亚热带常见造林树种对土壤细菌及微生物功能群的影响

为揭示亚热带人工林常见造林树种对森林土壤微生物群落的影响,本研究选取马尾松、米老排、枫香、冬青、火力楠、麻栎和光皮桦7个树种为研究对象,采用16S rRNA高通量测序和实时荧光定量PCR技术,探究不同树种土壤细菌的多样性、群落构成以及微生物功能群基因丰度。结果表明: 变形菌门、酸杆菌门和放线菌门是亚热带造林树种的优势细菌门,不同树种细菌多样性和丰富度指数无显著差异。冗余分析表明,土壤容重、土壤C/N、凋落物氮和凋落物C/N是影响土壤细菌组成的主要环境因子。不同造林树种土壤中氨氧化古菌、氨氧化细菌和完全氨氧化菌amoA基因丰度均具有显著差异。完全氨氧化菌在数量上占据优势地位,但只有氨氧化古菌amoA基因丰度与土壤硝态氮呈显著正相关关系,表明氨氧化古菌在亚热带酸性森林土壤自养硝化作用中可能发挥主要作用。相关分析表明,凋落物氮是不同树种影响氨氧化微生物丰度变化的关键驱动因子。本研究表明,土壤微生物功能群对树种的响应比细菌群落结构更加敏感,未来应从微生物功能群角度深入探究不同造林树种对森林生态系统功能的影响机制。     

保护性耕作对东北黑土微生物碳循环功能基因的影响

土壤微生物既参与土壤有机碳的分解也是土壤有机碳转化和固定的驱动者,是影响土壤碳循环和有机碳稳定性的关键因素。然而,保护性耕作（秸秆还田）如何通过调节土壤微生物碳循环功能基因组成来影响土壤CO₂释放的机理尚不明确。因此,依托中国科学院东北地理与农业生态研究所长春保护性耕作观测站,借助鸟枪法宏基因组测序技术,分析了玉米连作系统不同耕作方式（免耕（NT）、秋翻（MP）以及常规耕作（CT））对土壤CO₂释放速率、碳水化合物活性酶（CAZy）、碳循环功能基因（碳固定、甲烷代谢以及碳水化合物代谢）组成的影响。研究表明：基于生长季节土壤CO₂释放速率6年平均值分析发现,生长季前期免耕土壤的平均CO₂释放速率显著低于秋翻和常规耕作,分别比秋翻低28%（5月份）、11%（6月份）和23%（7月份）;比常规耕作低31%（5月份）、19%（6月份）和7%（7月份）。基于CAZy数据库注释结果,发现耕作处理显著影响一些糖苷水解酶（如GH102、GH5_38和GH13_17）、糖基转移酶（如GT39）和多糖裂解酶（如PL17和PL5_1）的基因丰度,与常规耕作相比,秸秆还田的免耕和秋翻处理的这些差异基因的相对丰度较高。基于京都基因与基因组百科全书（KEGG）数据库注释结果,发现耕作方式显著影响土壤碳循环功能基因组成（Adonis,多元方差分析,R²=0.45;P=0.006）,且免耕处理土壤的碳固定、甲烷代谢以及碳水化合物代谢功能基因组成不同于常规耕作和秋翻处理,单独聚为一类。免耕土壤上调的碳固定功能基因的相对丰度（所有上调功能基因相对丰度的平均值）分别比常规耕作和秋翻高17%和11%,而下调的2个功能基因（K01007和K00170）的丰度分别低19%（CT）、21%（MP）和14%（CT）、17%（MP）。免耕土壤上调的甲烷代谢基因相对丰度分别较常规耕作和秋翻高15%和10%;下调基因的丰度分别低13%（CT）和11%（MP）。免耕土壤上调的碳水化合物代谢功能基因丰度较常规耕作和秋翻高23%和14%;下调的基因丰度分别低25%（CT）和18%（MP）。冗余分析（db-RDA）表明土壤容重及土壤水溶性有机碳（DOC）是驱动土壤碳循环功能基因组成差异的主要因子（P<0.05）,且免耕土壤上调的碳固定功能基因（K00625、K01676、K09709、K00925和K14470等）、甲烷代谢基因（K03520、K00830、K10713、K15633和K00625等）和碳水化合物代谢功能基因（K00886、K00830、K01676、K00117和K00114等）与土壤DOC、容重或含水量呈显著正相关。此外,研究发现土壤CO₂释放速率与土壤碳循环功能基因组成显著相关（R²=0.80;P<0.01）,尤其是与一些碳水化合物代谢功能基因显著相关。这些结果说明免耕处理通过影响土壤理化性质改变土壤碳循环过程,且推断免耕秸秆还田和减少干扰的叠加效应通过调节碳循环功能基因组成来提高土壤固碳潜力。     

Effect of starch and inorganic nitrogen on microbial transformations of organic compounds in soil

It was found in long-term incubation experiments (100 weeks) that in soil non amended with organic compounds, mineralization proceeded in a steady state after an initial reactive respiration and corresponded approximately to the rate of mineralization of soil organic matter under natural conditions. The addition of nitrogen influenced this mineralization process only very slightly. The addition of starch decreased the stability of organic compounds in the soil at first but the newly formed organic substances were gradually stabilized again. The addition of nitrogen to starch increased the extent and the rate of these alterations. The overall extent of mineralization of the substrate after the addition of starch alone exceeds the amount of the added substrate; a small accumulation of the substrate could be observed after the addition of starch together with nitrogen.     

