IMPACT OF AGERATUM HOUSTONIANUM MILL. INVASION ON PLANT DIVERSITY AND CROPS IN DIFFERENT LAND USE TYPES OF KANCHANPUR, NEPAL

Abstract

Invasive plant species means an alien species which become established in natural or semi-natural ecosystems and threatens native biological diversity. It has high resistant capacity, produce large number of seeds and can grow easily in different types of habitat. It can out-compete native species, reduces wildlife habitat potential, alter ecosystem processes and change soil properties and have great role in land cover change. Ageratum houstonianum is a native species of America that enters to Nepal. It has grown in different land use (agriculture, forest, grassland). Laljhadhi-Mohana Biological corridor (LMBC) is corridor between Suklaphanta national park and Dudhwa national park largest national park of India. Corridor is a pathway of plants and animals so invasive plants species can easily enters. From India to Nepal invasive species can easily enters through corridors and may impact native species diversity. To understand the impact of A. houstoniunum on species diversity, vegetation sampling was done. Altogether 120 plots of size 2m×2m were laid in each sampling site (invaded and non-invaded sites).Different quantitative parameters for vegetation analysis like frequency, density, coverage, IVI, Simpson Index, Shannon Wiener Index were calculated. Results showed that the diversity of non-invaded area was greater than the invaded area. To understand the impact of allelochemical effect of leaf to the crop plant, different concentrations (2, 10, 20, 30, 50%) were prepared. Seed germination of winter and summer crop plant was done in different concentrations of leaf extract and also in control to compare the impact. Germination was significantly inhibited (p=0.05) in higher concentrations (20, 20, 50%) than lower concentrations (2, 10%) of mustard crop. Measurement of radicle and plumule was taken. Growth rate was lower in high concentrations (20, 30, 50%) than low concentrations (2, 10%). Summer crop (maize and paddy) was not affected by allelochemical effect of leaf extract but winter crop (mustard and wheat) was highly affected by allelochemical effect of A. houstonianum.