DOCSLIB.ORG

Tracing Energy Flow in Stream Food Webs Using Stable Isotopes Of

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Tracing Energy Flow in Stream Food Webs Using Stable Isotopes Of Freshwater Biology (2010) 55, 941–951 doi:10.1111/j.1365-2427.2009.02327.x Tracing energy flow in stream food webs using stable isotopes of hydrogen ,† ‡ † JACQUES C. FINLAY* , RICHARD R. DOUCETT AND CAMILLE MCNEELY *Department of Ecology, Evolution and Behavior, University of Minnesota, St Paul, MN, U.S.A. †St Anthony Falls Laboratory, National Center for Earth-surface Dynamics, University of Minnesota, MN, U.S.A. ‡Colorado Plateau Stable Isotope Laboratory, Merriam Powell Center for Environmental Research, Northern Arizona University, Flagstaff, AZ, U.S.A. SUMMARY 1. Use of the natural ratios of carbon and nitrogen stable isotopes as tracers of trophic interactions has some clear advantages over alternative methods for food web analyses, yet is limited to situations where organic materials of interest have adequate isotopic separation between potential sources. This constrains the use of natural abundance stable isotope approaches to a subset of ecosystems with biogeochemical conditions favourable to source separation. 2. Recent studies suggest that stable hydrogen isotopes (dD) could provide a robust tracer to distinguish contributions of aquatic and terrestrial production in food webs, but variation in dD of consumers and their organic food sources are poorly known. To explore the utility of the stable hydrogen isotope approach, we examined variation in dD in stream food webs in a forested catchment where variation in d13C has been described previously. 3. Although algal dD varied by taxa and, to a small degree, between sites, we found consistent and clear separation (by an average of 67&) from terrestrial carbon sources. Environmental conditions known to affect algal d13C, such as water velocity and stream productivity did not greatly influence algal dD, and there was no evidence of seasonal variation. In contrast, algal d13C was strongly affected by environmental factors both within and across sites, was seasonally variable at all sites, and partially overlapped with terrestrial d13C in all streams with catchment areas larger than 10 km2. 4. While knowledge of isotopic exchange with water and trophic fractionation of dD for aquatic consumers is limited, consistent source separation in streams suggests that dD may provide a complementary food web tracer to d13C in aquatic food webs. Lack of significant seasonal or spatial variation in dD is a distinct advantage over d13C for applications in many aquatic ecosystems. Keywords: energy flow, food webs, stable isotopes, subsidies, trophic interactions Introduction Correspondence: Jacques C. Finlay, Department of Ecology, Knowledge of the sources and fluxes of energy and Evolution and Behavior, University of Minnesota, 1987 Upper nutrients through food webs is integral to under- Buford Circle, St Paul, MN 55108, U.S.A. standing the productivity and diversity of consumers E-mail: jfi[email protected] and essential to any effort to understand their Present address: Camille McNeely, Department of Biology, ecological interactions. The sources of organic matter Eastern Washington University, 258 Science Building, Cheney, that fuel aquatic consumers are highly diverse in WA 99004-2440, U.S.A. space and time, a feature that has presented Ó 2009 Blackwell Publishing Ltd 941 942 J. C. Finlay et al. substantial challenges to understanding food web used to measure trophic position, d15N can provide a dynamics. Stable isotopes are increasingly used to complementary source tracer to d13C in some settings, trace energy flow and trophic structure in food webs such as at the marine–freshwater interface, and in because they integrate across spatial and temporal highly eutrophic ecosystems where source differences scales and thus provide important information that is are large (e.g. Delong & Thorp, 2006). Such applica- not otherwise accessible without very large expendi- tions are limited, however, by variable trophic frac- tures of research time and resources (Peterson & Fry, tionation by primary consumers (e.g. Goedkoop, 1987). Akerblom & Demandt, 2006) and temporal changes Most natural abundance isotope studies of diet in organic matter d15N because of variation in d15Nof sources use stable isotopes of carbon (i.e. d13C). dissolved inorganic nitrogen and microbial