Biocrusts Indicators of Livestock Grazing Effects on Soil Stability in Sagebrush Steppe: A Case Study from a Long-Term Experiment in the Northern Great Basin

Biocrusts are sensitive to changes in livestock grazing intensity in arid rangelands and may be useful indicators of ecosystem functions, particularly soil properties like soil stability, which may suggest the potential for soil erosion. We compared biocrust community composition and surface soil stability in a big sagebrush (Artemisia tridentata) steppe rangeland in the northwestern Great Basin in several paired sites, with or without long-term cattle grazing exclusion, and similar soils (mostly sandy loams), climate, and vegetation composition. We found that livestock grazing was associated with both lower surface soil stability and cover of several biocrust morphogroups, especially lichens, compared with sites with long-term livestock exclusion. Surface soil stability did not modify the effects of grazing on most biocrust components via interactive effects. Livestock grazing effects on total biocrust cover were partially mediated by changes in surface soil stability. Though lichens were more sensitive to grazing disturbance, our results suggest that moss (mostly Tortula ruralis in this site) might be a more readily observable indicator of grazing-related soil stability change in this area due to their relatively higher abundance compared with lichens (moss: mean, 8.5% cover, maximum, 96.1%, lichens: mean, 1.0% cover, maximum, 14.1%). These results highlight the potential for biocrust components as sensitive indicators of change in soil-related ecosystem functions in sagebrush steppe rangelands. However, further research is needed to identify relevant indicator groups across the wide range of biocrust community composition associated with site environmental characteristics, variable grazing systems, other rangeland health metrics, and other disturbance types such as wildfire

Chronic, intermittent treatment with a cannabinoid receptor agonist impairs recognition memory and brain network functional connectivity

Elucidating how cannabinoids affect brain function is instrumental for the development of therapeutic tools aiming to mitigate 'on target' side effects of cannabinoid based therapies. A single treatment with the cannabinoid receptor agonist, WIN 55,212-2, disrupts recognition memory in mice. Here we evaluate how prolonged, intermittent (30 days) exposure to WIN 55,212-2 (1mg/kg) alters recognition memory and impacts on brain metabolism and functional connectivity. We show that chronic, intermittent treatment with WIN 55,212-2 disrupts recognition memory (Novel Object Recognition Test) without affecting locomotion and anxiety-like behaviour (Open Field and Elevated Plus Maze). Through 14 C-2-deoxyglucose functional brain imaging we show that chronic, intermittent WIN 55,212-2 exposure induces hypometabolism in the hippocampal dorsal subiculum and in the mediodorsal nucleus of the thalamus, two brain regions directly involved in recognition memory. In addition, WIN 55,212-2 exposure induces hypometabolism in the habenula with a contrasting hypermetabolism in the globus pallidus. Through the application of the Partial Least Squares Regression (PLSR) algorithm to the brain imaging data, we observed that prolonged WIN 55,212-2 administration alters functional connectivity in brain networks that underlie recognition memory, including that between the hippocampus and prefrontal cortex, the thalamus and prefrontal cortex, and between the hippocampus and the perirhinal cortex. In addition, our results support disturbed lateral habenula and serotonin system functional connectivity following WIN 55,212-2 exposure. Overall, this study provides new insight into the functional mechanisms underlying the impact of chronic cannabinoid exposure on memory and highlights the serotonin system as a particularly vulnerable target. This article is protected by copyright. All rights reserved

Shading and litter mediate the effects of soil fertility on the performance of an understorey herb

Background and aimsSoil fertility and topographic microclimate are common determinants of plant species distributions. However, biotic conditions also vary along these abiotic gradients, and may mediate their effects on plants. In this study, we investigated whether soils and topographic microclimate acted directly on the performance of a focal understorey plant, or indirectly via changing biotic conditions.MethodsWe examined direct and indirect relationships between abiotic variables (soil fertility and topographic microclimate) and biotic factors (overstorey and understorey cover, litter depth and mycorrhizal colonization) and the occurrence, density and flowering of a common understorey herb, Trientalis latifolia, in the Klamath-Siskiyou Mountains, Oregon, USA.ResultsWe found that the positive effects of soil fertility on Trientalis occurrence were mediated by greater overstorey shading and deeper litter. However, we did not find any effects of topographic microclimate on Trientalis distribution that were mediated by the biotic variables we measured. The predictive success of Trientalis species distribution models with soils and topographic microclimate increased by 12 % with the addition of the biotic variables.ConclusionsOur results reinforce the idea that species distributions are the outcome of interrelated abiotic gradients and biotic interactions, and suggest that biotic conditions, such as overstorey density, should be included in species distribution models if data are available

Core_Dataset

This datasheet contains the core data by individual and plot for the manuscript, including environmental data, Trientalis traits, and community traits. See the Core_Dataset_Metadata.csv for details

Data from: Community traits affect plant–plant interactions across climatic gradients

Plant abundances and demography often vary along gradients of environmental stress, and neighboring plants can amplify or diminish such variation. We asked to what degree the effects of neighboring plants on a focal species can be explained by the traits and abundances of species in the surrounding community. We studied a common understory herb, Trientalis latifolia, across climatic gradients created by topography in the Siskiyou Mountains, southwestern Oregon. We compared Trientalis fitness along these gradients with and without neighbor removal, and asked whether the effects of neighboring plants could be predicted by their community-weighted trait values and abundances. Environmental conditions alone did not explain whether neighbors had competitive or facilitative effects on Trientalis. However, the environment interacted with neighbor traits and biomass to influence neighbor effects: at cool, higher elevations, high neighbor biomass was associated with stronger facilitative effects, while at warm, lower elevations, high neighbor dissimilarity from Trientalis was associated with stronger competitive effects. We suggest that covariation and interactions among environmental and community characteristics are key to understanding species performance along climatic gradients

Core_Dataset_Metadata

Metadata with column definitions and units for Core_Dataset.cs

RII_Trait_Metadata

Metadata file with column descriptions and units for the RII_Traits.csv file