Rapid amino acid cycling in arctic and antarctic soils

Amino acids constitute one of the largest inputs of organic nitrogen (N) to most polar soils and have been hypothesized to be important in regulating vegetational succession and productivity in Arctic ecosystems. Our understanding of amino acid cycling in these soils, however, is poor. The aim of this study was to investigate the size and rate of turnover of the amino acid pool in a range of Arctic and Antarctic soils. Our results indicate that in polar soils with either high or low ornithogenic inputs the amino acid pool is small in comparison to the inorganic N pool (NO^–₃ and NH⁺₄). The free amino acid pool constituted only a small proportion of the total dissolved organic nitrogen (DON) pool in these soils. Here we show that these low concentrations may be due to rapid use by the soil microbial community in both Arctic and Antarctic soils. The turnover of the amino acid pool in soil was extremely rapid, with a half-life ranging from 2 to 24 h, indicating that this N pool can be turned over many hundred times each summer when polar soils are frequently unfrozen. The implications of amino acids in N cycling and plant and microbial nutrition are discussed.     

Transition to self‐directed work teams: implications of transition time and self‐monitoring for managers' use of influence tactics

In the face of heightened competitive pressures, elevated quality expectations, and calls for worker empowerment, more and more organizations have turned to self‐directed work teams (SDWTs). A review of the literature devoted to SDWTs suggests that managers often struggle with the transition to SDWTs because of the required shift in control to SDWT members. To promote the development of work teams, managers must modify their use of influence tactics in direct response to the control shift. In this study, we explore changes in managers' usage of influence tactics during the transition to SDWTs within a large aluminum manufacturing plant. Analyses of longitudinal data show that despite the new team environment, managers' use of influence tactics was focused at the individual level. We also found that transition time accounts for variance in managers' choices of influence tactics. Finally, an exploratory analysis suggests that high as opposed to low self‐monitoring managers may be more prone to increase their usage of soft influence tactics and decrease their usage of hard influence tactics over the course of the transition; the influence behavior of low self‐monitoring managers remained unchanged. Implications for future research are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

REGION,LANDSCAPE, AND SCALE EFFECTS ON LAKE SUPERIOR TRIBUTARY WATER QUALITY1

ABSTRACT: In 1998 and 1999, third‐order watersheds in high mature forest (HMF) and low mature forest (LMF) classes were selected along gradients of watershed storage within each of two hydrogeomorphic regions in the Lake Superior Basin to evaluate threshold effects of storage on hydrologic regimes and watershed exports. Differences were detected between regions (North and South Shore) for particulates, nutrients, and pH, with all but silica values higher for South Shore streams (p < 0.05). Mature forest effects were detected for turbidity, nutrients, color, and alkalinity, with higher values in the LMF watersheds, that is, watersheds with less that 50 percent mature forest cover. Dissolved N, ammonium, N:P, organic carbon, and color increased, while suspended solids, turbidity, and dissolved P decreased as a function of storage. Few two‐way interactions were detected between region and mature forest or watershed storage, thus threshold based classification schemes could be used to extrapolate effects across regions. Both regional differences in water quality and those associated with watershed attributes were more common for third‐order streams in the western Lake Superior drainage basin as compared with second‐order streams examined in an earlier study. Use of ecoregions alone as a basis for setting regional water quality criteria would have led to misinterpretation of reference condition and assessment of impacts in the Northern Lakes and Forest Ecoregion.     

