Blowouts in the Nebraska Sandhills: The Habitat of \u3ci\u3ePenstemon haydenii\u3c/i\u3e

The Nebraska Sandhills is the largest area of sand dunes in the Western Hemisphere, occupying over 5 million ha in northcentral Nebraska. The rolling to steep dunes range in height from a few meters to over 60 m. Soils are poorly developed in wind deposited sand. The continental climate is characterized by 425 to 625 mm of annual precipitation, an average annual temperature of 10 C, and a frost-free period of 130-155 days. Upland vegetation is primarily tall grasses and midgrasses such as sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fern.], prairie sandreed [CaLamovilfa Longifolia (Hook.) Scribn.], little bluestem [Schizachyrium scoparium (Michx.) Nash], and switchgrass (Panicum virgatum L.). Forbs are common. Wind erosion occurs when the protective cover of vegetation is destroyed. Blowouts are active sites of erosion. Blowouts are irregular or conical craters formed when the deep, loose sands are removed by swirling action of the prevailing northwesterly winds. Blowout penstemon (Penstemon haydenii S. Wats.) is only found on these sites of active wind erosion and is an early successional species. Important associated species in blowouts include blowout grass [Redfieldia flexuosa (Thurb.) Vasey] and lemon scurfpea (Psoralea Lanceolata Pursh). The number of blowouts has decreased with the control of fire and improved range management techniques. Loss of suitable habitat is one of the reasons for the decline of blowout penstemon. At the same time, there are many blowouts in the Sandhills that seem to offer suitable habitat where blowout penstemon is not found

Blowouts in the Nebraska Sandhills: The Habitat of \u3ci\u3ePenstemon haydenii\u3c/i\u3e

The Nebraska Sandhills is the largest area of sand dunes in the Western Hemisphere, occupying over 5 million ha in northcentral Nebraska. The rolling to steep dunes range in height from a few meters to over 60 m. Soils are poorly developed in wind deposited sand. The continental climate is characterized by 425 to 625 mm of annual precipitation, an average annual temperature of 10 C, and a frost-free period of 130-155 days. Upland vegetation is primarily tall grasses and midgrasses such as sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fern.], prairie sandreed [CaLamovilfa Longifolia (Hook.) Scribn.], little bluestem [Schizachyrium scoparium (Michx.) Nash], and switchgrass (Panicum virgatum L.). Forbs are common. Wind erosion occurs when the protective cover of vegetation is destroyed. Blowouts are active sites of erosion. Blowouts are irregular or conical craters formed when the deep, loose sands are removed by swirling action of the prevailing northwesterly winds. Blowout penstemon (Penstemon haydenii S. Wats.) is only found on these sites of active wind erosion and is an early successional species. Important associated species in blowouts include blowout grass [Redfieldia flexuosa (Thurb.) Vasey] and lemon scurfpea (Psoralea Lanceolata Pursh). The number of blowouts has decreased with the control of fire and improved range management techniques. Loss of suitable habitat is one of the reasons for the decline of blowout penstemon. At the same time, there are many blowouts in the Sandhills that seem to offer suitable habitat where blowout penstemon is not found

Random forest explorations for URL classification

Phishing is a major concern on the Internet today and many users are falling victim because of criminal’s deceitful tactics. Blacklisting is still the most common defence users have against such phishing websites, but is failing to cope with the increasing number. In recent years, researchers have devised modern ways of detecting such websites using machine learning. One such method is to create machine learnt models of URL features to classify whether URLs are phishing. However, there are varying opinions on what the best approach is for features and algorithms. In this paper, the objective is to evaluate the performance of the Random Forest algorithm using a lexical only dataset. The performance is benchmarked against other machine learning algorithms and additionally against those reported in the literature. Initial results from experiments indicate that the Random Forest algorithm performs the best yielding an 86.9% accuracy

Blowouts in the Nebraska Sandhills: The Habitat of \u3ci\u3ePenstemon haydenii\u3c/i\u3e

