Relationship between root tip morphology and habitat environment across Macaranga and Shorea species in a tropical lowland forest of Peninsula Malaysia

Abstract Aims The relationship between functional trait and habitat environment across tree species provides critical information for understanding the strategy of resource acquisition and utilization of each tree species. Correspondingly, the purpose of this study was to elucidate the relationship between root tip morphology and habitat environment in a primary lowland dipterocarp forest. Methods We surveyed habitat environmental factors for 13 target species of Macaranga and Shorea, i.e., light condition, soil physical properties, and soil nitrogen (N) dynamics, and root tip morphology, including specific root tip length (SRTL), root tip diameter (RTD), and root tip tissue density (RTTD) and analyzed their relationship considering their phylogenetic effect. Results The differences in SRTL and RTD between Macaranga and Shorea species were validated by the difference in environmental factors, i.e., light intensity and soil ammonification rate. With the phylogenetic effect in mind, we detected an interspecific variation in SRTL, RTD, and RTTD in response to differences in environmental factors such as light intensity, soil physical properties, soil nitrification, and N mineralization rates. Among the same species of the trees, the SRTL decreased with increasing light intensity and increased with increasing nitrification rates, while the RTD exhibited an opposite trend. Conclusion We confirmed that the root tip morphology varies according to habitat environment in tropical tree species. However, the variation pattern was different than that of the temperate tree species, implying the existence of factors that determine the direction of root tip morphological variation in response to environmental factors.