Recycling in Brazil: Challenges and prospects

This article presents a comparative analysis of the performance in formal and informal areas that deal with solid waste in Brazil. The article demonstrates that there has been significant progress in areas related to recycling and that this progress has been based mainly on informality and on the precarious labour conditions for the pickers of recyclable materials. The article also focuses on the problems found in the model for waste recovery that is being implemented in Brazil and that is based on allocation of precarious waste recovery facilities; this model has mostly small operational capabilities even in large municipalities. These problems are discussed in contrast to the great challenges imposed by the new legal framework of the country. Finally, the article proposes a categorisation of the technological models of material recovery facilities (MRFs) based on their degree of automation and nominal capacities in a manner similar to that used worldwide for incineration plants.     

Resource supplements cause a change in colony sex-ratio specialization in the mound-building ant, Formica exsecta

We examine the role of food resources on split sex ratios in Formica exsecta. Models of resource-based sex allocation predict that greater resources will cause an increase in the production of reproductive females (gynes) and an increase in overall size of offspring. We experimentally increased food resources for a subset of colonies in a polygynous population with a very male-biased sex ratio. This increase in food availability caused colonies that were male specialists the prior year to switch to female production. Overall, a significantly greater proportion of food-supplemented colonies produced gynes, compared to control colonies. Moreover, food-supplemented colonies produced significantly larger workers and males (but not gynes), compared to those produced by control colonies. There was, however, no significant difference in the numerical productivity of food-supplemented and control colonies. We also measured the natural association between colony sex specialization and proximity to conifers, which typically harbor honeydew-bearing aphids (an important natural food source). In line with the view that resources play an important role for determining sex ratios in social insects, we found that female-producing colonies were significantly closer to conifers than were male-producing colonies.     

Observations on phytoplankton productivity in relation to hydrography in the Northern Adriatic

This work, carried out within the framework of the PRISMA II project, aims at evaluating the effects of the Po River flow on primary productivity, measured by C with in situ sample incubations. A total of four cruises was carried out in late winter and early summer (1996-1998) along transects from the coast offshore. In both seasons, the highest primary productivity was found in the most oligohaline stations. The effects of the Po River inputs were therefore clearly evident in the westernmost area, both in high productivity values and in the shape of productivity profiles. In late winter, extensive blooms of Skeletonema costatum and Pseudo-nitzschia delicatissima resulted in productivity values that were sometimes higher than in early summer. In early summer 1996, greatly reduced river flow clearly influenced productivity which was much lower than in 1997.     

Ecological and economic dynamics of the Shunde agricultural system under China's small city development strategy

The agricultural and industrial development of small cities is the primary environmental management strategy employed to make full use of extra labor in the rural areas of China. The ecological and economic consequences of this development strategy will affect over 100 million people and change the organization of the Chinese landscape. In this study, we examined the agricultural development of Shunde, a small city in Guangdong Province, over the period 1978 until 2000. Our analysis of the ecological and economic dynamics of the agricultural system revealed the dominant role of labor in the intensification of agricultural production, even though the use of fuels, fertilizers and machines also increased during this time. The Shunde agricultural system was examined from both biophysical or donor-based and human utility or receiver-based perspectives, using emergy and economic methods, respectively. After 22 years of urbanization, the Shunde agricultural system was still able to fill 96% of the local demand for agricultural products using only 6% of its total yield compared to using 14% of the total yield in 1978. Aquaculture developed quickly during the study period as grain production decreased. In 2000, the production of fish, pork, and vegetables accounted for 92% of the total emergy output of the system; however, the emergy buying power of the money received in exchange was lower than the emergy contained in the products exported. The excess emergy exported is the basis for a high quality diet delivered to city dwellers at a relatively low price. In the 1980s, the productivity of both land and labor increased; but after 1992 the productivity of labor decreased, causing the efficiency of the whole agricultural system to decrease. We recommend that processing plants be established for the main agricultural products of Shunde to decrease the emergy loss in trading and to increase employment. The effect of including monetized ecosystem services in the balance between the emergy delivered to the markets in agricultural products and the emergy buying power of the money received was to decrease the emergy gained by the Shunde agricultural system.     

Modeling soil and plant phosphorus within DSSAT

The crop models in the Decision Support System for Agrotechnology Transfer (DSSAT) have served worldwide as a research tool for improving predictions of relationships between soil and plant nitrogen (N) and crop yield. However, without a phosphorus (P) simulation option, the applicability of the DSSAT crop models in P-deficient environments is limited. In this study, a soil-plant P model integrated to DSSAT was described, and results showing the ability of the model to mimic wide differences in maize responses to P in Ghana are presented as preliminary attempts to testing the model on highly weathered soils. The model simulates P transformations between soil inorganic labile, active and stable pools and soil organic microbial and stable pools. Plant growth is limited by P between two concentration thresholds that are species-specific optimum and minimum concentrations of P defined at different stages of plant growth. Phosphorus stress factors are computed to reduce photosynthesis, dry matter accumulation and dry matter partitioning. Testing on two highly weathered soils from Ghana over a wide range of N and P fertilizer application rates indicated that the P model achieved good predictability skill at one site (Kpeve) with a final grain yield root mean squared error (RMSE) of 535 kg ha⁻¹and a final biomass RMSE of 507 kg ha⁻¹. At the other site (Wa), the RMSE was 474 kg ha⁻¹ for final grain yield and 1675 kg ha⁻¹ for final biomass. A local sensitivity analysis indicated that under P-limiting conditions and no P fertilizer application, crop biomass, grain yield, and P uptake could be increased by over 0.10% due to organic P mineralization resulting from a 1% increase in organic carbon. It was also shown that the modeling philosophy that makes P in a root-free zone unavailable to plants resulted in a better agreement of simulated crop biomass and grain yield with field measurements. Because the complex soil P chemistry makes the availability of P to plants extremely variable, testing under a wider range of agro-ecological conditions is needed to complement the initial evaluation presented here, and extend the use of the DSSAT-P model to other P-deficient environments.     

