Plant Ecology

1
Plant Ecology

• Definition study of the distribution and
  abundance of plants and the factors (biotic and
  environmental) that controls this.
• Individual
• Population
• Community
• Ecosystem

2
Why study plant ecology?
3
Why is plant ecology different from animal ecology
Plants are sessile
4
Consequence of being sessile
Cant escape predators Toxins, spines, grasses
hide meristems
5
Consequence of being sessile

• Cant migrate in bad weather
• Leaf deciduousness, seed dormancy, overwinter
  below ground

6
Consequence of being sessile

• Need special adaptations to move seeds and pollen
• Seeds have wings, parachutes, or berries
  dispersed by animals
• Pollen-wind dispersed or animal dispersed

7
Consequence of being sessile

• Interact primarily with neighbors
• Compete for resources locally, therefore, concept
  of density may not be appropriate
• Matings take place between neighbors

8
Consequence of being sessile

• Spatial structure of populations is very
  important
• Affects competitive relationships, and
  mutualistic relationships
• Affects the genetic structure of the population

9
Why is plant ecology different than animal ecology

• Plants exhibit indeterminate growth
• All plants grow from meristems,
• the position of the meristem determines the
  morphology of the plant
• E.g. Strawberry,grass tillers

10
Definitions

• Meristem- the growing point of the plant
• A region in which undifferentiated cells divide
• Genet- refers to genetically distinct
  individuals, (i.e. all of the parts arise from
  the same seed)
• Ramet-a part of the genet, (i.e., one tiller of a
  grass)

11
Why is plant ecology different than animal ecology

• Plants exhibit plastic growth
• Examplesplants growing in dry conditions may
  allocate more biomass to roots than shoots
  plants growing in wet conditions produce more
  arenchyma cells

12
Why?

• This flexible growth arises from their modular
  construction
• Phenotypic plasticity- plants can change their
  growth form in response to environmental
  conditions

13
How are plants similar to animals

• Plants exhibit behavior

14
How are plants similar to animals

• Plants exhibit behavior
• Movement in response to some kind of change in
  the plants environment
• E.g. sensitive plant Mimosa pudica
• Tropical liana or vine, Ipomea phillomega grows
  towards gaps
• Response to light determined by phytochrome

15
Individuals

• Why study individuals?
• Individuals exhibit different physiological
  tolerances
• Determine plant distribution in the environment

16
Individuals

• Why study individuals?
• Individuals have different competitive abilities
• Determine plant distribution in the environment

17
Individuals

• Why study individuals?
• Individuals have different genetic composition,
  which determines their ability of their offspring
  to tolerate different environmental conditions
• Determine plant distribution in the environment

18
Individuals

• Variation among individuals
• Important
• Population dynamics- community and ecosystems
• Evolution
• Change in the phenotypic characteristics of a
  population or species over time

19
Individual traits can determine where plants
occur in the environment

• Physiological tolerances
• Biotic interactions
• Evolutionary constraints

20
Life History of a plant
21
Life History of a plant

• Life History describes the typical
  characteristics of a species, particularly the
  characteristics related to reproduction
• how long a plant lives, how long it takes to
  reach reproductive size, how often it reproduces
• Examples annual, biennial, perennials
• Extreme examples, Monocarpic plants, live many
  years, reproduce once and die
• bamboo

22
Life History of a plant

• how long a plant lives, how long it takes to
  reach reproductive size, how often it reproduces
• Examples annual, biennial, perennials
• Extreme examples, Monocarpic plants, live many
  years, reproduce once and die
• Bamboo, yucca plants

23
Environmental Controls of species distributions

• The law of the minimum- the factor in shortest
  supply will limit growth the most
• Water, light, nutrients, micronutrients
• Problems with this idea
• Excess supply of a factor can be toxic
• Factors may be substitutable

24
Environmental Controls of species distributions

• Physiological Tolerance Model
• The range of habitats for a given species is the
  sum of tolerance limits for each environmental
  factor.

Soil nitrogen
Soil pH
Light intensity
Frost free
Potential habitat
25
Environmental Controls of species distributions

• Problems with this model
• Assumes that environmental factors limit plant
  distribution and ignores biotic factors such as
  competition
• Physiological tolerances may change when plants
  are grown together and are competing

26
Relative growth
pH
pH
Pure culture
Mixed culture
Physiological tolerance can shift when plants are
grown in competition
27
Environmental Controls of species distributions

• Physiological range-potential range of a species
• Physiological optimum-optimal conditions for a
  species
• Ecological range- observed range when grown under
  natural conditions
• Ecological optimum-observed optimum when grown
  under natural conditions

28
What is a species?

• Definition of species
• (A) Typological species-defined through reference
  to a type specimen
• (B) Morphological species-defined through shared
  traits
• Flower structure,leaf shape, chromosome number,
  biochemical pathways, similarity of DNA sequences
• (C) Biological species-members of a group of
  populations that interbreed or potentially
  interbreed with each other and produce viable
  offspring