The elevational ascent and spread of exotic annual grasslands in the Great Basin, USA

In the Great Basin of the U.S., sagebrush (Artemisia spp.) and salt desert shrublands are rapidly transitioning to exotic annual grasslands, a novel and often self-reinforcing state that threatens the economic sustainability and conservation value of western grazing lands. Climate change is predicted to directly and indirectly favor annual grasses, potentially pushing annual grassland transitions into higher elevations. We used recently developed remote sensing-based rangeland vegetation data to retrospectively quantify expansion and elevational range shift of annual grassland transitions in the Great Basin from 1986–2019. During this period, we document an alarming six-fold increase in annual grassland area (to >75,000 km2) occurring at a rate of 1,950 km2 yr-1. Annual grasslands now occupy one fifth of Great Basin rangelands. This rapid expansion has been in part facilitated by a broadening of elevational range limits, with the leading edge of annual grassland transitions moving upslope at 60–110 m decade-1. Accelerated intervention is critically needed to conserve the fragile band of rangelands being compressed between annual grassland transitions at lower elevations and woodland expansion at higher elevations.SignificanceExotic annual grasses became widespread throughout the western U.S. Great Basin in the last century and now rank among the most vexing challenges facing western rangelands. Once established, these invaders can transform native sagebrush (Artemisia spp.) and salt desert shrublands into virtual monocultures of highly flammable exotic annual grasses with severely diminished biological and economic value. Capitalizing on a recently developed remote sensing vegetation product providing continuous spatial and annual temporal coverage of western US rangelands, we map the expansion of exotic annual grasslands over the past three decades. Our analysis reveals the alarming pace at which native shrublands are transitioning to annual grasslands, and confirms the movement of these transitions into ever higher elevations as the climate of the western U.S. warms.

Soil Organic Carbon Pools and Microbial Population in Extremely Saline Soils: A Case Study in Salt Desert of Rann of Kachchh, India

Saline soils are not suitable for plant growth due to higher osmotic potential and impair crop productivity to a great extent. Globally vast tract of land in arid and semiarid regions are affected by salinity and hardly supports any economic activities. Soil acts as the largest sink of terrestrial carbon and can help in climate change mitigation through sequestration of organic carbon. Therefore, an attempt has been made to assess the carbon concentration as well as microbial activity of soils of Rann of Kachchh (salt desert), Gujarat, India. The soil and water samples were found dark black in colour and the water was extremely saline (electrical conductivity>700 dS m-1) in nature. Results showed that the total carbon and oxidizable organic carbon concentration was 7.1 and 5.3 g kg-1 at 0-15 cm soil depth. About 25.4% of the total carbon was present in recalcitrant form. We calculated that the salt desert of Rann of Kachch stored about ~3640 ton carbon at 0-15 cm soil depth. Fungi were absent and bacteria and actinomycetes were found in those soils. These highly saline soils of Rann of Kachchh can serve as a great sink for carbon sequestration with higher stability and help to achieve the goal of “4 per 1000” initiative.

Reactive bromine chemistry in the Rann of Kachchh salt desert

<p>The Rann of Kachchh is a salt desert in the southern border area of India and Pakistan. Recently, high amounts of bromine monoxide (BrO) were observed there in satellite measurements of the Ozone Monitoring Instrument (OMI). Release mechanisms of reactive bromine, dominating chemical processes, the influence of the ambient atmosphere and transport processes, etc. are not well understood in general. Furthermore, due to their short time scales these processes are difficult to assess with satellite instruments, which only offer a single measurement per day with limited spatial resolution.</p><p>Here, we present BrO, HCHO and nitrogen dioxide (NO<sub>2</sub>) measurements from ground-based MAX DOAS performed at two different locations in the Rann of Kachchh salt desert in Gujarat, India during three weeks in March and April 2019. We observe large amounts of BrO building up during daytime reaching maxima of several tens of ppt in the late afternoon. Additional mobile measurements performed directly over the salt gave similar results to the measurements at 5-15 km distance from the salt surface, suggesting that the BrO formation time scale and effective life times during daytime are at least of the order of several minutes to a few hours. Additional in-situ ozone measurements indicate ozone depletion events linked to the episodes of high BrO abundance. This indicates that BrO is formed by bromine atoms reacting with ozone and then being recycled via BrO self-reaction and heterogeneous processes involving aerosol surfaces, as proposed for other environments (Polar Regions, volcanic plumes).</p><p>While we found high but steady HCHO levels, the observed NO<sub>2</sub> levels showed a distinct anti-correlation to BrO, indicating coupling of bromine- and NO<sub>x</sub>-chemistry and thereby the influence of the pollution level of the ambient atmosphere. Formation of bromine nitrate probably delays the formation of large BrO amounts, but might also support the recycling of bromine atoms through heterogeneous chemistry.</p>

Rapid Biodiversity Sampling for Bat Assemblages in Northwestern Nevada

Bat (Chiroptera) assemblages in the western North America remain understudied despite their importance to ecosystem function and vulnerability to multiple anthropogenic stressors. We present the first large-scale survey that we are aware of for bat fauna in the Black Rock Plateau of northwestern Nevada in the northern Great Basin Desert. We conducted surveys using both acoustic and mist net methods, documenting 14 species across 19 sites sampled during a four-night period in August 2016. We surveyed over water sources, usually surrounded by cliff and canyon habitat, and in salt desert scrub, sagebrush, and woodland habitats, detecting multiple sensitive bat species (spotted bat Euderma maculatum, little brown bat Myotis lucifugus, canyon bat Parastrellus hesperus) in the canyon habitats of the High Rock region. We analyzed regional species diversity and present the utility of using multiple detection methods to enhance understanding of Chiroptera biodiversity at both local and regional scales. Our results demonstrate the utility of “BioBlitz” approaches in documenting local and regional diversity and provide insight into areas with species assemblages or vulnerable species. Knowledge of these sites is increasingly important for future disease surveillance and population monitoring.

Barde/askan, the City of Gardens

The article is an attempt to interpret the toponym Bardeskan/Bardaskan, which is the name of a city and a šahrestān (“county”) located in the south of the Khorasan-e Razavi province in Iran, on the northern edge of the Great Salt desert (Kavīr-e namak). Parallelly, the author discusses also the origin of a number of other place-names from the same area.