immobil- Tracing of sources using d13C in aquatic ecosystems isation of N onto organic matter (Finlay & Kendall, relies on isotopic differences between potential or- 2007). Sulphur stable isotopes (d34S) are increasingly ganic matter sources that arise from variation within used to complement d13C analyses in organic matter or among ecosystems in plant d13C, usually because of source tracing. A recent review found that d34S effects of inorganic carbon d13C and fractionation of distinguished organic matter sources in coastal inorganic carbon d13C during photosynthesis (Peter- marine ecosystems better than d15N (Connolly et al., son & Fry, 1987). After carbon is fixed by plants, there 2003). Within freshwater ecosystems, however, the are minor changes associated with aerobic decompo- sparse data available indicate relatively little differ- sition and trophic transfer so that d13C is an effective ence between major organic matter sources in d34Sin tracer of diet sources (Vander Zanden & Rasmussen, most ecosystems (Finlay & Kendall, 2007). 2001). While environmental variation or physiological Hydrogen stable isotopes (i.e. 2H and 1H, deute- differences among plants create useful separation rium : hydrogen, dD, or d2H) in organic materials are between source d13C in some streams and lakes (e.g. variable in the environment and could provide an Finlay, 2001; Grey, Jones & Sleep, 2001), there are alternative or complementary natural abundance iso- others where source d13C overlap occurs during some topic tracer to those of carbon, nitrogen and sulphur. or all of the year. Terrestrial plants show a somewhat dD is increasingly used to track movement and limited range of d13C values such that variation in migrations of animals (Hobson, 1999; Bowen, Was- algal d13C largely determines the degree of overlap senaar & Hobson, 2005) but has not been widely used between allochthonous and autochthonous sources in to distinguish organic matter sources and energy freshwaters (Finlay & Kendall, 2007). Algal d13C can flow pathways in food webs. Such use was consid- have a range that exceeds 15& within a site because of ered decades ago (Smith & Epstein, 1970; Estep & variation in water flow (France, 1995; Hecky & Dabrowski, 1980) but was not widely adopted because Hesslein, 1995; Trudeau & Rasmussen, 2003; Singer of methodological limitations and concern about et al., 2005), biomass (Hill & Middleton, 2006), dis- unexplained variability in dD (see Doucett et al., 2007). 13 solved CO2 concentrations and d C of dissolved Recent advances in stable hydrogen isotope meth- inorganic carbon (Finlay, 2004). In aquatic ecosystems ods have triggered new interest in dD as a tracer in where environmental conditions are highly dynamic, freshwater ecosystems. dD has been most commonly tracing of energy flow with d13C may not be possible analysed in specific compounds rather than bulk or may require a high intensity sampling effort. organic materials because of variation among biolog- Greater knowledge of environmental effects on ical tissues and methodological concerns. Improved variation in d13C values of sources and recognition analytical techniques (Wassenaar & Hobson, 2003) of the inherent complexity of many food webs have, however, addressed some of the methodological suggests a need for additional tracers of energy flow issues associated with analyses of bulk tissues. Fur- pathways in aquatic ecosystems. Use of multiple ther, a recent study suggests that effects of trophic tracers greatly increases the ability to resolve organic fractionation and exchange of isotopes between matter sources in food webs and ecosystems (Phillips organism and water are relatively small and may be & Gregg, 2003). The stable isotope tracer often used to predictable (Solomon et al., 2009). Finally, a study in complement d13C in natural abundance studies of rivers of the southwestern U.S.A. demonstrated a aquatic ecosystems is d15N. While most commonly large isotopic separation between non-exchangeable Ó 2009 Blackwell Publishing Ltd, Freshwater Biology, 55, 941–951 Hydrogen isotope tracing in food webs 943 dD in terrestrial and aquatic sources of organic matter Methods and their consumers (Doucett et al., 2007). Together, General approach these advances suggest the potential of dDasan effective tool to analyse energy flow in aquatic food The primary study sites were in the South Fork of the webs. Eel River catchment in the Coast Range of Mendocino