Data from: Disentangling relationships between plant diversity and decomposition processes under forest restoration

Biodiversity has been elucidated to be one of the major factors sustaining
ecosystem functioning. The vast majority of studies showing a relationship
between biodiversity and ecosystem functioning have come from experiments,
and this knowledge has not yet been applied to most real-world cases of
conservation and management. This is especially true in forest ecosystems,
characterized by the dominance of long-lived organisms (trees) and high
levels of structural complexity and environmental heterogeneity. To apply
biodiversity–function relationships to actual forest management, there are
several issues to be considered. These include employing a cross-taxon
perspective, as some functions (e.g. soil biogeochemical processes) cannot
be maintained by a narrow set of organisms, as is usually the case with
experimental systems. More specifically, although the interaction between
above- and below-ground diversity is important for many functions in
forests, there are few studies that evaluated the roles of diversity in
both subsystems in a manner that could be informative in practice. To
evaluate the roles of above- and below-ground diversity to support natural
soil ecosystem functions, we conducted a decomposition experiment in the
northern forests of Japan, which are currently under restoration
management. The restoration area consists of mosaics of different
vegetation types by various revegetation activities and establishment of
ungulate exclosures. Using structural equation modelling and linear
mixed-effects models, we assessed direct and indirect pathways from
diversity to functions by focusing on both of taxonomic and functional
diversity indices. To put our findings into practice, we utilized a
trait-based approach, which provides a link between the functional
consequences of human influences and ecosystem structure. We found little
direct effects of tree diversity on below-ground functions such as
decomposition rate and litter stabilization. However, once the diversities
of understorey herbaceous plants and soil fungi were considered as a
possible mediating explanatory factor, we found a significant effect of
tree diversity to indirectly support these functions by supporting these
other types of biodiversity. Particularly, we found that the models based
on functional trait diversity, rather than on taxonomic species richness,
best explained the variation in below-ground processes. Synthesis and
applications. Forest restoration in the northern forests of Japan has had
no explicit objective to restore soil functions. Nevertheless,
afforestation, and the associated increase in tree diversity as a measure
of forest restoration, was, although often unintentionally, proven
effective for the maintenance of multiple ecosystem functions, such as
soil biogeochemical processes. This finding suggests a great potential for
management to make local tree assemblages functionally dissimilar and
diverse for the sake of supporting and enhancing fundamental ecosystem
functions in forests.