Diversity of soil bacteria and fungi communities in artificial forests of the sandy-hilly region of Northwest China

Soil erosion is a serious issue in the sandy-hilly region of Shanxi Province, Northwest China. There has been gradual improvement due to vegetation restoration, but soil microbial community characteristics in different vegetation plantation types have not been widely investigated. To address this, we analyzed soil bacterial and fungal community structures, diversity, and microbial and soil environmental factors in Caragana korshinskii Kom., Populus tomentosa Carr., Populus simonii Carr., Salix matsudana Koidz, and Pinus tabulaeformis Carr. forests. There were no significant differences in the dominant bacterial community compositions among the five forest types. The alpha diversity of the bacteria and fungi communities showed that ACE (abundance-based coverage estimator), Chao1, and Shannon indices in C. korshinskii forest were significantly higher than those in the other four forest types (P<0.05). Soil organic matter, total nitrogen, and urease had a greater impact on bacterial community composition, while total nitrogen, β-glucosidase, and urease had a greater impact on fungal community composition. The relative abundance of beneficial and pathogenic microorganisms was similar across all forest types. Based on microbial community composition, diversity, and soil fertility, we ranked the plantations from most to least suitable as follows: C. korshinskii, S. matsudana, P. tabulaeformis, P. tomentosa, and P. simonii.     

Changes in diversity,composition and assembly processes of soil microbial communities during Robinia pseudoacacia L. restoration on the Loess Plateau,China

Robinia pseudoacacia L. (RP) restoration has increased vegetation cover in semi-arid regions on the Loess Plateau of China, but ecological problems have also occurred due to RP restoration, such as reduced soil moisture. Further, it is still uncertain how microbial diversity, composition and assembly processes change with RP restoration in semi-arid regions. Therefore, amplicon sequencing of small subunit ribosomal ribonucleic acid (16S rRNA) and internal transcribed spacer (ITS) genes was performed to study soil bacterial and fungal diversity, composition and assembly processes at four study sites with different stand ages of RP plantations (Y10, RP plantation with stand ages less than 10 a; Y15, RP plantation with stand ages approximately 15 a; Y25, RP plantation with stand ages approximately 25 a; and Y40, RP plantation with stand ages approximately 40 a) along a 40-a chronosequence on the Loess Plateau. The diversity of soil bacteria and fungi increased significantly during the restoration period from 10 to 15 a (P<0.05). However, compared with Y15, bacterial diversity was lower at Y25 and Y40, and fungal diversity remained stable during the restoration period between 25 and 40 a. The relative abundances of Proteobacteria and Ascomycota increased during the restoration period from 10 to 15 a. Conversely, after 15 a of restoration, they both decreased, whereas the relative abundances of Actinomycetes, Acidobacteria and Basidiomycota gradually increased. The variations in soil bacterial communities were mainly related to changes in soil total nitrogen, nitrate nitrogen and moisture contents, while soil fungal communities were mainly shaped by soil organic carbon and nitrate nitrogen contents. Bacterial communities were structured by the heterogeneous selection and stochastic process, while fungal communities were structured primarily by the stochastic process. The RP restoration induced an increase in the relative importance of heterogeneous selection on bacterial communities. Overall, this study reveals the changes in microbial diversity, community composition and assembly processes with RP restoration on the Loess Plateau and provides a new perspective on the effects of vegetation restoration on soil microbial communities in semi-arid regions.     

