Search

A rapid renewable energy transition has facilitated the development of large, ground‐mounted solar energy facilities worldwide. Deserts, and other sensitive aridland ecosystems, are the second most common land‐cover type for solar energy development globally. Thus, it is necessary to understand existing diversity within environmentally sensitive desert plant populations to understand spatiotemporal effects of solar energy siting and design. Overall, few population genomic studies of desert plants exist, and much of their biology is unknown. To help fill this knowledge gap, we sampled Mojave milkweed (Asclepias nyctaginifolia) in and around the Ivanpah Solar Electric Generating Station (ISEGS) in the Mojave Desert of California to understand the species' population structure, standing genetic variation, and how that intersects with solar development. We performed Restriction‐site Associated Sequencing (RADseq) and discovered 9942 single nucleotide polymorphisms (SNPs). Using these data, we found clear population structure over small spatial scales, suggesting each site sampled comprised a genetically distinct population of Mojave milkweed. While mowing, in lieu of blading, the vegetation across the solar energy facility's footprint prevented the immediate loss of the ISEGS Mojave milkweed population, we show that the effects of land‐cover change, especially those impacting desert washes, may impact long‐term genetic diversity and persistence. Potential implications of this include a risk of overall loss of genetic diversity, or even hastened extirpation. These findings highlight the need to consider the genetic diversity of impacted species when predicting the impact and necessary conservation measures of large‐scale land‐cover changes on species with small population sizes. [ABSTRACT FROM AUTHOR]

We studied a rodent community in the San Joaquin Desert of California, United States, from 1993 to 2016. Using biannual trapping on a 144-trap plot, we found that mice of various species were rarely caught in appreciable numbers in contrast to many other studies of rodent communities in arid North America. Most captures were made of 3 species of kangaroo rats: giant kangaroo rat (Dipodomys ingens), Heermann's kangaroo rat (D. heermanni), and San Joaquin kangaroo rat (D. nitratoides). The site was dominated by D. ingens, which, in many years, was the only kangaroo rat captured. Precipitation varied extremely across the study period with 2 periods of high rainfall and 2 periods of well-below-average rainfall. The rodent community seems to have been responding to both bottom-up control and the competitive dominance of D. ingens. In particular, our trapping showed 2 complete cycles of abundance of D. ingens, from very high numbers to crashes with either no or only 2 individuals caught during a session. In both cases, the species recovered after these crashes in abundance. Although we found some D. ingens living to 4-5 years, and D. heermanni and D. nitratoides living up to 3 years, annual survivorship estimates were low compared with other studies of kangaroo rats. Other studies, however, were of much shorter duration and therefore may have missed eventual downturns in population abundances. Dipodomys ingens is a protected species, and from a conservation standpoint, our data indicate that populations can be highly resilient even in the face of high environmental variability. [ABSTRACT FROM AUTHOR]

The article discusses the biological impact of the Ivanpah Solar Electric Generating System thermal power plant on the Mohave Desert region in California, and it mentions several bird deaths, as well as the environmental impact of a mandate for rapid solar development in the U.S. The U.S. Bureau of Land Management's compliance with the country's National Environmental Policy Act of 1969 is mentioned, along with the Environmental Impact Statement process and wildlife protection efforts.

Examines the patterns of the development of desert pavements as a function of elevation in the Mojave Desert. Pavement density; Rate of pebble density fall with elevation increase; Distribution of vegetation change; Evidence for rapid deformation of pavements; Implications for rock varnish dating.

Investigates the disruption of ancient, varnished desert pavement surfaces near Death Valley National Park in California. Association between the increased levels of bioturbation and enhanced vegetation growth; Effect of El Nino precipitation on vegetation growth; Indication of the occurrence of abundant varnished clasts.

Shows the impact of elevated levels of atmospheric carbon dioxide in the Mojave Desert ecosystem. Effects on new shoot production in a dominant perennial shrub in high rainfall and drought years; Effect on above-ground production and seed rain of an invasive annual grass; Conclusion that elevated carbon dioxide levels could lead to the long-term success and dominance of exotic annual grasses, which have the potential to accelerate the fire cycle, reduce biodiversity and alter ecosystem function in the deserts of western North America.