树种多样性对土壤微生物群落结构和元素生物地球化学循环的影响研究进展

森林是陆地生态系统的重要组成部分,其巨大的生产力和生态服务功能对人类的生存和发展至关重要。森林树种多样性增加能够显著提高森林生产力,关于树种多样性如何影响地下生物多样性及生态功能逐渐受到国内外学者的广泛关注。从土壤微生物及其介导的元素生物地球化学循环这一视角出发,综述了树种多样性对土壤细菌和真菌多样性、群落结构及功能的影响,提出需要进一步深入研究的方向。总体来说,树种多样性有利于增加土壤细菌生物量和多样性,是预测病原性真菌和菌根真菌多样性及群落结构的重要生物因子。树种多样性能增加土壤有机碳储量,增强森林土壤的甲烷氧化能力,并提高土壤磷周转速率及有效磷含量。关于树种多样性对森林土壤氮循环的影响需考虑多样性假说和质量比假说的相对贡献。今后应加强树种多样性对多个营养级之间相互作用的研究;关注树种多样性对生态系统多功能的影响;加强学科交叉,引入微生物种群动态模型和气候模型等模型预测方法,研究树种多样性对全球气候变化的应对机制,以期促进地上植物多样性与地下生态系统功能关系的研究,增强森林生态系统应对未来全球环境变化的能力。     

树种多样性和土壤微生物多样性对人工林生产力的影响

林分生产力通常会随着树种多样性增加而增加,但不同营养级生物多样性以及树种和土壤微生物多样性之间的相互作用如何影响生产力目前尚不清楚。以亚热带不同丰富度和树种组成的人工林为研究对象,从物种、功能性状、遗传三个维度的树种多样性以及土壤真菌和细菌系统发育多样性,探究了中国亚热带人工林树种多样性和土壤微生物多样性对林分生产力的影响。研究发现,林分生产力随树种功能多样性(FD)(P<0.001)、比叶面积群落加权均值(CWM-SLA)(P<0.01)、树种系统发育多样性(PD)(P<0.05)和土壤真菌多样性(PDF)(P<0.01)的增加而显著增加,分别解释了林分生产力总变异的12.86%、6.80%、3.67%和3.08%。FD和CWM-SLA可分别通过增加土壤真菌、细菌多样性而间接提高林分生产力。研究结果表明多营养级生物多样性是维持高水平林分生产力的基础,树种多样性和土壤微生物多样性之间的自上而下的级联效应在调节生态系统生产力方面发挥着重要作用。     

Grass species and soil type effects on microbial biomass and activity

We evaluated plant versus soil type controls on microbial biomass and activity by comparing microbial biomass C, soil respiration, denitrification potential, potential net N mineralization and nitrification in different soils supporting four grass species, and by growing a group of 10 different grass species on the same soil, in two experiments respectively. In the first experiment, none of the microbial variables showed significant variation with grass species while all variables showed significant variation with soil type, likely due to variation in soil texture. In the second experiment, there were few significant differences in microbial biomass C among the 10 grasses but there were significant relationships between variation in microbial biomass C and potential net N mineralization (negative), soil respiration (positive) and denitrification (positive). There was no relationship between microbial biomass C and either plant yield or plant N concentration. The results suggest that 1) soil type is a more important controller of microbial biomass and activity than grass species, 2) that different grass species can create significant, but small and infrequent, differences in microbial biomass and activity in soil, and 3) that plant-induced variation in microbial biomass and activity is caused by variation in labile C input to soil.     

