Rust disease (Melampsora epited) of willow (Salix spp.) grown as short rotation coppice (SRC) in inter- and intra-species mixtures

Twenty inter‐ and intra‐species genotypes of willows (Salix spp.) were grown in large mono‐plots and incorporated into five, 10,15 and 20–way mixtures. In each growing season from 1996 to 2001 the level of rust disease caused by Melampsora epitea was recorded on each genotype where it was growing as a mono‐plot or as part of a mixture. Three genotypes, S. schwerinii×viminalis×dasyclados’V7531′, S. schwerinii×aquatica‘V7533’ and S. viminalis‘Gigantea’ remained virtually rust free through the six yr of the trial. It is, however, argued that there are benefits of including such genotypes in a mixture in order to reduce the risk of them developing rust susceptibility. S. burjatica‘Germany’, S. dasyclados×aquatica‘V7511’ and S. dasyclados×caprea‘V794’ were severely affected by rust, although levels tended to be less when included in mixtures. The levels of rust on S. mollissima‐undulata‘SQ83’ were much higher in the first three‐year harvest cycle than during the second cycle. On a number of genotypes, e.g. S. burjatica‘Germany’ and S. dasyclados×aquatica‘V7511’ rust was more severe on the regrowth from freshly coppiced stools.     

Correlation between pathogenicity and molecular characteristics in the willow leaf rusts <Emphasis Type="Italic">Melampsora epitea</Emphasis> and <Emphasis Type="Italic">M. humilis</Emphasis> in Japan

 We studied the correlation between pathogenicity and restriction fragment length polymorphism (RFLP) type, which was determined by polymerase chain reaction-based RFLP analysis of the internal transcribed spacer regions of ribosomal DNA, in the willow leaf rust fungi Melampsora epitea and M. humilis. Eighteen clones of eight Salix species were inoculated with urediniospores from seven collections of the two rust species. M. epitea and M. humilis (RFLP type-5 collections) were pathogenic to six to eight Salix species. RFLP type-7 collections of M. epitea were pathogenic to only two Salix species. The taxonomic relationships of the two rust species are discussed. Received: December 11, 2002 / Accepted: February 17, 2003 RID="*" ID="*" Contribution no. 179, Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba, Japan Acknowledgments We thank K. Katsuya, former professor at the University of Tsukuba, for his encouragement in this study. We are also grateful to M. Yashima, Botanical Garden, University of Tohoku, for his assistance in collecting materials and to R. Suzuki, University of Tsukuba, for providing a rust isolate.     

Development and characterization of microsatellite markers for the poplar rust fungi Melampsora medusae and Melampsora larici‐populina

Melampsora species and their hybrids are obligate parasites of Populus and Salix species worldwide. The increasing interest in Populus and Salix for biomass and fibre production necessitates genetic markers for population studies of Melampsora spp. Libraries enriched for simple sequence repeats were used to develop five microsatellite markers for Melampsora medusae and Melampsora larici‐populina. The variation detected by these markers will be valuable for phylogenetic and population genetic studies, substantiate putative hybrids, and deployment of resistant poplar clones.     

Parameters of photosynthesis light curve in <Emphasis Type="Italic">Salix dasyclados</Emphasis> and their changes during the growth season

A dependence of the photosynthesis rate on light is characterized by a number of parameters that are often used for comparison between plant species or for finding photosynthesis interconnections with other physiological processes. In order to properly assessed these parameters, we measured the maximum apparent photosynthesis rate (P _max), dark respiration rate (R _d), light compensation point (LCP), quantum yield corresponding to photosynthetic efficiency (QY), and the light saturation constant (K _s), taking into consideration the leaf plastochron index during vegetation of one of the willow species (Salix dasyclados Wimn.). The P _max value was the highest in the beginning of the growth season when the leaf reached 65% of its full area; after that P _max slowly declined. The most important cardinal value for R _d is its plateau reached by the end of leaf growth, i.e., later than the photosynthesis rate maximum. This plateau value also decreased during vegetation. The LCP value changed in the same way as R _d but reached its plateau simultaneously with the photosynthesis rate maximum. QY also reached its maximum at the same time with the photosynthesis rate; during vegetation it changed more than twofold. The K _s value also changed almost twofold during the season, reaching its maximum together or slightly later than the photosynthesis maximum and then remained constant. Thus, we have found significant changes in the parameters of the photosynthesis light curve during growth season. This shows that they can be used only after a thorough study of leaf development in each particular plant species. Usually performed measuring gas exchange parameters in fully developed leaves does not yield their maximum values and thus does not have any physiological sense.     

