Short-term impact of fire-deposited charcoal on soil microbial community abundance and composition in a subtropical plantation in China

Geoderma 359 (2020) 113992

Contents lists available at ScienceDirect

Geoderma journal homepage: www.elsevier.com/locate/geoderma

Short-term impact of fire-deposited charcoal on soil microbial community abundance and composition in a subtropical plantation in China Yuzhe Wanga, Junqiang Zhengb, Xian Liua, Qiang Yanc, Yalin Hua,

T

⁎

a

Forestry College of Fujian Agriculture and Forestry University, Fuzhou 350002, China College of Life Sciences, Henan University, Kaifeng 475004, China c Xiqin Forest Station of Fujian Agriculture and Forestry University, Nanping 353000, China b

A R T I C LE I N FO

A B S T R A C T

Handling Editor: Naoise Nunan

Slash burning is a common and efficient way of removing forest harvest residues in subtropical plantations. However, few field studies have assessed the impact of fire-deposited charcoal on the diversity and composition of soil microbial communities. In this study, we manipulated the amount of charcoal left in plots after slash burning in a Pinus massoniana plantation of subtropical China. Soil samples were collected from 0 to 10 cm depth one year after charcoal application or removal. We investigated the diversity and composition of soil bacterial and fungal communities by high-throughput sequencing. The results showed that a taxon-specific shift in the relative abundances of bacteria and fungi at the genus level was observed after one year of fire-derived charcoal application, while soil bacterial and fungal diversity were not affected. Soil pH played a predominant role in determining the abundance of operational taxonomical units and diversity of soil bacteria, but not of the soil fungal community. In addition to soil pH, the amount of available phosphorus in soil played an important role in structuring soil microbial communities. Collectively, our findings highlight the importance of fire-deposited charcoal to soil bacterial and fungal communities in subtropical plantations subjected to slash burning.

Keywords: Slash burning Charcoal Bacterial community Fungal community Microbial diversity Field manipulation

1. Introduction Slash-and-burn is commonly used to clear harvest residues and improve forest health in subtropical plantations (Bonanomi et al., 2007; Anderson et al., 2011). Soil microbes play a key role in maintaining forest ecosystem functions such as carbon (C) and nutrient cycling, degradation of pollutants, and productivity (Carney and Matson, 2005; Peng et al., 2010; Zhao et al., 2015). However, little is known about how fire-deposited charcoal from slash-and-burn practices influences microbial processes in subtropical forest plantations. Fire can influence soil microbial communities directly through fire-induced mortality and indirectly through post fire-driven changes in soil physiochemical properties (Neary et al., 1999; Dooley and Treseder, 2012), e.g. variation in soil microclimate due to the input of combusted residues (i.e. fire-deposited charcoal) (Kolb et al., 2009; Ball et al., 2010). By altering the soil microclimate such as pH, water holding capacity, cation exchange capacity, bulk density, and soil structure (Liang et al., 2009; Qiu et al., 2008; Wang et al., 2016), char amendments have been shown to influence the diversity and composition of soil microbial communities in studies that used char materials (e.g. biochar) for soil amendment in agriculture (Anderson et al., 2011; Khodadad et al.,

⁎

2011; Chen et al., 2018) and studies used fire-derived char to investigate changes in soil properties following fire (Ball et al., 2010; Makoto et al., 2012). Furthermore, char materials provides C source and nutrients directly as well as indirectly to microorganisms as due to its high surface area, and it adsorbs nutrients from soil (i.e. root exudates, decomposing organic compounds and microbial byproducts) and make them available to microbes (Yu et al., 2006; Prendergast-Miller et al., 2011; Gul et al., 2015). The high porosity and large surface area of char provides habitat and refuge to microbes from soil predators (Pietkäinen et al., 2000; Quilliam et al., 2013). Alterations in the soil microbial community induced by char amendments vary with soil type and the feedstock of char materials (Khodadad et al., 2011). The response of soil microbial communities to char amendments is therefore likely to be different in subtropical and boreal forest ecosystems (Kim et al., 2007). Previous studies of the effects of char amendments on soil microbial community composition and diversity produced inconsistent results, varying with soil type, char type, soil conditions, and whether sites had previously experienced forest fires (Kim et al., 2007; Khodadad et al., 2011). For example, Khodadad et al. (2011) reported that there was a decrease in microbial number and diversity in unburned soils after the

Corresponding author. E-mail address: [email protected] (Y. Hu).

https://doi.org/10.1016/j.geoderma.2019.113992 Received 29 November 2018; Received in revised form 17 September 2019; Accepted 24 September 2019 0016-7061/ © 2019 Elsevier B.V. All rights reserved.

Geoderma 359 (2020) 113992

Y. Wang, et al.

2.2. Experimental design and soil sampling

addition of oak biochars produced at lower temperature (250 °C), while both unburned and soils experienced prescribed burns exhibited an increase in microbial number and diversity when treated with high temperature biochars (650 °C). Biochar made at higher temperatures generally have higher surface area and provide more favorable habitat for microorganisms (Zimmerman, 2010). However, the decrease of soil microbial diversity treated with low temperature oak biochar observed by Khodadad et al. (2011) was inconsistent with a previous study showing an 25% increase in microbial diversity in terra preta Anthrosols formed by “slash and char” practice in comparison to adjacent pristine forest soils (Kim et al., 2007). Moreover, previous studies showed char amendment could enhance the growth of specific taxa within the whole soil microbial community. Although increases in relative abundance of bacteria within the phyla Actinobacteria were generally observed in forest soils with natural or added char (Bääth et al., 1995; Khodadad et al., 2011), however, a decrease in the relative abundance of Acidobacteria was observed in a greenhouse study (Xu et al., 2014). The different responses of Actinobacteria abundance to char amendment might be due to the differences in biochar characteristics such as type, production temperature and adsorption ability (Kasozi et al., 2010). Most studies investigating char amendments have been conducted in laboratory conditions within closed systems, which may limit the transport of both char materials and soil microbes. Charcoal produced by slash burning is heterogeneously distributed on the soil surface, mixing into the soil over time (Ohlson et al., 2009; Makoto et al., 2012). To understand how the charcoal produced by slash burning influences the diversity and composition of soil microbial communities and whether bacterial and fungal communities respond differently to charcoal additions, we created plots with three different levels of charcoal (C0, in which all charcoal was removed after slash burning; C1, in which charcoal was left undisturbed after slash burning; and C2, in which charcoal removed from C0 sites was added to produce a double quantity of charcoal) in a Pinus massoniana plantation in Southern China. We hypothesized that: (1) the diversity of the soil microbial community would increase with the amount of charcoal input; and (2) charcoal addition would enrich specific taxa (e.g. bacteria from the phyla Gemmatimonadetes and Actinobacteria) involved in soil pyrogenic C metabolism. To our knowledge, this is the first study using molecular approach to investigate soil microbial responses to fire-deposited charcoal in subtropical pine plantations. The findings of this study will be of interest regarding soil quality of forests as influenced by charcoal deposition.

