Species Composition and Plant Diversity as Influenced by Altitude and Size of Homegardens in Mizoram, North-East India

摘要

Floristic assemblage, crop diversity, occurrence, vertical stratification of species and use aspects of 92 homegardens in twenty two villages in Mizoram, northeast India was studied. An attempt was made to assess the influence of altitude and size of homegardens on different attributes of vegetation. A total of 351 plants belonging to 101 families were recorded from the survey which included 170 trees, 42 shrubs, 94 herbs, 5 epiphytes, 34 climbers and 6 bamboo species. An average of 34 plant species (sd, ±14) per garden were recorded; more than fifty percent of the gardens contain 21 -40 plant species while very few gardens have less than 10 species or more than 60 species per garden. Density of trees per unit area was significantly (p＜0.01) more in low altitudes and least in the high altitude gardens and it ranged from 15 trees in a garden in mid altitude to 720 trees in low altitude. Shannon Weiner diversity index of trees and shrubs varied significantly (p＜0.01) across the altitudes and was higher (H'=3.89) in the mid altitudes and minimum (H' =2.73) in the low altitudes. The importance value index (IVI) of plants showed that Parkia timoriana was more ecologically important in the high altitude (19.76) and mid altitude gardens (5.61) while it was Areca cachecu (16.61) in the low altitude. The former showed a decreasing stem density per garden with decreasing altitude. The relationship between garden size and the number of species encountered at different altitudes showed an weak increasing trend but was significant at the high altitude gardens (p＜0.01).