Present study was carried out to understand the proliferation status of invasive alien species (IAS) along altitudinal gradient (650-2150 m) in different forest types (Sal, Pine, Oak and Deodar) of western Himalaya. To understand the trend of proliferation of invasive species repeat vegetation survey and quantitative analysis method used in same plots after two years. Major invasive species in the region were Lantana camara, Ageratina adenophora, Ageratum conyzoides and Parthenium hysterophorus. Ageratina adenophora was highly spreading invasive species present in all forest type of the study area. Maximum density (8394 ind/ha.) and frequency (64.15%) was recorded in Pine forest. Important value index (IVI) of Ageratina adenophora increase from 23.4 to 25.71 in Pine forest followed by in Sal forest (6.32 to 8.21) and Deodar forest (11 to 12.53). Maximum density (246 ind/ha.) and frequency (41%) of Lantana camara recorded in Sal forest and IVI increase from 29.9 to 30.78. Oak forest allowed less rate of invasion of alien species. In study area with increase elevation number of invasive species decrease. However, high proliferation rate of Ageratina adenophora recorded at an elevation 2150 m asl in moist Deodar forest.

Keywords: Invasive Alien Species; Proliferation; Forest Types;