Influence of four soil maintenance practices on Collembola communities in a Mediterranean vineyard

We studied the influence of four soil maintenance practices on Collembola communities in the soil of a Mediterranean vineyard: (a) postemergence herbicide with glyphosate; (b) postemergence and pre-emergence herbicides with glyphosate, terbuthylazine, diuron and oryzalin; (c) natural flora and (d) tillage to a depth of 10–15 cm. Total Collembola abundance, species diversity and species richness significantly varied between the four practices. Notably, the practice using postemergence and pre-emergence herbicides had significantly lower values. Identification of Collembola at species level allowed an interspecies comparison and revealed significant differences for the most common species between the four practices, with each practice being characterized by a different set of species. None of the species were found to be significantly more abundant in the plots treated with postemergence and pre-emergence herbicides.     

Temporal changes of resource use,soil fertility and economic situation in upland Northwest Vietnam

Agricultural land in lowland Vietnam is scarce due to population growth. Hence, cultivation is increasingly practised on the steep upland slopes. Factors affecting resource use, soil fertility and household economics were studied in six villages of the Black Thai ethnic group in northwest Vietnam. Farmers were interviewed about their individual household situation. Yield development of major crops and cropping patterns in upland cultivation over the last 50 years were recorded in group discussions. In addition, soil fertility was analysed on different land‐use units. Formerly predominant upland rice changed to maize and cassava production at present. Decreasing soil fertility and a shift from subsistence to market‐oriented production, facilitated by new maize varieties and better access to markets are major causes. The Black Thai farmers economy has improved in recent years. The decline in soil fertility is concealed by higher maize yields from new varieties, and soil fertility conservation ranks low among farmers' priorities. The improved economy of the individual households might be of short duration if farmers cannot be sensitized to new resource management options. These have to be developed in line with farmers' priorities and the fragile environment of Vietnam's uplands. Copyright © 2002 John Wiley & Sons, Ltd.     

Photocatalytic Removal of the Antibiotic Cefotaxime on TiO<Subscript>2</Subscript> and ZnO Suspensions Under Simulated Sunlight Radiation

This study presents the main results about the removal of the antibiotic cefotaxime (CTX) under simulated sunlight radiation using heterogeneous photocatalysis with titanium dioxide (TiO₂) and zinc oxide (ZnO) in aqueous solutions. The effects of pH and catalyst initial load on pollutant removal were assessed considering the response surface methodology and a central composite circumscribed experimental design, which allowed to determine the optimized conditions that lead to a higher substrate elimination. Experimental results indicated that evaluated parameters have a significant effect on antibiotic removal in both TiO₂ and ZnO suspensions. In addition, the role of photogenerated holes, hydroxyl, and superoxide anion radicals on CTX degradation was evaluated to clarify the reaction mechanism. Finally, analysis of the dissolved organic carbon content in solutions and the antibacterial activity of treated samples showed that photocatalytic treatments were able to reduce a considerable portion of the organic matter present in the systems and its antimicrobial activity.     

Contamination of pastures by polycyclic aromatic hydrocarbons (PAHs) in the vicinity of a highway

To assess PAH contamination pastures, grass and soil samples have been collected from 10 m (d1), 50 m (d2), and 150 m (d3) perpendicular to a French highway (70,000 vehicles per day) and at a control site in a rural area away from nearby contaminating sources. Total PAH concentration ranges from 767 ng/g dry weight to 3989 ng/g dry weight, according to the matrix and the distance from the highway. Distance is not a significant factor for PAH deposition on grass, while in soil it has an effect between d1 and d2 or d3. The total PAH concentration in highway samples is 8 times higher than in control site samples for grass and 7 to 4 times higher for soil. Fluoranthene, pyrene, and phenanthrene are the major PAHs in grass samples at the control site and the highway, but the concentrations are about 5 times higher near the highway. In soil samples collected near the highway, the values of concentrations between all compounds are not statistically different. PAH deposition on grass is linked to the physicochemical properties of the compounds, which lead to a specific distribution of each molecule (according to their volatility and the number of aromatic rings) while no specific behavior is revealed in soil.     

基于植被覆盖率的农村居民点整理潜力估算及实证

为合理估算农村居民点整理潜力,该文提出基于植被覆盖率的农村居民点整理潜力测算新思路。借助植被覆盖率对农村居民点斑块进行分类,通过分析抽样农村居民点斑块的植被覆盖与内部用地结构得到整理潜力修正系数,从而建立基于植被覆盖率修正的农村居民点整理潜力估算模型,并以北京市门头沟区为例展开实证研究。研究结果表明,门头沟区无整理潜力的农村居民点占大多数,具有整理潜力的农村居民点主要集中在经济相对落后的乡镇,并且这部分农村居民点多远离主干道;山区具有中、高整理潜力的农村居民点略多于平原、浅山区,而低整理潜力的农村居民点明显多于平原、浅山区;门头沟区规划整理的农村居民点内部包含有大量农用地,其中建设用地比例只占63.19%～71.54%,但是,第二次土地调查将整个农村居民点都作为建设用地调绘;因而,一些不考虑植被覆盖修正的农村居民点整理潜力测算方法夸大了整理潜力,放大了城乡建设用地增减挂钩的效果。该文为进一步合理估算农村居民点整理理论潜力提供参考。     

Intermuscular variation in tenderness: association with the ubiquitous and muscle-specific calpains

