Data from: Intraspecific variability and reaction norms of forest understory plant species traits

1.Trait-based models of ecological communities typically assume
intraspecific variation in functional traits is not important, though such
variation can change species trait rankings along gradients in resources
and environmental conditions, and thus influence community structure and
function. 2. We examined the degree of intraspecific relative to
interspecific variation, and reaction norms of 11 functional traits for 57
forest understory plant species, including: intrinsic water-use efficiency
(iWUE), Δ15N, 5 leaf traits, 2 stem traits and 2 root traits along
gradients in light, nitrogen, moisture and understory cover. 3. Our
results indicate that interspecific trait variation exceeded intraspecific
variation by at least 50% for most, but not all traits. Intraspecific
variation in Δ15N, iWUE, leaf nitrogen content and root traits was high
(47-70%) compared with most leaf traits and stem traits (13-38%). 4. Δ15N
varied primarily along gradients in abiotic conditions, while light and
understory cover were relatively less important. iWUE was related
primarily to light transmission, reflecting increases in photosynthesis
relative to stomatal conductance. Leaf traits varied mainly as a function
of light availability, with some reaction norms depending on understory
cover. Plant height increased with understory cover, while stem specific
density was related primarily to light. Resources, environmental
conditions and understory cover did not contribute strongly to the
observed variation in root traits. 5. Gradients in resources,
environmental conditions and competition all appear to control
intraspecific variability in most traits to some extent. However, our
results suggest that species cross-over (i.e., trait rank reversals) along
the gradients measured here are generally not a concern. 6. Intraspecific
variability in understory plant species traits can be considerable.
However, trait data collected under a narrow range of environmental
conditions appears sufficient to establish species rankings and scale
between community and ecosystem levels using trait-based models.
Investigators may therefore focus on obtaining a sufficient sample size
within a single set of conditions rather than characterizing trait
variation across entire gradients in order to optimize sampling efforts.