Transcript SectetsOfSoil - Prairie Ecosystems

Fire (continued)
• Chicago Wilderness
– Passing the Drip torch
In healthy woods and savannas,
representatives of every age—
seedlings, saplings, teenagers, and
adults
one community
of “pioneer
plants” prepares
the way
the growth of the
next generation
of oaks as
“recruitment”
http://www.chicagowildernessmag.org/issues/spring2007/editorsessay.html
Healthy burns in the arboretum
• Burns over large areas
• Rotation of a 4-year burn schedule
• Adjacent to areas not burned in the last
2 years
• Seasonal rotation of burns
The dry Plains were provided the perfect conditions for
fires to start. The long hot summers left the Prairie
Grass and the homesteaders’ crops bone dry.
Accidental fires started by a spark or a bit of broken
glass lying on the ground and reflecting the sun were a
disaster for the homesteaders.
Unless the fire could be stopped quickly by beating, it
soon spread. Without any water to put out the fire, the
homesteaders were forced to hide in their sod houses
until their crops were destroyed and the fire died.
Canopy fire
Hot (300-400 F)
Widespread mortality
Strongly linked to fire weather
Potentially large spatial scale
Dominant vegetation removed
Yellowstone National Park,
1988
Tallgrass prairie, Kansas
Surface fires
Grasses regenerate because growth tissues are underground
Seedlings and saplings killed; adult trees spared
Lower temperature than canopy fires
Tall and short grass prairie
http://climate.konza.ksu.edu/
Tall and short grass prairie
• Disturbance agents: fire and drought, and historical grazing from
bison.
• 5-10 yr return intervals for tall grass prairie
• Fires removes litter (or duff) and woody shrubs
• Perennial grasses have greater seed production and germination
rates following fire
• Trees found on the eastern sides of rivers because of prevailing
westerly winds.
• Mowing is not a good replacement for fires, as it does not remove
the litter. Grazing by domestic cattle is not a good replacement as it
exerts a selective pressure on only a few species.
• Burning is required for the restoration and maintenance of prairie
reserves
Is fire carbon Negative?
Other physical effects of fire
Creates environmental heterogeneity
Promotes species coexistence, particularly between early and late successional
species
•
Cerro Grande fire in New Mexico, 2000
– Controlled burn escapes and destroys
homes in Los Alamos
•
Biscuit fire in southern Oregon, 2002
– Lightning-ignited fire burns
uncontrollably over wide area and burns
national forests and homes in local
communities
•
Esperanza fire in southern California,
2006
– Arsonist starts fire at suburban-wildland
interface in southern California
• 1990’s-2006: increased
pressure to suppress fire and
thin forests in response to
uncontrollable natural wildfires,
escape of controlled burns,
and a growing population at
the suburban-wildland
interface.
• The recent Healthy Forests
Restoration Act advocates
salvage logging after fires to
pre-emptively thin them
• In-class short readings 2-4
Secrets of the Soil
Chapter 4
Justin Borevitz
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Fungal, bacterial, insect, nematodes
Water Bear, Spring Tails
Nitrogen Fixing
Allelopathy
Soil Microbe diversity
A multi-disciplinary approach to
research in soil related ecosystem
services
Soil ecology
Soil science
Environmental economics
Resource economics
Soil Biodiversity
Ecosystem functions
Soil processes
Ecosystem services
for human welfare
Soil Organisms
Sociology
soil biology - microbiology
Let me start with a
challenge to soil
science to
Political sciences
http://www.fao.org/ag/AGL/agll/soilbiod/default.stm
KEY FUNCTIONAL GROUPS
OF SOIL BIOTA
Legume
Maize
Micro-symbionts
mycorrhizal
Fungi
Macrofauna
(Ecosystem Engineers)
– Earthworms
– Termites
Source Swift (2002)
Decomposers
e.g. cellulose degraders
N-fixing
Bacteria
Microregulators
Nematodes
Pests and
Diseases
e.g. fungi, invertebrates
C&N transformers
e.g.methanogens
& nitrifiers
What do fungi “eat?”
• Decomposers break down complex
molecules into sugars or consume
sugars found in environment
• Symbiotic fungi receive their energy
(carbohydrates) directly from a plant or
algal partner
Examples:
• mycorrhizal fungi (live on plant roots)
• lichens (contain algae)
Briana Timmerman [email protected]
What else do fungi “eat?”
• Predatory fungi, catch
and digest other
organisms (like
nematodes)
But still absorptive nutrition! Just have to catch it first…
Briana Timmerman [email protected]
Lichens
Briana Timmerman [email protected]
Mycorrhiza symbosis
• A mycorrhiza (Greek for fungus roots) is
the result of a mutualistic association
between a fungus and a plant. This
mutualism takes place at the root level,
where individual hyphae extending from
the mycelium of a fungus colonize the
roots of a host plant, either intracellularly
or extracellularly
• Transport P, K from great distances
• Extend the root system
• Trade Minerals for sugars..