There is, however, little information to determine County, CA. Previous studies of stream food webs at the general efficacy of source separation using dD. In this site have identified the controls over d13Cof plants, stable isotope ratios are determined by the d resources and invertebrate consumers (Finlay, Power value of inorganic nutrients and fractionation during & Cabana, 1999; Finlay, Khandwala & Power, 2002; photosynthetic uptake. Inorganic hydrogen incorpo- McNeely, Clinton & Erbe, 2006; McNeely, Finlay & rated into plant biomass is derived from water. While Power, 2007). Here, we examined dD source separa- dD of precipitation may be highly variable over short tion through a combination of dD measurements of timescales, ground and surface water are more tem- archived samples previously analysed for d13C and porally integrated and show more dampened
Load more

Recommended publications
  • The Effects of Detritus Input on Soil Organic Matter Content and Carbon Dioxide Emission in a Central European Deciduous Forest
    Acta Silv. Lign. Hung., Vol. 7 (2011) 87–96 The Effects of Detritus Input on Soil Organic Matter Content and Carbon Dioxide Emission in a Central European Deciduous Forest a* b c István FEKETE – Zsolt KOTROCZÓ – Csaba VARGA – b b Zsuzsa VERES – János Attila TÓTH a Institute of Environmental Science, College of Nyíregyháza, Nyíregyháza, Hungary b Department of Ecology, University of Debrecen, Debrecen, Hungary c Department of Land and Environmental Management, College of Nyíregyháza, Nyíregyháza, Hungary Abstract – A major objective of our research was to survey soil biological activity and organic matter content reduction in a Central European oak forest during treatments of various detritus inputs within the Síkf őkút DIRT ( Detritus Input and Removal Treatments ) Project. Beside the control, three detritus removal and two detritus duplication treatments were applied. Our examinations have proven that soil organic matter content declined relatively fast in detritus removal treatments. The reduction was especially remarkable in root detritus removal treatments, where – due to the lack of transpiration – soils were moister during the whole year than in the other treatments. The higher moisture content, despite of the reduction of detritus input, produced an intense soil respiration. This can be explained by the fact that decomposing organisms have increased the use of soil organic matter. Detritus input reduction had a significantly greater effect on soil respiration and organic matter content than detritus input duplication of the same extent. The latter did not cause any significant change compared to the control. litter manipulation / soil respiration / DIRT Project / humus content / climate change Kivonat – Az avarinput hatása a talaj szerves anyag tartalmára és szén-dioxid kibocsátására egy Közép-európai lombhullató erd őben.
    [Show full text]
  • Power Sources Challenge
    POWER SOURCES CHALLENGE FUSION PHYSICS! A CLEAN ENERGY Summary: What if we could harness the power of the Sun for energy here on Fusion reactions occur when two nuclei come together to form one Earth? What would it take to accomplish this feat? Is it possible? atom. The reaction that happens in the sun fuses two Hydrogen atoms together to produce Helium. It looks like this in a very simplified way: Many researchers including our Department of Energy scientists and H + H He + ENERGY. This energy can be calculated by the famous engineers are taking on this challenge! In fact, there is one DOE Laboratory Einstein equation, E = mc2. devoted to fusion physics and is committed to being at the forefront of the science of magnetic fusion energy. Each of the colliding hydrogen atoms is a different isotope of In order to understand a little more about fusion energy, you will learn about hydrogen, one deuterium and one the atom and how reactions at the atomic level produce energy. tritium. The difference in these isotopes is simply one neutron. Background: It all starts with plasma! If you need to learn more about plasma Deuterium has one proton and one physics, visit the Power Sources Challenge plasma activities. neutron, tritium has one proton and two neutrons. Look at the The Fusion Reaction that happens in the SUN looks like this: illustration—do you see how the mass of the products is less than the mass of the reactants? That is called a mass deficit and that difference in mass is converted into energy.
