Lecture 16: Facilitation in extreme environments Flashcards
facilitation:
species interactions that benefit at least one of the participants and cause harm to neither
- penguins clustering in arctic
- clustering vegetation to protect from weather and provide organic materials to share
in harsh environments: more facilitation or competition
competition is less, facilitation is higher
how to assess if facilitation is going on in a population
- removal experiments
- remove neighbours and see if population struggle
- if so facilitation important
altitude and shelter effects on facilitation
- low alt, sheltered = competition dominant
- low alt, exposed = mixture
- mid alt, sheltered = mixture (balanced)
- mid alt, exposed = facilitation
- high alt, shattered and exposed = facilitation
in general low alt = c/f important
high alt = c/f important
in general low alt = competition important
high alt = facilitation important
–> all over the world
____ is the dominant ecological process structuring communities in extreme environments
facilitation
facilitation and competition are like to be occurring ____
at the same time
- so u get net effects, mixture of the 2
- c in extreme
- f in benign
mech of facilitation: Hydraulic lift in desert plant
- NIGHT dry soil near surface at night stomata of plant will shut, WP gradient from wet deep soil through root into dry soil at surface
- re-wet dry soil at surface
- DAY = normal transpiration and extra wet soil can be utilised
- DEEP ROOTED
- provides wet soil for other plants, benefiting neighbours
Nurse plants =
- established plant which allows others to establish below it
- e.g. established shrub tree & cacti beneath it
- reduced soil temp under nurse plant, some underneath plants can’t survive w/o nurse plant
negatives to being under nurse plant
- shading, competition for light
- comp for water -> cacti have shallower roots, better chance of absorbing water from short water bursts
nurse plants and their underneath plants: both have + ___ & - ____
positives of facilitation
negatives of competition
how to calc just the positive and negative effects facilitation and nurse plants
EFFECT SOF ANNUALS ON SHRUB
+ = (shrub & mass of annual vegetative material reduces wind so helps reduce water loss) - just the shrub
- = (shrub & annual plants) - (shrub and mass of annual vegetative materials red wind and therefore water loss)
- -> criticism = only + effect is the veg material reducing wind, red water loss
- difficult to distinguish between facilitation and competition
facilitation and competition effect annuals on shrubs and shrubs on annuals
effects vary
- time and conditions
- yearly (depending on rainfall)
- – low rainfall better to be in open, not competing w shrub for water
- lots of rainfall, better to be under, protection
facilitation changes concept of the ___ space
niche
- -competition dominant = being w neighbours shrinks your ecological niche
- facilitation dominant = expands niche space, increases range of places u can survive
a stress/productivity changes the negative impact can be explained by both ___
increased competition or decreased facilitation
