PLA平铺沙障对沙丘土壤颗粒分形特征的影响

采用室外调查与室内分析相结合的方法,统计分析了毛乌素沙地PLA沙障铺设5年后的土壤颗粒粒径组成、分形维数及其与土壤砂粒(0.05 mm)、粉粒(0.05~0.002 mm)和黏粒(0.002 mm)含量的之间的关系。结果表明:研究区沙物质颗粒主要以粒径大于0.05 mm的细沙、极细沙为主。设置PLA沙障后,导致沙丘中粗沙含量减少,黏粒物质增加。沙障规格对土壤分形维数的影响表现为规格越小,土壤分形维数越大。沙丘表层分形维数与砂粒含量(0.05 mm)呈极显著的负相关关系,而与黏粒含量呈极显著的正相关关系。该地区颗粒分形维数的临界粒径为0.05 mm粒径物质,低于0.05 mm的颗粒含量越多,分形维数越高,反之则越低。设置PLA沙障后,黏粒物质聚集和沙粒物质的降低共同导致分形维数的增加。     

封育对天然草地深层土壤粒径分形特征的影响

为了明确长期封育对天然草地土壤粒径分形的影响,采用空间序列代替时间序列的方法,试验对比研究了黄土高原宁夏固原云雾山自然保护区封育30年草地和放牧草地的深层土壤粒径分形特征。结果表明:(1)封育30年草地土壤中粉粒含量显著低于放牧草地(p0.05),分别为21.1%和28.1%。(2)封育30年草地的土壤粒径分形维数明显高于放牧草地(p0.01),在140—500cm的土层中表现尤为显著。(3)土壤粒径分形维数与粉粒和极细沙粒含量呈极显著正相关(p0.01),而与细沙粒、中沙粒、粗沙粒呈极显著负相关(p0.01)。因此,长期封育草地土壤粒径趋于变大,中细颗粒土壤积累减少,同时长期封育影响深层土壤结构,深层土壤物理结构信息不容忽视。     

黄土丘陵区红豆草和苜蓿植物篱对土壤颗粒组成的影响

以苜蓿、红豆草两种植物篱为研究对象,对黄土丘陵沟壑区坡耕地布设植物篱后不同坡位土壤颗粒含量的变化、土壤分形维数进行研究,分析了植物篱对土壤颗粒组成的影响。结果表明:（1）同坡面相比,中坡及下坡土壤极细沙粒与粗粉粒含量增加,细粉粒与黏粒含量减少,出现相对于上坡的土壤机械组成粗化现象,且下坡粗化程度大于中坡;（2）相对于对照坡面,植物篱坡面各坡位粗化现象均得到缓解,红豆草对土壤颗粒的影响在上坡表现明显,苜蓿的影响在下坡表现明显;（3）坡面土壤分形维数呈现上部 > 中部 > 下部,苜蓿 > 红豆草 > 对照样地;（4）土壤颗粒与土壤分形维数的相关性分析显示,土壤分形维数与极细沙粒、粗粉粒呈极显著（P < 0.01）负相关,与黏粒呈显著（P < 0.05）正相关。     

库布齐沙漠生态光伏电站不同覆盖类型下土壤粒度特征

以亿利生态光伏电站3种不同立地条件的光伏电板阵列内沉积物为研究对象,利用激光衍射技术研究地表不同位置0～5 cm沉积物粒度组成,计算平均粒径、标准偏差、分形维数等粒度参数。结果表明:(1)光伏区沉积物以细沙、中沙、极细沙为主。其中甘草光伏区还有少量的粉沙,其体积百分含量为2.93%,裸沙光伏区土壤细沙粒、中沙粒体积百分比分别为74.03%和23.24%,秸秆光伏区细沙粒、中沙粒颗粒体积百分比分别为82.76%和14.41%。(2)秸秆和甘草光伏区极细沙粒百分含量上升,分选性变差,峰态平缓,偏度近似对称,分形维数数值增大,但相比裸沙光伏区,甘草光伏区的标准偏差和峰态值有一定的规律,但秸秆光伏区的标准偏差和峰态值无明显规律。(3)挟沙气流受到光伏电板倾斜角的加速,对光伏电板板间、板下、基座三处位置的土壤颗粒粗细分配不均,且铺设秸秆不足以能使土壤颗粒的细粒组分朝良好趋势发展,种植甘草可以使土壤细粒组分增多。     