黄柄曲霉ASD对辣椒疫病根际真菌菌群结构及土壤功能的影响

为阐明辣椒疫病生防菌黄柄曲霉ASD的土壤微生态调控机理,本研究利用化学方法与Illumina HiSeq平台分析了ASD菌液对罹病辣椒根际土壤特性及真菌多样性的影响。结果表明,ASD菌液的施入可以明显提高罹病土壤硝态氮与有效钾含量,降低铵态氮含量与N-乙酰基-β-D-氨基葡糖苷酶活性。ASD菌液增加了罹病辣椒根际土壤真菌多样性与丰度,从而改变了辣椒根际优势真菌群落构成。优势种群与发病率相关分析结果表明,丰度上升的嗜热链球菌属与嗜热毁丝霉属等9个物种与发病率呈负相关,丰度降低的斜盖伞属及近地伞属与发病率呈正相关。与环境因子相关性分析表明,有效钾、硝态氮的含量与ASD处理的土壤真菌多样性呈正相关,并正向影响锥盖伞属等10个物种,铵态氮含量及N-乙酰基-β-D-氨基葡糖苷酶活性则反之。综上所述,黄柄曲霉ASD可以增加辣椒疫病根际土壤真菌多样性,改变土壤营养状况与优势真菌种群结构,从而降低辣椒疫病的发病率。结果可为菌株ASD应用于生产实践提供理论基础。     

长期施用绿肥对小麦玉米间作土壤微生物的影响

利用Biolog微平板法和高通量测序技术，研究小麦玉米间作条件下，不同长期施肥处理土壤微生物对不同碳源的利用差异以及土壤微生物群落在门、属水平上的变化，探明长期施用绿肥对土壤微生物群落多样性及代谢功能的影响。结果表明：长期施用绿肥可显著提高土壤有机质、速效磷和速效钾含量，降低土壤pH值，增强土壤微生物碳源代谢能力。不同施肥条件下，放线菌门(Actinobacteria)和变形菌门(Proteobacteria)为土壤优势菌群，绿肥处理的放线菌门丰度最高(29.94%),农家肥处理最低(22.95%);秸秆还田处理的变形菌门丰度最高(22.32%),对照处理最低(18.85%);酸杆菌门(Acidobacteriota)、绿弯菌门(Chloroflexi)、厚壁菌门(Firmicutes)在各个处理中的相对丰富度较高，分别为13.39%～19.71%、10.85%～14.56%、3.54%～12.98%。长期施用绿肥有效提高了土壤放线菌门、厚壁菌门、芽孢杆菌属(Bacillus)以及假节杆菌属(Pseudarthrobacter)的丰度，降低了酸杆菌门的丰度，增加了土壤微生物种群数量。综...     

Succession of soil bacterial and fungal communities of Caragana korshinskii plantation in a typical agro-pastoral ecotone in northern China over a 50-a period

Bacterial and fungal communities play critical roles in reestablishing vegetation structure, function and biodiversity in ecosystem restoration in arid and semi-arid areas. However, the long-term successional changes in bacterial and fungal communities that occur with artificial vegetation development are not fully understood. In this study, we investigated the successional changes in bacterial and fungal communities in Caragana korshinskii Kom. plantation over a period of 50 a (6, 12, 18, 40 and 50 a) and their relationships with key soil environmental factors in a typical agro-pastoral ecotone, northern China. The results showed that bacterial and fungal diversities (α- and β-diversity) were significantly affected by plantation age; moreover, the change in fungal community was more evident than that in bacterial community. Soil samples from 12 a plantation had the highest (P<0.05) bacterial and fungal α-diversity (i.e., abundance-based coverage estimator (ACE) and Chao1 index) at 0-10 cm depth compared with other samples. However, soil samples from plantation at the late recovery stage (40-50 a) had the highest α-diversity at 10-20 cm depth. Soil bacterial community was not significantly affected by plantation age at the genus level; but, soil fungal community was significantly affected at the genus level. Overall, Mortierella and Chaetomium were the dominant genera at natural recovery stage (0 a); Inocybe was the dominant genus at the early recovery stage (6-12 a); Inocybe and Mortierella were the dominant genera at the mid-recovery stage (12-40 a); And Mortierella, Cladosporium and Humicola were the dominant genera at the late recovery stage (40-50 a). Redundancy analysis (RDA) showed that β-glucosidase activity, total nitrogen and soil organic carbon were closely associated with bacterial community composition, while alkaline phosphatase, urease activity and total nitrogen were associated with fungal community composition, indicating that changes in enzyme activity and soil nutrients were the most important determinants of dominant genera. Furthermore, pathogenic microorganisms (Cladosporium and Humicola) were dominant in soils from 40-50 a plantation, which may affect plant growth, resulting in the decline of C. korshinskii plantation. Overall, the findings of this study improve the understanding of ecological patterns of bacterial and fungal communities in artificial vegetation and provide an important scientific basis for comprehensive ecological restoration management in arid and semi-arid areas.     

