Exotic and Invasive Plants (Aquatic and Ecotone) of Nalbari District of Assam

Author(s): Gunajit Kalita*, Durlav Nr Singha and Sarada Kanta Sarma

Abstract: The exotic aquatic invasive plant species degrades wetlands and initiates succession that causes slow death and gradual loss of productive life of the wetlands. The gregarious growth of aquatic macrophytes during rainy season and subsequent accumulation of organic debris during winter season in wetlands significantly changes the characteristics of the water bodies and reduces the water spread area of the wetlands. Their luxuriant growth and subsequent death and decay, and deposition make the wetland shallow which consequently promotes succession by terrestrial species. The management of aquatic invasive weeds is very important in the wetland conservation strategy. The invasion by aquatic weeds of feeder channels of the wetlands not only clogs the drainage systems but also alters the hydrology of the wetlands. The alteration in the hydrological regime makes the water body shallower in due course of time and this in turn invites more invasions by aquatic as well as terrestrial plant species. Thus once resourceful wetland becomes hydrocere in due course of time due to invasion and subsequent succession. In this context, ecological investigations have been carried out in some of the wetlands, low-lying water logged areas, rice fields etc of Nalbari district of Assam to document the aquatic and ecotone invasive plant species. The menace of invasion by aquatic macrophytes was observed in the above mentioned places. In a typical scenario during investigation it was observed that a floodplain wetland of Pagladia river is completely invaded by aquatic weeds and practically changed its wetland characteristics into that of a marshy land. A large number of aquatic macrophytes were recorded from those wetlands, of which some of the invasive species that grows gregariously are Eichhornia crassipes, Hygroryza aristata, Cyclosorus gongyloides, Alpinia galanga, Echinochloa colonum, Ipomoea fistulosa, Ipomoea aquatica etc. Most of these aquatic weeds were present throughout the year in the wetlands of Nalbari district of Assam. Their phenological characters shows interesting features like flowering stages of some species can be observed two to three times in a year. This indicates their resilience and potential to invade and destroy the water bodies in a very short span of time.

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