塔里木河干流上中游河床沉积物粒度分形特征初探

利用体积分形维数模型对塔里木河干流上中游河床沉积物的粒度分形特征进行分析,并探讨了沉积物分形维数与粒度组成、粒度参数的相关关系,结果表明:(1)塔里木河干流上中游河床沉积物粒度粒径介于0~9 mm,黏粒、粉粒与砂粒含量的均值分别为11.46%、53.29%和35.25%,采集样品中有2/3为细粒土,其余为细粒土质砂,沉积物质地相对较细。(2)沉积物体积分形维数介于1.921~2.403,均值为2.114,河床沉积物粒度组成相对简单。(3)沉积物分形维数与黏粒及粉粒含量呈显著的正相关关系,相关系数分别为0.594、0.372,与砂粒含量呈显著的负相关关系,相关系数为-0.538,分形维数越大,沉积物质地越细。(4)分形维数与平均粒径呈显著的负相关关系,相关系数为-0.529,与标准差、偏度和峰度呈现显著的负相关关系,相关系数分别为0.272、0.714和0.483,分形维数可反应沉积物粒度参数的综合特征。     

草方格造林固沙过程中土壤性质变化及分形特征——以腾格里沙漠东南缘为例

以腾格里沙漠东南缘草方格人工固沙植被区为研究对象,分别选取流动沙地、4年和30年固沙植被区为研究样地,于春季、夏季和秋季研究了草方格造林固沙过程中土壤性质变化及分形特征。结果表明:(1)土壤含水量与土壤pH既受到不同固沙年限的影响,亦受到季节变化的调控。(2)流动沙地、4年和30年固沙植被区土壤电导率分别为77.84～82.34,86.04～114.68,113.80～168.66μS/m,土壤有机碳含量分别为0.86～1.74,1.30～1.52,7.96～17.36g/kg,土壤全氮含量分别为0.18～0.32,0.24～0.26,0.44～0.78g/kg。(3)仅流动沙地土壤具有粗沙粒成分,含量占0.50%～0.53%。流动沙地、4年和30年固沙植被区土壤中沙粒含量分别为40.42%～43.82%,14.36%～17.17%和12.01%～14.75%,土壤细沙粒含量分别为55.44%～58.84%,80.15%～83.19%和42.55%～53.30%,土壤极细沙粒含量分别为0.24%～0.31%,2.45%～3.33%和15.85%～21.35%。仅30年固沙植被区土壤具有黏粒和粉粒成分,含量分别为0.84%～1.33%和15.16%～22.75%。(4)土壤粗沙粒与土壤电导率间呈负相关性(P0.05),土壤细沙粒、中沙粒均与土壤电导率、有机碳、全氮、碳氮比之间呈显著负相关性(P0.01),而土壤黏粒、粉粒、极细沙粒均与土壤电导率、有机碳、全氮、碳氮比呈显著正相关性(P0.01)。(5)土壤分形维数介于0～3。流动沙地、4年和30年固沙植被区土壤分形维数分别为0.55～0.82,1.57～1.67和2.37～2.59。(6)土壤分形维数与土壤粗沙粒和中沙粒间呈负相关性(P0.05),与土壤黏粒、粉粒和极细沙粒间呈显著正相关性(P0.01),而与土壤细沙粒间无相关性(P0.05)。研究表明,在腾格里沙漠地区扎设草方格并进行人工造林固沙,有利于改善土壤质地,促使土壤理化性质向良好的方向发展,促进土壤质量提升和实现沙漠化防治。     

