重金属复合污染对水稻土微生物生物量和群落结构的影响

以浙江富阳小冶炼厂附近水稻土为例,采用氯仿熏蒸法、稀释平板培养法和磷脂脂肪酸(PLFA)技术研究了重金属复合污染对水稻土微生物生物量和群落结构的影响。结果表明,自然状态下铜、锌、镉、铅复合污染降低了土壤微生物量。土壤微生物群落结构对重金属复合污染产生了响应,约41.82%的土壤微生物群落结构的改变可由重金属污染来解释。污染程度高的土壤中,含脂肪酸12∶0,i15∶0,i17∶0,18∶0,i16∶0,19∶0相对较高的微生物占优势,而在污染程度低的土壤中,含脂肪酸20∶2ω6,9 c,20∶0,16∶1ω9 c,a15∶0,a16∶0,18∶1ω7,10M e16∶0,10M e19∶0的相对含量较高的微生物占优势。反映在具体类群上,随着污染程度的增加,微生物向着Cm ic/Nm ic低、真菌相对含量增加,放线菌与革兰氏阴性菌含量相对减少的趋势发展。     

潮土长期雨养对土壤酶活性和微生物功能多样性影响

随着华北地区水资源持续短缺,雨养农业可能是当地粮食生产的趋势之一,因而明确雨养农业对土壤质量影响将为预估作物产量变化提供基础。本研究以河南省封丘县潮土4种不同利用类型的土壤为平台,探讨长期雨养农地(雨养地)和传统灌溉农地(传统地)上土壤酶活性和微生物功能多样性的差异,并将其与邻近荒地和林地进行比较。除脱氢酶活性为雨养地比传统地低24%外,蔗糖酶、脲酶及碱性磷酸酶活性在雨养地和传统地间均相当,但比林地和荒地高36%~149%;基于Biolog分析的参数,包括平均吸光值(AWCD)及功能多样性指数,在不同处理间没有显著性差异,但主成分分析发现雨养地的碳源利用能力与传统地和林地比较接近,而与荒地相差较大,主要表现在利用羧酸类和氨基酸类物质的不同上,这可能与荒地较高p H及雨养地、传统地、林地根系有可能分泌羧酸类和氨基酸类物质有关。本研究结果表示,在潮土上即使经过连续16年的雨养农业后,土壤酶活性和微生物功能多样性的变化很小,结果从土壤质量变化角度预示在当地实行雨养农业的可能性。     

不同气候条件下潮土微生物群落的变化

针对气候变化的背景研究农田土壤微生物对气候变化的响应机制是调控农田土壤养分循环的理论基础。本研究基于设置在3个气候带(冷温带海伦、暖温带封丘和中亚热带鹰潭)的潮土移置试验,利用磷脂脂肪酸(PLFA)分析方法研究了移置第6年土壤微生物群落的变化特征。结果表明,在3种气候条件下潮土移置6年后土壤部分理化性质显著变化,土壤有机质含量表现为冷温带最高而中亚热带最低;在种植玉米的不同施肥处理中,土壤中微生物总PLFAs、革兰氏阳性细菌(G+)、革兰氏阴性细菌(G-)、细菌和放线菌PLFAs含量均表现为海伦封丘鹰潭,真菌/细菌比值在冷温带最低;PLFA图谱的主成分分析显示气候条件显著影响了土壤微生物的群落结构,海伦和封丘位于PC1正轴,而鹰潭位于负轴,受气候影响较大的特征PLFA包括18:1ω7c、16:1ω5c、16:0、18:0和18:2ω6,9c;逐步回归分析显示温度、降雨和土壤有机质是影响微生物群落的主要因子。总体上,气候条件的变化在短期内(6年)改变了土壤微生物的群落结构,可以影响农田生态系统的生物地球化学循环。     

