Distribution of resprouting woody plants and the effect of fire on vegetation types in the Southern Great Plains

The effects of soil, topography, and fire on woody plant distribution and extent has been studied over numerous systems; however, most literature has focused individually on these influencing variables at single sites. In this study, we evaluated the effects of soil texture, slope, aspect, and fire measured across 39 ecological sites and four different locations in Oklahoma, USA, from 2018-2019. We used an information€ theoretic model building approach to develop models describing the effects of these predictor variables on two different estimates of woody plant cover as well as woody plant density across sites. Top models for all three woody plant metrics indicated that both woody plant cover and density were primarily influenced by percent sand, aspect direction, and the number of times burned. Metrics of woody plant cover and density declined in areas with finer soil textures, east-facing aspects, and areas that were burned more frequently across sites. Of these predictor variables, topoedaphic variables appeared overall to have a greater influence than fire. This suggests that managing woody plants with fire is partly limited by underlying soil and topographic conditions. Summary statistics at the site level mostly indicated relationships similar to cross-site analysis among woody plant metrics and predictor variables, however, there were also differences among sites. In addition to examining broad-scale patterns, we also investigated site-level relationships. Specifically, we examined the post-fire effects on woody plant vegetation type at three of the four sites. Our research suggests that these vegetation types of the Southern Great Plains recover quickly from fire and can be burned every 2-3 years to promote heterogeneity, limit the invasion of non-resprouting woody plants, and potentially benefit native wildlife. Following fire, vegetation cover and structure recovered to pre-burn conditions within 2 years post-fire at all three sites. Our research emphasizes the importance of broad-scale and site-level examination of woody plant distribution to better understand the factors influencing woody plant cover and densities to provide insightful management strategies for these landscapes

Quantification of Human Polyomaviruses JC Virus and BK Virus by TaqMan Quantitative PCR and Comparison to Other Water Quality Indicators in Water and Fecal Samples▿

In the United States, total maximum daily load standards for bodies of water that do not meet bacterial water quality standards are set by each state. The presence of human polyomaviruses (HPyVs) can be used as an indicator of human-associated sewage pollution in these waters. We have developed and optimized a TaqMan quantitative PCR (QPCR) assay based on the conserved T antigen to both quantify and simultaneously detect two HPyVs; JC virus and BK virus. The QPCR assay was able to consistently quantify ≥10 gene copies per reaction and is linear over 5 orders of magnitude. HPyVs were consistently detected in human waste samples (57 of 64) and environmental waters with known human fecal contamination (5 of 5) and were not amplified in DNA extracted from 127 animal waste samples from 14 species. HPyV concentrations in sewage decreased 81.2 and 84.2% over 28 days incubation at 25 and 35°C, respectively. HPyVs results were compared to Escherichia coli, fecal coliform, and enterococci concentrations and the presence of three other human-associated microbes: Bacteroidetes, Methanobrevibacter smithii, and adenovirus. HPyVs were the most frequently detected of these in human and contaminated environmental samples and were more human specific than the Bacteroidetes (HF183) or M. smithii. HPyVs and M. smithii more closely mimicked the persistence of adenovirus in sewage than the other microbes. The use of this rapid and quantitative assay in water quality research could help regulatory agencies to identify sources of water pollution for improved remediation of contaminated waters and ultimately protect humans from exposure to pathogens

Presence of Pathogens and Indicator Microbes at a Non-Point Source Subtropical Recreational Marine Beach ▿ †

Swimming in ocean water, including ocean water at beaches not impacted by known point sources of pollution, is an increasing health concern. This study was an initial evaluation of the presence of indicator microbes and pathogens and the association among the indicator microbes, pathogens, and environmental conditions at a subtropical, recreational marine beach in south Florida impacted by non-point sources of pollution. Twelve water and eight sand samples were collected during four sampling events at high or low tide under elevated or reduced solar insolation conditions. The analyses performed included analyses of fecal indicator bacteria (FIB) (fecal coliforms, Escherichia coli, enterococci, and Clostridium perfringens), human-associated microbial source tracking (MST) markers (human polyomaviruses [HPyVs] and Enterococcus faecium esp gene), and pathogens (Vibrio vulnificus, Staphylococcus aureus, enterovirus, norovirus, hepatitis A virus, Cryptosporidium spp., and Giardia spp.). The enterococcus concentrations in water and sand determined by quantitative PCR were greater than the concentrations determined by membrane filtration measurement. The FIB concentrations in water were below the recreational water quality standards for three of the four sampling events, when pathogens and MST markers were also generally undetectable. The FIB levels exceeded regulatory guidelines during one event, and this was accompanied by detection of HPyVs and pathogens, including detection of the autochthonous bacterium V. vulnificus in sand and water, detection of the allochthonous protozoans Giardia spp. in water, and detection of Cryptosporidium spp. in sand samples. The elevated microbial levels were detected at high tide and under low-solar-insolation conditions. Additional sampling should be conducted to further explore the relationships between tidal and solar insolation conditions and between indicator microbes and pathogens in subtropical recreational marine waters impacted by non-point source pollution