Plant Diversity of North-Eastern Uttar Pradesh, India: Species Distribution and Depletion Pattern During the Last Five Decades

Abstract

The landscape of north-eastern Uttar Pradesh is a mosaic of several land uses and vegetation types. A detailed survey of the area reported 1057 plant species belonging to 563 genera and 119 families during 1960s. The gradual rarefaction and eventual local extinction of plant species of different habits have been viewed in the light of perceived changes in the local climatic conditions during the last few decades.  The estimate showed consistent decrease in the occurrence of species during the last 5 decades which together amount to about 15.70% of the total species content. Amongst the four vegetation types, the highest depletion occurred in grassland followed by forest, wasteland and old-fields in that order. As regards the generic depletion, about 62 monotypic and 4 polytypic genera out of the total 563 genera, recorded around 1960, were lost during the past five decades.  A number of species which showed rare occurrences in 1960s, gradually became very rare and most of these species locally disappeared by 2014. During the past five decades, the region of north-eastern Uttar Pradesh experienced intense land-use and associated disturbances such as deforestation, intense grazing, trampling etc. that appear to have severely affected the existence of several plant species. The species richness of a disturbed site depends on the differential responses of its species to such disturbances.  The ongoing loss and fragmentation of habitats of natural forests and grasslands, therefore, pushed a number of monotypic genera towards rarity during the last five decades. These taxa are:  Abrus, Asparagus, Calamus, Clitoria, Gloriosa, Narvelia and Oxystelma. A major share of herbaceous as well as woody plant species depleted during 1980s -1990s. This period coincided with the major changes in the pattern of temperature and rainfall. Severe changes in habitat conditions resulted into the loss of specialist species and rise of a number of opportunist species.  Several shrubby species such as Helicteres jamaicensis, Mahonia nepalensis, Nitraria schoberi, Opuntia dillenii, Phlogacanthus curviflorus, Psoralea drupacea, Securinega virosa, Thyrsostachys  oliveri and Toddalia  aculeata also got severely depleted  and became locally extinct by 2000s. During recent years, much of these communities or habitats shrank fast due to expansion of agricultural fields. The number of lianas and vines, however, did not dwindle as fast. Several exotics recently took over the indigenous species and showed natural aggregation at places.  Sincere efforts are required for conservation of habitat of herbaceous and woody plants in order to ensure the perpetuity of regional bio-resource and their sustained utilization for food, fodder, fuel, medicine etc.