Download - Plant Ecology - Chapter 5 Populations. Population Growth Births Deaths Immigration Emigration
Plant Ecology - Chapter 5
Populations
Population Growth
BirthsDeathsImmigrationEmigration
Population Growth
Genets - genetically distinct individualsRamets - physiologically independent but not genetically distinct individuals
Population Growth
“Birth” - seed production, vegetative clones, mature pollen grains (gametophyte)?
Population Growth
“Individual” - distinctly separate plants (unitary) or interconnected, related individuals (modular)
Population Structure
Population size important, but so is the distribution of individuals among different ages/sizes/stagesHave differing importance to population
Population Structure
Animal populations usually age-structuredAge determines role, importance to populationAge not as important for plants - size is far more importantPlant populations stage-structured
Population Structure
Plant stages frequently based on size - number of leaves, mass, height categories, diameter categoriesFrequently impossible to determine plant age
Population Structure
Plants have very flexible growth patternsCan lose parts and shrink from year to year, go through years of dormancy, or not appear above ground in a given year
Population Structure
Stage structuring difficult under these circumstancesPlants can advance directly through stages, remain at some stage, or undergo reversions
Population Structure
Plant ecologists must keep track of multiple stages and all possible transitions between them
Population Structure
In structured populations, individuals of different stages make different contributions to future population growthPre-repro, repro, post-repro
Life Cycle Graphs
Summaries of transitionsbetween stages
Life Tables - Cohort
Matrix ModelsCombine life cycle graphs with life table datato understand which stage classes have thestrongest effects on population growth
Which stage needs protection? Which stageclass is most affected by fire? Which stagelimits population growth?
Matrix ModelsCan be used to predict age-based quantities fromstage-based data
Long-Lived Plants
Problems studying long-lived plantsLonger life span than researchers!Year-to-year variation in environmental conditions, longer intervals between censuses - misses younger plants
Long-Lived Plants
Static life tables problematic - assumptions such as stable age structure impossible to justifyIncorporate cyclic variability (e.g., pest outbreaks)Compare old to new photographs
Variable Population Growth
Matrix modeling generalizations allow for estimates not possible two decades agoLong-run population growth ratesExtinction probabilitiesMinimum viable population sizes