Data from: Stand structural diversity rather than species diversity enhances aboveground carbon storage in secondary subtropical forests in Eastern China

Stand structural diversity, typically characterized by variances in tree
diameter at breast height (DBH) and total height, plays a critical role in
influencing aboveground carbon (C) storage. However, few studies have
considered the multivariate relationships of aboveground C storage with
stand age, stand structural diversity, and species diversity in natural
forests. In this study, aboveground C storage, stand age, tree species,
DBH and height diversity indices, were determined across 80 subtropical
forest plots in Eastern China. We employed structural equation modelling
(SEM) to test for the direct and indirect effects of stand structural
diversity, species diversity, and stand age on aboveground C storage. The
three final SEMs with different directions for the path between species
diversity and stand structural diversity had a similar goodness of fit to
the data. They accounted for 82 % of the variation in aboveground C
storage, 55–59 % of the variation in stand structural diversity, and 0.1
to 9 % of the variation in species diversity. Stand age demonstrated
strong positive total effects, including a positive direct effect
(β =  0.41), and a positive indirect effect via stand structural diversity
(β =  0.41) on aboveground C storage. Stand structural diversity had a
positive direct effect on aboveground C storage (β =  0.56), whereas there
was little total effect of species diversity as it had a negative direct
association with, but had a positive indirect effect, via stand structural
diversity, on aboveground C storage. The negligible total effect of
species diversity on aboveground C storage in the forests under study may
have been attributable to competitive exclusion with high aboveground
biomass, or a historical logging preference for productive species. Our
analyses suggested that stand structural diversity was a major determinant
for variations in aboveground C storage in the secondary subtropical
forests in Eastern China. Hence, maintaining tree DBH and height diversity
through silvicultural operations might constitute an effective approach
for enhancing aboveground C storage in these forests.