辽宁省滨海公路建设对沿线生态系统的影响

根据2006年10月野外调查数据及1998年的LANDSAT 5卫星影像解译的辽宁省植被类型数据,以辽宁省滨海公路沿线植被生态系统为研究对象,运用ARCVIEW3.3、ARCGIS9.0和FRAGSTATS3.3软件研究辽宁省滨海公路建设对沿线生态系统结构的影响,结果表明：①辽宁省滨海公路跨越2个纬度和5个经度,沿线主要植被类型以湿地生态系统和农业生态系统为主。②辽宁省滨海公路的建设对生态系统产生直接的切割,使景观更加破碎。③辽宁省滨海公路的建设直接破坏沿线植被生态系统（主要为50m缓冲区内）,损失总净初级生产量为25778.39 t/a,损失总生物量199274.2～284380.6t/a。建议采取一些必要的环境保护及生态恢复性措施。     

Quantitative relationships among phytoplankton body size classes and production processes in the North Adriatic frontal region

The variation patterns of phytoplankton standing crop and productivity in the North Adriatic frontal region and the relative importance of pico-, nano-, micro-phytoplankton are shown. Data of standing crop (chlorophyll a - Chl a ) and productivity ( 14 C assimilation) and PAR radiation ( w Em m 2 r s m 1 ) were collected during the four oceanographic cruises of the PRISMA II project. Average standing crop and productivity in the study area were 1.41 - 0.42 r mg r m m 3 Chl a and 1.23 - 0.37 r mg r C r m m 3 r h m 1 ; average assimilation number (P/B) was 0.872 - 0.589 r mg r C (mg-Chl a ) m 1 h m 1 and average photosynthetic efficiency (PE) was 0.020 - 0.054 (mg r C(mg-Chl a ) m 1 r h m 1 ) [ w Em m 2 r s m 1 ] m 1 . Phytoplankton biomass and productivity showed significant patterns of variation with the distance from the coast, with increasing depth and decreasing light intensity. The same patterns were shown by the three phytoplankton size classes. The spatio-temporal variations were significantly larger within the microplankton than within the pico- and nano-plankton size classes. Planktonic guilds were dominated by picoplankton, both as standing crop and productivity, in the northern stations (0.539 - 0.21 r mg r m m 3 Chl a and 0.572 - 0.25 r mg r C r m m 3 r h m 1 ) and in those more offshore, while microplankton was more important in the coastal and southern stations (0.727 - 0.58 r mg r m m 3 Chl a and 0.63 - 0.28 r mg r C r m m 3 r h m 1 ). In relative terms, picoplankton accounts for the 53% and 46% of biomass and primary production, while the microplankton account for the 43.6% and 48%. Assimilation number and photosynthetic efficiency did not show spatio-temporal variations but PE was inversely related with PAR radiation for all the size classes. Data suggest that the spatio-temporal patterns observed in this study are affected by the competitive relationships among body size classes in the phytoplankton guilds.     

Do biodiversity indices behave as expected from traits of constituent species in simulated scenarios?

It is believed that diversity of plant communities has a positive effect on their productivity. The benefits of diversity are described by “biodiversity indices”, comparing yield of mixtures with yields of monocultures of constituent species. These indices are supposed to capture also the main mechanisms leading to increased yield. We have constructed a spatially explicit individual based model, simulating even-aged stand development, and compared the behaviour of selected biodiversity indices (overyielding, selectivity and complementarity) with expectations based on life history traits of constituent species. The results are based on comparisons of two species mixtures with corresponding monocultures. We designed three scenarios of changes in the two species life history differentiation, and compared the behaviour of the indices with expectation based on it. In the first scenario, selectivity was driven by increasing size inequality of the two species, mostly in accordance with expectations. The second scenario presents increasing shade tolerance of the smaller species that increased complementarity, again mostly as expected. In the last scenario, shortening of length of stress tolerance of the weaker species surprisingly increased values of the biodiversity indices. For each setting, we varied sowing density and spatial pattern of the constituent species. The behaviour of the indices was influenced by both factors, but the effect of density was more pronounced. In particular, at high sowing densities, the most important interactions happened in the very early stages of mixture development, and the behaviour of the indices was often counter-intuitive.     

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.