Abstract:
Kandyan home gardens are well-established land use systems found in the mid
country wet zone especially in and around the Kandy District. Due to their unique
vegetation characteristics, these ecosystems play an important role in enhancing food
security and biodiversity. Among the cultivated species, nutmeg (Myristica fragrans)
has become a popular crop due to its high economic value. This study aims to
investigate the dominance of nutmeg in Kandyan home gardens and its impact on
plant diversity by comparing the species diversity of home gardens with and without
nutmeg trees. Vegetation data were collected using the Point-Centered Quarter
Method (PCQM) at 10 sampling points along a 50 m transect, recording 40 trees
in total. Light intensity at each point was measured and for each plant, the distance
from the central point, diameter at breast height (DBH), and tree height were
recorded. Species dominance, diversity, and structure were assessed using standard
ecological indices. A species abundance matrix within study sites was analyzed using
PCORD software. Cluster analysis and Detrended Correspondence Analysis (DCA)
were used to determine species composition patterns across Kandyan home gardens.
Biodiversity indices were computed using Biodiversity Pro software for comparative
analysis between sampling sites. Nutmeg was found in 78% of the sites surveyed,
contributing an average of 17% to total tree density and 19.75% to overall basal area,
indicating its strong ecological presence. Home gardens with higher nutmeg density
showed lower absolute tree density, reduced light intensity, and a strong negative
correlation between nutmeg abundance and understory light levels. Species diversity
was notably lower in nutmeg-dominated sites. Cluster and DCA analyses grouped
home gardens into distinct clusters based on species assemblages, with nutmeg
dominated sites forming separate ecological outliers. DCA ordination confirmed that
Myristica fragrans strongly influenced site distribution, highlighting its role as a key
driver of species composition. These findings suggest that nutmeg dominance can
substantially alter species diversity and ecosystem structure in Kandyan home
gardens. Adaptive management strategies are recommended to maintain productivity,
ecological resilience, and biodiversity conservation in these systems.
