Agroforestry species composition and growth of Black Cardamom in different habitats along altitudinal gradient, Bhutan

Abstract

Abstract The composition and arrangement of agroforestry species at different altitudes play a vital environmental role in the growth of Black Cardamom crop. The present study assesses agroforestry tree species composition and the relationship between the growth of Black Cardamom and associated tree species. For this, the altitudes were sorted into three altitudinal ranges; low (850-1150 m), mid (1250-1550 m), and high (1650-1950 m) and in each altitudinal range three different habitats were assessed (Timber Tree (TT), Fodder tree (FT) and Mix tree (MT) habitats). In each altitudinal band, 16 plots were made for each habitat (TT, MT, FT) with a total of 144 plots sampled systematically with 20×20 m plot size within the selected altitudinal range (850 to 1950 m). The result of the study found 56 ecologically important agroforestry tree species under 32 families that are used as shade trees for Black Cardamom. The tree species preference of Black Cardamom changes based on the basal area of trees, altitudes, and habitat types (F(2, 33)=45.672, P=.000). The overall growth (R2=.95) was better in timber tree habitat at mid altitudes, where Alnus nepalensis was the dominating species having 41.40% canopy cover with low pest and disease-infested Black Cardamom stems, making it a suitable habitat for growth. The lower altitudinal band and all the mixed tree habitats were found to be unsuitable for Black Cardamom growth (p<0.05). Thus, while cultivating Black Cardamom it is important to select appropriate tree species, canopy cover, altitude, and habitat for optimum growth.