Relationships of phosphorus concentration in reproductive organs with soil phosphorus availability for tropical rain-forest trees on Mount Kinabalu, Borneo

Abstract

Abstract:Bornean rain forests on phosphorus (P)-poor soils exhibit a high P-use efficiency in the production of reproductive organs (i.e. the inverse of P concentration in reproductive-organ litter). The mechanism underpinning this high P-use efficiency is not known, but is hypothesized to result from dilution of P in a given type of reproductive organ and/or a shift of the community composition of flower/fruit types with decreasing P availability. These hypotheses were tested using eight forests with different soil P availabilities on Mount Kinabalu, Borneo. Mean P concentration per forest by genus in inflorescences was significantly positively correlated with P availability, while that in seeds or pericarps was not significantly correlated. This trend was consistent across 21 genera that we analysed, suggesting that P concentration in seeds is maintained in exchange with the dilution of P in inflorescences. The composition of fruit types in tree community was estimated based on the relative abundances of genera in each forest. The relative abundance of capsulate species, which required less P in pericarps, tended to increase in tree community with decreasing P availability. Therefore, both mechanisms were involved in P-use efficiency. This work provides an insight into the reproductive adaptation of trees to P deficiency.

Variations in the reproductive cycle of Bornean montane tree species along elevational gradients on ultrabasic and non‐ultrabasic soils

“…Phylogenetic conservatism is another key aspect of the reproductive phenology of tropical trees (Bawa et al, 2003; Wright & Calderón, 1995). In the present study, the Myrtaceae showed supra‐annual cycles of flowering across sites (Figure 3a), although this family includes capsulate and fleshy‐fruited genera with different P demands for fruiting (Tsujii & Kitayama, 2018). Elevational variation in reproductive phenology was associated with taxa composition.…”

“…This might be explained by efficient P utilization and acquisition, which may shorten the time required to accumulate resources. Among our study sites, it was reported that P concentration in reproductive organs decreased with soil P deficiency (Kitayama et al, 2015; Tsujii & Kitayama, 2018). This may reduce the P requirement per reproduction.…”

“…Mycorrhizal types were categorized using genus‐level data from Soudzilovskaia et al (2020). Fruit‐type data were cited from Tsujii and Kitayama (2018) with slight modification (see Table S1).…”