    [Show full text]
  • Fractionation and Characterization of Natural Organic Matter from Certain Rivers and Soils by Free-Flow Electrophoresis
    Fractionation and Characterization of Natural Organic Matter from Certain Rivers and Soils by Free-Flow Electrophoresis GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1817-E Fractionation and Characterzation of Natural Organic Matter from Certain Rivers and Soils by Free-Flow Electrophoresis By J. A. LEENHEER and R. L. MALCOLM ORGANIC SUBSTANCES IN WATER GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1817-E UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1973 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog-card No. 73-600209 For sale by the Superintendent of Documents, U. S. Government Printing Office Washington, D. C. 20402 - Price 35 cents (paper cov«?r) Stock No. 2401-02400 CONTENTS Page Abstract ___________________________________________ El Introduction __________________________________ __ 1 Methods and materials __________________________________ 3 Sample preparation ______ _______ _ __ 3 Sample description _________________________________ 3 Separation procedure _______ ___________ __ 4 Assay of fractions ___________________________________ 4 Results and discussion _ _______________ 5 Conclusions ________________________________________ 12 References _____________________________________ __ 14 ILLUSTRATIONS Page FIGURES 1-3. Graphs showing: 1. Organic-carbon and optical-density electrophoretic fraction- ation curves for organic materials from soil and from river water ___________________________ E6 2. Organic-carbon and polysaccharide electrophoretic
    [Show full text]
  • Determining the Fraction of Organic Carbon RISC Nondefault Option
    Indiana Department of Environmental Management Office of Land Quality 100 N. Senate Indianapolis, IN 46204-2251 GUIDANCE OLQ PH: (317) 232-8941 Indiana Department of Environmental Management Office of Land Quality Determining the Fraction of Organic Carbon RISC Nondefault Option Background Soil can be a complex mixture of mineral-derived compounds and organic matter. The ratios of each component can vary widely depending on the type of soil being investigated. Soil organic matter is a term used by agronomists for the total organic portion of the soil and is derived from decomposed plant matter, microorganisms, and animal residues. The decomposition process can create complex high molecular weight biopolymers (e.g., humic acid) as well as simpler organic compounds (decomposed lignin or cellulose). Only the simpler organic compounds contribute to the fraction of organic carbon. There is not a rigorous definition of the fraction of organic carbon (Foc). However, it can be thought of as the portion of the organic matter that is available to adsorb the organic contaminants of concern. The higher the organic carbon content, the more organic chemicals may be adsorbed to the soil and the less of those chemicals will be available to leach to the ground water. A nondefault option in the Risk Integrated System of Closure (RISC) is to use Foc in the Soil to Ground Water Partitioning Model to calculate a site specific migration to ground water closure level. In the Soil to Ground Water Partition Model, the coefficient, Kd, for organic compounds is the Foc multiplied by the chemical-specific soil organic carbon water partition coefficient, Koc.
    [Show full text]
  • Progress and Challenges in Using Stable Isotopes to Trace Plant Carbon and Water Relations Across Scales
    Biogeosciences, 9, 3083–3111, 2012 www.biogeosciences.net/9/3083/2012/ Biogeosciences doi:10.5194/bg-9-3083-2012 © Author(s) 2012. CC Attribution 3.0 License. Progress and challenges in using stable isotopes to trace plant carbon and water relations across scales C. Werner1,19, H. Schnyder2, M. Cuntz3, C. Keitel4, M. J. Zeeman5, T. E. Dawson6, F.-W. Badeck7, E. Brugnoli8, J. Ghashghaie9, T. E. E. Grams10, Z. E. Kayler11, M. Lakatos12, X. Lee13, C. Maguas´ 14, J. Ogee´ 15, K. G. Rascher1, R. T. W. Siegwolf16, S. Unger1, J. Welker17, L. Wingate18, and A. Gessler11 1Experimental and Systems Ecology, University Bielefeld, 33615 Bielefeld, Germany 2Lehrstuhl fur¨ Grunlandlehre,¨ Technische Universitat¨ Munchen,¨ 85350 Freising-Weihenstephan, Germany 3UFZ – Helmholtz Centre for Environmental Research, Permoserstr. 