DOI: 10.5061/dryad.bg79cnpmq
title: Data from: Labile carbon input alleviates nitrogen-induced community instability in a meadow steppe

description: Global nitrogen (N) deposition continues to threaten plant diversity and
 ecosystem stability despite a recent slowdown in its increasing rates.
 Labile carbon (C) may help reduce excess N by alleviating microbial C
 starvations, but their role in mitigating the harmful effects of N
 enrichment remains unclear. In a meadow steppe in northern China, we
 conducted a 9-year (2014-2022) field experiment with six levels of
 historical N addition (0, 2, 5, 10, 20, and 50 g N m–2 yr–1, 2014-2019)
 and three levels of labile C (0, 200, and 2000 g C m-2 yr-1). Three years
 after ceasing N treatments (2020-2022), aboveground net primary
 productivity (ANPP) remained high under N addition. However, species
 richness and community stability continued to decline with increasing N
 addition rates. Labile C addition reduced the dominance of certain plant
 species within the community while it enhanced species asynchrony and
 belowground net primary productivity (BNPP). Boosted regression tree
 models indicated that the high levels of labile C inputs improved
 community stability by enhancing BNPP, which increased the relative
 importance of BNPP to the community stability from 7.5% to 27.4% as labile
 C input rose. Synthesis. Our results highlight how labile C inputs can
 counteract the negative impacts of N enrichment on community stability via
 enhancing plant-microbe competition and increasing belowground biomass
 allocation.
description: Aboveground biomass was collected annually in mid-August (2020 to
 2022) by clipping all vascular plants within a 1 × 1 m quadrat from a 2 ×
 2 m subplot. Biomass was sorted by species, separated from litter and dead
 standing biomass, and then weighed after being oven-dried at 70 °C for at
 least 48 h to estimate ANPP. Species richness was calculated as the total
 number of species per quadrat. Belowground net primary
 productivity (BNPP) was measured using the root ingrowth core method (Wang
 et al., 2019a; Yang et al., 2022). At the end of the growing season in
 mid-September 2019, a single core (7 cm in diameter and 50 cm deep) was
 vertically drilled into the soil in each subplot. The soil was sieved to 2
 mm to remove roots, debris, and rocks. A polyester mesh bag (mesh size 2
 mm) was placed over a PVC tube (7 cm in diameter and 50 cm length) and
 inserted into the holes. The PVC tube was then slowly pulled out while the
 hole was filled with root-free sieved soil, which was compressed to match
 the original soil density. In mid-September from 2020
 to 2022, mesh bags were carefully pulled out from the holes, and the soil
 was sieved (mesh size 2 mm) to collect roots from each year. The screened
 soil was then returned to the polyester mesh bag and reinserted into the
 original hole. All root samples were washed, dried at 70 °C for 48 h, and
 weighed. BNPP was calculated based on the average root biomass from the
 ingrowth core in each subplot over the years 2020 to 2022.
 During the growth period from 2020 to 2022, the leaves of
 <em>L. chinensis</em> were collected from all subplots, and
 the total N concentration of leaf samples was determined using an element
 analyzer (vario El III, Elementar Analysensysteme GmbH, Hanau, Germany)
 after grinding with a ball mill. Following the biomass
 harvests in mid-August each year from 2020 to 2022, soil samples were
 collected using a soil auger (3 cm in diameter). The five-point method was
 employed to collect soil samples from the 0-10 cm depth, which were then
 combined to obtain a single homogenized composite sample per subplot.
 These samples were passed through a 2-mm sieve to remove visible plant
 roots before analyzing soil parameters, including soil pH, microbial
 biomass C (MBC), microbial biomass nitrogen (MBN), soil ammonium
 (NH<sub>4</sub><sup>+</sup>-N) and nitrate
 (NO<sub>3</sub><sup>−</sup>-N) concentrations. MBC
 and MBN were extracted using a 0.5 M
 K<sub>2</sub>SO<sub>4</sub> solution following the
 chloroform fumigation extraction method (Lovell<em> </em>et
 al., 1995), and analyzed using an elemental analyzer (Liqui TOC,
 Analysensysteme, Germany). Soil
 NH<sub>4</sub><sup>+</sup>-N and
 NO<sub>3</sub><sup>−</sup>-N concentrations were
 extracted with a 2 M KCl solution and quantified using a continuous flow
 injection analyzer (FIAStar, Foss Tecator, Sweden).
description: # Data from: Labile carbon input alleviates nitrogen-induced community
 instability in a meadow steppe
 [https://doi.org/10.5061/dryad.bg79cnpmq](https://doi.org/10.5061/dryad.bg79cnpmq) ## Description of the data and file structure The zip file contains three files. The "Plant and Soil Data" and "Water Addition Treatment" files contain data collected over three years (2020-2022), with eight replicates per year. The "Leaf Nitrogen Concentration" file contains data collected over three years (2020-2022), with five replicates per year. **Description:**  ###### *Variables* * Plot: Nitrogen treatment plot. A Plot refers to a specific experimental unit where treatments are applied. * Block: Study block. A block refers to a randomized grouping of experimental plots designed to control for variability in environmental conditions. * Labile C addition:  Carbon (C) addition treatment. Carbon addition treatment includes Control (CK), Low labile carbon addition (Low C), High labile carbon addition (High C), and Water addition (Water) treatments. * Historical N addition:  Historical nitrogen (N) addition treatment. Historical N addition includes six different N addition rates: 0, 2, 5, 10, 20, and 50 g N m² yr⁻¹. * Richness: Species richness. Richness refers to the total number of species present within a given subplot. * ANPP:  Aboveground net primary productivity. The unit for ANPP (Aboveground Net Primary Productivity) is g m⁻² yr⁻¹ (grams per square meter per year). * Temporal stability: The temporal stability of the community * Asynchrony: Species asynchrony * Dominance ratio index: The species dominance ratio index * BNPP: Belowground net primary productivity. The unit for BNPP (Belowground Net Primary Productivity) is g m⁻² yr⁻¹ (grams per square meter per year). * NO3: Soil nitrate concentrations. The unit for NO₃⁻-N (Soil nitrate concentrations) is mg N kg⁻¹ soil (milligrams of nitrogen per kilogram of soil).  * NH4: Soil ammonium concentrations. The unit for NH₄⁺-N (Soil ammonium concentrations) is mg N kg⁻¹ soil (milligrams of nitrogen per kilogram of soil).  * MBC: Soil microbial biomass carbon. The unit for MBC (Soil microbial biomass carbon) is mg C kg⁻¹ soil (milligrams of carbon per kilogram of soil).  * MBN: Soil microbial biomass nitrogen. The unit for MBN (Soil microbial biomass nitrogen) is mg N kg⁻¹ soil (milligrams of nitrogen per kilogram of soil). * Leaf N concentration: Leaf nitrogen concentration of Leymus chinensis. The Leaf N concentration of Leymus chinensis is g N kg⁻¹ (grams of nitrogen per kilogram of dry leaf).