Ấn phẩm:
The relationship between microbial communities, processes, and mine waste contamination in upper Clark Fork River alluvial soils
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Chapter 2:
Polyphasic studies that used phospholipid fatty acid analysis (PLFA) in conjunction with community level physiological profiling (CLPP) or PCR-based molecular methods were analyzed in order to evaluate the power of each strategy to detect treatment effects on soil microbial community structure (MCS). We found no studies where CLPP or PCR-based methods differentiated treatments that were not also differentiated by PLFA. In 14 of 32 studies (44%), PLFA differentiated treatments that were not resolved by CLPP analysis. In 5 of 25 studies (20%), PLFA differentiated treatments that were not resolved by PCR-based methods. We discuss PLFA, CLPP, and PCR-based methods with respect to power to discriminate change in MCS versus potential for characterization of underlying population level changes.
CHAPTER 3:
We used a 93-year-old mine waste contamination gradient in alluvial soil to explore the relationship between ecosystem level functioning and community structure in a chronically stressed ecosystem. The sensitivity of broad functional parameters (in situ soil respiration, microbial biomass, above and below ground plant biomass) and microbial diversity (phospholipid fatty acid (PLFA) abundance and richness) were compared. Functional responses were linear with respect to contaminants while thresholds were detected in the community structural response to contamination along the gradient. For example, in situ soil respiration was negatively and linearly correlated to contamination concentration (R = -0.783, P < 0.01), but changes in microbial community structure only became evident where contaminant concentrations were greater than 28 times above background levels. Our results suggest that functional redundancy does not prevent depression of ecosystem function in the long-term.
CHAPTER 4:
We present an application of a statistical approach, quantile regression (QR), which identifies trends in soil processes otherwise masked by spatial and temporal variability. QR identifies limits on processes and changes in the variance of a response along an environmental gradient. We quantified in situ soil respiration, pH, and heavy metal concentrations across a mine waste contamination gradient that spanned greater than an order of magnitude of metal concentrations. Respiration values were monitored at study sites over 2 y. We used QR to show that soil respiration was limited with respect to both heavy metals and pH, and that both increased metals and increased acidity constrained variation in soil respiration values. Maximum respiration values declined by 48% over the Metals Contamination Index (MCI) range and by 72% over the pH range. The use of QR avoided the necessity of discriminating between multiple sources of variation in a spatially and temporally variable system. It is often unrealistic or too time consuming and expensive to attempt to measure all of the relevant predictor variables in the field. The simpler approach offered by QR is to explore factors that limit a process, recognizing that not all of the factors contributing to a soil function will be measured. An application of this approach to the evaluation of a mine waste remediation procedure is discussed.
CHAPTER 5:
New approaches to discriminate contaminant effects from natural spatiotemporal variation under field conditions in long-term contaminated systems are needed in order to evaluate remediation options. We used a combination of sampling and statistical approaches to investigate the relative influence of metals, soil acidity, and organic matter on a suite of analogous plant and microbial community parameters (Plants: species percentage canopy cover, richness, and plant, graminoid, and forb biomass. Microbes: PLFA community profiles, PLFA richness, and microbial, bacterial, and fungal biomass) in floodplain soils contaminated by mine wastes in the early twentieth century. We compared the sensitivity of plant and microbial communities using quantile regression and multivariate analyses. We also investigated biological and geochemical changes that occurred along a short transect (64 cm) that spanned a transition from a productive grassland to an area of barren wasteland representing a total functional collapse of the grassland/soil ecosystem. Along the small-scale transect we quantified geochemical parameters (heavy metal concentrations, soil acidity, organic matter content, and soil moisture) and biological parameters (respiration, microbial PLFAs, microbial biomass, root biomass) in two layers, an upper layer (0-10 cm) and a lower layer (10-20 cm). In both studies plant and microbial communities were significantly affected by the mine wastes. Overall, plant communities were more sensitive to the wastes than microbial communities were. Mechanisms responsible for the observed differences in plant and microbial community responses are discussed. Results indicated that soil acidity and organic matter concentration exerted stronger effects on plant and microbial community structure than metals. We assert that removal of the floodplain surface is not necessary for remediation, rather liming and organic matter amendments would alleviate most of the toxic effects of the mine wastes.
Tác giả
Ramsey, Philip Wharton
Người hướng dẫn
Nơi xuất bản
Nhà xuất bản
The University of Montana
Năm xuất bản
2006
ISSN tạp chí
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Từ khóa chủ đề
Đất, Vi sinh , Mine wastes