Carbon balance of the taiga forest within Alaska: present and future

Forest biomass, rates of production, and carbon dynamics are a function of climate, plant species present, and the structure of the soil organic and mineral layers. Inventory data from the U.S. Forest Service (USFS) Inventory Analysis Unit was used to develop estimates of the land area represented by the major overstory species at various age-classes. The CENTURY model was then used to develop an estimate of carbon dynamics throughout the age se- quence of forest development for the major ecosystem types. The estimated boreal forest area in Alaska, based on USFS inventory data is 17 244 098 ha. The total aboveground biomass within the Alaska boreal forest was estimated to be 815 330 000 Mg. The CENTURY model estimated maximum net ecosystem production (NEP) at 137, 88, 152, 99, and 65 g·m–2·year–1 for quaking aspen (Populus tremuloides Michx.), paper birch (Betula papyrifera Marsh.), balsam poplar (Populus balsamifera L.), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Mill.) BSP) forest stands, respectively. These values were predicted at stand ages of 80, 60, 41, 68, and 100 years, respec- tively. The minimum values of NEP for aspen, paper birch, balsam poplar, white spruce, and black spruce were –171, –166, –240, −300, and –61 g·m–2·year–1 at the ages of 1, 1, 1, 1, and 12, respectively. NEP became positive at the ages of 14, 19, 16, 13, and 34 for aspen, birch, balsam poplar, white spruce, and black spruce ecosystems, respectively. A 5°C increase in mean annual temperature resulted in a higher amount of predicted production and decomposition in all ecosystems, resulting in an increase of NEP. We estimate that the current vegetation absorbs approximately 9.65 Tg of carbon per year within the boreal forest of the state. If there is a 5°C increase in the mean annual temperature with no change in precipitation we estimated that NEP for the boreal forest in Alaska would increase to 16.95 Tg of carbon per year

Cutaneous Nocardia asteroides infection of nontraumatic origin Infecção cutânea de origem não traumática por Nocardia asteroides

This paper reports a case of cutaneous infection of nontraumatic origin caused by Nocardia asteroides in a hospitalized patient with chronic obstructive pulmonary disease. Diagnosis was established by direct and histological examination, cultures from exudate and biopsy specimen. We discuss the classification of clinical forms of Nocardia infections affecting the skin.<br>É relatado um caso de infecção cutânea de origem não traumática por Nocardia asteroides em paciente hospitalizado com doença broncopulmonar obstrutiva crônica. O diagnóstico foi feito pelo exame direto e histológico e culturas do exsudato e fragmento de biópsia. É discutida a classificação das formas clínicas das infecções por Nocardia que afetam a pele