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 yearsWithin 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?

• Directional change – Succession• Definition• Examples• Models of succession• Relationships between species• The climax community

• Cyclical change – Patch dynamics• 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?

Seedling density differences (gopher - field)

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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 richness-Gradients 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 ←─→ DTolerance

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.orgE-mail : sylv@tiem.utk.edu

Overview

• 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

H0

H1

H2

Hn

P0

P1

P2

Pn

…