长期施肥对渭北旱塬麦田土壤线虫群落特征的影响

为探究长期定位施肥对黄土高原渭北旱塬麦田土壤线虫群落的影响,以长武国家黄土高原农业生态试验站的长期定位试验（1984—2018年）为平台,调查裸地（L）以及不施肥（CK）、施氮磷肥（NP）、单施有机肥（M）、氮磷肥配施有机肥（MNP）的小麦田土壤线虫群落数量、组成结构和生态功能指数,并分析其与土壤理化性质的关系。结果表明：（1）小麦田土壤线虫数量显著高于裸地,而CK、M和MNP处理使小麦田中土壤线虫数量比NP处理提高了31.63%~56.20%;（2）施肥减缓了长期种植小麦导致的食细菌线虫（特别是头叶属）相对丰度的下降,单施有机肥的处理（M）植食性线虫相对丰度显著降低,同时,相比于CK,施用有机肥的M和MNP处理杂食/捕食线虫相对丰度分别增加了18.4%和8.24%,表明有机肥对杂食/捕食线虫的促进作用;（3）长期施肥处理土壤线虫Shannon多样性指数（H）和指示土壤健康状况的瓦斯乐卡指数（WI）分别为1.80~2.19和0.36~0.68,相较于裸地（H=2.36;WI=1.57）有所下降,但M和MNP处理的线虫成熟度指数（MI）和结构指数（SI）均高于其他处理（L、CK和NP处理）,表明施用有机肥有助于土壤食物网维持复杂的结构和成熟稳定的状态;（4）不同施肥措施下土壤全氮、有机碳、微生物生物量碳和氮以及可溶性碳的变化是影响土壤线虫数量和群落特征的重要环境因素。     

Changes in soil microbial community response to precipitation events in a semi-arid steppe of the Xilin River Basin,China

In the context of climate change, precipitation is predicted to become more intense at the global scale. Such change may alter soil microbial communities and the microbially mediated carbon and nitrogen dynamics. In this study, we experimentally repackaged precipitation patterns during the growing season(from June to September) of 2012 in a semi-arid temperate steppe of the Xilin River Basin in Inner Mongolia of China, based on the 60-year growing season precipitation data. Specifically, a total amount of 240 mm simulated precipitation was assigned to experimental plots by taking the following treatments:(1) P6(6 extreme precipitation events, near the 1~(st) percentile);(2) P10(10 extreme precipitation events, near the 5~(th) percentile);(3) P16(16 moderate precipitation events, near the 50~(th) percentile); and(4) P24(24 events, 60-year average precipitation, near the 50~(th) percentile). At the end of the growing season, we analyzed soil microbial community structure and biomass, bacterial abundance, fungal abundance and bacterial composition, by using phospholipid fatty acid(PLFA), real-time quantitative polymerase chain reaction(RT-qPCR) and 16S rRNA gene clone library methods. The extreme precipitation events did not change soil microbial community structure(represented by the ratio of PLFA concentration in fungi to PLFA concentration in bacteria, and the ratio of PLFA concentration in gram-positive bacterial biomass to PLFA concentration in gram-negative bacterial biomass). However, the extreme precipitation events significantly increased soil microbial activity(represented by soil microbial biomass nitrogen and soil bacterial 16S rRNA gene copy numbers). Soil fungal community showed no significant response to precipitation events. According to the redundancy analysis, both soil microbial biomass nitrogen and soil ammonium nitrogen(NH_4-N) were found to be significant in shaping soil microbial community. Acidobacteria, Actinobacteria and Proteobacteria were the dominant phyla in soil bacterial composition, and responded differently to the extreme precipitation events. Based on the results, we concluded that the extreme precipitation events altered the overall soil microbial activity, but did not impact how the processes would occur, since soil microbial community structure remained unchanged.     

