The vegetation of Cholistan and Thai deserts, Pakistan

Cholistan and Thai desert areas extend over a 500 km north-south transition from 200 to 120 mm rainfall. They were sampled by repeated 100-m long transects at 55 sites. Ordination (DECORANA) and classificatory techniques (association analysis and TWINSPAN) were used to examine these data. No clearly disjunct vegetation patterns emerged from these analyses. The major axes brought out by the ordination were related to disturbance and seasonality, although it is possible to relate the units of classification to broad soil types. The application of the classifications to the ordination allowed an interpretation of the vegetation variation in terms of topography, disturbance and utilization by the human population. The vegetation patterns revealed are discussed in relation to the general problem of plant community definition in vegetation of widely scattered plants, and the specific history of the deserts of the Indian sub-continent.