Soil nutrients and size-dependent tree dynamics of tropical lowland forests on volcanic and sedimentary substrates in Sabah, Malaysian Borneo

Abstract

Soil nutrient concentrations and tree dynamics were examined in two Bornean tropical forests on contrasting geological substrates, one on volcanic and the other on sedimentary rocks. Concentrations of P extracted by the Hadley fractionation method and inorganic N of topsoils were much greater in the volcanic site than in the sedimentary site. Dipterocarps showed greater relative growth rates in the volcanic site than in the sedimentary site at the smallest size class (10 cm ≤ diameter at breast height＜20 cm), but not at larger size classes. Dipterocarps in the two sites demonstrated the same values of crown position index (a surrogate of light conditions), implying that the greater tree growth in the volcanic site was associated with the greater soil nutrient availability, but not with light availability. On the other hand, relative growth rates of non-dipterocarps did not differ between the sites at all size classes despite the considerable differences in the soil nutrient concentrations, suggesting that factors other than N and P availabilities limit the growth of these trees. Contrary to growth rate, annual mortality rate was greater in the volcanic site at all size classes for all phylogenetic groups. Our results suggest that the volcanic site is characterized as high soil nutrient availability and a greater tree turnover, and that tree size is an important factor that differentiates tree growth between the two tropical forests with contrasting nutrient availabilities.

Competition and site weakly explain tree growth variability in undisturbed Central African moist forests

“…supposed to have low wood density) was positively linked with total P and N but also Mg and Ca. In Sabah, (Aoyagi et al, 2016) found that total P and N acted significantly only on the growth of small trees belonging to the Dipterocapaceae species (but with no information on their wood density).…”

Breakdown of the growth–mortality trade-off along a soil phosphorus gradient in a diverse tropical forest

“…It remains unclear how mortality rates of tropical tree species vary with fertility, because variation in speciesspecific mortality in relation to soil P gradients has been studied mainly in seedling experiments with a small number of species [13,25,28], while there are many studies examining the relationship between edaphic gradients and stand-level mortality (see below). The growth-mortality trade-off hypothesis predicts that the faster growth rates observed for species adapted to low-P soils in Panama [18,19] should coincide with a higher mortality rate, yet stand-level and seedling mortality rates generally decrease as soil fertility declines across tropical regions [15,[28][29][30][31] (but see [13] for the opposite trend in seedling mortality). A lower mortality rate in infertile environments might be due to greater resource allocation to defence and the reduced effects of natural enemies in species growing in infertile environments [32].…”

Density‐dependent reproductive success among sympatric dipterocarps during a major mast fruiting event

“…Reserve and secondary forests in the Tangkulap Forest Reserve (Imai et al, 2012). The vegetation and soil characteristics at the sites were reported by Aoyagi et al (2016) and Imai et al (2010). Dipterocarp species constituted 47.5% of the relative basal area (RBA) in the primary forest plot.…”