火电厂烟气脱硫装置的性能检测

详细介绍了火电厂烟气脱硫装置性能检测的指标、系统、组织、流程和方法,为脱硫工程后评估中脱硫装置的性能考核和验收检测提供了技术支持和指导。     

Rapid amino acid cycling in arctic and antarctic soils

Amino acids constitute one of the largest inputs of organic nitrogen (N) to most polar soils and have been hypothesized to be important in regulating vegetational succession and productivity in Arctic ecosystems. Our understanding of amino acid cycling in these soils, however, is poor. The aim of this study was to investigate the size and rate of turnover of the amino acid pool in a range of Arctic and Antarctic soils. Our results indicate that in polar soils with either high or low ornithogenic inputs the amino acid pool is small in comparison to the inorganic N pool (NO^? ₃ and NH⁺ ₄). The free amino acid pool constituted only a small proportion of the total dissolved organic nitrogen (DON) pool in these soils. Here we show that these low concentrations may be due to rapid use by the soil microbial community in both Arctic and Antarctic soils. The turnover of the amino acid pool in soil was extremely rapid, with a half-life ranging from 2 to 24 h, indicating that this N pool can be turned over many hundred times each summer when polar soils are frequently unfrozen. The implications of amino acids in N cycling and plant and microbial nutrition are discussed.     

An automated wet deposition system to compare the effects of reduced and oxidised N on ombrotrophic bog species: Practical considerations

Critical N loads for ombrotrophic bogs, which often contain rare and N-sensitive plants (especially those in lower plant groups: lichens, mosses and liverworts), are based on very few experimental data from measured, low background N deposition areas. Additionally the relative effects of reduced versus oxidised N are largely unknown. This paper describes an automated field exposure system (30 km S. of Edinburgh, Scotland) for treating ombrotrophic bog vegetation with fine droplets of oxidised N (NaNO₃) and reduced N (NH₄Cl). Whim Moss exists in an area of low ambient N deposition (ca. 8 kg N ha^?1 y^?1), the sources and quantification of which are described. The wet N treatment system is run continuously, and is controlled/activated by wind speed and rainfall to provide a unique simulation of “real worl” treatment patterns (no rain=no treatment). Simulated precipitation is supplied at ionic concentrations below 4 mM in rainwater collected on site. Treatments provide a replicated dose response to 16, 32 and 64 kg N ha^?1 y^?1 adjusted for ambient deposition (8 kg N ha^?1 y^?1). The 16 and 64 kg N ha^?1 y^?1 are duplicated with a P+K supplement. Baseline soil chemistry and foliar nutrient status was established for all 44 plots for Calluna vulgaris, Sphagnum capillifolium, Hypnum jutlandicum and Cladonia portentosa.     

Correlating the spatial distribution of atmospheric ammonia with δ15n values at an ammonia release site

A field ammonia (NH₃) release experiment and open top chambers containing moorland monoliths continuously fumigated with NH₃ or sprayed with NH₄Cl were used to assess the potential for using δ¹⁵N values in determining the area of influence around a point NH₃ emission source. δ¹⁵N values are being increasingly used as environmental tracers and we tested the hypothesis that the δ¹⁵N signal from an NH₃ emission source is observable in nearby vegetation. Using modified monitoring devices, atmospheric NH₃ concentrations were found to decrease with distance from source, with δ¹⁵N values also reflecting this trend, producing a signal shift with changing concentration. Open top chamber studies of δ¹⁵N values of Calluna vulgaris (L.) Hull indicated a correlation with deposition treatments in current year shoots. Analysis of Calluna shoots from the NH₃ release showed a similar trend of δ¹⁵N enrichment. Significant linear correlations between δ¹⁵N and percent N in plant material were found, both in the controlled conditions of the open top chambers and at the NH₃ release site, illustrating the possible use of this technique in N deposition biomonitoring.     

Application of a health promotion model to community-based sustainability planning

The future of human health and that of all other species depends on the viability and sustainability of a host of environments and ecosystems. Human behaviours have profound effects (both positive and negative) on such ecosystems. Despite the obviousness of these statements, there remains a lack of clarity around the mechanisms for altering specific behaviours related to sustainability and their impact on environments. This paper offers a conceptual framework for identifying relations between human behaviour and ecosystem health and sustainability. We also discuss strategies for changing target behaviours in the context of a programme or policy planning. Finally, we draw on research that applies this adaptation to a small island community near Vancouver, Canada.