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One critical tool for creating an environmentally literate citizenry is to reach students other than those in environmental-related majors in the form of the university-level large introductory environmental studies course. In this study, we relate student academic background to initial and final environmental awareness results. We found that students from a wide range of backgrounds begin with similar motivation for taking the class and uniformly low environmental knowledge. Our results indicate that a low-credit, engaging introductory environmental studies class can strongly impact student awareness independent of diverse learner academic backgrounds. For example, results suggest that students taking the course primarily to meet science breadth requirements and students with a strong previous science background had equivalent initial awareness and course outcomes. The lack of a correlation with background suggests that students are not learning about environmental studies in other classes and reinforces the importance of investing in nonmajors-focused environmental education. Additionally, our findings support the importance of affective learning gains, such as attitude changes, which we term "learning to care".

A proliferation of data gathered to predict a critically important, urgent and social-policy related question often leads to debate and divergent model results. This classic feature of complex systems is currently being evidenced in assessing a potentially serious feedback response of soil respiration with increased temperatures due to global climate change. Here we apply soft systems modelling (SSM) for a detailed analysis of the 'soft' aspects of the topic. Supported by a literature review, we conclude that that varied perspectives on the system's dynamics and its web of controlling factors have led to seemingly conflicting results. We present a simplified hierarchy organizing the comprehensive universe of interacting controls across scales. This model is implemented as a relational database, including relationships between factors such as nesting and feedbacks. We conclude that although this model is currently limited to pairwise interactions, it provides a useful tool to assess potential interactions and factors of interest. Copyright © 2009 John Wiley & Sons, Ltd. Keywords soft systems modelling; complexity; global climate change; modelling; soil carbon, INTRODUCTION With many current environmental challenges, a web of confounding factors acting at different scales complicates the coherent synthesis of experimental results. The relationship between temperature and soil carbon decomposition [...]

Microbial communities (microbiomes) are associated with almost all metazoans, including the honey bee Apis mellifera. Honey bees are social insects, maintaining complex hive systems composed of a variety of integral components including bees, comb, propolis, honey, and stored pollen. Given that the different components within hives can be physically separated and are nutritionally variable, we hypothesize that unique microbial communities may occur within the different microenvironments of honey bee colonies. To explore this hypothesis and to provide further insights into the microbiome of honey bees, we use a hybrid of fatty acid methyl ester (FAME) and phospholipid-derived fatty acid (PLFA) analysis to produce broad, lipid-based microbial community profiles of stored pollen, adults, pupae, honey, empty comb, and propolis for 11 honey bee hives. Averaging component lipid profiles by hive, we show that, in decreasing order, lipid markers representing fungi, Gram-negative bacteria, and Gram-positive bacteria have the highest relative abundances within honey bee colonies. Our lipid profiles reveal the presence of viable microbial communities in each of the six hive components sampled, with overall microbial community richness varying from lowest to highest in honey, comb, pupae, pollen, adults and propolis, respectively. Finally, microbial community lipid profiles were more similar when compared by component than by hive, location, or sampling year. Specifically, we found that individual hive components typically exhibited several dominant lipids and that these dominant lipids differ between components. Principal component and two-way clustering analyses both support significant grouping of lipids by hive component. Our findings indicate that in addition to the microbial communities present in individual workers, honey bee hives have resident microbial communities associated with different colony components. [ABSTRACT FROM AUTHOR]

How diversity influences the stability of a community function is a major question in ecology. However, only limited empirical investigations of the diversity–stability relationship in soil microbial communities have been undertaken, despite the fundamental role of microbial communities in driving carbon and nutrient cycling in terrestrial ecosystems. In this study, we conducted a microcosm experiment to investigate the relationship between microbial diversity and stability of soil decomposition activities against changes in decomposition substrate quality by manipulating microbial community using selective biocides. We found that soil respiration rates and degradation enzyme activities by a coexisting fungal and bacterial community (a taxonomically diverse community) are more stable against changes in substrate quality (plant leaf materials) than those of a fungi-dominated or a bacteria-dominated community (less diverse community). Flexible changes in the microbial community composition and/or physiological state in the coexisting community against changes in substrate quality, as inferred by the soil lipid profile, may be the mechanism underlying this positive diversity–stability relationship. Our experiment demonstrated that the previously found positive diversity–stability relationship could also be valid in the soil microbial community. Our results also imply that the functional/taxonomic diversity and community ecology of soil microbes should be incorporated into the context of climate–ecosystem feedbacks. Changes in substrate quality, which could be induced by climate change, have impacts on decomposition process and carbon dioxide emission from soils, but such impacts may be attenuated by the functional diversity of soil microbial communities. [ABSTRACT FROM AUTHOR]

