Data from: The value of biodiversity for the functioning of tropical forests: insurance effects during the first decade of the Sabah biodiversity experiment

One of the main environmental threats in the tropics is selective logging,
which has degraded large areas of forest. In southeast Asia, enrichment
planting with seedlings of the dominant group of dipterocarp tree species
aims to accelerate restoration of forest structure and functioning. The
role of tree diversity in forest restoration is still unclear, but the
‘insurance hypothesis’ predicts that in temporally and spatially varying
environments planting mixtures may stabilize functioning owing to
differences in species traits and ecologies. To test for potential
insurance effects, we analyse the patterns of seedling mortality and
growth in monoculture and mixture plots over the first decade of the Sabah
biodiversity experiment. Our results reveal the species differences
required for potential insurance effects including a trade-off in which
species with denser wood have lower growth rates but higher survival. This
trade-off was consistent over time during the first decade, but growth and
mortality varied spatially across our 500 ha experiment with species
responding to changing conditions in different ways. Overall, average
survival rates were extreme in monocultures than mixtures consistent with
a potential insurance effect in which monocultures of poorly surviving
species risk recruitment failure, whereas monocultures of species with
high survival have rates of self-thinning that are potentially wasteful
when seedling stocks are limited. Longer-term monitoring as species
interactions strengthen will be needed to more comprehensively test to
what degree mixtures of species spread risk and use limited seedling
stocks more efficiently to increase diversity and restore ecosystem
structure and functioning.