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キーワード:
Central Amazon; Floodplain forest; Várzea; Restinga baixa; Primary succession; Canopy structure; Radial increment; Wood biomass production; Growth model; Sustainable forest management
要旨:
Growth rates of stands and tree species are a basic
information for the development of sustainable
management plans in tropical rainforests. In Central
Amazonian floodplains the growth rhythm of trees is
triggered by the annual long-term flooding, which results in
a cambial dormancy and the formation of annual tree rings.
This allows the determination of tree ages and growth rates.
In the Mamairauá Sustainable Development Reserve
(MSDR), located in the Amazon state of Brazil, we studied
various successional stages in their canopy structure,
floristic composition and annual wood biomass production.
All trees = 10 cm diameter at breast height (dbh) were
investigated in plots differing in size by several parameters
like tree species, dbh, tree height, crown area and crown
exposure. From each tree cores were sampled to determine
wood density, tree age and mean radial increment.
Additional cross-sections were taken at different tree
heights to model cumulative diameter growth and height
growth of the most important tree species. The results show
changes along the successional development which
incorporates a increasing number of tree species, a
decreasing tree density, and dynamical changes in the
canopy structure. Wood density increases considerably
along the chronosequence leading to an accumulation of
above-ground wood biomass, but can not compensate the
declining radial and volume increment which results in a
lower mean biomass production. The volume increment and
biomass production of softwood tree species in the early
succession vary significantly from those of densewood
timber species in the mature forests. There is a urgent need
to consider differences in the growth behavior of tree
species to guarantee the sustainability of a forest
management as it is planned in MSDR
