Desempenho de dispositivos eletrônicos para a análise estrutural da floresta de terra firme na Amazônia Central

Technologies with the laser as operating principle have been considered a promising initiative to obtain demanding dendrometric variables in the field. However, such technologies need to be evaluated in terms of precision and accuracy in different forest ecosystems. This study aimed to evaluate the performance of two technologies in obtaining two dendrometric variables, the diameter measured at the breast height (DBH) and total height (Ht) in a terra firme forest in central Amazonia. The two technologies were a set of interconnected electronic devices (electronic caliper for the DAP and laser rangefinder for the Ht) and a terrestrial LiDAR (TLS). A total of 55 trees with DBH ≥ 10 cm were measured within a 30-m diameter circular plot. For the DBH, the measurements of the technologies were compared with measurements made by a diametric tape, whereas the measurements of Ht were compared with measurements using a metric tape. The measurements of DBH obtained with the different technologies were very similar in terms of precision and accuracy, with measurements with the electronic caliper showing a slight systematic tendency to underestimate the DBH tape measurements. On the other hand, Ht estimates using the different technologies presented a lower correspondence of the Ht measured by the metric tape. Measures from TLS were slightly better than those measured with laser rangefinder in terms of accuracy and accuracy. Ht measurements from the different technologies were compared with the estimates of Ht from two hypsometric equations adjusted for central Amazonia (Feldpaush et al. (2011) and Lima et al. (2012). Although with reasonable precision, the equation of Feldpaush et al. (2011) presented a strong bias in the estimates, systematically underestimating the real Ht when compared with the technologies analyzed and the equation of Lima et al. (2011). The equation of Lima et al. (2011), on the other hand, showed a tendency to underestimate trees larger than 20 m and to overestimate trees smaller than 20 m.Tecnologias que têm o laser como princípio de funcionamento vêm sendo consideradas promissoras para a obtenção de variáveis dendrométricas de difícil medição em campo. No entanto, tais tecnologias necessitam ser avaliadas quanto à precisão e acurácia em diferentes ecossistemas florestais. O objetivo deste estudo foi avaliar o desempenho de duas tecnologias para obtenção de duas variáveis dendrométricas, o diâmetro medido à altura de 1,30 m do solo (DAP) e a altura total (Ht), em uma área de floresta de terra-firme na Amazônia central. As tecnologias analisadas foram um conjunto de dispositivos eletrônicos interligados (suta eletrônica para o DAP e laser rangefinder para a Ht) e um LiDAR do tipo terrestre (TLS). Um total de 55 indivíduos arbóreos com DAP ≥ 10 cm foi medido dentro de uma parcela circular de 30 m de diâmetro. Para o DAP, as medidas das tecnologias foram comparadas com medidas realizadas com uma fita diamétrica, enquanto que as medidas de Ht foram comparadas com medidas utilizando fita métrica. As medidas de DAP obtidas com as diferentes tecnologias foram muito próximas em termos de precisão e acurácia, com as medidas com a suta eletrônica apresentando uma leve tendência sistemática em subestimar as medidas da fita diamétrica. Por outro lado, as estimativas da altura usando as diferentes tecnologias apresentaram uma menor correspondência das alturas medidas pelos aparelhos com as alturas reais. As medidas advindas do TLS foram ligeiramente melhores do que as medidas com o laser rangefinder em termos de precisão e acurácia. Foram também comparadas as medidas Ht advindas das diferentes tecnologias com as estimativas de Ht advindas de duas equações hipsométricas ajustadas para a Amazônia central (Feldpaush et al. (2011) e Lima et al. (2012). Embora com precisão satisfatória, a equação de Feldpaush et al. (2011) apresentou forte tendenciosidade nas estimativas, subestimando sistematicamente as Ht reais dos indivíduos, quando comparado com as tecnologias analisadas e a equação de Lima et al. (2011). A equação de Lima et al. (2011), por outro lado, apresentou uma tendência em subestimar árvores maiores de 20 m de Ht e superestimar árvores menores de 20 m

