DOI: 10.5061/dryad.sf7m0cgcb
title: Plant litter loss exacerbates drought influences on grasslands

description: Plant litter is known to affect soil, community, and ecosystem properties.
 However, we know little about the capacity of litter to modulate grassland
 responses to climate change. Using a 7-year litter removal experiment in a
 semiarid grassland, here we examined how litter removal interacts with
 consecutive droughts to affect soil environments, plant community
 composition, and ecosystem function. Litter loss exacerbates the negative
 impacts of drought on grasslands. Litter removal increased soil
 temperature but reduced soil moisture and nitrogen mineralization, which
 substantially increased the negative impacts of drought on primary
 productivity and the abundance of perennial rhizomatous graminoids.
 Moreover, complete litter removal shifted plant community composition from
 grass-dominated to forb-dominated, and reduced species and functional
 group asynchrony, resulting in lower ecosystem temporal stability. Our
 results suggest that ecological processes that lead to reduction in
 litter, such as burning, grazing, and haying, may render ecosystems more
 vulnerable and impair the capacity of grasslands to withstand drought
 events.
description: Study
 site and experimental treatments The field
 experiment was conducted in a semiarid steppe at the Inner Mongolia
 Grassland Ecosystem Research Station (116°42'E, 43°38'N, and
 1,250 m a.s.l.) of the Chinese Academy of Sciences, located in Inner
 Mongolia, northern China. This area has a semiarid temperate continental
 climate with mean annual precipitation (1982-2021) of 333.1 mm, of which
 60–80% falls from May to August. Mean winter precipitation that falls as
 snow is 27.8 mm (November to April), accounting for 8.3% of the total
 annual precipitation (1982–2021). The mean annual temperature is 1.0°C,
 with mean monthly temperatures ranging from -21.2°C in January to 19.7°C
 in July. The soil at the study site is dark chestnut with loamy sand
 texture. The plant community in the study area is dominated by perennial
 herbaceous plants, including <em>Leymus chinensis, Stipa grandis,
 Agropyron cristatum, Cleistogenes squarrosa, </em>and<em>
 Carex korshinskyi </em>(Bai et al., 2010). The plant
 litter removal experiment was conducted in a grassland enclosure that had
 been protected from grazing since 1999. A randomized complete block
 experiment was established in October 2014, including three plant litter
 removal treatments and six replicates for each treatment. Three 3 × 3 m
 plots were randomly laid out in each of six blocks (18 total plots) and
 then assigned to the 3 treatments: partial litter removal (-50%), complete
 litter removal (-100%), and no litter removal (control). Before the litter
 removal, there were no differences in plant community and soil properties
 among treatments. The litter removal treatments were applied annually at
 the end of October after plant natural senescence from 2014 to 2021. In
 each complete litter removal plot, all standing litter was removed by
 cutting with scissors and fallen plant litter was cleared by raking. In
 each partial litter removal plot, half of the standing and fallen litter
 were returned to the community in the first year and only the standing
 litter was manipulated in the following years.
 Soil
 moisture, temperature, and nitrogen mineralization
 Soil
 temperature was continuously measured every 60 min at a depth of 10 cm
 from November 2014 to September 2021.  Measurements were recorded
 automatically with a Datalogger (iButton DS1922L Wdsen Electronic
 Technology Co., Ltd).  Based on the daily average temperature data, we
 calculate the mean soil temperature in the growing season (ST) from May to
 September and in the non-growing season (NGST) from October to April of
 the following year.  Soil moisture was measured 3 times per month within
 the depth interval of 0–12 cm in each plot from June to August, using
 manual Time Domain Reflectometry (TDR) equipment (Soil Moisture Equipment
 Corp., Santa Barbara, CA, USA). Soil net N
 mineralization rate was measured using the in situ soil core incubation
 method from mid-July to mid-August each year from 2015 to 2021,
 corresponding to the peak growing season.  For each plot, 2 sharp-edged
 PVC tubes (5 cm in diameter and 12 cm in length) were inserted into the
 soil at 10 cm depth to extract soil cores.  One core was sealed by a
 parafilm membrane to prevent water penetration while allowing gas exchange
 and was then incubated in the field for about 28 days.  The other core was
 taken back to the laboratory and stored in a refrigerator at 4°C for
 measuring the initial inorganic N contents.  Soil inorganic N
 (NH<sub>4</sub><sup>+</sup>-N and
 NO<sub>3</sub><sup>-</sup>-N) was extracted with a
 2 mol/L KCl solution and subsequently measured using a continuous flow
 injection analyzer (AA3 HR, SEAL Analytical GmbH). 