Broadcast burning of forest harvest residues was conducted within different blocks at the experimental site on March 7, 2016. Two weeks after burning, three levels of charcoal input were applied to the treatment areas by removing charcoal from some plots (10 × 10 m) and adding charcoal to other plots. The three charcoal treatments were arranged in a randomized complete block design with four replicates. The charcoal treatments were: C0, in which all visible charred materials were carefully removed from the plot; C1, in which all charred materials were left in place on the forest floor; and C2, in which all charred materials removed from the C0 plots were added to plots to double the quantities of charcoal deposits. Charcoal added to the C2 plots was spread on soil surface without mixing into the subsurface layers. Within each block, the unburnt area created for preventing the spread of fire to surrounding sites was used for the unburned control (UB). The basic chemical properties of charcoal are: pH, 7.98 ± 0.03; C content, 80.1 ± 0.30%; and N content, 0.32 ± 0.02%. In April 2016, all plots (including the unburned area) were planted with 1-year-old Phoebe bournei (Hemsl.) Yang seedlings in 2 m × 2 m spacing (2500 plants ha−1). Soil samples were collected on March 21, 2017, one year after charcoal application. After removing organic materials from the forest floor, eight soil samples were collected from each plot at 0–10 cm depth using a 3.8 cm-diameter auger. The eight samples collected from each plot were mixed to create a single composite sample per plot, sealed in polyethylene bags, and transported to the laboratory as soon as possible. After removal of visible stones and plant residues, soils were passed through a 2-mm sieve. Subsamples were air-dried for pH, total carbon (TC), total nitrogen (TN) and available phosphorus (P) analyses. Subsamples were stored at 4 °C for the analyses of moisture content, mineral N (NH4+-N and NO3−-N), dissolved organic C (DOC), total dissolved nitrogen (TDN), microbial biomass C (MBC) and N (MBN), and the analyses were finished within one week. Subsamples were frozen at −80 °C for molecular analysis by high-throughput sequencing. 2.3. Analysis of soil physicochemical properties Soil bulk density was determined using volumetric ring method (Pedrotti et al., 2005), and the following formula was used: soil bulk density = m/v, where m is weight of the soil inside the volumetric ring after drying at 105 °C for 24 h; v is volume of the ring (100 cm3). Soil moisture was determined gravimetrically by weighing soil samples before and after drying at 105 °C for 24 h. Soil pH was determined using a soil-to-water ratio of 1:2.5 (w/v) (Chen et al., 2018). Soil TC and TN were measured with a CN element analyzer (Vario MICRO cube, Elementar, Germany). The total P of soil samples was determined by digesting samples with concentrated HNO3 and analyzing them colorimetrically using the molybdate method (VIS-723 N, Rayleign, China). Soil available P was extracted with a 0.5 M NaHCO3 solution, colored with molybdenum-antimony solution, and measured using the spectrophotometry (VIS-723 N, Rayleign, China) (Olsen et al., 1954). DOC and TDN were extracted using 2 M KCl in a mix of 1:5 soil-to-water and then measured with a TOC-VCPH/CPN analyzer (Shimadzu Scientific Instruments, Japan). Soil mineral N (NH4+-N, NO3−-N) was extracted using 2 M KCl and measured with an Auto Discrete Analyzer (SmartChem200, AMS, Italy). DON was calculated by subtracting soil mineral N from TDN. Soil MBC and MBN were measured using the fumigation-extraction method. Soil samples were exposed to chloroform for 24 h followed by extraction with 0.5 M K2SO4 and C and N contents in the extracts were determined using a TOC-VCPH/CPN analyzer (Shimadzu Scientific Instruments, Japan). Soil MBC and MBN concentrations were calculated as the difference between fumigated and unfumigated extracts with conversion factors of 2.64 (Vance et al., 1987) and 2.22 (Brookes et al., 1985), respectively.

2. Materials and methods 2.1. Study site This study was conducted in the Xiqin Forest Station of Fujian Agriculture and Forestry University (26°33′ N, 118°6′ E), northwest Fujian Province, in southeast China. This region has a subtropical climate, with hot, humid summers between June and October, and short, mild winters in January and February. The mean annual rainfall is 1817 mm, mainly concentrated between May and July, and the average temperature is 19.4 °C. In October 2015, a P. massoniana plantation (2.8 ha, slope 25°) was clear-felled at the age of 33 years. This site has deep soil (> 1 m) classified as Ferric Acrisol according to the World Reference Base (WRB, 2015) soil classification system. The main understory plant species before burning were Ilex chinensis Sims, Pleioblastus amarus (Keng) Keng, Indocalamus tessellatus (Munro) Keng f., Callicarpa kochiana Makino, Ficus hirta Vahl, Litsea cubeba (Lour.) Pers., Miscanthus floridulus (Lab.) Warb. ex Schum. et Laut., and Dicranopteris linearis (Burm.) Underw.

2

Geoderma 359 (2020) 113992

Y. Wang, et al.

Table 1 Soil physiochemical properties as influenced by slash burning (C1), slash burning with charcoal removed (C0), slash burning with charcoal addition (C2) and no burning control (UB) one year after charcoal application in a subtropical pine plantation in Southern China. Different letters indicated significant differences among the treatments (P < 0.05). Properties −3

Bulk density (g cm ) Moisture (%) pH Total C (g kg−1) Total N (g kg−1) Total P (g kg−1) C:N C:P N:P DOC (mg kg−1) DON (mg kg−1) DOC:DON NH4+-N (mg kg−1) NO3−-N (mg kg−1) Available P (mg kg−1) MBC (mg kg−1) MBN (mg kg−1) MBC:MBN

UB

C0

C1

C2

1.12 ± 0.05 a 23.34 ± 1.60 a 4.24 ± 0.04 a 20.69 ± 1.50 a 1.58 ± 0.10 a 0.115 ± 0.003 a 13.07 ± 0.15b 178.91 ± 8.83 a 13.67 ± 0.54 a 155.00 ± 7.42 a 25.43 ± 3.92 a 6.45 ± 0.78 a 0.79 ± 0.22 ab 7.44 ± 1.47 a 1.99 ± 0.48 a 410.11 ± 52.44 a 78.64 ± 11.31 a 5.29 ± 0.26 ab

1.16 ± 0.04 a 18.45 ± 1.36 b 4.58 ± 0.13 a 18.81 ± 1.85 a 1.35 ± 0.15 a 0.112 ± 0.005 a 14.03 ± 0.27 ab 166.99 ± 9.59 a 11.95 ± 0.89 a 114.96 ± 8.54 a 23.79 ± 5.57 a 5.94 ± 1.69 a 1.90 ± 0.63 a 6.41 ± 0.84 a 4.40 ± 0.34 ab 300.55 ± 23.83 b 49.67 ± 2.80 b 6.07 ± 0.46 a

