Data from: Seedling growth of savanna tree species from three continents under grass competition and nutrient limitation in a greenhouse experiment

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.