Environmental Factors Affecting Growth of Agarwood (Aquilaria malaccensis Lamarck, 1783) Forests of Bhutan

Abstract

Aquilaria malaccensis Lam., commonly referred by its trade name Agarwood, is an endangered species. Its natural distribution and ecology in Bhutan are poorly known. So, this study aimed to understand the ecological requirements and model suitable habitats for the growth of A. malaccensis in the country. Using purposive-non-probability sampling, vegetation data were collected from plot sizes of
20 x 20 m for trees, 5 x 5 m for understory and 2 x 2 m for groundcover. A total of 168 plant species under 67 families were recorded. Lauraceae and Euphorbiaceae were found to be the most dominant and co-dominant families in the natural Agarwood stand. A cluster analysis using PC-ORD revealed that Agarwood prefers habitat with warm-moist evergreen broadleaved forest. The Pearson and Kendall correlation in NMS ordination showed the strongest correlation between Agarwood growth and mean annual rainfall (r = 0.90) followed by average soil pH of 6.15 (r = 0.82). However, the slope and aspect of the area exhibited a negative correlation with the growth and distribution of Agarwood (r = -0.46). An area of 6,490.8 km², which accounts to 16.9% of Bhutan, was found to be suitable for cultivating Agarwood. This could support Agarwood regeneration and plantation to conserve and protect the species from extinction in the wild.