Tropical forest seedling trait data collected in Danum Valley, Sabah, Malaysia, in February 2020

Trait data were collected by direct sampling of seedlings adjacent to 75, 1 m2 seedling plots (46 in unlogged primary forest; 26 in logged forest). The length of the longest root and shoot length were measured using a ruler and shoot diameter was measured just below the first branch using precision callipers. Shoot diameter was converted into shoot cross-sectional area based on the assumption that all shoots were circular. To calculate leaf area, all leaves were scanned using a flatbed scanner (CanoScan LiDE 120, Canon Inc., Tokyo, Japan) and analysed using ImageJ software in the R package LeafArea (Katabuchi, 2015). Leaf thickness was measured on three leaves, where available, using precision callipers avoiding any major veins and a mean was calculated. Leaf force to punch was measured at three points on the leaf using a Chantillon DFXII Digital Force Gauge with a 1 mm2 flat head rod (AMETEK Sensors, New York, USA) and the mean was calculated. Leaves, shoots and roots were air-dried before being transferred to the Forest Research Centre, Sepilok, where they were dried to constant weight in an oven at 50 degC before being weighed. Leaf mass fraction and root mass fraction were calculated by dividing dry leaf and dry root mass by total dry mass, respectively. Leaf mass area was calculated by dividing dry leaf mass by leaf area. Leaf area to shoot area ratio was calculated by dividing leaf area by the cross-sectional area of the shoot, root length to shoot length ratio by dividing root length by shoot length and specific maximum root length by dividing maximum root length by dry root mass.

The leaves of the sampled seedlings were combined with additional sample material from the same plot before being analysed for foliar nutrient concentrations at the Forest Research Centre, Sepilok. Leaves were ground using a SM2000 Heavy-duty Cutting Mill (Retsch, Haan, Germany) to pass through a 100-mesh (212 μm) sieve. The ground material was digested using a hydrogen peroxide-sulfuric acid digestion (Allen, 1989). Nleaf and Pleaf were measured colorimetrically using an Astoria-Pacific Flow Analyzer (Astoria-Pacific, OR, USA). Caleaf, Kleaf and Mgleaf were measured spectrometrically using a SpectroArcos FHX22 (Spectro Analytical Instruments, Kleve, Germany). A subsample of the leaves was dried at 105 degC to constant weight to calculate the percentage moisture content and to correct laboratory analyses to an oven dry basis. N:P was calculated by dividing Nleaf by Pleaf.

Related datasets

Tropical forest seedling census data from Danum Valley, Sabah, Malaysia, 2019-2021