Inbreeding and local mate competition in the ant Cardiocondyla batesii

The ant species Cardiocondyla batesii is unique in that, in contrast to all other ant species, both sexes are flightless. Female sexuals and wingless, ergatoid males mate in the nest in autumn and young queens disperse on foot to found their own colonies in spring. The close genetic relatedness between queens and their mates (r_qm=0.76±SE 0.12) and the high inbreeding coefficient (F=0.55; 95%CI 0.45–0.65) suggest that 83% of all matings are between brothers and sisters. As expected from local mate competition theory, sex ratios were extremely female biased, with more than 85% of all sexuals produced being young queens. Despite the common occurrence of inbreeding, we could not detect any adult diploid males. Though the probability of not detecting multiple mating was relatively high, at least one-third of all queens in our sample had mated more than once. Multiple mating to some extent counteracts the effects of inbreeding on worker relatedness (r_ww=0.68±SE 0.05) and would also be beneficial through decreasing diploid male load, if sex was determined by a single locus complementary system.Communicated by L. Sundström     

Spread of metals through an invertebrate food chain as influenced by a plant that hyperaccumulates nickel

Summary. Hyperaccumulation of metals in the shoot system of plants is uncommon, yet taxonomically and geographically widespread. It may have a variety of functions, including defense against herbivores. This study investigated the effects of hyperaccumulation on metal concentrations across trophic levels. We collected plant material, soil, and invertebrates from Portuguese serpentine outcrops whose vegetation is dominated by the nickel hyperaccumulator Alyssum pintodasilvae. Samples were analyzed for nickel, chromium, and cobalt. Grasshoppers, spiders, and other invertebrates collected from sites where A. pintodasilvae was common had significantly elevated concentrations of nickel, compared to nearby sites where this hyperaccumulator was not found. Chromium and cobalt, occurring in high concentrations in the serpentine soil but not accumulated by A. pintodasilvae, were not elevated in the invertebrates. Therefore, it appears likely that a flux of nickel to herbivore and carnivore trophic levels is specifically facilitated by the presence of plants that hyperaccumulate this metal. The results may be relevant to the development of phytoremediation and phytomining technologies, which use plants to extract metals from the soil. Reveived 22 August 2002; accepted 2 April 2003. R1D=" Correspondence to: A. J. Pollard, e-mail:joe.pollard@furman.edu     

Allelopathic potential of Cistus ladanifer chemicals in response to variations of light and temperature

Summary. Earlier studies have demonstrated the allelopathic potential of the exudate of Cistus ladanifer leaves, and have identified the compounds responsible for the effect. It is here shown that the effect of each of these compounds and their interactions on germination and seedling development varies depending on the light and temperature parameters to which they are subjected. The allelochemicals show a fairly heterogeneous response when studied separately, there being no general pattern to the behaviour. When they act conjointly, however, their activity is enhanced by high temperatures, and the greatest phytotoxicity in inhibiting both germination and seedling development is attained with high temperatures and long photoperiods. These results suggest that the environmental factors temperature and photoperiod may alter the allelopathic effect of Cistus ladanifer. Received 5 December 2001; accepted 11 March 2002.     

Recycled and virgin plastic carriers in hybrid reactors for wastewater treatment.

The reduction of organic and nitrogen pollution of wastewater was investigated in two hybrid reactors and compared with the reduction obtained by using a conventional activated sludge reactor (ASR) run as a control. Both HR-1 and HR-2 were activated sludge systems where a low-density carrier, P1 (polyethylene) for HR-1 and P2 (recycled plastics) for HR-2, was added. Firstly, the three reactors were operated at 10 days Suspended Solid Retention Time (SRT(SS)), leading to a complete nitrification. Secondly, the SRT(SS) for each reactor was lowered to 3 days. Nitrification was lost for the ASR but remained complete for HR's. Respirometric techniques were used to measure fixed or suspended biomass activities for heterotrophic and autotrophic biomass. More than 90% of the autotrophic activity was found on the supports whatever the SRT(SS) used. The results may underline the role of the carrier geometry or surface characteristics on the autotrophic/heterotrophic microorganism distribution.     

Geomorphological consequences of fraquent and infrequent rainfall and hydrological events in Pyrennez Mountains of Spain

Various aspects of pluviometric andhydrological events have been studiedworldwide, one of which is the geomorphichazards as the intensity of the eventsexceeds various geomorphic thresholds.During the last few years, rainstorms ofdifferent intensities have occurred in theCentral Spanish Pyrenees, including one ofexceptional character. Large, historicaldebris flows have been studied, as well asthe actual sediment transport in smallexperimental catchments. This study showsthat during the most frequent eventssuspended sediment transport is the commongeomorphic process. Bedload is mobilizedseveral times per year while small rockavalanches and channelized debris flowshave a return period of at least 5 years.Hillslope debris flows are triggered byrainfall events with a 25–30 year returnperiod. Reactivation of large, deep massmovements is linked to rainfalls of around100 year return period (between 130 and160 mm in 24 hours). Catastrophicgeomorphic processes occur whenprecipitation exceeds a 100 year returnperiod, as was the case of the Biescascampsite disaster. Geomorphic processestriggered by intense rainfall events havecaused major damage and human disastersbut the hazards have been reduced by theintroduction of several control measures,including reforestation, the constructionof check-dams, canalization of riversegments and improved flood forecasting.     

