Lecture 17 Organisms and Nitrogen

Lecture 17 Organisms and Nitrogen - Soil Organisms What...

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Unformatted text preview: Soil Organisms What creatures live in soil? 22 species Harvester Ant Colony Fauna Macro Micro Mammals, reptiles, insects, earthworms Flora Nematodes, Protozoa, Rotifers 20,000 species Plant roots, algae, fungi, actinomycetes (filamentous bacteria), bacteria unicellular Macrofauna: Earthworms Macrofauna: 1,000,000 per acre five pairs of hearts Mostly intestine 22 ft. long (Afr. and Aus.) Earthworm cast Casts: earthworm’s wastes Eat soil organics: 2-30 times of their own wt. Earthworms Earthworms Abundance of earthworms Abundance 10-1,000/m – 3 – 3,000 species Benefits of earthworms Benefits - soil fertility by producing cast - aeration & drainage - size & stability of soil aggregates Soil Fungi 10 - 100 billion/m Yeasts, molds, mushrooms 2 Cell with a nuclear membrane and cell wall Tolerate extremes in pH (bacteria do not) Most versatile & most active in acid forest soils Mycorrhizae symbiosis Mycorrhizae Association between fungi & plant root Increased SA (up to 10 times) Increased nutrient uptake, Increased especially P especially Mycorrhizae Fungi Mycorrhizae 1. Ions in solution 2. Movement from solution to root (diffusion) Phosphorous granule Fungal hyphae Root hair Symbiosis – – – Fungi provide nutrients Plant root provides carbon Ectomycorrhiza Root surfaces and cortex in forest trees Root – Endomycorrhiza Penetrate root cell walls agronomic cropscorn, cotton, wheat, & rice corn, Soil Bacteria Soil 10-100 trillion/m2 Single-celled organisms Rapid reproduction Small (<5 µm) Small Mostly heterotrophic Autotrophic Bacteria Impact the availability of soil nutrients (N,S) Quantification of Soil Organisms Quantification of Soil Organisms Three Criteria Numbers of organisms Numbers – – – Extremely numerous 1,000,000-1,000,000,000 /g soil 10,000 species /g soil Biomass – 1-8% of total soil organic matter Metabolic activity – Respiration: CO Respiration: CO 2 Soil Organisms in Surface Soils Organisms Organisms Microflora Bacteria Actinomycetes Fungi Algae #/g soil 108 -109 -10 107 -108 -10 105 -106 -10 104 -105 -10 Biomass (g/m2) 40-500 40-500 40-500 40-500 100-1,500 100-1,500 1-50 1-50 Fauna Protozoa Nematodes Mites Earthworms 104 -105 -10 10 -102 -10 1 -10 1 -10 Note those in White 2-20 2-20 1-15 1-15 1-2 1-2 10-150 10-150 Basic Classification of Organisms Food Oxygen Energy Source Based on food: live or dead Based Herbivores – Eat live plants Insects, mammals, reptiles Detritivores • Eat dead tissues: • Fungi, bacteria Predators – Eat other animals Insects, mammals, reptiles Based on O2 demand Aerobic Aerobic Active in O rich environment – 2 – Use free oxygen for metabolism Anaerobic Active in O poor environment – 2 Use combined oxygen (NO , SO ) Based on energy & C source Autotrophic (CO2) Autotrophic – Solar energy (photoautotrophs) – Chemical reaction w/inorganic elements N, S, & Fe (chemoautotrophs) N, Heterotrophic Energy from breakdown of organic matter Most Numerous Organisms are Major Determinants of Water Quality and the Impact or Availability of Water Pollutants Metals (Hg, Pb, As) Nutrients (N, P) Organic Chemicals (PCBs, Dioxins) The Earliest Organisms Autotrophic: produce complex organic compounds from simple inorganic molecules and an external source of energy. Organic = Carbon-containing Chemoautotrophs, Cyanobacteria, Plants 3.5 bya Autotrophs – Plants, Algae, Cyanobacteria Produce complex organic compounds from carbon dioxide using energy from light. energy light 6CO2 + 6H O 2 simple inorganic molecule C6H12O6 + 6O2 complex