Isolation and characterization of microsatellite loci from the rust pathogen,Melampsora lini

We developed and characterized primers for 11 variable microsatellite loci present in the genome of the flax rust, Melampsora lini. The microsatellite loci were identified by sequencing clones from a library of EcoRI DNA fragments enriched for four simple sequence repeat motifs (AAG, AAT, TC and TG). All 11 primer pairs successfully amplified DNA fragments from a sample of 102 M. lini isolates (98 isolated from Linum marginale and four from Linum usitatissimum), revealing a total of 32 alleles. Allelic diversity at the 11 loci ranged from 0.030 to 0.449.     

Variation in the occurrence of rust (Melampsora spp.) and other diseases and pests, in short-rotation coppice plantations of Salix in the British Isles

A proportional odds model was employed to analyse simple assessments of disease and pest severity in plantings of short-rotation coppice willows at 18 sites in the UK over a 5-year period (1987–1991). Of a wide range of fungal diseases and pests encountered, the most severe and damaging were rusts, caused by Melampsora spp., and feeding damage due to beetles of the family Chrysomelidae. For rust, the model revealed highly significant (P < 0.001) interactions between the main factors, disease development within a season and between seasons, clones and sites. Within seasons, rust severity increased more at sites in the northern than in the southern UK, due mainly to low levels of occurrence at the northern sites early in the season. There was a gradual increase in rust severity over the 5-year period, although clones differed both in terms of disease severity and the extent of change in severity in any one year. Beetle feeding damage was also analysed in a similar way, indicating a general increase from 1987–1989, but also revealing differential patterns over time and between sites.     

On minimizing assignment errors and the trade‐off between false positives and negatives in parentage analysis

Genetic parentage analyses provide a practical means with which to identify parent–offspring relationships in the wild. In Harrison et al.'s study (2013a), we compare three methods of parentage analysis and showed that the number and diversity of microsatellite loci were the most important factors defining the accuracy of assignments. Our simulations revealed that an exclusion‐Bayes theorem method was more susceptible to false‐positive and false‐negative assignments than other methods tested. Here, we analyse and discuss the trade‐off between type I and type II errors in parentage analyses. We show that controlling for false‐positive assignments, without reporting type II errors, can be misleading. Our findings illustrate the need to estimate and report both the rate of false‐positive and false‐negative assignments in parentage analyses.     

Variation in the uptake of Arsenic, Cadmium, Lead, and Zinc by different species of willows Salix spp. grown in contaminated soils

The experiment assessed the variability of in seven clones of willow plants of high biomass production (Salix smithiana S-218, Salix smithiana S-150, Salix viminalis S-519, Salix alba S-464, Salix ’Pyramidalis’ S-141, Salix dasyclados S-406, Salix rubens S-391). They were planted in a pots for three vegetation periods in three soils differing in the total content of risk elements. Comparing the calculated relative decrease of total metal contents in soils, the phytoextraction potential of willows was obtained for cadmium (Cd) and zinc (Zn), moderately contaminated Cambisol and uncontaminated Chernozem, where aboveground biomass removed about 30% Cd and 5% Zn of the total element content, respectively. The clones showed variability in removing Cd and Zn, depending on soil type and contamination level: S. smithiana (S-150) and S. rubens (S-391) demonstrated the highest phytoextraction effect for Cd and Zn. For lead (Pb) and arsenic (As), the ability to accumulate the aboveground biomass of willows was found to be negligible in both soils. The results confirmed that willow plants show promising results for several elements, mainly for mobile ones like cadmium and zinc in moderate levels of contamination. The differences in accumulation among the clones seemed to be affected more by the properties of clones, not by the soil element concentrations or soil properties. However, confirmation and verification of the results in field conditions as well as more detailed investigation of the mechanisms of cadmium uptake in rhizosphere of willow plants will be determined by further research.     