15, 04318 Leipzig, Germany 4University of Sydney, Faculty of Agriculture, Food and Natural Resources, 1 Central Avenue, Eveleigh, NSW 2015, Australia 5College of Oceanic and Atmospheric Sciences, Oregon State University, 104 COAS Admin Bldg, Corvallis (OR), USA 6Center for Isotope Biogeochemistry, Department of Integrative Biology, University of California, Berkeley, CA 94720, USA 7Potsdam Institute for Climate Impact Research (PIK) PF 60 12 03, 14412 Potsdam, Germany 8CNR – National Research Council of Italy – Institute of Agro-environmental and Forest Biology, via Marconi 2, 05010 Porano (TR), Italy 9Laboratoire d’Ecologie, Systematique´ et Evolution (ESE), CNRS AgroParisTech – UMR8079, Batimentˆ 362, Universite´ de Paris-Sud (XI), 91405 Orsay Cedex, France 10Ecophysiology of Plants, Department of Ecology and Ecosystem Management, Technische Universitat¨ Munchen,¨ Von-Carlowitz-Platz 2, 85354 Freising, Germany 11Institute for Landscape Biogeochemistry Leibniz-Zentrum fur¨ Agrarlandschaftsforschung (ZALF) e.V., Eberswalderstr.
    [Show full text]
  • Is Extraterrestrial Organic Matter Relevant to the Origin of Life on Earth?
    IS EXTRATERRESTRIAL ORGANIC MATTER RELEVANT TO THE ORIGIN OF LIFE ON EARTH? D. C. B. WHITTET Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, NY 12180, U.S.A. (Received 19 August 1996) Abstract. I review the relative importance of internal and external sources of prebiotic molecules on Earth at the time of life's origin 3.7 Gyr ago. The ef®ciency of synthesis in the Earth's atmosphere was critically dependent on its oxidation state. If the early atmosphere was non-reducing and CO2- dominated, external delivery might have been the dominant source. Interplanetary dust grains and micrometeorites currently deliver carbonaceous matter to the Earth's surface at a rate of 3 5 7 10 kg/yr (equivalent to a biomass in 2 Gyr), but this may have been as high as 5 10 kg/yr (a biomass in only 10 Myr) during the epoch of late bombardment. Much of the incoming material is in the form of chemically inactive kerogens and amorphous carbon; but if the Earth once had a dense (10-bar) atmosphere, small comets rich in a variety of prebiotic molecules may have been suf®ciently air-braked to land non-destructively. Lingering uncertainties regarding the impact history of the Earth and the density and composition of its early atmosphere limit our ability to draw ®rm conclusions. 1. Introduction In at least one sense, a connection between the Universe at large and life in our small corner of it is inevitable. The hydrogen, carbon, nitrogen, oxygen, and other elements that make up our bodies and other living things were created billions of years ago in the interiors of stars and, in the case of hydrogen, in the the Big Bang itself (see Trimble, 1997, in this volume for an eloquent review).
    [Show full text]
  • The Nature and Dynamics of Soil Organic Matter: Plant Inputs, Microbial Transformations, and Organic Matter Stabilization
    Soil Biology & Biochemistry 98 (2016) 109e126 Contents lists available at ScienceDirect Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio Review paper The nature and dynamics of soil organic matter: Plant inputs, microbial transformations, and organic matter stabilization Eldor A. Paul Natural Resource Ecology Laboratory and Department of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523-1499, USA article info abstract Article history: This review covers historical perspectives, the role of plant inputs, and the nature and dynamics of soil Received 19 November 2015 organic matter (SOM), often known as humus. Information on turnover of organic matter components, Received in revised form the role of microbial products, and modeling of SOM, and tracer research should help us to anticipate 31 March 2016 what future research may answer today's challenges. Our globe's most important natural resource is best Accepted 1 April 2016 studied relative to its chemistry, dynamics, matrix interactions, and microbial transformations. Humus has similar, worldwide characteristics, but varies with abiotic controls, soil type, vegetation inputs and composition, and the soil biota. It contains carbohydrates, proteins, lipids, phenol-aromatics, protein- Keywords: Soil organic matter derived and cyclic nitrogenous compounds, and some still unknown compounds. Protection of trans- 13C formed plant residues and microbial products occurs through spatial inaccessibility-resource availability, 14C aggregation of mineral and organic constituents, and interactions with sesquioxides, cations, silts, and Plant residue decomposition clays. Tracers that became available in the mid-20th century made the study of SOM dynamics possible. Soil carbon dynamics Carbon dating identified resistant, often mineral-associated, materials to be thousands of years old, 13 Humus especially at depth in the profile.