Abstract: Studies assessing shifts in soil nutrient cycling with warming benefit from microbial data collection with clear ecological hypotheses. However, the fact that many organisms alter their lipids to adjust to temperature complicates interpretation of the widely-used method of phospholipid fatty acid (PLFA) analysis. Changes in PLFA profiles may reflect shifts in community composition (i.e. relative abundance of microbial groups) or physiological change (i.e. the same groups after membrane optimization) or both. The various approaches presently used to interpret results from warming studies expose a need for greater conceptual clarity. We compile the various data metrics commonly used for PLFA and discuss their interpretations in the context of temperature-based studies. We propose that certain lipid ratios are likely to at least partially reflect decreased unsaturation and other warming-induced physiological shifts. A change in community composition may underlie warming results for both whole-community ordination and certain indicator lipids, provided that the effect of lipids commonly re-synthesized to maintain membrane fluidity are considered. Overall, conclusions in warming studies would be strengthened by explicit consideration of temperature-dependent lipid effects in data analysis. Further research is needed toward substantiating the interpretation of PLFA-based temperature response data as indicating community compositional or physiological change. [Copyright &y& Elsevier]

Stand-replacing fires influence soil nitrogen availability and microbial community composition, which may in turn mediate post-fire successional dynamics and nutrient cycling. However, fires create patchiness at both local and landscape scales and do not result in consistent patterns of ecological dynamics. The objectives of this study were to (1) quantify the spatial structure of microbial communities in forest stands recently affected by stand-replacing fire and (2) determine whether microbial variables aid predictions of in situ net nitrogen mineralization rates in recently burned stands. The study was conducted in lodgepole pine (Pinus contorta var. latifolia) and Engelmann spruce/subalpine fir (Picea engelmannii/Abies lasiocarpa) forest stands that burned during summer 2000 in Greater Yellowstone (Wyoming, USA). Using a fully probabilistic spatial process model and Bayesian kriging, the spatial structure of microbial lipid abundance and fungi-to-bacteria ratios were found to be spatially structured within plots two years following fire (for most plots, autocorrelation range varied from 1.5 to 10.5 m). Congruence of spatial patterns among microbial variables, in situ net N mineralization, and cover variables was evident. Stepwise regression resulted in significant models of in situ net N mineralization and included variables describing fungal and bacterial abundance, although explained variance was low (R2<0.29). Unraveling complex spatial patterns of nutrient cycling and the biotic factors that regulate it remains challenging but is critical for explaining post-fire ecosystem function, especially in Greater Yellowstone, which is projected to experience increased fire frequencies by mid 21st Century. [ABSTRACT FROM AUTHOR]

Abstract: Management-intensive rotational grazing has been shown to stimulate net primary production in subhumid pastures compared to extensive grazing strategies. The degree to which this represents a direct effect on plant developmental stage and community composition, and/or indirect effects of grazing on microbial community structure and nutrient feedback to production is an open question. To better understand whether the effects of pasture management on microbial communities led to indirect nutrient feedbacks, we analyzed microbial lipids and environmental and physical factors of surface soils under four pasture management treatments – management-intensive rotational grazing, continuous grazing, harvesting for hay, and an unmanaged control. Principal component analysis indicated microbial community structure under our two grazed treatments was different than that of ungrazed treatments. While there was no effect of treatments on total microbial biomass, guild comparisons revealed lower fungal-to-bacterial ratios, lower arbuscular mycorrhizal fungi concentrations, and higher actinomycete biomarkers in soils under grazing, irrespective of grazing management treatments. Gram-positive and anaerobic bacteria biomarker abundance was greater in treatments that included grazing and no management when compared to the treatment where biomass was harvested mechanically. There was no evidence of treatment effects on either Gram-negative bacteria or saprotrophic fungi. Regression tree analysis identified litter quality as the main correlate of differences in the microbial community between grazed and ungrazed treatments. Lower root C:N predicted lower F:B and biomarkers of the bacterial guilds Gm+ and actinomycetes, which were dominant in the grazing treatments, while higher root C:N predicted higher F:B and the guild biomarkers of AMF, which dominated in the ungrazed treatments. These results indicate that greater forage production observed in humid and subhumid regions under management-intensive rotational grazing likely stems from the direct effects on plant developmental stage and plant community composition rather than microbial mediated nutrient feedbacks from altered quantity and quality of plant litter. If the potential for a more favorable C balance in subhumid pastures is realized, greater biomass production and therefore greater litter inputs as a result of the direct effects of management-intensive rotational grazing on plant communities is the most likely mechanism. [Copyright &y& Elsevier]

