The self-thinning exponent in overcrowded stands of the mangrove, Kandelia obovata, on Okinawa Island, Japan

• Published in: Journal of oceanography Vol. 68; no. 6; pp. 851 - 856
• Main Authors: Kamara, Mouctar, Deshar, Rashila, Sharma, Sahadev, Kamruzzaman, Md, Hagihara, Akio
• Format: Journal Article
• Language: English
• Published: Japan Springer Japan 01.12.2012; Springer Nature B.V
• Subjects: Biomass; Earth and Environmental Science; Earth Sciences; Freshwater & Marine Ecology; Kandelia; Marine; Oceanography; Population density; Special Section: Original Article; Terrestrial ecosystems; Thinning; Trees; Wetlands; Japan; Okinawa; ISEW, Japan, Nansei-shoto, Okinawa; ISEW, Japan, Nansei-Shoto, Okinawa Prefect., Okinawa I; Weller’s allometric model; Self-thinning exponent; Self-thinning line; Biomass density; 3/2 power law of self-thinning; Metabolic model; Simple geometric model
• ISSN: 0916-8370; 1573-868X
• DOI: 10.1007/s10872-012-0135-7

Weller’s allometric model assumes that the allometric relationships of mean area occupied by a tree , i.e., the reciprocal of population density , , mean tree height , and mean aboveground mass density to mean aboveground mass hold. Using the model, the self-thinning line of overcrowded Kandelia obovata stands in Okinawa, Japan, was studied over 8 years. Mean tree height increased with increasing . The values of the allometric constant and the multiplying factor are 0.3857 and 2.157 m kg −θ , respectively. The allometric constant and the multiplying factor are −0.01673 and 2.685 m −3  kg 1−δ , respectively. The value was not significantly different from zero, showing that remains constant regardless of any increase in . The average of , i.e., biomass density , was 2.641 ± 0.022 kg m −3 , which was considerably higher than 1.3–1.5 kg m −3 of most terrestrial forests. The self-thinning exponent and the multiplying factor were estimated to be 1.585 and 16.18 kg m −2α , respectively. The estimators and are dependent on each other. Therefore, the observed value of cannot be used for the test of the hypothesis that the expectation of the estimator equals 1/3, i.e., , or 1/4, i.e., . The value was 0.6310, which is the same as the reciprocal of the self-thinning exponent of 1.585, and was not significantly different from 2/3 ( t  = 1.860, df  = 191, p  = 0.06429), i.e., . Thus the self-thinning exponent is not significantly different from 3/2 based on the simple geometric model. On the other hand, the self-thinning exponent was significantly different from 3/4 ( t  = 6.213, df  = 191, p  = 3.182 × 10 −9 ), i.e., . Therefore, the self-thinning exponent is significantly different from 4/3 based on the metabolic model.