95% of all
plant families
are
predominantly
mycorrhizal
An ericoid mycorrhizal fungus isolated from Woollsia pungens [2].
Midgley, DJ, Chambers, SM & Cairney, JWG. 2002.. Australian Journal of Botany 50, 559-565
Mycorrhizae
• “myco” = fungus and “rhiza” = root
• Symbiotic association between
plant roots and fungi
• Several different types of association
(defined by structure of fungus:plant
interface)
Briana Timmerman [email protected]
Fungi can access more of the soil
because
1. Hyphae are smaller than plant roots
Root Hair
Hyphae are
1/500th the
diameter of a
plant root
hair
hyphae
Briana Timmerman [email protected]
and fungi expand the surface area
available for nutrient uptake
Briana Timmerman [email protected]
These connections can form
forest-wide networks!
•If mycorrhizae can move significant amounts of
carbon (sugar) between different plant species,
this could reduce competition and contribute to
the stability and diversity of ecosystems.
Briana Timmerman [email protected]
Biological Nitrogen Fixation (BNF)
• Plant receives ‘reduced’
nitrogen
• Bacteria receives
energy and other
nutrients
Root nodules
Nitrogen fixation is the process by which atmospheric
nitrogen gas is converted into ammonia. The ammonia is
subsequently available for many important biological
molecules such as amino acids, proteins, vitamins, and
nucleic acids. The reaction can be presented as follows:
N2 + 16 ATP + 8e- + 8H+ -> 2NH3 + 16 ADP + 16 Pi + H2
Biological Nitrogen Fixation (BNF)
• Infection, nodule development, and fixation
occurs when:
Proper match occurs (strain specific)
Surface chemistry conditions are met (Ca++, NO3levels)
Bacteroid is formed capable of fixing N2
Synthesize nitrogenase
Jointly with plant synthesize leghemoglobin
N2 is reduced to NH3
NH3 is attached to glutamate
Amino acid is made or transported as glutamine
or ureide
allelopathy
• denotes the production of specific
biomolecules by one plant that can harm,
or give benefit to, another plant. However,
it is most commonly used in the former
sense - an interaction in which one plant
causes suffering to another plant
• Competition or toxicity
• Direct or through microrhyzhoa
• Some plants that use allelopathy are
black walnut trees, sunflowers,
wormwoods, sagebrushes, trees of
heaven
• Pine trees, Eucalyptus
In 1 teaspoon of agricultural soil there are…
 Bacteria
100 million to 1 billion
 Fungi
6-9 ft fungal strands put end to end
 Protozoa
Several thousand flagellates & amoeba
One to several hundred ciliates
 Nematodes 10 to 20 bacterial feeders and a few fungal feeders
 Arthropods
Up to 100
 Earthworms
5 or more
Mary Barbercheck Dept. of Entomology
Penn State University
Soil Health Indicator
Some Factors Affected by Tillage
• Soil Moisture
• Soil Temperature
• Range of Temperature
and Moisture
Fluctuations
• Surface Residue
• Soil Fauna Abundance
and Diversity
• Plant Diversity
• Favors Bacteria > Fungi
Tilled
No Till
Bacterial-based
Fungal-based
Soil Health Indicator
Predatory Arthropods (0.0001x)
Predatory Arthropods (0.01x)
Predators of BFN (0.001x)
BF Nemas (0.01x)
FF Invertebrates (0.1x)
Protozoa (0.1x)
Bacteria (x)
•
•
•
Fungi (x)
Densities are much lower than in unmanaged systems, regardless of
level and types of inputs
Favors bacteria over fungi
(After Moldenke, 2002)
Soil arthropods tend to consume fungi
Effects of Cover Crop Rye Management
in Reduced Tillage Corn
Clark et al. 1993. J. Entomol. Sci. 28: 404-416
Mean Number
Roll
Paraquat
6
5
a
Remove
Fallow/Disk
a
a
a
4
aa
3
ab
bb
2
1
b
b
b
0
ae
ae
e
lid
a
id
el
hi
n
ci
p
ny
id
in
e
ae
id
l
hy
a
id
s
co
ap
oc
C
Li
Ly
St
ab
ar
C
Ave. #/Core
Systems Experiment 1999-2002
Microarthropods Cumulative Average
180
160
140
120
100
80
60
40
20
0
Other
Coll.
Mites
Pasture BMP
CT
Trees
BMP
NT
Old Organic
Field
Barbercheck, unpubl.