Transcript Plant Ecology - Chapter 5

Plant Ecology - Chapter 5
Populations
Population Growth
Births
Deaths
Immigration
Emigration
Population Growth
Genets - genetically
distinct individuals
Ramets 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/stages
Have differing
importance to
population
Population Structure
Animal populations
usually age-structured
Age determines role,
importance to
population
Age not as important for
plants - size is far more
important
Plant populations stagestructured
Population Structure
Plant stages
frequently based on
size - number of
leaves, mass,
height categories,
diameter categories
Frequently
impossible to
determine plant age
Population Structure
Plants have very
flexible growth
patterns
Can 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
circumstances
Plants 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 growth
Pre-repro, repro, postrepro
Life Cycle Graphs
Summaries of transitions
between stages
Life Tables - Cohort
Matrix Models
Combine life cycle graphs with life table data
to understand which stage classes have the
strongest effects on population growth
Which stage needs protection? Which stage
class is most affected by fire? Which stage
limits population growth?
Matrix Models
Can be used to predict age-based quantities from
stage-based data
Long-Lived Plants
Problems studying longlived plants
Longer 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 justify
Incorporate cyclic
variability (e.g., pest
outbreaks)
Compare old to new
photographs
Variable Population Growth
Matrix modeling
generalizations allow for
estimates not possible
two decades ago
Long-run population
growth rates
Extinction probabilities
Minimum viable
population sizes