Vulnerabilidade mecânica de árvores relacionada a tempestades convectivas na Amazônia Central, Manaus (AM)
Storms producing high winds are frequent and major natural disturbance events in the Central and Western Amazon, affecting forest structure and diversity at the landscape level. The stability of Amazonian tree species against storm-induced wind-throw has never been evaluated using direct experime...
| Autor principal: | Ribeiro, Gabriel Henrique de Mello |
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| Grau: | Tese |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia – INPA
2020
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| Assuntos: | |
| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/4989 http://lattes.cnpq.br/5790046030990301 |
| Resumo: |
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Storms producing high winds are frequent and major natural disturbance events in the
Central and Western Amazon, affecting forest structure and diversity at the landscape level.
The stability of Amazonian tree species against storm-induced wind-throw has never been
evaluated using direct experimental approaches such as winching. This has typically been
related to the distribution of wind speeds, butt little is known about difference in the
susceptibility to wind damage cause by site-related difference in growth form. Previous work
in the Central Amazon found that tree mortality caused by storm-induced blowdowns,
primarily by snapping and uprooting, was highest on plateaus and slopes, while much lower
in valley forests. In this study we investigated the critical turning moments (Mcrit) of 60 trees,
ranging from 19.0 to 41.1 cm in diameter at breast height (DBH) and located in different
topographic positions, using a cable-winch load-cell system. Our approach used torque as a
measure of tree failure to a point of no return (snapping or uprooting). Size controlled
variation in Mcrit was quantified for cardeiro (Scleronema mincranthum (Ducke) Ducke),
mata-matá (Eschweilera spp.), and a random selection of trees across a number of species.
Our analysis of Mcrit revealed that tree resistance to failure increased with size and differed
among species, but no effects of topography or failure mode were found for the species
groups either separately or pooled. For the random species, total explained variance increased
from an R2 of 0.49 for DBH alone, to 0.68 when including both DBH and stem wood density
(SWD) in a multiple regression model. For the random selection of trees those that have
interlocked grain seems not to increase Mcrit whit increases in size ,when compared to similar
sized trees with other grain orientation. The slenderness factor (total tree height/DBH, both in
m) influence Mcrit for the different groups, overall values bellow 80 show higher resistance.
Depending on the size attribute (DBH or above ground biomass (AGB)) for similar sized trees
on group is just more resistant than the others. This mechanics approach allows the
comparison of tree vulnerability induced by wind damage across ecosystems and facilitates
the use of forest structural information in ecosystems models. Our results indicate that
topographic differences in wind-throw vulnerability are likely due to elevational differences
in wind velocities and crown exposure, rather than by differences in soil properties related to
topography |