冬灌制度对膜下滴灌棉田土壤理化性质、酶活性和微生物群落的影响

为明确不同冬灌制度的应用效果，以南疆膜下滴灌棉田为研究对象，选取每年冬灌处理（CK）、不冬灌处理（H1）及隔年冬灌处理（H2）3种冬灌制度，结合高通量测序技术对冬灌后土壤的理化性质、生物学性质以及微生物群落组成进行测定与分析。结果表明：（1）各处理间0~20 cm土层土壤总盐含量无显著差异，与CK相比，H1和H2处理显著降低了脲酶（0.96%~1.35%）和转化酶活性（1.17%）以及微生物量氮含量（4.21%~7.03%），但H2处理显著提高了土壤有机质（14.30%）、全氮（14.29%）、全磷（4.55%）和全钾（7.40%）含量；H1处理显著降低了土壤有机质（6.03%）、全磷（12.5%）和水分（23.08%）含量，提高了微生物量碳氮比（7.37%）。（2）不同处理下细菌群落的丰度和多样性以及真菌群落的丰度无显著差异，但与CK相比，H1和H2处理显著提高了真菌的辛普森指数（4.12%~ 4.55%）。此外，H1较CK处理提高了细菌放线菌门（Actinobacteria）、酸杆菌门（Acidobacteria）、绿弯菌门（Chloroflexi）和真菌担子菌门（Basidiomycota）的相对丰度，H2较CK处理提高了细菌变形菌门（Proteobacteria）、芽单胞菌门（Gemmatimonadetes）和真菌被孢霉门（Mortierellomycota）的相对丰度。（3）相关性分析结果表明细菌的群落结构主要受微生物量碳含量的影响，真菌的群落结构和多样性分别受转化酶和脲酶活性的影响。在无法保证每年冬灌用水的情况下，隔年冬灌更有利于保障膜下滴灌棉田的土壤耕地质量。     

Snowpack shifts cyanobacterial community in biological soil crusts

Winter snowpack is an important source of moisture that influences the development ofbiological soil crusts(BSCs)in desert ecosystems.Cyanobacteria are important photosynthetic organismsin BSCs.However,the responses of the cyanobacterial community in BSCs to snowpack,snow depth andmelting snow are still unknown.In this study,we investigated the cyanobacterial community compositionand diversity in BSCs under different snow treatments(doubled snow,ambient snow and removed snow)and three snow stages(stage 1,snowpack;stage 2,melting snow;and stage 3,melted snow)in theGurbantunggut Desert in China.In stages 1 and 2,Cyanobacteria were the dominant phylum in the bacterialcommunity in the removed snow treatment,whereas Proteobacteria and Bacteroidetes were abundant inthe bacterial communities in the ambient snow and doubled snow treatments.The relative abundances ofProteobacteria and Bacteroidetes increased with increasing snow depth.The relative abundances ofCyanobacteria and other bacterial taxa were affected mainly by soil temperature and irradiance.In stages 2and 3,the relative abundance of Cyanobacteria increased quickly due to the suitable soil moisture andirradiance conditions.Oscillatoriales,Chroococcales,Nostocales,Synechococcales and unclassifiedCyanobacteria were detected in all the snow treatments,and the most dominant taxa were Oscillatorialesand Chroococcales.Various cyanobacterial taxa showed different responses to snowpack.Soil moisture andirradiance were the two critical factors shaping the cyanobacterial community structure.The snowpackdepth and duration altered the soil surface irradiance,soil moisture and other soil properties,whichconsequently were selected for different cyanobacterial communities.Thus,local microenvironmentalfiltering(niche selection)caused by snow conditions may be a dominant process driving shifts in thecyanobacterial community in BSCs.     