王茂沟流域淤地坝系土壤颗粒与有机碳分布特征研究

为了研究黄土高原丘陵沟壑区坝系坝地土壤颗粒与有机碳的分布特征,以陕北绥德县王茂沟小流域为研究对象,选取了47个土壤剖面,采集土样940个,分析了分形维数、粗化度、有机碳与各粒径组成之间的关系。结果表明:（1）研究区坝地的土壤粒径分布中,粉粒含量占主导地位,依次为砂粒、黏粒;（2）王茂沟坝地土壤颗粒的分形维数在2.674~2.829之内变化,垂直剖面上变化很微小,坝前、坝中、坝后土壤颗粒分形维数分别为2.803 3,2.783 6,2.795 8;（3）王茂沟坝地土壤质地粗化度在0.27~0.58,平均值为0.44,坝前（0.40） < 坝后（0.45） < 坝中（0.46）;（4）坝地土壤颗粒在0.05~0.002 mm和 < 0.002 mm范围内与土壤颗粒的分形维数成极显著正相关,在2.0~0.05 mm范围内与土壤颗粒的分形维数成极显著负相关;坝地土壤有机碳与粉粒和黏粒呈正相关,与细砂粒和极细沙粒含量呈负相关。     

基于土壤粒度参数的荒漠草原地表粗粒化过程

草原退化特征已由植被变化为主演变为土壤退化的阶段,其植被覆盖变化可在一定程度上反映退化状况与过程,探明荒漠草原不同退化阶段(覆盖度)地表风蚀状况,对合理利用与保护草地资源意义重大。以希拉穆仁荒漠草原7个覆盖度(裸地,5%,20%,40%,60%,80%和100%)下的表层土壤为研究对象,利用激光衍射技术测量表层0—1cm土壤粒度组成,分析不同覆盖度下的平均粒径、标准偏差、偏度、峰态及分形维数等粒度参数变化情况及颗粒频率分布。结果表明:(1)土壤粒度组成均以沙粒和粉粒为主,黏粒含量较低;偏度可作为有效粒度参数指标。(2)随着盖度降低,平均粒径数值越大,分选性越好,频率曲线由近于对称—正偏—极负偏转变,峰态由尖锐变平缓,分形维数先增加后降低。(3)粒径分布基本呈双峰分布,盖度越小第二波峰滞后越明显,且分布均匀程度越低,易风蚀颗粒范围为144~869μm。     

毛乌素沙地西南缘不同土地利用类型土壤颗粒分形特征

为揭示毛乌素沙地西南缘农田、荒地、草地、灌丛沙堆和林地等土地利用类型的土壤分形特征与防风固沙效果的关系,采用野外取样与室内粒度分析相结合的方法,分析了该区5种土地利用类型的土壤颗粒粒径分布、分形维数以及土层深度与分形维数间关系。结果表明:(1)草地、灌丛沙堆以及林地的土壤粒度组成以极细沙、细沙和中砂为主,耕地和荒地则以粉粒和细砂为主;(2)研究区不同土地利用方式的土壤粒径分布和分形维数差异明显,荒地>农田>灌丛沙堆>草地>林地,随土层深度增加,林地分形维数值减小,草地分形维数值增大,荒地、农田和灌丛沙堆分形维数值变化不大;(3)分形维数与<100 μm和>100 μm粒径含量分别呈显著正相关和负相关,其大小由<100 μm的极细砂粒和粉粒含量决定。研究区内5种土地利用类型土壤颗粒粒径分布与分形维数差异显著,这综合反映出在不同植被效应与人为耕作后,土壤的颗粒组成会发生明显变化。研究结果可为毛乌素沙地西南缘防沙治沙以及土壤恢复提供理论依据。     

