role of wood density and stem support costs in the growth and mortality of tropical trees

• Published in: The Journal of ecology Vol. 94; no. 3; pp. 670 - 680
• Main Authors: King, David A, Davies, Stuart J, Tan, Sylvester, Noor, Nur Supardi Md
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-05-2006; British Ecological Society; Blackwell Publishing Ltd; Blackwell Science
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Demecology; demography; diameter; Dipterocarpaceae; dry matter accumulation; Forest ecology; Forest growth; Forest trees; Functional Relationships; Fundamental and applied biological sciences. Psychology; General aspects; height; Human ecology; life‐history strategies; mechanical support costs; Plant ecology; Plant growth; Rainforests; rapid growth; Risk factors; tree architecture; tree crown; Tree crowns; tree growth; tree trunk; Trees; Tropical forests; tropical rain forest; Tropical rain forests; Wood density; Borneo; Malaysia; Costs; Life history; life-history strategies; Demography; Wood; Growth; Mortality; Tropical rain forest; Stem; mechanical support costs; wood density; Tree; Strategy; tree architecture; Population dynamics
• ISSN: 0022-0477; 1365-2745
• DOI: 10.1111/j.1365-2745.2006.01112.x

1 The rapid growth rates of light-demanding tree species have been attributed in part to their low-density, low-cost stems. We evaluated the influence of light and biomass support costs on growth rates of trees 8-25 cm in diameter at breast height (d.b.h.) among 21 species differing in wood density in two aseasonal rain forests. 2 Measurements of crown width, tree height, d.b.h. and wood density (p) were used to estimate the stem biomass (Ms) of a standard-sized tree (17 m tall and$16 m^2$in crown area), i.e. the cost in stem biomass of supporting a given sized crown at a given height. 3 The species showed a three-fold range in support cost, which was highly correlated with wood density ($M_s \propto p^{0.77}$, r2= 0.72 for the log-transformed relationship). This relationship is due to the high interspecific variation in wood density and the fact that the stem diameter of the standard-sized tree increased only slightly with decreasing wood density, i.e. light-wooded species did not compensate for their lighter, weaker wood by substantially increasing stem thickness. 4 Mean growth rate per species showed a 10-fold range and increased with the fraction of trees at least partly in gaps (gap fraction), the reciprocal of support cost$(1/M_s)$, and the reciprocal of wood density$(1/\rho)$. The relationship between mean growth rate and$1/M_s$was particularly strong when one outlier was excluded (r2= 0.88) and among the Dipterocarpaceae$(r^2 = 0.89)$. 5 Log(mortality rate), as determined for all trees per species$\geq 1 cm$d.b.h., increased linearly with$1/M_s$,$1/\rho$and gap fraction. 6 These results suggest an important role for wood density and support costs in the classic tradeoff between rapid growth and increased risks of damage and death.