Respostas ecofisiológicas de espécies da sucessão secundária crescendo sobre pastagens abandonadas na Amazônia central
Deforestation contributes to reducing the Amazonian biome with direct and indirect effects on regional and global climatic change. Pasture formation continues to be the main driver of the expansion of deforested areas. Amazonian pastures become unsustainable due to low soil fertility and to the s...
| Autor principal: | Silva, Carlos Eduardo Moura da |
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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/1/4974 http://lattes.cnpq.br/1016638921761687 |
| Resumo: |
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Deforestation contributes to reducing the Amazonian biome with direct and indirect effects on
regional and global climatic change. Pasture formation continues to be the main driver of the
expansion of deforested areas. Amazonian pastures become unsustainable due to low soil
fertility and to the small use of production technology the pastures after use become
unsustainable and then they are abandoned giving place to emerging secondary forest. To
understand the strategies adopted by the more frequent species early secondary successional:
Vismia japurensis and Vismia cayennensis; Mid secondary successional: Bellucia
grossularioides and Laetia procera; Late secondary successional: Goupia glabra, the
ecophysiological characteristics of the species were determined and relationship with the
successional chronosequence. The study was carried in the secondary forests at different
stages of regeneration (0-19 years), located in the experimental area of the Forest Fragment
Biological Dynamic Project-PDBFF (02º34'S, 60º07'W). The chemical characteristics and soil
fertility were measured as well as the nutrients leaf concentration, specific leaf area, water
potential, gas exchanges and chlorophyll a fluorescence parameters. The N, P and K
concentrations increased and while Ca and Mg decreased in the soil with the age of the stand.
Leaf nutrient concentrations, as well as nutrient-use efficiencies, varied among the species
and in relation stand age. Photosynthetic rate differed among species, with higher values in
early successional (14-17 Vmol m-2 s-1) than in late successional species (8-10 Vmol m-2 s-1).
High values of Amax were observed for species in the genus Vismia. Values of Amax, gs, Rd,
and E declined with stand age for all species except G. glabra. G. glabra and L. procera
showed reductions in photosynthetic rate during the low-precipitation season. A typical OJIP
transient curve was observed for all species, with modifications for the responses of G. glabra
and L. procera in the low-precipitation season. The performance index of the species
increased with stand age, especially for B. grossularioides and L. procera. Plants in young
stands dissipated more energy in the form of fluorescence than did those in old stands. The
maximum quantum efficiency of PSII primary photochemistry increased with stand age for all
species (0.80 to 0.83). Water potential showed little variation among the species and also
varied little with stand age. Both the values of the chlorophyll content index and the specific
leaf area increased with stand age for all species. The data suggest that species differ within
each successional position group and that resource-use efficiency becomes limited despite the
improvement of nutritional conditions with time. Increases in specific leaf area and decreases
in photosynthetic rate and dissipation of energy with increasing stand age suggesting that
modifications in the plasticity of the plants might have occurred over time and that these
modifications are usually associated with alterations in irradiance readiness. Therefore, the
importance of secondary-succession species should be emphasized with regard to reception
and use of available primary resources in the first 15 years of growth on abandoned pastures.
These species play a role in absorbing atmospheric carbon in the face of current changes in
the Amazonian landscape. |