松嫩平原西部典型盐生景观土壤分形维数及盐碱化特征

为探究松嫩平原西部典型盐生景观土壤颗粒粒度组成及分形特征与土壤盐碱化之间的关系,采用体积分形维数模型计算了6种典型盐生景观土壤表层0—30 cm颗粒组成及分形维数,结合相关分析法分析了土壤分形维数与质地、盐碱特征之间的相关性。结果表明:(1)6种典型盐生景观中农田土壤分形维数值最小(2.35),碱蓬群落土壤最大(2.61),分形维数均值为2.48,分形维数随盐生景观土壤碱化程度增加而增大。(2)土壤质地越粗,砂粒含量越高,分形维数值越小;土壤质地越细,黏粒和粉粒含量越高,分形维数越大。(3)分形维数与盐分含量呈显著正相关(r=0.87,P0.05),尤其与盐分组成中HCO_3~-含量呈极显著正相关(r=0.89,P0.01),与养分中总磷含量呈极显著正相关(r=0.90,P0.01)。(4)土壤颗粒组成中砂粒、粉粒和黏粒与盐分、HCO_3~-及总磷含量也存在极显著相关性。不同盐生景观土壤分形维数与土壤颗粒组成和土壤盐分之间存在显著的相关性,因此可以用分形维数来反映土壤质地和指示土壤盐碱化特征。     

Polymorphism of high molecular weight glutenin subunits in three species of Aegilops

A collection of 136 accessions of Aegilops umbellulata (39), Ae. comosa (75) and Ae. markgrafii (22) was analysed for high-molecular-weight (HMW) glutenin subunits composition. The homogeneity of the accessions was studied and 55.1% of the collection was homogeneous for HMW glutenin subunits (29 Ae. umbellulata, 33 Ae. comosa and 14 Ae. markgrafii). The HMW glutenin subunits of Ae. umbellulata are encoded by the Glu-U1 locus; in Ae. comosa results showed that this proteins are encoded at the 1M chromosome, and the locus was named Glu-M1. In Ae. markgrafii it was assumed that HMW glutenin subunits were encoded by an homoeologous locus and it was named Glu-C1. All the accessions of Ae. umbellulata and Ae. markgrafii expressed both, x-type and y-type subunits. Among the Ae. comosa accessions, only one expressed an x-type subunit alone. All the accessions of Ae. umbellulata and some of Ae. comosa had x-type glutenins of higher molecular weights than those commonly present in bread wheat. A total of 8 alleles were detected at the Glu-U1 locus, 11 at the Glu-M1 and 4 at the Glu-C1. The new HMW glutenin variation found in this work suggests their possible utilisation in breeding for wheat quality.     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Powdery Mildew Resistance in a Collection of Chinese Barley Varieties

One hundred and forty-seven Chinese barley varieties maintained at the Gene Bank of the National Barley Improvement Centre, Zhejiang, and 84 progenies from these varieties were tested at the seedling stage for their reaction to 32 selected pathotypes of Blumeria graminis f. sp. hordei. Eighteen resistance spectra were identified comprising single or combined resistances from eight known (Ml(Bw), Ml(Ch), Mla7, Mla8, Mla9, Mla13, MlaRu4 and Mlg) and six unknown resistance genes. The most frequent gene was Ml(Bw), which was found in 69 varieties and previously detected in only a few European winter barley varieties. The genes Mla8 and Ml(Ch) were also often present, but other resistance genes were rare. After inoculation, considerably fewer pathogen colonies were observed in ‘Aiganqi’ and one line of ‘Tong5’. Twenty varieties were composed of lines with different resistance genes. China is likely to be a region of origin of the genes Ml(Bw), Mla7, as well as three unknown genes found in original landraces and perhaps another three unknown genes detected in cultivars bred in China. The resistances of varieties from the Zhejiang province and those originating from 11 other Chinese provinces were quite different. Unfortunately, none of the varieties are promising sources of resistance to powdery mildew and China does not seem to be a region suitable for identifying such sources.     

