念珠藻葛仙米叶绿素荧光与水分胁迫的关系

在渗透系统中,念珠藻葛仙米因轻微失水而叶绿素的Ｆｖ／Ｆｍ上升,水势继续降低时Ｆｖ／Ｆｍ快速下降。衬质系统和自然失水的影响相似,藻体在失去总水分的９４％以后Ｆｖ／Ｆｍ开始下降,此前水分的丢失对Ｆｖ／Ｆｍ比值的上升稍有促进和。干燥藻体吸水后Ｆｖ／Ｆｍ的恢复速率随着贮藏时间的延长而下降,并且Ｆｖ／Ｆｍ的恢复对光和蛋白南的重新合成有依赖性。ＤＣＭＵ虽然也抑制Ｆｖ／Ｆｍ的恢复,但可逆转。     

Cytochemical changes in the developmental process of Nostoc sphaeroides (cyanobacterium)

There are several apparent developmental stages in the life cycle of Nostoc sphaeroides Kützing, an edible cyanobacterium found mainly in paddy fields in central China. The cytochemical changes in developmental stages such as hormogonia, aseriate stage, filamentous stage and colony in N. sphaeroides were examined using fluorescent staining and colorimetric methods. The staining of acidic and sulfated polysaccharides increased with development when hormogonia were used as the starting point. Acidic polysaccharides (AP) were most abundant at the aseriate stage and then decreased, while the sulfated polysaccharides (SP) were highest at the colony stage. Quantitatively, along the developmental process from hormogonia to colony, total carbohydrates first increased, then became stable, and then reached their highest level at the colony stage, while reducing sugars were highest at the hormogonia stage and then decreased sharply once development began. SP were not detectable in the hot water soluble polysaccharides (HWSP), and hormogonia had the lowest content of AP, while old colonies had the highest. The AP content of the aseriate stage, filamentous stage and young colony stage were very similar. The evolutionary relationships reflected in the developmental stages of N. sphaeroides are discussed.     

不同水分管理方式对稻田土壤生物学特性的影响

在下辽河平原单季稻地区研究了常规浅湿干灌溉 (CK)、浅湿干灌溉薄膜阻渗 (IC)、湿润灌溉薄膜阻渗 (MC)、淹水灌溉薄膜阻渗 (FC) 4种不同水分管理方式下土壤线虫及土壤微生物量的动态变化。结果表明 ,耙耕前 ,CK、FC处理食细菌线虫数量显著高于MC、IC处理 ;薄膜阻渗在黄熟期显著降低了土壤食细菌线虫的数量 ,在耙耕前显著降低了食真菌线虫数量。潮棕壤稻田食真菌线虫与食细菌线虫相比数量较低。在耙耕前不同水分管理方式下土壤微生物量C显著低于对照。不同水分管理方式在水稻分蘖期、抽穗期对食细菌线虫数量、食真菌线虫数量、微生物量C和微生物量N没有影响。土壤食细菌线虫、食真菌线虫数量与土壤微生物量C、N没有达到显著相关。     

Effects of soil physicochemical properties and stand age on fine root biomass and vertical distribution of plantation forests in the Loess Plateau of China

The responses of aboveground parts of the forest to changes in environmental factors and stand age is well studied, but the same is not true for the belowground parts of the forest. Two plantation black locust (Robinia pseudoacacia L.) forest sites were taken in the Loess Plateau of China, one in the drier, infertile, more sandy area of the middle Loess Plateau, and another in the wetter, fertile, more clay-filled area of the southern Loess Plateau. At each site, both a younger (8-year-old) plantation stand and an older (30-year-old) plantation stand were included to study the effects of soil physicochemical properties and stand age on the fine root (<2?mm) biomass and vertical distribution of black locust forests. Root samples were taken with soil cores to a depth of 100?cm. The fine root biomass decreased from the middle site to the southern site for both stand ages, as expected, and the decrease could be due to a higher fine root N concentration associated with a higher fine root turnover rate at the southern site. There was a similar rooting pattern, though not deeper, in the drier, sandy site as predicted based on soil water infiltration and evaporation demands. The different effects of stand characters (e.g., tree density, tree height) on the fine root distribution as compared with the environmental properties may contribute partly to the similar pattern found in the two sites. The fine root biomass increased with stand age in both sites. In contrast to the evident difference in fine root biomass, there was no clear trend in the fine root vertical distribution pattern with stand age. Our results indicate that fine roots are likely to respond to changes in soil physicochemical properties and stand age by changing fine root biomass rather than by varying rooting pattern.     

