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Seasonal Dynamics and the Islands of Fertility in Arid Landscapes: An Evaluation of Extraction Techniques

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Microarthropods play important roles in the decomposition process of the detrital food web, where they break down organic matter and return nutrients to the soil. However, only a small percentage of the belowground microarthropod population has been studied or even

Microarthropods play important roles in the decomposition process of the detrital food web, where they break down organic matter and return nutrients to the soil. However, only a small percentage of the belowground microarthropod population has been studied or even discovered, leading to a decrease in the knowledge of all of the processes carried out by these organisms and their importance to the soil. This is because microarthropod extraction methods are not 100% effective at collecting specimens. This study aimed to find an ideal quantitative procedure to better record the number of microarthropods existing in the soil and to determine if a seasonal variation exists that effects the success of extraction. Two extraction methods, including dynamic extraction and heptane flotation extraction, were compared across two seasons, a dry season (June) and a wet season (September). Average biomasses and average richness were calculated for four different functional groups, including Prostigmata, Mesostigmata, Cryptostigmata, and Collembola, across the two seasons, and statistical analysis was performed to determine if any differences that existed were statistically significant. Results indicate that the dynamic extraction method was significantly more effective for the collection of microarthropods during the wet season, and the heptane extraction method was significantly more effective during the dry season. In addition, the heptane procedure recovered samples of higher average richness than the dynamic method during both seasons. The heptane procedure works best for extraction during the dry season because it is able to collect organisms that entered into an ametabolic anhydrobiotic state to escape desiccation. These organisms form a protective lipid layer around their exoskeletons to retain water, and the non-polar exoskeletons display a chemical affinity to the heptane fluid, allowing for collection out of the soil and into the heptane layer. Despite these results, no one method is entirely superior to the other, and the most efficacious procedure depends on the researcher's aim of study.

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2014-12

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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 central Arizona, Pueblo la Plata within the Agua Fria National

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