Genetic diversity of rhizobia associated with indigenous legumes in different regions of Flanders (Belgium)

We investigated the diversity of rhizobia isolated from different indigenous legumes in Flanders (Belgium). A total of 3810 bacterial strains were analysed originating from 43 plant species. Based on rep-PCR clustering, 16S rRNA gene and recA gene sequence analysis, these isolates belonged to Bradyrhizobium, Ensifer (Sinorhizobium), Mesorhizobium and Rhizobium. Of the genera encountered, Rhizobium was the most abundant (62%) and especially the species Rhizobiumleguminosarum, followed by Ensifer (19%), Bradyrhizobium (14%) and finally Mesorhizobium (5%). For two rep-clusters only low similarity values with other genera were found for both the 16S rRNA and recA genes, suggesting that these may represent a new genus with close relationship to Rhodopseudomonas and Bradyrhizobium. Primers for the symbiotic genes nodC and nifH were optimized and a phylogenetic sequence analysis revealed the presence of different symbiovars including genistearum, glycinearum, loti, meliloti, officinalis, trifolii and viciae. Moreover, three new nodC types were assigned to strains originating from Ononis, Robinia and Wisteria, respectively. Discriminant and MANOVA analysis confirmed the correlation of symbiosis genes with certain bacterial genera and less with the host plant. Multiple symbiovars can be present within the same host plant, suggesting the promiscuity of these plants. Moreover, the ecoregion did not contribute to the separation of the bacterial endosymbionts. Our results reveal a large diversity of rhizobia associated with indigenous legumes in Flanders. Most of the legumes harboured more than one rhizobial endosymbiont in their root nodules indicating the importance of including sufficient isolates per plant in diversity studies.     

Changes in trace element speciation in kola north surface waters during snow melt

The powerful mass-flow of melt water during the brief period of spring thaw provides a surge of pollutants and causes extremely toxic short term conditions. Together with the increase in total metal concentrations during this period, a redistribution in metal speciation occurs that increases the proportion of more toxic forms. Concentrations of ion-exchangeable fractions of nickel (Ni), copper (Cu), aluminium (Al), and manganese (Mn) show strong negative correlations with pH. The sum of complex metal species shows a strong positive correlation with total organic carbon (TOC). A data analysis model based on relationships observed between key parameters and metal behaviour together with gidrological data allowed an assessmrnt of the metal impact on waterbodies from accumulated airborne pollution (Ni, Cu) as well as from accelerated leaching from watersheds (Al, Mn).     

Sources of powdery mildew resistance in a wild barley collection

A total of 1,383 accessions of wild barley (Hordeum vulgare ssp. spontaneum) held in the USDA-National Small Grains Collection, Aberdeen were screened for resistance to powdery mildew (Blumeria graminis f. sp. hordei) in the Czech Republic. They were subsequently tested at the seedling stage for reaction to selected powdery mildew pathotypes and simultaneously for their adult plant resistance in the field. One hundred and twenty-three accessions exhibited resistance to 22 pathotypes in the greenhouse tests (reaction type 2–3 or lower) as well as resistance to the natural population of this pathogen in the field in the Czech Republic during at least 2-year testing. These accessions represent large amount of promising sources in breeding barley for resistance to powdery mildew.     

Agricultural potential of Mediterranean grain and forage legumes: Key differences between and within Vicia species in terms of phenology, yield, and agronomy give insight into plant adaptation to semi-arid environments

