Feocromocitoma suprarrenal en un paciente hipertenso con crisis hipertensiva / Adrenal pheochromocytoma in a hypertensive patient with a hypertensive crisis

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Interannual variations of soil organic carbon fractions in unmanaged volcanic soils (Canary Islands, Spain).

The stability over time of the organic C stocked in soils under undisturbed ecosystems is poorly studied, despite being suitable for detecting changes related to climate fluctuations and global warming. Volcanic soils often show high organic C contents due to the stabilization of organic matter by short-range ordered minerals or Al-humus complexes. We investigated the dynamics of different organic C fractions in volcanic soils of protected natural ecosystems of the Canary Islands (Spain) to evaluate the stability of their C pools. The study was carried out in 10 plots, including both undisturbed and formerly disturbed ecosystems, over two annual periods. C inputs to (litterfall) and outputs from (respiration) the soil, root C stocks (0-30 cm), soil organic C (SOC) fractions belonging to C pools with different degrees of biogeochemical stability -total oxidisable C (TOC), microbial biomass C (MBC), water soluble C (WSC), hot-water extractable C (HWC), humic C (HSC), - and total soil N (TN) (at 0-15 and 15-30 cm) were measured seasonally.A statistically significant interannual increase in CO(2) emissions and a decrease in the SOC, mainly at the expense of the most labile organic forms, were observed, while the root C stocks and litterfall inputs remained relatively constant over the study period. The observed changes may reflect an initial increase in SOC resulting from low soil respiration rates due to drought during the first year of study. The soils of nearly mature ecosystems were more apparently affected by C losses, while those undergoing the process of active natural regeneration exhibited disguised C loss because of the C sequestration trend that is characteristic of progressive ecological succession.

Mineralization rate of eroded organic C in Andosols of the Canary Islands.

The aim of this paper is to determine the biological dynamism of the organic C forms bonded to soil particles mobilized by water erosion in Andosols of the Canary Islands, to evaluate their susceptibility towards mineralization processes and the role of sediments as sources or sinks of atmospheric CO(2) in these soils. The study was carried out in Tenerife (Canary Islands) on three 200 m(2) experimental plots of the RESEL Programme on silic Andosols under forest, 3 years after being subjected to clear-cutting. Eroded sediments were collected for analysis from five significant winter rainfall episodes. For each event, samples of surface (0-5 cm) soil in situ were also collected. CO(2)-C was measured by incubation in all the samples, as well as microbial biomass-linked C. The results obtained show an enrichment in the eroded sediments of microbial biomass (7.5+/-1.6 g kg(-1) vs. 3.8+/-1.5 g kg(-1)) and of potentially mineralizable C (1419 mg CO(2)-C kg(-1) vs. 386 mg CO(2)-C kg(-1)). In addition, there was twice as much mineralization of C compounds in eroded sediments as in the soil surface horizon.

A biological quality index for volcanic Andisols and Aridisols (Canary Islands, Spain): variations related to the ecosystem degradation.

The aim of this work is to identify indicators of biological activity in soils from the Canary Islands, by studying the variation of selected biological parameters related to the processes of deforestation and accelerated soil degradation affecting the Canarian natural ecosystems. Ten plots with different degrees of maturity/degradation have been selected in three typical habitats in the Canary Islands: laurel forest, pine forest and xerophytic scrub with Andisols and Aridisols as the most common soils. The studied characteristics in each case include total organic carbon, field soil respiration, mineralized carbon after laboratory incubation, microbial biomass carbon, hot water-extractable carbon and carboxymethylcellulase, beta-d-glucosidase and dehydrogenase activities. A Biological Quality Index (BQI) has been designed on the basis of a regression model using these variables, assuming that the total soil organic carbon content is quite stable in nearly mature ecosystems. Total carbon in mature ecosystems has been related to significant biological variables (hot water-extractable carbon, soil respiration and carboxymethylcellulase, beta-d-glucosidase and dehydrogenase activities), accounting for nearly 100% of the total variance by a multiple regression analysis. The index has been calculated as the ratio of the value calculated from the regression model and the actual measured value. The obtained results show that soils in nearly mature ecosystems have BQI values close to unit, whereas those in degraded ecosystems range between 0.24 and 0.97, depending on the degradation degree.

Temporal evolution of organic carbon and nitrogen forms in volcanic soils under broom scrub affected by a wildfire.

The evolution of total N, total oxidizable C, water-soluble NH(4)(+)-N, exchangeable NH(4)(+)-N and soluble NO(3)(-)-N was studied in Canarian volcanic soils under mountainous legume scrub affected by a wildfire by June 2003. Three systematic soil samplings in the burned area and in neighbouring non-burned sampling points were carried out 3, 7 and 12 months after the fire event. The results showed an important mobilization of N (as total N and soluble and exchangeable NH(4)(+)-N) in the soil within the burned area at short term, with a simultaneous depletion of nitrates. Later on, the water-soluble NH(4)(+)-N levels remained nearly constant along the study period in the burned area, whereas the exchangeable NH(4)(+) decreased progressively. Nitrates were found to increase inside and outside the burned area, but the increase rate was much higher for the burned samples. Total N fluctuated along the year, although its levels were generally higher in the burned area. However, such a response pattern of N to fire in this environment was insufficient to prompt the recovery of the plant cover.