Peatland Initiation, Carbon Accumulation, and 2 ka Depth in the James Bay Lowland and Adjacent Regions

Copyright © 2014 University of Colorado at Boulder, Institute of Arctic and Alpine ResearchPeatlands surrounding Hudson and James Bays form the second largest peatland complex in the world and contain major stores of soil carbon (C). This study utilized a transect of eight ombrotrophic peat cores from remote regions of central and northern Ontario to quantify the magnitude and rate of C accumulation since peatland initiation and for the past 2000 calendar years before present (2 ka). These new data were supplemented by 17 millennially resolved chronologies from a literature review covering the Boreal Shield, Hudson Plains, and Taiga Shield bordering Hudson and James Bays. Peatlands initiated in central and northern Ontario by 7.8 ka following deglaciation and isostatic emergence of northern areas to above sea level. Total C accumulated since inception averaged 109.7 ± (std. dev.) 36.2 kg C m–2. Approximately 40% of total soil C has accumulated since 2 ka at an average apparent rate of 20.2 ± 6.9 g C m–2 yr–1. The 2 ka depths correlate significantly and positively with modern gridded climate estimates for mean annual precipitation, mean annual air temperature, growing degree-days > 0 °C, and photosynthetically active radiation integrated over days > 0 °C. There are significantly shallower depths in permafrost peatlands. Vertical peat accumulation was likely constrained by temperature, growing season length, and photosynthetically active radiation over the last 2 ka in the Hudson Bay Lowlands and surrounding regions.US National Science Foundatio

Effects of Low-Dose Aspirin on Vascular Sensitivity to Angiotensin II and on 24 Hours Arterial Blood Pressure in Pregnancy

The angiotensin sensitivity test (AST) was performed in a group of 40 high risk pregnant women before and after oral administration of low doses of aspirin (ASA) (100 mg). AST performed before ASA characterized two groups of patients: 18 with positive AST (AST+) (effective pressor dose (EPD) = 6.91\ub11.69 (mean \ub1 S.D.) ng/Kg/min of angiotensin II (A II)) and 22 with negative AST (AST-) (EPD = 22.44\ub111.23 ng/Kg/min of All). After ASA administration there was a significant increase in EPD in AST+ patients (15.00\ub19.54 ng/Kg/min, p<0.001). In AST- patients the mean EPD was significantly but non-homogeneously changed (18.33\ub18.11 ng/Kg/min). Nineteen pregnant high risk patients also underwent AST between weeks 24 and 39 of gestation. Then systolic, diastolic and mean arterial blood pressure were recorded using a portable device for indirect noninvasive automatic arterial pressure measure before and after seven days of low-dose aspirin therapy. In AST- patients no significant difference was observed before and after ASA regimen, whereas in AST+ patients post ASA mean blood pressure values were lower than pre ASA values, and during nighttime this difference became significant