This study aimed to investigate the changes in textural properties of two potato varieties (JZ-226 and XS-6) during boiling and to elucidate the interaction mechanisms within their starch-pectin composite systems, and their impacts on textural characteristics. The results showed that during the boiling process, both potato varieties exhibited decreased hardness and chewiness. As the boiling time lengthened, starch underwent gelatinization; the amylose content dropped; water solubility increased; and the swelling power, transparency, and iodine blue value reduced. Meanwhile, pectin degraded, with the degree of esterification increasing; the content of protopectin and other bound pectins decreased; and water-soluble pectin increased, along with molecular weight rising. In the early stages of gelatinization (15 min), the addition of pectin inhibited the short-range orderliness of starch, forming a relatively stable network structure. However, prolonged gelation disrupts the gel network structure of the starch-pectin complex, leading to further textural changes. Compared to XS-6, the pectin in JZ-226 demonstrated a stronger ability to inhibit starch short-range orderliness, forming a more stable network structure, thereby maintaining superior hardness. These findings provide a theoretical basis for understanding the molecular mechanisms underlying textural changes in potato processing and offer technical support for developing functional potato products.

Chronic metabolic disease is a serious global health issue, which is accompanied by impaired insulin resistance. Tomato pectin (TP) is a naturally soluble complex hetero-polysaccharide with various biological functions. However, the impact of TP on hepatic insulin resistance in a high-fat diet (HFD) and its potential mechanism remains largely unknown. The results revealed that TP treatment significantly decreased the liver weight, hepatic fat accumulation and hepatic injury in HFD-fed mice. TP also improved fasting blood glucose levels and glucose tolerance in HFD-fed mice. The underlying mechanisms involved in the inflammation, oxidative stress and insulin signaling in the liver were also investigated by RT-qPCR and western blot, which indicated that TP ameliorated hepatic insulin resistance by regulating the PI3K/AKT/GSK-3β pathway, increasing the expression of GLUT4, decreasing the expression of PECK and G6P as well as restoring antioxidant activities and suppressing the inflammation statues in HFD-fed mice. Our data showed that dietary TP has profound effects on hepatic insulin resistance, inflammation and oxidative stress, demonstrating that TP might be a promising therapeutic agent against insulin resistance and related chronic metabolic disease.

Fresh agricultural products are frequently contaminated with Listeria monocytogenes (L. monocytogenes), which threatens consumer health. The mechanism of the inhibitory effect of ultrasound and sodium hypochlorite (USNaClO) on L. monocytogenes on fresh-cut cucumber remains poorly understood. Therefore, the bactericidal ability and mechanism of US-NaClO treatment on L. monocytogenes were studied on fresh-cut cucumber during storage using various approaches such as determination of intracellular material leakage, scanning electron microscopy, flow cytometry, and expression analysis of virulence genes. The results showed that the number of L. monocytogenes on fresh-cut cucumber was significantly reduced after ultrasound treatment for 5 min in combined with 75 ppm sodium hypochlorite treatment(P < 0.05). The US-NaClO treatment affected cell morphology, impaired cell membrane integrity, increased cell membrane permeability, and reduced the concentration of K+, inorganic phosphate, ATP, proteins, and DNA in bacterial cells, leading to the inactivation of microorganisms. In addition, the US-NaClO treatment downregulated expression of the virulence genes actA, hly, inlA, mpl, pclA, and plcB, thus decreasing the pathogenicity of bacteria. It can avoid contamination by pathogenic bacteria during the production of fresh-cut cucumber, while providing safety assurance for production.

土壤农化分析实验课程是农业资源与环境专业的专业核心课程.针对课程前期教学中存在的问题,结合新农科背景下高质量人才培养需求,从学生实验操作能力与实验安全意识提升、实验兴趣培养与实验项目设置、教学方式及考核形式等环节对课程教学进行了改革探索.土壤农化分析实验课程的教学改革不仅有助于提高教学效率,还可以充分调动学生学习的积极性,提升新农科背景下应用型、复合型人才培养的质量.