湿地土壤微生物功能多样性及碳氮组分对长期氮输入的响应

氮输入对湿地生态系统碳氮循环具有重要影响,研究湿地土壤微生物功能多样性及碳氮组分对氮输入的响应,对于明确湿地土壤碳氮循环微生物驱动机制具有重要意义。依托长期野外氮输入模拟试验,利用Biolog-ECO微平板技术,分析不同浓度氮输入:N1(6 g N m^-2 a^-1)、N2(12 g N m^-2 a^-1)和N3(24 g N m^-2 a^-1)对湿地土壤表层(0-15 cm)和亚表层(15-30 cm)微生物碳源代谢活性、功能多样性和碳氮组分的影响。结果表明:N2处理显著提高了亚表层土壤微生物碳源代谢活性和McIntosh指数,N3处理显著降低了表层土壤微生物Shannon指数和Shannon-evenness指数。随氮输入浓度增加湿地表层土壤微生物对糖类的利用率显著降低,N3处理表层土壤微生物对胺类的利用率以及亚表层土壤微生物对醇类的利用率显著提高。N1处理显著提高了湿地表层土壤全氮和微生物量碳含量;N2、N3处理显著提高了土壤铵态氮、硝态氮含量;N3处理显著降低了土壤pH值。湿地土壤pH、总碳、溶解性有机碳含量是影响微生物碳源代谢活性和功能多样性的重要因素,土壤溶解性有机碳、铵态氮、全氮含量、含水率是影响微生物碳源利用变化的主要因子。     

The effects of stubble retention and nitrogen application on soil microbial community structure and functional gene abundance under irrigated maize

The effects of agronomic management practices on the soil microbial community were investigated in a maize production system in New South Wales, Australia. The site has been intensively studied to measure the impact of stubble management and N-fertilizer application on greenhouse gas emissions (CO(2) and N(2)O), N-cycling, pathology, soil structure and yield. As all of these endpoints can be regulated by microbial processes, the microbiology of the system was examined. Soil samples were taken after a winter fallow period and the diversity of the bacterial and fungal communities was measured using PCR-denaturing gradient gel electrophoresis. Stubble and N shifted the structure of bacterial and fungal communities with the primary driver being stubble addition on the fungal community structure (P<0.05 for all effects). Changes in C, N (total and NO(3)), K and Na, were correlated (P<0.05) with variation in the microbial community structure. Quantitative PCR showed that nifH (nitrogen fixation) and napA (denitrification) gene abundance increased upon stubble retention, whereas amoA gene numbers were increased by N addition. These results showed that the management of both stubble and N have significant and long-term impacts on the size and structure of the soil microbial community at phylogenetic and functional levels.     

亚热带树种转换对林地土壤微生物群落结构和功能的影响

通过分析杉木采伐迹地营造阔叶树种尾巨桉和固氮树种黑木相思人工林后土壤微生物群落组成和酶活性,探讨造林树种转换对于改善杉木林地土壤微生物特性的影响.结果表明: 树种转换对土壤微生物群落组成和酶活性的影响主要局限于0～10 cm土壤层.杉木转换为固氮树种黑木相思后,显著提高了0～10 cm土壤层总脂肪酸含量、真菌、革兰氏阳性细菌、革兰氏阴性细菌和放线菌生物量.主成分分析表明,黑木相思人工林土壤微生物群落组成与杉木和尾巨桉人工林具有显著差异,土壤中革兰氏阳性细菌、阴性细菌和放线菌丰度显著提高.在0～10 cm土壤层,黑木相思人工林土壤纤维素水解酶、乙酰氨基-葡萄糖苷酶和酸性磷酸酶活性均显著高于杉木和尾巨桉人工林.研究表明,杉木转变为固氮树种黑木相思后会显著提高微生物生物量和酶活性,有助于土壤有机质的恢复,加快养分循环过程.     

The effect of single tree species on soil microbial activities related to C and N cycling in the Siberian artificial afforestation experiment

The effects of grassland conversion to forest vegetation and of individual tree species on microbial activity in Siberia are largely unstudied. Here, we examined the effects of the six most commonly dominant tree species in Siberian forests (Scots pine, spruce, Arolla pine, larch, aspen and birch) on soil C and N mineralization, N₂O-reduction and N₂O production during denitrification 30 years after planting. We also documented the effect of grassland conversion to different tree species on microbial activities at different soil depths and their relationships to soil chemical properties. The effects of tree species and grassland conversion were more pronounced on N than on C transformations. Tree species and grassland conversion did significantly alter substrate-induced respiration (SIR) and basal respiration, but the differences were not as large as those observed for N transformations. Variances in SIR and basal respiration within species were markedly lower than those in N transformations. Net N mineralization, net nitrification, and denitrification potential were highest under Arolla pine and larch, intermediate under deciduous aspen and birch, and lowest beneath spruce and Scots pine. Tree species caused similar effects on denitrification potential, net N mineralization, and net nitrification, but effects on N₂O reduction rate were idiosyncratic, indicating a decoupling of N₂O production and reduction. We predict that deciduous species should produce more N₂O in the field than conifers, and that Siberian forests will produce more N₂O if global climate change alters tree species composition. Basal respiration and SIR showed inverse responses to tree species: when basal respiration increased in response to a given tree species, SIR declined. SIR may have been controlled by NH₄ ⁺ availability and related therefore to N mineralization, which was negatively affected by grassland conversion. Basal respiration appeared to be less limited by NH₄ ⁺ and controlled mostly by readily available organic C (DOC), which was higher in concentration under forests than in grassland and therefore basal respiration was higher in forested soils. We conclude that in the Siberian artificial afforestation experiment, soil C mineralization was not limited by N.     

