Floristic Zones Research Articles

Floristic Relationships Along the Cascade-Sierran Axis

Seventeen areas along the Cascade-Sierran mountain axis are compared on the basis of plant species in common. The floras for each area, separated into montane and alpine components based on ecological criteria, are compared using a simple dissimilarity function (Sorenson's Index) and a cluster analysis technique. Floristic zones, related to geographical position along the mountain chain, are identified. Eighty-five percent of the variation of floristic dissimilarity between the areas studied is accounted for by the geograph- ical distance between areas; topographic and climatic variables explain less of the total observed variation. Families which are more similar between areas than would normally be expected are reported, based on chi-square comparisons. Latitudinal gradients of decrease or increase in the importance of certain families in the flora of the Cascade-Sierran axis are given. Brief mention is made of the possible geographical, historical and ecological factors which control the observed relationships.

Stratigraphical notes on the standard sequence of the Upper Gondwanas of India

Recent additions to the knowledge of the geological history and the floral characters of the various Gondwana members in India necessitate to revise the so far accepted standard sequence of the Upper Gondwana formations. A new scheme based on the geological history and the palaeobotanical characters of the beds is here proposed. The sequence is represented by Mahadeva and Jabalpur series (in the revised sense). The former consists of two stages - Pachmarhi and Denwa, while the latter consists of four floristic zones corresponding to: Parsora, Rajmahal, Nipania and Bhuj.