Nitrogen and phosphorus enhance growth and luxury consumption of four secondary forest tree species in Borneo

Four common fallow tree species were tested for a response to nitrogen and phosphorus fertilization. Seedlings or cuttings of Melicope glabra (Rutaccae), Macaranga gigantea (Euphorbiaceae), Persea romosa (Laureaceae), Peronema canescens (Verbenaceae) were grown in pots of a 50:50 mix of native soil and sand under 18% full sun for 18 weeks. Every 2 weeks, plants received either added N, added P, added N+P, or no added nutrients (control). Persea, a shade-tolerant species, and Macaranga, a light-demanding pioneer, improved relative growth rate with the addition of both N and P. Neither responded to N or P alone. Peronema and Melicope demonstrated luxury consumption of both N and P but did not show enhanced growth. Two of the four species tested (Persea and Melicope) were more limited by P than N. Macaranga was equally limited by both and Peronema was more limited by N. Along with previous studies, evidence for positive growth response and luxury consumption among light-demanding species suggests that P. rather than N, should limit seedling performance and may ultimately influence tree diversity in young secondary tropical forests.