Leaf litter mixtures alter microbial community development: Mechanisms for non-additive effects in litter decomposition

To what extent microbial community composition can explain variability in ecosystem processes remains an open question in ecology. Microbial decomposer communities can change during litter decomposition due to biotic interactions and shifting substrate availability. Though relative abundance of decomposers may change due to mixing leaf litter, linking these shifts to the non-additive patterns often recorded in mixed species litter decomposition rates has been elusive, and links community composition to ecosystem function. We extracted phospholipid fatty acids (PLFAs) from single species and mixed species leaf litterbags after 10 and 27 months of decomposition in a mixed conifer forest. Total PLFA concentrations were 70% higher on litter mixtures than single litter types after 10 months, but were only 20% higher after 27 months. Similarly, fungal-to-bacterial ratios differed between mixed and single litter types after 10 months of decomposition, but equalized over time. Microbial community composition, as indicated by principal components analyses, differed due to both litter mixing and stage of litter decomposition. PLFA biomarkers a15∶0 and cy17∶0, which indicate gram-positive and gram-negative bacteria respectively, in particular drove these shifts. Total PLFA correlated significantly with single litter mass loss early in decomposition but not at later stages. We conclude that litter mixing alters microbial community development, which can contribute to synergisms in litter decomposition. These findings advance our understanding of how changing forest biodiversity can alter microbial communities and the ecosystem processes they mediate

Long-term insect herbivory slows soil development in an arid ecosystem

Although herbivores are well known to alter litter inputs and soil nutrient fluxes, their long-term influences on soil development are largely unknown because of the difficulty of detecting and attributing changes in carbon and nutrient pools against large background levels. The early phase of primary succession reduces this signal-to-noise problem, particularly in arid systems where individual plants can form islands of fertility. We used natural variation in tree-resistance to herbivory, and a 15 year herbivore-removal experiment in an Arizona piñon-juniper woodland that was established on cinder soils following a volcanic eruption, to quantify how herbivory shapes the development of soil carbon (C) and nitrogen (N) over 36–54 years (i.e., the ages of the trees used in our study). In this semi-arid ecosystem, trees are widely spaced on the landscape, which allows direct examination of herbivore impacts on the nutrient-poor cinder soils. Although chronic insect herbivory increased annual litterfall N per unit area by 50% in this woodland, it slowed annual tree-level soil C and N accumulation by 111% and 96%, respectively. Despite the reduction in soil C accumulation, short-term litterfall-C inputs and soil C-efflux rates per unit soil surface were not impacted by herbivory. Our results demonstrate that the effects of herbivores on soil C and N fluxes and soil C and N accumulation are not necessarily congruent: herbivores can increase N in litterfall, but over time their impact on plant growth and development can slow soil development. In sum, because herbivores slow tree growth, they slow soil development on the landscape. http://dx.doi.org/10.1890/ES12-00411.

Spatiotemporal characteristics of atrial fibrillation electrograms: a novel marker for arrhythmia stability and termination

Background: Sequentially mapped complex fractionated atrial electrograms (CFAE) and dominant frequency (DF) sites have been targeted during catheter ablation for atrial fibrillation (AF). However, these strategies have yielded variable success and have not been shown to correlate consistently with AF dynamics. Here, we evaluated whether the spatiotemporal stability of CFAE and DF may be a better marker of AF sustenance and termination. Methods: Eighteen sheep with 12 weeks of "one-kidney, one-clip" hypertension underwent open-chest studies. A total of 42 self-terminating (28–100 s) and 6 sustained (>15 min) AF episodes were mapped using a custom epicardial plaque and analyzed in 4-s epochs for CFAE, using the NavX CFE-m algorithm, and DF, using a Fast Fourier Transform. The spatiotemporal stability index (STSI) was calculated using the intraclass correlation coefficient of consecutive AF epochs. Results: A total of 67,733 AF epochs were analyzed. During AF initiation, mean CFE-m and the STSI of CFE-m/DF were similar between sustained and self-terminating episodes, although median DF was higher in sustained AF (p=0.001). During sustained AF, the STSI of CFE-m increased significantly (p=0.02), whereas mean CFE-m (p=0.5), median DF (p=0.07), and the STSI of DF remained unchanged (p=0.5). Prior to AF termination, the STSI of CFE-m was significantly lower (p<0.001), with a physiologically non-significant decrease in median DF (−0.3 Hz, p=0.006) and no significant changes in mean CFE-m (p=0.14) or the STSI of DF (p=0.06). Conclusions: Spatiotemporal stabilization of CFAE favors AF sustenance and its destabilization heralds AF termination. The STSI of CFE-m is more representative of AF dynamics than are the STSI of DF, sequential mean CFE-m, or median DF

The June 2016 Optical and Gamma-Ray Outburst and Optical Micro-Variability of the Blazar 3C454.3

