sw22 - Exam Grades will be posted today. Soil Organisms...

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Unformatted text preview: Exam Grades will be posted today. Soil Organisms What creatures live in soil? 22 species Harvester Ant Colony Fauna Macro Mammals, reptiles, insects, earthworms Micro Nematodes, Protozoa, Rotifers Flora Plant roots, algae, fungi, actinomycetes (filamentous bacteria), bacteria unicellular bacteria Macrofauna: Earthworms Macrofauna: 1,000,000 per acre five pairs of hearts Mostly intestine 22 ft. long (Afr. and Aus.) 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 Casts: earthworm’s aggregates - size & stability of soilwastes Eat soil organics: 2-30 times of their own wt. Soil Fungi 10 - 100 billion/m 2 Yeasts, molds, mushrooms 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 root SA (up to 10 times) Increased nutrient uptake, Increased especially P especially 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, Mycorrhizae Fungi Mycorrhizae 1. Ions in solution 2. Movement from solution to root (diffusion) Phosphorous granule Fungal hyphae Root hair Soil Bacteria Soil 10-100 trillion/m2 Single-celled organisms Rapid reproduction Small (<5 µm) Small Mostly heterotrophic Quantification of Soil Organisms Quantification 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 Respiration: CO Respiration: CO Metabolic activity Metabolic – 2 Soil Organisms in Surface Soils Organisms Organisms Flora #/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 Bacteria Actinomycetes Fungi Algae 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 Insects, Food Source Autotrophs and Heterotrophs Autotrophs Autotrophic: produce complex organic compounds from simple inorganic molecules and an external source of energy. Organic = Carbon-containing Photoautotrophs – Plants, Algae, Cyanobacteria Produce complex organic compounds from carbon dioxide using energy from light. Primary producers – base of the food chain energy light 6CO2 + 6H O simple inorganic molecule 2 C6H12O6 + 6O2 complex organic compound Heterotrophic Organisms 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 ) 6 12 6 Heterotrophs Producers Consumers Heterotrophic Organisms Two Basic Types Related to Oxygen Status Anaerobic low-oxygen environments Anaerobic heterotrophs Aerobic high oxygen environments Aerobic heterotrophs Summary * Autotrophs store energy from the sun in carbon compounds (C6H12O6) Heterotrophs consume these complex carbon compounds for energy There are two types of heterotrophic organisms: aerobic and anaerobic Aerobic heterotrophs: high oxygen environments Anaerobic heterotrophs: low oxygen environments Extra Credit: 1. Organisms that produce complex organic compounds from simple inorganic molecules and an external source of energy are called ______________________________ 2. Organisms that live in high oxygen environments are ____ 3. Organisms that live in low oxygen environments are ____ 4. ________consume complex carbon compounds for energy 5. Detritovores eat ________ tissues 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 C H O + Oxygen = energy 6 12 6 C6H12O6 + 6O → 6CO2 + 6H2O 2 Aerobic Respiration + energy organisms The energy is obtained by exchanging electrons between carbon and oxygen. 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 Anaerobic Heterotrophic Organisms Anaerobic: Live in low-oxygen environments Heterotrophic: 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 (SO42-) Iron (Fe3+) Long term flooding can create anaerobic conditions The diffusion of oxygen in water is About 10,000 times slower than in the air Aerobic Respiration Electron poor Electron rich C6H12O6 + 6O2 → 6CO2 + 6H2O Electron rich Electron poor Anaerobic respiration C H O + 3NO3 + 3H O = 6HCO + 3NH4+ 6 12 6 2 3- Electron poor Electron rich Electron rich Electron poor Two Types of Heterotrophic Organisms Aerobic Heterotrophs Anaerobic Heterotrophs Both produce energy by transferring electrons from carbon (organic) to an electron acceptor Aerobic Heterotrophs use oxygen to accept electrons Anaerobic Heterotrophs use other elements to accept electrons e.g. Nitrogen, Sulfur, Iron eAerobic Heterotrophs C6H12O6 O2 eAnaerobic Heterotrophs C6H12O6 N S Fe Bacteria Pseudomonas, Desulfovibrio Anaerobic respiration is also slower, less efficient and produces less energy than aerobic respiration C6H12O6 + 6O2 → 6CO2 + 6H2O C H O + 3NO3- + 3H O = 6HCO + 3NH C6H12O6 + 3SO42- + 3H = 6HCO 3- + 3HS 4+ 2 6 12 6 + 3- 2880 kJ 1796 kJ 453 kJ Summary Autotrophs Store energy from the sun in carbon compounds (C6H12O6) Heterotrophs Consume these complex carbon compounds for energy Aerobic heterotrophs High oxygen environments Fast, efficient consumers Rapid decomposition of organic materials Anaerobic heterotrophs low oxygen environments Slow, inefficient consumers Slow decomposition of organic materials Accumulation of organic matter under anaerobic conditions is responsible for fossil fuels and the build-up of peat (organic matter) in wetlands. O horizon Organisms are Major Determinants of Soil and Water Quality and the Impact or Availability of Contaminants Metals (Hg, Pb, As) Nutrients (N, P) Organic Chemicals (PCBs, Dioxins) Respiration and Still Ponds O2 NO SO 3- Aerobic heterotrophs consume oxygen Heterotrophic Organisms Anaerobic heterotrophs Use nitrate instead of O 2 oxygen Anaerobic heterotrophs Use sulfate instead of O SO-2 4 4-2 HS 42- 2 C6H12O6 + 3SO + 3H+ = 6HCO3- + 3HS - Example: Eutrophication Nutrient Additions Photosynthetic life Nutrient addition increases primary productivity (algae) Sunlight is limited at greater depth Photoautotrophs die and become food for aerobic heterotrophs O2 bacteria Aerobic autotrophs consume oxygen Oxygen content in water is reduced If oxygen is reduced sufficiently, aerobic microbes cannot survive, and anaerobic microbes take over 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 organic NH4+ mineral Immobilization NH4+ or NO 3- R – NH2 Cycling of Nitrogen R-NH2 is organically bound form of nitrogen N2 X Decomposition Of O.M. R-NH2 Uptake by plant Uptake by plant NH4+ nitrosomonas NO2- nitrobacter NO3- NH4+ is exchangeable, NO3- is not Atmospheric Nitrogen Fixation Forms of Nitrogen R-NH2 is organically bound form of nitrogen N2 X Decomposition Of O.M. R-NH2 Uptake by plant Uptake by plant NH4+ nitrosomonas NO2- nitrobacter NO3- NH4+ is exchangeable, NO3- is not 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- NO 3- Negative Exchange sites Loss of Productivity Leaching to groundwater, surface water 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 Next: Phosphorus ...
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This note was uploaded on 02/04/2011 for the course SWS 3022 taught by Professor Bonczek during the Spring '11 term at University of Florida.

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