We used microbial lipid analysis to analyze microbial biomass and community structure during 6 years of experimental treatment at the Jasper Ridge Global Change Experiment ( JRGCE), a long-term multi-factor global change experiment in a California annual grassland. The microbial community fingerprint and specific biomarkers varied substantially from year to year, in both control and experimental treatment plots. Possible drivers of the variability included plant growth, soil moisture, and ambient temperature. Surprisingly, background variation in the microbial community was of a larger magnitude than even very significant treatment effects, and this variation appeared to constrain responses to treatment. Microbial communities were mostly not responsive or not consistently responsive to the experimental treatments. Both arbuscular mycorrhizal fungi biomarker abundance (16 : 1 ω5c) and the fungal to bacterial ratio were lower under nitrogen addition in most years. Bacterial lipid biomarker abundances (15 : 0 iso and 16 : 1 ω7c) were higher under nitrogen addition in 2002, the year of largest microbial biomass, suggesting that bacteria could respond more to nitrogen addition in years of better growth conditions. Nitrogen addition and warming led to an interactive effect on the Gram-positive bacterial biomarker and the fungal to bacterial ratio. These patterns indicate that in California grassland ecosystems, microbial communities may not respond substantially to future changes in climate and that nitrogen deposition may be a determinant of the soil response to global change. Further, year-to-year variation in microbial growth or community composition may be important determinants of ecosystem response to global change. [ABSTRACT FROM AUTHOR]

Abstract: Identifying the transformation of amino sugars in soils is essential in understanding microbial contribution to soil organic matter turnover and sequestration. Using a recently developed method, combining gas chromatograph/mass spectrometry (GC/MS) with laboratory incubation of substrates containing 13C or 15N isotopes, we were able to trace isotopic changes in amino sugar compounds. This allows us to quantitatively evaluate C or N enrichment in amino sugars during transformation in soils using the fragment (F) abundance ratio of m/z F + n to F (n is original skeleton atom number in each fragment). However, there is still lack of detail structural and substitutional information for each ion fragment. In order to improve the interpretation and increase our ability to study amino sugar turnover, we grew labeled amino sugars in lab-cultured organisms. We spectrometrically investigated the ion structures and original skeleton C number (mass shift n) in major ion fragments based on applying multiple representative isotope labels. Our results categorically confirm that previously made assumptions were correct regarding the substitutional number “n” of the glucosamine (). Our study also added valuable structural information for aldononitrile acetate derivatized glucosamine and muramic acid upon electron impact ionization in MS. [Copyright &y& Elsevier]

Background: Leaf-cutter ants use fresh plant material to grow a mutualistic fungus that serves as the ants' primary food source. Within fungus gardens, various plant compounds are metabolized and transformed into nutrients suitable for ant consumption. This symbiotic association produces a large amount of refuse consisting primarily of partly degraded plant material. A leaf-cutter ant colony is thus divided into two spatially and chemically distinct environments that together represent a plant biomass degradation gradient. Little is known about the microbial community structure in gardens and dumps or variation between lab and field colonies. Methodology/Principal Findings: Using microbial membrane lipid analysis and a variety of community metrics, we assessed and compared the microbiota of fungus gardens and refuse dumps from both laboratory-maintained and fieldcollected colonies. We found that gardens contained a diverse and consistent community of microbes, dominated by Gramnegative bacteria, particularly γ-Proteobacteria and Bacteroidetes. These findings were consistent across lab and field gardens, as well as host ant taxa. In contrast, dumps were enriched for Gram-positive and anaerobic bacteria. Broad-scale clustering analyses revealed that community relatedness between samples reflected system component (gardens/dumps) rather than colony source (lab/field). At finer scales samples clustered according to colony source. Conclusions/Significance: Here we report the first comparative analysis of the microbiota from leaf-cutter ant colonies. Our work reveals the presence of two distinct communities: one in the fungus garden and the other in the refuse dump. Though we find some effect of colony source on community structure, our data indicate the presence of consistently associated microbes within gardens and dumps. Substrate composition and system component appear to be the most important factor in structuring the microbial communities. These results thus suggest that resident communities are shaped by the plant degradation gradient created by ant behavior, specifically their fungiculture and waste management. [ABSTRACT FROM AUTHOR]