The quasar 3C454.3 underwent a uniquely-structured multi-frequency outburst in June 2016. The blazar was observed in the optical $R$ band by several ground-based telescopes in photometric and polarimetric modes, at $\gamma$-ray frequencies by the \emph{Fermi}\ Large Area Telescope, and at 43 GHz with the Very Long Baseline Array. The maximum flux density was observed on 2016 June 24 at both optical and $\gamma$-ray frequencies, reaching $S^\mathrm{max}_\mathrm{opt}=18.91\pm0.08$ mJy and $S_\gamma^\mathrm{max} =22.20\pm0.18\times10^{-6}$ ph cm$^{-2}$ s$^{-1}$, respectively. The June 2016 outburst possessed a precipitous decay at both $\gamma$-ray and optical frequencies, with the source decreasing in flux density by a factor of 4 over a 24-hour period in $R$ band. Intraday variability was observed throughout the outburst, with flux density changes between 1 and 5 mJy over the course of a night. The precipitous decay featured statistically significant quasi-periodic micro-variability oscillations with an amplitude of $\sim 2$-$3\%$ about the mean trend and a characteristic period of 36 minutes. The optical degree of polarization jumped from $\sim3\%$ to nearly 20\% during the outburst, while the position angle varied by \sim120\degr. A knot was ejected from the 43 GHz core on 2016 Feb 25, moving at an apparent speed $v_\mathrm{app}=20.3c\pm0.8c$. From the observed minimum timescale of variability $\tau_\mathrm{opt}^\mathrm{min}\approx2$ hr and derived Doppler factor $\delta=22.6$, we find a size of the emission region $r\lesssim2.6\times10^{15}$ cm. If the quasi-periodic micro-variability oscillations are caused by periodic variations of the Doppler factor of emission from a turbulent vortex, we derive a rotational speed of the vortex $\sim0.2c$.Comment: 19 pages, 13 figures, 3 tables, accepted to the Astrophysical Journal 2019 March

Attitudes towards community gambling venues and support for regulatory reform: An online panel study of residents in New South Wales, Australia

Background: Harmful gambling has been identified as an important public health issue that affects individuals, families and the broader community. One gambling product, electronic gambling machines (EGMs), has been associated with significant gambling harm in Australia. There has been limited research that has explored community perceptions of EGMs and attitudes towards reform. This study, conducted in NSW, Australia, aimed to explore community use of EGM venues (clubs and hotels containing EGMs), attitudes towards EGMs and whether the use of these venues influenced attitudes towards EGM reform. Methods: An online survey was conducted with 500 adults aged 16 years and over, representative of the population for age and gender. Discrete choice and open-ended questions were used to gather data on gambling behaviours, use of and attitudes towards EGMs and EGM venues and support for gambling harm reduction measures. Results: Three quarters of participants had visited an EGM venue in the previous year. Participants who had attended such venues were significantly more likely to use EGMs at least once per month. Participants attended EGM venues for a range of reasons including use of non-gambling facilities such as restaurants, the social aspects of the venue and ease of access to the venue. Some participants also attended EGM venues specifically for the gambling facilities. Most participants identified some negative impacts of EGMs for local communities and were supportive of measures to reduce the number of EGMs and prevent children's exposure to EGMs in such venues. Conclusions: This study shows a high level of support for EGM reform amongst both individuals who attend EGM venues and also those who do not. There is potential for government to further regulate EGMs and the environments where they are located

Applying polygenic risk scores to postpartum depression

The etiology of major depressive disorder (MDD) is likely to be heterogeneous, but postpartum depression (PPD) is hypothesized to represent a more homogenous subset of MDD. We use genome-wide SNP data to explore this hypothesis

Attitudes towards community gambling venues and support for regulatory reform: an online panel study of residents in New South Wales, Australia

BACKGROUND: Harmful gambling has been identified as an important public health issue that affects individuals, families and the broader community. One gambling product, electronic gambling machines (EGMs), has been associated with significant gambling harm in Australia. There has been limited research that has explored community perceptions of EGMs and attitudes towards reform. This&nbsp;study, conducted in NSW, Australia, aimed to explore community use of EGM venues (clubs and hotels containing EGMs), attitudes towards EGMs and whether the use of these venues influenced attitudes towards EGM reform. METHODS: An online survey was conducted with 500 adults aged 16&nbsp;years and over, representative of the population for age and gender. Discrete choice and open-ended questions were used to gather data on gambling behaviours, use of and attitudes towards EGMs and EGM venues and support for gambling harm reduction measures. RESULTS: Three quarters of participants had visited an EGM venue in the previous year. Participants who had attended such venues were significantly more likely to use EGMs at least once per month. Participants attended EGM venues for a range of reasons including use of non-gambling facilities such as restaurants, the social aspects of the venue and ease of access to the venue. Some participants also attended EGM venues specifically for the gambling facilities. Most participants identified some negative impacts of EGMs for local communities and were supportive of measures to reduce the number of EGMs and prevent children\u27s exposure to EGMs in such venues. CONCLUSIONS: This study shows a high level of support for EGM reform amongst both individuals who attend EGM venues and also those who do not. There is potential for government to further regulate EGMs and the environments where they are located