Explores the relationship between perennial dessert shrubs Atriplex hymenelytra Wats and Tidestromia oblongifolia Standl in Death Valley, California. Peak growth activity; Wats' conservative water use; Standl's lack of stomatal restriction of water loss; Interspecific competition.

Butterfly–host plant relationships can inform our understanding of ecological and trophic interactions that contribute to ecosystem function, resiliency, and services. The ecology of danaid–milkweed (Apocynaceae) host plant interactions has been studied in several biomes but is neglected in deserts. Our objective was to determine effects of plant traits, seasonality, and landscape-level host plant availability on selection of Mojave milkweed (Asclepias nyctaginifolia A. Gray) by ovipositing monarch butterflies (Danaus plexippusplexippus) and queen butterflies (Danaus gilippus thersippus) in the Californian Mojave Desert. We surveyed all known Mojave milkweed locations in the Ivanpah Valley, California (n = 419) during early, mid-, and late spring in 2017. For each survey, we counted monarch and queen butterfly eggs on each Mojave milkweed plant. We also measured canopy cover, height, volume, and reproductive stage of each Mojave milkweed plant. We counted a total of 276 queen butterfly eggs and zero monarch butterfly eggs on Mojave milkweed host plants. We determined that count of queen butterfly eggs significantly increased with increasing Mojave milkweed canopy cover. Additionally, count of queen butterfly eggs was: (1) greater on adult Mojave milkweed plants than on juvenile and seedling plants and greater on juvenile Mojave milkweed plants than on seedling plants; and (2) greater during early spring than mid-spring—we recorded no eggs during late spring. Based on aggregation indices, queen butterfly eggs occurred on Mojave milkweed plants in a nonrandom, clustered pattern throughout the Ivanpah Valley. We provide the first evidence of trophic interactions between queen butterflies and Mojave milkweed at multiple spatial scales in the Mojave Desert, suggesting that conservation and management practices for both species should be implemented concurrently. Given its role as an herbivore, pollinator and prey, the queen butterfly may serve as a model organism for understanding effects of anthropogenic disturbance (e.g., solar energy development) on "bottom-up" and trophic interactions among soils, plants and animals in desert ecosystems. [ABSTRACT FROM AUTHOR]

Upscaled soil hydraulic properties are needed for many large-scale hydrologic applications such as regional and global climate studies and investigations of land-atmosphere interactions. Many larger scale subsurface flow and contaminant transport studies also require upscaled hydraulic property estimates. The objectives of this study were to develop a methodology for upscaling hydraulic property functions using a p-norm approach, to examine how p-norm values differ for two commonly used soil hydraulic property models (the Gardner and van Genuchten functions), and to investigate the relative sensitivities of p-norms and the effective hydraulic parameters to the degree of soil heterogeneity (expressed in terms of variances and auto-correlation lengths of the hydraulic parameters) and other environmental conditions. The p-norm approach expresses upscaling schemes such that it reduces their sensitivity to uncertainties (heterogeneities) in site conditions. The upscaling schemes are obtained as the result of two new criteria proposed to upscale soil hydraulic properties in this study--one preserving the ensemble vertical moisture flux across the land-atmosphere boundary, and a second preserving the ensemble soil surface moisture content. The effective soil hydraulic parameters of a heterogeneous soil formation are then derived by conceptualizing the formation as an equivalent homogeneous medium that satisfies the upscaling criteria. Upscaling relationships between the Gardner and van Genuchten models can then also be established for steady-state vertical flow using the statistical structures of the hydraulic parameters of these two models as estimated from field measurements. The upscaling scheme is demonstrated using hydraulic property data collected at 84 locations across a site in the Mojave Desert. Our results show that the p-norms generally vary less in magnitude than the effective parameters when the variances of the hydraulic parameters increase. We also show that, in general, p-norm values are better defined for the van Genuchten model than the Gardner model. Hydraulic parameter auto correlations, as defined by correlation lengths, were found to have little impact in relating the upscaling schemes (p-norm values) for the two hydraulic property models, but correlation between the hydraulic parameters within the hydraulic property models can significantly affect p-norm relationships. [ABSTRACT FROM AUTHOR]