Microbial community structure as influenced by season and stand age in a Douglas-fir (Pseudotsuga menziesii) ecosystem

Forest harvest can have significant impacts on forest ecosystems that may influence the capacity of soils to sequester carbon (C). The microbial community controls decomposition, which is a critical process in partitioning litter- and root-C between CO₂ and storage in semi-permanent soil-C pools. The objectives of this study were to determine the effect of clear-cutting and stand age on: 1) temporal dynamics of soil microbial community (SMC) structure and physiological status; and 2) shifts among microbial functional groups in taking up ¹³C-labeled plant materials during decomposition. The experiment was conducted in Douglas-fir ecosystems within the Gifford Pinchot National Forest, Washington. We chose stands of three different ages: old-growth where trees are between 300 and 500 years old; an 8-year old stand; and a 25-year old stand. Phospholipid fatty acid (PLFA) profiling and ¹³C-PLFA labeling techniques along with the ratio of saturated to monounsaturated PLFAs and the ratios of cyclopropyl PLFAs to their monoenoic precursors as microbial physiological stress markers were utilized. Microbial PLFA profiles showed that SMC structure and physiological status was most affected by season and secondarily by time since clear-cutting. Total microbial biomass and bacterial and fungal biomass were significantly reduced in CC8 but not in CC25 sites relative to old-growth sites. Total microbial biomass concentration was lowest and the stress indicators were highest in August, which corresponded to low soil moisture and high temperatures. The relative amount of ¹³C incorporated into PLFAs was also influenced by stand age and ¹³C source (¹³C-labeled litter vs. ¹³C-labeled root material). A significantly greater amount of ¹³C was incorporated in CC8 samples compared to OG1 samples in five out of the seven sample dates. Additionally, a significantly greater proportion of ¹³C was incorporated into soil samples containing the ¹³C-labeled litter material relative to samples containing ¹³C-labeled root material in four out of the seven dates. In general, 18:lω9 and 18:2ω6,9 (common fungal biomarkers) had the greatest amount of ¹³C incorporation throughout the study period in both clear-cut and old-growth sites, indicating the important role of fungi in the decomposition of litter and root material and translocation of C within soil layers

Microbiology of wind-eroded sediments: current knowledge and future research directions

Wind erosion is a threat to the sustainability and productivity of soils that takes place at local, regional, and global scales. Current estimates of the cost of wind erosion have not included the costs associated with the loss of soil biodiversity and reduced ecosystem functions. Microorganisms carried in dust are responsible for numerous critical ecosystem processes including biogeochemical cycling of nutrients, carbon storage, soil aggregation, and transformation of toxic compounds in the source soil. Currently, much of the information on microbial transport in dust has been collected at continental scales, with no comprehensive review regarding the microbial communities, particularly those associated with agricultural systems, redistributed by wind erosion processes at smaller scales including regional or field scales. Agricultural systems can contribute significantly to atmospheric dust loading and loss or redistribution of soil microorganisms are impacted in three interactive ways: (1) differential loss of certain microbial taxa depending on particle size and wind conditions, (2) through the destabilization of soil aggregates and reduction of available surfaces, and (3) through the reduction of organic matter and substrates for the remaining community. The purpose of this review is to provide an overview of dust sampling technologies, methods for microbial extraction from dust, and how abiotic, environmental, and management factors influence the dust microbiome within and among agroecosystems. The review also offers a perspective on important potential future research avenues with a focus on agroecosystems and the inclusion of the fungal component

What is the relationship between photospheric flow fields and solar flares?

We estimated photospheric velocities by separately applying the Fourier Local Correlation Tracking (FLCT) and Differential Affine Velocity Estimator (DAVE) methods to 2708 co-registered pairs of SOHO/MDI magnetograms, with nominal 96-minute cadence and ~2" pixels, from 46 active regions (ARs) from 1996-1998 over the time interval t45 when each AR was within 45^o of disk center. For each magnetogram pair, we computed the average estimated radial magnetic field, B; and each tracking method produced an independently estimated flow field, u. We then quantitatively characterized these magnetic and flow fields by computing several extensive and intensive properties of each; extensive properties scale with AR size, while intensive properties do not depend directly on AR size. Intensive flow properties included moments of speeds, horizontal divergences, and radial curls; extensive flow properties included sums of these properties over each AR, and a crude proxy for the ideal Poynting flux, the total |u| B^2. Several magnetic quantities were also computed, including: total unsigned flux; a measure of the amount of unsigned flux near strong-field polarity inversion lines, R; and the total B^2. Next, using correlation and discriminant analysis, we investigated the associations between these properties and flares from the GOES flare catalog, when averaged over both t45 and shorter time windows, of 6 and 24 hours. We found R and total |u| B^2 to be most strongly associated with flares; no intensive flow properties were strongly associated with flares.Comment: 57 pages, 13 figures; revised content; added URL to manuscript with higher-quality image

