The role of historical fire disturbance in the carbon dynamics of the pan-boreal region : a process-based analysis

Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): G02029, doi:10.1029/2006JG000380.Wildfire is a common occurrence in ecosystems of northern high latitudes, and changes in the fire regime of this region have consequences for carbon feedbacks to the climate system. To improve our understanding of how wildfire influences carbon dynamics of this region, we used the process-based Terrestrial Ecosystem Model to simulate fire emissions and changes in carbon storage north of 45°N from the start of spatially explicit historically recorded fire records in the twentieth century through 2002, and evaluated the role of fire in the carbon dynamics of the region within the context of ecosystem responses to changes in atmospheric CO2 concentration and climate. Our analysis indicates that fire plays an important role in interannual and decadal scale variation of source/sink relationships of northern terrestrial ecosystems and also suggests that atmospheric CO2 may be important to consider in addition to changes in climate and fire disturbance. There are substantial uncertainties in the effects of fire on carbon storage in our simulations. These uncertainties are associated with sparse fire data for northern Eurasia, uncertainty in estimating carbon consumption, and difficulty in verifying assumptions about the representation of fires that occurred prior to the start of the historical fire record. To improve the ability to better predict how fire will influence carbon storage of this region in the future, new analyses of the retrospective role of fire in the carbon dynamics of northern high latitudes should address these uncertainties.Funding for this study was provided by grants from the National Science Foundation Biocomplexity Program (ATM-0120468) and Office of Polar Programs (OPP-0531047 and OPP- 0327664); the National Aeronautics and Space Administration Land Cover Land Use Change Program (NAF-11142) and North America Carbon Program (NNG05GD25G); the Bonanza Creek LTER (Long-Term Ecological Research) Program (funded jointly by NSF grant DEB-0423442 and USDA Forest Service, Pacific Northwest Research Station grant PNW01- JV11261952-231); and the U.S. Geological Survey

The multiplicity of malaria transmission: a review of entomological inoculation rate measurements and methods across sub-Saharan Africa

Plasmodium falciparum malaria is a serious tropical disease that causes more than one million deaths each year, most of them in Africa. It is transmitted by a range of Anopheles mosquitoes and the risk of disease varies greatly across the continent. The "entomological inoculation rate" is the commonly-used measure of the intensity of malaria transmission, yet the methods used are currently not standardized, nor do they take the ecological, demographic, and socioeconomic differences across populations into account. To better understand the multiplicity of malaria transmission, this study examines the distribution of transmission intensity across sub-Saharan Africa, reviews the range of methods used, and explores ecological parameters in selected locations. It builds on an extensive geo-referenced database and uses geographical information systems to highlight transmission patterns, knowledge gaps, trends and changes in methodologies over time, and key differences between land use, population density, climate, and the main mosquito species. The aim is to improve the methods of measuring malaria transmission, to help develop the way forward so that we can better assess the impact of the large-scale intervention programmes, and rapid demographic and environmental change taking place across Africa

Sea-Land Total Ozone Differences from TOMS: GHOST Effect

Mean global TOMS (Total Ozone Mapping Spectrometer) ozone data, averaged in time, reveals persistent year-to-year differences in total ozone between continents and oceans. This feature has been named GHOST (global hidden ozone structures from TOMS). During Northern Hemisphere summer it can be seen within the latitudinal belt between 40°S and 50°N. The most pronounced land-sea difference in total ozone with values of up to 18 Dobson units is observed between latitudes 35°N and 40°N. The gradients associated with the coastlines are stronger in summer, when transient planetary wave activity decreases, but is still observable in the winter period. The Iberian Peninsula has been selected as a case study to examine the effect of each possible contribution quantitatively. It has been found that the truncation of the lower tropospheric column due to the topography explains 26% of the land-sea differences, while permanent differences in tropopause height distribution can account for a further 8%. After these “corrections” other structures remain. Additional contributions due to the TOMS total ozone retrieval algorithm artifact (absorbing aerosol distribution) are also explored. After considering the optical depths and absorbance of aerosols above the Iberian Peninsula, the remaining 66% is compatible with the presence of UV-absorbing aerosols whose effects may not be correctly accounted for in the TOMS retrieval algorithm