DOI: 10.5061/dryad.280gb5mt9
title: Data for: The interactive effects of soil fertility and tree mycorrhizal association explain spatial variation of diversity-biomass relationships in a subtropical forest

description: Observed biodiversity-ecosystem function (BEF) relationships are highly
 variable, particularly in natural forests. However, our understanding of
 the factors that generate these often contradictory patterns, especially
 the role of different mycorrhizal associations, is still limited. By
 relating tree species richness and aboveground biomass (AGB) in a
 fully-mapped 24-ha subtropical forest dynamics plot, we evaluated the
 impacts of soil fertility and tree mycorrhizal type in mediating BEF
 relationships at multiple spatial scales. Our results demonstrate a highly
 positive total richness effect on AGB for arbuscular mycorrhizal (AM)
 trees but a negative effect on AGB for ectomycorrhizal (EcM) trees, and
 their relationships were highly spatial scale dependent. However, the
 observed BEF relationships turned into positive at small spatial scales
 (i.e., 10 m and 20 m) after controlling for other confounding factors
 (i.e., topography, soil fertility, and AM proportion). In addition, we
 found significant interactions between soil fertility and species richness
 on AGB. Specifically, the positive effect of total species richness on AGB
 for major mycorrhizal types gradually weakened with increasing soil
 fertility, while the positive effect of EcM species richness on AM AGB
 gradually enhanced at small spatial scales, suggesting the observed
 diversity effects can be largely attributed to resource niche
 complementarity and the role of EcM fungi. Synthesis. We conclude that the
 variable BEF relationships among forest communities could be explained by
 spatial variation in abiotic environments and community mycorrhizal
 composition because different types of symbionts perform different
 nutrient uptake strategies and ability in protection from antagonists. Our
 findings provide novel insights into the understanding of the variation in
 the shape of BEF relationships in natural forests, which is critical for
 forest management, conservation, and restoration in a changing world.
description: Our study was conducted in a 24-ha subtropical
 evergreen broad-leaved forest dynamics plot in the Gutianshan (GTS)
 National Nature Reserve (29°15′N, 118°07′E), in eastern China. This area is characterized by a subtropical
 monsoon climate and mean annual temperature is 15.3℃ and annual precipitation is 1963.7 mm. The
 major soil group is a subtropical red clay soil, equivalent to Ultisols in
 the US taxonomy. The GTS
 plot was established in 2005 as part of the Chinese Forest Biodiversity
 Monitoring Network (CForBio) and the Center for Tropical Forest
 Science-Forest Global Earth Observatory
 (CTFS-ForestGEO). In this
 plot, all woody stems with diameter at breast height (DBH, 1.3 m above
 ground) ≥1 cm was tagged, mapped, measured, and identified to species
 following the CTFS-ForestGEO tree census protocol. We assign a unique
 mycorrhizal status to each tree species based on the FungalRoot
 database. In total, the
 GTS plot contained 133 arbuscular mycorrhizal (AM), 13 ectomycorrhizal
 (EcM), 3 N-fixing, and 10 ericoid mycorrhizal (ErM) plant species in the
 initial census.