1.16 ± 0.07 a 20.97 ± 1.48 ab 4.69 ± 0.18 a 18.93 ± 3.64 a 1.38 ± 0.24 a 0.114 ± 0.015 a 13.58 ± 0.28 ab 162.08 ± 8.99 a 11.92 ± 0.47 a 115.38 ± 8.77 a 20.36 ± 3.46 a 6.09 ± 0.83 a 0.58 ± 0.28 b 4.52 ± 0.89 a 3.97 ± 0.36 ab 309.33 ± 26.07 b 61.79 ± 7.90 ab 5.11 ± 0.30 b

1.23 ± 0.03 a 21.83 ± 1.68 a 5.28 ± 0.66 a 24.65 ± 3.02 a 1.56 ± 0.09 a 0.108 ± 0.009 a 15.78 ± 1.41 a 243.08 ± 57.55 a 14.94 ± 2.13 a 140.66 ± 36.07 a 27.60 ± 6.07 a 5.09 ± 0.59 a 1.48 ± 0.58 ab 5.15 ± 1.23 a 5.86 ± 1.58 b 307.17 ± 46.13 b 63.68 ± 7.00 ab 4.77 ± 0.19 b

diversity, we rarified the OTU table and calculated three metrics: Chao1, an estimate of the species abundance; Observed Species, an estimate of the amount of unique OTUs found in each sample; Shannon diversity index (H) and Simpson diversity index (D) were calculated according to the equations H = −∑(Pi)(log2Pi) and D = 1 − ∑(Pi)2, respectively, where Pi is the proportion of the community represented by OTUi (Simpson, 1949; Shannon and Weaver, 1963). All raw sequence data have been deposited in the NCBI Sequence Read Archive under accession numbers PRJEB28207 and PRJEB28178.

2.4. Soil DNA extraction, amplification and purification DNA was extracted from 0.3 g of soil (wet weight) using the MoBio PowersoilTM DNA isolation kit (Carlsbad, CA, USA) according to the manufacturer’s protocols, with the final elution step using deionized water instead of TE buffer. The concentration of DNA was measured using a DeNovix DS-11 spectrophotometer (DeNovix, Wilmington, DE, USA). The bacteria-specific primers 341F and 806R were used to amplify the V3-V4 region of the bacterial 16S rRNA gene, while the eukaryotespecific primers ITS5-1737F and ITS2-2043R were used to amplify the ITS1 region of the fungal internal transcribed spacer. To distinguish between samples, the reverse primers were tagged with unique barcodes. All PCR reactions were carried out in 30 µL reactions with 15 µL of Phusion® High-Fidelity PCR Master Mix (New England Biolabs, UK), 0.2 µM each of forward and reverse primers, and 10 ng of template DNA. Thermal cycling consisted of an initial denaturation step at 98 °C for 1 min, followed by 30 cycles of denaturation at 98 °C for 10 s, annealing at 50 °C for 30 s, and elongation at 72 °C for 30 s, and a final extension step at 72 °C for 5 min. Following PCR amplification, equal volume of PCR products and 1× loading buffer (containing SYBR green) were mixed and detected by electrophoresis in a 2% (w/v) agarose gel. The obtained products were mixed in equal density ratios and purified using a QIAquick PCR Purification Kit (QIAGEN, Germany). Sequencing libraries were generated using TruSeq® DNA PCR-Free Sample Preparation Kit (Illumina) according to the manufacturer’s recommendations. Library quality was assessed on the Qubit® 2.0 Fluorometer (Invitrogen, Carlsbad, CA, USA). Finally, libraries were sequenced on the Illumina Hiseq2500 platform at Novogene Bioinformatics Technology Co., Ltd. (Beijing, China).

2.6. Statistical analysis Normality and homogeneity of variance were checked prior to statistical analysis. The effect of charcoal application on soil physiochemical properties, number of OTUs, diversity indices, and the relative abundances of bacteria and fungi at the phylum and genus level were tested using a univariate general linear model with block as the random factor, and post-hoc comparisons were made using the least significant difference test at a significant level of 0.05. Canonical correspondence analysis (CCA) was conducted to elucidate the relationship between soil microbial community characteristics and soil physiochemical properties among the charcoal treatments. Path analysis was performed to test the contribution of soil physiochemical properties and nutrient quality to variations in the number of soil bacterial OTUs and microbial community diversity. The variables to be included in the path diagram were determined by multiple stepwise regression analysis of relationship between soil properties (physiochemical properties and nutrients content) and soil microbial community characteristics (OTUs and diversity). The coefficients of each path, taken as the calculated standardized coefficients, were determined by analyzing the correlation matrices of soil physiochemical properties and nutrients data. A univariate general linear model and path analysis were conducted using IBM SPSS Statistics (version 22.0) and CCA was performed in R v.3.5.0 software with the vegan package (R Development Core Team 2018).

2.5. High-throughput sequencing data analysis The raw paired-end reads were assembled after filtering adaptors, low quality reads, ambiguous nucleotides, and barcodes to generate clean joined reads for each sample. Split sequences for individual samples were merged using FLASH V1.2.7 (Magoä and Salzberg, 2011), and low-quality sequences were discarded using QIIME V1.7.0 (Caporaso et al., 2010). Sequences analyses were performed using Uparse software (Uparse v7.0.1001, http://drive5.com/uparse/; Edgar, 2013). Sequences with ≥97% similarity were assigned to the same operational taxonomical units (OTUs). A representative sequence for each OTU was screened for further annotation. To compute alpha

3. Results 3.1. Soil physiochemical properties The moisture contents of C2 and UB soils were significantly higher than that of C0 soil (P < 0.05; Table 1). Soil bulk density was unaltered by the application of charcoal (P > 0.05; Table 1). Soil pH remained constant regardless of the level of charcoal (P > 0.05). The 3

Geoderma 359 (2020) 113992

Y. Wang, et al.

Table 2 Operational taxonomical units (OTUs) numbers and Alpha diversity indexes of soil bacterial and fungal communities as influenced by slash burning (C1), slash burning with charcoal removed (C0), slash burning with charcoal addition (C2) and no burning control (UB) in a subtropical pine plantation in Southern China. Values are the means ± standard errors (n = 4). Different letters indicated significant differences among the treatments (P < 0.05). Index

