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Abstract

As a result of climate change driving global resource scarcity, ecosystems are pressured to respond to recent regime shifts. Specifically, in arid ecosystems, stronger droughts and rapidly rising annual temperatures are increasing water scarcity and forcing arid landscapes to become more resilient to these environmental changes. Self-organized patchiness of vegetation structure has been observed in arid ecosystems worldwide as a response to water scarcity. Mathematical models have explored the significance of these patterned landscapes and have suggested their existence as a sign of resiliency in arid ecosystems, but also as a possible forewarning of a catastrophic shift to a homogenous bare ecosystem. Several factors, like slope orientation and mechanisms such as positive feedbacks and bistability, create a periodic banded vegetation pattern. We investigated the formation of the periodic banded vegetation patterns in Southern Colorado at Chico Basin Ranch. We expected the landscape at Chico Basin Ranch to start as a spatially random, homogenous landscape that developed periodic patterns over time in response to a change in climate. A Fast Fourier Transform (FFT) analysis method was developed on R Studio and then applied to high resolution imagery of the 1x2 km area of interest for the years 1999, 2003, 2015, 2017 and 2019. The quantitative analysis searched for statistically significant banded vegetation patterns, the dominant waves in each AOI and the orientation of the pattern. Climate trends observed in El Paso County, CO show an upward linear trend in temperature maxima/minima combined with three significant droughts which occurred during the 20-year period of this study. We observed a notable increase in significant banded vegetation patterns after the droughts occurred. We found that there are statistically significant banded vegetation patterns at Chico Basin Ranch and the coverage of significant patterns has increased since 1999 from 14.7% to 36% in 2019 of the AOI. The landscape at Chico Basin did not begin as a spatially random homogenous landscape, as we had originally expected, but rather as a landscape with a low proportion of statistically significant patterns that was not spatially random. Generally, the patterns are oriented at ~90° (North). The effects of climate change could be driving the continued formation of the vegetation patterns at Chico Basin Ranch

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