In order to identify key adaptive traits which affect productivity in Mediterranean grain and forage legumes and simultaneously determine the agricultural potential of a wide range of Vicia species, germplasm collected from the wild throughout the eastern Mediterranean was grown under semi-arid conditions in Tel Hadya, Syria (313 mm growing season rainfall). These included species currently in use in Mediterranean agriculture, such as V. sativa L., as well as those more widely used in the past-such as V. ervilia L., but also a broad selection from Section Narbonensis (B. Fedtsch. ex Radzhi) Maxted, including V. narbonensis L, V. johannis Tamamsch., V. hyaeniscyamus Mout., V. serratifolia Jacq., and V. kalakhensis Khattab et al. V. faba, a near relative of the taxa in Section Narbonensis, was included as a domesticated control. Where applicable, a representative range of subspecies was used. Accessions were chosen from a wide range of habitats in terms of latitude (31.02–40.72 decimal^o), longitude (27.1–43.17 decimal^o), altitude (20–1510 m), rainfall (180–1700 mm/yr) and soil depth (5–50 cm) in order to maximise diversity within species. Agricultural potential was determined by measuring seed, hay and biological yield, as well as agronomic traits such as harvest index, standing crop height, and seed size. The comparative influence of phenology and key agronomic traits such as plant habit and seed size on productivity varied tremendously between species, depending on their reproductive strategies. In V. sativa and V. ervilia, the smaller seed species which rely on long vegetative phases and growing seasons to accumulate sufficient biomass to set seed, and in which there was comparatively little agronomic variation, phenology had a large impact on yield. In early emerging taxa such as V. ervilia and V. s. subsp. sativa, with built-in long vegetative phases and growing seasons, seed yield was negatively correlated with flower ing (r = –0.86 to –0.88), whereas the opposite was the case for later emerging taxa such as V. s. subsp. nigra (L.) Ehrh. (r = 0.95). Within V. narbonensis and relatives, the larger seeded Vicia species which rely on more conservative reproductive strategies where high seedling vigour associated with large seeds enables the species to enter reproductive phases relatively early, phenology had a much smaller impact on yield than did variation of key traits such as seed weight, plant habit and pod shattering. Among the undomesticated germplasm harvest indices ranged from 0.09–0.31, hay yields from 0.1–3.4 t/ha, seed yield from 0–2.0 t/ha, and dry matter at maturity from 1.6–6.5 t/ha. Sub-specific taxonomy was crucial in determining agronomic potential. V. narbonensis var. aegyptiaca Kornhuber ex Asch. et Schweinf. showed the most potential, combining an upright habit, large seeds (212 mg) and tendency to retain intact pods after maturity, with the highest yield, harvest index and crop height of all the wild Vicia species. V. sativa subsp. sativa, V. ervilia and V. narbonensis var. narbonensis were less productive, but still showed agricultural potential. The smaller seeded V. narbonensis, var. affinis, var. jordanica H. Schäf. and var. salmonea (Mout.) H. Schäf., and their close relatives V. johannis, V. hyaeniscyamus, V. serratifolia and V. kalakhensis have little to offer Mediterranean agriculture on the basis of poor agronomy.     

Changes in rhizosphere microbial activity mediated by native or allochthonous AM fungi in the reafforestation of a Mediterranean degraded environment

This study was carried out in a semiarid degraded area to assess the effectiveness of mycorrhizal inoculation with a mixture of native arbuscular mycorrhizal (AM) fungi or an allochthonous AM fungus (Glomus claroideum), on the establishment of Olea europaea subsp. sylvestris L. and Retama sphaerocarpa (L.) Boissier in this area. Associated changes in the soil microbiological properties and aggregate stability related to these AM inocula were also recorded. Eighteen months after planting, G. claroideum had increased available P in the rhizosphere of both shrub species. In general, both inoculation treatments increased water-soluble C and water-soluble and total carbohydrates, G. claroideum being the most effective inoculum, particularly in R. sphaerocarpa. The mixture of native AM fungi was the most effective treatment for increasing the aggregate stability of R. sphaerocarpa soil, while that of O. europaea was increased only by G. claroideum. Increased (dehydrogenase, urease, protease-BAA, acid phosphatase and -glucosidase) enzyme activities, in particular of dehydrogenase and acid phosphatase, were recorded in the rhizosphere of both mycorrhizal shrub species. The mixture of native AM fungi was the most effective treatment for stimulating the growth of O. europaea and R. sphaerocarpa (11.6-fold and 3.3-fold, respectively, greater than control plants). The establishment of mycorrhizal shrub species favoured the reactivation of soil microbial activity, which was linked to an increase in aggregate stability.