Biological Soil Crusts of the Great Plains: A Review

Biological soil crusts (BSCs), or biocrusts, are composed of fungi, bacteria, algae, and bryophytes (mosses, etc.) that occupy bare soil, entwining soil particles with filaments or rootlike structures and/or gluing them together with polysaccharide exudates to form a consolidated surface crust that stabilizes the soil against erosion. BSCs are common in arid and semiarid regions where vascular plant cover is naturally sparse, maximizing the exposure of surface-dwelling organisms to direct sunlight. Although less prominent and less studied there, BSC organisms are also present in more mesic areas such as the Great Plains where they can be found in shortgrass and mixed-grass prairie, in the badlands of several states, where burrowing animals have created patches of bare soil, on damaged road-cuts, strip-mines, gas and oil drill pads, military training areas, heavily grazed areas, and burn scars. Even where BSCs are not readily visible to the naked eye, many of the organisms are still present. BSC organisms are passively dispersed to the Great Plains as airborne organismal fragments, asexual diaspores, or sexual spores that accompany wind-blown dust from as far away as northern China and Mongolia. BSCs can best be studied and managed by 1) acknowledging their presence; 2) documenting their diversity, abundance, and functional roles; and 3) minimizing unnecessary disturbance, particularly when the soils are dry. This paper describes the current knowledge of Great Plains BSCs in an effort to heighten awareness of these cryptic but crucial ecosystem components and to encourage new research initiatives to better understand and manage them in this biome. Some specific actions may include refined taxonomic and ecologic studies of BSC organisms in underexplored areas, particularly those previously less or not recognized as BSC habitat, and incorporation of techniques to sample airborne organisms

\u3cem\u3eBromus tectorum\u3c/em\u3e Litter Alters Photosynthetic Characteristics of Biological Soil Crusts from a Semiarid Shrubland

Invasion by the exotic annual grass Bromus tectorum has increased the cover and connectivity of fine litter in the sagebrush steppes of western North America. This litter tends to cover biological soil crusts, which could affect their metabolism and growth. To investigate this possible phenomenon, biological soil crusts dominated by either the moss Bryum argenteum or the lichen Diploschistes muscorum were covered with B.tectorum litter (litter treatment) or left uncovered (control treatment) and exposed to natural field conditions. After periods of five and ten months, we removed the litter and compared the photosynthetic performance of biological soil crusts from the two treatments. Litter induced photosynthetic changes in our samples. In bothB. argenteum and D. muscorum, biological soil crusts that had been covered with litter for ten months had lower rates of gross photosynthesis and lower chlorophyll content than control samples. Similarly in both biological soil crust types, litter reduced the rate of dark respiration. For D. muscorum, the reduction in dark respiration fully compensated for the decrease in gross photosynthesis, resulting in similar values of net photosynthesis in the two treatments. In contrast, for B. argenteum, net photosynthesis was four-times greater in the control than the litter treatment. Also under litter cover, D. muscorum showed three common adaptations to shade conditions: a decrease in the light compensation point, in the light intensity needed to achieve 95% of maximal net photosynthesis, and in the chlorophyll a/b ratio. None of these changes was apparent in B. argenteum. Overall, our results indicate that photosynthetic responses to the presence of litter varied among species of the crust biota and that the litter can reduce the photosynthetic capacity of biological soil crusts. These results help to explain field observations of decreases in biological soil crust cover and changes in biological soil crust composition with increases in litter cover, and suggest that the landscape-wide invasion by B. tectorum may have substantial effects on biological soil crust performance and therefore their capacity to function in semiarid shrublands

The climate benefit of seagrass blue carbon is reduced by methane fluxes and enhanced by nitrous oxide fluxes

