Soil carbon and nitrogen in a Great Basin pinyon–juniper woodland: Influence of vegetation,burning, and time

Much of the Great Basin, U.S. is currently dominated by sagebrush (Artemisia tridentate ssp. (Rydb.) Boivin) ecosystems. At intermediate elevations, sagebrush ecosystems are increasingly influenced by pinyon (Pinus monophylla Torr. & Frém.) and juniper (Juniperus osteosperma Torr.) expansion. Some scientists and policy makers believe that increasing woodland cover in the intermountain western US will create new carbon storage on the landscape; however, little is currently known about the distribution of carbon on these landscapes. This is especially true of below ground pools. Our objectives were to quantify the spatial distribution of soil carbon in expansion woodlands, and to determine prescribed fire's effect on soil C and N. We looked at two treatments (control and burn), three microsites (undertree, undershrub, and interspace), and four soil depths (0–8, 8–23, 23–38, and 38–52 cm). The study was conducted over a six year period with one year pre-fire and five years post-fire data. Results for both carbon and nitrogen were similar, indicating the close relationship between the two elements in this ecosystem. Undershrub microsites had higher soil C and N concentrations than interspace and undertree microsites; however, under tree microsites had higher C:N ratio than interspace and undershrub microsites. Carbon and nitrogen concentration tended to decrease with increasing depth at both control and burn sites. Prescribed burning caused immediate increases in surface soil C and N concentration, but over intermediate to longer periods of time no statistically detectable change in soil C or N content occurred from burning.     

Experimentelle Untersuchungen über die Erzeugung von Salzteilchen aus den Meeren

Zusammenfassung Die für die Erzeugung von Salzteilchen aus dem Meer wesentlichen Vorg?nge werden untersucht, wobei die Teilchen nachVittori nachgewiesen und vermessen werden. Es zeigt sich, dass Zerplatzen von aufsteigenden Luftblasen allein wenig wirksam ist. Dagegen nimmt die erzeugte Teilchenzahl mit wachsender Zersprühgeschwindigkeit rasch zu. Dichten von 10⁶ pro cm³ durchgeblasener Luft sind leicht realisierbar. Die Ergebnisse werden im Hinblick auf die für und wider dieK?hler’sche Hypothese vorgebrachten Argumente und auf die tats?chlichen Chloridgehalte der Atmosph?re diskutiert.

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Summary The processes essential for the production of salt-particles from the sea are investigated, the particles being identified and measured according toVittori. Bursting air bubbles are shown to be mostly ineffective. The number of produced particles increases rapidly with accelerating velocity of spraying. Populations of 10⁶ per cm³ of air blown through the water are possible. The results are discussed with regard to the arguments stated pro and contra the hypothesis ofK?hler and to the chlorid contents of the atmosphere.

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Résumé Les facteurs essentiels pour la production de particules de chlorure de sodium hors de la mer sont examinés en indiquant et mesurant les particules selon la méthode deVittori. L’éclatement des bulles d’air ascendant dans l’eau est démontré être peu efficace. Le nombre de particules produits s’augmente très vite, si la vélocité de jaillissement s’accro?t. On peut aisément réaliser des densités de 10⁶ par cm³ d’air soufflé. Les résultats sont discutés en vue des arguments constatés pro et contre l’hypothèse deK?hler et de la quantité de chlorure, contenue effectivement dans l’atmosphère.

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Dr.W. Rau, Max-Planck-Institut für Physik der Stratosph?re,Weissenau (Würtibg.).     

Some examples of the Middle-Triassic Marine transgression in South-Western Mediterranean Europe

In Southwestern Mediterranean Europe (NE Spain, Sardinia and NW Apennines e. g. Monti Pisani and Punta Bianca) the Middle-Triassic transgression on a margin of an intracratonic basin appears to be controlled by the different morphology and tectonic activity of the margin itself. The analysis of some sequences leads to recognize three different kinds of margins:

1. margin with a narrow shelf sloping toward a very shallow restricted basin (Central and Southwestern Sardinia);
2. margin with a broad shelf gently sloping toward a shallow basin (NE Spain, Monti Pisani, NW Sardinia);
3. margin with a narrow shelf and steep slope marked by tectonic and volcanic activity (Punta Bianca).