The present flora and vegetation of the moraines of the Klutlan Glacier,Yukon Territory,Canada: A study in plant succession

The flora and vegetation of six ice-cored moraines of the Klutlan Glacier were analyzed in 65 plots by European plant-sociological techniques. The age of each plot was estimated from annual growth rings of shrubs or trees in the plots. Nine major vegetation types are distinguished: Crepis nana, Dryas drummondii, Hedysarum mackenzii, Hedysarum-Salix, Salix-Shepherdia canadensis, Picea-Salix, Picea-Arctostaphylos, Picea-Ledum, and Picea-Rhytidium. These contain plants aged 2–6, 9–23, 10–20, 24–30, 32–58, 58–80, 96–178, 177–240, and >163- >339 yr, respectively. Six other vegetation types are described from windthrow areas, drainage channels, volcanic tephra slopes, lake margins, fens, and drained lakes. The major vegetation types reflect a vegetational succession related to moraine age and stability, with the Crepis nana type as the pioneer vegetation developing through the other vegetation types to the Picea-Rhytidium type on the oldest moraines. Changes in species diversity and soil development, particularly humus accumulation, parallel the vegetational succession. This succession differs from patterns of revegetation of deglaciated landscapes in Alaska and British Columbia today and in Minnesota in late-Wisconsin times because of differences in climate, plant migration, and local ecology.     

Predictive elements of large-body impacts in geologic history

Large-body impacts cannot be predicted, although the probability (size-frequency) of large impacts on the Earth has been worked out, yielding frequencies of the order of one impact of a 1-km body every 500?000 years. Another type of prediction, however, is that forthcoming from the consequences of a large-body impact. Prediction as validation of theory. What can be predicted are the consequences of a large impact, ranging from local and regional ejecta blankets to global climate changes leading to mass extinctions. It is the fulfillment of such predictions that has rendered strength to the impact-extinction theory for the Cretaceous-Tertiary (K/T) boundary, in contrast to predictions attached to widespread volcanism, such as at the Deccan traps in India, or sea-level changes.     

Beobachtungen an der Küste von Suriname

Ohne Zusammenfassung