Transcript Cowels - Prairie Ecosystems / FrontPage

Cowels
Ecological Relations of the
vegetation on the sand dunes of
Lake Michigan (1899)
• Plant Formations should be found that are
rapidly changing to another type by means
of changing environment.
• Can be seen in no better place than Sand
Dunes due to instability..
• Plant Society – product of past and
present environmental conditions
• Plant Formations are investigated
– species composition
• The progressive changes that take place
and the factors in the environment which
caused these changes.
Ecological Factors
• Light and Heat
– Open exposed to extremes
• Wind
– From the North west, Michigan City dunes most
affected
• Soil
– Quartz sand, deplete of organic material
• Water
– Holding capacity of sand
• Other factors
– Fire, topography, other animals and plants
Plant Societies
• Beach
– Lower, middle, upper
• Embroyonic or Stationary Beach Dunes
– Rapid growth, slow growth
• Active or Wandering Dune Complex
– Transformation
– Physical and Biological features
– Encroachment
– Capture (by vegetation)
Plant Societies of Chicago and
Vicinity (1901)
Plant Succession: An analysis of the
development of Vegetation (1916)
• “Treats the formation as an organism with
structures and functions like an individual
plant…. The formation is defined as the climax
community of a natural area where the essential
climatic [habitat] relations are similar or identical”
• “sere” - term used to describe the entire
successional series, eg developmental process
• [Thus succession is development of a formation
with infant, child, juvenile, and adult phases. But
that can revert to earlier phases and start again.]
– Clements 1919 comprehensive review
Primary Succession after Glacial
Retreat
Bare glacial till 
Mosses, willow, dryas, fireweed, cottonwood in
the first 1 to 10 years
Within 10 years, sites are invaded by alder which
forms a dense thicket up to 9 m tall in about 50 years
Sites invaded by Sitka spruce, which after
another 120 years form a dense forest
These forests are invaded by hemlock, which
forms a climax spruce-hemlock forest after another
80 years in well drained sites
Form sphagnum bogs or muskeg in poorly
drained sites
Changes in site conditions
during succession after glaciers
• Decrease in soil pH
• Increases in soil nitrogen with alder
• Decreases in soil nitrogen after alder is
absent
• Water logging and acidification of soils in
areas invaded by sphagnum
Reduction in soil drainage
• Addition of dead organic matter into the soil
matrix reduces soil drainage
• In some sites, this leads to an increase of soil
moisture over time
• Moss invades mature spruce/hemlock forests –
produces more organic matter that reduces soil
drainage  creates highly acidic soils
• In poorly drained sites, soils become permanently
saturated – trees die out and bogs are formed
Lake Michigan sand dunes
Key Issues for Community Change
1. What factors result or cause changes in
the community?
2. Are community changes predictable?
3. What types of changes are occurring?
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Directional change – Succession
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Definition
Examples
Models of succession
Relationships between species
The climax community
Cyclical change – Patch dynamics
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Examples
In a climax community, how
does a community maintain
its species composition?
• Gap dynamics – the process by which
space created by a dying canopy tree is
occupied by trees growing in the
understory
• In a stable climax community, the
species growing in the understory are
similar to those growing in the canopy
Four stages in the heath community life cycle
Do certain plant species require
small scale disturbances like gopher
mounds to propagate?
Density
(gopher - field)
Species
Hedhi
Sornu
Crete
Poapr
Erica
Digis
Ambar
15
10
5
0
-5
-10
-15
Molve
Setgl
Polco
Lycal
Chele
Schsc
Berin
Lepde
Andge
Erasp
Oxast
Seedling density differences
(gopher - field)
Conclusions
• Gophers do have significant effects on plant
communities
– Effects on succession
– Pre-agriculture role
• Prairie restoration
The Next Step:
• Continue analysis of data
• Long term project--Add gophers to part of a gopher
free field and observe effects
Spatial gradients of sp richnessGradients with altitude and depth
• Terrestrial environment:
– altitude incr, S decr (fig 10.21)
• Aquatic environment:
– depth incr, S decr (fig 10.22)
10.21
Temporal gradients of sp richness
-- in a community (succession)
• Along a succession course
– Hump curve predicted as model,
– confirmed by plants succession
– But, few studies on animals… fig 10.23
10.23
Simple model, d
Mechanisms of succession
-- Connell-Slatyer Model
• Facilitation: pioneering sp modify the physical
env in such a way as to facilitate colonization by
later succession sp.
• Tolerance: one sp makes env less fit for its
offspring although other sp are able to colonize
and reproduce. replacement of early sp with
others
• Inhibition: the early colonizer inhibit further
colonization of the length of their life spans
Facilitation
A─→B─→C─→D
Inhibition
A ←─→ B
C ←─→ D
Tolerance
A─→B─→C─→D
The nature of the climax
• Definition: the final, self-perpetuating stage in a
successional sequence.
• monoclimax, single regional climax, Clements
(1916,1936),
• polyclimax: Tansley (1939), a series of local climax
states, determined by local soil and microclimate
conditions, edaphic climax
• Pattern climax: mosaic of local edaphic climaxs
that merge gradually into one another
The ATLSS Vegetative Succession
Model
Scott M. Duke-Sylvester
ATLSS Project : University of Tennessee
Project web-site : www.atlss.org
E-mail : [email protected]
Overview
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Purpose of the model
Application to restoration planning
Model description
Calibration/validation
Development/delivery schedule
Availability
Purpose of the vegetative
succession model
• Provide vegetative succession dynamics
• Modeling changes to habitat is important
for accurate modeling of higher trophic
levels
• A rigorous succession model would
include process dynamics : Everglades
Landscape Model (ELM)
• The ATLSS objective is to interface with
ELM, but also produce a alternative less
complex succession model.
Application to restoration
planning
• Provides another tool for assessing the
potential for change due to alternative
hydrologic scenarios
– Directly through changes in habitat diversity
and structure
• Diversity : number of species, evenness
• Structure : tree islands
– Indirectly by providing a changing habitat for
other models
Model features
• Time step : 1 year
• Spatial scale : 500x500 meters
– Possibly finer if computationally feasible
• 58 habitat types (FGAP 6.6)
• Stochastic process influenced by local
environmental processes
Model response
• The model will simulate succession
dynamics in response to a number of
environmental processes
– Hydrologic disturbance : hydroperiod
– Nutrient disturbance : phosphorus
– Fire disturbance
• Response to disturbance is habitat type
specific
Model description
• Space is broken into a set of discrete cells
• Cell model
– Starts with a habitat type: H0
– Set of alternative habitat types : H1 .. Hn
– Transition probabilities from H0 to H0 .. Hn : P0
.. Pn
– P0 .. Pn depend on the current environmental
conditions
• Cell model replicated in each discrete cell
Cell Model
• Allows for changes in cell habitat type
• Allows for changes in transition
probabilities in response to changing
environmental conditions
• Order of events:
– Update current transition probabilities in
response to environmental change
– Determine the new habitat type for the cell
Change in cell state
P0
H0
P1
P2
H2
…
Pn
H1
Hn