DOI: 10.5061/dryad.pvmcvdnq7
title: Data for: Soil incubation data with intensified water variability

description: The dataset is from an incubation experiment which was carried out in the
 dark at the temperature of 15°C and the relative humidity of 40% for
 approximately three months. The predominant soil sampled from a temperate
 grassland of northern China, it is chernozem and belongs to sandy loam,
 with sand, silt and clay percentages of 54%, 41% and 5%, respectively. The
 SOC content of the 0-10 cm layer is 4.2% and the pH is 6.9. This study
 manipulated soil water levels and the intensity of water variability with
 a total of six treatments. There were four replicates for each treatment
 for gas sampling. The average cumulative CO2 release and the soil
 aggregate of the four replicates and its standard error (SE) are provided
 in the dataset. One additional group of destructive samplings and the
 soils for the gas sampling were collected at the wet end and dry end in
 the last drying-rewetting cycle, respectively. 14 phospholipid fatty acids
 (FLFA) markers were selected from the combination results of the wet and
 dry ends in the last drying-rewetting cycle.
description: The soil samples were collected from the 0-10 cm layer at four
 locations several meters apart in September 2020. Plants and surface
 litter were removed before sampling. The collected soil samples were
 transported to the laboratory in containers with ice. In the laboratory,
 the soil samples were passed through a 2 mm sieve, homogenized, and stored
 at -20℃ until the incubation experiment started. During the incubation,
 66.3 g fresh soil (equivalent to 50 g air-dried soil) was put in a 200 ml
 open-top mason jar. All the jars were pre-incubated at 60% of field water
 holding capacity for seven days. The soil water content was monitored
 daily by weighing the jars and adjusted by adding the corresponding amount
 of water if needed. During gas measurement, the jar was covered by a
 rubber lid with two gas paths and connected to an LI-8100A infrared gas
 analysis system (LI-COR, USA). The CO<sub>2</sub>
 concentration changes within 90 seconds in the headspace of each jar were
 recorded to calculate the CO<sub>2</sub> emission rate. The
 gas measurement was conducted daily in the first eight days, every two
 days for the next 19 days, and every 2-4 days thereafter.
 The soils for the gas measurements were destructively sampled at
 the end of the experiment. The experiment ended at their respective driest
 ends for intensified water variability treatments. One additional group of
 destructive samplings was collected at the wet end in the last
 drying-rewetting cycle to reveal whether there was a quick shift of
 microbial community between the dry and wet ends. Based on the microbial
 community and the total PLFA did not change within the last cycle, 14 FLFA
 markers were selected from the combination results of the wet and dry ends
 in the last drying-rewetting cycle. We chose PLFAs 15:0, 17:0, i15:0,
 a15:0, i16:0, i17:0, a17:0, cy17:0, 16:1ω7, 18:1ω7 to represent bacterial
 biomass, PLFAs 18:2ω6 and 18:1ω9 to indicate fungi biomass and PLFAs
 10Me16:0, 10Me18:0 to represent actinomycetes biomass. The water-stable
 aggregates composition was measured by Passing the soil samples through
 250 μm and 53μm sieves to get macro-aggregates (&gt;250 μm),
 micro-aggregates (53-250 μm) and mineral-associated SOC fraction
 (&lt;53 μm).