Interactive Effects of Soil Moisture and pH on Early Growth of Bush Candle Tree (Canarium schweinfurthii)

An overexploitation of Canarium schweinfurthii (commonly known as the bush candle tree; family: 
Burseraceae) for fuel, medicine, food, and construction has resulted in a tremendous decline in its 
population in the Western Highlands Forest of Cameroon. The situation is exacerbated by a long 
latent period, which lowers the competitive ability of seedlings compared to rapidly germinating 
and fast-growing species. Investigating the responses of seedlings to environmental conditions in 
the ecosystem is crucial for developing strategies to enhance their growth. The aim of this study 
was to test the effect of moisture and pH on the early growth of C. schweinfurthii. Three-week-old 
plants were grown under three soil moisture regimes (low: 20 – 30 %; medium: 40 – 50 %; high: 60 
– 70 % Field Water Capacity) and two soil pH levels (pH 7.0; pH 4.5 - 5.5). The treatments were 
laid out in a split plot design, with moisture as the whole plot and pH as the subplot. Measurements 
of growth were taken three months after the initiation of treatments. The data were subjected to 
split plot ANOVA and then Scheffe's test for mean separation. The high soil moisture regime 
significantly increased plant height, stem volume, number of leaves, and leaf area. The lower soil 
pH level suppressed height, stem volume, height-to-diameter ratio, number of leaves, and leaf area. 
There were significant effects of moisture × pH on height, stem volume, number of leaves, and leaf 
area, indicating that the effect of moisture depended on the pH treatment level. For instance, the 
increase in the number of leaves and leaf area due to the high soil moisture regime was limited only 
to seedlings in the higher pH treatment level. The findings of this study highlight the need to 
improve soil moisture and pH conditions in drier and acidic areas of the species' range in order to 
increase the growth potential of seedlings.