Data and code from: Species turnover drives responses of community fine-root traits to recurrent droughts

Data files

Jun 24, 2026 version files 14.36 KB

FD.csv

5.66 KB
README.md

5.33 KB
TableS2_CWM_LMM.R

1.51 KB
TableS3_FDis_LMM.R

1.86 KB

Abstract

Fine roots and their traits are critical for plant drought adaptation, yet predicting their responses to recurrent droughts remains a key challenge under climate change. We conducted a repeated extreme drought experiment across four semiarid grasslands along an aridity gradient. We compared the effects of single (precipitation reduction in 2021-2023) versus recurrent droughts (precipitation reduction in both 2015-2018 and 2021-2023) on community-weighted means (CWMs) and functional diversity of fine root traits. We also examined the relative contributions of intra- and interspecific variation to both CWMs and trait diversity under repeated droughts. Results showed that the CWMs or functional diversity of key fine root traits (diameter, specific length/area, tissue density) varied among grasslands. However, neither single nor recurrent drought altered these traits in any site, indicating community trait conservatism under drought. This resistance was driven by joint contributions of intra- and interspecific variation buffering changes in community trait values. Intraspecific variation prevailed under a single drought, whereas interspecific variation increased under recurrent drought. Furthermore, recurrent drought altered dominance within the intermediate-trait range, favoring different grasses (e.g., Leymus chinensis) than those favored by single drought (e.g., Stipa grandis). However, fine root trait CWMs and diversity showed either non-significant or very weak correlations with grassland primary productivity under drought. Synthesis. Our study reveals a dual response in grasslands to repeated drought, where community fine root traits maintain high resistance through species turnover. This suggests that community functional responses to climate extremes cannot be inferred from species trait shifts alone.

Description of the data and file structure

This data package contains the processed dataset and R scripts used to reproduce the linear mixed-effects model analyses of community-weighted mean fine-root traits and functional diversity reported in Tables S2 and S3.

The package includes three files:

FD.csv: the main processed dataset containing site, block, drought treatment, aboveground net primary productivity (ANPP), community-weighted mean (CWM) fine-root traits, and functional dispersion (FDis) metrics.
TableS2_CWM_LMM.R: R script used to analyze the effects of drought treatment, site, and their interaction on community-weighted mean fine-root traits.
TableS3_FDis_LMM.R: R script used to analyze the effects of drought treatment, site, and their interaction on multivariate and single-trait functional dispersion.

The dataset was generated from a repeated drought experiment conducted across four grassland sites in northern China. The experiment included three drought treatments: control, single drought, and recurrent drought. In the dataset, these treatments are coded as control, single, andrecurrent, respectively.

The experimental design included four sites and three drought treatments. The IMG-2 site had three blocks, whereas the other three sites had six blocks. Therefore, the expected total number of observations is 63 rows.

Files and variables

File: FD.csv

Description:
This file contains plot-level data used for linear mixed-effects model analyses of community-weighted mean fine-root traits and functional dispersion.

Each row represents one plot-level observation from a specific site, block, and drought treatment.

Experimental design variables

site: grassland site. Four sites are included:
- EFS: Erguna Forest-Steppe Ecotone Research Station
- IMG-1: Inner Mongolia Grassland Ecosystem Research Station-1
- IMG-2: Inner Mongolia Grassland Ecosystem Research Station-2
- NHG: National Hulunber Grassland Ecosystem Observation and Research Station
block: block identifier within each site.
treat: drought treatment. Three treatment levels are included:
- control: ambient precipitation control
- single: single drought treatment
- recurrent: recurrent drought treatment

Productivity variable

ANPP: aboveground net primary productivity, calculated as the total dry biomass of all species within each plot. Unit: g m^-2.

Functional dispersion variables

FDis: functional dispersion calculated in multivariate fine-root trait space.
RDFDIS: functional dispersion calculated using root diameter only.
SRLFDIS: functional dispersion calculated using specific root length only.
SRAFDIS: functional dispersion calculated using specific root area only.
RTDFDIS: functional dispersion calculated using root tissue density only.

Community-weighted mean trait variables

CWM.RD: community-weighted mean of root diameter. Unit: mm.
CWM.SRL: community-weighted mean of specific root length. Unit: m g^-1.
CWM.SRA: community-weighted mean of specific root area. Unit: cm² g ^-1.
CWM.RTD: community-weighted mean of root tissue density. Unit: g cm ^-3.

File: TableS2_CWM_LMM.R

Description:
This R script reproduces the linear mixed-effects model analyses reported in Table S2.

The script tests the effects of drought treatment, site, and their interaction on community-weighted mean fine-root traits.

The response variables analyzed in this script are:

CWM.RD
CWM.SRA
CWM.SRL
CWM.RTD

The model structure is:

response ~ site * treat
random = ~1 | block

Models are fitted using restricted maximum likelihood (REML) with the lme function from the nlme package. Fixed effects are assessed using ANOVA.

Post hoc pairwise comparisons among drought treatments within each site are performed using estimated marginal means from the emmeans package.

File: TableS3_FDis_LMM.R

Description:
This R script reproduces the linear mixed-effects model analyses reported in Table S3.

The script tests the effects of drought treatment, site, and their interaction on functional dispersion estimated in multivariate trait space and separately for each fine-root trait.