土壤微生物群落结构对凋落物组成变化的响应

凋落物分解是陆地生态系统养分循环的关键过程,明确凋落物多样性如何影响土壤微生物群落构成和多度,继而潜在地改变凋落物分解的微生物学机制有助于认识生物多样性和森林生态系统功能的关系。通过小盆模拟试验,应用磷脂脂肪酸谱图的方法研究了我国南方红壤丘陵区典型物种马尾松和湿地松的凋落物分别与白栎和青冈的凋落物混合,与单一针叶凋落物分解时相比,针阔混合凋落物分解过程中土壤微生物群落结构的变化,结果显示:(1)针阔混合凋落物分解时土壤微生物群落磷脂脂肪酸(Phospholipidfatty acids,PLFA)总量低于单一针叶处理,细菌和放线菌的相对多度高于单一针叶处理,真菌则相反,群落真菌/细菌低于单一针叶处理,土壤微生物生物量的差异主要来自于真菌;(2)主成分分析表明:针阔混合凋落物分解与单一针叶凋落物分解的土壤微生物群落结构差异显著,两个时期(分解9个月和18个月)主成分一分别可以解释65.74%和89.63%的变异,第一主成分主要包括18∶2ω6,9、18∶1ω9c、17∶0和10Me18∶0等磷脂脂肪酸;(3)土壤微生物群落结构受凋落物初始C/N和木质素/N调控,土壤微生物群落细菌的相对多度与凋落物初始C/N和木质素/N显著负相关,真菌则与凋落物初始C/N和木质素/N显著正相关,群落真菌/细菌与凋落物初始C/N和木质素/N显著正相关。针阔凋落物混合分解通过改变凋落物C/N和木质素/N,提供了对分解者更为有利的微环境。     

地膜覆盖对土壤微生物群落结构的影响

采用磷脂脂肪酸(PLFA)法测定了沈阳农业大学棕壤长期定位试验站地膜覆盖条件下土壤微生物磷脂脂肪酸图谱及群落结构。结果表明:在玉米苗期,长期施氮肥处理土壤覆膜后大部分脂肪酸含量都有所提高;施有机肥处理的土壤覆膜后脂肪酸的含量有降低的趋势;有机无机肥配合施用处理的土壤覆膜会增加真菌的含量,但却降低了其他脂肪酸的含量;在不施肥处理的土壤中,覆膜会使一些支链脂肪酸的含量降低。抽雄期,施有机肥的土壤覆膜后除单饱和脂肪酸含量有所下降外,其他脂肪酸都会提高;不施肥土壤覆膜处理双不饱和支链脂肪酸及放线菌标志性脂肪酸10Me18:0的含量会有所提高。成熟期,施氮肥的土壤覆膜处理大部分脂肪酸的含量降低;有机肥处理土壤中各种脂肪酸如:15∶0,a17∶0,i17∶0,i19∶0,18∶0,10Me18∶0含量覆膜高于裸地;有机无机配施处理土壤中17∶0,br17∶0,18∶0,18∶2w6,10Me18∶0含量覆膜处理高于裸地;对照土壤中i15∶0,16∶0,17∶0,a17∶0,18∶0,18∶2w6,19∶0含量覆膜高于裸地。另外,从脂肪酸的变化看出,覆膜处理土壤微生物群落整体结构发生了改变,没有表现出明显的种群优势。但是,尽管土壤的施肥处理不同,覆膜处理土壤微生物群落结构有一致化发展的趋势。     