秸秆还田方式对东北水稻土理化性质及微生物群落的影响

【目的】研究秸秆还田方式对东北黑土理化性质及微生物群落的影响。【方法】试验周期为2019年12月至2021年10月,秸秆还田采用2种方式： 秸秆直接还田+微生物菌剂WJ(strawdirect return+microbial agent WJ;MD),秸秆堆肥还田+微生物菌剂WJ(straw compost return +microbial agent WJ;MC)。分析土壤肥力、酶活和微生物群落。【结果】分析两种方式土壤有机质(SOM)、腐殖酸(HS)和富里酸有机碳(FA-C)含量,发现秸秆直接还田+微生物菌剂WJ比秸秆堆肥还田+微生物菌剂WJ分别增加2.28g/kg、7.82g/kg和5.26g/kg。土壤铵态氮(NH4⁺-N)、速效磷(AP)略高于秸秆堆肥还田+微生物菌剂WJ,均在6月份达到峰值。胡敏酸有机碳(HA-C)含量下降。此外,土壤脲酶、转化酶、纤维素酶活性和碱性磷酸酶活性对比发现,秸秆直接还田+微生物菌剂WJ比秸秆堆肥还田+微生物菌剂WJ分别高8.55%、15.46%、4.35%和6.19%。高通量测序结果显示,秸秆直接还田+微生物菌剂WJ中细菌和真菌的多样性均比秸秆堆肥还田+微生物菌剂WJ丰富。其中Anaerolinea、Bacteroidetes、Pseudomonas为优势细菌,Tausonia、Mrakia、Mrakiella为优势真菌。【结论】秸秆直接还田+微生物菌剂WJ比秸秆堆肥还田+微生物菌剂WJ更有利于土壤有机质、腐殖酸、土壤酶活性和微生物多样性的增加,这说明秸秆添加WJ菌剂直接还田可以减少有机养分的流失,保持田间土壤肥力。     

Root biomass distribution and soil properties of an open woodland on a duplex soil

Data on the distribution of root biomass are critical to understanding the ecophysiology of vegetation communities. This is particularly true when models are applied to describe ecohydrology and vegetation function. However, there is a paucity of such information across continental Australia. We quantified vertical and horizontal root biomass distribution in a woodland dominated by Angophora bakeri and Eucalyptus sclerophylla on the Cumberland Plains near Richmond, New South Wales. The site was characterised by a duplex (texture contrast) soil with the A horizon (to 70 cm) consisting of loamy sand and the B horizon (to > 10 m) consisting of sandy clay. The topsoil had a smaller bulk density, a smaller water holding capacity but a larger organic component and a larger hydraulic conductivity in comparison to the subsoil. Root biomass was sampled to 1.5 m depth and declined through the soil profile. Whilst total biomass in the B horizon was relatively small, its contribution to the function of the trees was highly significant. Coarse roots accounted for approximately 82% of the root mass recovered. Lateral distribution of fine roots was generally even but coarse roots were more likely to occur closer to tree stems. Variation in tree diameter explained 75% of the variation in total below-ground biomass. The trench method suggested the belowground biomass was 6.03?±?1.21 kg m^?2 but this method created bias towards sampling close to tree stems. We found that approximately 68% of root material was within a 2 m radius of tree stems and this made up 54% of the total number of samples but in reality, only approximately 5 to 10% of the site is within a 2 m radius of tree stems. Based on these proportions, our recalculated belowground biomass was 2.93?±?0.59 kg m^?2. These measurements provide valuable data for modeling of ecosystem water use and productivity.     