UB

C0

C1

C2

Bacteria

OTUs Observed species Shannon index Simpson index Chao1

1461 ± 50 b 1264 ± 40 b 7.529 ± 0.038 b 0.986 ± 0.001 b 1456.16 ± 58.32 a

1837 ± 101 a 1654 ± 127 ab 8.070 ± 0.141 ab 0.990 ± 0.001 ab 2309.28 ± 578.61 a

1953 ± 144 a 1723 ± 139 a 8.192 ± 0.170 a 0.990 ± 0.001 ab 1910.73 ± 144.19 a

1980 ± 168 a 1766 ± 166 a 8.391 ± 0.312 a 0.991 ± 0.002 a 1940.41 ± 163.66 a

Fungi

OTUs Observed species Shannon index Simpson index Chao1

874 ± 75 a 607 ± 40 ab 4.70 ± 0.32 a 0.86 ± 0.04 a 851.74 ± 72.31 ab

741 ± 126 a 493 ± 54 b 4.65 ± 0.13 a 0.89 ± 0.01 a 656.37 ± 94.52 b

1036 ± 79 a 692 ± 61 a 5.23 ± 0.41 a 0.89 ± 0.04 a 969.12 ± 84.77 a

948 ± 79 a 639 ± 61 ab 5.01 ± 0.58 a 0.89 ± 0.05 a 889.78 ± 64.32 ab

NH4+-N content was higher in C0 soil than in C1 soil (P < 0.05). The available P content was significantly higher in C2 soil than in UB soil (Table 1). No significant differences were observed in soil bulk density, TC, TN, TP, C:P, N:P, NO3−-N, DOC, DON, or DOC:DON among any of the treatments. 3.2. Structure and diversity of soil microbial communities The number of bacterial OTUs was significantly higher in burnt soils (C0, C1, and C2) than in UB soil (P < 0.05; Table 2). The number of observed species and the Shannon index were significantly higher in the C1 and C2 treatments than in UB soil (P < 0.05; Table 2). The Simpson index of C2 soil was significantly higher than that of UB soil (P < 0.05; Table 2). The number of bacterial OTUs, number of observed species, and Shannon index were not altered by the quantity of charcoal in burned plots (P > 0.05; Table 2). There were no significant differences in the chao1 index among the treatments (P > 0.05; Table 2). In terms of the soil fungal community, the number of observed species and the chao1 index were significantly lower in C0 soil than in C1 soil (P < 0.05), while charcoal addition (C2) had no significant effect on these variables (P > 0.05; Table 2). No significant differences were observed in the number of fungal OTUs, Shannon index, or Simpson index among the various charcoal treatments (P > 0.05; Table 2).

Fig. 1. Relative abundance of bacterial phyla in soils as influenced by slash burning (C1), slash burning with charcoal removed (C0), slash burning with charcoal addition (C2) and no burning control (UB) in a subtropical pine plantation in Southern China. Different letters indicated significant differences among the treatments (P < 0.05).

significantly lower in C2 soil than in UB soil (P < 0.05, Fig. 3a). The relative abundance of the other four fungal phyla were not significantly different among the various charcoal treatments (P > 0.05). At the genus level, the relative abundance of Bartalinia was significantly higher in C2 soil than in UB, C0 or C1 soil (P < 0.05; Fig. 3b). Soil in the C0 treatment had significantly lower relative abundances of sequences belonging to Cordana and Metarhizium than UB soil (P < 0.05) and significantly lower relative abundance of Pestalotiopsis than C1 soil (Fig. 3b).

3.3. Abundance and composition of soil microbial communities The MBC content of UB soil was significantly higher than those of C0, C1 and C2) (P < 0.05), and the MBN content of UB soil was significantly higher than that of C0 soil (P < 0.05; Table 1). The ratio of soil MBC:MBN was significantly higher in the C0 treatment than in C1 and C2 treatments (P < 0.05; Table 1). Across all the treatments, the most abundant bacterial phyla were Proteobacteria, Acidobacteria, Actinobacteria, and Chloroflexi, which accounted for more than 90% of the total relative abundance of the soil bacterial community (Fig. 1). The relative abundances of Proteobacteria, Acidobacteria, Actinobacteria, Chloroflexi, Gemmatimonadetes, Bacteriodetes, Cyanobacteria and Thaumarchaeota did not vary with charcoal treatments (P > 0.05). The relative abundance of Gemmatimonadetes was significantly higher in C1 soil than in UB soil (P < 0.05). At the genus level, the relative abundance of Candidatus koribacter was significantly higher in C2 soil than in C0 soil (P < 0.05; Fig. 2a), while the opposite was true for one unidentified genus belonging to phylum Acidimicrobiales (Fig. 2a). Charcoal removal also significantly decreased the relative abundance of one unidentified genus belong to phylum Acidobacteria compared to C1 soil (P < 0.05; Fig. 2a). Basidiomycota, Ascomycota, Zygomycota, Glomeromycota and Chytridiomycota were the most abundant fungal phyla in the soil fungal community, accounting for more than 99% of the total fungal sequences (Fig. 3a). The relative abundance of Chytridiomycota was

3.4. Relationships between soil physiochemical properties and microbial responses According to CCA eigenvalues, axes 1 and 2 accounted for 47.4% and 18.3% of the overall variance in soil bacterial communities (Fig. 4a) and 26.9% and 22.2% of the overall variance in soil fungal communities, respectively (Fig. 4b). Soil pH, available P and TC accounted for the greatest proportion of the variance in soil bacterial taxa among the charcoal treatments. Similarly, soil pH, available P and MBC content accounted for the greatest proportion of the variance in the soil fungal community. There was a positive relationship between soil pH, C:N ratio, and available P, and a negative relationship between soil total P, NO3−-N and diversity indices of soil bacterial communities (Table S1). The only significant negative relationship observed in our analysis of soil fungal communities was that between soil MBN and the Simpson index (Table S2). Through calculating the relative contributions of soil pH and nutrient contents and ratios to OTU abundance and 4

Geoderma 359 (2020) 113992

Y. Wang, et al.

Fig. 2. Relative abundances of abundant bacterial genera in soils exposed to slash burning (C1), slash burning with charcoal removed (C0), slash burning with charcoal addition (C2) and no burning control (UB) in a subtropical pine plantation in Southern China. Different letters indicated significant differences among the treatments (P < 0.05).

Fig. 3. Relative abundances of abundant fungal phyla (a) and genera (b) in soils exposed to slash burning (C1), slash burning with charcoal removed (C0), slash burning with charcoal addition (C2) and no burning control (UB) in a subtropical pine plantation in Southern China. Different letters indicated significant differences among the treatments (P < 0.05).

diversity of soil microbial communities, we found that soil pH played a predominant role in determining out abundance (Fig. 5a) and diversity (Fig. 5b) in the soil bacterial community, but not in the fungal community. The results of a path analysis of the soil fungal community were not significant (P > 0.05), so we have not presented the model here.

higher than that of C0 soil one year after charcoal application, while soil bulk density and pH were unaltered by any amount of charcoal application. The increase in soil moisture in response to charcoal addition might be ascribed to the retention effects that charcoal possesses due to its porosity and large surface area (Zackrisson et al., 1996). Contrary to some previous studies, we did not observe any significant increase in soil pH with charcoal addition in our study (Major et al., 2009; Anderson et al., 2011). DeLuca et al. (2006) also found that soil pH was not affected by the addition of field-collected charcoal in western Montana. It is possible that the charcoal-induced pH increase sometimes observed in forest soils driven by the ash that is deposited along with charcoal (Bélanger et al., 2004). In our study, we removed and replaced charred materials while ashes were left on site and soil samples were collected 1 year after charcoal application. More time may be required to induce a significant shift in soil pH and other soil properties. The long-term influence of charcoal applications on soil physiochemical properties should be measured in future studies. Previous studies have demonstrated that charcoal amendment has the potential to increase soil N availability in forest ecosystems (Steiner et al., 2008; Ball et al., 2010). However, we did not find any increase in soil NH4+-N or NO3−-N contents after charcoal addition, and in fact found that soil NH4+-N content significantly increased with charcoal removal. The increase may be attributable to decreased soil nitrification after charcoal removal, since charcoal has the capacity to adsorb organic compounds (e.g. phenolic compounds and monoterpenes) that inhibit nitrification (White, 1994; DeLuca et al., 2006). The lack of