Blue carbon is carbon stored long-term in vegetated coastal ecosystems, which constitutesan important sink for atmospheric carbon dioxide (CO2). However, because methane (CH4)and nitrous oxide (N2O) have higher global warming potentials (GWP) than CO2, theirproduction and release during organic matter diagenesis can affect the climate benefit of bluecarbon. Here, we present a meta-analysis synthesizing seagrass CH4 and N2O fluxes andlong-term organic carbon burial rates, and use these data to estimate the reduced climatebenefit (offsets) of seagrass blue carbon using three upscaling approaches. Mean offsets forindividual seagrass species (34.7% GWP20;1.0% GWP100) and globally (33.4% GWP20;7.0%GWP100) were similar, but GWP20 offsets were higher, and GWP100 offsets were lower thanglobally, for the Australian region (41.3% GWP20;1.1% GWP100). This study highlights theimportance of using long-term organic carbon burial rates and accounting for both CH4 andN2O fluxes in future seagrass blue carbon assessments.Blue carbon is carbon stored long-term in vegetated coastal ecosystems, which constitutes an important sink for atmospheric carbon dioxide (CO2). However, because methane (CH4) and nitrous oxide (N2O) have higher global warming potentials (GWP) than CO2, their production and release during organic matter diagenesis can affect the climate benefit of blue carbon. Here, we present a meta-analysis synthesizing seagrass CH4 and N2O fluxes and long-term organic carbon burial rates, and use these data to estimate the reduced climate benefit (offsets) of seagrass blue carbon using three upscaling approaches. Mean offsets for individual seagrass species (34.7% GWP20;1.0% GWP100) and globally (33.4% GWP20;7.0% GWP100) were similar, but GWP20 offsets were higher, and GWP100 offsets were lower than globally, for the Australian region (41.3% GWP20;1.1% GWP100). This study highlights the importance of using long-term organic carbon burial rates and accounting for both CH4 and N2O fluxes in future seagrass blue carbon assessments.</p

Coronin-1C Protein and Caveolin Protein Provide Constitutive and Inducible Mechanisms of Rac1 Protein Trafficking

Sustained directional fibroblast migration requires both polarized activation of the protrusive signal, Rac1, and redistribution of inactive Rac1 from the rear of the cell so that it can be redistributed or degraded. In this work, we determine how alternative endocytic mechanisms dictate the fate of Rac1 in response to the extracellular matrix environment. We discover that both coronin-1C and caveolin retrieve Rac1 from similar locations at the rear and sides of the cell. We find that coronin-1C-mediated extraction, which is responsible for Rac1 recycling, is a constitutive process that maintains Rac1 protein levels within the cell. In the absence of coronin-1C, the effect of caveolin-mediated endocytosis, which targets Rac1 for proteasomal degradation, becomes apparent. Unlike constitutive coronin-1C-mediated trafficking, caveolin-mediated Rac1 endocytosis is induced by engagement of the fibronectin receptor syndecan-4. Such an inducible endocytic/degradation mechanism would predict that, in the presence of fibronectin, caveolin defines regions of the cell that are resistant to Rac1 activation but, in the absence of fibronectin leaves more of the membrane susceptible to Rac1 activation and protrusion. Indeed, we demonstrate that fibronectin-stimulated activation of Rac1 is accelerated in the absence of caveolin and that, when caveolin is knocked down, polarization of active Rac1 is lost in FRET experiments and culminates in shunting migration in a fibrous fibronectin matrix. Although the concept of polarized Rac1 activity in response to chemoattractants has always been apparent, our understanding of the balance between recycling and degradation explains how polarity can be maintained when the chemotactic gradient has faded

Biodegradable collagen matrix implant vs mitomycin-C as an adjuvant in trabeculectomy: a 24-month, randomized clinical trial

