Descripción: The inability to monitor wetland drag coefficients at a regional scale is rooted in the difficulty to determine vegetation structure from remote sensing data. Based on the fact that the backscattering coefficient is sensitive to marsh vegetation structure, this paper presents a methodology to estimate the drag coefficient from a combination of SAR images, interaction models and ancillary data. We use as test case a severe fire event occurred in the Paraná River Delta (Argentina) at the beginning of 2008, when 10% of the herbaceous vegetation was burned up. A map of the reduction of the wetland drag coefficient is presented. © 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.

Descripción: We compared several attributes of vegetation structure of the understory and of bird species richness, guild abundance, and total abundance between a 200-ha area of semiarid Chacoan forest and another 200-ha area of the same forest where shrubs were manually removed, in Santiago del Estero province, Argentina. We seasonally recorded birds at 60 point count stations (30 in each type of habitat) between March 1998 and August 1999. The shrubless area showed higher percentages of herb cover and bare ground than the forest, whereas in the forest there were higher covers of litter and shrubs and a higher shrub height than in the shrubless area. Moreover, the shrubless area showed a lower species richness and bird abundance than the forest in summer. At the guild level, analyses revealed that bark insectivores were more abundant in the shrubless area, whereas foliage insectivores, terrestrial insectivores, and arboreal seed eaters were more abundant in the forest. Our results show that shrub removal has a great influence on the structure of bird assemblages, which persists several years later after the application of this technique. We recommend that, in case of massive shrub removal, stripes of shrubby vegetation should be maintained in order to guarantee the inclusion of shrub-associated bird species in the mosaic landscape. © The Neotropical Ornithological Society.

Descripción: The study area is located in central-western Santa Cruz including El Chaltén town between 49°00'and 49°36'S - 73°30'and 72°00'W. Environmental variability, relief, parent material, altitude, climate, vegetation and soils were recognized. According to characteristics of the soils, it is possible to differentiate three sectors: western, central and eastern. Inceptisols, Spodosols and Andisols dominate in the first, meanwhile in Central area the main soils are Molisolls and Entisols. Aridisols and aridic Entisols dominate in the Eastern sector. A west-east variation trend, in relation to soil features could be established: an increase in pH, CEC, exchangeable bases and % of CaCO3. Inversely there is an increase % C, pHNaF (in udic regime soils) and divalent/monovalent cations relationship.

Descripción: Probe electrospray ionization (PESI) is a recently developed ESI-based ionization technique which generates electrospray from the tip of a solid needle. In this study, we have applied PESI interfaced with a time of flight mass spectrometer (TOF-MS) for direct profiling of phytochemicals in a section of a tulip bulb in different regions, including basal plate, outer and inner rims of scale, flower bud and foliage leaves. Different parts of tulip petals and leaves have also been investigated. Carbohydrates, amino acids and other phytochemicals were detected. A series of in vivo PESI-MS experiments were carried out on the second outermost scales of four living tulip bulbs to monitoring the change of carbohydrate content during the first week of initial growth. The breakdown of carbohydrates was observed which was in accordance with previous reports achieved by other techniques. This study has indicated that PESI-MS can be used for rapid and direct analysis of phytochemicals in living biological systems with advantages of low sample consumption and little sample preparation. Therefore, PESI-MS can be a new choice for direct analysis/profiling of bioactive compounds or monitoring metabolic changes in living biological systems. © 2009.

Descripción: Most insects' assemblages differ with forest type and show vertical stratification. We tested for differences in richness, abundance and composition of hymenopteran families and mymarid genera between sugar maple (Acer saccharum) and white pine (Pinus strobus) stands and between canopy and understory in northeastern temperate forests in Canada. We used flight interception traps (modified malaise traps) suspended in the canopy and the understory in a split-split block design, with forest type as the main factor, forest stratum as the first split factor, and collection bottle location as the second split factor. Hymenopteran families and mymarid genera differed in their diversity depending on forest type and stratum. Both family and genera richness were higher in maple than in pine forests, whereas family richness was higher in the canopy and top bottles and generic richness was higher in the understory and bottom bottles. Multivariate analysis separated samples by forest type, vegetation stratum, and bottle location. Family composition showed 77% similarity between forest types and 73% between the canopy and understory. At the lower taxa level, mymarid genera showed only 47% similarity between forest types and 40% between forest strata, indicating vertical stratification and relatively high β-diversity. Our study suggests that hymenopteran diversity and composition is strongly dependent on forest type and structure, making flying members of this order particularly vulnerable to forest management practices. It also shows that insect assemblage composition (especially at low-taxon levels), rather than relative abundance and richness, is the community attribute most sensitive to forest type and vertical stratification. © 2007 Entomological Society of America.