Effect of combined nitrogen on dinitrogen fixation and productivity in Pisum sativum L. Inoculated with different strains of Rhizobium

This growth chamber study was designed to determine rates of nitrogen fixation, growth, productivity and concentrations of nitrogen and phosphorus during vegetative growth, flowering and the beginning of the fruiting and ripening period in Pisum sativum plants supplied with different concentrations of nitrate and nodulated by various strains of Rhizobium leguminosarum. Noninoculated control plants were grown under the same nutritional conditions. Nodulated and unnodulated plants responded differently to treatment. The effects of inoculation with Rhizobium and the nitrate treatments on the parameters of growth and nitrogen content varied with plant age. Although the presence of nitrate in the culture medium inhibited nodulation and acetylene reducing activity (ARA), the different Rhizobium strains used in the inoculations led to variations in tolerance to combined nitrogen.     

Application of a Physical Input–Output Table to Evaluate the Development and Sustainability of Continental Water Resources in Spain

Continental waters are complex resources in terms of a measurable physical quantity, and measuring them requires a good knowledge of total water availability. In this research, an accounting physical input–output table (PIOT) was applied to evaluate total water resources and gross annual availabilities at each stage of the natural-artificial water cycle. These stages are considered subsystems of a continental water resource system describing water transfers for an average year within 13 administrative basins of Spain. Water transfers between various subsystems are characterized by internal flows decreasing the water resource availabilities. The PIOT analysis establishes these internal flows, and the origins and final uses of the total resources for each subsystem. The input-output balance registered an unsustainable negative net accumulation in eight water basins. The PIOT analysis also allowed the calculation of significant indicators such as water resource developments (RDI) and their sustainable use (SUI). RDI and SUI demonstrate that groundwater is a critical resource affecting the environment (e.g., wetlands in the upper Guadiana) and the water supply (e.g., irrigation in the Segura basin). The results of this model suggest that above-/below-ground hydrological links are important when decisions have to be made in order to provide a satisfactory supply of water in Spain. The model integrates the different water basins under territorial criteria, and therefore it may be useful for the Spanish National Hydrological Plan.     

Expanding Kenya's protected areas under the Convention on Biological Diversity to maximize coverage of plant diversity

Biodiversity is highly valuable and critically threatened by anthropogenic degradation of the natural environment. In response, governments have pledged enhanced protected‐area coverage, which requires scarce biological data to identify conservation priorities. To assist this effort, we mapped conservation priorities in Kenya based on maximizing alpha (species richness) and beta diversity (species turnover) of plant communities while minimizing economic costs. We used plant‐cover percentages from vegetation surveys of over 2000 plots to build separate models for each type of diversity. Opportunity and management costs were based on literature data and interviews with conservation organizations. Species richness was predicted to be highest in a belt from Lake Turkana through Mount Kenya and in a belt parallel to the coast, and species turnover was predicted to be highest in western Kenya and along the coast. Our results suggest the expanding reserve network should focus on the coast and northeastern provinces of Kenya, where new biological surveys would also fill biological data gaps. Meeting the Convention on Biological Diversity target of 17% terrestrial coverage by 2020 would increase representation of Kenya's plant communities by 75%. However, this would require about 50 times more funds than Kenya has received thus far from the Global Environment Facility.     

Understanding and Integrating Local Perceptions of Trees and Forests into Incentives for Sustainable Landscape Management

We examine five forested landscapes in Africa (Cameroon, Madagascar, and Tanzania) and Asia (Indonesia and Laos) at different stages of landscape change. In all five areas, forest cover (outside of protected areas) continues to decrease despite local people's recognition of the importance of forest products and services. After forest conversion, agroforestry systems and fallows provide multiple functions and valued products, and retain significant biodiversity. But there are indications that such land use is transitory, with gradual simplification and loss of complex agroforests and fallows as land use becomes increasingly individualistic and profit driven. In Indonesia and Tanzania, farmers favor monocultures (rubber and oil palm, and sugarcane, respectively) for their high financial returns, with these systems replacing existing complex agroforests. In the study sites in Madagascar and Laos, investments in agroforests and new crops remain rare, despite government attempts to eradicate swidden systems and their multifunctional fallows. We discuss approaches to assessing local values related to landscape cover and associated goods and services. We highlight discrepancies between individual and collective responses in characterizing land use tendencies, and discuss the effects of accessibility on land management. We conclude that a combination of social, economic, and spatially explicit assessment methods is necessary to inform land use planning. Furthermore, any efforts to modify current trends will require clear incentives, such as through carbon finance. We speculate on the nature of such incentive schemes and the possibility of rewarding the provision of ecosystem services at a landscape scale and in a socially equitable manner.     

