Commonness and rarity pattern of plant species within <i>Terai</i> grassland of northeastern Uttar Pradesh, India

Abstract

We investigated the frequency of occurrence of plant species in grassy landscapes in northeastern Uttar Pradesh, India. Using random quadrats, field assessment was undertaken at 11 sites to sample an area of 333.75 ha, at an overall sampling density of 0.01%. A total of 287 plant species belonging to 183 genera and 53 families was recorded. Of these, 254 species were commonly distributed and 33 species exhibited localized occurrences; according to the rarity classes of Rabinowitz, the latter were classified as rare. One hundred and sixty-five species had large population sizes and 122 species exhibited small population sizes. The most common species, which exhibited high frequency and abundance, were predominantly from Poaceae, Cyperaceae, Papilionaceae, Asteraceae, Scrophulariaceae and Euphorbiaceae. Some species, which are known to have narrow geographical distributions, were locally abundant. Rare species showed restricted as well as localized distributions and were typically sampled at low population densities. The rare occurrences of once frequent and widespread species probably reflect acute fragmentation and shrinkage of specialized habitats as a result of intense cultural activities. Several species are to be considered as threatened. Studies on the status of rare plant species and the processes threatening their survival are urgently required.

Keywords: Community structure, frequency of occurrence, habit groups, habitat fragmentation, native grassland.