Long-term meteorological analyzes suggest an increase in air temperature and a decrease in rainfall over the Amazon biome. The effect of these climate changes on the forest remains unresolved, because field observations on functional traits are sparse in time and space, and the results from remote sensing analyses are divergent. Then, we analyzed the drought response in a ‘terra firme’ forest fragment in the southwestern Amazonia, during an extreme drought event influenced by ENSO episode (2015/2017), focusing on stem growth, litter production, functional traits and forest canopy dynamics. We use the Moderate Resolution Imaging Spectroradiometer (MODIS), corrected by Multi-Angle Implementation of Atmospheric Correction (MAIAC) to generate the enhanced vegetation index (EVI) and green chromatic coordinate (Gcc) vegetation indices. We monitor stem growth and measure the functional traits of trees in situ, such as the potential at which the plant loses 50% of hydraulic conductivity (P50), turgor loss point (πTLP), hydraulic safety margin (HSM) and isohydricity. Our results suggest that: (a) during the dry season, there is a smooth reduction in EVI values (browning) and an increase in the wet season (greening); (b) in the dry season, leaf flush occurs, when the water table still has a quota at the limit of the root zone; (c) the forest showed moderate resistance to drought, with water as the primary limiting factor, and the thickest trees were the most resistant; and (d) a decline in stem growth post-El-Niño 2015/2016 was observed, suggesting that the persistence of negative rainfall anomalies may be as critical to the forest as the drought episode itself.
O objetivo desse trabalho foi avaliar a influência dos modelos de colonização ("espinha de peixe" e topográfico) nos diferentes estágios sucessionais: Inicial (SS1), Intermediário (SS2) e Avançado (SS3) na Amazônia Legal Brasileira, através de atributos fitossociológicos apoiados por imagens de satélite, e entender as variáveis que afetam os padrões de sucessão florestal e as diferenças existentes entre as variáveis biométricas dentro dos diferentes assentamentos localizados na porção Noroeste do Estado de Rondônia. Para isso foram amostrados 56 transectos de 10 x 250 m em áreas de estágio sucessional avançado, 64 transectos de 10 x 10 m em áreas de estágio sucessional intermediário, e 79 transectos de 2 x 2 m em áreas de estágio sucessional inicial. No modelo de colonização denominado "espinha de peixe", foram identificadas 23 famílias e 43 espécies-no estágio sucessional inicial; no estágio SS2 foram identificadas 20 famílias e 41espécies; já no estágio sucessional avançado, foram catalogadas 37 famílias com 42 espécies. No modelo de colonização cuja forma é conhecida como topográfico, foram catalogadas no estágio inicial-32 famílias e 60 espécies; no estágio intermediário-29 famílias e 54 espécies; e no estágio avançado-43 famílias e 57 espécies. As famílias mais importantes neste processo de sucessão foram as Fabaceae, Caesalpiniaceae, Lauraceae e Bignoniaceae em ambos os modelos.
Several colonisation projects were implemented in the Brazilian Legal Amazon in the 1970s and 1980s. Among these colonisation projects, the most prominent were those with the “fishbone” and “topographic” models. Within this scope, the settlements known as Anari and Machadinho stand out because they are contiguous areas with different models and structures of occupation and colonisation. The main objective of this work was to evaluate the dynamics of Land-Use and Land-Cover (LULC) in two different colonisation models, implanted in the State of Rondônia in the 1980s. The fishbone and topographic or Disorganised Multidirectional models were implemented in the Anari and Machadinho settlements, respectively. A 36-year time series of Landsat images (1984–2020) was used to evaluate the rates and trends in the LULC process in the different colonisation models. In the analysed models, a rapid loss of primary and secondary forests (anthropized areas) was observed, mainly due to the dynamics of its use, established by the Agriculture/Pasture relation with a heavy dependence on road construction. Understanding these two forms of occupation can help the future programs and guidelines of the Brazilian Legal Amazon and any tropical rainforest across the globe.
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