, which indirectly benefited Agave carbon uptake and reduced temperature and drought stress. Although more agronomic research about rock pile use is needed, our research suggests that rock piles can be applied to cultivate Agave because of the physiological benefits provided such as increasing nocturnal total CO2 uptake. In addition, the suitability of rock piles in the U.S borderlands indicates that rock piles can be applied beyond the regions where they were used by the Hohokam in pre-historic times.

Degree

PhD

College and Department

Life Sciences; Plant and Wildlife Sciences

Rights

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