AIM: To verify the safety and efficacy of Ologen (OLO) implant as adjuvant compared with low-dosage mitomycin-C (MMC) in trabeculectomy. METHODS: This was a prospective randomized clinical trial with a 24-month follow-up. Forty glaucoma patients (40 eyes) were assigned to trabeculectomy with MMC or OLO. Primary outcome includes target IOP at ≤21, ≤17, and ≤15 mm Hg; complete (target IOP without medications), and qualified success (target IOP regardless of medications). Secondary outcomes include bleb evaluation, according to Moorfields Bleb Grading System (MBGS); spectral domain optical coherence tomography (SD-OCT) examination; number of glaucoma medications; and frequency of postoperative adjunctive procedures and complications. RESULTS: The mean preoperative IOP was 26.5 (±5.2) in MMC and 27.3 (±6.0) in OLO eyes, without statistical significance. One-day postoperatively, the IOP dropped to 5.2 (±3.5) and 9.2 (±5.5) mm Hg, respectively (P=0.009). The IOP reduction was significant at end point in all groups (P=0.01), with a mean IOP of 16.0 (±2.9) and 16.5 (±2.1) mm Hg in MMC and OLO, respectively. The rates and Kaplan-Meier curves did not differ for both complete and qualified success at any target IOP. The bleb height in OLO group was higher than MMC one (P<0.05). SD-OCT analysis of successful/unsuccessful bleb in patients with or without complete success at IOP ≤17  mm Hg indicated a sensitivity of 83% and 73% and a specificity of 75% and 67%, respectively, for MMC and OLO groups. No adverse reaction to OLO was noted. CONCLUSIONS: Our results suggest that OLO implant could be a new, safe, and effective alternative to MMC, with similar long-term success rate

Shotgun Sequencing Decades-Old Lichen Specimens to Resolve Phylogenomic Placement of Type Material

Natural history collections, including name-bearing type specimens, are an important source of genetic information. These data can be critical for appropriate taxonomic revisions in cases where the phylogenetic position of name-bearing type specimens needs to be identified, including morphologically cryptic lichen-forming fungal species. Here, we use high-throughput metagenomic shotgun sequencing to generate genome-scale data from decades-old (i.e., more than 30 years old) isotype specimens representing three vagrant taxa in the lichen-forming fungal genus Rhizoplaca, including one species and two subspecies. We also use data from high-throughput metagenomic shotgun sequencing to infer the phylogenetic position of an enigmatic collection, originally identified as R. haydenii, that failed to yield genetic data via Sanger sequencing. We were able to construct a 1.64 Mb alignment from over 1200 single-copy nuclear gene regions for the Rhizoplaca specimens. Phylogenomic reconstructions recovered an isotype representing Rhizoplaca haydenii subsp. arbuscula within a clade comprising other specimens identified as Rhizoplaca haydenii subsp. arbuscula, while an isotype of R. idahoensis was recovered within a clade with substantial phylogenetic substructure comprising Rhizoplaca haydenii subsp. haydenii and other specimens. Based on these data and morphological differences, Rhizoplaca haydenii subsp. arbuscula is elevated to specific rank as Rhizoplaca arbuscula. For the enigmatic collection, we were able to assemble the nearly complete nrDNA cistron and over 50 Mb of the mitochondrial genome. Using these data, we identified this specimen as a morphologically deviant form representing Xanthoparmelia aff. subcumberlandia. This study highlights the power of high-throughput metagenomic shotgun sequencing in generating larger and more comprehensive genetic data from taxonomically important herbarium specimens

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

Bromus tectorum litter alters photosynthetic characteristics of biological soil crusts from a semiarid shrubland

