Transcript Slide 1

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
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
Abundance of earthworms
– 10-1,000/m3
– 3,000 species
Benefits of earthworms
- soil fertility by producing cast
- aeration & drainage
- size & stability of soil aggregates
Soil Fungi
Yeasts, molds, mushrooms
10 - 100 billion/m2
Cell with a nuclear membrane and cell wall
Most versatile & most active in acid forest soils
Tolerate extremes in pH (bacteria do not)
Mycorrhizae symbiosis
Association between fungi & plant root
Increased SA (up to 10 times)
Increased nutrient uptake,
especially P
Mycorrhizae Fungi
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
– Endomycorrhiza
Penetrate root cell walls
agronomic cropscorn, cotton, wheat, & rice
Soil Bacteria
10-100 trillion/m2
Single-celled organisms
Rapid reproduction
Small (<5 µm)
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
– 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: CO2
– Proportional to # & biomass
Soil Organisms in Surface Soils
Organisms
Microflora
Bacteria
Actinomycetes
Fungi
Algae
#/g soil
108 -109
107 -108
105 -106
104 -105
Biomass (g/m2)
40-500
40-500
100-1,500
1-50
Fauna
Protozoa
Nematodes
Mites
Earthworms
104 -105
10 -102
1 -10
1 -10
Note those in White
2-20
1-15
1-2
10-150
Basic Classification of Organisms
Food
Oxygen
Energy Source
Based on food: live or dead
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
– Active in O2 rich environment
– Use free oxygen for metabolism
Anaerobic
– Active in O2 poor environment
– Use combined oxygen (NO3- , SO4-2)
Based on energy & C source
Autotrophic (CO2)
– Solar energy (photoautotrophs)
– Chemical reaction w/inorganic elements
N, S, & Fe (chemoautotrophs)
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 + 6H2O
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
(C6H12O6)
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 + 6O2 → 6CO2 + 6H2O
+ 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
C6H12O6 + 3NO3- + 3H2O = 6HCO3- + 3NH4+
Electron rich
Electron poor
Anaerobic respiration is less efficient
and produces less energy.
C6H12O6 + 6O2 → 6CO2 + 6H2O
C6H12O6 + 3NO3- + 3H2O = 6HCO3- + 3NH4+
C6H12O6 + 3SO42- + 3H+ = 6HCO3- + 3HS-
2880 kJ
1796 kJ
453 kJ
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
NO3-
Aerobic heterotrophs
consume oxygen
Heterotrophic Organisms
Anaerobic heterotrophs
Use nitrate instead of O2
oxygen
SO4-2
SO4-2
Anaerobic heterotrophs
Use sulfate instead of O2
HS-
C6H12O6 + 3SO42- + 3H+ = 6HCO3- + 3HS-
Organisms and Nutrients
Nitrogen
Nitrogen and Soil
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
Component of living systems
Amino acids
Proteins
Enzymes
Nucleic acids (DNA)
Chlorophyll
Strongly limiting in the Environment
Deficiency
Chlorosis – pale, yellow-green appearance primarily
in older tissues.
Excess
Enhanced vegetative growth – lodging
Over production of foliage high in N
Delayed maturity
Degraded fruit quality
N 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-NH2
Mineral:
soil N
NH4+, NO3-
Cycling in the Environment
Mineralization: Decomposition of organic forms releasing
nitrogen into the soil, generally as NH4+
Immobilization: Plant uptake of mineral nitrogen, removing
it from the soil and incorporating into plant
tissue.
Ammonium and Nitrate
Mineralization
R – NH2
NH4+
organic
mineral
Immobilization
NH4+ or NO3-
R – NH2
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
N2 + 6H2
2NH3
Fixing N2 is energetically “expensive”
N N
Triple bond
– Must use energy to break these bonds
Artificial Nitrogen Fixation
Haber - Bosch Process - Artificial Fixation of
Nitrogen Gas:
– 200 atm
– 400-500 oC
yield of 10-20%
– no oxygen
Produces 500 million tons of artificial N fertilizer per year.
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
NH4+
NO3-
NO3Negative Exchange
sites
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
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
5. Sea level rise, lack of Suwannee current.
6. Suspended siliciclastic sediments settle over the peninsula
7. These sediments blanket the underlying limestone forming
the upper confining layer for the Floridan Aquifer.
1.
2.
3.
4.
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 CaCO3
Magnesium Carbonate MgCO3
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
CO2 + H2O = H2CO3 (carbonic acid)
H2CO3 => H+ + HCO3Acid
Acidity from rainfall reacts with CaCO3
and dissolves the carbonate rock.
CO2 + H2O = H2CO3
H2CO3 => H+ + HCO3-
CaCO3 + H+ = HCO3- + Ca2+
(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