Fire efect on the seasonal forest structure in the cerrado biome

There are few studies on the effects of fire on the seasonal semideciduous forest of the Cerrado region. This study aimed to assess the effect of fire on Semideciduous forest fragments located in the Altamiro Moura Pacheco State Park (AMPSP). The study area is located in the central state of Goiás. A total of 10 plots (50 x 20 m; 1,000 m2) were drawn in the remaining forests seeking to portray two areas: area which underwent forest fire (burned area; B) and unburned area (unburned; UB). A total of 771 individuals with DBH (≥ 5 cm) were identified. A total of 303 individuals were recorded in the burned area (B), comprising 28 families, 41 genera and 47 species, while the unburned area (UB) had 468 individuals comprising 25 families, 43 genera and 50 species. The species Anadenanthera colubrina (Vell.) Brenan, Emmotum nitens (Benth.), Zanthoxylum rhoifolium Lam, Tapirira guianensis Aubl., Myracrodruon urundeuva Allemão and Luehea candicans Mart. had the highest Importance Value Index (IVI) values and occur in both areas. The percentage of dead trees differed between the areas, where the burned area had a mortality of 12.69% and the unburned area of 7.29% in regards to the number of individuals. Density per plot was the only parameter that differed between the areas, where the burned area (B) had the lowest values. The fire affected all diameter classes, demonstrating the fragility of this vegetation type in regards to fire. The fire had a greater effect on trees in the smaller diameter classes, reducing the frequency of individuals in the burned area and changing height distribution, which may have favored the establishment of lianas and invasive species

In situ short-term responses of Amazonian understory plants to elevated CO₂

The response of plants to increasing atmospheric CO2 depends on the ecological context where the plants are found. Several experiments with elevated CO2 (eCO2) have been done worldwide, but the Amazonian forest understory has been neglected. As the central Amazon is limited by light and phosphorus, understanding how understory responds to eCO2 is important for foreseeing how the forest will function in the future. In the understory of a natural forest in the Central Amazon, we installed four open-top chambers as control replicates and another four under eCO2 (+250 ppm above ambient levels). Under eCO2, we observed increases in carbon assimilation rate (67%), maximum electron transport rate (19%), quantum yield (56%), and water use efficiency (78%). We also detected an increase in leaf area (51%) and stem diameter increment (65%). Central Amazon understory responded positively to eCO2 by increasing their ability to capture and use light and the extra primary productivity was allocated to supporting more leaf and conducting tissues. The increment in leaf area while maintaining transpiration rates suggests that the understory will increase its contribution to evapotranspiration. Therefore, this forest might be less resistant in the future to extreme drought, as no reduction in transpiration rates were detected.</p

In situ short-term responses of Amazonian understory plants to elevated CO₂

The response of plants to increasing atmospheric CO2 depends on the ecological context where the plants are found. Several experiments with elevated CO2 (eCO2) have been done worldwide, but the Amazonian forest understory has been neglected. As the central Amazon is limited by light and phosphorus, understanding how understory responds to eCO2 is important for foreseeing how the forest will function in the future. In the understory of a natural forest in the Central Amazon, we installed four open-top chambers as control replicates and another four under eCO2 (+250 ppm above ambient levels). Under eCO2, we observed increases in carbon assimilation rate (67%), maximum electron transport rate (19%), quantum yield (56%), and water use efficiency (78%). We also detected an increase in leaf area (51%) and stem diameter increment (65%). Central Amazon understory responded positively to eCO2 by increasing their ability to capture and use light and the extra primary productivity was allocated to supporting more leaf and conducting tissues. The increment in leaf area while maintaining transpiration rates suggests that the understory will increase its contribution to evapotranspiration. Therefore, this forest might be less resistant in the future to extreme drought, as no reduction in transpiration rates were detected.</p

FIRE EFECT ON THE SEASONAL FOREST STRUCTURE IN THE CERRADO BIOME

There are few studies on the effects of fire on the seasonal semideciduous forest of the Cerrado region. This study aimed to assess the effect of fire on Semideciduous forest fragments located in the Altamiro Moura Pacheco State Park (AMPSP). The study area is located in the central state of Goiás. A total of 10 plots (50 x 20 m; 1,000 m2) were drawn in the remaining forests seeking to portray two areas: area which underwent forest fire (burned area; B) and unburned area (unburned; UB). A total of 771 individuals with DBH (≥ 5 cm) were identified. A total of 303 individuals were recorded in the burned area (B), comprising 28 families, 41 genera and 47 species, while the unburned area (UB) had 468 individuals comprising 25 families, 43 genera and 50 species. The species Anadenanthera colubrina (Vell.) Brenan, Emmotum nitens (Benth.), Zanthoxylum rhoifolium Lam, Tapirira guianensis Aubl., Myracrodruon urundeuva Allemão and Luehea candicans Mart. had the highest Importance Value Index (IVI) values and occur in both areas. The percentage of dead trees differed between the areas, where the burned area had a mortality of 12.69% and the unburned area of 7.29% in regards to the number of individuals. Density per plot was the only parameter that differed between the areas, where the burned area (B) had the lowest values. The fire affected all diameter classes, demonstrating the fragility of this vegetation type in regards to fire. The fire had a greater effect on trees in the smaller diameter classes, reducing the frequency of individuals in the burned area and changing height distribution, which may have favored the establishment of lianas and invasive species