1. BIOLOGY 403: PRINCIPLES OF ECOLOGY (Communities, Succession, Biomes)

2. COMMUNITIES DEFINITION
a community is a unit composed of two or more interacting species in a given area
Communities have boundaries in space and time.
How many communities are there on the earth?
One ???
Millions ???
Ecotone
zone between communities where composition very rapidly changes from that typical of one community to that typical of the other

3. ECOTONE A ‘pressure’ zone (an intermediate / intergrading area)
May be narrow or wide
May have larger flora / fauna than adjacent communities --- WHY ???
May have species unique to it

4. EMERGING CHARACTERISTICS IN COMMUNITIES
Dominant (= Keystone) Species / Subordinant Species
Stratification (= Layering)
Phenology (rhythmic seasonal patterns)
Succession
a non-cyclic process in which species / communities in a particular area are replaced by other species / communities over time (the ‘life history’ of a community)
Sociability --- the + or – affinity one species has for another

5. ECOLOGICAL SUCCESSION (I)

6. ECOLOGICAL SUCCESSION (II)

7. ECOLOGICAL SUCCESSION (III)

8. ECOLOGICAL SUCCESSION (III)
What causes it?
Organisms and the changes they create are the driving force.
Types of Succession
Primary
occurs on a primary bare area
Secondary
occurs on a secondary bare area

9. ECOLOGICAL SUCCESSION (IV)
Sere - the whole sequence of communities in a particular succession (Xerosere, Mesosere, Hydrosere) OFTEN: X  M  H
Pioneer (species of community)
the first species to invade an area
Seral (species or community)
those which occupy intermediate positions in a succession (early, mid, late, etc.)
Climax (species or community)
those occupying the final position in a succession (Monoclimax or Polyclimax ?????)

10. CLIMAX COMMUNITIES (I)
DEFINITION: dynamic steady state community whose characteristics are determined by the characteristics of its habitat / environment
Primary Climax
do not depend on recurrent disturbances by fire or animals to maintain floristic / faunal composition
Climatic Climax --- on normal soils, with average topography, and thus only the macroclimatic conditions are controlling it.
Edaphic Climax --- develops differently from what one expects for the macroclimatic conditions due to an unusual soil
Topographic Climax --- develops differently from others in the same region due to a distinctive microclimate

11. CLIMAX COMMUNITIES (II)
Disclimax
all climaxes that maintain their floral / faunal composition only as a result of persistent disturbances of the same kind, frequency and intensity
- Fire
NJ Pine Barrens
Some Grasslands
- Zootic

12. TRENDS DURING SUCCESSION (I)
Stage in Ecosystem Development Attribute Young Mature
Biomass low high
Trophic Relationships simple complex
Food Chains short, grazing long, detritus
Food Webs simple complex
Stratification less more
Species Diversity low high
Niche Specialization broad narrow
Feeding Relations general specialized
Life Cycles short, simple long, complex
Population Control Mechanisms physical biological

13. TRENDS DURING SUCCESSION (II)
Stage in Ecosystem Development Attribute Young Mature
Fluctuations greater lesser
Stability low high
Potential Yield to Humans high low
Net Community Production higher lower (0 ??)
Community Respiration lower higher
Community P / R Ratio P > R P = R

14. PHYSIOGNOMIC TYPES OF VEGETATION (I)
Physiognamy --- landscape appearance due to occupying vegetation type(s)
Forest --- tall trees covering the area densely and uniformly (needle-leaved, broadleaved evergreen, broadleaved deciduous; OPEN vs. CLOSED)
Woodland when trees are of a lower stature
Gallery forest or woodland --- in a strip along stream courses (subdivided as in forest)

15. PHYSIOGNOMIC TYPES OF VEGETATION (II)
Savanna --- singly scattered trees or shrubs over a more continuous phase of low vegetation
Groveland --- clusters of trees or shrubs scattered over a more continuous phase of low vegetation
Parkland --- ‘islands’ of low vegetation (the PARKS) interspersed in a more continuous phase of forest

16. PHYSIOGNOMIC TYPES OF VEGETATION (III)
Scrub (Shrub) area covered by lower growing woody vegetation (subdivided as in forest)
Grassland --- herbs are the dominant vegetation
Steppe --- xerophytic herblands (usually dominated by narrow- leaved grasses)
Meadow --- Mesophytic herblands (usually dominated by broader-leaved grasses and forbs)
Shrub-Steppe --- mixture of low shrubs and grasses sharing dominance in an arid area

17. BIOMES
DEFINITION
a large area, on land, characterized by certain dominant climax plant species
why characterized by the plants instead of animals????????
The major Biomes
see class handout for their names and the conditions causing them

18. TEMPERATURE, MOISTURE AND BIOMES

19. BIOMES OF THE WORLD

20. LATITUDE, ALTITUDE & BIOMES

21. N. & S. AMERICAN BIOMES

22. DESERTS OF THE WORLD

23. GRASSLANDS AND THEIR ORGANISMS