茴香轮作调控土壤细菌群落缓解三七连作障碍的效应及机制

三七是我国特有的中药材，但连作障碍严重制约了其产业发展，轮作是生产上最常用且有效的缓解措施。本研究在三七收获后的土壤上轮作茴香，通过测定轮作土壤水浸液对三七存苗的影响来评价轮作对三七连作障碍的缓解效果，并从轮作对土壤细菌群落的影响方面深入阐释轮作缓解连作障碍的机制。结果表明，茴香轮作后的土壤水浸液可以显著提高三七的存苗率。土壤细菌分析表明，茴香轮作后土壤细菌群落发生了明显改变。细菌的丰富度增加，相对丰度>1%的优势菌门变形菌门Proteobacteria和放线菌门Actinobacteria的相对丰度呈增加趋势。属水平上，轮作茴香使66个属的相对丰度显著增加，其中相对丰度>0.2%的优势菌属有14个；30个属的相对丰度显著降低，其中优势菌属有8个，总体上看相对丰度显著增加的属多于显著降低的属。在相对丰度显著增加的优势菌属中包含常见的拮抗菌属假单胞菌属Pseudomonas和芽孢杆菌属Bacillus细菌。本研究也分离到2株假单胞菌和1株芽孢杆菌对三七根腐病菌腐皮镰刀菌Fusarium solani和Monographella cucumerina具有明显的拮抗活性。因此，轮作茴香可以改善三七连作土壤细菌群落结构，增加土壤中拮抗细菌的丰度，提高三七的存苗率。生产上利用茴香与三七轮作对缓解连作障碍具有一定潜力。     

娃娃菜不同轮作模式下根际土壤微生物群落多样性特征

为探明不同作物与娃娃菜轮作后的效果，在宁夏南部山区进行定位试验，采用高通量测序技术，结合土壤理化性质及酶活性，比较分析了娃娃菜-西兰花(CMB)、娃娃菜-大葱(CMG)、娃娃菜-洋葱(CMO)、娃娃菜-土豆(CMP)和以娃娃菜连作(CCC)为对照的5个处理的微生物多样性，旨在筛选出适宜与娃娃菜轮作的作物，为从栽培模式选择角度缓解或避免娃娃菜连作障碍提供理论依据。试验结果表明：与连作相比，轮作马铃薯土壤硝态氮含量最高为12.8 mg·kg^-1,轮作大葱土壤速效磷含量最高为75.74 mg·kg^-1,但不同轮作模式下速效钾和有机质含量有所下降。轮作马铃薯土壤的碱性磷酸酶、蔗糖酶与轮作洋葱土壤的过氧化氢酶、脲酶显著低于娃娃菜连作和轮作其他作物。细菌丰度在属水平上的结果表明轮作导致大部分有益细菌属丰度升高，如贪铜菌属(Cupriavidus)、鞘脂单胞菌属(Sphingomonas)、柄杆菌属(Caulobacter)等，有害菌及其他部分未分类功能作用菌属丰度降低，如伯克氏菌(Burkholderiaceae)、黄杆菌属(Flavobacterium...     

桑树青枯病与根际土壤肥力及微生物群落结构特征的研究

本文比较分析了桑树青枯病发病和健康植株根际土壤肥力以及微生物（细菌和真菌）群落结构特征差异，旨在挖掘和利用丰富微生物资源的有益功能，为构建桑树青枯病生物防治技术体系奠定基础。结果表明，桑树青枯病发病植株根际土壤中指示土壤肥力与健康状况的生物学性状指标β-葡糖苷酶和磷酸酶的活性显著降低，微生物生物量碳、磷显著下降；细菌门分类水平上，发病植株根际土壤中酸杆菌门、放线菌门和疣微菌门等优势细菌相对丰度降低，变形菌门、绿弯菌门、粘球菌门、厚壁菌门、拟杆菌门等优势细菌相对丰度增加；细菌属分类水平上，发病植株根际土壤富集了硝化螺菌属和放线菌属等特有细菌属，缺失了诸如链霉菌属等具有分泌抗生素功能的优势细菌属。真菌门分类水平上，发病植株根际土壤中子囊菌门和担子菌门真菌相对丰度增加，unclassified_k_Fungi和霉菌门真菌相对丰度降低；真菌属分类水平上，发病植株根际土壤富集了地霉菌属、腐质霉属和丝孢菌属等腐生真菌，缺失了被孢霉属、枝顶孢属和曲霉属等具有产抑菌化合物功能的优势真菌。研究表明，桑树青枯病与根际土壤β-葡糖苷酶、磷酸酶活性，微生物生物量碳、磷以及微生物群落结构都具有一定的相关性。链霉菌属细菌以及被孢霉属、枝顶孢属和曲霉属真菌有望作为生物防控青枯病的有效备选菌属。     

