DOI: 10.5061/dryad.4f4qrfjh7
title: Data for: Environmental filtering drives biodiversity‒spatial stability relationships in a large temperate forest region

description: The assumption that greater biodiversity enhances ecosystem stability,
 commonly known as "portfolio effect", has attracted considerable
 research attention. However, the potential portfolio effects on spatial
 stability (the similarity of ecosystem functioning among forest
 communities) are still poorly examined especially at different spatial
 scales and under varying environmental stress conditions. Accordingly,
 this study investigates the biodiversity-spatial stability relationship
 among regional communities across different spatial scales and
 environmental conditions in a temperate forest region. We define spatial
 stability as the invariability of the productivity of woody plants among
 plots within a regional community. To test spatial stability, the N
 closest plots to a given plot were aggregated to form regional communities
 representing different spatial scales. Structural equation modeling was
 used to evaluate how biodiversity (including taxonomic (TD) and
 phylogenetic diversity (PD)) increases spatial stability via species
 asynchrony and/or population stability across spatial scales. Hierarchical
 Bayesian modeling was used to evaluate the environmental dependence of the
 portfolio effects on spatial stability. TD and PD both increased spatial
 stability by increasing asynchrony, but decreased population stability.
 The portfolio effect of TD on spatial stability became stronger and
 reached saturation at the intermediate scale and then decreased as
 regional communities became larger. The portfolio effects of TD were
 weaker under the stressful conditions of drought, high precipitation
 seasonality and high elevation but unchanged across temperature
 seasonality and human disturbance. PD showed no discernable effect on
 spatial stability and did not change across spatial scale and
 environmental condition. Our results suggest that the positive effect of
 biodiversity on species asynchrony overcomes the negative biodiversity
 effect on population stability to buffer the spatial change in
 productivity in diverse communities. Future research on the
 biodiversity–spatial stability relationship may thus benefit from
 incorporating different spatial scales and environmental conditions into
 the analysis. 
description: The study region covers a
 large, natural forest area in northeastern China (39°N–54°N latitude,
 119°E–134°E longitude) where coniferous and broadleaved mixed forests
 occur. The region belongs to a temperate continental climate,
 characterized by long and cold winters and warm summers. The annual
 average temperature ranged from -5.6°C to 9.8°C across the regional area.
 The annual average precipitation ranged from 363.8 mm to 1,073.7 mm, with
 more rainfall concentrated from June to September. The total study area
 covered approximately 700,000 km<sup>2</sup>, where the 456
 circular field plots with relatively even cover, each measuring 0.1 ha,
 were used in this study. The elevational range of the study region extends
 from 79 to 1255 m. The N plots closest to the focal plot were
 aggregated to form regional clusters of varying extents. These clusters
 represented local communities of different sizes, which in turn
 represented different regional communities in different geographical
 locations. Each spatial extent included a total of 456 regional
 communities distributed within the temperate forest regions. We used three
 spatial scales with 5, 10 and 20 plot-communities. The spatial extent of
 the three regional communities (N=5, 10 and 20) covers an average distance
 of 48, 76 and 113 km, respectively.