Data from: Size-related scaling of tree form and function in a mixed-age forest

Many morphological, physiological and ecological traits of trees scale
with diameter, shaping the structure and function of forest ecosystems.
Understanding the mechanistic basis for such scaling relationships is key
to understanding forests globally and their role in Earth's changing
climate system. Here, we evaluate theoretical predictions for the scaling
of nine variables in a mixed-age temperate deciduous forest
(CTFS-ForestGEO forest dynamics plot at the Smithsonian Conservation
Biology Institute, Virginia, USA) and compare observed scaling parameters
to those from other forests world-wide. We examine fifteen species and
various environmental conditions. Structural, physiological and ecological
traits of trees scaled with stem diameter in a manner that was sometimes
consistent with existing theoretical predictions – more commonly with
those predicting a range of scaling values than a single universal scaling
value. Scaling relationships were variable among species, reflecting
substantive ecological differences. Scaling relationships varied
considerably with environmental conditions. For instance, the scaling of
sap flux density varied with atmospheric moisture demand, and herbivore
browsing dramatically influenced stem abundance scaling. Thus,
stand-level, time-averaged scaling relationships (e.g., the scaling of
diameter growth) are underlain by a diversity of species-level scaling
relationships that can vary substantially with fluctuating environmental
conditions. In order to use scaling theory to accurately characterize
forest ecosystems and predict their responses to global change, it will be
critical to develop a more nuanced understanding of both the forces that
constrain stand-level scaling and the complexity of scaling variation
across species and environmental conditions.