Allometric scaling relationship between above‐ and below‐ground biomass within and across five woody seedlings

Allometric biomass allocation theory predicts that leaf biomass (M_L) scaled isometrically with stem (M_S) and root (M_R) biomass, and thus above‐ground biomass (leaf and stem) (M_A) and root (M_R) scaled nearly isometrically with below‐ground biomass (root) for tree seedlings across a wide diversity of taxa. Furthermore, prior studies also imply that scaling constant should vary with species. However, litter is known about whether such invariant isometric scaling exponents hold for intraspecific biomass allocation, and how variation in scaling constants influences the interspecific scaling relationship between above‐ and below‐ground biomass. Biomass data of seedlings from five evergreen species were examined to test scaling relationships among biomass components across and within species. Model Type II regression was used to compare the numerical values of scaling exponents and constants among leaf, stem, root, and above‐ to below‐ground biomass. The results indicated that M_L and M_S scaled in an isometric or a nearly isometric manner with M_R, as well as M_A to M_R for five woody species. Significant variation was observed in the Y‐intercepts of the biomass scaling curves, resulting in the divergence for intraspecific scaling and interspecific scaling relationships for M_L versus M_S and M_L versus M_R, but not for M_S versus M_R and M_A versus M_R. We conclude, therefore, that a nearly isometric scaling relationship of M_A versus M_R holds true within each of the studied woody species and across them irrespective the negative scaling relationship between leaf and stem.     

内蒙古草原大针茅群落地上生物量与降水量的关系

根据中国科学院内蒙古草原生态系统定位研究站在大针茅样地(面积500m×500m,地理坐标43°32′20″～43°32′40″N116°33′00″～116°33′30″E)的地上生物量与气候观测资料,利用SPSS分别进行大针茅群落地上生物量与年降水量、月降水量关键时期(4～6月份与6～8月份)降水量以及1～7月份总降水量的相关分析;对年降水量接近的1982、1983和1989年(分别为283.2mm,289.9mm,287.2mm)的地上生物量进行方差分析;运用积分回归模型模拟了降水的季节分配对群落生物量的影响。结果表明:(1)群落生物量的年际变化与年降水、月降水、关键时期降水(4～6月份和6～8月份)以及1～7月份降水量的变化没有显著的相关性(p>0.1);(2)在年降水量接近的年份,群落的地上生物量之间存在显著差异。降水量季节分配的变化对地上生物量的影响还有待于进一步研究。     

光照强度对8种红树植物幼苗生长和生物量分配的影响

选取无瓣海桑(Sonneratia apetala Buch-Ham.)、卤蕨(Acrostichum aureum Linn.)、桐花树(Aegiceras corniculatum Blanco.)、老鼠簕(Acanthus ilicifolius Linn.)、木榄(Bruguiera gymnorrhiza Lam.)、秋茄(Kandelia candel Druce.)、银叶树(Heritiera littoralis Ait.)和黄槿(Hibiscus tiliaceus L.)为研究对象,通过遮荫控制实验,研究这8种红树植物幼苗在不同光照强度(自然光强的100%、45%、30%、10%)下的生长和生物量分配特征。结果表明:(1)遮荫对无瓣海桑幼苗相对生长速率、生物量积累、基径的增长和叶片数的增长均有显著的抑制作用;(2)桐花和老鼠簕在遮荫处理下生长状况较好,遮荫对桐花生长的影响不显著,对老鼠簕幼苗的生长则有一定的促进作用;(3)当光照强度降低时,无瓣海桑、秋茄、老鼠簕、桐花树的幼苗都对地上部分投入了更多的生物量,其中秋茄、老鼠簕和桐花树通过提高叶生物量来获取更大的光能捕获能力。研究结果表明,从对光照的生长适应角度来看,桐花、老鼠簕和卤蕨适宜种植在郁闭度较高的林下;秋茄适宜在郁闭度较低的林下种植;真红树无瓣海桑和木榄以及半红树黄槿和银叶树则不适合在林下种植。     

Grain size affects the relationship between species richness and above-ground biomass in semi-arid rangelands

ABSTRACT

Background: Discrepancies in the shape of the productivity–diversity relationship may arise from differences in spatial scale. We hypothesised that there is a grain size effect on the productivity–diversity relationship.