The leachate composition of an old waste dump connected to groundwater: Influence of the reclamation works

This study has been carried out in an uncontrolled dump in the suburbs of Buenos Aires, Argentina. This dump still contains solid wastes of different types in direct contact with the human consumption aquifer. After 18 years of overturning the dump was closed in 1992, and the reclamation works started.Three leachate samplings were carried out in three different zones of the dump, selected according to the topography, the age of residues and the degree of water contact. These samplings were done before the reclamation works, at the end, and four months after they were finished. Several chemical parameters, including heavy metals in solid and dissolved fractions, were analyzed.Multivariate analysis (PCA) was performed to help to understand the effects of the labors on leachate composition. The works could be responsible for a temporal increase of dissolved heavy metals and several chemical variables in the leachate. At the sites of the dump where the modifications were carried out, the levels of some elements analyzed recovered their former values a few months after the reclamations works. At the farthest site, the impact and recovery effects of the works on leachate composition, were delayed.     

Sugarcane straw management for bioenergy: effects of global warming on greenhouse gas emissions and soil carbon storage

Mitigation and Adaptation Strategies for Global Change - Global warming can intensify the soil organic matter (SOM) turnover, damaging soil health. Crop residues left on the soil are important to...     

Interdisciplinary studies on the technical and economic feasibility of deep underground coal gasification with CO<Subscript>2</Subscript> storage in bulgaria

This paper presents the outcome of a feasibility study on underground coal gasification (UCG) combined with direct carbon dioxide (CO₂) capture and storage (CCS) at a selected site in Bulgaria with deep coal seams (>1,200 m). A series of state-of-the-art geological, geo-mechanical, hydrogeological and computational models supported by experimental tests and techno-economical assessments have been developed for the evaluation of UCG-CCS schemes. Research efforts have been focused on the development of site selection requirements for UCG-CCS, estimation of CO₂ storage volumes, review of the practical engineering requirements for developing a commercial UCG-CCS storage site, consideration of drilling and completion issues, and assessments of economic feasibility and environmental impacts of the scheme. In addition, the risks of subsidence and groundwater contamination have been assessed in order to pave the way for a full-scale trial and commercial applications. The current research confirms that cleaner and cheaper energy with reduced emissions can be achieved and the economics are competitive in the future European energy market. However the current research has established that rigorous design and monitor schemes are essential for productivity and safety and the minimisation of the potential environmental impacts. A platform has been established serving to inform policy-makers and aiding strategies devised to alleviate local and global impacts on climate change, while ensuring that energy resources are optimally harnessed.     

Influence of tree species composition,thinning intensity and climate change on carbon sequestration in Mediterranean mountain forests: a case study using the CO2Fix model

Prediction of future forest carbon (C) stocks as influenced by forest management and climate is a crucial issue in the search for strategies to mitigate and adapt to global change. It is hard to quantify the long-term effect of specific forest practices on C stocks due to the high number of processes affected by forest management. This work aims to quantify how forest management impacts C stocks in Mediterranean mountain forests based on 25 combinations of site index, tree species composition and thinning intensity in three different climate scenarios using the CO2Fix v.3.2 model Masera et al. (Ecol Modell 164:177–199, 2003). The study area is an ecotonal zone located in Central Spain, and the tree species are Scots pine (Pinus sylvestris L.) and Pyrenean oak (Quercus pyrenaica Willd.). Our results show a strong effect of tree species composition and a negligible effect of thinning intensity. Mixed stands have the highest total stand C stocks: 100 % and 15 % more than pure oak and pine stands respectively, and are here suggested as a feasible and effective mitigation option. Climate change induced a net C loss compared to control scenarios, when reduction in tree growth is taken into account. Mixed stands showed the lowest reduction in forest C stocks due to climate change, indicating that mixed stands are also a valid adaptation strategy. Thus converting from pure to mixed forests would enhance C sequestration under both current and future climate conditions.     

Valorization of EVA waste from footwear industry as natural aggregates substitutes in mortar: the effect of granulometry

Journal of Material Cycles and Waste Management - The increased consumption of polymers and the consequent generation of waste requires the development of efficient recycling strategies. In this...