organic compound Primary producers – base of the food chain Heterotrophs Derive energy from consumption of complex organic compounds produced by autotrophs Autotrophs store energy from the sun in carbon compounds (C6H12O6) Heterotrophs consume these complex carbon compounds for energy autotrophs carbon compounds (C H O ) Heterotrophs Organisms Heterotrophs: use carbon compounds for energy - consumers Heterotrophs Anaerobic Aerobic live in low-oxygen environments live in high oxygen environments Aerobic heterotrophs Anaerobic heterotrophs Aerobic Heterotrophs and Anaerobic Heterotrophs Aerobic Heterotrophs Live in high-oxygen environments Consume organic compounds for energy Obtain the energy stored in complex organic compounds by combining them with oxygen C6H12O6 + Oxygen = energy Aerobic Respiration C6H12O6 + 6O → 6CO2 + 6H2O 2 + energy The energy is obtained by exchanging electrons during chemical reactions. Electron poor Electron rich C6H12O6 + 6O2 → 6CO2 + 6H2O Electron rich Electron poor 2880 kJ of energy is produced Aerobic respiration is very efficient, yielding high amounts of energy Anaerobic Heterotrophic Organisms Live in low-oxygen environments Consume organic compounds for energy Can use energy stored in complex carbon compounds in the absence of free oxygen The energy is obtained by exchanging electrons with elements other than oxygen. Nitrogen (NO3) Sulfur (SO4) Iron (Fe3+) Aerobic Respiration Electron poor Electron rich C6H12O6 + 6O2 → 6CO2 + 6H2O Electron poor Electron rich Anaerobic respiration Electron poor Electron rich C H O + 3NO3 + 3H O = 6HCO + 3NH4+ 6 12 Electron rich 6 - 2 3- Electron poor Anaerobic respiration is less efficient and produces less energy. C6H12O6 + 6O2 → 6CO2 + 6H2O C H O + 3NO3- + 3H O = 6HCO + 3NH C6H12O6 + 3SO42- + 3H = 6HCO 3- + 3HS 4+ 2 2880 kJ 1796 kJ 453 kJ 6 12 6 + 3- - The oxygen status of soil/water determines the type of organisms aerobic or anaerobic High-oxygen Low-oxygen Oxygen status impacts availability of nutrients as well As the availability and toxicity of some pollutants Example: Eutrophication Nutrient Additions Nutrient addition increases primary productivity (algae) Sunlight is limited at greater depth Photosynthetic life O2 bacteria Photoautotrophs die and become food for aerobic heterotrophs Aerobic autotrophs consume oxygen Oxygen content in water is reduced If oxygen is reduced sufficiently, aerobic microbes cannot survive, and anaerobic microbes take over Respiration and Still Ponds O2 Aerobic heterotrophs consume oxygen NO Heterotrophic Organisms Anaerobic heterotrophs Use nitrate instead of O oxygen 2 SO 3- SO-2 4 Anaerobic heterotrophs Use sulfate instead of O HS 2 C6H12O6 + 3SO 4-2 - + 3H+ = 6HCO3- + 3HS 42- - Organisms and Nutrients Nitrogen Nitrogen Nitrogen and Soil Nitrogen The most limiting essential element in the environment Surface soil range: 0.02 to 0.5% 0.15% is representative 1 hectare = 3.3 Mg Biological/Plant Nitrogen Biological/Plant Component of living systems Amino acids Proteins Enzymes Nucleic acids (DNA) Chlorophyll Strongly limiting in the Environment Deficiency Deficiency Chlorosis – pale, yellow­green appearance primarily in older tissues. Excess Excess Enhanced vegetative growth – lodging Over production of foliage high in N Delayed maturity Degraded fruit quality N Distribution/Cycling Distribution/Cycling N2, NO, N2O Atmosphere Soil / soil O.M. NH4+, NO3-, R – NH2 Plants, animals Proteins, amino acids Organic Nitrogen (plant tissue, Soil Organic Matter): R – NH2 During organic decomposition, R – NH2 is usually broken down to NH4+ NH4+ is converted to NO3- by soil microorganisms Forms: mineral and organic