    [Show full text]
  • Unit 2.3, Soil Biology and Ecology
    2.3 Soil Biology and Ecology Introduction 85 Lecture 1: Soil Biology and Ecology 87 Demonstration 1: Organic Matter Decomposition in Litter Bags Instructor’s Demonstration Outline 101 Step-by-Step Instructions for Students 103 Demonstration 2: Soil Respiration Instructor’s Demonstration Outline 105 Step-by-Step Instructions for Students 107 Demonstration 3: Assessing Earthworm Populations as Indicators of Soil Quality Instructor’s Demonstration Outline 111 Step-by-Step Instructions for Students 113 Demonstration 4: Soil Arthropods Instructor’s Demonstration Outline 115 Assessment Questions and Key 117 Resources 119 Appendices 1. Major Organic Components of Typical Decomposer 121 Food Sources 2. Litter Bag Data Sheet 122 3. Litter Bag Data Sheet Example 123 4. Soil Respiration Data Sheet 124 5. Earthworm Data Sheet 125 6. Arthropod Data Sheet 126 Part 2 – 84 | Unit 2.3 Soil Biology & Ecology Introduction: Soil Biology & Ecology UNIT OVERVIEW MODES OF INSTRUCTION This unit introduces students to the > LECTURE (1 LECTURE, 1.5 HOURS) biological properties and ecosystem The lecture covers the basic biology and ecosystem pro- processes of agricultural soils. cesses of soils, focusing on ways to improve soil quality for organic farming and gardening systems. The lecture reviews the constituents of soils > DEMONSTRATION 1: ORGANIC MATTER DECOMPOSITION and the physical characteristics and soil (1.5 HOURS) ecosystem processes that can be managed to In Demonstration 1, students will learn how to assess the improve soil quality. Demonstrations and capacity of different soils to decompose organic matter. exercises introduce students to techniques Discussion questions ask students to reflect on what envi- used to assess the biological properties of ronmental and management factors might have influenced soils.
    [Show full text]
  • Improving Garden Soils with Organic Matter, EC 1561
    EC 1561 • May 2003 $2.50 Improving Garden Soils with Organic Matter N. Bell, D.M. Sullivan, L.J. Brewer, and J. Hart This publication will help you understand the • Tomatoes and peppers get blossom-end rot, importance of soil organic matter levels to good even if fertilized with calcium. plant performance. It also contains suggestions • Water tends to pool on the soil surface and to for suitable soil amendments. Any soil, no drain slowly, or it runs off the surface. matter how compacted, can be improved by the addition of organic matter. The result will be a nnnn better environment for almost any kind of plant. What makes a productive soil? nnnn A productive soil provides physical support, water, air, and nutrients to plants and soil- What gardening problems are dwelling organisms (see “What is soil?” caused by poor soil quality? page 2). Like humans, roots and soil organisms Many problems with home vegetable gar- breathe and require sufficient air and water to dens, fruit trees, shrubs, and flower gardens are live. As a result, a good soil is not “solid”; caused not by pests, diseases, or a lack of rather, between 40 and 60 percent of the soil nutrients, but by poor soil physical conditions. volume is pores. The pores may be filled with Symptoms of poor soil quality include the water or air, making both available to plants following. (see illustration on page 3). • The soil is dried and cracked in summer. The largest pores control aeration and move- • Digging holes in the soil is difficult, whether ment of water through the soil and are largely it is wet or dry.