连续施用不同氮量对半干旱地区马铃薯根际真菌群落结构的影响

针对马铃薯生产中因氮肥过量施用导致的土壤微生物群落结构失衡和多样性下降等问题,在始于2013年的不同氮肥用量(N0:不施氮,对照;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);N375:施氮量375 kg·hm~(-2))田间定位试验中,于2017年马铃薯成熟期采集根际土壤,应用Illumina PE250测序等分子生物学手段,研究连续5 a施用不同氮量对半干旱地区马铃薯根际真菌群落结构的影响。结果表明:不同施氮量对马铃薯根际真菌群落物种组成造成了显著影响,子囊菌门、Mucoromycota和担子菌门是3个优势门类真菌(相对丰度1.0%),以子囊菌门的相对丰度最大,占总序列的75.48%～83.95%,其优势属是Plectosphaerella(29.92%)和镰刀菌属(13.54%);马铃薯干腐病和枯萎病的病原菌——镰刀菌属的相对丰度随施氮量增加呈增大的趋势。马铃薯根际真菌Alpha多样性随施氮量的增加而降低。连续5 a超量施氮导致了0～20 cm表层土壤中NO~-_3-N含量显著增加,N375处理的NO~-_3-N含量是N0处理的3.76倍。连续5 a超量施氮也显著降低了根际pH值和速效磷含量,N375处理比N0处理pH值和速效磷含量分别降低了0.17个单位和32.10%。RDA及相关性分析结果表明,土壤硝态氮含量是影响马铃薯根际真菌群落结构变化的主要因素(F=1.571,P=0.043~*)。连续大量施用氮肥显著降低了马铃薯块茎产量,连续施氮5 a后,由于土壤剖面中NO~-_3-N的积累,最高产量施肥量由2013—2014年的N225减低为N75,其它施氮处理较N75分别减产了3.46%、22.81%、26.05%和25.32%。长期过量施用氮肥使马铃薯根际硝态氮大量累积,导致pH值降低,进而使根际真菌多样性降低;同时过量氮肥施用会使根际中土壤真菌病原菌相对丰度增加,不利于土壤的健康和马铃薯的高产。     

红砂植被盖度对土壤不同形态碳、氮及细菌多样性的影响

以自然恢复的红砂群落为研究对象,探讨黄土高原红砂植被不同盖度对土壤不同形态碳、氮及细菌多样性的影响,为该地区的人工生态恢复措施提供理论支撑.在兰州市南北两山植被恢复技术研究与示范基地,按照5级盖度分类法设置红砂植被盖度梯度,重点对土壤养分碳氮、微生物量碳氮和细菌多样性开展研究.结果表明:随着植被恢复,土壤有机碳 (SOC)和全氮(TN)、土壤微生物碳 (MBC)和微生物氮(MBN)逐渐提高,并且增加比较快 ,但是当总盖度达到48.73%之后,增加比较缓慢,而且增加的差异不显著.相同的植被盖度对土壤有机碳、全氮和土壤微生物碳、氮的影响趋于一致.土壤细菌多样性随植被盖度有所增加,在植被盖度达到48.73%后多样性维持在彼此接近的水平,尽管微生物多样性群落结构有差异 .在植被稀疏、物种多样性较低的干旱坡地,红砂植被盖度增加明显改善了土壤生态功能, 但是片面追求植被盖度的增加,对土壤特性改善有限.     