To study the microbial community succession during cow manure composting under different ventilation conditions,using cow manure and straw as raw materials,two treatments of continuous ventilation (K1,aeration rates 0.2 L·kg -1 ·min -1 ) and intermittent ventilation (K2,average aeration rates 0.2 L·kg -1 ·min -1 ;aerate 10 min,stop 10 min) were set up to carry out aerobic composting experiment in the reactor.The microbial community succession and response to environmental factors were analyzed by high-throughput sequencing technology.The results showed that the bacterial and fungal community structure changed greatly in the entire composting.In the initial stage of composting,Proteobacteria （62.07%） in mixed raw materials of cow manure and corn straw was the dominant phylum of bacteria.Firmicutes was the dominant phyla in the thermophilic period,the relative abundance of Firmicutes in K2 treatment （83.09%） was significantly higher than K1 treatment （57.79%）.Bacillus and Solibacillus were the predominant groups in the thermophilic period of composting.The relative abundance of Bacillus in K1 and K2 treatments were 13.67%and 32.61%,respectively,and the relative abundance of Solibacillus were 7.2%and 23.05%,respectively.Ascomycota and Basidiomycota were the dominant phylum of fungi in the whole composting process.In the thermophilic period of composting,the proportion of Ascomycota in K1 and K2 treatments were58.11%and 78.11%,respectively.The relative abundance of Kurtzmaniella-Candida clade in K2 treatment （25.67%） was significantly higher than that in K1 treatment （7.85%）,which was the dominant genus in the thermophilic period of composting.The redundancy analysis （RDA） results showed that temperature,NH 4 + -N and C/N ratio were the main environmental factors affecting the bacterial and fungal community structure during the thermophilic period.The pH value,NO 3 - -N and TN had great influence on the bacterial and fungal community structure in cooling and maturity stage.Intermittent ventilation was beneficial to the increase of the relative abundance of Firmicutes in the thermophilic period of composting,and significantly increased the relative abundance of Bacillus and Solibacillus.Intermittent ventilation was beneficial to the increase of relative abundance of Ascomycota and Kurtzmaniella-Candida clade in the thermophilic period.

Soil organic matter (SOM) fractions play a key role in sustaining soil productivity; however, these fractions are relatively low in agricultural soils due to crop residue removal and tillage practices. Straw return has been reported to improve SOM fractions; however, its effects on soils with different nitrogen status is lacking. Therefore, a two-year experiment was conducted on an existing five-year different nitrogen rates (0, 75, 150 and 375 kg Nha- 1 yr-1) trial field to assess the effects of nitrogen fertilizer rate and straw return on SOM fractions at different soil depths. The experiment had four nitrogen rates: 0 (CK, control), 75 (low N, LN), 150 (medium N, MN), and 375 (high N, HN) kg Nha- 1 yr-1 with and without straw return (S, 9 t ha-1). The results showed that straw return significantly stimulated the SOM fractions at both 0-20 and 20-40 cm soil depths. Compared with the control, treatment MN with straw increased carbon pool management index (28.52 %), dissolved organic carbon (45.89 %), microbial biomass carbon (66.11 %), readily organic carbon (27.07 %), humic acid carbon (21.69 %), and humin carbon (10.34 %) at 0-20 cm soil depth; however, these fractions were comparable to those of HN with straw. Total organic carbon and carbon pool management index showed a positive and significant correlation with labile SOM fractions in the soil. The application of 150 kg N ha-1 after straw return stimulates SOM fractions, which in turn maintains the fertility and productivity of loess soil.

通过土培收集、硅烷衍生化分离、气质联用鉴定马铃薯苗期、现蕾期及盛花期根系分泌物的主要成分,并采用半固体平板法、类毛细管法和结晶紫染色法比较观察马铃薯不同生育时期根系分泌物及氨基酸对萎缩芽孢杆菌QHZ3 趋化成膜的影响,以揭示菌株QHZ3 在马铃薯根际的定殖机制.马铃薯根系分泌物鉴定中发现了 5 种氨基酸:脯氨酸、甘氨酸、天冬氨酸、苯丙氨酸和酪氨酸.定性试验显示,马铃薯不同生育时期的根系分泌物和除脯氨酸之外的其他 4 种氨基酸均对菌株QHZ3 具有显著的正趋化作用,并以甘氨酸的作用最强,其趋化圈直径(6.40 cm)是对照(3.48 cm)的1.84 倍;定量试验结果表明,根系分泌物(120 μg?mL-1和240 μg?mL-1)、甘氨酸(10～50 μmol?L-1)、天冬氨酸(50～75 μmol?L-1)和苯丙氨酸(25～50 μmol?L-1)均对菌株QHZ3 有显著正趋化作用,尤其以 25 μmol?L-1的甘氨酸趋化性指数最大,其毛细管中细菌数量(5.13×105 CFU?mL-1)达到对照组(1.53×105 CFU?mL-1)的 3.3 倍;结晶紫染色法显示,现蕾期和盛花期根系分泌物以及甘氨酸(25～100 μmol?L-1)、脯氨酸(75～100 μmol?L-1)和苯丙氨酸(25～100 μmol?L-1)均对菌株QHZ3 生物膜的形成有显著促进作用.根系分泌物和氨基酸均对菌株QHZ3 在马铃薯根际趋化成膜具有促进作用,但 5 种氨基酸的作用各不相同,其中天冬氨酸和酪氨酸显著影响菌株的趋化作用,脯氨酸显著影响了菌株生物膜的形成,而甘氨酸和苯丙氨酸则对菌株的趋化和成膜兼具显著效果.

