Data from: Aboveground biomass is driven by mass-ratio effects and stand structural attributes in a temperate deciduous forest

1.Forest ecosystems are critical for the global regulation of carbon (C),
a substantial portion of which is stored in aboveground biomass (AGB).
While it is well understood that taxonomic and functional composition,
stand structure, and environmental gradients influence spatial variation
in AGB, the relative strengths of these drivers at landscape-scales has
not been investigated in temperate forests. Furthermore, when biodiversity
enhances C storage, it is unclear whether it is through mass-ratio effects
(i.e., the dominant trait in communities regulates AGB) or through niche
complementarity (i.e., increased AGB due to interspecific resource
partitioning). 2.To address these mechanisms, we analyzed data from a
census of 28,262 adult trees sampled across 900 ha of temperate deciduous
forest in southwestern Pennsylvania. We used data on four key plant
functional traits to determine if (1) there is a positive relationship
between species diversity and AGB and (2) whether this is due to
mass-ratio effects or niche complementarity. We also sought to (3)
identify the physical stand structural attributes and topographic
variables that influence AGB across this landscape. 3.We found AGB was
positively related to species richness and negatively related to species
evenness, albeit weakly, while functional diversity indices had neutral
effects. AGB was enhanced in communities dominated by traits related to
greater maximum tree height, deeper minimum rooting depths and larger
seeds. Most importantly, areas with high AGB were dominated by Acer
saccharum and Liriodendron tulipifera. Overall, these results support
mass-ratio effects, with little evidence for niche complementarity.
4.Synthesis: Stand structure, topography, and species and functional
composition, but not taxonomic or functional diversity, were found to be
key drivers of AGB at landscape-scales (<900 ha) in this temperate
deciduous forest. Our findings suggest that simultaneously managing for
both high diversity and for aboveground C storage may prove challenging in
some forest systems. Our results further indicate that the impact of tree
biodiversity loss on aboveground C stocks will depend greatly on the
identity of the species that are lost.