a b s t r a c t Invasion by the exotic annual grass Bromus tectorum has increased the cover and connectivity of fine litter in the sagebrush steppes of western North America. This litter tends to cover biological soil crusts, which could affect their metabolism and growth. To investigate this possible phenomenon, biological soil crusts dominated by either the moss Bryum argenteum or the lichen Diploschistes muscorum were covered with B. tectorum litter (litter treatment) or left uncovered (control treatment) and exposed to natural field conditions. After periods of five and ten months, we removed the litter and compared the photosynthetic performance of biological soil crusts from the two treatments. Litter induced photosynthetic changes in our samples. In both B. argenteum and D. muscorum, biological soil crusts that had been covered with litter for ten months had lower rates of gross photosynthesis and lower chlorophyll content than control samples. Similarly in both biological soil crust types, litter reduced the rate of dark respiration. For D. muscorum, the reduction in dark respiration fully compensated for the decrease in gross photosynthesis, resulting in similar values of net photosynthesis in the two treatments. In contrast, for B. argenteum, net photosynthesis was four-times greater in the control than the litter treatment. Also under litter cover, D. muscorum showed three common adaptations to shade conditions: a decrease in the light compensation point, in the light intensity needed to achieve 95% of maximal net photosynthesis, and in the chlorophyll a/b ratio. None of these changes was apparent in B. argenteum. Overall, our results indicate that photosynthetic responses to the presence of litter varied among species of the crust biota and that the litter can reduce the photosynthetic capacity of biological soil crusts. These results help to explain field observations of decreases in biological soil crust cover and changes in biological soil crust composition with increases in litter cover, and suggest that the landscape-wide invasion by B. tectorum may have substantial effects on biological soil crust performance and therefore their capacity to function in semiarid shrublands

Advances in understanding of air-sea exchange and cycling of greenhouse gases in the upper ocean

\ua9 2024 University of California Press. All rights reserved. The air–sea exchange and oceanic cycling of greenhouse gases (GHG), including carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), carbon monoxide (CO), and nitrogen oxides (NOx \ubc NO \ufe NO2), are fundamental in controlling the evolution of the Earth’s atmospheric chemistry and climate. Significant advances have been made over the last 10 years in understanding, instrumentation and methods, as well as deciphering the production and consumption pathways of GHG in the upper ocean (including the surface and subsurface ocean down to approximately 1000 m). The global ocean under current conditions is now well established as a major sink for CO2, a major source for N2O and a minor source for both CH4 and CO. The importance of the ocean as a sink or source of NOx is largely unknown so far. There are still considerable uncertainties about the processes and their major drivers controlling the distributions of N2O, CH4, CO, and NOx in the upper ocean. Without having a fundamental understanding of oceanic GHG production and consumption pathways, our knowledge about the effects of ongoing major oceanic changes—warming, acidification, deoxygenation, and eutrophication—on the oceanic cycling and air–sea exchange of GHG remains rudimentary at best. We suggest that only through a comprehensive, coordinated, and interdisciplinary approach that includes data collection by global observation networks as well as joint process studies can the necessary data be generated to (1) identify the relevant microbial and phytoplankton communities, (2) quantify the rates of ocean GHG production and consumption pathways, (3) comprehend their major drivers, and (4) decipher economic and cultural implications of mitigation solutions

Nutrient Cycling in Tropical and Temperate Coastal Waters: Is Latitude Making a Difference?

Tropical coastal waters are highly dynamic and amongst the most biogeochemically active zones in the ocean. This review compares nitrogen (N) and phosphorus (P) cycles in temperate and tropical coastal waters. We review the literature to identify major similarities and differences between these two regions, specifically with regards to the impact of environmental factors (temperature, sunlight), riverine inputs, groundwater, lateral fluxes, atmospheric deposition, nitrogen fixation, organic nutrient cycling, primary production, respiration, sedimentary burial, denitrification and anammox. Overall, there are some similarities but also key differences in nutrient cycling, with differences relating mainly to temperature, sunlight, and precipitation amounts and patterns. We conclude that due to the differences in biogeochemical processes, we cannot directly apply cause and effect relationships and models from temperate systems in tropical coastal waters. Our review also highlights the considerable gaps in knowledge of the biogeochemical processes of tropical coastal waters compared with temperate systems. Given the ecological and societal importance of tropical coastal waters, we hope that highlighting the differences and similarities to temperate systems as well as the existing gaps, will inspire further studies on their biogeochemical processes. Such knowledge will be essential to better understand and forecast impacts on tropical coastal nutrient cycling at local, regional, and global scales