Aims: To determine the effect of three sampling grain sizes on the productivity–diversity relationship.

Methods: We applied generalised linear mixed effect models on community data from 735 vegetation plots in the Taleghan rangelands, Iran, sampled at three grain sizes (0.25, 1 and 2 m²) to ascertain plant productivity-diversity patterns, while accounting for the effects of site, plant community type, disturbance, and life form.

Results: Overall, relationships between biomass and plant species richness were unimodal at grain sizes of 0.25 and 1 m², and asymptotical at 2 m². The spurious occurrence of a single large shrub may overwhelm a small-sized sampling unit, resulting in a high estimate of the sample’s biomass relative to species richness. However, the relationship between biomass and species richness at larger grain sizes is more likely to reach an asymptote.

Conclusions: Shrubs are partly responsible for driving the relationship between plant biomass and species richness. Given that the frequency of shrubs is highly variable between small plots but not so in large plots, their presence may result in unimodal productivity–diversity relationships at small but not at large grain sizes.     

Soil fungal and bacterial responses to conversion of open land to short‐rotation woody biomass crops

Short‐rotation woody biomass crops (SRWCs) have been proposed as an alternative feedstock for biofuel production in the northeastern US that leads to the conversion of current open land to woody plantations, potentially altering the soil microbial community structures and hence functions. We used pyrosequencing of 16S and 28S rRNA genes in soil to assess bacterial and fungal populations when ‘marginal’ grasslands were converted into willow (Salix spp.) and hybrid poplar (Populus spp.) plantations at two sites with similar soils and climate history in northern Michigan (Escanaba; ES) and Wisconsin (Rhinelander; RH). In only three growing seasons, the conversion significantly altered both the bacterial and fungal communities, which were most influenced by site and then vegetation. The fungal community showed greater change than the bacterial community in response to land conversion at both sites with substantial enrichment of putative pathogenic, ectomycorrhizal, and endophytic fungi associated with poplar and willow. Conversely, the bacterial community structures shifted, but to a lesser degree, with the new communities dissimilar at the two sites and most correlated with soil nutrient status. The bacterial phylum Nitrospirae increased after conversion and was negatively correlated to total soil nitrogen, but positively correlated to soil nitrate, and may be responsible for nitrate accumulation and the increased N₂O emissions previously reported following conversion at these sites. The legacy effect of a much longer grassland history and a second dry summer at the ES site may have influenced the grassland (control) microbial community to remain stable while it varied at the RH site.     

水分梯度上放牧对内蒙古主要草原群落功能群多样性与生产力关系的影响

应用样线法对放牧对内蒙古草原沿水分梯度分布的主要植物群落:小针茅(Stipaklemenzii)群落、大针茅(Stipagrandis)群落、羊草(Leymuschinensis)群落和羊草杂类草群落多样性、生产力以及两者关系的影响进行了研究,结果表明,除羊草杂类草群落外,物种多样性、生活型多样性和水分生态类型多样性随放牧强度的加大而降低,但适度放牧增加了羊草杂类草群落的上述多样性指标。群落地上现存量一般随放牧强度的增大而下降,但小针茅群落反之,主要与1年生植物猪毛菜(Salsolacollina)的生物量迅速增加有关。除羊草群落外,其他群落0～10cm地下生物量随放牧强度的变化不显著;放牧显著降低羊草群落和羊草杂类草群落0～30cm地下生物量。多样性和生产力间的关系在群落水平上的趋势是不同的,但放牧影响下内蒙古草原4种群落多样性与生产力总体而言呈线性增加关系;同时两者之间的关系还和采用哪种多样性指标和生产力指标有关,用水分生态类型多样性比物种多样性更能反映与地上地下总生产力间的关系,得到放牧影响下内蒙古草原植物群落地上地下总生物量与水分生态类型多样性的回归方程。     

