Measurement of Greenhouse Gas Flux from Agricultural Soils Using Static Chambers

Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the biogeochemical drivers of climate change and to the development and evaluation of GHG mitigation strategies based on modulation of landscape management practices. The static chamber-based method described here is based on trapping gases emitted from the soil surface within a chamber and collecting samples from the chamber headspace at regular intervals for analysis by gas chromatography. Change in gas concentration over time is used to calculate flux. This method can be utilized to measure landscape-based flux of carbon dioxide, nitrous oxide, and methane, and to estimate differences between treatments or explore system dynamics over seasons or years. Infrastructure requirements are modest, but a comprehensive experimental design is essential. This method is easily deployed in the field, conforms to established guidelines, and produces data suitable to large-scale GHG emissions studies.     

Sampling accuracy of reef resource inventory technique

A new technique called the reef resource inventory (RRI) was developed to map the distribution and abundance of benthos and substratum on reefs. The rapid field sampling technique uses divers to visually estimate the percentage cover of categories of benthos and substratum along 2×20 m plotless strip-transects positioned randomly over the tops, and systematically along the edge of reefs. The purpose of this study was to compare the relative sampling accuracy of the RRI against the line intercept transect technique (LIT), an international standard for sampling reef benthos and substratum. Analysis of paired sampling with LIT and RRI at 51 sites indicated sampling accuracy was not different (P>0.05) for 8 of the 12 benthos and substratum categories used in the study. Significant differences were attributed to small-scale patchiness and cryptic coloration of some benthos; effects associated with sampling a sparsely distributed animal along a line versus an area; difficulties in discriminating some of the benthos and substratum categories; and differences due to visual acuity since LIT measurements were taken by divers close to the seabed whereas RRI measurements were taken by divers higher in the water column. The relative cost efficiency of the RRI technique was at least three times that of LIT for all benthos and substratum categories and as much as 10 times higher for two categories. These results suggest that the RRI can be used to obtain reliable and accurate estimates of relative abundance of broad categories of reef benthos and substratum.

Spatial heterogeneity of wind forcing: application to artificial reef functioning influenced by the circulation in the Bay of Marseilles, France

In the frame of the largest French project of artificial production reefs, initiated by the city of Marseilles in 2001, the present study aimed at describing the hydrodynamic pattern of the coastal area considered, by the use of a 3D numerical modelling. Results were local wind statistics, bottom current fields and drifting particle maps. The knowledge of the hydrodynamic connexions between particle (such as larvae) sources or targeted areas linked to the reefs, allows us to explain the success or failure of the reefs' colonizing. Moreover, the study confirms the wind spatial variability and demonstrates the error resulting from the use of an average but locally absent wind direction.     

细胞离子在振荡电磁场作用下的受力模型分析

本文通过生物细胞模型,研究振荡电场、振荡磁场以及振荡磁场产生的感应电场对细胞离子的作用机理。模型分析结果表明,电场力和罗仑兹力对细胞膜两侧的自由离子将产生加速度,振荡离子将产生周期性电位移。该模型同时也解释了脉冲电磁场比同参教的连续场产生更多的生物效应,以及连续场在开始施加和切除时的效应最大。     

REHABILITATION AND RELEASE OF MARINE MAMMALS IN THE UNITED STATES: RISKS AND BENEFITS

Rehabilitation of stranded marine mammals elicits polarized attitudes: initially done alongside display collections, but release of rehabilitated animals has become more common. Justifications include animal welfare, management of beach use conflict, research, conservation, and public education. Rehabilitation cost and risks have been identified that vary in degree supported by data rather than perception. These include conflict with fisheries for resources, ignorance of recipient population ecology, poor understanding of long-term survival, support of the genetically not-so-fit, introduction of novel or antibiotic-resistant pathogens, harm to human health, and cost. Thus facilities must balance their welfare appeal against public education, habitat restoration, human impact reduction, and other conservation activities. Benefits to rehabilitating marine mammals are the opportunity to support the welfare of disabled animals and to publish good science and so advance our understanding of wild populations. In specific cases, the status of a population may make conservation the main reason for rehabilitation. These three reasons for rehabilitation lead to contrasting, and sometimes conflicting, management needs. We therefore outline a decision tree for rehabilitation managers using criteria for each management decision, based on welfare, logistics, conservation, research, and funding to define limits on the number of animals released to the wild.     

Mechanism of Inhibition of Translation Termination by Blasticidin S

Understanding the mechanisms of inhibitors of translation termination may inform development of new antibacterials and therapeutics for premature termination diseases. We report the crystal structure of the potent termination inhibitor blasticidin S bound to the ribosomal 70S?release factor 1 (RF1) termination complex. Blasticidin S shifts the catalytic domain 3 of RF1 and restructures the peptidyl transferase center. Universally conserved uridine 2585 in the peptidyl transferase center occludes the catalytic backbone of the GGQ motif of RF1, explaining the structural mechanism of inhibition. Rearrangement of domain 3 relative to the codon-recognition domain 2 provides insight into the dynamics of RF1 implicated in termination accuracy.     

