DOI: 10.5061/dryad.745g830
title: Data from: Seedling growth of savanna tree species from three continents under grass competition and nutrient limitation in a greenhouse experiment

description: 1. Changes in savanna tree species composition, both within landscapes and
 across climatic gradients, suggest that species differ in their ability to
 utilise resources and cope with grass competition. Linking trait variation
 among species to their relative performance under resource limitation and
 competition treatments could provide mechanistic understanding of species’
 turnover across environmental gradients in savannas. We investigated how
 tree species differ in response to competition from grasses and nutrient
 supply, and whether these responses can be related to plant traits. As
 humid savannas are often associated with low fertility, species of humid
 savannas may grow more efficiently under nutrient suppression than species
 from semi-arid savannas. In heterogeneous grass swards, fast-growing,
 resource-wasteful species may be found in short-grass patches and
 slow-growing, resource-conservative species in tall-grass patches. 2. We
 compared seedlings of 40 tree species sampled from humid and semi-arid
 savannas of three continents (Africa, Australia, South America) with and
 without grass competition and with high and low nutrient supply. We
 measured traits related to soil resource capture, light capture and
 growth, and tested whether these traits were related to performance under
 the four treatments. 3. All tree species were suppressed by grass
 competition and most by nutrient limitation. Only species from humid
 savannas in Australia grew better under nutrient limitation than their
 semi-arid counterparts. Deciduous species from semi-arid climates were
 more negatively impacted by grass competition than deciduous species from
 humid climates whereas the reverse pattern was observed among evergreen
 species. Faster growing species were more severely suppressed by grass
 competition and low nutrients than slower growing species. Traits
 associated with soil resource capture and seed mass supported growth under
 grass competition and nutrient limitation, but the traits differed by
 continent and by leaf habit. 4. Synthesis: We found limited evidence that
 tree seedlings from humid savannas grow better under nutrient limitation
 than species of semi-arid savannas. We confirmed that fast-growing species
 may be advantaged in short-grass patches and conservative species may be
 advantaged in tall-grass patches. Traits that improved performance under
 grass competition differed by continent, which may relate to differences
 in leaf habit and constraints on seed size.
description: Tomlinson JECOL-2018
 Individual dataData is for measurements
 taken on individuals at 0, 5 and 20 weeks after planting. Data for each
 age of sampling are recorded in separate sheets. Traits measured at 0
 weeks were: initial mass of recently germinated seedlings (Mass0, g).
 Traits measured at 5 weeks were: root extension rate (RER, mm d-1), and
 specific taproot length (STRL, m g-1). Traits measured at 20 weeks were:
 total mass (Mass, g), root mass fraction (RMF, g root mass g-1 total
 mass), stem extension rate (SER, mm d-1), specific leaf area (SLA, cm2
 g-1), leaf nitrogen content (Nm, mg N g-1), leaf phosphorus content (Pm,
 mg P g-1), leaf potassium content (Km, mg K g-1), leaf assimilation rate
 (Am, nmol CO2 g-1 s-1), stomatal conductance (gs, μmol H2O m-2 s-1), and
 plant photosynthetic water use efficiency (PWUE, μmol CO2 μmol-1
 H2O).Tomlinson JECOL-2018-0362R2
 Individual data.xlsx