Consistent effects of nitrogen amendments on soil microbial communities and processes across biomes

Ecosystems worldwide are receiving increasing amounts of reactive nitrogen (N) via anthropogenic activities with the added N having potentially important impacts on microbially mediated belowground carbon dynamics. However, a comprehensive understanding of how elevated N availability affects soil microbial processes and community dynamics remains incomplete. The mechanisms responsible for the observed responses are poorly resolved and we do not know if soil microbial communities respond in a similar manner across ecosystems. We collected 28 soils from a broad range of ecosystems in North America, amended soils with inorganic N, and incubated the soils under controlled conditions for 1 year. Consistent across nearly all soils, N addition decreased microbial respiration rates, with an average decrease of 11% over the year‐long incubation, and decreased microbial biomass by 35%. High‐throughput pyrosequencing showed that N addition consistently altered bacterial community composition, increasing the relative abundance of Actinobacteria and Firmicutes, and decreasing the relative abundance of Acidobacteria and Verrucomicrobia. Further, N‐amended soils consistently had lower activities in a broad suite of extracellular enzymes and had decreased temperature sensitivity, suggesting a shift to the preferential decomposition of more labile C pools. The observed trends held across strong gradients in climate and soil characteristics, indicating that the soil microbial responses to N addition are likely controlled by similar wide‐spread mechanisms. Our results support the hypothesis that N addition depresses soil microbial activity by shifting the metabolic capabilities of soil bacterial communities, yielding communities that are less capable of decomposing more recalcitrant soil carbon pools and leading to a potential increase in soil carbon sequestration rates.     

Effects of N-serve on soybeans and soil nitrogen transformations

Summary Plant dry weight, total N, and total Ca was increased at 0.1 and 1 ppm N-serve. At greater 10 ppm the plants showed visual symptoms of a stunted growth, stem elongation, flowers, and pods failed to form or were aborted, young leaves were curled, and roots were club shaped with many branches. These symptoms were increasingly evident with increasing N-serve application rates. The reason was attributed to an auxin effect. Dry wt and total N in the plant was less than the control at the higher N-serve applications. There was little effect on nitrogenase activity at less than 10 ppm N-serve. Nodulation tended to increase at 0.1 and 1 ppm N-serve.Nitrification was inhibited up to 104 days at 20 ppm N-serve. The soil pH of the high N-serve rates was decreased at 104 days probably due to nitrification. Generally there were little detectable differences among treatments in soil organic N. The average soil organic N from 0 to 104 days decreased by 0.01%. Average increase in total N within each pot at harvest was equivalent to about 138 kg N/ha.     

玉米间作和施氮对土壤微生物代谢功能多样性的影响

微生物功能多样性是土壤健康的重要指标,在多种生物地球化学过程中发挥关键作用.本研究基于多年田间小区定位试验,设置间作和单作2种种植模式和4个施氮水平(N0,0 kg·hm-2;N125,125 kg·hm-2;N250,250 kg·hm-2;N375,375 kg·hm-2),采用 Biolog-Eco微平板法,分析...     

Microscale heterogeneity of the soil nitrogen cycling microbial functional structure and potential metabolism

Soil aggregates, with complex spatial and nutritional heterogeneity, are clearly important for regulating microbial community ecology and biogeochemistry in soils. However, how the taxonomic composition and functional attributes of N-cycling-microbes within different soil particle-size fractions under a long-term fertilization treatment remains largely unknown. Here, we examined the composition and metabolic potential for urease activity, nitrification, N₂O production and reduction of the microbial communities attached to different sized soil particles (2000–250, 250–53 and <53 μm) using a functional gene microarray (GeoChip) and functional assays. We found that urease activity and nitrification were higher in <53 μm fractions, whereas N₂O production and reduction rates were greater in 2000–250 and 250–53 μm across different fertilizer regimes. The abundance of key N-cycling genes involved in anammox, ammonification, assimilatory and dissimilatory N reduction, denitrification, nitrification and N₂-fixation detected by GeoChip increased as soil aggregate size decreased; and the particular key genes abundance (e.g., ureC, amoA, narG, nirS/K) and their corresponding activity were uncoupled. Aggregate fraction exerted significant impacts on N-cycling microbial taxonomic composition, which was significantly shaped by soil nutrition. Taken together, these findings indicate the important roles of soil aggregates in differentiating N-cycling metabolic potential and taxonomic composition, and provide empirical evidence that nitrogen metabolism potential and community are uncoupled due to aggregate heterogeneity.