DOI: 10.5061/dryad.t4b8gtj8d
title: Data for: Male, female and mixed-sex poplar plantations support divergent soil microbial communities

description: Mixed-species forests are often more productive than monocultures because
 of a lower niche overlap and higher taxonomic and functional diversity of
 soil microbial communities. Males and females of dioecious plants have
 sex-specific adaptations to diverse habitats. The potential of using
 sexual differences in establishing more diverse poplar plantations has not
 been explored in degraded areas. We conducted a series of greenhouse and
 field experiments to investigate how belowground competition, soil
 microbial communities and seasonal variation nitrogen content differ among
 female, male and mixed-sex Populus cathayana plantations. In the
 greenhouse experiment, female neighbors suppressed the growth of males
 under optimal nitrogen conditions. However, male neighbors enhanced δ15N
 of females under inter-sexual competition. In the field, the root length
 density, root area density and biomass of fine roots were lower in female
 plantations than in male or mixed-sex plantations. Bacterial networks of
 female, male and mixed-sex plantations were characterized by different
 composition of hub nodes, including connectors, module and network hubs.
 The sex composition of plantations altered bacterial and fungal community
 structures according to Bray-Curtis distances, with 44% and 65% of
 variance explained by the root biomass, respectively. The total soil
 nitrogen content of mixed-sex plantation was higher than that in female
 plantation in spring and summer. The mixed-sex plantation also had a
 higher β-1,4-N-acetyl-glucosaminidase activity in summer and a higher
 nitrification rate in autumn than the other two plantations. The seasonal
 soil N content, nitrification rate and root distribution traits
 demonstrated spatiotemporal niche separation in the mixed-sex plantation.
 We argue that a strong female-female competition and limited nitrogen
 content could strongly impede plant growth and reduce the resistance of
 monosex plantations to climate change and the mixed-sex plantations
 constitutes a promising way to restore degraded land.
description: The four experiments as following: Experiment
 1. Plant-plant competition under different N levels To
 investigate the effects of the sex identity on the growth of neighboring
 plants, one-year-old cuttings were sampled from male and female
 plantations and then cultivated in pots in a naturally-lit greenhouse at
 the Hangzhou Normal University (30°17′N, 120°0′E). Thereafter, cultivated
 plants of a similar size were randomly chosen and transplanted in plastic
 pots (diameter 36 cm, height 27 cm). Each pot was filled with sand,
 vermiculite, and perlite (1:1:1). Each pot contained two rooted cuttings,
 either male-male, female-female, or male-female. Half of the plants were
 subject to an optimal N treatment (control) and half of the plants to a
 limited N treatment (N-). Each treatment had five replicates. The N levels
 were controlled with the Long Ashton solution (supplementary material for
 detailed information of the Long Ashton solution). After growing for 14
 weeks, the plants were harvested, separated between biomass fractions and
 dried at 75 °C for 72 h, after which the dry mass of each fraction was
 measured. The root N content was measured by semimicro Kjeldahl method (Wu
 et al. 2021). The dried leaf samples (n = 3) were used to determine
 natural δ13C and δ15N with an isotope ratio mass spectrometer (DELTA V
 Advantage, Thermo Fisher Scientific, Inc., USA). The Pee Dee Belemnite and
 N2 were used as standards to calculate δ13C and δ15N,
 respectively. <em>Experiment 2. Variation in root
 features along soil vertical profile in different
 plantations</em> The root architecture and
 distribution along the soil profile was explored among the three
 plantation types. Twenty 10 m × 8 m plots were set up in the male and
 female plantations, and 17 plots in the mixed-sex plantation. A soil core
 sampler (diameter 70 mm) was used to sample soil and roots at soil depths
 of 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, 40-50 cm and 50-60 cm. The soil
 cores were sampled at a distance of 1 m from each plant. All soil samples
 were immediately put in plastic bags and taken to the lab. Roots in each
 sample were carefully separated from soil and washed by deionized water.
 Coarse roots (diameter ≥ 2 mm) of each sample were separated and dried at
 75 °C for 72 h to measure their biomass. Fine roots (diameter &lt; 2
 mm) were immediately scanned, and the Win-Rhizo system (Régent instrument
 Inc., Québec, Canada) was used to measure the total fine root length.
 After scanning, fine roots of each sample were separated into two
 fractions based on the diameter 1-2 mm or &lt;1 mm. Both root
 fractions were dried at 75 °C for 72 h and their dry mass was estimated.
 Nitrogen contents of coarse and fine roots were measured by semimicro
 Kjeldahl method (Wu et al. 2021). <em>Experiment
 3. Seasonal dynamics in phospholipid fatty acids (PLFAs) and N
 cycle</em> This experiment aimed to explore
 seasonal dynamics in the microbial biomass, extracellular enzyme
 activities and net nitrification rate among the three plantations.
 Sampling was conducted in April, July and October, 2021 from the female,
 male and mixed plantations. As the Experiment 2 demonstrated that the bulk
 of the root biomass was located in 0-10 and 10-20 cm soil layers (Fig. 1),
 the samples were taken from these soil layers. From each stand, ten
 replicate samples were collection. The soil microbial
 biomass was assessed by PLFA analyses according to Schindlbacher et al.