Is there a reduction of congenital abnormalities in the offspring of diabetic pregnant women after folic acid supplementation? A population-based case-control study

The objective of the present study was to estimate the preventive effect of folic acid for structural birth defects (i.e. congenital abnormalities [CAs]) in the offspring of pregnant women with diabetes mellitus type 1 (DM-1). The occurrence of medically recorded DM-1 in pregnant women who had malformed fetuses/newborns (cases) and delivered healthy babies (controls) with or without folic acid supplementation was compared in the population-based Hungarian Case-Control Surveillance System of Congenital Abnormalities. The case group included 22,843 offspring, and there were 79 (0.35%) pregnant women with DM-1, while the control group comprised of 38,151 newborns, and 88 (0.23%) had mothers with DM-1. Case mothers with DM-1 associated with a higher risk of total rate of CAs in their offspring (OR with 95% CI: 1.5, 1.1-2.0) compared to the total rate of CAs in the offspring of non-diabetic case mothers. This higher risk can be explained by four specific types/groups of CAs: isolated renal a/dysgenesis; obstructive CA of the urinary tract; cardiovascular CAs; and multiple CAs, namely caudal dysplasia sequence. However, there was no higher rate of total CAs in the children of pregnant women with DM-1 after folic acid supplementation; in addition, neural-tube defect and renal a/dysgenesis did not occur. However, this benefit cannot be explained by the CA reduction effect of folic acid during the critical period of major CAs. In conclusion, there was a certain reduction in maternal teratogenic effect of DM-1 after folic acid supplementation during pregnancy, but the explanation of this effect requires further study

A Systematic Comparison of Antimicrobial Wound Dressings using a Planktonic Cell and an Immobilised Cell Model. Kamran

Aim: The aim of the study was to evaluate the ability of in-vitro planktonic and immobilised cell models for determining the antimicrobial efficacy of common antimicrobial wound dressings. Methods and Results: Five strains of A.baumannii , P.aeruginosa and S. aureus (MRSA) were tested against four antimicrobial wound dressings containing silver, honey or PHMB, using both a planktonic and immobilised cell model. Across all species and models used, the NSCD demonstrated the best antimicrobial activity being as good if not better than all the other dressings. The planktonic cell model was less effective at differentiating the dressings on antimicrobial performance as the immobilised cell model indicating that a diffusion barrier had a significant impact on the performance of some dressings. In the presence of the diffusion barrier antimicrobial impact of the Honey and PHMB dressings was significantly reduced particularly in the case of A. baumannii. Activity was at least an order of magnitude lower in the immobilised cell model vs. the planktonic cell model. Conclusions: The use of a planktonic cell model within standard tests may overestimate the efficacy of honey and PHMB. The use of an immobilised cell model provides a more demanding test for antimicrobial dressings allowing dressing to dressing and pathogen to pathogen differences to be more clearly quantified. Significance and Impact of study: The introduction of planktonic and immobilised cell models as part of testing regimens for wound dressings will provide a more thorough understanding of their antimicrobial and antibiofilm properties

