Caracterização Morfométrica da Bacia Hidrográfica do Rio São José, Cascavel, PR

O conhecimento das características morfométricas de uma bacia hidrográfica é essencial para o desenvolvimento de planos que visem à compreensão dos processos neste meio. O objetivo do presente estudo foi realizar a caracterização morfométrica da bacia hidrográfica do rio São José, Cascavel, PR. Para isso, foram calculados, a partir da planta topográfica digitalizada do terreno, os parâmetros morfométricos para o estudo do comportamento hidrológico da bacia. A área de drenagem encontrada foi de 143,17 km² e o perímetro 54,41 km. A bacia hidrográfica do rio São José apresenta perfil alongado, coeficiente de compacidade de 1,27, fator de forma de 0,51 e índice de circularidade de 0,61, indicando que a precipitação pluviométrica sobre ela se concentra em diferentes pontos. A densidade de drenagem obtida foi de 0,84 kmkm-2. A altitude média encontrada foi de 684 m e o revelo do terreno foi classificado como suavemente ondulado (5%). A análise dos dados morfométricos mostrou que a bacia hidrográfica do rio São José é pouco susceptível a picos de enchentes

Physical, chemical, and biological properties of soil under soybean cultivation and at an adjacent rainforest in Amazonia

Land-use change in the Amazon basin has occurred at an accelerated pace during the last decade, and it is important that the effects induced by these changes on soil properties are better understood. This study investigated the chemical, physical, and biological properties of soil in a field under cultivation of soy and rice, and at an adjacent primary rain forest. Increases in soil bulk density, exchangeable cations and pH were observed in the soy field soil. In the primary forest, soil microbial biomass and basal respiration rates were higher, and the microbial community was metabolically more efficient. The sum of basal respiration across the A, AB and BA horizons on a mass per area basis ranged from 7.31 to 10.05 Mg CO2-C ha-1yr-1, thus yielding estimates for total soil respiration between 9.6 and 15.5 Mg CO2-C ha-1yr-1 across sites and seasons. These estimates are in good agreement with literature values for Amazonian ecosystems. The estimates of heterotrophic respiration made in this study help to further constrain the estimates of autotrophic soil respiration and will be useful for monitoring the effects of future land-use in Amazonian ecosystems

Seasonal and drought‐related changes in leaf area profiles depend on height and light environment in an Amazon forest

Seasonal dynamics in the vertical distribution of leaf area index (LAI) may impact the seasonality of forest productivity in Amazonian forests. However, until recently, fine-scale observations critical to revealing ecological mechanisms underlying these changes have been lacking. To investigate fine-scale variation in leaf area with seasonality and drought we conducted monthly ground-based LiDAR surveys over 4 yr at an Amazon forest site. We analysed temporal changes in vertically structured LAI along axes of both canopy height and light environments. Upper canopy LAI increased during the dry season, whereas lower canopy LAI decreased. The low canopy decrease was driven by highly illuminated leaves of smaller trees in gaps. By contrast, understory LAI increased concurrently with the upper canopy. Hence, tree phenological strategies were stratified by height and light environments. Trends were amplified during a 2015-2016 severe El Niño drought. Leaf area low in the canopy exhibited behaviour consistent with water limitation. Leaf loss from short trees in high light during drought may be associated with strategies to tolerate limited access to deep soil water and stressful leaf environments. Vertically and environmentally structured phenological processes suggest a critical role of canopy structural heterogeneity in seasonal changes in Amazon ecosystem function