The Nebraska Sandhills is the largest area of sand dunes in the Western Hemisphere, occupying over 5 million ha in northcentral Nebraska. The rolling to steep dunes range in height from a few meters to over 60 m. Soils are poorly developed in wind deposited sand. The continental climate is characterized by 425 to 625 mm of annual precipitation, an average annual temperature of 10 C, and a frost-free period of 130-155 days. Upland vegetation is primarily tall grasses and midgrasses such as sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fern.], prairie sandreed [CaLamovilfa Longifolia (Hook.) Scribn.], little bluestem [Schizachyrium scoparium (Michx.) Nash], and switchgrass (Panicum virgatum L.). Forbs are common. Wind erosion occurs when the protective cover of vegetation is destroyed. Blowouts are active sites of erosion. Blowouts are irregular or conical craters formed when the deep, loose sands are removed by swirling action of the prevailing northwesterly winds. Blowout penstemon (Penstemon haydenii S. Wats.) is only found on these sites of active wind erosion and is an early successional species. Important associated species in blowouts include blowout grass [Redfieldia flexuosa (Thurb.) Vasey] and lemon scurfpea (Psoralea Lanceolata Pursh). The number of blowouts has decreased with the control of fire and improved range management techniques. Loss of suitable habitat is one of the reasons for the decline of blowout penstemon. At the same time, there are many blowouts in the Sandhills that seem to offer suitable habitat where blowout penstemon is not found

Effects of past and current drought on the composition and diversity of soil microbial communities

Drought is well known to have strong effects on the composition and activity of soil microbial communities, and may be determined by drought history and drought duration, but the characterisation and prediction of these effects remains challenging. This is because soil microbial communities that have previously been exposed to drought may change less in response to subsequent drought events, due to the selection of drought-resistant taxa. We set up a 10-level drought experiment to test the effect of water stress on the composition and diversity of soil bacterial and fungal communities. We also investigated the effect of a previous long-term drought on communities in soils with different historical precipitation regimes. Saplings of the holm oak, Quercus ilex L., were included to assess the impact of plant presence on the effects of the drought treatment. The composition and diversity of the soil microbial communities were analysed using DNA amplicon sequencing of bacterial and fungal markers and the measurement of phospholipid fatty acids. The experimental drought affected the bacterial community much more than the fungal community, decreasing alpha diversity and proportion of total biomass, whereas fungal diversity tended to increase. The experimental drought altered the relative abundances of specific taxa of both bacteria and fungi, and in many cases these effects were modified by the presence of the plant and soil origin. Soils with a history of drought had higher overall bacterial alpha diversity at the end of the experimental drought, presumably because of adaptation of the bacterial community to drought conditions. However, some bacterial taxa (e.g. Chloroflexi) and fungal functional groups (plant pathogens and saprotrophic yeasts) decreased in abundance more in the pre-droughted soils. Our results suggest that soil communities will not necessarily be able to maintain the same functions during more extreme or more frequent future droughts, when functions are influenced by community composition. Drought is likely to continue to affect community composition, even in soils that are acclimated to it, tending to increase the proportion of fungi and reduce the proportion and diversity of bacteria

Tissue type and location within forest together regulate decay trajectories of Abies faxoniana logs at early and mid-decay stage

Deadwood decomposition plays a crucial role in global carbon and nutrient cycles. Factors controlling deadwood decomposition at local scales could also have strong effects at broader scales. We tested how trait variation within stems (i.e. tissue types) and forest habitat heterogeneity (i.e. location within forest) together influence the deadwood decay trajectory and decay rate. We conducted an in situ decomposition experiment of Abies faxoniana logs in an alpine forest on the eastern Qinghai-Tibetan Plateau, decomposing logs from a series of decay classes I-III (on a 5-class scale) for five years on the forest floor in canopy gap, gap edge and under closed canopy (each sized 25 ± 3 × 25 ± 3 m). We found strong differences in density and chemical composition between tissue types at least across decay classes I-III, which revealed the distinct contribution of each tissue type to carbon and nutrient cycling. There were remarkable interactions of tissue types and locations within forest. We found bark always decomposed faster than wood, while heartwood can decompose faster than sapwood in canopy edge and canopy gap. Locations within forest influenced the best fit decay model and decay rate of bark and sapwood in the same way, while it had no corresponding effects for heartwood decay dynamics. The largest difference in T0.25 and T0.4 (time to 25% and 40% mass loss) between locations were 1.52 and 3.21 (bark), 19.41 and 37.61 (wood overall), 31.82 and 60.15 (sapwood), and 12.86 and 22.84 (heartwood), respectively. We also found that pH was significantly negatively related with sapwood and heartwood mass loss, demonstrating that pH can potentially be applied to evaluate sapwood and heartwood mass loss when density correction is difficult to achieve at least at early to mid-decay stages. However, whether pH is a powerful predictor of decomposition trajectory across more species and biomes remains to be tested. We strongly recommend that further model predictions of coarse log decay include radial positions within stem and locations within forest as factors to increase the reliability of carbon budget estimates