野生黄花蒿土壤的养分状况与微生物特征

黄花蒿是提取青蒿素的唯一原料植物,广泛分布于我国西南地区。为探索野生黄花蒿的耐瘠机理,提高人工种植黄花蒿的产量品质,研究了野生黄花蒿土壤的养分状况与微生物特性,以及它们与黄花蒿产量品质的关系。结果表明,在野生黄花蒿生长的不同样地中,土壤养分、pH、酶活性和微生物量差异显著,说明黄花蒿耐瘠耐肥,具有广泛的生态适应性。利用气相色谱-质谱联用仪共检测出24种土壤微生物标记性磷脂脂肪酸(PLFAs),包括代表细菌的19种11～19碳PLFAs,代表放线菌的10Me18∶0,代表真菌的18∶2ω6,9、18∶1ω9c和18∶1ω9t,以及代表线虫的20∶0,PLFAs总含量均表现出细菌放线菌真菌的现象。在黄花蒿根际土壤中,pH显著低于非根际土壤,但有机质、碱解氮、有效磷、速效钾,蔗糖酶、脲酶和磷酸酶活性,微生物碳氮量,PLFAs总含量,微生物群落的多样性和均匀度指数等显著高于非根际土壤。此外,在野生黄花蒿根际土壤中,微生物PLFAs总含量与黄花蒿植株生物量、青蒿酸和青蒿素产量呈极显著正相关,微生物生物量碳氮与青蒿酸和青蒿素产量呈显著或极显著正相关。说明黄花蒿根际土壤适合多种微生物生长繁殖,种群丰富,密度高,酶活性强,提高了土壤养分的有效性,有益于野生黄花蒿适应不同的土壤条件,根际土壤微生物显著影响野生黄花蒿生长及其有效成分的含量。     

放牧与围栏内蒙古针茅草原土壤微生物生物量碳、氮变化及微生物群落结构PLFA分析

以内蒙古贝加尔针茅草原、大针茅草原和克氏针茅草原为研究对象,采用氯仿熏蒸法和磷脂脂肪酸（PLFA）分析方法研究了放牧与围栏条件下内蒙古针茅草原土壤微生物生物量和群落结构特征的变化情况。研究表明放牧与围栏草地土壤微生物生物量和群落结构差异显著。氯仿熏蒸法分析结果表明内蒙古针茅草原土壤微生物生物量碳的含量介于166.6-703.5mg·kg^-1之间,微生物生物量氮含量介于30.34-92.15mg·kg^-1之间,其中贝加尔针茅草原土壤微生物生物量碳、氮最高,大针茅草原次之,克氏针茅草原则最低。放牧条件下,贝加尔针茅草原、大针茅草原土壤微生物生物量碳、氮显著低于围栏草地,克氏针茅草原则无显著变化。PLFA分析结果显示,内蒙古针茅草原土壤微生物群落PLFAs种类、含量丰富,共检测出28种PLFA生物标记磷脂脂肪酸,并且以直链饱和脂肪酸和支链饱和脂肪酸为主,相对含量占总量的2/3左右,其中贝加尔针茅草原土壤微生物含量最丰富,其围栏样地土壤的PLFA含量达到27.3nmol·g-1,大针茅草原和克氏针茅草原依次降低。围栏条件下,各类型草原土壤细菌脂肪酸与总PLFA含量均显著高于放牧草地,真菌脂肪酸含量则因草原类型不同各有差异;放牧导致各类型草原革兰氏阳性细菌PLFAs/革兰氏阴性细菌PLFAs（GPPLFAs/GNPLFAs）比值显著降低,而除了克氏针茅草原,细菌PLFAs/真菌PLFAs比值则显著升高。PLFAs主成分分析表明,放牧和围栏处理对内蒙古针茅草原土壤微生物群落结构产生影响,且围栏处理的影响程度大于放牧处理。经相关分析表明,氯仿熏蒸法和PLFA分析方法之间有很好的一致性,且土壤微生物PLFAs与土壤有机质、全磷、硝态氮显著相关。     

复垦煤矸山不同利用类型土壤微生物群落分析

土壤微生物是表征土壤质量状况的重要指标,因此研究其群落特征对指导煤矸山植被恢复具有重要意义。以山西霍州曹村矿煤矸山为对象,分析了农田(WL)、果园(PO)和草地(GL)3种土地利用类型0~10 cm和10~20 cm土层土壤微生物群落结构。结果表明:(1)3种复垦样地土壤微生物总数、微生物总浓度和微生物群落浓度均低于普通农田(CK),表明该煤矸山复垦地土壤质量状况仍未达到与普通农田相当的水平。(2)从土壤微生物群落结构看,3种土地利用类型中革兰氏阳性菌、细菌和放线菌所占比例无显著差异,而革兰氏阴性菌和真菌占比有显著变化。(3)在3种样地中,WL和PO样地中的优势菌种均为细菌16∶0、真菌18∶1 w9c和革兰氏阳性菌i15∶0、a15∶0;而GL样地中的优势菌种为细菌16∶0、真菌18∶1 w9c和革兰氏阳性菌i15∶0。     

