Global Biogeochemistry Research Articles

FLOW CYTOMETRY AND THE SINGLE CELL IN PHYCOLOGY.

Flow cytometers measure light scattering and fluorescence characteristics from individual particles in a fluid stream as they cross one or more light beams at rates of up to thousands of events per second. Flow cytometrically detectable optical signals may arise naturally from algae, reflecting cell size, structure, and endogenous pigmentation, or may be generated by fluorescent stains that report the presence of otherwise undetected cellular constituents. Some flow cytometers can physically sort particles with desired optical characteristics out of the flow stream and collect them for subsequent culture or other analyses. The statistically rigorous, cell-level perspective provided by flow cytometry has been advantageous in experimental investigations of phycological problems, such as the regulation of cell cycle progression. The capacity of flow cytometry to measure large numbers of cells in large numbers of samples rapidly and quantitatively has been used extensively by biological oceanographers to define the distributions and dynamics of marine picophytoplankton. Recent work has shown that flow cytometry can be used to elucidate relationships between the optical properties of individual cells and the bulk optical properties of the water they live in, and thereby may provide an explicit link between algal physiology and global biogeochemistry. Unfortunately, commercially available flow cytometers that are optimized for biomedical applications have a limited capacity to analyze larger phytoplankton. To circumvent these limitations, many investigators are developing flow cytometers specifically designed for analyzing the broad range of sizes, shapes, and pigments found among algae. These new instruments can perform some novel measurements, including simple fluorescence excitation spectra, detailed angular scattering measurements, and in-flow digital imaging. The growing accessibility and power of flow cytometers may allow the technology to be applied to a wider array of problems in phycology, including investigations of nonplanktonic and multicellular algae, but also presents new challenges for effectively analyzing the large quantity of multiparameter data produced. Ultimately, the detection of molecular probes by flow cytometry may allow single-cell taxonomic and physiological information to be garnered for a variety of algae, both in culture and in nature.

Links between Transpiration and Plant Nitrogen: Variation with Atmospheric CO2 Concentration and Nitrogen Availability

Transpiration is closely linked to plant nitrogen (N) content, indicating that global or other changes that alter plant N accumulation or the relative requirements of plants for water and N will affect transpiration. We studied effects of N availability and atmospheric CO2 concentration, two components of global biogeochemistry that are changing, on relationships between whole-plant transpiration and N in two perennial C3 species, Pseudoroegneria spicata (a tussock grass) and Gutierrezia microcephala (a half-shrub). Two indices of plant N requirement were used: N accretion (N in live and dead tissues) and N loss in litter (N in dead tissues). Transpiration was analyzed as the product of N accretion or loss by plants and the ratio of transpiration to N accretion or loss. The two indices of plant N requirement led to different conclusions as to the effects of N availability on plant use of water relative to N. Transpiration scaled proportionally with N accretion, but transpiration per unit of N loss declined at high N. Carbon dioxide enrichment had little effect on the ratio of transpiration to N accretion and no effect on transpiration per unit of N loss. The two species accumulated similar amounts of N, but the half-shrub used more than twice as much water as the grass. Nitrogen availability and CO2 concentration influenced whole-plant transpiration more by changing plant N accumulation than by altering the stoichiometry between transpiration and plant N. Species differences in total water use, by contrast, reflected differences in the scaling of transpiration to plant N. A better understanding of species differences in water and N dynamics may thus be required to predict transpiration reliably.

Biogeochemical Cycles: A Computer‐Interactive Study of Earth System Science and Global Change

Global biogeochemistry is the discipline that links various aspects of biology, geology, and chemistry to investigate the surface environment of the Earth. The global biogeochemical cycles of the elements lie at the very core of the subject and involve a myriad of processes that transform and transport various substances throughout the Earth's ecosphere, which consists of the atmosphere, hydrosphere, shallow crust (soils, sediments, and crustal rocks), biosphere, and cryosphere. As the authors of Biogeochemical Cycles: A Computer‐Interactive Study of Earth System Science and Global Change say, “anyone interested in understanding the causes of global environmental change and its implications for life would be well‐advised to begin with an investigation of global biogeochemistry.” This small but illuminating book is an attempt to provide a reasonably integrated and comprehensive text dealing with the study of the life‐essential global biogeochemical cycles of carbon, phosphorus, nitrogen, sulfur, and oxygen.