The influence of ultrasound combined with sodium hypochlorite (US-NaClO) treatment on microorganisms and quality of fresh-cut cucumber during storage were investigated. Ultrasound (400 W, 40 kHz, US: 5, 10 and 15 min) and sodium hypochlorite (NaClO: 50, 75, 100 ppm) were used to treat fresh-cut cucumber in a single or combined treatment and stored at 4 °C for 8 days and analyzed for texture, color and flavor. The results showed that US-NaClO treatment had a synergistic effect on the inhibition of microorganisms during storage. It could significantly reduce (p < 0.05) the number of microorganisms by 1.73 to 2.17 log CFU/g. In addition, US-NaClO treatment reduced the accumulation of malondialdehyde (MDA) during storage (4.42 nmol/g) and water mobility, and maintained the integrity of the cell membrane, delayed the increase of weight loss (3.21%), reduced water loss, thus slowing down the decline of firmness (9.20%) of fresh-cut cucumber during storage. The degradation of chlorophyll (6.41%) was reduced to maintain the color of freshly cut cucumbers. At the same time, US-NaClO could maintain the content of aldehydes, the main aromatic substance of cucumber, and reduced the content of alcohols and ketones during storage. Combined with the electronic nose results, it could maintain the cucumber flavor at the end of the storage period and reduce the odor produced by microorganisms. Overall, US-NaClO was helpful to inhibit the growth of microorganisms during storage, improve the quality of fresh-cut cucumber.

以豌豆分离蛋白(PPI)为原料,添加卡拉胶(CGN),制备豌豆蛋白—卡拉胶(PPI-CGN)复合膜,研究卡拉胶对复合膜性能的影响.结果表明:添加0.6％～1.4％的卡拉胶时,随着卡拉胶添加量的增加,复合粒子的粒径和Zeta电位绝对值显著增大(p＜0.05),复合膜的厚度、水蒸气透过率、水溶性、不透明度逐渐增大(p＞0.05),复合膜的机械强度、L*值和a*值呈先增大后减小的趋势(p＞0.05).与豌豆蛋白膜相比,复合粒子的粒径和Zeta电位绝对值、复合膜的抗拉伸强度和色度显著增大(p＜0.05),断裂伸长率和溶解度显著降低(p＜0.05).

针对沈阳农业大学食品专业《植物蛋白质工艺学》课程教学的现状及其存在的问题,以"金课"为导向开展课程教学模式改革探讨,提出优化课程教学内容、构建多元化教学模式、采用过程性多元化考核方式等建议,以提高《植物蛋白质工艺学》课程教学质量.

以豌豆分离蛋白(PPI)为原料,添加卡拉胶(CGN)制备豌豆蛋白—卡拉胶(PPI-CGN)复合膜,并研究超声处理对复合膜性能的影响.结果表明:超声处理显著提高了PPI-CGN复合粒子的Zeta电位绝对值和复合膜的机械性能、阻隔性及溶胀度(p<0.05);降低了复合粒子的粒径和复合膜的厚度、溶解度及水分含量(p<0.05).与豌豆蛋白膜相比,经超声处理的PPI-CGN复合膜的粒径、Zeta电位绝对值、机械性能、水分含量、阻隔性均显著提高(p<0.05);水溶性显著降低(p<0.05).