东祁连山高寒草地土壤微生物三大类群的时空动态特征

通过对2005年和2006年东祁连山高寒草地4种不同草地类型(珠芽蓼草地、禾草草地、沼泽草地、嵩草草地)土壤3大类群微生物(真菌、细菌、放线菌)数量的时空动态进行研究。结果表明:(1)不同空间层次草地土壤3大类群微生物数量变化均较大,0-10 cm土层的数量为10-20 cm土层的1.02~3.89倍;(2)不同植被下土壤3大类微生物数量季节变化各有其自身的特点,年际变化也不一致;(3)不同植被下同一时间草地土壤三大类群微生物总数量差异较大,为0.83×107~4.71×107个/g;(4)三大类微生物中,细菌数量最大,放线菌次之,真菌最小,分别占微生物总数的48.9%~67.69%,32.18%~48.96%和0.08%~0.25%。     

磷脂脂肪酸法分析地黄根际土壤微生物多样性

应用磷脂脂肪酸法(PLFA)分析了1年生、2年生和5年轮作地黄根际土壤微生物群落多样性.研究发现,地黄连作障碍在2年生和5年轮作田均发生,表现为病虫害严重,根系生长不良,根际土壤微生物基础呼吸、代谢商高于对照等,说明地黄根际生态系统的代谢能力降低,可能影响到能量循环过程.应用主成分分析法从33个PLFAs中提取出3个主成分,代表72.55%的变异信息,其中PCI解释了48.91%的变异,PC2解释了14.16%的变异,PC3解释了9.48%的变异,而且从主成分得分图上可以很明显区分根际和非根际土壤.另外还发现地黄根际真菌标志磷脂C18:2ω6,9显著高于非根际的对照土壤,这可能和根际病害发生有关.     

两种施肥处理下不同有机质含量农田黑土微生物群落结构PLFA分析

土壤有机质含量和施肥是影响黑土微生物群落结构的重要因素,但是受气候影响,很难单独明确有机质含量或施肥对土壤微生物群落的影响。本研究利用黑土生产力长期定位试验,将有机质含量不同的5个黑土(SOM1.7、SOM3、SOM5、SOM6、SOM11)置于相同气候条件下,通过分析磷脂脂肪酸,系统地研究了施肥与有机质含量对农田黑土微生物群落结构的影响。研究结果表明,5个有机质含量农田黑土中,土壤磷脂脂肪酸总量为10.6~31.5 nmol·g^-1,细菌磷脂脂肪酸含量为6.23~18.4 nmol·g^-1,真菌磷脂脂肪酸总量为1.78~4.57 nmol·g^-1。土壤有机质含量升高和施肥会显著提高土壤中总微生物量、细菌生物量和真菌生物量,但施肥和有机质含量对真菌/细菌比值无显著影响。非度量多维尺度分析(NMDS)分析表明,有机质含量和施肥是导致微生物群落结构差异的重要因素,但施肥可能会遮蔽有机质含量对微生物群落的影响。     

