Environment factors influencing abundance and growth of wild yam in broadleaved forest, Tsirang District, Bhutan

Yams (Dioscorea) consist of approximately 600 species in the world. Yams are considered a staple food in Asia, tropical and subtropical regions. Genetic erosion and unsustainable harvesting practices are among the main problems associated with wild yam plants. This study was conducted with the objectives to enumerate wild yam species composition and environmental parameters affecting its growth and abundance. Systematic sampling of the study site was carried out based on different land aspects. Line transects were laid out in selected land aspects within the elevation range of 825 – 1935 m. Five plots in each transect with a 100 m plot interval comprising seven transects were laid out in the study area. Each plot was divided into sub-plot of 20 x 20 m, 5 x 5 m, and 1 x 1 m to enumerate trees, shrubs, and herbs respectively. Seven species of yams were found from the broadleaved forest and spearman correlation showed negative association of yam abundance with tree counts and canopy closure. The areas with higher density of trees had low count of yam abundance. Yam grows well in open canopy in lower altitudes comparing to high altitudes. Yam abundance was positively related with shrubs, herbs, soil moisture, soil organic matter, soil organic carbon, and nitrogen content. Analysis of Variance (ANOVA) showed significant difference of yam abundance in 7 different transects due to different ecological parameters influencing the abundance in different transects though transect being in a broadleaved forest.