The tuber yield of potato in China is relatively low compared to the average global yield, partly due to poor nitrogen (N) management. Moreover, excessive N fertilization reduces the nitrogen use efficiency (NUE) of potato and increases production costs, which reduces profit margins. Therefore, a 2-year field trial was conducted on an existing field with 5 years of different inorganic N fertilization rates in Dingxi to determine the effects of N fertilization rate on growth, tuber yield, net income and NUE of potato on a loess soil. The experiment included six N fertilization rates, namely 0 kg N ha−1 (N0), 75 kg N ha−1 (N1), 150 kg N ha−1 (N2), 225 kg N ha−1 (N3), 300 kg N ha−1 (N4) and 375 kg N ha−1 (N5). The treatments were laid out in a randomized complete block design and replicated four times. The results from the principal component analysis revealed that N fertilization has a strong effect on potato growth, tuber yield and NUE. Treatment N2 increased total tuber yield (29.0% and 33.1%) and net income (54.8% and 61.4%) of potato in 2018 and 2019 seasons, respectively, compared to the control. Excessive N fertilization (N5) reduced tuber yield, net income and NUE of potato in both seasons. To increase tuber yield, net income and NUE of potato (cultivar Qingshu 9) on a loess soil of Northwest China, N fertilization rate should not exceed 150 kg ha−1.

Due to the outbreak of COVID-19, a large number of disposable personal protective equipment (PPE) wastes were generated. It has caused great harm to the ecological environment, and even in the future may endanger human health. Therefore, it is of great significance to research biodegradable materials that can be used in the field of medical protective equipment. This article reviews the application of biodegradable materials in personal protective equipment. First of all, the classification, characteristics, and general application of biodegradable materials are described. Then, the application of biodegradable antibacterial materials, which can improve the degradability, antibacterial, and comfort of medical protective articles, is analyzed. Finally, the significance and challenges are discussed, and some prospects in this field are put forward.

Amino sugars are key microbial biomarkers for determining the contribution of microbial residues in soil organic matter (SOM). However, it remains largely unclear as to what extent inorganic nitrogen (N) fertilization can lead to the significant degradation of SOM in alkaline agricultural soils. A six-year field experiment was conducted from 2013 to 2018 to evaluate the effects of chronic N enrichment on microbial residues, amino sugars, and soil biochemical properties under four nitrogen (urea, 46% N) fertilization scenarios: 0 (no-N, control), 75 (low-N), 225 (medium-N), and 375 (high-N) kg N ha−1. The results showed that chronic N enrichment stimulated microbial residues and amino sugar accumulation over time. The medium-N treatment increased the concentration of muramic acid (15.77%), glucosamine (13.55%), galactosamine (18.84%), bacterial residues (16.88%), fungal residues (11.31%), and total microbial residues (12.57%) compared to the control in 2018; however, these concentrations were comparable to the high-N treatment concentrations. The ratio of glucosamine to galactosamine and of glucosamine to muramic acid decreased over time due to a larger increase in bacterial residues as compared to fungal residues. Microbial biomass, soil organic carbon, and aboveground plant biomass positively correlated with microbial residues and amino sugar components. Chronic N enrichment improved the soil biochemical properties and aboveground plant biomass, which stimulated microbial residues and amino sugar accumulation over time.

为定量年生长周期内猕猴桃树体各器官养分含量及养分携出量,确定猕猴桃果园年养分需求量和合理施肥量,在猕猴桃年生长周期内采集秦美、哑特和华优3个品种猕猴桃树体各器官样品,测定养分含量,计算养分携出量.同时在参照研究区成龄果园树体养分贮藏量的基础上,通过果园养分吸收量推算猕猴桃果园合理施肥量.结果表明:不同品种猕猴桃果实产量、单果质量、单叶质量及叶个数、枝条修剪量间均没有显著差异,各器官氮(N)、磷(P)、钾(K)养分含量亦无显著差异.猕猴桃果园每生长1 kg叶片吸收的养分量为N 2.81 g、P 0.31 g、K 2.13 g;每收获1 kg鲜果移出的养分量为N 1.40 g、P 0.47 g、K 2.23 g;每修剪1 kg枝条移出的养分量为N 3.70 g、P 0.47 g、K 2.94 g.年生长周期内果园因叶片吸收、果实收获、枝条修剪和树体贮藏的总养分量为N 162 kg?hm-2?a-1、P 36 kg?hm-2?a-1、K 146 kg?hm-2?a-1,其中来自肥料的养分为N 38.0 kg?hm-2?a-1、P 5.4 kg?hm-2?a-1、K 20.0 kg?hm-2?a-1.研究表明,不同品种成龄猕猴桃果园的推荐施肥量均为N 380 kg?hm-2?a-1、P 77 kg?hm-2?a-1、K 87 kg?hm-2?a-1,N:P2O5:K2O为1:0.5:0.3.

