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Kent State University (2021)

Factors that inhibit and promote biocrust cover and functionality

Baldarelli, Lauren Marie

Titre : Factors that inhibit and promote biocrust cover and functionality

Auteur : Baldarelli, Lauren Marie

Université de soutenance : Kent State University,

Grade : Doctor of Philosophy (PhD) 2021

The overall motivations of this work were to better understand anthropogenic and environmental factors that can both inhibit or destroy, as well as promote biological soil crusts (biocrusts) in the North American southwest. Biocrusts are living mats that occupy the first few millimeters of soils in arid environments around the globe. They contribute to many ecosystem services including soil stabilization and nitrogen fixation. The specific research questions of this dissertation aim to unpack to complexity of these unique, specialized organisms capable of inhancing arid environments. The research here was approached from manuipulative and observational frameworks to increase our understanding of the ecology of biocrusts. Chapter I is an introduction to biocrusts, and the broader ecological concepts covered as part of this dissertation. In Chapter II, I present the research that was completed within the Nutrient Network (NutNet) framework at the Sevilleta, New Mexico. Here we showed that vascular plants respond positively to nutrients and consequently outcompete biocrusts for space. Chapter III represents the potential negative effects that nutrient deposition can have on nitrogen fixation of biocrusts. This study was done at the Jornada Basin Long-Term Ecological Research site in southern New Mexico. We also determined that encroaching shrubs were responsible for contributing more fixed nitrogen to the landscape compared to biocrusts, at least prior to the monsoon season. Chapter IV demonstrates the negative effect that livestock trampling has on the cover and function of biocrusts. We did this study at the Santa Rita Experimental Range in southern Arizona. We found that biocrust cover increased with increasing distance from watering holes within a piosphere framework. Chapter V illustrates the effects of elevation and soil parent material on biocrust cover and enzyme activity. This study was done between Phoenix (low elevation) and Flagstaff (high elevation) in Arizona. We found that elevation and soil parent material have significant effects on biocrust cover. Lastly, Chapter VI highlights our conclusions from this work as a whole and suggests future research.


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