Organic: plant/tissue N R-NH 2 Cycling in the Environment Mineral: soil N Mineralization: Decomposition of organicNH , NO forms releasing nitrogen into the soil, generally as NH4+ 4+ 3- Immobilization: Plant uptake of mineral nitrogen, removing it from the soil and incorporating into plant tissue. Ammonium and Nitrate Ammonium Mineralization R – NH2 NH4+ organic mineral Immobilization R – NH2 NH4+ or NO 3- Cycling of Nitrogen R-NH2 is organically bound form of nitrogen N2 X R-NH2 Decomposition Of O.M. NH4+ Uptake by plant nitrosomonas NO2- Uptake by plant nitrobacter NH4+ is exchangeable, NO3- is not NO3- Atmospheric Nitrogen Fixation Forms of Nitrogen R-NH2 is organically bound form of nitrogen N2 X R-NH2 Decomposition Of O.M. NH4+ Uptake by plant nitrosomonas NO2- Uptake by plant nitrobacter NH4+ is exchangeable, NO3- is not NO3- Symbiotic Biological Nitrogen Fixation Symbiosis between plant roots and rhizobium bacteria Rhizobium N2 NH4+ Nodules are packed with Rhizobium Nitrogen and Legumes Residue from legume crops is usually high in N when compared with residue from other crops and can be a major source of N for crops that follow legumes in rotation. Most of the N contained in crop residue is not available to plants until microbes decompose the plant material. N Contributions alfalfa range from 100 to 150 lbN/acre Soybeans range from 20-40 lb/acre Nitrogen Fixation is Difficult and Specialized Nitrogen N2 + 6H2 2NH3 Fixing N2 is energetically “expensive” NN Triple bond – Must use energy to break these bonds Artificial Nitrogen Fixation Artificial Haber - Bosch Process - Artificial Fixation of Nitrogen Gas: Nitrogen – 200 atm yield of 10-20% 400-500 C 400-500 – o – roduces 500 million tons of artificial N fertilizer per year. P no oxygen 1% of the world's energy supply is used for it Sustains roughly 40% of the world’s population Nitrogen and Food Food production has grown with population Crop Varieties Fertilizers 70% of water used Irrigated land expected to expand by 23% in 25 years Nitrogen Fertilization Nitrogen NH4+ NO 3- Negative Exchange sites NO 3- Loss of Productivity Leaching to groundwater, surface water Some Areas of Florida are Susceptible Approximately 250 million years ago Approximately 150 - 200 million years ago Late Jurassic Flooded, stable platform Subject to marine sedimentation FL platform/plateau For the next several million years the platform was dominated by carbonate sedimentation Sedimentation: settling of particles from a fluid due to gravity Carbonate Deposition/Sedimentation Marine Calcium and Magnesium Carbonate CaCO3 MgCO3 Between about 150 Mya and 25 Mya Florida platform was a flooded, submarine plateau dominated by carbonate deposition CaCO3 FL platform * The Eocene and Oligocene Limestone The Eocene and Oligocene limestone forms the principal fresh water-bearing unit of the Floridan Aquifer, one of the most productive aquifer systems in the world Eocene: 55 – 34 million years ago Oligocene: 34 – 24 million years ago Marine Carbonates carbonates Prior to 24 Mya Between 150 and 25 Mya, Florida was dominated by carbonate deposition Continental Influences highlands Sediments Isolation of the Florida Peninsula Sediments Georgia Channel Suwannee Current Events of the Late Oligocene Epoch, approximately 25 Mya Raising of the Florida Platform Lowering of Sea Levels, Interruption of Suwannee Current Suwannee Current Exposure of Limestone The Oligocene marked the beginning of a world wide cooling trend and lower sea Levels. Erosion cavities Due to acidity Miocene Epoch: began approximately 24 Mya sediments Rejuvenation of Appalachians, weathering, increased sediment load Sediments were sands, silts, clays Filling in the Georgia Channel Sediments Early Miocene (~ 24 Mya) Sediments Rising sea levels allow sediments to become suspended in water and drift over the platform Siliciclastics Covered the Peninsula Sands And Clays Summary 1. 