4. Discussion Charcoal is a recalcitrant byproduct of forest fires that is known to alter soil biotic activity both directly and indirectly (Glaser et al., 2002; Makoto et al., 2012; Hart and Luckai, 2013). In this study, we found that charcoal application altered the abundance of bacteria and fungi at the genus level, while bacterial and fungal diversity was unaltered. Soil bacterial and fungal diversity differed in their responses to soil pH. Moreover, soil pH and available P were the key drivers determining soil microbial community structure in subtropical plantations subjected to slash burning. 4.1. Soil physiochemical properties and nutrients content Soil physiochemical properties, such as moisture, pH, bulk density and organic C, are generally improved by biochar and charcoal amendments (Glaser et al., 2002). However, the responses of specific physiochemical properties differ between lab incubations and field experiments, as well as short-term and long-term field studies. In this study, we found that the moisture content of C2 soils was significantly 5

Geoderma 359 (2020) 113992

Y. Wang, et al.

Fig. 4. Canonical correlation analysis (CCA) of the relationships between soil physiochemical properties and bacterial (a) and fungal (b) communities exposed to slash burning (C1), slash burning with charcoal removed (C0), slash burning with charcoal addition (C2) and no burning control (UB) in a subtropical pine plantation in Southern China.

Fig. 5. Path diagrams representing the final model showing the contributions of soil properties to soil bacterial operational taxonomical units (OTUs) (a) and diversity (b) in a subtropical pine plantation in Southern China.

response of NO3−-N content to charcoal applications might be due to the high mobility of NO3−-N, which may increase loss through leaching, especially in subtropical China with a mean annual rainfall of ca. 1800 mm. The effects of charcoal input on soil N retention/loss in subtropical plantations need to be investigated in combination with plant N uptake, soil N dynamics, N-associated enzyme activity and functional gene expression in future studies. In this study, soil available P content in charcoal-added soils was significantly higher than that of unburnt soils 1 year after charcoal application, highlighting the ability of charcoal to enhance soil P availability in the short term (Table 1). Previous studies have shown that biochar has the potential to improve soil P availability (Gao et al., 2016; Pingree et al., 2017; Gao and DeLuca, 2018), a phenomenon that could be controlled by abiotic or biotic mechanisms. Abiotic processes include shifts in redox potentials, direct surface adsorption and desorption of P, and the development of organo-mineral complexes around biochar particles (DeLuca et al., 2015; Joseph et al., 2015; Zhang et al., 2016). During the development of organo-mineral complexes, the formation rate of macroaggregates was increased and an additional surface to which phosphatase enzymes could adsorb was created, which might result in an increase in the pool of bioavailable P (Swaine et al., 2013; Weng et al., 2017). Moreover, soil P solubility could also be modified by the adsorption of chelating organic molecules via ligand exchange and surface binding during the formation of organo-mineral complexes (Gao and Deluca, 2018). The potential biotic mechanism is

derived from biochar-induced alterations in the size and activity of soil microorganisms that mediate solubility or mineralization of soil P (He et al., 2014). Phosphorus is known to be a limiting factor in many ecosystems, especially in subtropical forests in Southern China (Huang et al., 2013). The short-term positive effects of charcoal produced by slash-and-burn practices on soil P availability could benefit soil fertility and productivity in subtropical plantations in China. Future studies combining investigations of soil P dynamics, soil biochemical analysis, P-associated enzyme activity and functional gene expression might help elucidate the underlying mechanisms responsible for charcoal-induced changes in soil P availability in subtropical plantations subjected to slash burning. 4.2. Diversity and structure of soil bacterial and fungal communities The diversity of soil bacterial and fungal communities as indicated by the Shannon and Simpson indices were not significantly different among different charcoal treatments (Table 2). Bacterial diversity has also been observed to remain unaffected by the addition of biochar in an acid rice paddy (Zheng et al., 2016) and in dry cropland in China (Chen et al., 2018). However, other studies have found that charcoal amendments impact the diversity of soil microbial communities, and both increases (Kolton et al., 2017) and decreases in microbial diversity have been reported (Khodadad et al., 2011). In the present study, we observed no significant impact of charcoal application on soil microbial 6

Geoderma 359 (2020) 113992

Y. Wang, et al.

diversity. The differences between our findings and the results of laboratory incubation experiments may be due to differences in procedure. In incubation experiments, charcoal was generally thoroughly mixed with soil, while in this study we applied charcoal only to the soil surface. The vertical movement of charcoal in natural systems is slow (Brodowski et al., 2006; Major et al., 2009), and more time may be required for charcoal to enter organic soil in the field and induce significant effects on soil microbial diversity. Kim et al. (2007) found that soil bacterial diversity of terra preta in the western Amazon was significantly higher than that of adjacent pristine forest soil. The terra preta Anthrosols were formed by “slash and char” agriculture (Mann 2002). This is evidence that fire-deposited charcoal may cause significant changes in soil microbial diversity over a longer time scale than that encompassed by the observations in this study. Moreover, bacterial diversity was significantly higher in charcoal-deposited soils than unburned soils, while there was no difference in fungal diversity between unburned and charcoal-deposited soils, indicating that soil bacterial communities could respond to the addition of fire-deposited charcoal in the short term (e.g. one year in the current study). However, long-term observations are needed to follow the changes in soil fungal diversity in response to the input of fire-deposited charcoal. We found that soil bacterial and fungal diversity differed in their responses to soil pH. Soil bacterial diversity was positively correlated with soil pH, while soil pH did not affect the diversity of fungi. This is consistent with the results of Rousk et al. (2010), who found that soil pH had a strong influence on the diversity of soil bacterial communities across a pH gradient ranging from 4.0 to 8.3, whereas the correlation between fungal diversity and pH was far weaker. The different responses of bacterial and fungal communities to soil pH might be due to the different pH ranges necessary for the optimal growth of each type of organism Soil bacteria experience optimal growth within a relatively narrow pH range, which varies between 3 and 4 pH units in pure culture (Rosso et al., 1995). By contrast, fungal species generally have a wider optimal pH, capable of relatively unimpeded growth in a range of 5–9 units (Wheeler et al., 1991; Nevarez et al., 2009). Although there was no significant difference in soil pH among charcoal treatments due to high variability, soil pH generally increased with the amount of charcoal input, indicating that fire-deposited charcoal input may have more influence on the diversity of soil bacteria than soil fungi. Previous studies have shown that soil pH and nutrient quality indicators such as C:N ratio and extractable organic C and N are important factors determining soil microbial community structure in terrestrial ecosystems (Fierer and Jackson, 2006; Rousk et al., 2010; Zhou et al., 2017). In this study, soil C:N ratio was found to be a less effective measure than pH in predicting soil microbial community structure; a similar result was reported by Högberg et al. (2007). The increase of the soil C:N ratio in our study was due to the artificial addition of charcoal, which was unavailable to microorganisms in the short term. We also found that soil available P, rather than soil C:N ratio, was a key factor strongly influencing soil bacterial and fungal communities. Phosphorus is one of the most limiting nutrients in subtropical and tropical forests in southern China (Cleveland et al., 2011; Huang et al., 2013). We found that soil available P content was enhanced by burning and charcoal deposited by fires which is consistent with previous studies (Makoto et al., 2012; Pingree et al., 2017). Charcoal additions appeared to preferentially stimulate microorganisms with a specific life strategy for P use, especially soil bacteria (Gao and DeLuca, 2018). It seems that soil P was a key determinant of soil microbial community structure after slash burning in the studied plantations, and the responses of specific taxa to different soil P fractions and the underlying mechanisms of these responses need to be examined in future studies.