Understanding the temperature sensitivity of soil respiration is critical for predicting the response of ecosystems to climate change, yet the microbial communities responsible are rarely considered explicitly in studies or models. In this study, we assessed total microbial community composition, quantified bacterial respiration temperature response, and investigated the temperature dependence of bacterial carbon substrate utilization in tropical, temperate, and taiga soils (from Puerto Rico, California, and Alaska). Microbial community composition was characterized using phospholipid fatty acid analysis. Bacterial community respiration on a standardized set of substrates was ascertained using the BiOLOG™ substrate utilization assay incubated at four temperatures: 4, 12, 28, and 40 °C. First, we found that microbial communities from the three latitudes were compositionally distinct and that the bacterial component of the three communities had markedly different respiration temperature–response curves corresponding with their experienced temperature regimes. We use these data to highlight limitations of widely used temperature–response equations and investigate temperature-dependent patterns of substrate utilization. We found that temperature response, in terms of both respiration rates and substrate use, varied for these bacterial communities independent of substrate quality or quantity interactions such as labile depletion. In contrast to the common assumption of heterotrophic microbial ubiquity, we found that bacterial community differences from these diverse systems appeared to determine both rates of respiration and patterns of carbon substrate usage. We suggest that microbial community composition-specific responses to changing climate may be important in predicting the long-term role of ecosystems in atmospheric CO2 dynamics. [ABSTRACT FROM AUTHOR]

The muramic acid (MurA) assay is a powerful tool for the detection and quantification of bacteria with no need to enrich samples by culturing. However, the analysis of MurA in mixed biological and environmental matrices is potentially more complex than analysis in isolated bacterial cells. In this study, we employed one commonly used procedure for extraction of MurA from environmental samples and found that the presence of streptomycin interfered with the determination of MurA by creating chemical species that coeluted with the aldononitrile derivative of MurA prepared in this method. On a molar basis, streptomycin yields a signal that is approximately 0.67 times that of MurA. Mass spectrometry analysis confirmed that the interference from hydrolyzed streptomycin is not actually by MurA, but rather is likely to be N-methyl glucosamine. Because streptomycin is widely applied for selective growth of eukaryotes both in situ and in vitro, our findings may have implications for the significance of results from MurA assays. We conclude that MurA remains an effectual bacterial biomarker due to its unique bacterial origin, but care must be applied in interpreting results from the assay when performed in the presence of streptomycin. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen (N) limits productivity in many coniferous forests of the western US, but the influence of post-fire structure on N cycling rates in early successional stands is not well understood. We asked if the heterogeneity created by downed wood and regenerating pine saplings affected N mineralization and microbial community composition in 15-yr old lodgepole pine (Pinus contorta var. latifolia) stands established after the 1988 fires in Yellowstone National Park (Wyoming, USA). In three 0.25-ha plots, we measured annual in situ net N mineralization in mineral soil using resin cores (n =100 per plot) under pine saplings, downed wood (legacy logs that survived the fire, and fire-killed trees that had fallen and were contacting or elevated above the ground), and in bare mineral soil. Annual in situ net N mineralization and net nitrification rates were both greater in bare mineral soil (8.4±0.6 and 3.6±0.3mgNkgsoil −1 yr−1, respectively) than under pine saplings, contact logs, or elevated logs (ca. 3.9±0.5 and 0.8±0.1mgNkgsoil −1 yr−1, respectively). Net nitrification was positively related to net N mineralization under all treatments except for elevated logs. In laboratory incubations using 15N pool dilution, NH4 + consumption exceeded gross production by a factor of two in all treatments, but consumption and gross production were similar among treatments. Contrary to our initial hypothesis, microbial community composition also did not vary among treatments. Thus, two- to three-fold differences in in situ net N mineralization rates occurred despite the similarity in microbial communities and laboratory measures of gross production and consumption of NH4 + among treatments. These results suggest the importance of microclimate on in situ annual soil N transformations, and differences among sites suggest that broader scale landscape conditions may also be important. [Copyright &y& Elsevier]