黄连根腐病发生与根际土壤、根茎内生、叶内生细菌群落结构变化关系

为了探讨细菌群落结构与黄连根腐病发生的关系,本文分析了两个不同地点健康和染病黄连的根茎、叶内生细菌和根际土壤细菌的组成和差异。结果显示,黄连根茎、叶片和根际土壤样品中根际土壤细菌群落多样性最丰富,根茎内生菌次之。在所有样品中,主要的优势菌门为变形菌门Proteobacteria、放线菌门Actinobacteria、拟杆菌门Bacteroidetes和绿弯菌门Chloroflexi。相较于健康黄连组样品,染病黄连根际土壤、根茎和叶片样品中多个菌属细菌相对丰度发生显著改变,如Vibrionimonas,乳杆菌属Lactobacillus和鞘氨醇单胞菌属Sphingomonas等,表明可能与黄连根腐病的发生有一定关联。此外,RDA分析表明,伯克氏菌属Burkholderia、全噬菌属Holophaga和雷尔氏菌属Ralstonia与黄连根际土壤有机质、有效氮、pH有显著相关性。本研究分析了两个不同地点的健康和染病黄连根际、叶片内生细菌和根际土壤细菌群落结构差异,为综合分析黄连根腐病的成因和机制提供了参考。     

Plantations of native shrub species restore soil microbial diversity in the Horqin Sandy Land,northeastern China

Caragana microphylla Lam., a leguminous shrub species, plays an important role in revegetation in the degraded ecosystems of the Horqin Sandy Land, Northeastern China. Large areas planted with this shrub have been artificially established as sand binders for soil protection, which might change the composition of soil bacterial communities with the development of sand dune stabilization. In this paper, we investigated the diversity and composition of native soil bacterial communities in the C. microphylla plantation for sand fixation using polymerase chain reaction with denaturing gradient gel electrophoresis（PCR-DGGE） to understand the influence of this plantation on sandy soil ecosystem development. We collected soil samples from plantations with an age sequence of 0, 9, 16, and 26 years, as well as from the natural community, to identify the differences among soil bacterial communities. The result showed that bacterial abundance and community composition in the sandy land were affected by the age of the C. microphylla plantation. Moreover, bacterial diversity decreased with increasing plantation age, and the composition of the bacterial community in the 26-year plantation was similar to that in the natural community. Phylogenetic analysis of bands excised from the DGGE gels showed that members of alpha Proteobacterium, gamma Proteobacterium, Gemmatimonadetes and Chloroflexi were dominant in the sandy land. The stabilization of moving sand dune and development of sand-fixed plantation resulted in an increase of soil fertility, which could drive the structural evolvement of soil bacterial community, and it needs over 20 years for the soil bacterial community to form a stable structure, similar to the case for the natural vegetation.     

新疆吉木萨尔县林场大、中型土壤动物群落组成及季节动态研究

为探讨山地生态系统不同生境对大、中型土壤动物群落结构特征的影响,分别于2009年4月、7月及9月对天山北麓中段吉木萨尔县林场山地生态系统的5种不同生境,即云杉林、山前草甸、山地草原、山地农田及山间河滩中的大、中型土壤动物群落进行了采样研究。共捕获大、中型土壤动物个体14727只,分别隶属于6门16纲39目(40类)。其中弹尾目和真螨目为优势类群,二者分别占总数的38.61%,25.54%。鞘翅目、寄螨目、膜翅目、蜘蛛目、鞘翅目幼虫、双翅目幼虫、颤蚓目、鳞翅目幼虫等8类为常见类群,共占总数的26.38%,优势类群和常见类群共占总数是的90.53%,这二类组成了该区大、中型土壤动物的基本成分。其余的30类为稀有类群,占总数的9.47%。研究还发现,山地不同生境大、中型土壤动物类群和个体数之间、不同季节之间、不同土层之间以及群落多样性之间均存在显著差异(P>0.05)。通过该区不同生境大、中型土壤动物群落的聚类和排序结果,将5种不同山地生境分为云杉林-山地草原生境类型和山前草甸-山地耕地-山间河滩生境类型两大类型。     

