Effects of Recent Land-Use Practices on Soil Nutrients and Succession under Tropical Wet Forest in Costa Rica

The effects of a variety of agricultural land uses were studied using soil nutrients, forest structure, and species assemblages as indicators. We compared soil properties and successional forests between abandoned cacao ( Theobroma cacao ) and abandoned palm ( Bactris gasipaes ) orchards, abandoned pasture, and mature forest. These sites co-occupy an alluvial terrace soil ( Andic Dystropept ) at La Selva Biological Station, Costa Rica. The agricultural sites were originally cleared of most or all forest vegetation approximately 30 years ago and went into succession approximately 7 years ago. Forest structure, species composition, soil nitrogen and phosphorus pools, and nitrogen-mineralization and nitrification rates were measured for each site. The abandoned palm orchard had lower basal area and stem density than other secondary forests of the same age. It also had significantly smaller nitrate (NaOH-extractable) and organic phosphorus pools and significantly lower net rates of nitrogen-mineralization and nitrification. It is evident that preserving tree cover does not necessarily maintain soil fertility. We found species richness and diversity in the secondary forests to be positively correlated with basal area at the time of abandonment.     

Abnormal gonadal morphology in intersex,<Emphasis Type="Italic"> Echinogammarus marinus</Emphasis> (Amphipoda): a possible cause of reduced fecundity?

Recent reports have demonstrated a cost associated with intersexuality in Amphipoda, including reduced fecundity and fertility. In this study, the gross morphology of the gonads in normal and intersex Echinogammarus marinus (Amphipoda) were compared to determine whether resource allocation to gonadal tissue accounted for this reduced fitness. Evidence for the presence of the male sex-determining hormone, androgenic gland hormone (AGH), was compared between sexual phenotypes using MALDI mass spectrometry. Two distinct intersex phenotypes (‘male’ intersex and ‘female’ intersex) were found, with variation in gonadal structure corresponding with external phenotype. Examination of male intersexes revealed normal testicular development (testes, seminal vesicles and vas deferens), but also revealed the formation of an oviduct. Ovaries of intersex females showed normal ovarian development, but were reduced in length by approximately 20% due to the presence of vas deferens. The number of vas deferens in intersex females was equal to the number (one or two) of genital papillae. We hypothesise that the reduced ovarian length observed in intersex females is a likely cause of the reduced brood size previously reported in intersex females of this species. Variation in the sexual phenotype corresponded both to development of the androgenic gland and to expression of a peptide fragment corresponding to the A chain of androgenic gland hormone (AGH). Androgenic glands and a putative AGH peptide were present in males. However, in both normal and intersex females, the androgenic glands were only present in a rudiment form and the peptide was not detected. Intersex males were found to possess abnormal glands that appeared hypertrophied. However, AGH peptides were not detected, supporting the suggestion that the intersex phenotype is manifested via perturbations of AGH.     

Relations between innovation management and organisational sustainability: a case study in a Brazilian higher education institution

Environment, Development and Sustainability - The objective of this work was to analyse the relations between innovation management and organisational sustainability in a Brazilian higher education...     

Translocation studies of 137Cs and 90Sr in bean plants (Phaseolus vulgaris): simulation of fallout

In case of an accident at a nuclear power plant with liberation of radioactive material into the atmosphere, knowledge about the behavior of plant species when in contact with radionuclides is indispensable for safety reasons. The leaf-fruit translocation is an important route through which agricultural products are contaminated by radionuclides. To quantify the leaf-fruit translocation factors for 137Cs and 90Sr in common beans (Phaseolus vulgaris) an experiment was carried out in a greenhouse with a randomized block design. 137Cs activity was determined by gamma-ray spectrometry, while chemical separation followed by beta counting of 90Y was used for 90Sr determination. The model applied for translocation indicated functional dependence between the moment of tracer application and the physiological development of the bean plant. Translocation factors obtained for 137Cs and 90Sr were 0.16 and less than 0.005, respectively.     

Correction to: Ecological restoration as a strategy for mitigating and adapting to climate change: lessons and challenges from Brazil

Mitigation and Adaptation Strategies for Global Change - The original version of the article unfortunately contained an error.     

Soil emissions of NO, N2O and CO2 from croplands in the savanna region of central Brazil