(Fig. 1). Charcoal had no effect on the relative abundance of bacteria at the phylum level. This is somewhat consistent with the findings of Xu et al. (2014), who found that biochar treatments did not affect the relative abundance of Proteobacteria and Actinobacteria. Previous studies showed that the impact of charcoal amendments on the relative abundance of specific taxa varied with soil and biochar type (Khodadad et al., 2011; Xu et al., 2014). Khodadad et al. (2011) found that biochar amendments enriched the relative abundance of Actinobacteria in unburned soils, but not in soils that experienced annual prescribed burns. In a greenhouse study, Xu et al. (2014) found that Acidobacteria was the most sensitive phylum to biochar made from rice straw, with its relative abundance decreasing from 17.8% to 6.1% in an acidic soil planted with rape. The relative abundance of Chloroflexi also significantly decreased with the addition of biochar, which is inconsistent with the results of this study. The impact of charcoal on soil microbial composition apparently differ in natural systems and laboratory incubation studies; more field studies are needed in the future to determine the true impact of charcoal in forest plantations. As they did with soil bacterial communities, charcoal applications changed the relative abundance of soil fungi at the genus level, but not at the phylum level. The addition of charcoal induced an increase in the relative abundance of the fungi genus Bartalinia over that in C0 soil (P < 0.05). Both addition and removal of charcoal decreased the relative abundance of the genus Pestalotiopsis, although this decrease was only significant in the C0 treatment (Fig. 3b). Pestalotiopsis is a complex genus including more than 225 species, most of which are phytopathogenic causing leaf spots, fruit rot, needle and grey blights on a variety of hosts (Keith et al., 2006; Espinoza et al., 2008; Sudhakara Reddy et al., 2016). Our findings indicate that post-fire charcoal management could influence the abundance of fungal plant pathogens in addition to bacterial plant pathogens (Anderson et al., 2011). Therefore, future research should monitor the symptoms of plant disease in afforested Phoebe bournei plantations. 5. Conclusions The short-term impacts of fire-deposited charcoal on the diversity and composition of two major soil microbial taxa, bacteria and fungi, were investigated in a subtropical pine plantation in China subjected to slash burning. One year after application, charcoal induced a taxonspecific shift in the relative abundance of bacteria and fungi at the genus level, but not at the phylum level. Soil bacterial and fungal diversity was unaltered by the application of charcoal in the short term. Soil pH played a predominant role in determining OTU abundance and diversity of soil bacterial communities, but not those of soil fungal communities. Our results also suggest that soil available P content, which is influenced by fire and charcoal, in turn influences the microbial community structure. Overall, our field study highlighted the role of fire-deposited charcoal in shaping soil microbial communities in subtropical plantations subjected to slash burning. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements The authors would like to thank Prof. Thomas H. DeLuca and Dr. Adam Polinko for providing insightful comments on this manuscript. We thank Zhe Wang, Long Lin, Peng Wu and Jundi Liu for their help with field and laboratory work. This work was financially supported by the Department of Education, Fujian Province (JAT170189) and the National Natural Science Foundation of China (Nos. 31700378, 41603081).

4.3. Composition of soil bacterial and fungal communities Proteobacteria, Actinobacteria, Actinobacteria and Chloroflexi were the most abundant soil bacterial phyla in all four soil treatments 7