1. 1. 1. Deposition of Eocene/Oligocene Limestone (55 – 24 Mya) Raising of the Florida platform Lowering of sea levels, interruption of the Suwannee Current Infilling of the Georgia Channel with sediments derived from Appalachian/continental erosion 1. Sea level rise, lack of Suwannee current. 1. Suspended siliciclastic sediments settle over the peninsula 1. These sediments blanket the underlying limestone forming the upper confining layer for the Floridan Aquifer. Permeability: the ease with which water moves through material Surface Siliciclastics (sandy) (highly permeable) Clays and Sands (low permeability) 55 – 24 million years ago Unconfined aquifer is extensive throughout the state of Florida Low Permeability Confining Unit (poor water movement) The Floridan aquifer is a confined aquifer. The water-bearing unit is permeable limestone. Low permeability rock (confining) The Water-bearing Unit is Extremely Productive Calcium Carbonate CaCO Magnesium Carbonate MgCO 3 3 limestone How does this material hold and deliver water? Carbonate Dissolution Acid (H+) dissolves calcium carbonate Carbonates are made porous by acid dissolution Rainfall is naturally acidic Carbon dioxide dissolved in water produces carbonic acid CO + H O = H CO (carbonic acid) 2 H2 CO =2 H3 + HCO > 2 3 + Acid 3- Acidity from rainfall reacts with CaCO3 and dissolves the carbonate rock. CO + H O = H CO H CO => H +2HCO 2 2 3 CaCO3 + H = +HCO3- +- Ca2+ 2 3 3 (solid) (acid) + (solution) (solution) Dissolution Cavities Dissolution Cave Acid dissolves calcium carbonate Caves and Solution Cavities CaCO3 + H+ = HCO3- + Ca2+ Clayey Deposits Carbonates Channels and Caves Karst Topography Characterized by sinkholes, springs, depressions, lakes Sinkhole Lakes Florida is Dominated by Karst Topography Sinkhole formation depends on the material overlying the carbonate water-bearing unit Very thick clays > 200ft. Thin, sandy covering Cohesive clays up to 200ft Thick sands up to 200 ft thick and some clays Miocene clays have been eroded and shaped throughout their history resulting in extreme variability in thickness across the state. The Importance of Sinkholes and Sinkhole Lakes Hydrologic connections between the surface and the underlying limestone are maintained. Florida: Nitrates (NO3-) Nitrates do not interact significantly with soil material and can move rapidly to groundwater. What areas are particularly vulnerable? The unconfined, surficial aquifer Areas where natural groundwater recharge occurs Areas where the aquifer confining unit is thin are also particularly vulnerable. Lower Suwannee River Watershed • residential and commercial septic systems in rural areas • about 300 row crop and vegetable farms • 44 dairies with more than 25,000 animals • 150 poultry operations with more than 38 million birds Nitrates NO3 Drinking water standard: 10 ppm Groundwater Nitrate Discharge to Rivers Possible sources of nitrate in the ground water in the vicinity of the river include fertilizer, animal wastes from dairy and poultry operations, and septic-tank effluent. Flow Nitrate concentrations were higher in the measured springs than in the river. Next: Phosphorus ...
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This note was uploaded on 07/31/2011 for the course SOS 3022 taught by Professor Staff during the Fall '08 term at University of Florida.

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