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Distributional Dynamics in the Hawaiian Vegetation
|Title:||Distributional Dynamics in the Hawaiian Vegetation|
|Issue Date:||Apr 1992|
|Publisher:||University of Hawai'i Press|
|Citation:||Mueller-Dombois D. 1992. Distributional dynamics in the Hawaiian vegetation. Pac Sci 46(2): 221-231.|
|Abstract:||Vegetation ecology is usually divided into two broad research
areas, floristic/environmental gradient analysis and studies of vegetation dynamics.
The early influential American ecologist Clements combined the two
areas into a dynamic system for classifying vegetation. His succession and
climax theory, however, was later severely criticized. A new approach to the
study of distributional dynamics, called "landscape ecology," focuses on the
dynamics of spatial vegetation patterns. There is a spatial hierarchy rule, which
implies greater stability of species and community patterns when one considers
larger area units versus smaller ones. It is argued that this rule is frequently
transgressed in biotically impoverished areas, like the Hawaiian Islands, where
certain dominant plant species have become established over unusually broad
areas and habitat spectra. A further point made is that with "species packing"
successional patterns change from auto-succession, where the dominant species
retains dominance by in situ generation turnover (termed chronosequential
monoculture), via "normal" succession (i.e., displacement of dominants by other
dominants over time [termed chronosequential polyculture]), to small-area patch
or gap dynamics (termed chronosequential gap rotation). Examples of the three
spatially different succession paradigms are given for Hawaii, and the point is
made that chronosequential monocultures cannot be expected to last, but
change to chronosequential gap rotation with the invasion of alien dominants.
Before the invasion of alien dominants, certain native dominants seem to have
segregated into races or varieties by evolutionary adaptation to successional
habitats. Finally, the concept of climax is discussed as having two meanings: (I)
permanency of community type, which can only be observed for the aggregate
assemblage of smaller communities in a larger space, such as occupied by a
biome; (2) the mode of organic production in ecosystem development. The
mode seems to occur between 1000 and 3000 yr in the Hawaiian rainforest
biome on volcanic soils. Thereafter, productivity declines with acidification and
soil nutrient impoverishment over a million years and more. This amounts
to a retrogression in the course of primary succession.
|Appears in Collections:||Pacific Science Volume 46, Number 2, 1992|
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