Geoderma 359 (2020) 113992

Y. Wang, et al.

References

Technol. 44, 6189–6195. Keith, L.M., Velasquez, M.E., Zee, F.T., 2006. Identification and characterization of Pestalotiopsis spp. causing scab disease of guava, Psidium guajava, in Hawaii. Plant Dis. 90, 16–23. Khodadad, C.L.M., Zimmerman, A.R., Green, S.J., Uthandi, S., Foster, J.S., 2011. Taxaspecific changes in soil microbial community composition induced by pyrogenic carbon amendments. Soil Biol. Biochem. 43, 385–392. Kim, J.S., Sparovek, G., Longo, R.M., De Melo, W.J., Crowley, D., 2007. Bacterial diversity of terra preta and pristine forest soil from the Western Amazon. Soil Biol. Biochem. 39, 684–690. Kolb, S.E., Fermanich, K.J., Dornbush, M.E., 2009. Effect of charcoal quantity on microbial biomass and activity in temperate soils. Soil Sci. Soc. Am. J. 73, 1173–1181. Kolton, M., Graber, E.R., Tsehansky, L., Elad, Y., Cytryn, E., 2017. Biochar-stimulated plant performance is strongly linked to microbial diversity and metabolic potential in the rhizosphere. New Phytol. 213, 1393–1404. Liang, B., Lehmann, J., Sohi, S.P., Thies, J.E., O’Neill, B., Trujillo, L., Gaunt, J., Solomon, D., Grossman, J., Neves, E.G., Luizão, F.J., 2009. Black carbon affects the cycling of non-black carbon in soil. Org Geochem. 41, 206–213. Magoä, T., Salzberg, S.L., 2011. FLASH: fast length adjustment of short reads to improve genome assemblies. Bioinformatics 27, 2957–2963. Major, J., Lehmann, J., Rondon, M.A., Goodale, C.L., 2009. Fate of soil-applied black carbon: downward migration, leaching and soil respiration. Glob. Change Biol. 16, 1366–1379. Makoto, K., Shibata, H., Kim, Y.S., Satomura, T., Takagi, K., Nomura, M., Satoh, F., Koike, T., 2012. Contribution of charcoal to short-term nutrient dynamics after surface fire in the humus layer of a dwarf bamboo-dominated forest. Biol. Fertil. Soils 48, 569–577. Mann, C.C., 2002. The real dirt on rain forest fertility. Science 297, 920–923. Neary, D.G., Klopatek, C.C., DeBano, L.F., Ffolliott, P.F., 1999. Fire effects on belowground sustainability: a review and synthesis. For. Ecol. Manage. 122, 51–71. Nevarez, L., Vasseur, V., Le Madec, L., Le Bras, L., Coroller, L., Leguérinel, I., Barbier, G., 2009. Physiological traits of Penicillium glabrum strain LCP 08.5568, a filamentous fungus isolated from bottled aromatised mineral water. Int. J. Food Microbiol. 130, 166–171. Ohlson, M., Dahlberg, B., Okland, T., Brown, K.J., Halvorsen, R., 2009. The charcoal carbon pool in boreal forest soils. Nat. Geosci. 2, 692–695. Pedrotti, A., Pauletto, E.A., Crestana, S., Holanda, F.S.R., Cruvinel, P.E., Vaz, C.M.P., 2005. Evaluation of bulk density of Albaqualf soil under different tillage systems using the volumetric ring and computadorized tomography methods. Soil Tillage Res. 80, 115–123. Peng, J.J., Cai, C., Qiao, M., Li, H., Zhu, Y.G., 2010. Dynamic changes in functional gene copy numbers and microbial communities during degradation of pyrene in soils. Environ. Pollut. 158, 2872–2879. Pietkäinen, J., Kiikkilä, O., Fritze, H., 2000. Charcoal as a habitat for microbes and its effect on the microbial community of the underlying humus. Oikos 89, 231–242. Pingree, M.R.A., Makoto, K., DeLuca, T.H., 2017. Interactive effects of charcoal and earthworm activity increase bioavailable phosphorus in sub-boreal forest soils. Biol. Fertil. Soils 53, 873–884. Prendergast-Miller, M.T., Duvall, M., Sohi, S.P., 2011. Localisation of nitrate in the rhizosphere of biochar-amended soils. Soil Biol. Biochem. 43, 2243–2246. Qiu, Y., Cheng, H., Xu, C., Sheng, G.D., 2008. Surface characteristics of crop-residuederived black carbon and lead (II) adsorption. Water Res. 42, 567–574. Olsen, S.R., Cole, C.V., Watanabe, F.S., 1954. Estimation of Available Phosphorus in Soils by Extraction with Sodium Bicarbonate. USDA Circular No. 939, US Government Printing Office, Washington DC. Quilliam, R.S., Glanville, H.C., Wade, S.C., Jones, D.L., 2013. Life in the ‘charosphere’ – does biochar in agricultural soil provide a significant habitat for microorganisms? Soil Biol. Biochem. 65, 287–293. Rosso, L., Lobry, J.R., Bajard, S., Flandrois, J.P., 1995. Convenient model to describe the combined effects of temperature and pH on microbial growth. Appl. Environ. Microbiol. 61, 610–616. Rousk, J., Bååth, E., Brookes, P.C., Lauber, C.L., Lozupone, C., Caporaso, J.G., Knight, R., Fierer, N., 2010. Soil bacterial and fungal communities across a pH gradient in an arable soil. ISME J. 4, 1340–1351. Shannon, C.E., Weaver, W., 1963. The Mathematical Theory of Communication. University of Illinois Press, Champaign, Ill, USA. Simpson, E.H., 1949. Measurement of diversity. Nature 163, 688. Steiner, C., Glaser, B., Teixeira, W.G., Lehmann, J., Blum, W.E.H., Zech, W., 2008. Nitrogen retention and plant uptake on a highly weathered central Amazonian Ferralsol amended with compost and charcoal. J. Plant Nutr. Soil Sci. 171, 893–899. Sudhakara Reddy, M., Murali, T.S., Suryanarayanan, T.S., Govinda Rajulu, M.B., Thirunavukkarasu, N., 2016. Pestalotiopsis species occur as generalist endophytes in trees of Western Ghats forests of southern India. Fungal Ecol. 24, 70–75. Swaine, M., Obrike, R., Clark, J.M., Shaw, L.J., 2013. Biochar alteration of the sorption of substrates and products in soil enzyme assays. Appl. Environ. Soil Sci. 2013, 1–5. Vance, E.D., Brookes, P.C., Jenkinson, D.S., 1987. An extraction method for measuring soil microbial biomass C. Soil Biol. Biochem. 19, 703–707. Wang, Y.Z., Zhang, L.W., Yang, H., Yan, G.J., Xu, Z.H., Chen, C.R., Zhang, D.K., 2016. Biochar nutrient availability rather than its water holding capacity governs the growth of both C3 and C4 plants. J. Soils Sediments 16, 801–810. Weng, Z., Van Zwieten, L., Singh, B.P., Tavakkoli, E., Joseph, S., Macdonald, L.M., Rose, T.J., Rose, M.T., Kimber, S.W.L., Morris, S., Cozzolino, D., Araujo, J.R., Archanjo, B.S., Cowie, A., 2017. Biochar built soil carbon over a decade by stabilizing rhizodeposits. Nat. Clim. Change 7, 371–376. Wheeler, K.A., Hurdman, B.F., Pitt, J.I., 1991. Influence of pH on the growth of some toxigenic species of Aspergillus, Penicillium and Fusarium. Int. J. Food Microbiol. 12,