高黎贡山土壤微生物生态分布及其生化特性的研究

研究了高黎贡山东坡不同海拔高度的自然林、不同海拔高度和人为干扰强度的集体林、不同权属森林和不同土地利用类型土壤微生物数量及某些生化特性。结果表明,在高黎贡山上半部,自然林随海拔降低,土壤微生物数量及活性升高。而下半部,集体林随海拔降低,人为干扰强度和频率增加,土壤微生物数量和活性降低;森林权属从国有集体个人,土壤微生物数量及活性降低;森林被纯林替代后,土壤微生物数量及活性迅速降低,但耕作通常更有利于微生物繁殖。高黎贡山中部(海拔2000m左右)的自然植被下土壤微生物含量丰富且活性较高,但海拔高气温低不利于土壤微生物生长繁殖及进行生物化学变化。另一方面,森林植被的过份砍伐和利用也使土壤微生物数量和活性降至较低水平。     

放牧对贝加尔针茅草原植被根系分布和土壤理化特征的影响

以内蒙古贝加尔针茅草原为研究对象,分析了放牧对植被根系分布特征的影响及其与土壤理化性状的相互关系。结果表明:放牧导致植被根系分布发生显著变化;0～10cm土层根系生物量占0～40cm根系总生物量的65.9%～82.6%,直径≥2mm根系和直径1mm的根系对放牧影响较为敏感;植被根系分布与土壤容重、含水量、全氮、全磷、有机碳含量以及阳离子交换量有一定程度的相关性,放牧主要通过改变土壤理化特征影响不同径级根系生物量的分布,同时各径级根系分布特征对土壤理化性状有一定的反馈作用。     

Hormogonia mass differentiation from Nostoc sphaeroides Kütz. (cyanobacterium) and the comparison of structural characteristics between hormogonia and vegetative filaments

It was found that, after colonies of Nostoc sphaeroides Kütz. in exponential phase of growth were transferred to fresh complete BG‐11₀ medium, the hormogonia differentiated independent of the type of preculture used. This provided evidence that the hormogonia differentiation was not directly related to phosphorus and potassium status, nor to the osmotic effect of the media. In contrast, all the cultures in the stationary growth phase had no hormogonium differentiation after being transferred to fresh medium. However, the incomplete media for preculture seemed to favor the liberation of hormogonia from colonies to the medium. The result showed that the morphology and ultrastruc‐tures of the vegetative filament, the main stage of Nostocacean life history, determine its adaptability in changing environments, while the hormogonium remains as a propagule of the species.     

有机稻鸭共作对土壤理化性状和细菌群落空间分布的影响

为探明有机稻鸭共作对不同深度耕层土壤理化性状和细菌群落的影响,采用田间实验,研究了有机稻鸭共作(12年)和转型期稻鸭共作(3年)田在0～6、6～13和13～20 cm土层的理化性状和细菌群落结构变化规律。结果表明:有机稻鸭共作12年后,0～6和6～13 cm土壤理化性状得到较大程度改善,但13～20 cm层改变较小;与转型期稻鸭共作相比,有机稻鸭共作显著改变了细菌群落组成,使不同耕层土壤具有了更高比例的共同细菌门;同时还提高了各耕层土壤细菌群落的丰富度和多样性,减小了各耕层土壤细菌群落结构分布差异性,这在0～6 cm层土壤中表现尤为明显,使细菌群落结构整体朝着更加稳定方向发展;相关分析表明,pH值、土壤容重、全氮和硝态氮是影响有机稻鸭共作后土壤细菌群落空间分布的重要因子。综合来看,有机稻鸭共作主要通过改变土壤理化性状来影响细菌群落的空间分布,是促进农业可持续发展的一种重要模式。     

