Short-term changes in nitrogen availability, gas fluxes (CO2, NO, N2O) and microbial biomass after tillage during pasture re-establishment in Rondônia, Brazil

Anthropogenic conversion of primary forest to pasture for cattle production is still frequent in the Amazon Basin. Practices adopted by ranchers to restore productivity to degraded pasture have the potential to alter soil N availability and N gas losses from soils. We examined short-term (35 days) effects of tillage prior to pasture re-establishment on soil N availability, CO₂, NO and N₂O fluxes and microbial biomass C and N under degraded pasture at Nova Vida ranch, Rondônia, Brazilian Amazon. We collected soil samples and measured gas fluxes in tilled and control (non tilled pasture) 12 times at equally spaced intervals during October 2001 to quantify the effect of tillage. Maximum soil NH₄⁺ and NO₃⁻ pools were 13.2 and 6.3 kg N ha⁻¹ respectively after tillage compared to 0.24 and 6.3 kg N ha⁻¹ in the control. Carbon dioxide flux ranged from 118 to 181 mg C–CO₂ m² h⁻¹ in the control (non-tilled) and from 110 to 235 mg C–CO₂ m² h⁻¹ when tilled. Microbial biomass C varied from 365 to 461 μg g⁻¹ in the control and from 248 to 535 μg g⁻¹ when tilled. The values for N₂O fluxes ranged from 1.22 to 96.9 μg N m⁻² h⁻¹ in the tilled plots with a maximum 3 days after the second tilling. Variability in NO flux in the control and when tilled was consistent with previous measures of NO emissions from pasture at Nova Vida. When tilled, the NO/N₂O ratio remained <1 after the first tilling suggesting that denitrification dominated N cycling. The effects of tilling on microbial parameters were less clear, except for a decrease in qCO₂ and an increase in microbial biomass C/N immediately after tilling. Our results suggest that restoration of degraded pastures with tillage will lead to less C matter, at least initially. Further long-term research is needed.     

Reproductive seasonality in Saanen goats kept under tropical conditions

Tropical Animal Health and Production - This study aimed to verify the reproductive seasonality in Saanen goats from distinct parity orders (nulliparous, primiparous, and pluriparous) throughout an...     

Release of doxycycline through cellulose acetate symmetric and asymmetric membranes produced from recycled agroindustrial residue: Sugarcane bagasse

Cellulose acetate is one of the components employed in drug controlled-release systems in the form of membranes. The aim of this study was to examine the controlled-release of doxycycline employing cellulose acetate symmetric and asymmetric membranes as matrices. The cellulose triacetate was produced from sugarcane bagasse through a homogeneous acetylation reaction, using acetic acid as the solvent, acetic anhydride as the acetylating agent and sulfuric acid as the catalyst. The viscosity average molecular weight of the cellulose acetate produced was 39,000 g mol⁻¹. The symmetric membranes were produced using a system solvent of dichloromethane/ethanol (9:1, v/v) and the asymmetric membranes were produced from the same solvent system and 10% of water. For the formulation of both, 5% of doxycycline was used. The membranes were characterized by thermal analysis (DSC and TGA) and scanning electron microscopy SEM. The release of doxycycline through cellulose triacetate matrices was examined using spectrophotometric analysis in the ultraviolet-visible region, at 275 nm. The results revealed that asymmetric membranes release 80% of the drug in 100 min, while symmetric membranes release 14% of the drug during the same time interval.     

Antiparasitic efficacy of dietary administration of trichlorfon (Masoten®) in the control of Neoechinorhynchus buttnerae (Neochinorhynchidae) in Colossoma macropomum (Serrasalmidae)

Aquaculture International - This study investigated the efficacy of trichlorfon against Neoechinorhynchus buttnerae, as well as its palatability, residue analysis, and the blood parameters of...     

Effects of dredging operations on sediment quality: contaminant mobilization in dredged sediments from the Port of Santos, SP, Brazil

Background, aim, and scope  

Contaminated sediments are a worldwide problem, and mobilization of contaminants is one of the most critical issues in environmental risk assessment insofar as dredging projects are concerned. The investigation of how toxic compounds are mobilized during dredging operations in the channel of the Port of Santos, Brazil, was conducted in an attempt to assess changes in the bioavailability and toxicity of these contaminants.     