The biochemistry of intermuscular variation in tenderness is not fully understood. To investigate the role of the calpains in this process we performed two experiments using bovine and ovine species. In the bovine experiment, two distinct muscles, longissimus thoracis et lumborum (LT) and psoas major (PM), were used. In the ovine experiment, four muscles, LT, PM, semimembranosus (SM), and semitendinosus (ST), were used. Muscles were sampled at death for the determination of the steady-state mRNA level of calpains and calpastatin and the activities of calpain 1, 2, and calpastatin. Muscles were also sampled to determine the temporal changes in pH, tenderness, and the activity of the ubiquitous calpain system during postmortem aging. The results of the relative rate of tenderization in both species was found to be related to muscle type; LT had the highest value in both species. Within species, the mRNA steady-state levels of calpain 1 and calpastatin were similar in various bovine and ovine muscles. Bovine calpain 2 mRNA level was significantly lower in the LT than in the PM. Ovine calpain 2 mRNA level was lower, but not significantly different, in the LT compared to the other muscles. The mRNA level of bovine calpain 3 was significantly higher in the LT muscle than in the PM. In the ovine, the mRNA level of calpain 3 was highest in the LT, followed by SM, PM, and ST. Results on the activity of the ubiquitous calpain system in various muscles at death were dependent on muscle type and species. Temporal changes in the activity of calpains and calpastatin during the first 24 h of postmortem aging were similar in the muscles studied: calpain 1 and calpastatin declined significantly and calpain 2 remained relatively unchanged. The temporal changes in muscle pH in both experiments indicated that the extent and rate of pH decline during aging was related to muscle type. Correlation analysis between the relative rate of tenderization and mRNA expression of calpains revealed a strong relationship with calpain 3 in both species.     

Distribution and repeatability of faecal egg counts and blood parameters in dairy goats naturally infected with gastrointestinal nematodes

The frequency, distribution and repeatability of measurements related to infection with gastrointestinal nematodes have been estimated in dairy goats. Monthly faecal and blood samples were taken over two grazing seasons from a flock of 120 naturally infected goats. The frequency distribution of egg excretion was positively skewed at each sampling date, suggesting an aggregative distribution of parasites. Overdispersed distributions were also apparent for pepsinogen and inorganic phosphate values. Repeatabilities for each parameter were estimated within each year. The values ranged between 0.23 to 0.43 and were relatively similar during the 2 years, with the highest coefficients recorded for pepsinogen. For each parameter, moderate to high repeatabilities were also estimated between the 2 years. Overall, the data suggest that, in dairy goats, the distribution of worms is overdispersed with a few individuals repeatedly harbouring large worm populations. These results have practical implications for genetic selection for resistance to worm infection and for selective administration of anthelmintics.     

Spatial distribution of leaf dry weight per area and leaf nitrogen concentration in relation to local radiation regime within an isolated tree crown

To assess the spatial distribution of photosynthetic capacity within an isolated 20-year-old walnut tree (Juglans regia L.) crown, the distribution of relevant leaf characteristics was measured. Variations in leaf dry weight per area (W(a)), and nitrogen content on a weight (N(w)) and area basis (N(a)) were studied along two horizontal and one vertical gradients of leaf irradiance, at two dates (July 30 and September 3). In addition, the content of total nonstructural carbon on a weight (TNC(w)) and area basis (TNC(a)) was measured on July 30. Concurrently, the spatial distribution of daily integrated leaf irradiance within the crown was simulated by a three-dimensional radiation transfer model over a one week period before sampling at each date. High spatial heterogeneity was observed for W(a) (from 50 to 140 g m(-2)), TNC(a) (from 4 to 17 g m(-2)) and N(a) (from 1.2 to 3.6 g m(-2)) among the foliage. Although TNC(w) and N(w) were not correlated and only weakly correlated to daily leaf irradiance, respectively, W(a), TNC(a) and N(a) were strongly correlated to daily leaf irradiance. The relationship between observed N(a) and simulated daily leaf irradiance was used to assess the spatial distribution of N(a) within the crown at each date. Total leaf nitrogen in the foliage was estimated to be 339 g in late July and 317g in early September. For the whole crown (i.e., 1729 current-year shoots), N(a) increased strongly with basal shoot diameter (an index of "shoot vigor"), highlighting the fact that large shoots were mainly located in sunlit locations and exhibited high photosynthetic capacity.     

Effects of the halothane genotype and slaughter weight on texture of pork

The objective of this study was to investigate the effects of the halothane (HAL) genotype, slaughter weight (SW), and the HAL x SW interaction on compositional and textural traits of raw and cooked pork. Pigs were bred to exhibit one of the three HAL genotypes (NN, Nn, and nn) with otherwise equivalent genomes. The nn halothane reactors are known to typically produce PSE pork, whereas NN pigs do not typically produce PSE pork. Pietrain x Large White gilts and boars, all with verified Nn genotype (by DNA test), were mated to obtain F2 littermates of the three HAL genotypes. These pigs were slaughtered at either 101 +/- 3 ("light") or 127 +/- 3 ("heavy") kg BW and were evaluated for longissimus muscle traits. The pH at .5 h after death (pH1) was 6.35, 6.13, and 5.68 in NN, Nn, and nn pigs, respectively. Sarcomere length was greater in nn than in NN and Nn pigs (1.94 vs 1.83 and 1.85 microm, respectively). Mechanical resistance was higher in nn than in NN pigs for both raw and cooked meat. Meat from nn pigs was judged by a trained panel to be less rough, more cohesive, harder, more fibrous, less granular, more elastic, and less easy to swallow than meat from NN pigs. For most traits under study, the heterozygotes were intermediate between the homozygotes but closer to NN than to nn pigs. Muscle from heavy pigs had longer sarcomeres and less moisture than muscle from light pigs. The n allele of the HAL gene unfavorably affects pork texture, and this effect is maintained throughout the range of 101 to 127 kg BW.