The role of surface physicochemical properties in determining the distribution of the autochthonous microflora in mineral water bottles

Investigation of the distribution of the viable autochthonous microflora in three brands of 1-2-month-old bottled mineral water showed that 1.8 x 10(4) (S.E.M. 8.9 x 10(3), n = 5) to 1.2 x 10(5) (S.E.M. 1.3 x 10(4), n = 5) cfu ml-1 were planktonic cells while 11 (S.E.M. 4, n = 5)-632 (S.E.M. 176, n = 5) cfu cm-2 were found in the biofilm. The biofilm represented between 0.03 and 1.79% of the total viable microbial population in the 1.5 litre bottles studied. Scanning electron microscopy studies showed that the cells adhering to the polyethylene terephthalate (PET) bottles were predominantly rod-shaped, sparsely distributed over the surface. In contrast, the cells adhering to the high density polyethylene (HDPE) caps were found to be mainly clumps of coccoid cells, suggesting that the bottle may provide different microhabitats for different microfloras. Large-scale roughness, such as that observed as lettering inside the cap (average height (z) = 93 microns) was associated with a 46-fold increase in cell numbers. Increased small-scale roughness, as measured by atomic force microscopy on PET and HDPE surfaces (average roughness (Ra) = 5-551 (nm), showed no correlation with adhesion. Investigations of surface hydrophobicity by the sessile drop technique showed that contact angles (theta) were greater on the HDPE caps (theta = 89-96 degrees) than on the PET surfaces (theta = 69-80 degrees). However, no correlation was found between contact angle and attached cell numbers. Measurements of surface electrostatic charge by streaming potential showed that the PET carried an overall negative charge, measuring -15.9 to -16.6 mV in mineral water. No significant change in charge occurred when the monomer composition of the PET was altered. It was concluded that surface roughness, in particular the scale of surface topographical features, is the most important physicochemical surface characteristic determining the distribution of the autochthonous microflora in mineral water bottles.     

Effect of rainfall interannual variability on the biomass and soil water distribution in a semiarid shrub community

The dynamics of biomass and soil moisture in semiarid land is driven by both the current rainfall and the ecosystem memory. Based on a meta-analysis of existing experiments, an ecosystem model was used to calculate the effect of the rainfall interannual variability on the pattern of biomass and soil moisture in a shrub community. It was found that rainfall interannual variability enabled shrubs to be more competitive than grasses, and to maintain the dominant role over a longer time. The rainfall interannual variability resulted in complex soil moisture dynamics. The soil water recharge in wet years alternated with discharge in drought years.     

炉渣与生物炭施加对稻田土壤碳库及微生物的影响

以福州平原稻田为实验区,在2015年早、晚稻秧苗移栽前,对稻田进行施加生物炭、炉渣、生物炭+炉渣（混施）处理,并以不施加处理作为对照。为了了解施加处理的后续效应,于2017年检测早、晚稻拔节期和成熟期土壤有机碳含量及真菌、细菌数量。结果表明：3种施加处理稻田土壤有机碳（SOC）含量均比对照组有显著提高（P < 0.05）,但溶解性有机碳（DOC）、易氧化碳（EOC）、土壤微生物量碳（MBC）含量各处理之间差异不显著（P > 0.05）。与对照组相比,各施加处理组在一定程度上提高了土壤中真菌和细菌数量,但差异不显著（P > 0.05）。细菌数量与DOC含量呈极显著负相关（P < 0.01）,与EOC含量呈显著负相关（P < 0.05）,与MBC含量呈显著正相关（P < 0.05）。真菌/细菌比值与真菌数量、DOC含量呈极显著正相关（P < 0.01）。说明炉渣和生物炭施加处理2年后,仍可提高稻田土壤的碳库稳定性,并增加土壤微生物数量。     