针对马铃薯生产实践中长期单施化肥或化肥过量施用等不合理施肥措施导致土壤碳库活性变差和土壤生物活性降低等问题.通过田间定位试验,分析不同施肥方式:不施肥(CK)、单施化肥(NPK)、单施有机肥(M)、有机无机肥配施(NPKM)对旱作马铃薯农田土壤有机碳组分和碳库管理指数的影响.结果显示,连续施肥5年后添加有机肥的M、NPKM处理较CK和NPK处理显著提高了土壤闭蓄态颗粒有机碳(OPOC)和土壤颗粒态有机碳(POC)含量,降低了土壤矿质结合态有机碳(MOC)含量.与CK和NPK处理相比,M、NPKM处理闭蓄态颗粒有机碳(OPOC)含量分别提高了 32.52％、30.39％和27.09％、24.78％;土壤颗粒态有机碳(POC)含量分别提高了 31.52％、29.65％和25.18％、23.15％.添加有机肥的M和NPKM处理显著提高了颗粒态有机碳(POC)的比例,降低了 MOC的比例,与CK和NPK相比,M、MNPK处理中POC的比例分别增加了 27.72％、25.23％和10.61％、7.54％,MOC的比例分别降低39.42％、33.16％和14.97％、9.81％.添加有机肥显著提高了土壤总有机碳(TOC)、微生物量碳(MBC)、易氧化有机碳(ROC)的含量,与CK处理相比,M和NPKM处理的TOC分别增加了 15.28％和13.64％,MBC增加了21.82％和19.17％,ROC的含量分别增加了 32.45％和31.35％;施用有机肥和有机无机配施均显著提高碳库管理指数(CPMI)较单施化肥分别提高28.8％和35.65％.综上所述,施用有机肥处理(M处理和MNPK处理)显著地提高了马铃薯农田土壤闭蓄态颗粒有机碳(OPOC)、颗粒态有机碳(POC)和总有机碳(TOC)及微生物量碳(MBC)、易氧化有机碳(ROC)含量,提高了土壤碳库管理指数;即马铃薯栽培施用有机肥有利于土壤活性有机碳的积累、能够改变土壤有机碳组分分布特征.

The average yield of fresh potato tubers per hectare is relatively low in China, partly due to poor nutrient management. Chronic inorganic N enrichment leads to soil acidification, which deteriorates soil fertility. Straw residues are removed from the field or burnt during land preparation, resulting in nutrient depletion and air pollution. However, these residues can be returned to the soil to improve its fertility. Therefore, a two–year experiment was conducted in an existing field with five years of different inorganic nitrogen (N) rate to determine the effects of straw return and N rate on potato growth, tuber yield, and quality, profit margin, and soil physicochemical properties. The experiment consisted of four N rates: 0 (control, CK), 75 (low N rate, LN), 150 (medium N rate, MN), and 300 (high N rate, HN) kg N ha−1 with and without straw (9 t ha−1) return. The results showed that straw with N enrichment improved soil fertility, which increased tuber yield and quality. Compared to the control, MN + straw treatment stimulated economic tuber yield (34.73% and 38.34%), profit margin (55.51% and 63.03%), and protein content (20.04% and 25.46%) in 2018 and 2019, respectively. Nitrogen enrichment after straw return is a sustainable practice for stimulating potato tuber yield, profit margin, and improving soil fertility to promote sustainable agriculture development.

