Abstract. Depletion of Ca in forests and its effects on forest health are poorly quantified. Depletion has been difficult to document due to limitations in determining rates at which Ca becomes available for ecosystem processes through weathering, and difficulty in determining changes in ecosystem storage. We coupled a detailed analysis of Sr isotopic composition with a mass balance at Cone Pond Watershed, New Hampshire, in order to further constrain estimates of these processes. Strontium acted as an analog for Ca in most processes except translocation of nutrients within forest vegetation. Variability in mineralogic and Sr isotopic composition of bedrock and soils complicated assessment of 87 8-6the Sr/ Sr ratio released to solution by weathering reactions. By conducting a mass balance on atmospherically derived Ca, it is possible to distinguish Ca weathering losses from Ca leached from ecosystem pools. The calcium weathering rate estimated by this method was less than half of that determined by mass balance assuming steady state conditions.
CHEMICAL composition. X-ray diffraction and other analytical data of a series of samples of clays that are composed essentially of illite are presented. The physical properties of these samples are given and related to variations in the composition and character of the illites. Data indicate that these ilUtes have less potassium than well-crystalUzed micas and some of them are not essentially mixed-layer structures. It is concluded, therefore, that illite is not necessarily a mixed-layer material.
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