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Biological soil crusts (biocrusts) are living soil surface aggregates housing communities of microbes. They cover an estimated 12% of the Earth’s surface and provide ecosystem services including soil stability, nutrient cycling, and carbon sequestration. However, the ecological dynamics of biocrust have not been comprehensively described across hot desert ecosystems. Our objective was to investigate how biocrust cover and composition varies within a diverse Chihuahuan Desert landscape using an ecological site and state framework and how this variability translates to ecosystem services. We quantified vegetation characteristics, biocrust cover and composition, ecosystem structure, soil chemical and physical characteristics, and soil stability of 63 plots across the Jornada Experimental Range in southern New Mexico. The plots represented clayey, loamy, and sandy ecological sites and each contained 4-5 alternate ecological states. NMDS ordination was used to identify the influence of ecological site and state on biocrust composition and other soil surface categories while environmental fits revealed relationships between the environmental variables and biocrusts. We found that biocrust cover and composition varied by both ecological site and state, for example, clayey and loamy sites had the greatest biocrust functional group richness but also the greatest variability in cover among states. Sandy had the lowest average biocrust cover and diversity. No consistent direction of change in biocrust cover and composition was found as ecological states departed from reference conditions. Specifically, reference and altered states differed greatly between ecological sites in diversity and composition of crust types. For example, crust diversity was very high and complex lichen cover was highest in the most altered, non-vegetated state of clay sites, but not so in the non-vegetated state of loamy sites. Our findings emphasize how biocrust cover and composition are shaped by ecological site and state drivers which differ from state alteration effects on vascular vegetation, and can thus lead to a more holistic understanding of the dryland landscape and provide novel aspects for land management. 

In the dynamically stepwise reaction pathway C–H insertionversusCope selectivity is highly influenced by whether or not vibrational synchronization occurs in the nonstatistical entropic intermediate. 

Abstract We describe a bundle for UCSF ChimeraX called SEQCROW that provides advanced structure editing capabilities and quantum chemistry utilities designed for complex organic and organometallic compounds. SEQCROW includes graphical presets and bond editing tools that facilitate the generation of publication‐quality molecular structure figures while also allowing users to build molecular structures quickly and efficiently by mapping new ligands onto existing organometallic complexes as well as adding rings and substituents. Other capabilities include the ability to visualize vibrational modes and simulated IR spectra, to compute and visualize molecular descriptors including percent buried volume, ligand cone angles, and Sterimol parameters, to process thermochemical corrections from quantum mechanical computations, to generate input files for ORCA, Psi4, and Gaussian, and to run and manage computational jobs. 

Abstract As the tools of computational quantum chemistry have continued to mature, larger and more complex molecular systems have become amenable to computational study. However, studies of these complex systems often require the execution of enormous numbers of computations, which can be a tedious and error‐prone process if done manually. We have developed a suite of free, open‐source tools to facilitate the automation of quantum chemistry workflows. These tools are collected under the organization QChASM (Quantum Chemistry Automation and Structure Manipulation) and include functionality for building and manipulating complex molecular structures and performing routine tasks (AaronTools), a toolkit for automating TS optimizations and predictions of the outcomes of selective homogeneous catalytic reactions, and a plug‐in for UCSF ChimeraX that provides a graphical interface for building complex molecular structures and representing output from quantum chemistry computations. These tools are described below, with a focus on the recent Python implementation of AaronTools. This article is categorized under:Structure and Mechanism > Reaction Mechanisms and CatalysisSoftware > Quantum Chemistry