INTRODUCED EUCALYPTUS UROPHYLLA PLANTATIONS CHANGE THE COMPOSITION OF THE SOIL MICROBIAL COMMUNITY IN SUBTROPICAL CHINA

Fast‐growing tree species are widely used as pioneers for reforestation. These plantations strongly affect the ecosystem productivity and nutrient cycling, whereas their effect on the soil microbial community is still unclear. In a reforestation chronosequence in subtropical China consisting of Eucalyptus plantation with ages of 1, 2, 4 or 5 years, we examined the response of the soil microbial community and its function. The results showed that soil bulk density and dissolved organic carbon decreased significantly along the chronosequence. Soil pH was highest in the 5‐year‐old plantation. The amount of bacterial phospholipid fatty acids (PLFAs) and arbuscular mycorrhizal fungal PLFAs increased, but the ratio of fungal‐to‐bacterial PLFAs decreased with increasing forest age. The composition of the soil microbial community obviously changed after 5 years' development. Redundancy analysis showed that dissolved organic carbon was the major factor associated with the changes of soil microbial community composition. The short‐rotation Eucalyptus plantation could affect the composition of soil microbial communities through changing soil available carbon when planted in subtropical region at the early developmental stage. We suggest that soil microbial community composition should be taken into consideration in the large‐scale reforestation activities. Copyright © 2012 John Wiley & Sons, Ltd.     

绿肥与化肥配施对植烟土壤微生物群落的影响

土壤微生物群落被认为是土壤生态系统变化的预警及敏感指标,指示着土壤质量的变化。本研究利用 3 年定位试验,通过测定磷脂脂肪酸(PLFAs)的含量,分析了连年绿肥和化肥配施对植烟土壤微生物群落结构的影响。研究结果表明：施肥明显地提高了土壤中 PLFAs 的种类和总量;在绿肥和化肥配施处理中,当翻压 15 000 kg/hm2 绿肥的基础上施用大于 85% 常规化肥时,明显提高了土壤中细菌、AM 真菌及微生物总的 PLFAs 含量;而当化肥的施用量减至常规施肥 70% 时,对土壤细菌、真菌及微生物总 PLFAs 含量的积累产生不利影响。从不同处理的主成分分析和聚类分析的结果可知,不同绿肥和化肥配施比例对土壤微生物群落结构变化有明显影响。经相关性分析表明,PLFA 分析方法和氯仿熏蒸法之间具有很好的一致性,且土壤速效钾和速效磷含量与革兰氏阴性菌的 PLFAs 含量呈显著相关,而与土壤真菌PLFAs 含量则无明显的相关性。     

Influences of past application rates of nitrogen and a catch crop on soil microbial communities between an intensive rotation

The aim of this study was to investigate influences of six-year past application rates of nitrogen and a catch crop, sweet corn (Zea mays L. ssp. Saccharata Sturt), on soil microbial community and diversity in a greenhouse-based intensive vegetable soil in eastern China. Soil electrical conductivity, pH, mineral nitrogen, phospholipid fatty acids (PLFA) profiles and carbon source utilization patterns under five annually past nitrogen rates (0, 348, 522, 696 and 870?kg?nitrogen?ha^?1) were evaluated after the establishment of sweet corn during 1–1.5-month fallow period over three-year tomato/cucumber/celery rotations. The past nitrogen application rates exerted significant effects on soil electrical conductivity, pH, nitrate-nitrogen, ammonium-nitrogen and carbon source utilization patterns, but not on PLFAs profiles. The sweet corn had a significant effect on soil chemical properties, total and actinobacterial PLFAs, but not on carbon source utilization patterns. Soil electrical conductivity, nitrate-nitrogen and the total PLFAs decreased whilst soil organic carbon, pH and the actinobacterial PLFAs increased after the establishment of sweet corn. Soil microbial functional diversity from carbon source utilization patterns and actinobacterial PLFAs were greatest after the establishment of sweet corn at a 60% of the conventional nitrogen rate (i.e. 522?kg?nitrogen?ha^?1). Soil electrical conductivity and ammonium-nitrogen were two key factors to determine carbon source utilization patterns, whilst soil pH was the key factor to determine PLFAs profiles. A combination of the catch crop sweet corn during summer fallow and a 60% of the conventional nitrogen rate is a sustainable pathway of utilizing greenhouse-based intensive vegetable soils in eastern China.     