Characterization of structural variability sheds light on the specificity determinants of the interaction between effector domains and histone tails

Structural characterization of the interaction between histone tails and effector modules (bromodomains, chromodomains, PHD fingers, etc.) is fundamental to understand the mechanistic aspects of epigenetic regulation of gene expression. In recent years many researchers have applied this approach to specific systems, thus providing a valuable but fragmentary view of the histone-effector interaction. In our work we use this information to characterize the structural features of the two main components of this interaction, histone peptides and the binding site of effector domains (focusing on those which target modified lysines), and increase our knowledge on its specificity determinants. Our results show that the binding sites of effectors are structurally variable, but some clear trends allow their classification in three main groups: flat-groove, narrow-groove and cavity-insertion. In addition, we found that even between within these classes binding site variability is substantial. These results in context with the work from other researchers indicate that the there are at least two determinants of binding specificity in the binding site of effector modules. Finally, our analysis of the histone peptides sheds light on the structural transition experienced by histone tails upon effector binding, showing that it may vary depending on the local properties of the sequence stretch considered, thus allowing us to identify an additional specificity determinant for this interaction. Overall, the results of our analysis contribute to clarify the origins of specificity: different regions of the binding site and, in particular, differences in the disorder-order transitions experienced by different histone sequence stretches upon binding.     

青海省高寒灌丛物种多样性、生物量及其关系

物种多样性对生态系统功能的作用是生物多样性研究的核心领域之一,生物量水平是生态系统功能的重要表现形式,而植物群落的生物量则是生态系统生物量的基础,因此研究植物群落物种多样性与生物量的关系,对于阐明植物多样性对生态系统功能的作用具有重要意义。通过对青海省高寒灌丛生物量、灌丛物种多样性特征以及与生物量的关系调查,得到以下结果:(1)被调查灌木植被群落的40个样地中共出现了207种植物(其中灌木植物18种,草本植物189种),隶属于130属,43科,灌木以蔷薇科、杜鹃花科为主,而草本以菊科、龙胆科、毛茛科和莎草科占优势。(2)群落多样性指数偏低,植物群落结构简单,物种组成稀少。小叶金露梅群落的多样性指数最大,金露梅群落、细枝绣线菊群落和鲜卑花群落次之,百里香杜鹃+头花杜鹃群落最低。(3)不同高寒灌丛类型生物量介于1893.03—7585.41 g/m~2之间,平均值为3775.9 g/m2,其中灌木生物量占灌丛总生物量的73.55%,草本为26.45%。(4)总生物量随草本物种多样性和群落物种多样性的增加而减小;草本生物量随其物种多样性的增加而减小,而灌木物种多样性与其生物量并无显著相关性。     

光强和光质对野外栽培高山红景天生物量和红景天甙含量的影响

为探讨野外条件下光强及光质对高山红景天 (Rhodiola sachalinensis)生物量和红景天甙含量的影响 ,于 2 0 0 1年 5月 8日至 9月 16日在大兴安岭加格达奇的高山红景天种植圃地 ,利用纱布及红色、蓝色和绿色的滤光膜遮光处理 ,对生长 3a和 4 a的高山红景天进行了光强、光质控制实验。与温室实验类似 ,遮荫显著抑制高山红景天根的生长 ,并使红景天甙的含量略有提高。红膜处理使光强大约降低一半 ,但仅从光质的角度而言 ,红膜处理对根的生长影响不大 ,却显著增加了根中的红景天甙含量和产量 ,不过效果不如温室实验明显。绿膜处理未表现出对红景天甙积累的促进作用 ,这与温室实验结果不同。红膜处理不同天数的结果表明 ,处理时间对红景天甙含量提高的程度影响很小。这意味着在野外种植的情况下 ,可以在临近收获的最后一段时间用红膜对高山红景天进行处理 ,这样既可避免红膜处理对高山红景天根生长的抑制 (由于减弱了光照 ) ,又可显著提高根的红景天甙含量 ,从而达到大幅度提高红景天甙产量的目的。