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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,