Dynamics of Microbial Community in Japanese Andisol of Apple Orchard Production Systems

Abstract

In this study, two fields of temperate Andisols from high‐input and low‐input (zero‐input) management practices of an apple orchard were selected to assess microbial community dynamics based on environmental variables. Soils from an Ap horizon were sampled in five consecutive months from May to September and assessed for phospholipid fatty acids as a biomarker of soil microbial community, soil hardness, bulk density, porosity, pH, electrical conductivity (EC), organic carbon (C), available nitrogen (N) and phosphorus (P), and exchangeable cations as soil environmental variables. For all sample dates, total phospholipid fatty acids (PLFAs), total bacterial PLFAs, fungal PLFA, mycorrhizal PLFA, PLFA for actinomycetes, and earthworm were higher in low‐input management than high‐input management. Total PLFAs showed a high degree of seasonality, having August maxima and May minima. Significant effect on the relationships among soil environmental variables and microbiological attributes were observed. Soil management practices also showed a remarkable effect on the relationships among microbiological traits, indicating that some mechanism regulated soil microbial dynamics under two soil management practices. Comparatively higher correlations among the microbiological attributes were observed in low‐input management than high‐input management. Irrespective of soil management practices, bacterial and fungal lipid biomarkers were negatively correlated, suggesting that these subsets of fatty acids are contrasting components of the microbial biomass. Bulk density has negative influence on all soil microbial communities except fungi. On the other hand, linoleic acid and organic C were positively correlated, referring to the distribution of soil organic C implying an upper layer of soils. Microbial community composition and structure were greatly affected by sampling date and to a lesser extent by long‐term management practice. In this study, both ecosystems were characterized by a very diverse microbial community.     

磷脂脂肪酸分析方法及其在土壤微生物多样性研究中的应用

磷脂脂肪酸（PLFA）是活体微生物细胞膜的重要组分，不同类群的微生物可通过不同的生化途径合成不同的PLFA。一些PLFA可作为分析微生物量和微生物群落结构变化的“生物标记”。在土壤微生物分析中，越来越多地采用了PLFA方法。本文介绍了表征微生物的一些PLFA、从土壤中提取PLFA的方法以及用GC-MS分析PLFA的原理。本文还将常用的研究微生物多样性的几种方法进行了比较；传统的分析土壤微生物群落的方法依赖于培养技术，只能培养和分离出一小部分微生物群落；Biolog方法可用于研究土壤微生物群落生理多样性，即可反映微生物群落如何利用各种碳源底物，但对快速生长和适合在Biolog实验条件下生长的小部分群落成员有强烈的选择性；核酸分析方法的主要缺点是不能对土壤微生物进行定量分析；而PLFA方法相对于上述几种方法有诸多优势。本文通过一些实例证明PLFA方法的特色或独到之处，也分析了其缺点。采用PLFA方法并结合其他方法有助于获取土壤微生物群落多样性的更多和更全面而完整的信息。     

Temperature and substrate controls on microbial phospholipid fatty acid composition during incubation of grassland soils contrasting in organic matter quality

Soil incubations are often used to investigate soil organic matter (SOM) decomposition and its response to increased temperature, but changes in the activity and community composition of the decomposers have rarely been included. As part of an integrated investigation into the responses of SOM components in laboratory incubations at elevated temperatures, fungal and bacterial phospholipid fatty acids (PLFAs) were measured in two grassland soils contrasting in SOM quality (i.e. SOM composition), and changes in the microbial biomass and community composition were monitored. Whilst easily-degradable SOM and necromass released from soil preparation may have fuelled microbial activity at the start of the incubation, the overall activity and biomass of soil microorganisms were relatively constant during the subsequent one-year soil incubation, as indicated by the abundance of soil PLFAs, microbial respiration rate (r), and metabolic quotient (qCO₂). PLFAs relating to fungi and Gram-negative bacteria declined relative to Gram-positive bacteria in soils incubated at higher temperatures, presumably due to their vulnerability to disturbance and substrate constraints induced by faster exhaustion of available nutrient sources at higher temperatures. A linear correlation was found between incubation temperatures and the microbial stress ratios of cyclopropane PLFA-to-monoenoic precursor (cy17:0/16:1ω7c and cy19:0/18:1ω7c) and monoenoic-to-saturated PLFAs (mono/sat), as a combined effect of temperature and temperature-induced substrate constraints. The microbial PLFA decay patterns and ratios suggest that SOM quality intimately controls microbial responses to global warming.     

