A monodominant rain forest on Maraca Island, Roraima, Brazil : forest structure and dynamics

A forest type dominated by Peltogyne gracilipes Ducke (Caesalpiniaceae) occurs on Maraca Island on a range of soil types. Maraca is located in Roraima State (Brazil) in the Rio Uraricoera and has an area of about 100,000 ha. This study compares the structure and floristic composition of the Peltogyne forest with the most widespread lowland forest type on Maraca and investigates some factors that could be involved in the persistent monodominance of Peltogyne. Three 0.25 ha plots were set up in each of three forest types: Peltogyne-rich forest (PRF), Peltogyne-poor forest (PPF) and forest without Peltogyne (FWP). Within each plot all trees (~ 10 cm dbh) were recorded. Seedlings and saplings were sampled in sub-plots of 2 m x 1 m (seedlings) and 4 m x 4 m (saplings). In the PPF and FWP, Sapotaceae were the most important family with the highest dominance and relative density values. Caesalpiniaceae showed high values in the PRF and PPF. Licania kunthiana, Pradosia surinamensis and Simarouba amara occurred in the forest types. Peltogyne dominated had 20% of stems and 53% of the trees ~ 10 cm dbh, and 91% of the canopy layer the canopy in total basal stems and 97% in all the the PRF and area of all of the total basal area of individuals > 50 cm dbh. In PPF, Lecythis corrugata and Tetragastris panamensis were the most abundant species, followed by Peltogyne. In the FWP the most abundant trees (~ 10 cm dbh) were L. kunthiana and P. surinamensis. In general, Peltogyne had low rates of seed predation and herbivory, but suffered locally high levels of damage to its seeds by leaf-cutter ants and was once observed to have an infestation of larvae of the moth Eulepidotis phrygionia on its young leaves. Peltogyne had no allelopathic effects on tested species and had VA mycorrhizal associations. Its occurrence remains unexplained but is most clearly correlated with soil magnesium

Magnon delocalization in ferromagnetic chains with long-range correlated disorder

We study one-magnon excitations in a random ferromagnetic Heisenberg chain with long-range correlations in the coupling constant distribution. By employing an exact diagonalization procedure, we compute the localization length of all one-magnon states within the band of allowed energies $E$. The random distribution of coupling constants was assumed to have a power spectrum decaying as $S(k)\propto 1/k^{\alpha}$. We found that for $\alpha < 1$, one-magnon excitations remain exponentially localized with the localization length $\xi$ diverging as 1/E. For $\alpha = 1$ a faster divergence of $\xi$ is obtained. For any $\alpha > 1$, a phase of delocalized magnons emerges at the bottom of the band. We characterize the scaling behavior of the localization length on all regimes and relate it with the scaling properties of the long-range correlated exchange coupling distribution.Comment: 7 Pages, 5 figures, to appear in Phys. Rev.

Oceanic eddy‑induced modifications to air–sea heat and CO2 fluxes in the Brazil‑Malvinas Confluence

Sea surface temperature (SST) anomalies caused by a warm core eddy (WCE) in the Southwestern Atlantic Ocean (SWA) rendered a crucial influence on modifying the marine atmospheric boundary layer (MABL). During the first cruise to support the Antarctic Modeling and Observation System (ATMOS) project, a WCE that was shed from the Brazil Current was sampled. Apart from traditional meteorological measurements, we used the Eddy Covariance method to directly measure the ocean–atmosphere sensible heat, latent heat, momentum, and carbon dioxide ( CO2) fluxes. The mechanisms of pressure adjustment and vertical mixing that can make the MABL unstable were both identified. The WCE also acted to increase the surface winds and heat fluxes from the ocean to the atmosphere. Oceanic regions at middle and high latitudes are expected to absorb atmospheric CO2, and are thereby considered as sinks, due to their cold waters. Instead, the presence of this WCE in midlatitudes, surrounded by predominantly cold waters, caused the ocean to locally act as a CO2 source. The contribution to the atmosphere was estimated as 0.3 ± 0.04 mmol m− 2 day− 1, averaged over the sampling period. The CO2 transfer velocity coefficient (K) was determined using a quadratic fit and showed an adequate representation of ocean–atmosphere fluxes. The ocean–atmosphere CO2, momentum, and heat fluxes were each closely correlated with the SST. The increase of SST inside the WCE clearly resulted in larger magnitudes of all of the ocean–atmosphere fluxes studied here. This study adds to our understanding of how oceanic mesoscale structures, such as this WCE, affect the overlying atmosphere

Practical Science and Environmental Education Workshop in Manaus, Brazil

It is an unequivocal fact that Amazonian tropical forest is the largest remaining primary forest in the world. The ecosystem in the region is e tremely comple with high biodiversity (Peres et al. 2010). Conservation and protection of the dynamic forest and river regions is e tremely important not only for the natural environments, but also for the economy and social dependence of benefits from such abundant natural environments. Important natural parameters that affect status of the natural environments include light (natural sunlight), soil, and water, which abundantly e ist in the Amazon region. Solar energy is the primary energy source for the majority of living organisms in both terrestrial and aquatic ecosystems, and drives the diurnal and seasonal cycles of biogeochemical processes (Monteith & Unsworth 2013). In particular, in situ light data remains one of the most underappreciated data measurements although having a significant impact on the physical, chemical and biological processes in the ecosystem (Johnsen 2012). Soil provides the fundamental basis for all terrestrial living organisms including the Amazonian forests as well as life-sustaining infrastructure for human society. Water is the most essential single entity to constitute all organisms from a single cell to the earth. Understanding of importance and roles of each factor and interaction of such comple dynamics in the natural environments can serve as fundamental platform for natural scientists, particularly for young scientists such as university students. The objective of this workshop was to provide hand- on scientific and environmental education for university students in Manaus, Amazonas, Brazil through practical field measurements using the three most important parameters in the natural ecosystem composed of natural sunlight, soil, and water. The workshop was divided into a series of lectures, in situ field sampling, and data processing, analysis and interpretation with the ultimate goal of empowering the undergraduate students with research-centered environmental education and e perience of developing international collaboration.departmental bulletin pape