Lignocellulosic materials have a complex physicochemical composition and structure that reduces their decomposition rate and hinders the formation of humic substances during composting. Therefore, a composting experiment was conducted to evaluate the effects of different C/N ratios on lignocellulose (cellulose, hemicellulose and lignin) degradation and the activities of corresponding enzymes during aerobic composting. The study had five C/N ratios, namely, T1 (C/N ratio of 15), T2 (C/N ratio of 20), T3 (C/N ratio of 25), T4 (C/N ratio of 30) and T5 (C/N ratio of 35). The results showed that treatments T3 and T4 had the highest rate of degradation of cellulose and hemicellulose, while treatment T3 had the highest rate of degradation of lignin. Among the five treatments, treatment T3 enhanced the degradation of the lignocellulose constituents, indicating a degradation rate of 6.86–35.17%, 15.63–44.08% and 31.69–165.60% for cellulose, hemicellulose and lignin, respectively. The degradation of cellulose and lignin occurred mainly at the thermophilic and late mesophilic phases of composting, while hemicellulose degradation occurred at the maturation phase. Treatment T3 was the best C/N ratio to stimulate the activities of manganese peroxidase, lignin peroxidase, polyphenol oxidase and peroxidase, which in turn promoted lignocellulose degradation.

为了揭示还田玉米秸秆在不同施氮水平下的腐解及养分释放特征,在马铃薯田间定位试验中,设置了6个不同施氮水平(T1:0 kg·hm-2;T2:75 kg·hm-2;T3:150 kg·hm-2;T4:225 kg·hm-2;T5:300 kg·hm-2;T6:375 kg·hm-2),研究其对还田玉米秸秆腐解及养分释放特征的影响.研究表明:还田玉米秸秆的腐解主要发生在前90 d,在此期间玉米秸秆腐解较快,T1～T6处理的玉米秸秆腐解率分别为37.3％、40.3％、44.8％、45.0％、50.8％、48.4％,以T5处理为最高,处理间差异显著(P<0.05);同时,T1～T6处理的玉米秸秆碳、氮释放率分别为48.2％～56.6％、33.8％～44.4％,T5处理下秸秆的碳、氮释放率均显著高于其他处理(P<0.05),而秸秆磷、钾的释放率分别为43.1％～49.2％、90.5％～93.0％,处理间无显著性差异.还田150 d后,玉米秸秆的腐解率为52.7％～55.8％,养分释放表现为K>C>P>N.综上所述,连续施氮可以显著促进还田玉米秸秆前期的腐解及碳氮的释放,但对磷钾的释放无明显影响,当施氮量为300 kg·hm-2时还田玉米秸秆的腐解效果最好.

为了揭示连续施用不同氮量对半干旱地区马铃薯根际细菌群落结构及反硝化作用的影响.通过大田试验设置了6个不同施氮量处理:N0(对照,不施氮)、N75(施氮量75 kg·hm-2)、N150(施氮量150 kg·hm-2)、N225(施氮量225 kg·hm-2)、N300(施氮量300 kg·hm-2)和N375(施氮量375 kg·hm-2),研究了连续5年不同施氮量对半干旱地区马铃薯根际细菌群落结构及反硝化作用过程中编码亚硝酸还原酶的关键酶基因nirK和nirS丰度的影响.结果显示:各处理土壤中NO3--N含量随施氮量的增加显著增加,最高施氮量处理(N375)土壤中NO3--N含量高达80.41 mg·kg-1,分别比其他处理增加了86.87％～856.12％;土壤亚硝酸还原酶活性随着施氮量的增加随之增强,高氮处理显著高于低氮处理.高通量测序结果显示,大量施氮降低了细菌群落的Alpha多样性,显著改变了土壤细菌群落的物种组成;与N0处理相比,其他各施氮处理根际土壤中变形菌门和厚壁菌门的相对丰度增加了1.66％～26.53％和22.59％～85.52％,放线菌门和酸杆菌门的相对丰度降低了3.48％～34.63％和4.21％～37.12％,高氮处理显著低于不施氮及低氮处理;高量施氮显著提高了根际土壤中Lactococcus、Bacillus和Ly-sobacter的相对丰度.根际土壤中nirK和nirS相对丰度随施氮量的增加随之增加,高氮处理中nirK和nirS相对丰度分别比N0处理增加了116.26％、101.49％和28.24％、8.47％.Person相关性分析表明,nirK相对丰度与土壤NO3--N含量呈显著正相关关系,pH与nirK和nirS的丰度呈显著负相关关系.大量施氮造成土壤剖面中NO3--N积累量的增加以及pH值降低是引起根际细菌群落结构以及nirK和nirS丰度变化的主要原因.