Geomorphic controls on shrub canopy volume and spacing of creosote bush in northern Mojave Desert, USA
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RESEARCH ARTICLE
Geomorphic controls on shrub canopy volume and spacing of creosote bush in northern Mojave Desert, USA James H. Gearon
. Michael H. Young
Received: 30 June 2020 / Accepted: 27 October 2020 Ó Springer Nature B.V. 2020
Abstract Context Studies on the role of geomorphology on vegetation structure at the basin scale are rarely available and less likely in the future due to access, funding, and potential health risks. Objectives Our goal is to determine the primary abiotic controlling factor(s) on shrub canopy structure using a dataset of approximately 23 million individual shrubs, generated using remote sensing and groundtruthing by Young et al. (in Remote Sens 9(5):16, https://doi.org/10.3390/rs9050458, 2017). We posit that landscape position and local-scale geomorphic features in a desert alluvial fan environment will influence canopy volume and shrub spacing of creosote bush Larrea tridentata. Methods We relate selected characteristics (canopy volume and spatial distribution) of identified L. tridentata to aspect and surface geomorphology at each shrub location. Statistical analyses included K-S testing, distribution fitting, and several generalized
linear models (GLMs). The study was located in Eldorado Valley, Nevada, USA. Results Aspect and surface age have demonstrable influences on both shrub canopy volume and shrub spacing for all 5 geomorphic surfaces studied, with the highest median canopy volumes on east-facing surface (0.758 m3) almost 5 9 larger than the lowest median volumes (0.152 m3) on the WNW-facing surfaces; variability in shrub volume was also higher on eastfacing than west-facing surfaces. Shrub spacing on alluvial flat and fan skirt surfaces (2.418 and 2.333 m, respectively) were larger than older alluvial fan, fan piedmont and fan remnant surfaces (1.776, 1.837 and 1.892 m, respectively). Conclusions Results show a significant relationship between shrub spacing and canopy volume by aspect and geomorphic surface, indicating a threshold at which biotic effects on canopy structure from intraspecies competition transition to abiotic effects governed by geomorphic and climatological factors. Mojave Desert Larrea tridentata Geomorphology Shrub characteristics Soil structure
J. H. Gearon Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78705, USA M. H. Young (&) Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78705, USA e-mail: [email protected]
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Landscape Ecol
Introduction Background Mapping and characterization of arid and semi-arid basins endemic to the American west has a storied history of field mapping by federal, state, and county soil agencies (Gardner 1998). The twenty-first century development of agronomic science and changes in federal and local funding priorities have limited soil mapping of land areas with little to no commercial or residential use. Prime examples of these un-m
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