Prolonged exposure does not increase soil microbial community compositional response to warming along geothermal gradients

Global change is expected to affect soil microbial communities through their responsiveness to temperature. It has been proposed that prolonged exposure to elevated temperatures may lead to progressively larger effects on soil microbial community composition. However, due to the relatively short-term nature of most warming experiments, this idea has been challenging to evaluate. The present study took the advantage of natural geothermal gradients (from +1°C to +19°C above ambient) in two subarctic grasslands to test the hypothesis that long-term exposure (>50 years) intensifies the effect of warming on microbial community composition compared to short-term exposure (5–7 years). Community profiles from amplicon sequencing of bacterial and fungal rRNA genes did not support this hypothesis: significant changes relative to ambient were observed only starting from the warming intensity of +9°C in the long term and +7°C/+3°C in the short term, for bacteria and fungi, respectively. Our results suggest that microbial communities in high-latitude grasslands will not undergo lasting shifts in community composition under the warming predicted for the coming 100 years (+2.2°C to +8.3°C).This work was supported by Research Foundation–Flanders (FWO) [1293114N to JTW, 12B0716N to SV, 11G1615N to NIWL], Icelandic Research Council [163272-051 to BDS], Climate Change Manipulation Experiments in Terrestrial Ecosystems (ClimMani) COST Action [ES1308], the European Research Council grant ERC-SyG-610028 IMBALANCE-P and the University of Antwerp: University Research Fund (BOF).Peer Reviewe

Filtration artefacts in bacterial community composition can affect the outcome of dissolved organic matter biolability assays

Inland waters are large contributors to global carbon dioxide (CO2) emissions, in part due to the vulnerability of dissolved organic matter (DOM) to microbial decomposition and respiration to CO2 during transport through aquatic systems. To assess the degree of this vulnerability, aquatic DOM is often incubated in standardized biolability assays. These assays isolate the dissolved fraction of aquatic OM by size filtration prior to incubation. We test whether this size selection has an impact on the bacterial community composition and the consequent dynamics of DOM degradation using three different filtration strategies: 0.2 μm (filtered and inoculated), 0.7 μm (generally the most common DOM filter size) and 106 μm (unfiltered). We found that bacterial community composition, based on 16S rRNA amplicon sequencing, was significantly affected by the different filter sizes. At the same time, the filtration strategy also affected the DOM degradation dynamics, including the δ13C signature. However, the dynamics of these two responses were decoupled, suggesting that filtration primarily influences biolability assays through bacterial abundance and the presence of their associated predators. By the end of the 41-day incubations all treatments tended to converge on a common total DOM biolability level, with the 0.7 μm filtered incubations reaching this point the quickest. These results suggest that assays used to assess the total biolability of aquatic DOM should last long enough to remove filtration artefacts in the microbial population. Filtration strategy should also be taken into account when comparing results across biolability assays

Embodied Discourses of Literacy in the Lives of Two Preservice Teachers

This study examines the emerging teacher literacy identities of Ian and A.J., two preservice teachers in a graduate teacher education program in the United States. Using a poststructural feminisms theoretical framework, the study illustrates the embodiment of literacy pedagogy discourses in relation to the literacy courses’ discourse of comprehensive literacy and the literacy biographical discourses of Ian and A.J. The results of this study indicate the need to deconstruct how the discourse of comprehensive literacy limits how we, as literacy teacher educators, position, hear and respond to our preservice teachers and suggests the need for differentiation in our teacher education literacy courses