滨海盐碱地刺槐(Robinia pseudoacacia)混交林土壤水盐动态

以固氮树种刺槐与绒毛白蜡、榆树、臭椿三树种的混交林及其纯林为研究对象,研究了刺槐与不同树种混交对土壤水分、盐分年动态变化的影响.研究结果表明:(1)刺槐与3个树种混交,刺槐臭椿混交林生长最好,均高于各自纯林.(2)混交林一定程度改善了土壤含水量及层次分布,土壤含水量整体趋势均表现出0～60 cm表层土中含水量高于各自纯林,而深层土壤含水量低的特点,只有8月份纯林和混交林的土壤含水量没有显著差别.不同树种在具体层次上略有差异;(3)混交林降低了土壤含盐量,改变了土壤盐分层次分布和年变化规律.不同月份间土壤含盐量随土壤深度、混交树种的变化而变化.深层土壤含盐量高,表层土壤含盐量低,混交林含盐量低于纯林且存在树种差异.混交林与纯林含盐量均雨季低,旱季高;但在某一具体月份各层次含盐量差别不大;不同土层含水量、含盐量与天然降水之间有明显的相关性,天然降水是混交林及纯林土壤水分的主要来源.     

Exopolysaccharide of Nostoc muscorum (Cyanobacteria) in the aggregation of soil particles

The effects on a saline-sodic soil of exopolysaccaride isolated from Nostoc Muscorum or the addition of a cyanobacterial mass proliferation were evaluated in a greenhouse experiment. By day 180 exopolysaccharide increased soluble C by 100%, microbial activity by 366% and the amount of water-stable aggregates larger than 250μm by 12 times. Inoculation with living cyanobacterial mass increased at the end of 365 oxidizable C by 11%, soluble C by 66%, microbial activity by 73% and aggregates larger than 250 μm by66%. A slimy film 3–5 mm thick, with N. Muscorum predominating, covered all the surface of inoculated soils. The higher soil aggregate stability produced by both treatments is a consequence of increased microbial activity and concentrating the soil polysaccharide. The high percentage of clays favours the creation of firm and long-lasting slime-mineral joints. Addition of isolated exopolysaccharide produces a faster and higher increase in soil aggregate stability than cyanobacterial mass inoculation. This revised version was published online in August 2006 with corrections to the Cover Date.     

稻鸭共作对稻田氮素变化及土壤微生物的影响

通过田间试验研究稻鸭共作生态系统中土壤与田面水全N、无机N的动态变化及水稻吸N的规律和土壤微生物数量的变化规律.结果表明,(1)与常规稻作相比,稻鸭共作稻田土壤、田面水全N含量略有提高,土壤、田面水NH 4含量和水稻含N量显著提高,而土壤、田面水NO-3含量无明显变化;(2)稻鸭共作极显著提高了水稻总吸N量,高于常规稻作17.8%;相关分析显示,水稻吸N量与NH 4含量呈一元二次方程式关系,达到显著或极显著相关.(3)与常规稻作相比,稻鸭共作能显著提高土壤微生物数量,其中细菌数最多,放线菌次之,真菌最少.     

三种纤毛虫对土壤微生物量和有效氮磷含量的影响

采用土壤培养方法研究了 3种纤毛虫对土壤微生物量及氮磷转化的影响 ,结果表明 ,向土壤接种肾形虫 ( Colopodia sp.)、尖毛虫 ( Oxytricna sp.)和澳毛虫 ( Australothrix sp.) ,特别是澳毛虫 ,显著地降低了土壤微生物碳。说明供试的原生动物与微生物之间存在消长关系。接种澳毛虫显著地降低了土壤有效磷含量 ,而肾形虫和尖毛虫对土壤有效磷含量影响很小 ,仅在培养后期显著地降低了土壤铵态氮含量 ,3种原生动物特别是澳毛虫 ,显著地降低了土壤氮矿化量和硝态氮含量 ,但提高了土壤铵态氮含量 ,说明 3种原生动物抑制了硝化作用 ,而增强了氨化作用。