Assessment and impact of alien species - Mimosa invisa L. on the biodiversity and pattern of vegetation at Dhoni hills, Western Ghats of Palakkad, Kerala-A case study

Abstract

Mimosa invisa is a widely adapted weed from tropical America that has invaded the Dhoni hills of Palakkad District, Kerala. They were established as monocultures in grasslands, agricultural fields, plantations and forest areas of Palakkad, causing threats to other species. In this juncture, the present study was conducted to evaluate the impact of Mimosa invisa on the natural biodiversity and floristic compositions of native species of Dhoni hills, Palakkad. Vegetation analysis was carried out using random-systematic design and gradient methods, including the importance value index, species richness, dominance index, diversity, similarity and dissimilarity index, using standard protocols, followed by soil parameters such as pH and nutrient content and phenols in the invaded and uninvaded areas. It was noticed that in the Mimosa invaded area, the mean species number and the α diversity declined by 32.10% and 41.21%, respectively. Similarly, fresh and dry plant weight displayed remarkable variation (decreased by 35.9 and 49.9%, respectively) in the intruded zones. Out of 135 species recorded, 63 species were common in the control and intruded zones. Eleven species were growing exclusively in the invaded areas. The total phenolic content was 45%, the ion conductivity was 32%, the % of organic carbon and organic matter was 51%, the nitrogen content was 55.7%, and the phosphorus, potassium and sodium contents were 48, 38.5 and 24.4%, respectively, in the invaded soil compared to the control. Similarly, the calcium, magnesium and chloride contents were increased by 38.4, 30.6 and 33.5% respectively. Hence, it could be concluded that the invasion of M. invisa drastically affected the productivity and diversity of the invaded areas in the Dhoni hills of Palakkad.