DOI: 10.5061/dryad.2ngf1vhvm
title: Root-centric β diversity reveals functional homogeneity while phylogenetic heterogeneity in a subtropical forest

description: Root-centric studies have revealed fast taxonomic turnover across root
 neighborhoods, but how such turnover is accompanied by changes in species
 functions and phylogeny (i.e. β diversity), which can reflect the degree
 of community-wide biotic homogenization, remains largely unknown,
 hindering better inference of below-ground assembly rules, community
 structuring, and ecosystem processes. We collected 2480 root segments from
 625 0–30 cm soil profiles in a subtropical forest in China. Root segments
 were identified into 143 species with DNA-barcoding with six root
 morphological and architectural traits measured per species. By using the
 mean pairwise (Dpw) and mean nearest neighbor distance (Dnn) to quantify
 species ecological differences, we tested the non-random functional and
 phylogenetic turnover of root neighborhoods that would lend more support
 to deterministic over stochastic community assembly processes, examined
 the distance-decay pattern of β diversity, and finally partitioned β
 diversity into geographical and environmental components to infer their
 potential drivers of environmental filtering, dispersal limitation, and
 biotic interactions. We found that functional turnover was often lower
 than expected given the taxonomic turnover, whereas phylogenetic turnover
 was often higher than expected. Both functional and phylogenetic Dpw (e.g.
 interfamily species) turnover exhibited a distance-decay pattern, likely
 reflecting limited dispersal or abiotic filtering that leads to the
 spatial aggregation of specific plant lineages. Conversely, phylogenetic
 Dnn (e.g. intrageneric species) exhibited an inverted distance-decay
 pattern, likely reflecting strong biotic interactions among spatially and
 phylogenetically close species leading to phylogenetic divergence. While
 the spatial distance was generally a better predictor of β diversity than
 environmental distance, the joint effect of environmental and spatial
 distance usually overrode their respective pure effects. These findings
 suggest that root neighborhood functional homogeneity may somewhat
 increase forest resilience after disturbance by exhibiting an insurance
 effect. Likewise, root neighborhood phylogenetic heterogeneity may enhance
 plant fitness by hindering the transmission of host-specific pathogens
 through root networks or by promoting interspecific niche complementarity
 not captured by species functions. Our study highlights the potential role
 of root-centric β diversity in mediating community structures and
 functions largely ignored in previous studies.
description: We randomly collected root materials from 625 soil cores (i.e.,
 root neigbourhoods) in a subtropical forest. Species were identified with
 DNA-barcoding and their morphologies. Soil variables were measued within a
 distance of 10 cm from the root-sampling core.The spatial distances of
 soil cores were quantified based on the coordinates of the cores. Species
 phylogeny was onstructed based on DNA sequence. Species root morphological
 and archetectural traits were measured with WinRHIZO.
description: These datasets were collected in the Guangdong Heishiding Dynamic
 Forest Plot in Southern China (2016). Details for each dataset are
 provided in the README file.
description: # Beta diversity among root neigbourhoods *** In this study, we looked at
 the functional and phylogenetic turnover rate (e.g., dissimilarity of
 functional traits and phylogenetic relatedness among species ) of
 root-centric species among root neighbourhoods (e.g., soil patches where
 multiple heterospecific roots cooccur) in a subtropical forest in southern
 China. The study aimed to compare the turnover rate of functions and
 phylogeny with that of plant taxonomy. Trait dissimilarity among species
 was quantified based on six root functional traits with species
 phylogenetic relatedness quantified based on a phylogeny. Multiple abiotic
 variables were measured at the soil core level such as topographical
 variables (e.g., elevation) and soil variables (e.g., soil nitrogen and
 phosphorus content). ## Description of the data and file structure 1. the
 [Root.trait.data] file is composed of 138 rows and 7 columns. Each row
 indicates one species named as "species", and the remaining rows
 indicate six functional traits of fine roots as explained below. 1\.
 Average diameter: Averaged diameter of fine roots \(mm\)\. 2\. Specific
 root length: Length per unit dry mass of fine roots \(cm/mg\)\.      3\.
 Specific root tip abundance: Number of root tips per unit dry mass of fine
 roots \(tips/mg\)\. 4\. Specific root surface area: Surface area per unit
 dry mass of fine roots \(cm<sup>2</sup>/mg). 5\. Root tissue
 density: Mass per unit volume of fine roots
 \(mg/cm<sup>3</sup>). 6\. Root branching intensity: Number of
 root tips per unit cm of fine roots \(tips/cm\)\. 2. the
 [Soil.topographical.variables] file is composed of 625 rows and 22
 columns. Each row indicates one sampling location named as “site”, and the
 remaining 21 rows indicate the measured topographical and soil variables
 as explained below. 1\. Site: sampling location 2\. gx: the x coordinate
 of the sampling location in the 500![]() by 1000 m forest plot. 3\. gy:
 the y coordinate of the sampling location in the 500 by 1000 m forest
 plot\. 4\. Altitude: altitude of the sampling location \(m\)\. 5\. Slope:
 slope of the sampling location \(degree\)\. 6\. Aspect: aspect of the
 sampling location \(degree\)\. 7\. Curvature: curvature of the sampling
 location\. 8\. Soil pH: soil pH of the sampling location\. 9\. Soil total
 nitrogen: soil total nitrogen content of the sampling location \(g/kg\)\.
 10\. Total phosphorus: soil total phosphorus content of the sampling
 location \(g/kg\)\. 11\. Total potassium: soil total potassium content of
 the sampling location \(g/kg\)\. 12.  Available phosphorus:soil available
 phosphorus content of the sampling location (mg/kg). 13.  Available
 potassium: soil available potassium of the sampling location (mg/kg). 14. 
 Soil volumetric sand content: soil volumetric sand content of the sampling
 location (%). 15.  Available copper: soil available copper of the sampling
 location (mg/kg). 16.  Available zinc: soil available zinc of the sampling
 location (mg/kg). 17.  Available iron: soil available iron of the sampling
 location (mg/kg). 18.  Available manganese: soil available manganese of
 the sampling location (mg/kg). 19.  Exchangeable magnesium: soil
 exchangeable magnesium of the sampling location (mg/kg). 20.  Exchangeable
 base cations: soil exchangeable base cations of the sampling location
 (cmol/kg). 21.  Available boron: soil available boron of the sampling
 location (mg/kg). 22.  Exchangeable aluminum: soil exchangeable aluminum
 of the sampling location (cmol/kg). 3. the [Root.community.data] file is
 composed of 609 rows and 138 columns. Each row indicates one sampling
 location names as “site”, and the remaining 138 rows indicate the
 presence/ absence of the study138 species in a root neighbourhoods (e.g.
 soil patches). 4. the [Phylogeny.data] file stores phylogeny of 152
 species including the study 138 species. The file can be opened with
 “TexEdit”. ## Code/Software Data files are processed with R.