1. Chapter 26 & 27 Plant Ecology

2. Why Ecology?
Ecology - study of organisms in relationship to all aspects of their surroundings – Biotic-Biotic, and Biotic-Abiotic interactions
We must try to understand plant traits as adaptations to habitat – ecological selection, co-evolution etc. – therefore systems biology
An individual or even a population does not exist in isolation, but coexists with numerous populations of other plant, animal, fungi, protist, and prokaryote spp. – communities, ecosystems
Therefore, ECOLOGY – let’s focus on population, community and Ecosystem

3. Populations
Intraspecific (within population) and interspecific interactions
(between populations)
Intraspecific – plant interference or exploitation in resource use
Population growth models – Exponential vs. Logistic

4. have both intraspecific and interspecific interactions
Communities
have both intraspecific and interspecific interactions
Species with r-and K-Selection - r-selected spp. can occur next to ones that are K-selected

5. Mutualistic symbiosis as a community interaction
Ectomycorrhizae – with Ascomycota & Basidiomycota; Endomycorrhizae – with Glomeromycota

6. Biological N fixation
Rhizobium spp. with many members of
Fabaceae and
few members of other plant families
N Cycle
N fixation
Nitrification
Assimilation
Ammonification
Denitrification

7. Community Succession and Climax
Community development thru
a series of stages of distinct
community structures in a
given area
Pioneer community to climax
community
Primary succession (no soil at
the beginning) Vs secondary
succession (following
disturbance)
Climax is not static but stable,
self-sustaining and tolerant in
Its environment – discuss
three panels in figure on left

8. Community Succession
The first plants that invade a new soil, called pioneers, must tolerate severe conditions
Pioneer plants often are associated with nitrogen-fixing prokaryotes
As pioneers live on soil, they change it significantly

9. Ecosystems
Structure physical size and shape of organisms and their distribution in relation to each other and physical environment constitute the physiognomic structure

10. Changes that an ecosystem undergoes with time = temporal structure
Time span can be as short as a day or can encompass seasons or decades
Plants change dramatically with season, as do other organisms
In tropical ecosystems, winter and summer do not exist, but an alternation of dry and wet seasons governs ecosystem change

11. Ecosystems: Species Composition
Species composition refers to the number and diversity of species that coexist in an ecosystem – affected by resources

12. Ecosystems: Species Composition
Stressful climates with poor soils support a low number of species because so few species are adapted to such conditions

13. Ecosystems: Species Composition
Mild climates and rich soils support an abundance of species because most plants have tolerance ranges that include such climatic and soil conditions
Globally – light, water and nutrients – most crucial determinants of species composition and productivity

14. Ecosystem Productivity and Trophic Levels
Trophic levels are feeding levels
As plants photosynthesize, energy and carbon compounds enter the ecosystem
As plants are eaten, their energy and carbon compounds move to the herbivore trophic level, then to the carnivore trophic level – decomposers (detritivores) get energy from all levels (energy flow and carbon flow)
At each step, much of the food is used in respiration (R), resulting in the production of ATP, heat, carbon dioxide, and water
Only ~ 10% goes to next upper level
NPP = GPP - R

15. Trophic Levels
Show omnivores

16. Trophic Levels
Movement of energy and biomass from one trophic level to the next is often represented as a pyramid of energy or a pyramid of biomass
Pyramids of biomass and numbers have become important as a means of illustrating the impact of the human introduction of herbicides, pesticides, and toxic wastes; toxins concentrate as they move up the food chain - biomagnification
Role of decomposers in the ecosystem is vital - if there were no decomposers in nature, plants could grow only as rapidly as weathering breaks down rock

17. Trophic Levels

18. Biomes Biome video – 16 min – Follow biomes
Large relatively distinct terrestrial region/ecosystems with characteristic/same
climate, soil, vegetation and animals irrespective of location
Biome video – 16 min – Follow biomes

19. Plants and Climate Change
Greenhouse effect and global warming
C cycle - atmospheric CO2 enrichment – Northern winter vs summer – human activity
Green corridors – plants and biodiversity
Plants for both minimizing the harmful environmental change and tolerating the damage by it