DOI: 10.5061/dryad.b8gtht78m
title: Above- and below-ground biodiversity jointly regulate temperate forest multifunctionality along a local-scale environmental gradient

description: 1. Tree diversity has been shown to promote a broad range of ecosystem
 functions in forests. However, how important these effects are in driving
 ecosystem multifunctionality in natural forests, relative to other
 drivers, such as below-ground biodiversity (e.g., soil microbial
 diversity), community-level functional traits and environmental
 conditions, remains poorly understood. Here, we hypothesise that tree
 species or phylogenetic diversity, stand structure, functional traits and
 soil microbial diversity jointly regulate temperate forest
 multifunctionality along a local-scale environmental gradient. 2. Using
 repeated census data from a 25-ha old-growth temperate forest, we first
 quantified eight ecosystem functions and properties related to above- and
 below-ground nutrient cycling. We then used these to estimate ecosystem
 multifunctionality using both an averaging and multiple thresholds (50,
 75, and 95%) approaches. Finally, we used structural equation models to
 explore how different facets of tree (tree species, functional and
 phylogenetic diversity) and soil (bacteria, fungi, and nematode diversity)
 biodiversity influence ecosystem multifunctionality, as well as how these
 relationships are modulated by stand structural attributes and
 environmental conditions (topography and soil nutrients). 3. Forest
 multifunctionality was positively related to stand structural complexity
 but negatively related to acquisitive traits (i.e. community-weighted mean
 of specific leaf area). Plant phylogenetic diversity had no significant
 direct effect on forest multifunctionality, but it had a significant
 indirect effect via increased stand structural complexity. The effect of
 soil microbial diversity on forest multifunctionality increased with
 increasing threshold levels of forest multifunctionality and outperformed
 tree diversity and environmental conditions at the highest threshold level
 (i.e. 95%). Forests on steep slopes had lower levels of ecosystem
 multifunctionality due to decreased stand structural complexity. Soil
 nutrients were responsible for regulating forest multifunctionality via
 plant trait composition and, to a lesser extent, via tree diversity, stand
 structure and soil microbial diversity. 4. Synthesis: Plant phylogenetic
 diversity, stand structure and soil microbial diversity jointly regulated
 forest multifunctionality, and these effects were influenced by
 local-scale changes in environmental conditions. Soil microbial diversity
 was a key driver of highly multifunctional forests, whereas conservation
 of complex stand structure and conservative trait dominance could enhance
 mean values of multiple functions. 1. Tree diversity has been shown to
 promote a broad range of ecosystem functions in forests. However, how
 important these effects are in driving ecosystem multifunctionality in
 natural forests, relative to other drivers, such as below-ground
 biodiversity (e.g., soil microbial diversity), community-level functional
 traits and environmental conditions, remains poorly understood. Here, we
 hypothesise that tree species or phylogenetic diversity, stand structure,
 functional traits and soil microbial diversity jointly regulate temperate
 forest multifunctionality along a local-scale environmental gradient. 2.
 Using repeated census data from a 25-ha old-growth temperate forest, we
 first quantified eight ecosystem functions and properties related to
 above- and below-ground nutrient cycling. We then used these to estimate
 ecosystem multifunctionality using both an averaging and multiple
 thresholds (50, 75, and 95%) approaches. Finally, we used structural
 equation models to explore how different facets of tree (tree species,
 functional and phylogenetic diversity) and soil (bacteria, fungi, and
 nematode diversity) biodiversity influence ecosystem multifunctionality,
 as well as how these relationships are modulated by stand structural
 attributes and environmental conditions (topography and soil nutrients).
 3. Forest multifunctionality was positively related to stand structural
 complexity but negatively related to acquisitive traits (i.e.
 community-weighted mean of specific leaf area). Plant phylogenetic
 diversity had no significant direct effect on forest multifunctionality,
 but it had a significant indirect effect via increased stand structural
 complexity. The effect of soil microbial diversity on forest
 multifunctionality increased with increasing threshold levels of forest
 multifunctionality and outperformed tree diversity and environmental
 conditions at the highest threshold level (i.e. 95%). Forests on steep
 slopes had lower levels of ecosystem multifunctionality due to decreased
 stand structural complexity. Soil nutrients were responsible for
 regulating forest multifunctionality via plant trait composition and, to a
 lesser extent, via tree diversity, stand structure and soil microbial
 diversity. 4. Synthesis: Plant phylogenetic diversity, stand structure and
 soil microbial diversity jointly regulated forest multifunctionality, and
 these effects were influenced by local-scale changes in environmental
 conditions. Soil microbial diversity was a key driver of highly
 multifunctional forests, whereas conservation of complex stand structure
 and conservative trait dominance could enhance mean values of multiple
 functions. 1. Tree diversity has been shown to promote a broad range of
 ecosystem functions in forests. However, how important these effects are
 in driving ecosystem multifunctionality in natural forests, relative to
 other drivers, such as below-ground biodiversity (e.g., soil microbial
 diversity), community-level functional traits and environmental
 conditions, remains poorly understood. Here, we hypothesise that tree
 species or phylogenetic diversity, stand structure, functional traits and
 soil microbial diversity jointly regulate temperate forest
 multifunctionality along a local-scale environmental gradient. 2. Using
 repeated census data from a 25-ha old-growth temperate forest, we first
 quantified eight ecosystem functions and properties related to above- and
 below-ground nutrient cycling. We then used these to estimate ecosystem
 multifunctionality using both an averaging and multiple thresholds (50,
 75, and 95%) approaches. Finally, we used structural equation models to
 explore how different facets of tree (tree species, functional and
 phylogenetic diversity) and soil (bacteria, fungi, and nematode diversity)
 biodiversity influence ecosystem multifunctionality, as well as how these
 relationships are modulated by stand structural attributes and
 environmental conditions (topography and soil nutrients). 3. Forest
 multifunctionality was positively related to stand structural complexity
 but negatively related to acquisitive traits (i.e. community-weighted mean
 of specific leaf area). Plant phylogenetic diversity had no significant
 direct effect on forest multifunctionality, but it had a significant
 indirect effect via increased stand structural complexity. The effect of
 soil microbial diversity on forest multifunctionality increased with
 increasing threshold levels of forest multifunctionality and outperformed
 tree diversity and environmental conditions at the highest threshold level
 (i.e. 95%). Forests on steep slopes had lower levels of ecosystem
 multifunctionality due to decreased stand structural complexity. Soil
 nutrients were responsible for regulating forest multifunctionality via
 plant trait composition and, to a lesser extent, via tree diversity, stand
 structure and soil microbial diversity. 4. Synthesis: Plant phylogenetic
 diversity, stand structure and soil microbial diversity jointly regulated
 forest multifunctionality, and these effects were influenced by
 local-scale changes in environmental conditions. Soil microbial diversity
 was a key driver of highly multifunctional forests, whereas conservation
 of complex stand structure and conservative trait dominance could enhance
 mean values of multiple functions.