A review of extracellular virulence product of Vibrio species important in diseases of cultivated shrimp

Shrimp aquaculture is an important industry that experiences significant losses from Vibrio species, especially at the larval and juvenile stages. Proteinaceous virulence factors, including alkaline proteases, metalloproteases, cysteine proteases and alkaline serine proteases, have been identified as important elements in Vibrio pathogenesis. This review summarizes current knowledge regarding the principal pathogenic Vibrio species in shrimp, with emphasis on relevant exotoxins and their modes of action, principal characteristics and molecular database. This pathogenic factors and their relation with other molecules produced by microorganisms may be help to understand the virulence mechanisms present in Vibrio strain.     

Germination and seedling growth of <Emphasis Type="Italic">Dimorphandra jorgei</Emphasis> MF Silva and <Emphasis Type="Italic">Swartzia macrostachya</Emphasis> Benth. var. <Emphasis Type="Italic">riedelii</Emphasis> Cowan

Dimorphandra jorgei MF Silva (Caesalpinaceae) and Swartzia macrostachya Benth. var. riedelii Cowan (Fabaceae) are tree species from the southern Bahian Atlantic Forest, identified for the restoration of degraded areas. The objective of this research is to study their seed germination and seedling growth to develop simple methods for seedling production in small scale nurseries. Because the species have distinct dormancy and germination characteristics, the seeds were submitted to different treatments. D. jorgei seeds were immersed in hot water, scarified and stored for 12 weeks in the laboratory environment (25°C). S. macrostachya seeds were submitted to different combinations of drying and storage in the laboratory environment or refrigerator (4°C). Seedlings were submitted to two light treatments for 3 months: partial shade (52% of full sun) and full shade (12% of full sun). In D. jorgei, the highest germination occurred for scarified seeds (87%) and for seeds stored for 12 weeks and then scarified (69%). In S. macrostachya the undried control seeds had the highest germination, followed by that of the refrigeration storage treatment, without predrying (99% and 97%, respectively). The average values for the growth parameters were greater in full shade for D. jorgei, while S. macrostachya seedlings showed greater growth rates in partial shade. Two months growth is recommended before D. jorgei seedlings are of the sufficient size and leaf number for field planting. On the other hand, a period of 4 months is recommended for S. macrostachya, due to its relatively slow growth.     

Planting mahogany in canopy gaps created by commercial harvesting

Attempts at natural forest management of mahogany (Swietenia macrophylla King) have so far met with limited success, whilst many plantations are beset by the shoot borer Hypsipyla spp. In this paper we present preliminary results of an approach to enrichment planting that aims to balance economic returns (rapid growth and good silvicultural form) with intervention costs and changes to forest structure. Mahogany seedlings were planted in gaps created by selective timber harvesting and that ranged in vertical projected area from 91 to 542 m² (mean = 257 m²). Seedlings grew within the matrix of gap regrowth, with limited control of competing vegetation. Sixty-one percent of seedlings had survived by 4.4 years (equivalent to an annual mortality rate of 10.5% year⁻¹), and had reached a mean height of 4.5 m. Stocking levels of mahogany were similar to that of naturally regenerated commercial species in unplanted gaps of the same age, but mahogany seedlings were significantly taller. The incidence of shoot borer attack on mahogany stems was relatively low (54.7%), but, more importantly, most damaged stems (58%) responded by producing a single replacement leader. The cost of the proposed methodology (US$ 94 per gap over 4.4 years) was low compared to the high value of mahogany timber relative to other species in the forest. The implications of planting mahogany in gaps for forest management and the potential benefits to conservation of the species are considered.     

Potential use of visible and near-infrared spectroscopy for pine species discrimination by examination of needles

The correct identification of pine species is necessary for proper application of wood in forest?based industries, since the quality of each species’ wood depends on factors intrinsic to the material. The aim of this study was to evaluate the potential use of near?infrared and visible spectroscopy in the discrimination of pine species planted in southern Brazil. Needles of Pinus clausa, P. glabra, P. kesiya, P. oocarpa, P. palustris, P. pseudostrobus, P. rigida, P. roxburghii and P. serotina were collected from experimental plantations located in the region of Rio Negro, Paraná, Brazil. The needles were dried and milled for analysis. The evaluation was performed with a spectral range of 400–750?nm (visible) and 1 000–2 500?nm (near?infrared). Analysis using the visible spectra resulted in two principal components explaining 95% of the variation between the needle samples. In the near?infrared analysis, it was possible to discriminate between all nine pine species studied using only two principal components, where the first explained 99% of the variation between species. Spectroscopy based on needles can be used for pine species discrimination, using the original data without mathematical treatment, in southern Brazil.