 After
 harvesting the plant biomass, three soil cores (3 cm diameter, 0–10 cm
 depth) were randomly collected and mixed into one sample in each plot in
 mid-August 2021.  Soil total nitrogen (STN) was measured after soil
 samples were air-dried, ground, and passed through a 2 mm sieve.  STN was
 determined following Kjeldehl digestion by a Nitrogen Analyzer System
 (KJELTEC 2300 AUTO SYSTEM II, Foss Tecator AB, Sweden).  Roots and stones were removed prior to
 all soil sample processing. Plant species
 composition and biomass A permanent 1 × 1 m quadrat was randomly
 established in each of the 18 plots. The species abundance was determined
 by 1 × 1 m quadrat by individual counts, and the community abundance was
 quantified by the total number of plants in each quadrat. Species richness
 was measured by the number of species in mid-August at the peak of
 aboveground biomass of the plant community from 2015 to 2021. We randomly
 selected five individuals for each species present in the plot to measure
 plant height. If there were fewer than five individuals, all of them were
 measured. We then calculated the weighted average of plant height at the
 functional group level. Plant species were classified into 4 functional
 groups based on their life forms, including perennial bunchgrasses (PB),
 perennial rhizomatous graminoids (PR), perennial forbs (PF), and annual
 forbs (AF). The 4 groups consisted of 7, 2, 26, and 8 species,
 respectively. To estimate the biomass of the entire community and
 individual species, one 0.25 m × 1 m rectangular quadrat was randomly chosen within each plot in
 mid-August from 2015 to 2021, away from the 1 × 1m quadrats. All plants in
 each rectangular quadrats were clipped and sorted by species,
 and then weighed for biomass after drying at 65°C to a consistent weight
 for at least 48 hours. Aboveground primary productivity (ANPP) was
 estimated using the peak aboveground biomass of the plant
 community.
description: # Plant litter loss exacerbates drought influences on grasslands
 [https://doi.org/10.5061/dryad.sf7m0cgcb](https://doi.org/10.5061/dryad.sf7m0cgcb) This dataset includes pre-treatment plant community and soil properties, plant and soil responses to litter removal treatment from 2015 to 2021, changes in stability in terms of plant species and functionl group composition, species richness, asynchrony of species and functional group, and aboveground primary production (ANPP). ## Description of the data and file structure trt: -50%=50% litter removal -100%=100% litter removal Litter\_amount= Litter removal amount（g m<sup>-2</sup>) GST= Growing season soil temperature(ºC) NGST= Non-growing season soil temperature (ºC) SM= Soil moisture (v/v,%) SIN=Soil inorganic nitrogen (mg kg<sup>-1</sup>) Nmin= Net nitrogen mineralization rate (mg N kg<sup>-1</sup> d<sup>-1</sup>) LRR=Log response ratio LRR\_ANPP=Ln(ANPPdrought/ANPPpredrought)  Ln(ANPPpost-drought/ANPPpre-drought) Similirity=Community composition similarity to pre-drought Abundance\_PB= Abundance of perennial bunchgrass species (per m<sup>-2</sup>) Abundance\_PR= Abundance of perennial rhizomatous graminoids species (per m<sup>-2</sup>) Abundance\_PF= Abundance of perennial forb species (per m<sup>-2</sup>) Abundance\_AF= Abundance of annual forb species (per m<sup>-2</sup>) relative\_Abundance\_PB= Realative abundance of perennial bunchgrass species (%) relative\_Abundance\_PR= Relative abundance of perennial rhizomatous graminoids species (%) relative\_Abundance\_PF= Relative abundance of perennial forb species (%) relative\_Abundance\_AF= Relative abundance of annual forb species (%) ANPP\_PB=  ANPP of perennial bunchgrass species (g m<sup>-2</sup>) ANPP\_PR= ANPP of perennial rhizomatous graminoids species (g m<sup>-2</sup>) ANPP\_PF= ANPP of perennial forbs species (g m<sup>-2</sup>) ANPP\_AF= ANPP of annual forb species  (g m<sup>-2</sup>) Height\_PB=  Perennial bunchgrass species height (cm) Height\_PR= Perennial rhizomatous graminoids species height (cm) Height\_PF= Perennial forb species height (cm) Height\_AF= Annual forb species height (cm) Richness\_PB= Richness of perennial bunchgrass species (sp.m<sup>-2</sup>) Richness\_PR= Richness of perennial rhizomatous graminoids species (sp.m<sup>-2</sup>) Richness\_PF= Richness of perennial forb species (sp.m<sup>-2</sup>) Richness\_AF= Richness of annual forb species (sp.m<sup>-2</sup>) STN= Soil total nitrogen (g kg<sup>-1</sup>) SOC= Soil organic carbon (g kg<sup>-1</sup>) Asynchrony\_species= Species asynchrony Asynchrony\_FGs= Functional groups asychrony meanANPP= Average ANPP of community (g m<sup>-2</sup>) sdANPP= Standard deviation of ANPP Compositional\_stability= Community compositional stability Stability=Communtiy temporal biomass stability Stability\_PB= Perennial bunchgrass species stability Stability\_PR= Perennial rhizomatous graminoids species stability Stability\_PF= Perennial forb species stability Stability\_AF= Annual forb species stability Stability\_species= Species stability Stability\_FGs= Functional groups stability PCA= Principal component analysis Soil\_PCA1= PC1 of ST, NST, SM,Nmin and STN ## Sharing/Access information * The dataset are available at [https://doi.org/10.5061/dryad.sf7m0cgcb](https://doi.org/10.5061/dryad.sf7m0cgcb) ## Code/Software