News Excerpt:

Assam is grappling with a growing threat from invasive plants that are rapidly taking over its forests, wreaking havoc on the region's biodiversity and impacting the diet of wild and domestic animals.

About Mimosa species:

• It is known as Touch-Me-Not, Shameplant, or giant sensitive plant, and is highly invasive. It has been identified by researchers as a climbing plant originating from America.
• Its characteristics include -
• rapid growth rate (10 mm per day),
• rapid maturation (germination to first flowering within 6 months),
• potentially autogamous,
• abundant seed production (9000 seeds per m2 annually),
• a large, long-lived (>10 years) seed bank in soil, and
• an effective dispersal system (flotation of clusters of capsules and via attachment to animals).
• Researchers attribute the spread of Mimosa to the tea industry, which was good for nitrogen fixation to enrich soils.
• However, climatic and geographical factors contributed to its spread, which choked the grasslands of Kaziranga within a few decades.
• Wildlife Trust of India (WTI) suggested that only manual removal of the roots of Mimosa varieties could stop its spread.

Siam species:

• It is also known as Chromolaena odorata, is a fast-growing perennial shrub, native to South America and Central America.
• It has been introduced into the tropical regions of Asia, Africa and the Pacific, where it is an invasive weed.
• It forms dense stands that prevent the establishment of other plant species. It is an aggressive competitor and may have allelopathic effects.
• Allelopathy is defined as a direct or indirect interaction, whereby allelochemicals released by one organism influence the physiological processes of other neighboring organisms.
• It is also a nuisance weed in agricultural land and commercial plantations.
• A study by Assam-based non-profit working on conservation, Aranyak, found that in 2004, the density of Siam weed was found to be highest among invasive species in Manas National Park’s grasslands.

Ludwigia peruviana:

• Family: Onagraceae
• Habit: shrubby perennial forb; semi-aquatic, reaching up to 15 feet in height.
• Seeds: The seeds are hydrophobic and will germinate while afloat in some cases allowing the formation of floating islands.
• It is also known as Peruvian water primrose.
• A rapid colonizer, it can quickly establish dense infestations, crowding out native vegetation and reducing wildlife diversity.
• Floating plant islands reduce water flow and navigability.

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