基于宏基因组测序解析长刺蒺藜草入侵对根际土壤氮循环的影响

为揭示外来入侵植物长刺蒺藜草 Cenchrus longispinus对氮素高效利用的微生态机制,利用宏基因组测序技术分析长刺蒺藜草、狗尾草 Setaria viridis、披碱草 Elymus dahuricus三种杂草根际土壤及对照中参与氮循环的微生物类群及功能基因差异。结果显示,长刺蒺藜草入侵显著增加了根际土壤中全氮和硝态氮含量,显著降低了土壤水溶性氮含量;长刺蒺藜草根际土壤中链霉菌属Streptomyces、红色杆菌属 Rubrobacter、硝化螺旋菌属 Nitrospira及类诺卡氏菌属 Nocardioides微生物丰度与其他3个处理之间差异显著,并与根际土壤中硝态氮含量显著相关;长刺蒺藜草根际土壤中微生物的氮代谢功能基因nasB和nifK丰度与对照之间差异显著,且与根际土壤中硝态氮含量显著相关。推测长刺蒺藜草入侵通过增加根际土壤中链霉菌属、红色杆菌属和类诺卡氏菌属微生物丰度影响根际土壤的氮代谢过程,通过减少 nasA基因丰度降低硝酸盐同化速率,其根际土壤有少量nifK固氮基因,表明其有一定的固氮能力。     

荒漠草原不同植被类型土壤微生物群落功能多样性

利用Biolog EcoplateTM技术通过对荒漠草原生态系统中沙米、白沙蒿、柠条、沙冬青和人工乔木林5种植被类型土壤微生物群落功能多样性分析,以探讨不同植被类型对土壤微生物群落代谢功能多样性的影响.结果表明,5种植被类型土壤微生物群落代谢活性有显著的差异(P＜0.01),5种植被类型土壤微生物群落利用碳源的种类也存在差异,氨基酸类、羧酸类和糖类是其主要的碳源利用类型.在Biolog ECO板培养基接种培养96 h后,5种植被类型土壤微生物群落多样性显示,物种丰富度指数(R)和均匀度指数(EH)差异显著,Shannon 指数(H′)差异不显著.     

不同连作年限硒砂瓜土壤细菌群落结构特征

应用高通量测序技术对宁夏中卫地区不同连作年限硒砂瓜土壤细菌群落结构和多样性进行研究,旨在揭示不同连作年限对硒砂瓜土壤细菌群落结构的影响。结果表明:随着连作时间的增加,细菌多样性指数和丰富度指数逐渐增加。从5份不同连作年限硒砂瓜土壤样本中共获得39门、98纲和620属的细菌;优势门为放线菌门(Actinobacteria)、变形菌门(Proteobacteria)、绿弯菌门(Chloroflexi)、酸杆菌门(Acidobacteria);随着连作时间的增加,放线菌门、酸酐菌门丰度先增加后降低,变形菌门丰度逐渐降低,绿弯菌门丰度呈先降低后增加又降低现象;优势纲分别为放线菌纲(Actinobacteria)、酸杆菌纲(Acidobacteria)、α-变形菌纲(Alphaproteobacteria)、芽单胞菌纲(Gmmatimonadetes)、杆菌纲(Bacilli)、热原体纲(Themomicrobia)、γ-变形菌纲(Gammaproteobacteria)、β-变形菌纲(Betaproteobacteria);优势目为norank_c_Acidobacteria、芽孢杆菌目(Bacillales)、芽单胞菌目(Gemmatimonadales)、根瘤菌目(Rhizobiales)。RDA分析表明,有机质、速效磷是硒砂瓜连作土壤细菌群落组成的主要影响因子。研究表明,引起硒砂瓜连作障碍发生主要因素不是由于土壤理化性质变化引起的,而是随着连作时间的增加,放线菌门、变形菌门、绿弯菌门、酸杆菌门、厚壁菌门等有益微生物丰度下降造成的。