Methane flux was measured in situ in the Alaska Arctic tundra to assess the magnitude and controls on spatial variability of emissions. A total of 122 measurements were made at 57 spatially independent sites across the Alaska North Slope during the summer of 1987. Variability in rates of emissions was similar in magnitude on local and regional scales, ranging from 0 to 286.5 mg CH4 m−2 d−1 overall and often varying across two orders of magnitude within 0.5‐m distances. Primary control on rates of emissions was determined by the substrate and the position of the water table relative to the surface. Secondary controls were defined by the substrate temperature and the type and quantity of vegetation participating in the plant‐mediated release of CH4 to the atmosphere. Emission rates in the Arctic Foothills ranged from 0.2 mg CH4 m−2 d−1 for tussock tundra to 55.3 mg CH4 m−2 d−1 over wet meadows. Within the Arctic Coastal Plain, rates of emissions were highest on inundated terrestrial sites (72.2 mg CH4 m−2 d−1), decreasing nearly 12 fold on comparable sites where the water table was 5 cm or more below the surface (6.1 mg CH4 m−2 d−1). Emission rates increased linearly with substrate temperatures at 10‐cm depth, increasing nearly ninefold over the 6°C temperature range observed. Plant mediated release of CH4 to the atmosphere was directly proportional to green leaf area and represented 92–98% of the total emission rates over vegetated sites. Comparisons between boreal studies reflect similarities in environmental controls on emissions at local‐to‐regional scales and demonstrate the sensitivity of regional to global estimates to sampling bias. These results suggest that current published emissions rates may have overestimated the contribution of boreal ecosystems to the global CH4 budget by several fold.

Boreal peatlands occupy about 1.14 x 106 km2 in North America. Fires can spread into peatlands, burning the biomass, and if moisture conditions permit, burning into the surface peat. Charred layers in peat sections reveal that historically bogs in the subhumid continental regions and permafrost peatlands of the subarctic regions have been the most susceptible to fires. Fire return periods were estimated from the numbers and ages of the charred peat layers. Based on average moisture conditions of the surface, about 0.5% of the peatlands (6420 km2) can be expected to burn annually, but the surface peat layer is expected to burn only in a small portion of this area (1160 km2). Carbon losses from aboveground combustion, in the form of CO2, CO, CH4, and nonmethane hydrocarbons, are the highest in forested swamps at 2.03 Tg C ·year-1. Carbon losses due to combustion of surface peat is the highest in the driest peatlands (e.g., raised bogs underlain by permafrost) at 5.82 Tg C ·year-1. The total estimated carbon release due to aboveground combustion is 2.92 Tg C ·year-1 and due to belowground peat combustion is 6.72 Tg C ·year-1. These estimates of direct carbon emissions to the atmosphere due to wildfires suggest a globally significant, but relatively small source in contrast with emissions from wildfires in uplands. The effects of a possible climate change are expected to be most prominent in the continental and northern parts of North America. A lower water table would result in increased CO2 but decreased CH4 emissions from the peatlands. A drier climate may mean increased fire frequency and intensity, resulting in more fires in peatlands and an increased probability of the fires consuming part of the peat.Key words: fire, peatlands, carbon, boreal, permafrost, gas flux.

No abstract

Abstract. In this study, we evaluate the effect of participatory Ecohealth interventions on domestic reinfestation of the Chagas disease vector Triatoma dimidiata after village-wide suppression of the vector population using a residual insecticide. The study was conducted in the rural community of La Brea, Guatemala between 2002 and 2009 where vector infestation was analyzed within a spatial data framework based on entomological and socio-economic surveys of homesteads within the village. Participatory interventions focused on community awareness and low-cost home improvements using local materials to limit areas of refuge and alternative blood meals for the vector within the home, and potential shelter for the vector outside the home. As a result, domestic infestation was maintained at 3% and peridomestic infestation at 2% for 5 years beyond the last insecticide spraying, in sharp contrast to the rapid reinfestation experienced in earlier insecticide only interventions.

No abstract