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 (Vc_max) and maximum electron transport (J_max) 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 Vc_max.  Pinus exhibited a higher Vc_max than Podocarpaceae, resulting in a less steep slope in the linear relationship between J_max and Vc_max.  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.

All data including A-C_i curves and light response curves (with additional points below 100 µmol_PAR m^-2 s^-1 for analysis of respiration in the light via the Kok method) were collected using an LI-6800 on potted conifer saplings growing in a shade house at Bidoup Nui Ba National Park Headquarters in the Central Highlands of Vietnam in January 2017.  See publication in Tree Physiology for full methods.

Each file contains a "metadata" tab with column names, descriptions and units, as well as a "data" tab.
 
Missing data, or data removed due to measurement error are denoted by "NA".

SSchmiege_Table1_leaftraits.xlsx
All foliar traits included in the analysis.

SSchmiege_Table2_Aci_curves_raw.xlsx
Output of the raw LI-6800 Aci curves.

SSchmiege_Table3_LightResponse_curves_raw.xlsx
Output of the raw LI-6800 light response curves (modified with additional points below 100 µmol_PAR m^-2 s^-1 for analysis of respiration in the light via the Kok method).