DOI: 10.5061/dryad.k7729
title: Data from: Limitation of seedling growth by potassium and magnesium supply for two ectomycorrhizal tree species of a Central African rain forest and its implication for their recruitment

description: In the ectomycorrhizal caesalpiniaceous groves of southern Korup National
 Park, the dominant tree species, Microberlinia bisulcata, displays very
 poor in situ recruitment compared with its codominant, Tetraberlinia
 bifoliolata. The reported ex situ experiment tested whether availabilities
 of soil potassium and magnesium play a role. Seedlings of the two species
 received applications of K and Mg fertilizer in potted native soil in a
 local shade house, and their responses in terms of growth and nutrient
 concentrations were recorded over 2 years. Amended soil concentrations
 were also determined. Microberlinia responded strongly and positively in
 its growth to Mg, but less to K; Tetraberlinia responded weakly to both.
 Added Mg led to strongly increased Mg concentration for Microberlinia
 while added K changed that concentration only slightly; Tetraberlinia
 strongly increased its concentration of K with added K, but only somewhat
 its Mg concentration with added Mg. Additions of Mg and K had small but
 important antagonistic effects. Microberlinia is Mg-demanding and
 apparently Mg-limited in Korup soil; Tetraberlinia, whilst K-demanding,
 appeared not to be K-limited (for growth). Added K enhanced plant P
 concentrations of both species. Extra applied Mg may also be alleviating
 soil aluminum toxicity, and hence improving growth indirectly and
 especially to the benefit of Microberlinia. Mg appears to be essential for
 Microberlinia seedling growth and its low soil availability in grove soils
 at Korup may be an important contributing factor to its poor recruitment.
 Microberlinia is highly shade-intolerant and strongly light-responding,
 whilst Tetraberlinia is more shade-tolerant and moderately
 light-responding, which affords an interesting contrast with respect to
 their differing responses to Mg supply. The study revealed novel aspects
 of functional traits and likely niche-partitioning among ectomycorrhizal
 caesalps in African rain forests. Identifying the direct and interacting
 indirect effects of essential elements on tropical tree seedling growth
 presents a considerable challenge due the complex nexus of causes
 involved.
description: Growth over three
 periodsHeight (ht, in cm), and
 numbers of leaves (lvn) and branches (brn), over three periods of the
 experiment for seedlings of Microberlinia bisulcata (Mb) and Tetraberlinia
 bifoliolata (Tb). Blank cells are where plants were lost or died. Periods
 1 to 3 were measured at nine, five and five dates respectively. The design
 consisted of 16 treatments (trmt), in four blocks (block), with a 4 x 4
 factorial arrangement of the two addition factors potassium (K) and
 magnesium (Mg), for which level numbers are shown (‘1,1’ was the control).
 There were four replicates of each treatment per species and block at the
 start, and one was removed at each of the tree harvests (H1, H2 and H3).
 The far right columns list individual plant ‘shock’ values (see main
 paper) used as a covariate. Mean of growth variables for treatments and
 harvests are given in Table S1 of the paper.Mb&Tb_growth1-3.xlsxHarvest dry masses and leaf nutrientsHeight (cm), numbers of leaves and branches, basal stem diameter (mm), leaf area (cm2; only H2 and H3) for each of the three harvests (Harv 1-3); oven-dried mass (DM, in g) for leaves, roots, stems and totals for each plant; and the nutrient concentrations of five macro-elements (P, N, Ca, K, and Mg; in µg g-1 DM) in their leaves (L), for seedlings of Microberlinia bisulcata (Mb) and Tetraberlinia bifoliolata (Tb). Blank cells are where plants had died and there was no material for analysis. The corresponding values for the covariate ‘shock’ are also given. Design and layout: as described for ‘Mb&Tb_growth1-3.xlsx’. Means of dry masses and nutrient concentrations for treatments and harvests are given in Tables 1 and 2 of the paper.Mb&Tb_harv&nutrL.xlsxRoot and shoot nutrientsNutrient concentrations of five macro-elements (P, N, Ca, K, and Mg; in µg g-1 DM) in roots (R) and stems (S) at harvest 2 for seedlings of Microberlinia bisulcata (Mb) and Tetraberlinia bifoliolata (Tb): details are as for leaves in ‘Mb&Tb_harv&nutrL.xlsx’. Blank cells are where plants had died and there was no material for analysis. Design and layout: as described for ‘Mb&Tb_growth1-3.xlsx’. Means of nutrient concentrations for treatments and harvests are given in Tables S2a, b of the paper.Mb&Tb_nutrR&S.xlsxNutrients in pot soilsConcentrations of extractable cations (Ca, K and Mg, as µg g-1 dry weight) in pot soils at harvests (Harv) 1 and 2, taken at two positions (Pos: U, upper; L, lower). Design and layout: as described for ‘Mb&Tb_growth1-3.xlsx’. Means of cation concentrations for treatments, positions and harvests are given in Tables S3a, b of the paper.Mb&TB_nutr-soils.xlsx