Using a simple apparatus to measure direct and diffuse photosynthetically active radiation at remote locations.

Plant canopy interception of photosynthetically active radiation (PAR) drives carbon dioxide (CO2), water and energy cycling in the soil-plant-atmosphere system. Quantifying intercepted PAR requires accurate measurements of total incident PAR above canopies and direct beam and diffuse PAR components. While some regional data sets include these data, e.g. from Atmospheric Radiation Measurement (ARM) Program sites, they are not often applicable to local research sites because of the variable nature (spatial and temporal) of environmental variables that influence incoming PAR. Currently available instrumentation that measures diffuse and direct beam radiation separately can be cost prohibitive and require frequent adjustments. Alternatively, generalized empirical relationships that relate atmospheric variables and radiation components can be used but require assumptions that increase the potential for error. Our goal here was to construct and test a cheaper, highly portable instrument alternative that could be used at remote field sites to measure total, diffuse and direct beam PAR for extended time periods without supervision. The apparatus tested here uses a fabricated, solar powered rotating shadowband and other commercially available parts to collect continuous hourly PAR data. Measurements of total incident PAR had nearly a one-to-one relationship with total incident radiation measurements taken at the same research site by an unobstructed point quantum sensor. Additionally, measurements of diffuse PAR compared favorably with modeled estimates from previously published data, but displayed significant differences that were attributed to the important influence of rapidly changing local environmental conditions. The cost of the system is about 50% less than comparable commercially available systems that require periodic, but not continual adjustments. Overall, the data produced using this apparatus indicates that this instrumentation has the potential to support ecological research via a relatively inexpensive method to collect continuous measurements of total, direct beam and diffuse PAR in remote locations.

Long-range guided THz radiation by thin layers of water.

We propose a novel method to guide THz radiation with low losses along thin layers of water. This approach is based on the coupling of evanescent surface fields at the opposite sides of the thin water layer surrounded by a dielectric material, which leads to a maximum field amplitude at the interfaces and a reduction of the energy density inside the water film. In spite of the strong absorption of water in this frequency range, calculations show that the field distribution can lead to propagation lengths of several centimeters. By means of attenuated total reflection measurements we demonstrate the coupling of incident THz radiation to the long-range surface guided modes across a layer of water with a thickness of 24 µm. This first demonstration paves the way for THz sensing in aqueous environments.

Colonización de la naturaleza: una aproximación desde el extractivismo en Colombia / Colonization of nature: an approach from extractivism in colombia

Este artículo de investigación pretende brindar elementos de análisis sobre el complejo tema de la colonización de la naturaleza. En él se hace una argumentación descriptiva basada hallazgos teóricos sobre las relaciones entre el extractivismo, una práctica propia del dispositivo colonial, y lo que aquí denominamos colonización de la naturaleza. El artículo presenta inicialmente un balance del impacto en la configuración de la visión-apropiación ancestral del territorio y su contenido cultural, a raíz de la imposición de una nueva semántica, en referencia al dispositivo de poder colonial. Luego, se analiza la relación del extractivismo con el proceso de colonización de la naturaleza, para finalmente esbozar una reflexión breve vinculando contextos y problemas contemporáneos.

This research paper aims at providing some elements of analysis on the complex issue of the colonization of nature. In it a descriptive argument is carried out based on theoretical findings on the relationships between extractivism, which is a proper practice of the colonial device, and what is here called colonization of nature. The article initially presents an assessment of the impact on the configuration of the ancestral vision and appropriation of the territory and its cultural contents, as a result of the imposition of a new semantics, in reference to the device of the colonial powers. Then, the relationship between extractivism and the process of colonization of nature is analyzed; to finally sketch a brief reflection, by linking contemporary issues and contexts.

Ecologia de nidificação de abelhas do gênero Partamona (Hymenoptera: Apidae) na caatinga, Milagres, Bahia / Ecology of nesting of bees of the genus Partamona in caatinga, Milagres, Bahia

Neste estudo foi analisada a riqueza, a abundância, os sítios de nidificação, o padrão de distribuição espacial, a densidade dos sítios potenciais disponíveis e dos sítios nidificados pelas espécies de abelhas sem ferrão do gênero Partamona e dos termiteiros arbóreos nidificados pelas abelhas, em uma área restrita de caatinga arbórea, em Milagres, Bahia, Brasil. Duas espécies ocorreram em simpatria, Partamona rustica (94,1 por cento) e Partamona cupira (5,9 por cento), ambas nidificando em termiteiros arbóreos da espécie Constrictotermes cyphergaster. Outras três espécies de termiteiros arbóreos ocorreram na área (Nasutitermes corniger, Nasutitermes macrocephalus e Microcerotermes sp.). Os térmitas arbóreos nidificaram principalmente na umburana (Commiphora leptophloeos). As espécies de abelhas do gênero Partamona têm como estratégia de nidificação na caatinga utilizar cavidades pré-existentes que consistem em ocos abertos em termiteiros arbóreos pelo periquito jandaia (Aratinga cactorum), para reprodução. Após o nascimento dos filhotes, o oco é abandonado e em seguida uma colônia de abelhas do gênero Partamona constrói ali o seu ninho, ocupando-o e isolando-o com geoprópolis, sendo freqüente a ocupação destes ocos por outros inquilinos.

The species richness, abundance, nesting sites, spatial distribution pattern, density of available substrates and substrates used for nesting by Partamona species were studied in a restricted area of a tropical dry forest/woodlands ecosystem called "arboreal caatinga" in Milagres, Bahia State, Brazil. Two species of the genus Partamona, occurred in the studied area, Partamona rustica (94.1 percent) and Partamona cupira (5.9 percent), both nested in arboreal termites nests of the Constrictotermes cyphergaster species. Other three species of arboreal termites' nests occurred in the area (Nasutitermes corniger, Nasutitermes macrocephalus and Microcerotermes sp.). The arboreal termites had nested mainly in "umburana" (Commiphora lepthophloeos). The nesting strategy of Partamona species consist in occupying preexisting cavities opened in arboreal termites nested by a parakeet called "jandaia" (Aratinga cactorum), for reproduction. After the birth of the younglings, the cavity is abandoned and after that a colony of Partamona bees occupies it and starts its nest construction, isolating it with mud and resin. Frequently these cavities are occupied by other inquilines.

[Effects of waste water sediments on the levels of heavy metals ion the soil and plants]. / Vliianie osadkov stochnykh vod na soderzhanie tiazhelykh metallov v pochve i rasteniiakh.

Field small-plot experiments studied the effects of sediments of waste water from Saransk disposal systems. The content of toxic heavy metals (lead, arsenic, and cadmium) in the waste-water sediments, was shown to be not greater than their maximum permissible concentrations (32, 2, and 10 mg per kg of dried soil, respectively). With the use of waste-water sediments, the content of manganese, copper, tin, nickel, vanadium, beryllium, cobalt, iron, and chromium was found to correspond to their baseline level in the soil and plants.