    [Show full text]
  • Humus) from a Consideration of the Chemical and Biochemical Processes of Humification
    Evaluation of Conceptual Models of Natural Organic Matter (Humus) From a Consideration of the Chemical and Biochemical Processes of Humification By Robert L. Wershaw Scientific Investigations Report 2004-5121 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Gale A. Norton, Secretary U.S. Geological Survey Charles G. Groat, Director U.S. Geological Survey, Reston, Virginia: 2004 For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225 For more information about the USGS and its products: Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov/ Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. iii Contents Abstract.......................................................................................................................................................... 1 Introduction ................................................................................................................................................... 1 Purpose and scope.............................................................................................................................. 2 Degradation reactions of plant tissue ............................................................................................. 2 Degradation pathways of plant tissue components ............................................................................... 3 Enzymatic reactions
    [Show full text]
  • Hydrogen and Its Components
    HYDROGEN AND ITS COMPONENTS Discovery In 1671, Robert Boyle discovered and described the reaction between iron filings and dilute acids, which resulted in the production of hydrogen gas. In 1766-81, Henry Cavendish was the first to recognize that hydrogen gas was a discrete substance, and that it produced water when burned. He named it "flammable air". In 1783, Antoine Lavoisier gave the element the name hydrogen (from the Greek σδρο-hydro meaning "water" and -γενης genes meaning "creator") when he and Pierre-Simon Laplace reproduced Cavendish's finding that water was produced when hydrogen was burned. Hydrogen was liquefied for the first time by James Dewar in 1898 by using regenerative cooling and his invention, the vacuum flask. He produced solid hydrogen the next year. Deuterium was discovered in December 1931 by Harold Urey, and tritium was prepared in 1934 by Ernest Rutherford, Mark Oliphant, and Paul Harteck. Heavy water, which consists of deuterium in the place of regular hydrogen, was discovered by Urey's group in 1932. The nickel hydrogen battery was used for the first time in 1977 aboard the U.S. Navy's Navigation technology satellite-2 (NTS-2). It had two caesium atomic clocks on board and helped to show that satellite navigation based on precise timing was possible. In the dark part of its orbit, the Hubble Space Telescope is powered by nickel-hydrogen batteries, which were finally replaced in May 2009, more than 19 years after launch, and 13 years passed their design life. from NASA (accessed 2 Feb 2015) Isotopes of hydrogen Hydrogen has three naturally occurring isotopes, denoted 1H, 2H and 3H.
    [Show full text]
  • Inherent Factors Affecting Soil Organic Matter
    Soil organic matter (SOM) is the organic component of soil, consisting of three primary parts including small (fresh) plant residues and small living soil organisms, decomposing (active) organic matter, and stable organic matter (humus). Soil organic matter serves as a reservoir of nutrients for crops, provides soil aggregation, increases nutrient exchange, retains moisture, reduces compaction, reduces surface crusting, and increases water infiltration into soil. Components vary in proportion and have many intermediate stages (Figure 1). Plant residues on the soil surface such as leaves, manure, or crop residue are not considered SOM and are usually removed from soil samples by sieving through a 2 mm wire mesh before analysis. Soil organic matter content can be estimated in the field and tested in a lab to provide estimates for Nitrogen, Phosphorus and Sulfur mineralized available for crop production and adjust fertilizer recommendations. Soil organic matter impacts the rate of surface applied herbicides along with soil pH necessary to effectively control weeds. Soil organic matter impacts the potential for herbicide carryover for future crops, and amount of lime necessary to raise pH. Figure 1. Major soil organic matter components (Source: The Soil Food Web, USDA-NRCS). Inherent Factors Affecting Soil Organic Matter Inherent factors affecting soil organic matter such warm and humid and slower in cool, dry climates. as climate and soil texture cannot be changed. Organic matter also decomposes faster when soil is Climatic conditions, such as rainfall, temperature, well aerated (higher oxygen levels) and much moisture, and soil aeration (oxygen levels) affect slower on saturated wet soils (refer to soil the rate of organic matter decomposition.
    [Show full text]