In the last 40 years, a large area of savanna vegetation in Central Brazil (Cerrado) has been converted to agriculture, with intensive use of fertilizers, irrigation and management practices. Currently, the Cerrado is the main region for beef and grain production in Brazil. However, the consequences of these agricultural practices on NO, N₂O and CO₂ emissions from soil to atmosphere are still poorly investigated. The objectives of this study were to quantify soil emissions of NO-N, N₂O-N and CO₂-C in different no-till cultivation systems in comparison with native savanna vegetation. The agricultural areas included: (a) the maize and Brachiaria ruzizienses intercropping system followed by irrigated bean in rotation; (b) soybean followed by natural fallow; and (c) cotton planting over B. ruzizienses straw. The study was performed from August 2003 to October 2005 and fluxes were measured before and after planting, after fertilizations, during the growing season, before and after harvesting. NO-N fluxes in the soybean field were similar to those measured in the native vegetation. In the cornfield, higher NO-N fluxes were measured before planting than after planting and pulses were observed after broadcast fertilizations. During Brachiaria cultivation NO-N fluxes were lower than in native vegetation. In the irrigated area (bean cultivation), NO-N fluxes were also significantly higher after broadcast fertilizations. Most of the soil N₂O-N fluxes measured under cultivated and native vegetation were very low (<0.6 ng N₂O-N cm⁻² h⁻¹) except during bean cultivation when N₂O-N fluxes increased after the first and second broadcast fertilization with irrigation and during nodule senescence in the soybean field. Soil respiration values from the soybean field were similar to those in native vegetation. The CO₂-C fluxes during cultivation of maize and irrigated bean were twice as high as in the native vegetation. During bean cultivation with irrigation, an increase in CO₂-C fluxes was observed after broadcast fertilization followed by a decrease after the harvest. Significantly lower soil C stocks (0-30 cm depth) were determined under no-tillage agricultural systems in comparison with the stocks under savanna vegetation. Fertilizer-induced emission factors of N oxides calculated from the data were lower than those indicated by the IPCC as default.     

Salt glands in the Jurassic metriorhynchid <Emphasis Type="Italic">Geosaurus</Emphasis>: implications for the evolution of osmoregulation in Mesozoic marine crocodyliforms

The presence of salt-excreting glands in extinct marine sauropsids has been long suspected based on skull morphology. Previously, we described for the first time the natural casts of salt-excreting glands in the head of the Jurassic metriorhynchid crocodyliform Geosaurus araucanensis from the Tithonian of the Vaca Muerta Formation in the Neuquén Basin (Argentina). In the present study, salt-excreting glands are identified in three new individuals (adult, a sub-adult and a juvenile) referable to the same species. New material provides significant information on the salt glands form and function and permit integration of evolutionary scenarios proposed on a physiological basis in extant taxa with evidence from the fossil record. G. araucanensis represents an advanced stage of the basic physiological model to marine adaptations in reptiles. G. araucanensis salt glands were hypertrophied. On this basis, it can be hypothesized that these glands had a high excretory capability. This stage implies that G. araucanensis (like extant pelagic reptiles, e.g. cheloniids) could have maintained constant plasma osmolality even when seawater or osmoconforming prey were ingested. A gradual model of marine adaptation in crocodyliforms based on physiology (freshwater to coastal/estuarine to estuarine /marine to pelagic life) is congruent with the phylogeny of crocodyliforms based on skeletal morphology. The fossil record suggests that the stage of marine pelagic adaptation was achieved by the Early Middle Jurassic. Salt gland size in the juvenile suggests that juveniles were, like adults, pelagic.     

210Po concentration in Perna perna mussels: looking for radiation effects

Twenty ropes with 400 Perna perna mussels seeds (3 cm shell size) were set-up on floating structures at Cabo Frio Island, Arraial do Cabo, approximately 100 km northeast of Rio de Janeiro city. A rope was taken out on a monthly basis, and the shell sizes of 100 seeds were measured. The haemolymph of 10 male and 10 female individuals was taken, and the same individuals were separated for 210Po/210Pb determination. After one year of monthly sampling, no clear correlation was observed between the 210Po concentration, mussel's age and weight. A mean 210Po concentration of 155 Bq kg(-1) wet weight basis, was obtained, which is comparable with data reported in the literature. The radiation dose did not have any observable effect on the micronuclei frequency and DNA breaks in the mussels. This was probably due to the low dose rate, 0.02 mGy d(-1), in comparison with the suggested potential dose limit of 10 mGy d(-1).     

Analysing the fate of nanopesticides in soil and the applicability of regulatory protocols using a polymer-based nanoformulation of atrazine

For the first time, regulatory protocols defined in the OECD guidelines were applied to determine the fate properties of a nanopesticide in two agricultural soils with contrasting characteristics. The nanoformulation studied had no effect on the degradation kinetics of atrazine indicating that (1) the release of atrazine from the polymer nanocarriers occurred rapidly relative to the degradation kinetics (half-lives 36–53 days) and/or that (2) atrazine associated with the nanocarriers was subject to biotic or abiotic degradation. Sorption coefficients, derived from a batch and a centrifugation technique at a realistic soil-to-solution ratio, were higher for the nanoformulated atrazine than for the pure active ingredient. Results indicate that the nanoformulation had an effect on the fate of atrazine. However, since the protocols applied were designed to assess solutes, conclusions about the transport of atrazine loaded onto the nanocarriers should be made extremely cautiously. The centrifugation method applied over time (here over 7 days) appears to be a useful tool to indirectly assess the durability of nanopesticides under realistic soil-to-solution ratios and estimate the period of time during which an influence on the fate of the active ingredient may be expected. More detailed investigations into the bioavailability and durability of nanopesticides are necessary and will require the development of novel methods suitable to address both the “nano” and “organic” characteristics of polymer-based nanopesticides.