Importance of indirect nitrous oxide emissions at the field, farm and catchment scale

Direct and indirect nitrous oxide (N₂O) emissions and leaching losses from an intensively managed grazed pasture in the Ythan catchment, Aberdeenshire, UK, were measured and compared over a 17-month period. Simultaneous measurements of farm-wide leaching losses of N₂O were also made and catchment-wide fluxes were estimated from existing N leaching data. The relative importance of direct and indirect N₂O fluxes at the field, farm and catchment scale was then assessed. At the field scale we found that direct N₂O emissions were low (1.2 kg N ha⁻¹ year⁻¹, 0.6% of N input) with indirect N₂O emissions via drainage waters comprising a significant proportion (25%) of total N₂O emissions. At the whole-farm scale, the N₂O-N emission factor (0.003) for leached NO₃-N (EF_5-g) was in line with the IPCC's recent downward revision. At the catchment scale, a direct N₂O flux of 1.9 kg N ha⁻¹ year⁻¹ and an indirect flux of 0.06 kg N₂O-N ha⁻¹ year⁻¹ were estimated. This study lends further support to the recent downward revision of the IPCC emission factor for N₂O arising from leached N in surface and ground waters (EF_5-g) and highlights the need for multiple point sampling to ensure that the importance of indirect N₂O losses via drainage waters is not misrepresented at the farm and catchment scales.     

Dengue epidemics in the Caribbean-temperature indices to gauge the potential for onset of dengue

The seasonality, patterns and the climate associations of the reported cases of dengue in the Caribbean were studied by analyzing the annual and monthly variability of reported cases as well as those of climate parameters (temperature and precipitation). More attention was given to Trinidad and Tobago, Barbados, and Jamaica, as those countries contributed mostly to the reported cases. The data were for the period 1980–2003. Results showed that the incidence of dengue in the Caribbean were higher in the last decade (1990s) compared to that in the previous decade (1980s). The yearly patterns of dengue exhibited a well-defined seasonality. The epidemics appeared to occur in the later half of the year following onset of rainfall and increasing temperature. Analysis revealed that the association of the epidemics with temperature was stronger, especially in relation to the onset of dengue, and the probability of epidemics was high during El Niño periods. In years with early warmer periods epidemics appeared to occur early, which was a scenario more probable in the year after an El Niño (an El Niño + 1 year). Indices linked to temperatures that are useful for gauging the potential for onset of dengue were examined. An index based on a moving average temperature (MAT) appeared to be effective in gauging such potential and its average (AMAT) signals a threshold effect. MAT index has potential use in adaptation and mitigation strategies.     

Selection of both habitat and genes in specialized and endangered caribou

Genetic mechanisms determining habitat selection and specialization of individuals within species have been hypothesized, but not tested at the appropriate individual level in nature. In this work, we analyzed habitat selection for 139 GPS-collared caribou belonging to 3 declining ecotypes sampled throughout Northwestern Canada. We used Resource Selection Functions comparing resources at used and available locations. We found that the 3 caribou ecotypes differed in their use of habitat suggesting specialization. On expected grounds, we also found differences in habitat selection between summer and winter, but also, originally, among the individuals within an ecotype. We next obtained Single Nucleotide Polymorphisms (SNPs) for the same caribou individuals, we detected those associated to habitat selection, and then identified genes linked to these SNPs. These genes had functions related in other organisms to habitat and dietary specializations, and climatic adaptations. We therefore suggest that individual variation in habitat selection was based on genotypic variation in the SNPs of individual caribou, indicating that genetic forces underlie habitat and diet selection in the species. We also suggest that the associations between habitat and genes that we detected may lead to lack of resilience in the species, thus contributing to caribou endangerment. Our work emphasizes that similar mechanisms may exist for other specialized, endangered species.