Soil microbial biomass carbon (C) and nitrogen (N) (MBC and MBN) reflect microbial size and soil fertility status, and they act as the living nutrient pool in soil . As the experiment proceeded, the soil microbial community in Calcaric Cambisol adapted to the experimental environment, and the low nutrient content in Calcaric Cambisol may encourage the microbes to assimilate exogenous C resources from the added organic materials [13, 65]; hence, significantly higher microbial functional diversity indices were found in Calcaric Cambisol at the end of the 12th month when compared with those in the 1st month. Writing – review & editing, Roles At the end of the 12th month, the variance in MBC and MBN was primarily explained by the organic material type, and the contribution of the organic material type was significant and explained 45.3% of the variance in MBC and 29.5% of the variance in MBN (P < 0.05, Table 3). Ling Li. Data curation, . [Article in Chinese] Li D(1), Wu Z, Chen L, Zhu P, Ren J, Liang C, Peng C, Gao H. Author information: (1)Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China. The chemical characteristics of these organic materials were shown in Table 2. https://doi.org/10.1371/journal.pone.0203812.t002. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. To better compare the effects of exogenous organic materials and soil type on the microbial characteristics and to eliminate the effect of climate factors, Calcaric Cambisol and Luvic Phaeozem were moved to the subtropical region to accentuate the effects of global warming and soil acidification. Soil properties that affect microbial biomass are clay, soil pH, and organic C (figure 3). At two time points (at the end of the 1st and 12th months), soil microbial biomass carbon (C) and nitrogen (N) (MBC and MBN) and Biolog Ecoplate substrate use patterns were determined, and the average well color development and the microbial functional diversity indices (Shannon, Simpson and McIntosh indices) were calculated. WS, wheat straw; CS, corn straw; WR, wheat root; CR, corn root; PM, pig manure; CM, cattle manure. Aliquots of 150 μl of the 10−3 suspension was incubated in each well of Biolog Eco plates at 28°C and the absorbance was measured at 590 nm with an Emax precision microplate reader (Biolog, Hayward, CA, USA). Total fiber content of organic material (cellulose, hemicellulose and lignin), total organic C, and total organic N were determined. Yes The quality of applied organic materials can regulate microbial abundance and function [2–4]. National Engineering Laboratory for Improving Quality of Arable Land, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, China, Roles https://doi.org/10.1371/journal.pone.0203812.g004. Meanwhile, the low pH in the Ferralic Cambisol (pH = 5.2) would reduce the utilization of labile substrate by soil microbes [56–57] because of the toxic exchangeable Al in low pH soil ; however, the integrated effect of SOC, clay content and organic materials amendment could affect the response of microbial biomass to pH as shown by the non-significance of pH in explaining microbial biomass in the stepwise multiple regression analysis. The management and environmental factors controlling microbial biomass and community structure were identified in a three-year field experiment. No, Is the Subject Area "Maize" applicable to this article? Soil microbial communities play an important role in supplying essential nutrients to plants by decomposing various organic matters. At the end of the 1st month, soil clay content significantly influenced AWCD and U, pH significantly influenced D, and total nitrogen significantly influenced H’ (P < 0.05). The high precipitation in the study site would leach the soluble acid ions into the litter bags, thus limiting organic matter availability and inhibiting microbial metabolism (Fig 1) [63–64]. ODR is affected by several factors. e0203812. Total fiber content of organic material (cellulose, hemicellulose and lignin) was determined by the method described by van Soest . Microbial CLPPs in soil were determined by Biolog Eco plates (Biolog, Hayward, CA, USA). Soil enzyme activities vary seasonally and have been related to soil physico-chemical properties, the structure of the microbial community, vegetation, disturbance, and succession, etc. Soil properties, e.g., organic C and clay content were the predominant influence on microbial functional diversity in particular at the end of the 12th month (61.8–82.8% of the variance explained). The differences among treatments with separation of means by Tukey’s HSD (α = 0.05) test at P < 0.05. Soil microbial biomass is a critical factor in ecosystem nutrient cycling [ 16, 17, 18 ], and knowledge about its relation with the ecological stoichiometry of soil is crucial for us to gain insight into the nutrient cycling of terrestrial ecosystems [ 19, 20, 21, 22 ]. The present study was not all consistent with the previous reports, although the Shannon index in Ferralic Cambisol and Luvic Phaeozem with lower initial pH (Table 1) was lower than that in Calcaric Cambisol at the end of the 1st month (Fig 3C). https://doi.org/10.1371/journal.pone.0203812.t005. Conversely, the N limitation was more serious in crop material treatments with high C/N ratio than in manure treatments (S1 Fig) ; the immobilized N induced by crop materials can be recycled in microorganisms with crop materials decomposition [47, 52]. Soil total K and available K were determined using atomic absorption spectrophotometry. The C/N ratio and N content of organic materials significantly affected the MBC and MBN at the end of the 1st and 12th months (P < 0.05), and soil clay significantly affected MBC at the end of the 1st month (P < 0.05, Table 5). As a result, AWCD and McIntosh index were low in Calcaric Cambisol because of its high initial pH (Table 1) at the end of the 1st month. No, Is the Subject Area "Shannon index" applicable to this article? Carbon sources can provide energy for microorganisms [46–47], and microorganisms can grow rapidly when they encounter abundant C sources, e.g., the significant increase in MBC in organic materials amendment treatments when compared with the control treatment in the three soils at the end of the 1st month (Fig 2). In agricultural systems, the return of organic materials to the soil is the most prevalent practice to maintain or improve soil fertility. Microbial biomass C and N were estimated by the difference between the total organic C or total N in the fumigated and non-fumigated extracts with a conversion factor (KEC) of 0.38 and (KEN) of 0.45 [40–41], respectively. Principal component analysis (PCA) of the Ecoplate data was performed to characterize the effect of different organic materials on soil microbial community functions, and the differences of the factor scores of the first principal component (PC1) axis among organic material treatments at each soil were tested using a one-way ANOVA by Tukey’s HSD (α = 0.05) test at P < 0.05. Soil Sci. Significantly higher MBC and MBN were found in Calcaric Cambisol and Luvic Phaeozem than that in Ferralic Cambisol regardless of organic material type (P < 0.05, Fig 2A and 2C). Different letters indicate significant differences at P < 0.05 among different materials in the same soil. Lignin is resistant to biodegradation and higher lignin content depresses microbial metabolism; this resulted in the negative correlation between lignin content and the diversity indices (Shannon and Simpson indices) in different organic material treatments at the end of the 1st month [17, 45]. https://doi.org/10.1371/journal.pone.0203812.s001, https://doi.org/10.1371/journal.pone.0203812.s002. Soil and rhizosphere microbial communities in agroecosystems may be affected by soil, climate, plant species, and management. A 20-g subsample of soil (oven-dried basis) was fumigated by exposing the soil to alcohol-free CHCl3 vapor in a sealed vacuum desiccator for 24 h. The fumigated soil was evacuated repeatedly in a clean empty desiccator until the odor of CHCl3 was not detected, and then extracted with 80 ml 0.5 M K2SO4 (soil:K2SO4 = 1:4) for 30 min. Soil properties had less influence on microbial biomass when compared with the organic material quality, with significant effects only observed at the end of the 1st month (Table 3). Soil texture can also affect the soil nutrient status and water content, thus affecting the living environment and metabolic activity of microorganisms [31–32]. The average well color development (AWCD) and the functional diversity indices including Shannon, Simpson and McIntosh indices were often used to investigate the general structure and functional potential of soil microbial communities [13, 24]. 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