Predicting the relative sensitivity of forest production in Ireland to site quality and climate change

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 10:51-67 (1998) - doi:10.3354/cr010051 Predicting the relative sensitivity of forest production in Ireland to site quality and climate change Christine L. Goodale1,*, John D. Aber1, Edward P. Farrell2 1Complex Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire 03824, USA2Department of Environmental Resource Management, University College Dublin, Agriculture Building Belfield, Dublin 4, Ireland *E-mail: christy.goodale@unh.edu Most model-based predictions of climate change effects on forest ecosystems have used either potential or static descriptions of vegetation and site, removing the effects of direct management or land use. In this paper we use a previously developed and validated model of carbon and water balances in forest ecosystems (PnET-II) to assess the relative sensitivity of forest production in Ireland to predicted climate change and to ambient variability in site quality. After validating the model against measured productivity for 2 sets of stands, we ran the model using existing variation in site quality, represented as differences in foliar N concentration, and also for predicted changes in climate and atmospheric CO2. Resulting variations in productivity were compared with those due to potential errors in the specification of input parameters and to variation in current ambient climate across the region. The effects on net primary production (NPP) and wood production of either ambient variation in climate or predicted changes in temperature, precipitation and CO2 are quite small (0 to 30%) relative to the effects of ambient variability in site quality (up to 400%). The range of possible variation in other user-specified physiological parameters resulted in changes of less than 10% in model predictions. We conclude that site-specific conditions and management practices result in a range of forest productivity that is much greater than any likely to be induced by climate change or CO2 enrichment. We also suggest that it is essential to understand and map spatial variability in site quality, as well as to understand how the productive capacity of landscapes will change in response to management and pollution loading, if we are to predict the actual role that climate change will play in altering forest productivity and global biogeochemistry. Regional modeling · Validation · Foliar nitrogen · Sitka spruce Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 10, No. 1. Online publication date: April 09, 1998 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 1998 Inter-Research.

Continental scale models of water balance and fluvial transport: An application to South America

A coupled water balance and water transport model (WBM / WTM) was constructed as part of a larger study of global biogeochemistry. The WBM / WTM provides critical hydrologic information to models of terrestrial primary production, organic matter decay, riverine nutrient flux and trace gas exchanges with the troposphere. Specifically, it creates high‐resolution data sets for monthly soil moisture, evapotranspiration, runoff, river discharge and floodplain inundation. As a first step toward eventual global coverage, the WBM / WTM was applied to South America, represented by more than 5700 1/2° (latitude / longitude) grid cells. The WBM transforms spatially complex data on long‐term climate, vegetation, soils and topography into predictions of soil moisture (SM), evapotranspiration (ET) and runoff (RO). For South America, field capacity in soils ranged from 27 to 582 mm of water, and computed values for mean annual SM, ET and RO were 284 mm, 1059 mm/yr and 619 mm/yr, respectively. There were large differences regionally and over the year. The transport model uses WBM‐derived runoff, information on fluvial topology, linear transfer through river channels and a simple representation of floodplain inundation to generate monthly discharge estimates for any cell within a simulated catchment. The WTM successfully determined the timing and magnitude of discharge at selected locations within the Amazon / Tocantins basin. It also demonstrated the importance of floodplain inundation in defining flow regime on the mainstem Amazon. Estimated mean annual discharge was 207,000 m3/s for the Amazon River and 17,000 m3/s for the Tocantins. In these basins, 45% of the incident precipitation emerges as river flow; 55% is lost to ET. The model described in this paper will be expanded to include the dynamics of carbon, major nutrients and sediments. It will serve as a semimechanistic tool to quantify the transport of materials from the landscape to the world's oceans. Such a capability becomes increasingly important as we seek to understand the impacts of climate and land use change on major river systems of the globe.

Variation of cadmium accumulation among Japanese.

Human liver, renal cortex, and heart muscle from 394 autopsied Japanese who had lived in eight districts of Japan were sampled. Subjects included 200 males between 0 to 89 yr of age and 194 females between 0 to 94 yr of age. Cadmium, copper, and zinc in both liver and renal cortex, as well as cadmium in heart muscle were compared by district, sex, age, and smoking habits. Statistical results revealed that the difference of each heavy metal distribution by eight districts is significant and that cadmium and zinc levels in liver and renal cortex sampled from north-central Japan were the highest. This probably results from the larger intake of dietary cadmium and zinc via rice since this area is known as one of the better rice growing regions in Japan. Although there is a lack of precise information on smoking habit, cadmium in liver and zinc in liver and renal cortex of males smoking eight or more cigarettes per day were statistically higher than that of nonsmokers and those who smoked less than seven cigarettes per day. However, cadmium in renal cortex was not significant between the two smoking groups. Further studies should be performed to determine the health significance of an increased intake of cadmium by populations from the viewpoint of global biogeochemistry.