Abstract: Several recent studies have indicated that an enriched atmosphere of carbon dioxide (CO2) could exacerbate the intensity of plant invasions within natural ecosystems, but little is known of how rising CO2 impacts the belowground characteristics of these invaded systems. In this study, we examined the effects of elevated CO2 and nitrogen (N) inputs on plant and soil microbial community characteristics of plant communities invaded by reed canary grass, Phalaris arundinacea L. We grew the invasive grass under two levels of invasion: the invader was either dominant (high invasion) at >90% plant cover or sub-dominant (low invasion) at <50% plant cover. Experimental wetland communities were grown for four months in greenhouses that received either 600 or 365μll−1 (ambient) CO2. Within each of three replicate rooms per CO2 treatment, the plant communities were grown under high (30mgl−1) or low (5mgl−1) N. In contrast to what is often predicted under N limitation, we found that elevated CO2 increased native graminoid biomass at low N, but not at high N. The aboveground biomass of reed canary grass did not respond to elevated CO2, despite it being a fast-growing C3 species. Although elevated CO2 had no impact on the plant biomass of heavily invaded communities, the relative abundance of several soil microbial indicators increased. In contrast, the moderately invaded plant communities displayed increased total root biomass under elevated CO2, while little impact occurred on the relative abundance of soil microbial indicators. Principal components analysis indicated that overall soil microbial community structure was distinct by CO2 level for the varying N and invasion treatments. This study demonstrates that even when elevated CO2 does not have visible effects on aboveground plant biomass, it can have large impacts belowground. [Copyright &y& Elsevier]

Microbial contribution to carbon and nitrogen cycling in forest soils is important, and may depend on tree species. The amount of amino sugars and their ratios can serve as reliable indicators for bacterial and fungal contribution. We compare forest floor microbial residues (amino sugars) beneath three canopy-tree species (Sugar Maple (SM), Acer saccharum Marsh; Basswood (BA), Tilia americana L.; Eastern Hemlock, Tsuga canadensis L.) replicated in five plots in an upper Michigan old-growth forest. We hypothesized that because individual tree species develop a unique microbial community over time, they will accumulate microbial residues to different degrees. In this study at three tree species sites, the absolute amount of fungal residue (glucosamine (GluN)) was relatively constant, while absolute quantities of bacterial residues (galactosamine (GalN) and muramic acid (MurA)) were least in the Hemlock site. Amino sugar ratios revealed that microbial residues were compositionally distinct in the three sites. The lower ratios of GluN to GaIN and GluN to MurA in BA and SM sites relative to Hemlock site indicate the lower net accumulations of GalN and MurA in Hemlock site. In terms of microbial contribution to carbon and nitrogen cycle in forest soils, we suggest that caution may be needed when using amino sugars as a tool, especially for nitrogen pool assessment, as the amino sugars are diluted by plant-derived litter. This study provides information on the microbial residues in undisturbed forest soils which may assist interpretation of data derived from managed or damaged forests in the future. [ABSTRACT FROM AUTHOR]

Evaluates the methodological variability of microbial community-level physiological profiles in soil from an annual grassland ecosystem in California. Importance of microbial communities on soil functioning; Levels of soil replicates; Details of the cell counts and inoculum densities from soil sequential extraction.

A letter to the editor is presented in response to the article "Microbial Production of Recalcitrant Dissolved Organic Matter: Long-Term Carbon Storage in the Global Ocean," by Nianzhi Jiao, Kai Tang and Haiyuan Cai in the previous issue.

Abstract: Microbial residues can be a significant component of soil organic matter, and their component amino sugars are integrative indicators of biologically relevant ecosystem properties. We evaluate the impact of soil attributes, microbial functional group biomass, and cropping system type on soil amino sugar profiles in three model biofuel cropping systems in southern Wisconsin, USA. Total soil carbon and clay content explained differences in soil amino sugar profiles, with glucosamine and galactosamine more strongly related to soil carbon and muramic acid associated with clay content. Amino sugars were not correlated to cropping system or to microbial functional group lipid abundance, suggesting amino sugar differences among locations were due to differences in soil legacy properties such as total carbon, clay content and culture age rather than to current biotic drivers. The disconnect between the current biotic composition and legacies of past microbial activity suggests that microbial residues should be considered as trajectories over time rather than static system properties. [Copyright &y& Elsevier]