TITLE:
Assessment of Performance of Sandalwood Grown under Different Agro-Climatic Zones of Karnataka Based on Relationship and Principal Component Analysis
AUTHORS:
Baragur Neelappa Divakara, Ghattamaraju Maruthi Sankar
KEYWORDS:
Sandalwood, Tree Growth Parameters, Soil Nutrients, Coefficient of Variation, Correlation, Principal Components
JOURNAL NAME:
Open Journal of Forestry,
Vol.16 No.3,
July
21,
2026
ABSTRACT: Santalum album L. (sandalwood) is a highly valued tree species cultivated for its heartwood and essential oil. The present study assessed the growth performance and adaptability of sandalwood across different agro-climatic zones (ACZs) of Karnataka, India, by examining relationships among growth, yield, soil, and weather parameters using correlation analysis and Principal Component Analysis (PCA). A total of 73 field plots were established on farmers’ lands, with plot sizes ranging from 110 m2 to 533 m2, ensuring the inclusion of at least 25 - 30 sandalwood trees per plot. Growth attributes (tree height, diameter at breast height, and heartwood diameter), heartwood yield, soil fertility characteristics, and weather variables were recorded and analyzed. Annual rainfall varied from 266.5 mm to 1376.4 mm (mean: 471 mm; CV: 56.9%), while mean temperature ranged from 23.7˚C to 28.0˚C (mean: 25.2˚C; CV: 4.4%). Rainfall exhibited a positive correlation with heartwood percentage in ACZ-5 (r = 0.396) and pooled ACZs (2, 7, 8, 9, and 10) (r = 0.667). In contrast, temperature showed negative associations with heartwood percentage in ACZ-5 (r = −0.483) and heartwood diameter in ACZ-6 (r = −0.730). Organic carbon was positively correlated with soil nitrogen across ACZ-3 to ACZ-6 and pooled zones, while tree diameter demonstrated a strong positive relationship with heartwood content in these regions. Significant associations among calcium, magnesium, and sulphur were observed in ACZ-3, ACZ-4, and ACZ-5. Heartwood content was influenced by tree age in ACZ-3, ACZ-5, and pooled zones, whereas tree height and heartwood diameter were important determinants in ACZ-4. PCA identified major soil fertility parameters driving growth variability, with strong loadings for pH, electrical conductivity (EC), organic carbon, nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, iron, copper, and zinc. Five principal components explained 77.07% of the total variance in ACZ-5, four components explained 79.09% - 85.87% in ACZ-4, ACZ-6, and pooled ACZs, and three components accounted for 74.01% in ACZ-3. Soil properties, particularly pH, EC, calcium, magnesium, and sulphur, exhibited relatively low variability and were consistently associated with improved growth and heartwood yield. The study demonstrates that sandalwood productivity is strongly influenced by the interaction of climatic conditions, soil fertility, and tree growth characteristics. The integration of environmental, edaphic, and growth variables through multivariate analyses provides a robust framework for identifying key drivers of sandalwood performance and offers valuable insights for zonal agroforestry planning, resource allocation, and site-specific management strategies aimed at maximizing heartwood production across Karnataka.