Plant Populations Flashcards
Why study plant populations
- primary producers = important to ecosystems
The different ways to study populations
- density
- distribution
- structure
- growth
What kind of info is studying plant pops aiming to find
- life cycles = aids describing populations
- influence of physical environment = how it affects growth and survival
- stresses on plants = how it affects growth and survival
Modular growth
Plants have intermediate growth and grow by adding modules
Vertical growth
Leaves, buds, twigs, branches, flowers, fruits
Horizontal growth
Clones
Genets
Produced by sexual reproduction
Ramets
Produced by asexual reproduction.
May be connected to a genet or independent
Clone
A group of ramets arising from the same gent
- all the same genotype
- usually dominant species in terrestrial ecosystems; important to plant communities
- allows physical integration ( transporting resources across ramets) = successful colonisation across wide range of habitats
Counting individual plants
Are to do if have runners/stolons or are clones
- w/ clones, genet may be very old but ramets young = ramets counted as separate individuals
Ubiquitous species
Broad, widespread range made up of many populations
Endemic species
Narrow range, containing a few populations
How can plant ranges be shifted
- global change e,g, some species expanding to cold regions, whilst others reducing distributions
- human influence e,g, transporting seeds = broken dispersal barriers
What are the different types of distribution
Random
Clumped
Uniform
Random distribution
Rare
Position of each is independent of the others
May occur in wind-dispersal
Requires uniform environment
Clumped distribution
Most common
Influenced by propagation type and environmental requirements
E.g. asexual reproduction
Uniform dispersal
No as common
Influenced by intraspecific competition due to scarcity of resources
Propagules
Vegetative structure that detaches from plant and forms new one Mostly by vectors: - biotic e.g. animals - abiotic e.g. water - other e.g. ballistic
Population structured by age
3 basic categories
- pre-reproductive
- reproductive
- post-reproductive
How to measure a plants age
- growth rings
- bud scars
- tracking through time (but may live longer than researcher)
Modular structure and asexuality can make it difficult
The Rauniker system
Alternate way of categorising population structure for plants
Via position of perennating buds in relation to ground surface
- phanerophytes
- chamaephytes
- hemi-cryptophytes
- cryptophtes
- therophytes
Phanerophytes
Dormant buds on branches which project freely into the air
Chamaephytes
Buds/short-spices on the surface of the ground or just above it
Hemi-cryptophytes
Resting buds at or near soils surface
Cryptophytes
Resting buds beneath the surface
Therophytes
Live through unfavourable season as seeds
Annuals/biennials
Often have Long-lived seed and significant seed bank
- opportunists
- their habitat changes unpredictable
Major problem with studying plant age
Seed bank in soil
- seeds can be dormant for many years
- plants may germinate at same time but aren’t from the same time
- do you factor in seed age?
The affect of competition on population structure
- older plants often exclude younger age classes
- younger trees my become larger = size cant always indicate age
- plants normally stage structured rather than age; but plant size often indicates reproductive potential
Complicated to sort out
Influences on popualtion growth
Extrinsic - density dependent - density independent Intrinsic - births and immigration - deaths and emigration
Negative density-dependence
Resource competition = plants slow growth
- increased mortality and reduced fecundity
Self thinning = progressive decline in density and increase in biomass of remaining individuals in a population
Positive density-dependence
Allele affect = increase in reproduction/survival with increasing density
May increase seed production per plant..perhaps due to increased mate availability and pollinator attraction
How life histories may affect pop growth
- variation in age and frequency of reproduction (mono or polycarpic)
- variation in offspring number and size
- R or K selected lifestyles
E.g. monocarpic bamboo
- fastest growing on the planet
- flower en-mass = whole pop at same time (not every year)
- major animal food source
- economically important to humans; building and food
- on every continent except Europe and America
- 1,500 spp
E.g. offspring number/size variation
Orchids = 1billion seeds the size of fungal spores
Vs. Sea coconut takes 6-7 years to mature + 2 to germinate. 1 seed per year produced
Grimes triangular model
Created by Philip Grime 3 strategy scheme to refine R and K selection theory for plants Split plants into either: - competitors - stress-tolerators - ruderals
Competitors in grimes triangle
Fast growing
Inhabit high fertility, low disturbance sites
Maximise captured resources
Stress tolerators in grimes triangle
Slow growing
Inhabit low fertility, low disturbance sites
Conserve captured resources
Ruderals in grimes triangle
Fast growing
Inhabit high fertility, high disturbance sites
High seed production
