Plant growth forms determine root resource acquisition strategy along ‘fast-slow’ economics spectrum in a temperate forest community

While root acquisition strategies at regional and global scales are
broadly associated with climate, soil resource availability, and plant
phylogeny, there is additional variation in functional traits at the local
scale that is substantial, yet remains poorly understood. We sampled 115
species across five growth forms (trees, shrubs, lianas, herbs, and ferns)
from a temperate forest and measured seven key functional traits of
first-order roots. Most trait variations were greater among growth forms
than within them. Root tissue density (RTD) and specific root length (SRL)
showed the highest variation compared with other traits. Variance
partitioning analysis revealing the growth form showed the largest
explaining of RTD and SRL variations. Among the five growth forms, herbs
had the thinnest root diameter, highest root nitrogen concentration, and
longest SRL, as well as the lowest ratio of root carbon to nitrogen, while
ferns exhibited the thickest cortex thickness and stele diameter. Compared
with trees and shrubs, lianas had longer SRL and lower RTD. Importantly,
species aggregated in root economics space separately by growth forms,
illustrating consistent differences in soil resource strategies among
growth forms from fast to slow acquisition. Discriminant function analysis
(DFA) demonstrated the primary roles of RTD and SRL in separating
different growth forms within the root economics space. Such diverse
strategies among plant growth forms may allow species to avoid strong
competition and promote species coexistence in a local forest community.
These findings improve our understanding of the mechanisms underlying
community assembly and stability from a below-ground perspective.