final exam Flashcards
limits to plant distribution
(1) biogeographic
(2) physiological
(3) ecological limits
OR
historical –> does it arrive?
physiological –> can it germinate, grow, survive and reproduce?
biotic –> does it successfully compete and defend itself?
historical limits to plant distribution
is explained by millions of years of evolution in the context of factors such as climate change and continental drift
- explains coefficient of biotic similarity: “shared plant families” found between different regions
- floral kingdom
floral kingdom
a large geographic area with a relatively uniform composition of plant species
- floristic kingdoms: a high degree of family endemism
- floristic regions by a high degree of generic endemism
- floristic provinces by a high degree of species endemism
physiological limits to plant distribution
biomes show a strong latitudinal distribution
- reflects climate and soils/topography
- use climate to predict the vegetation zones/biomes (like in world veg)
1. Holdridge (triangle with potential evapotranspiration ratio, humidity provinces, and annual precipitation)
2. Whittaker (average temperature v annual precipitation)
Raunkier’s Classification
based on position of perennating (dormant) buds
(a) Phanerophytes: buds on exposed branch tips such as trees –> high in mild, moist environments
(b) Chamaeohytes: buds close to ground, protected by snow –> environments with snow cover
(c) Hemicryptophytes: buds at soil level, protected by dieback –> moist, temperate regions
(d) Cryptophytes: bulbs, rhizomes, corms, etc. protected by soil –> extreme cold or drought
(e) Therophytes: seeds –> deserts
biotic limits
competition (biotic limits) explains why species adapted to environmental extremes often occur only in stressful environments and not mesic environments , e.g., xerophytes occur only in deserts
plant communities
an assemblage of plant species that interact among themselves and with their environment within a space-time boundary
they have:
- a relatively consistent floristic composition
- uniform physiognomy
- a distribution that is characteristic of a particular habitat
california coastal prairie
characteristic species of this community include
- perennial bunch grasses
- danthonia
- festuca
- calamagrostis
- hordeum
- etc
organismic view
closed
- communities are clearly defined with sharp boundaries, indicator species, and distinct interactions
continuum concept
open
- ecotones tend to be “soft”, with overlap between communities across the ecotone
- distributions of plant species tend to be independent of one another
ecotones
- a transition area between two biological communities, where two communities meet and integrate
-are often caused by underlying environmental gradients
species interactions
can be random, positive, or negative
species interactions – positive
some clumping may be due to underlying pattern of resources, or it may reflect a positive association
- commensalism
- mutualism
plant growth simulation
- new plants develop while existing plants grow
- at some points, the plants have to fight for limited resources (water, light, soil)
- weak plants get dominated by strong ones and eventually die
- number of plants decreases with dominant plants growing
commensalism
an association between two organisms in which one benefits and the other derives neither benefit nor harm
-EPIPHYTES; occurs between small plants called epiphytes and the large tree branches on which they grow. depend on their hosts for structural support but do not derive nourishment from them or harm them in any way
- NURSE PLANT SYNDROME; takes place when plant species shelter seedlings, young and/or adult individuals of other species though their ontogeny
- HYDRAULIC REDISTRIBUTION (LIFT); the passive movement of water via roots from regions of wetter soil to regions of dryer soil, including the lifting of water from the deeper to shallower soil layers
mutualisms
-lichens
- mycorrhizae; fungi that have a symbiotic relationship with the roots of many plants, they enhance nutrient and water uptake of the host plant
- nitrogen-fixing bacteria
- pollination
- zoochory; the dispersal of plants (seeds) by animals , can be via getting stuck to fur or pooping it out lol
-myrmecophytes ; have structural adaptations to their rhizomes, leaves, and stems that provide ants with food and shelter, and in return ants assist them with nutrition, defense, and seed dispersal
species interactions - negative
- herbivory
- competition
herbivory
consumption of all or part of a plant by a consumer
- consumers: parasitic microbes or plants, grazing and browsing animals
considered negative because of biomass loss, however, may be positive when it involves pollination, dispersal, and germination
- 10 to 100% (seeds) lost to herbivory
- plants defenses against herbivory have an energetic cost
competition
results in mutually adverse effects to organisms that utilize a common resource in short supply
- ex. larrea and ambrosia in Mojave Desert
MECHANISM;
(1) resource based (passive) competition alters the availability of a limiting resource with greater or lesser effects on a given species –> Ambrosia affected more than Larrea
(2) non-resource based –> allelopathy –> the chemical inhibitor of one plant (or other organism) by another, due to the release into the environment of substances acting as germination or growth inhibitors
Ambrosia v. Larrea
Ambrosia root systems appear capable of detecting and avoiding other Ambrosia root systems, whereas Larrea roots inhibit Larrea and Ambrosia: activated charcoal suggests Larrea effect mediate by release of a chemical compound, but Ambrosia infraspecific interaction resource based
changes in communities
- disturbance –> sudden stochastic events
- succession –> 1-500 years
- climate change –> 1000’s years
- evolution –> millions of years
disturbances
accidentally injuries that reduce biomass and competitive ability
- processes leading to bare ground (unseats the occupier)
- can fall into two categories
(1) adaptations that allow a plant to resist disturbance (and keep their site)
(2) attributes that enhance the probability of colonizing a new microsite
intermediate disturbance hypothesis
- can support both k and r selected species if disturbance is not too several or too little
k- selected= exhibit logistic growth, have longer life spans , does well with low disturbance
r-selected= short life spans, exponential growth, does well with high disturbance
succession
directional cumulative change in species that occupy a given area through time
-types: primary, secondary, autogenic, allogenic, progressive, retrogressive, directional, cyclic
primary succession
occurs on land not previously vegetated
- barren area
- initiated due to a biological or any other external factors
- no soil, while primary succession starts
- pioneer species come from outside environment
- it takes more time to complete
secondary succession
occurs in previously vegetated areas that have been disturbed
- starts due to external factors only
- it starts where soil covers is already present
- pioneer species develop from existing environment
- it takes comparatively less time to complete
autogenic succession
driven by the effect of the plants on their habitat
- biotic factors
- secondary succession starts with autogenic succession
allogenic succession
driven by major environmental change: changing external geophysical processes
- abiotic factors –> outside influence, not within the existing community itself
- primary succession starts with allogenic succession and proceeds to autogenic succession
progressive succession
increase community complexity, results in mesic habitats (a type of habitat with a well balanced or moderate supply of moisture throughout the growing season)
- example would be secondary succession
retrogressive succession
decreases community complexity, results in more extreme habitats
- example would be ecosystem retrogression
directional succession
cyclic succession
successional changes on a very local scale
transition matrices
-use column vectors to represent current stage
- use transition matrix for transition probabilities
- matrix multiplication predicts future population
CAUTIONARY NOTES
- Markoff Modelling– are such assumptions valid?
- if model too simple– ignores important life history differences
- best models reasonably complex and involve studies over time