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LEC 2bPlant Populations in Vegetation

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Describing the structure of a population is central to understanding plant dynamics. plants are not evenly distributed in either time or space. differences in environmental conditions, biotic neighborhoods,and site histories influence the distribution and dynamics of plantpopulations. unlike most animals, individual adult plants do not move, ingeneral, making tracking of survivorship and mortality mucheasier. plants can, however produce new individuals asexually and candrop or add new sets of organs (flowers, leaves, stems, andbranches) in response to the external environment (biotic orabiotic). thus, the material of the plant ecologist is not limited to thedistribution and dynamics of individuals in a population butincludes the dynamic growth of the ever-changing plant body.

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Plant Demography

study of changes in population sizeand structure through time

note: circadian rhythm to aeons

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Sampling

Quadrat (an area of any shape that can be delimited sothat plant species may be listed, counted, or have their

vegetation cover estimated

Completely random plot selection (picking plots over an

area at random

Stratified random sampling (subdividing the area into

sections and random sampling is done in each section);

this is used in areas with strong environmental

gradient; thus the area is well represented

It is important to note that: how the density and distribution of thesespecies or populations in the area are essential information withregards to the interactions going on with other organisms (intraspecificor interspecific) or nonliving factors within the area (ecosystem).

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Population POPULATION (a group of individuals of the same species living in

the same area)

There is no limit on the size of the area so a population may be all

the cogon grass in an area in the campus

whatever the species or area, all populations undergo 3 distinctphases during their existence:

Growth Stability Decline

the KEY is BALANCE: no forces or rigid structures exist that preventecosystems from changing; in fact, ecosystems can and do change, even

drastically, as conditions are altered; the one thing that enables

ecosystems to sustain a given composition of species over long periods of

time is that all relationships in the system are in a DYNAMICbalance.thus, ECOSYSTEMbalance is POPULATIONbalance.

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thatsallfor

now,