Anderson, C.R., Condron, L.M., Clough, T.J., Fiers, M., Stewart, A., Hill, R.A., Sherlock, R.R., 2011. Biochar induced soil microbial community change: implications for biogeochemical cycling of carbon, nitrogen and phosphorus. Pedobiologia 54, 309–320. Ball, P.N., MacKenzie, M.D., DeLuca, T.H., Montana, W.E.H., 2010. Wildfire and charcoal enhance nitrification and ammonium-oxidizing bacterial abundance in dry montane forest soils. J. Environ. Q. 39, 1243–1253. Bääth, E., Frostegärd, A., Pennanen, T., Fritze, H., 1995. Microbial community structure and pH response in relation to soil organic matter quality in wood-ash fertilized, clear-cut or burned coniferous forest soils. Soil Biol. Biochem. 27, 229–240. Bélanger, N.I., Côté, B., Fyles, J.W., Chourchesne, F., Hendershot, W.H., 2004. Forest regrowth as the controlling factor of soil nutrient availability 75 years after fire in a deciduous forest of southern Quebec. Plant Soil 262, 363–372. Bonanomi, G., Antignani, V., Pane, C., Scala, E., 2007. Suppression of soilborne fungal diseases with organic amendments. J. Plant Pathol. 89, 311–324. Brodowski, S., John, B., Flessa, H., Amelung, W., 2006. Aggregate-occluded black carbon in soil. Eur. J. Soil Sci. 57, 539–546. Brookes, P., Landman, A., Pruden, G., Jenkinson, D., 1985. Chloroform fumigation and the release of soil nitrogen: a rapid direct extraction method to measure microbial biomass nitrogen in soil. Soil Biol. Biochem. 17, 837–842. Caporaso, J.G., Kuczynski, J., Stombaugh, J., Bittinger, K., Bushman, F.D., Costello, E.K., Fierer, N., Peña, A.G., Goodrich, J.K., Gordon, J.I., Huttley, G.A., Kelley, S.T., Knights, D., Koenig, J.E., Ley, R.E., Lozupone, C.A., McDonald, D., Muegge, B.D., Pirrung, M., Reeder, J., Sevinsky, J.R., Turnbaugh, P.J., Walters, W.A., Widmann, J., Yatsunenko, T., Zaneveld, J., Knight, R., 2010. QIIME allows analysis of highthroughput community sequencing data. Nat. Methods 7, 335–336. Carney, K.M., Matson, P.A., 2005. Plant communities, soil microorganisms, and soil carbon cycling: does altering the world belowground matter to ecosystem functioning? Ecosystems 8, 928–940. Chen, J.H., Sun, X., Zheng, J.F., Zhang, X.H., Liu, X.Y., Bian, R.J., Li, L.Q., Cheng, K., Zheng, J.W., Pan, G.X., 2018. Biochar amendment changes temperature sensitivity of soil respiration and composition of microbial communities 3 years after incorporation in an organic carbon-poor dry cropland soil. Biol. Fertil. Soils 54, 175–188. Cleveland, C.C., Townsend, A.R., Taylor, P., Alvarez-Clare, S., Bustamante, M.M., Chuyong, G., Dobrowski, S.Z., Grierson, P., Harms, K.E., Houlton, B.Z., Marklein, A., Parton, W., Porder, S., Reed, S.C., Sierra, C.A., Silver, W.L., Tanner, E.V., Wieder, W.R., 2011. Relationships among net primary productivity, nutrients and climate in tropical rain forest: a pan-tropical analysis. Ecol. Lett. 14, 939–947. DeLuca, T.H., MacKenzie, M.D., Gundale, M.J., Holben, W.E., 2006. Wildfire-produced charcoal directly influences nitrogen cycling in ponderosa pine forests. Soil Sci. Soc. Am. J. 70, 448–453. DeLuca, T.H., Gundale, M.J., MacKenzie, M.D., Jones, D.L., 2015. Biochar effects on soil nutrient transformations. In: Lehmann, J., Joseph, S. (Eds.), Biochar for Environmental Management: Science, Technology and Implementation. Routledge, London, pp. 421–454. Dooley, S.R., Treseder, K.K., 2012. The effect of fire on microbial biomass: a meta-analysis of field studies. Biogeochemistry 109, 49–61. Edgar, R.C., 2013. UPARSE: highly accurate OTU sequences from microbial amplicon reads. Nat. Methods 10, 996–998. Espinoza, J.G., Briceño, E.X., Keith, L.M., Latorre, B.A., 2008. Canker and twig dieback of blueberry caused by Pestalotiopsis spp. and a Truncatella sp. in Chile. Plant Dis. 92, 1407–1414. Fierer, N., Jackson, R.B., 2006. The diversity and biogeography of soil bacterial communities. PNAS 103, 626–631. Gao, S., DeLuca, T.H., 2018. Wood biochar impacts soil phosphorus dynamics and microbial communities in organically-managed croplands. Soil Biol. Biochem. 126, 144–150. Gao, S., Hoffman-Krull, K., Bidwell, A.L., DeLuca, T.H., 2016. Locally produced wood biochar increases nutrient retention and availability in agricultural soils of the San Juan Islands, USA. Agric. Ecosyst. Environ. 233, 43–54. Glaser, B., Lehmann, J., Zech, W., 2002. Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal-a review. Biol. Fertil. Soils 35, 219–230. Gul, S., Whalen, J.K., Thomas, B.W., Sachdeva, V., Deng, H., 2015. Physico-chemical properties and microbial responses in biochar-amended soils: mechanisms and future directions. Agric. Ecosyst. Environ. 206, 46–59. Hart, S., Luckai, N., 2013. Charcoal function and management in boreal ecosystems. J. Appl. Ecol. 50, 1197–1206. He, H., Qian, T.T., Liu, W.J., Jiang, H., Yu, H.Q., 2014. Biological and chemical phosphorus solubilization from pyrolytical biochar in aqueous solution. Chemosphere 113, 175–181. Högberg, M.N., Högberg, P., Myrold, D.D., 2007. Is microbial community composition in boreal forest soils determined by pH, C-to-N ratio, the trees, or all three? Oecologia 150, 590–601. Huang, W.J., Liu, J.X., Wang, Y.P., Zhou, G.Y., Han, T.F., Li, Y., 2013. Increasing phosphorus limitation along three successional forests in southern China. Plant Soil 364, 181–191. Joseph, S., Husson, O., Graber, E., van Zwieten, L., Taherymoosavi, S., Thomas, T., Nielsen, S., Ye, J., Pan, G., Chia, C., Munroe, P., Allen, J., Lin, Y., Fan, X., Donne, S., 2015. The electrochemical properties of biochars and how they affect soil redox properties and processes. Agronomy 5, 322–340. Kasozi, G.N., Zimmerman, A.R., Nkedi-Kizza, P., Gao, B., 2010. Catechol and humic acid sorption onto a range of laboratory-produced black carbons (biochars). Environ. Sci.

8

Geoderma 359 (2020) 113992

Y. Wang, et al.

Zheng, J., Chen, J., Pan, G., Liu, X., Zhang, X., Li, L., Bian, R., Cheng, K., Zheng, J., 2016. Biochar decreased microbial metabolic quotient and shifted community composition four years after a single incorporation in a slightly acid rice paddy from southwest China. Sci. Total Environ. 571, 206–217. Zhao, C.C., Fu, S.L., Mathew, R.P., Lawrence, K.S., Feng, Y.C., 2015. Soil microbial community structure and activity in a 100-year-old fertilization and crop rotation experiment. J. Plant Ecol. 8, 623–632. Zhou, X.Q., Guo, Z.Y., Chen, C.R., Jia, Z.J., 2017. Soil microbial community structure and diversity are largely influenced by soil pH and nutrient quality in 78-year-old tree plantations. Biogeosciences 14, 2101–2111. Zimmerman, A.R., 2010. Abiotic and microbial oxidation of laboratory-produced black carbon (biochar). Environ. Sci. Technol. 44, 1295–1301.

141–150. White, C.S., 1994. Monoterpenes: their effects on ecosystem nutrient cycling. J. Chem. Ecol. 20, 1381–1406. Xu, H.J., Wang, X.H., Li, H., Yao, H.Y., Su, J.Q., Zhu, Y.G., 2014. Biochar impacts soil microbial community composition and nitrogen cycling in an acidic soil planted with rape. Environ. Sci. Technol. 48, 9391–9399. Yu, X.Y., Ying, G.G., Kookana, R.S., 2006. Sorption and desorption behaviours of diuron in soils amended with charcoal. J. Agric. Food. Chem. 54, 8545–8550. Zackrisson, O., Nilsson, M.C., Wardle, D.A., 1996. Key ecological function of charcoal from wildfire in the Boreal forest. Oikos 77, 10–19. Zhang, H.Z., Chen, C.R., Gray, E.M., Boyd, S.E., Yang, H., Zhang, D.K., 2016. Roles of biochar in improving phosphorus availability in soils: a phosphate adsorbent and a source of available phosphorus. Geoderma 276, 1–6.

9