Seasonal and tidal impact on the organic compounds and nutrients distribution in tropical mangroves, Kerala, India

Seasonal changes in the concentration of nutrients and various organic compounds were studied in the waters surrounding mangroves and in the marshy areas of mangroves. Higher amounts of nutrients and organic compounds were observed during low tide. This is due to the remineralisation of plant detritus in this area. High concentration of carbohydrates, proteins, chlorophyll and phosphate were observed during monsoon, which can be attributed to the leaching of plant detritus as well as the land run-off. During pre-monsoon and post-monsoon high tannin and lignin concentration was noted. A 24-hour sampling was also done to study the tidal impact on the concentrations of various organic compounds and nutrients in this ecosystem. Even though a tidal impact was observed, a clear picture was not reported in this study.     

高氟环境对奶牛生产和繁殖性能的影响

通过检测宁夏某地奶牛内外环境中的饮水、饲料和土壤氟、硒、铜及血氟、毛氟、尿氟和全血硒、铜，证实该场奶牛高氟低硒低硐。日粮添加０。２６ｍｇ／ｋｇ硒和３．２ｍｇ／ｋｇ铜。连续饲喂３个月，低硒低铜现象消失，但高氟仍旧存在。高氟使奶牛子宫复旧时间、首次发情时间 科后配妊天数分别延长６．６ｄ、６ｄ和３８．５ｄ，产后孕酮含量始终低于健康奶牛，同时，奶牛胎衣不下发病率和乳房炎发病率分别高于健康奶牛１６．７％和１     

Variation and evaluation of coastal salt marshes

Ten intertidal salt marshes along the Rhode Island coast were sampled and compared in terms of the relative standing crop and height of tallSpartina alterniflora, density of shoots, seed production and size, fish populations, and the abundance of grass shrimp, fiddler crabs, insects, and birds. The marshes ranged from 0.49 to 52.61 hectares (1.2 to 130 acres) and included fringe marsh in dense urban developments as well as unspoiled waterfowl preserves in rural isolation. Large variation in most parameters made it impossible to separate the sites with statistical significance using either univariate or multivariate techniques. Moreover, there was little meaningful intercorrelation among the parameters. Although more intensive sampling might make it possible to separate individual marshes with statistical rigor, these results suggest that the necessary effort may be too great to allow comparative field sampling to play a practical part in wetlands evaluation programs. The results also indicate that there is little, if any, correlation between visual esthetic perceptions of a marsh and its ecological characteristics. This work suggests that the development of ecological rating systems will not provide a reliable tool for the management of coastal wetlands.     

What is hidden behind the concept of ecosystem efficiency in energy transformation?

The number of energy transformation levels in trophic webs is usually below five, but can be extended up to ten when parasites and hyper-parasites are included. Research on the structure and function of food webs is relevant to the complexity–stability–productivity debate. The aim of this theoretical analysis is to link energetic and connectional aspects of ecosystems with information theory. Updating an energetic model reported by Ricklefs [Ecologia, Zanichelli Editore S.p.A., Bologna, Italy, 1993, p. 896], our approach is integrated with a static analysis of food webs. The length of food webs is theoretically associated with the average ecological efficiency which can be empirically correlated with the effective connectance between species. Furthermore, the advantage of greater complexity when applied to a signalling network is qualitatively addressed.The overall efficiency of energy transformation into biomass throughout a trophic web, in an ecosystem with a given number of species, is the resultant of the various ecological efficiencies, η, at the transitions between the trophic levels. However, we propose that an increment in effective connectance and interspecies connectivity based on a superimposed signalling web may increase the η values, despite the fact that signalling per se has an energetic cost. According to this hypothesis, ecosystem stability would not be necessarily reduced by increasing the number of trophic levels, N, whenever stability in terms of persistence is improved by a cost-efficient regulatory network.     

Plant vintage, technology, and environmental regulation

We use data on productivity and pollution abatement costs at individual pulp and paper mills to test whether the impact of environmental regulation on productivity differs by plant vintage and technology. Plants with higher pollution abatement costs have significantly lower productivity levels. This relationship differs greatly based on a plant's technology, with productivity at integrated mills being greatly affected by abatement costs, while the impact at non-integrated mills is negligible. Plant vintage does not seem to matter, with older and newer plants showing similar impacts. Reported abatement costs appear to substantially understate the true costs of abatement. Accounting for the impact of technology differences makes some difference in the estimated overall impact of environmental regulation.     

Is mining a high-tech industry?: Investigations into innovation and productivity advance

The fundamental nature of the mining industry with respect to innovation is often questioned. Is it the conservative, stodgy industry commonly depicted by its critics or is it instead a sophisticated, high-tech industry as championed by many of proponents? Using productivity statistics, it can be shown that the innovation rate of metal mining companies directly compares with the rates associated with general manufacturing. This relationship has held true for the last 50 years. A significant difference lies in the high-tech manufacturing sector, which for the last approximately dozen years has held productivity increases of 9.5% per year, in contrast to general manufacturing and metal mining rates of 2.5% and 2.3% per year, respectively.     

Environmental policy and misallocation: The productivity effect of intensity standards

Firm-level idiosyncratic policy distortions misallocate resources between firms, lowering aggregate productivity. Many environmental policies create such distortions; in particular, output-based intensity standards (which limit firms energy use or emissions per unit of output) are easier for high-productivity firms to achieve. We investigate the productivity effect of intensity standards using a tractable general-equilibrium model featuring multiple sectors and firm-level heterogeneity. Qualitatively, we demonstrate that intensity standards are always inferior to uniform taxes, as they misallocate both dirty and clean inputs across firms and sectors, which lowers productivity. Quantitatively, we calibrate the model to US data and show that these productivity losses can be large.