Soil fertility,enzyme activity,and microbial community structure diversity among different soil textures under different land use types in coastal saline soil

Purpose

This investigation assessed the responses of soil fertility, enzyme activity, and microbial community diversity to soil texture and land use type.

Materials and methods

The tested soils included five soil textures (sandy loam, medium loam, heavy loam, light clay, and medium clay soils) with two land use types (uncultivated and paddy soils) in the coastal zone of Zhejiang Province, China.

Results and discussion

Soil texture had a significant effect on soil pH, electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), available nitrogen (AN), phosphorus (AP) and potassium (AK), catalase and protease activities, total phospholipid fatty acids (PLFAs), bacterial and actinomycetes PLFAs, and microbial diversity (MD). The clay content was significantly positively correlated to soil EC, OC, TN, AN, AP, AK, catalase activity, total PLFAs, bacterial and actinomycetes PLFAs, and MD but significantly negatively associated with soil pH and protease activity. Land use type also had significantly influenced soil pH, EC, OC, TN, AN, AP, AK, catalase, protease and urease activities, total PLFAs, bacterial, actinomycetes, and fungal PLFAs, and MD. The paddy soil had higher OC, TN, AN, AP, catalase, protease and urease activities, total PLFAs, bacterial and actinomycetes PLFAs, and MD but lower soil pH, EC, and AK than the uncultivated soil. The interaction with soil texture and land use type had significantly affected soil pH, EC, OC, TN, AN, AP, AK, catalase and protease activities, total PLFAs, bacterial and actinomycetes PLFAs, and MD.

Conclusions

Soil texture and land use type could be considered important factors in improving soil fertility, enzyme activity, and microbial diversity in coastal saline soils.

     

PLFA方法研究连作对加工番茄根际土壤微生物群落结构的影响

通过在石河子大学农学院试验站开展加工番茄连作定点微区试验,采用氯仿熏蒸和磷脂脂肪酸(PLFA)法相结合,研究了不同连作处理(种植1 a、连作3 a、5 a和7 a)对新疆加工番茄花果期和成熟期根际土壤微生物群落结构及土壤微生物量的影响。结果表明,连作导致土壤微生物量碳(SMBC)、微生物量氮(SMBN)和微生物熵(q MB)下降,SMBC/SMBN升高,而微生物量磷(SMBP)随连作年限和生育期的变化而不同。连作显著增加了真菌PLFAs含量,降低了细菌PLFAs含量、土壤PLFAs总量及细菌/真菌PLFAs的比值,而放线菌PLFAs含量变化无规律。连作7 a时,成熟期的细菌PLFAs含量、土壤PLFAs总量较对照分别减少62.9%、50.3%(P0.05),而真菌PLFAs含量较对照升高60.2%(P0.05)。从多样性指数分析看,Shannon-Wiener指数、Simpson指数、Brillouin指数和Pielou指数均随连作年限的延长呈先升后降的变化,其中连作3 a时各项指数最大,连作7 a时最小,表明在本试验年限范围内,连作使得微生物群落多样性与均匀程度皆出现了一定程度的降低。相关性分析表明,土壤微生物各类群PLFAs量、微生物量及土壤肥力之间存在相关性,说明土壤微生物量与土壤肥沃程度相关,可作为评价土壤肥力的生物学指标。可见,加工番茄连作改变了土壤微生物群落结构,降低了土壤微生物量,最终在根际土壤微生态系统和环境因子等因素的综合作用下产生连作障碍。