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Dryad

Data From: Contrasting physiological traits of shade tolerance in Pinus and Podocarpaceae native to a tropical Vietnamese forest: Insight from an aberrant flat-leaved pine

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Abstract

The absence of pines from tropical forests is a puzzling biogeographical oddity potentially explained by traits of shade intolerance.  Pinus krempfii, a flat-leaved pine endemic to the Central Highlands of Vietnam, provides a notable exception as it seems to successfully compete with shade-tolerant tropical species.  Here, we test the hypothesis that successful conifer performance at the juvenile stage depends on physiological traits of shade tolerance by comparing the physiological characteristics of P. krempfii to coexisting species from the genus Pinus and from the Podocarpaceae, a relatively abundant and shade tolerant conifer family found in pantropical forests.  We examined leaf photosynthetic, respiratory and biochemical traits.  Additionally, we compiled attainable maximum photosynthesis, maximum RuBP carboxylation (Vcmax) and maximum electron transport (Jmax) values for Pinus and Podocarpaceae species from the literature.  In our literature compilation, P. krempfii was intermediate between Pinus and Podocarpaceae in its maximum photosynthesis and its VcmaxPinus exhibited a higher Vcmax than Podocarpaceae, resulting in a less steep slope in the linear relationship between Jmax and Vcmax.  These results suggest that Pinus may be more shade intolerant than Podocarpaceae with P. krempfii falling between the two groups.  However, in contrast, Vietnamese conifers’ leaf mass per areas and biochemical traits did not highlight the same intermediate nature of P. krempfii.  Furthermore, regardless of leaf shape or family assignation, all species demonstrated a common carbon gain efficiency.  Overall, our findings highlight the importance of shade tolerance for conifer survival in tropical forests.  However, they also demonstrate a diversity of shade tolerance strategies, all of which lead to the persistence of Vietnamese juvenile conifers in low-light tropical understories.