DOI: 10.5061/dryad.vx0k6djtv
title: Data from: Does pH matter for ecosystem multifunctionality? An empirical test in a semi-arid grassland on the Loess Plateau

description: Date of data collection: 2016-2018 Geographic location of data collection:
 Guyuan, Ningxia, China (106°23′E, 36°15′N) These data were generated to
 (i) investigate the responses of soil properties, biological communities
 and multifunctionality to decreased soil pH; (ii) determine the potential
 biotic and abiotic pathways that soil pH may drive multifunctionality. In
 2016, a 17 m × 40 m semi-arid grassland plot with an initial pH value of
 8.05 and uniform vegetation was selected. The experiment was granted by
 the administration of Yunwu Mountain National Nature Reserve. A randomized
 block design was used with five treatments and six replicates per
 treatment. A total of 30 plots were established. All plots were 2 m × 2 m
 and separated by 1 m buffer zones. The treatments included five levels of
 acid addition rate (0, 0.23, 0.56, 3.60, and 9.01 mol H+ m-2) in the form
 of sulphuric acid solution. In late August 2017, the plant communities
 achieved their peak biomass, and were surveyed and harvested in a 0.5 m ×
 1 m quadrat in each plot to determine the plant community diversity and
 estimate above-ground biomass. After harvesting the plants, six soil cores
 (0-15 cm deep, 2.5 cm diameter) per plot in each of the six blocks were
 collected and pooled by plot as a replicate for further chemical analyses.
description: 1. Plant community and primary productivity 
 Total numbers of species and individuals observed in each quadrat
 were measured as species richness and abundance, respectively. The species
 diversity of each plot was also characterized by Shannon Wiener's
 diversity index and Simpson’s diversity index. The species evenness was
 characterized by Pielou's evenness index. We measured soil
 respiration, root respiration, ecosystem respiration (ER) and net
 ecosystem C exchange (NEE) one time in mid-August 2017. Gross primary
 productivity (GPP) is the sum of NEE and ER. 2. Soil
 properties Soil pH was measured in a 1/2.5 ratio
 (soil/water) suspension. A rapid method of soil carbonate analysis using
 gas chromatography (GC-7890B, Agilent, Santa Clara, CA, USA) was used to
 measure soil carbonate. A 20 g subsample of the fresh soil was oven-dried
 at 105 °C for 24 h to determine soil moisture. Ammonium and nitrate
 concentrations in soil extracts were measured using a segmented ﬂow
 analyzer (Skalar SAN Plus; Skalar Inc., Breda, Netherlands). SOC was
 measured using the Walkley-Black method. Dissolved organic carbon (DOC) in
 extracts was determined with a TOC analyzer (Elementar Vario Micro Cube,
 Germany). Microbial biomass carbon (MBC) and nitrogen (MBN) were
 determined using the chloroform extraction methods, as conversion factors
 KC (0.38) and KN (0.45) for MBC and MBN, respectively. Available
 phosphorus concentrations in the extracts were measured by using the
 molybdate blue colorimetric method. The concentrations of the extractable
 cations were determined by an inductive coupled plasma emission
 spectrophotometer (Thermo 6300, Thermo Electron, Milford, MA,
 USA).  3. Potential extracellular enzymes
 activities Potential extracellular enzyme activities
 relating to C-cycling (α-1,4-glucosidase, β-1,4-glucosidase, β-cellobiose,
 β-1,4-xylosidase, phenol oxidase and peroxidase), N-cycling (leucine amino
 peptidase, β-1,4-N-acetyl-glucosaminidase) and P-cycling (alkaline
 phosphatase) were measured as decomposition and nutrient release functions
 of ecosystems. The activities of all extracellular enzymes, except for
 phenol oxidase and peroxidase, were quantiﬁed by high throughput
 ﬂuorometric assay in 96-well microtiter plates. The phenol oxidase and
 peroxidase activities were measured spectrophotometrically using
 l-3,4-dihydroxy phenylalanine (DOPA) as the substrate in clear 96-well
 microplates. The soils were assayed at a pH of 8.0 by suspending
 approximately 2.5 g of soil in 50 mL of 50 mM sodium acetate
 buffer.  4. Potential net N mineralization rates and
 potential nitrification rates  Potential net N
 mineralization rates were determined using the aerobic incubation
 procedure (Evans et al., 2001). Briefly, 12.5 g fresh soil was placed in a
 150 mL specimen bottle, which was then closed with a perforated plastic
 cap to allow gas exchange while minimizing evaporation. These samples were
 incubated for 30 days at 25 °C. Potential net N mineralization rates were
 calculated by the change in the concentrations of total inorganic N before
 and after the incubation.  Potential nitrification
 rates were measured by the chlorate inhibition method (Hoffmann et al.,
 2007). Brieﬂy, for each sample, two subsamples (2.5 g of fresh soil) were
 incubated in 50 mL centrifuge tubes containing 10 mL of ammonium sulfate
 solution (10 mM) and 50 μL of sodium chloride solution (1.5 M). One
 subsample was added with 2.5 mL of potassium chlorate (2 M) to inhibit
 nitrite oxidation before incubation, while the other one was not added
 until an incubation of 5 h in the dark in a shaker (175 rpm; 25 °C).
 Potential nitrification rates were calculated as the linear accumulation
 of nitrite concentration between time 0 and 5 h during the
 incubation.  Refences: Evans, R. D.,
 Rimer, R., Sperry, L., & Belnap, J. (2001). Exotic plant invasion
 alters nitrogen dynamics in an arid grassland. Ecological Applications,
 11(5), 1301–1310.
 https://doi.org/10.1890/1051-0761(2001)011[1301:EPIAND]2.0.CO;2
 Hoffmann, H., Schloter, M., & Wilke, B. M. (2007).
 Microscale-scale measurement of potential nitrification rates of soil
 aggregates. Biology and Fertility of Soils, 44(2), 411–413.
 https://doi.org/10.1007/s00374-007-0227-5