GHG emission under different cropping systems in some Histosols of Malaysia

Oil palm is the fastest expanding equatorial crop, and is one of the biggest threats to carbon-rich tropical peatlands in Malaysia. Smallholder plantations cover a vast area of peatlands in Peninsular Malaysia and follow varied cropping systems. Here we analyse the impacts of specific crops and the effects of proximity to such crops, upon GHG emissions from the soil, and the soil microbial community phenotype. We found that only mature oil palm plants in 1st generation oil palm mono-cropping potentially had significant autotrophic contributions to total CO2 emissions with 33.5% increase in locations closer to mature oil palm stems. The sampling locations closer to younger oil palms and other crops did not significantly increase total CO2 emissions. CH4 emissions were significantly greater for sampling locations near plants with adventitious root system such as yam and pineapple crops. However CH4 emissions were very low in comparison to CO2 emissions, and their contribution to carbon loss was limited in these sites. Surface peat microbial community structure was unaffected by proximity to different crops within each cropping system, possibly due to a lack of influence of rhizosphere in the surface peat layers (0–5 cm). The results suggest that most of the total CO2 emissions from these agro-ecosystems contribute to C loss due to microbial decomposition of the peat soil, unlike greater autotrophic contributions to total emissions in forested peatlands reported in other studies. Hence without appropriate above-ground vegetation or hydrology conducive to peat formation, ancient carbon stored in these peatlands is gradually lost into the atmosphere via greater heterotrophic respiration under agricultural management on such peat-based ecosystems

Anaerobic Decomposition of Switchgrass by Tropical Soil-Derived Feedstock-Adapted Consortia

Tropical forest soils decompose litter rapidly with frequent episodes of anoxic conditions, making it likely that bacteria using alternate terminal electron acceptors (TEAs) play a large role in decomposition. This makes these soils useful templates for improving biofuel production. To investigate how TEAs affect decomposition, we cultivated feedstock-adapted consortia (FACs) derived from two tropical forest soils collected from the ends of a rainfall gradient: organic matter-rich tropical cloud forest (CF) soils, which experience sustained low redox, and iron-rich tropical rain forest (RF) soils, which experience rapidly fluctuating redox. Communities were anaerobically passed through three transfers of 10 weeks each with switchgrass as a sole carbon (C) source; FACs were then amended with nitrate, sulfate, or iron oxide. C mineralization and cellulase activities were higher in CF-FACs than in RF-FACs. Pyrosequencing of the small-subunit rRNA revealed members of the Firmicutes, Bacteroidetes, and Alphaproteobacteria as dominant. RF- and CF-FAC communities were not different in microbial diversity or biomass. The RF-FACs, derived from fluctuating redox soils, were the most responsive to the addition of TEAs, while the CF-FACs were overall more efficient and productive, both on a per-gram switchgrass and a per-cell biomass basis. These results suggest that decomposing microbial communities in fluctuating redox environments are adapted to the presence of a diversity of TEAs and ready to take advantage of them. More importantly, these data highlight the role of local environmental conditions in shaping microbial community function that may be separate from phylogenetic structure

Soil biota in boreal urban greenspace : Responses to plant type and age

Plant functional type influences the abundance and distribution of soil biota. With time, as root systems develop, such effects become more apparent. The relationship of plant type and time with the structure and abundance of soil microbial and invertebrate communities has been widely investigated in a variety of systems. However, much less is known about long-term soil community dynamics within the context of urban environments. In this study, we investigated how soil microbes, nematodes and earthworms respond to different plant functional types (lawns only and lawns with deciduous or evergreen trees) and park age in 41 urban parks in southern Finland. As non-urban controls we included deciduous and evergreen trees in 5 forest sites. We expected that microbial biomass and the relative abundance of fungi over bacteria would increase with time. We also expected major differences in soil microbial and nematode communities depending on vegetation: we hypothesized that i) the presence of trees, and evergreens in particular, would support a greater abundance of fungi and fungal-feeding nematodes over bacteria and bacterial-feeding nematodes and ii) the fungi to bacteria ratio would be lowest in lawns, with deciduous trees showing intermediate values. In contrast to our predictions, we showed that old deciduous trees, rather than evergreens, supported the highest fungal abundances and fungal-feeding nematodes in the soil. Consistent with our predictions, microbial biomass in urban park soils tended to increase with time, whereas - in contrast to our hypotheses - fungal-feeding nematode abundance declined. Even in the oldest parks included in the current study, microbial biomass estimates never approximated those in the minimally managed natural forests, where biomass estimates were three times higher. Anecic earthworm abundance also increased with time in urban parks, whereas abundances of fungal-feeding, plant-feeding and omnivorous nematodes, as well as those of epigeic and endogeic earthworms remained constant with time and without any distinct differences between urban parks and the control forests. Our findings highlight that although urban park soils harbor diverse soil communities and considerable microbial biomass, they are distinct from adjacent natural sites in community composition and biomass.Peer reviewe