A Numerical Model for the Transport of Chromium and Fine Sediments

A mathematical model which represents the transport processes of heavy metals and fine sediments in a fluvial stream was developed. The model consists of a three-equation system: the first one for total chromium concentration in the water column, C _Tw, the second one for total suspended sediment concentration, S _w, and the third one for chromium concentration in bed sediments, r. The third equation represents the chromium exchange between the water column and bed sediments by two processes: diffusion of soluble chromium and erosion/deposition of chromium sorbed to sediments. The basic assumption of the model is the instantaneous equilibrium. The main parameters are the partition coefficients in the water column and bed sediments, the depth of the active bed sediment layer, and the mass transfer coefficient between the water column and sediment pore water. The numerical model approximates the equations of advection–dispersion for chromium in water and suspended sediments by using a Eulerian third-order scheme. Numerical vs. analytical solutions were considered satisfactory for different initial, boundary, and sedimentological conditions. In order to estimate the impact of a chromium side discharge, the model was implemented for the Salado River in a reach of 65.6-km long (Santa Fe, Argentina). The results showed the effect of chromium discharge on almost the whole reach, then the vulnerability of the water quality in the Salado River when the flow was low was evidenced. When comparing the computed and measured results, the former showed a reasonable representation of the presence of chromium in water and bed sediments.     

Risk assessment of soils contaminated by mercury mining, Northern Spain

Analytical results of soil samples taken in three different mercury mining sites in Northern Spain are studied to assess the potential adverse health effects of the exposure to trace elements associated with the mining process. Doses contacted through ingestion and inhalation and the dose absorbed through the skin were calculated using USEPA's exposure parameters and the US Department of Energy's toxicity values. The results of the risk assessment indicate that the highest risk is associated with ingestion of soil particles and that the trace element of major concern is arsenic, the exposure to which results in a high cancer risk value for all the sites ranging from 3.3 × 10(-5) to 3.6 × 10(-3), well above the 1 × 10(-5) probability level deemed unacceptable by most regulatory agencies. Regarding non-cancer effects, exposure to polluted soils yields an aggregate hazard index above the threshold value of 1 for all three sites, with As and Hg as the main contributors. Risk assessment has proven to be a very useful tool to identify the contaminants and exposure pathways of most concern in the soils from metal mining sites, as well as to categorize them in terms of action priority to ensure fitness for use.     

House sparrows selectively eject parasitic conspecific eggs and incur very low rejection costs

Most host species of obligate interspecific brood parasites are under strong selection because such parasitism, e.g., that involving evictor nestmates, is highly costly. Egg rejection is one of the most efficient host defences against avian brood parasites. Many hosts have thus evolved egg-recognition ability and rejection behaviour. However, this defensive mechanism has not evolved in most species where only intraspecific brood parasitism occurs, probably because (1) the eggs of conspecific females are very similar in appearance, making egg rejection less likely to emerge, and (2) such parasitism is frequently less costly than interspecific parasitism. Using a captive population of house sparrows (Passer domesticus) with a low breeding density, we here provide new evidence showing that this species actually has a fine capacity to discriminate conspecific eggs and to eject them (44.2% of foreign eggs ejected) while incurring very low rejection costs (4.2% of own eggs ejected). This result contradicts those previously found in high-density house sparrow populations in which very high rejection costs and very high clutch desertion rates were reported, probably as a consequence of intraspecific competition and infanticide provoked by the high breeding density. The house sparrow has only rarely been reported as the host of an interspecific brood parasite, which implies that it is a newly described example of an altricial species in which egg ejection has evolved and is maintained in response to intraspecific brood parasitism.     

Mangrove mapping in Ecuador: The impact of shrimp pond construction

A cooperative mangrove mapping project between the Ecuadorian Center for Remote Sensing (CLIRSEN) and the University of Delaware was begun in August 1982. The objectives of the project were to create historical maps of mangrove ecosystem extent and change, while transferring aerial photographic interpretation techniques to Ecuadorian personnel. The result of this cooperation was a series of three 125,000 scale maps of historical mangrove extent and change from 1966 to 1982 in the southern Gulf of Guayaquil. This multitemporal study showed a 16% decrease in mangrove extent and a 27% increase in shrimp pond development. If these rates of change prevail into the future, mangroves in Ecuador will reach parity with shrimp ponds in 1984 and completely disappear by mid-1990. Recognizing the significance of this loss to shellfish and fish production along the coast, Ecuadorian scientists at CLIRSEN have subsequently initiated a nationwide mangrove mapping program to create a historical base for future mangrove management strategies.     

Cognitive skills and bacterial load: comparative evidence of costs of cognitive proficiency in birds

Parasite-mediated selection may affect the evolution of cognitive abilities because parasites may influence development of the brain, but also learning capacity. Here, we tested some predictions of this hypothesis by analyzing the relationship between complex behaviours (feeding innovations (as a measure of behavioural flexibility) and ability to detect foreign eggs in their nests (i.e. a measure of discriminatory ability)) and abundance of microorganisms in different species of birds. A positive relationship would be predicted if these cognitive abilities implied a larger number of visited environments, while if these skills favoured detection and avoidance of risky environments, a negative relationship would be the prediction. Bacterial loads of eggshells, estimated for mesophilic and potentially pathogenic bacteria (i.e. Enterococcus, Staphylococcus and Enterobacteriaceae), were used as a surrogate of probability of contact with pathogenic bacteria. We found that bird species with higher feeding innovation rates and rejection rates of experimental brood parasitic eggs had higher density of bacteria on their eggshells than the average species. Since the analysed groups of microorganisms include pathogenic bacteria, these results suggest that both feeding innovation and ability to recognize foreign eggs are costly and highlight the importance of parasite-mediated selection in explaining the evolution of cognitive abilities in animals.