Integrated aquaculture in Chinese lakes and paddy fields

While pond culturing is still the staple of Chinese freshwater fisheries, its extensive development is handicapped by the increasing shortage of land resource for cereal production in face of China’s population growth. Accordingly, people have looked towards the development of aquaculture in lakes (and reservoirs) in the 1970s. This paper reviews the successful integrated measures taken in an experiment for raising fish in Donghu lake (East lake) of Wuhan. By way of (1) stocking the right kinds of fish; (2) producing a large number of sizeable fingerlings; (3) improving fish screens; (4) controlling predatory fish; and (5) applying the ‘driving and concentrating’ bulk harvesting fishing method, fish production of the lake has increased steadily from 180 t in 1971 to 800 t in 1978, and then to 1840 t in 1995, all in an area of 1500 ha, and all without any supplementary feeding. Integrated aquaculture in paddy fields, known to be beneficial to both rice and fish production, has been regaining momentum in recent years. The paper summarizes its underlying principle, its benefits—economical, social and ecological—and the prospect of its development in China.     

Regulation of calcium fluxes in rat pancreatic islets: Quinine mimics the dual effect of glucose on calcium movements

The effects of quinine and 9-aminoacridine, two blockers of potassium conductance in islet cells, on ⁴⁵Ca efflux and insulin release from perifused islets were investigated in order to elucidate the mechanisms by which glucose initially reduces ⁴⁵Ca efflux and later stimulates calcium inflow in islet cells. In the absence of glucose, 100 μM quinine stimulated ⁴⁵Ca net uptake, ⁴⁵Ca outflow rate and insulin release. Quinine also dramatically enhanced the cationic and the secretory response to intermediate concentrations of glucose, but had little effect on ⁴⁵Ca net uptake, ⁴⁵Ca fractional outflow rate and insulin release at a high glucose concentration (16.7 mM). The ability of quinine to stimulate ⁴⁵Ca efflux depended on the presence of extracellular calcium, suggesting that it reflects a stimulation of calcium entry in the islet cells. In the absence of extracellular calcium, quinine provoked a sustained decrease in ⁴⁵Ca efflux. Such an inhibitory effect was not additive to that of glucose, and was reduced at low extracellular Na⁺ concentration. At a low concentration (5 μM), quinine, although reducing ⁸⁶Rb efflux from the islets to the same extent as a non-insulinotropic glucose concentration (4.4 mM), failed to inhibit ⁴⁵Ca efflux. In the presence of extracellular calcium, 9-aminoacridine produced an important but transient increase in ⁴⁵Ca outflow rate and insulin release from islets perifused in the absence of glucose. In the absence of extracellular calcium, 9-aminoacridine, however, failed to reduced ⁴⁵Ca efflux from perifused islets. It is concluded that quinine, by reducing K⁺ conductance, reproduces the effect of glucose to activate voltage-sensitive calcium channels and to stimulate the entry of calcium into the B-cell. However, the glucose-induced inhibition of calcium outflow rate, which may also participate in the intracellular accumulation of calcium, does not appear to be mediated by changes in K⁺ conductance.     

Composition of grazed and cleared temperate grassy woodlands in eastern Australia: patterns in space and inferences in time

Abstract. A regional vegetation survey of the temperate grassy woodlands (temperate savanna) in Australia was designed to assess the effects of clearing and grazing on the composition of vegetation remnants and the adjacent pasture matrix. Vegetation was sampled across a range of habitats using 77 0.1024‐ha quadrats; the relative abundance of species was recorded. Classification analysis clustered the sites into three main groups that corresponded to intensity of grazing/clearing followed by groups based on underlying lithology (basalt, metasediment, granites). Using Canonical Correspondence Analysis, exogenous disturbance and environmental variables were related to the relative abundance of species; grazing intensity had the highest eigenvalue (0.27) followed by tree canopy cover (0.25), lithology (0.18), altitude (0.17) and slope (0.10). Based on two‐dimensional ordination scores, six species response groups were defined relating to intensity of pastoralism and nutrient status of the landscape. Abundance and dominance of native shrubs, sub‐shrubs, twiners and geophytes were strongly associated with areas of less‐intense pastoralism on low‐nutrient soils. The strongest effects on species richness were grazing followed by canopy cover. Continuously grazed sites had lower native species richness across all growth forms except native grasses. There was no indication that intermediate grazing intensities enhanced forb richness as a result of competitive release. Species richness for all native plants was lowest where trees were absent especially under grazed conditions. Canopy cover in ungrazed sites appeared to promote the co‐existence of shrubs with the herbaceous layer. Predicted declines in forb richness in treeless, ungrazed, sites were not detected. The lack of a disturbance‐mediated enhancement of the herbaceous layer was attributed to habitat heterogeneity at 0.1 ha sampling scale.