 (2011). All measurements included a blank sample with the internal
 standard (peak 19:0, nonadecanoic fatty acid). The PLFA biomarkers
 including iso-, anteiso-(i13:0, i14:0, i15:0, a15:0, i16:0, i17:0 and
 a17:0) and 10Me-(10Me17:0 and 10Me18:0) branched PLFAs were attributed to
 Gram-positive bacteria (G+ bacteria) (Luo et al. 2022); monounsaturated
 and cyclopropyl PLFAs including 17:1ω8c, 18:1ω5c, 18:1ω7c, cy17:0 and
 cy19:0 were attributed to Gram-negative bacteria (G– bacteria) (Luo et al.
 2022); and 16:1ω5c, 18:1ω9c and 18:3ω6c were used for fungi (Joergensen
 2022; Willers et al. 2015). The PLFAs including 14:0, 16:0, 17:0, 18:0 and
 20:0 were used as non-specific markers present in all microorganisms
 (Joergensen 2022). The sum of all selected PLFAs was used to characterize
 the total microbial biomass. The sum of G+ and G− bacterial PLFAs was used
 to characterize the bacterial biomass. The G+ : G– ratio and fungal :
 bacterial (F:B) ratio were separately calculated as the ratio of G+ PLFAs
 to G– PLFAs and the ratio of fungal PLFAs to bacterial PLFAs. The
 activities of three hydrolytic enzymes, including β-1,4-glucosidase (BG),
 β-1,4-N-acetyl-glucosaminidase (NAG), and acid phosphatase,  were measured
 following the methods in Jing et al. (2020). The net nitrification rate
 was assessed by quantifying changes in NO3- concentration before and after
 a 10-day aerobic incubation (Durán et al. 2014). Soil-water suspension
 (1:2.5 w/v) was used for pH determination.
 <em>Experiment 4. Microbiota assembly in different sex
 plantations</em> In the beginning of August,
 2020, soil samples were taken from the depths 0-20 cm, 20-40 cm and 40-60
 cm to explore their chemical and microbial traits of different soil
 layers. Five plots (25 m × 15 m) were established in each plantation. In
 each plot, three soil samples were collected at each soil depth and pooled
 to form a composite sample. Five soil samples at each depth were also
 collected in the degraded area without any artificial management
 practices. A total of 45 samples were collected. After sampling, the soil
 samples were kept on ice before transportation to the laboratory, where a
 part was kept at -80 °C until DNA extraction and a part was air-dried for
 chemical analyses, including contents of soil organic matter (SOM), total
 nitrogen (TN), total phosphorus (TP) and available phosphorus (AP)
 contents. The remaining part of soil was kept at 4 °C to measure the
 contents of NH4+, NO3-, dissolved organic carbon (DOC), dissolved organic
 nitrogen (DON), microbial carbon biomass (MBC) and microbial nitrogen
 biomass (MBN). SOM was determined by the potassium dichromate external
 heating method. Soil AP was determined by the molybdenum-antimony
 colorimetric method after extraction with sodium bicarbonate (Guo et al.
 2021). TN was measured by the Kjeldahl method and TP by Ultraviolet
 spectrophotometer. Fresh soil (10 g) was extracted with 2 M KCl, and the
 extractions were used to determine NH4+ and NO3- contents. The contents of
 DOC and DON were estimated according to Luo et al. (2022). MBC and MBN
 were determined by the chloroform fumigation extraction method (Vance et
 al. 1987).
description: # Data for: Male, female and mixed-sex poplar plantations support
 divergent soil microbial communities
 ## Description of the data
 and file structure The files contain primary data including Experiment 1,
 2, 3 and 4, including C and N isotope, soil traits, root biomass, root N
 content, PLFA, nitrification rate, enzymes. Data in sheet 1: Leaf δ13C and
 δ15N affected by plant-plant competition under different N availabilities,
 optimal (control) vs. limited. The NHF, NHM, NMM, NFF in the sheet1
 indicated female in inter-sexual competition, male in inter-sexual
 competition, M in intra-sexual competition, and female in intra-sexual
 competition under control treatment. The HF, HM, MM, FF in the sheet1
 indicated female in inter-sexual competition, male in inter-sexual
 competition, M in intra-sexual competition, and female in intra-sexual
 competition under nitrogen-limited treatment. Data in sheet 2: SOM, soil
 organic matter; TN, total nitrogen; TP, total phosphorus; AP, available
 phosphorus; DOC, dissolved organic carbon; DON, dissolved organic
 nitrogen; MBC, microbial carbon biomass; MBN, microbial nitrogen biomass.
 Data in sheet 3: Indicated biomass of fine and coarse root. F: female. M:
 male. FM: mixed-sex. Data in sheet 4: The seasonal dynamics in
 extracellular enzyme activities. BG: β-1,4-glucosidase (nmol·g dry
 weight-1· h-1). NAG: β-1,4-N-acetyl-glucosaminidase (nmol· g dry weight-1·
 h-1). AP: acid phosphatase (nmol ·g dry weight-1 ·h-1). Data in sheet 5:
 Seasonal dynamics in net nitrification rate in female, male and mixed-sex
 plantations. NR: net nitrification rate Data in sheet 6: Seasonal soil pH
 data Data in sheet 7: N content of fine and coarse root Data in sheet 8:
 Seasonal soil N content data Data in sheet 9: PLFA (phospholipid fatty
 acids)