Revegetation Methods for High-Elevation Roadsides at Bryce Canyon National Park, Utah

Establishment of native plant populations on disturbed roadsides was investigated at Bryce Canyon National Park (BCNP) in relation to several revegetation and seedbed preparation techniques. In 1994, the BCNP Rim Road (2,683–2,770 m elevation) was reconstructed resulting in a 23.8‐ha roadside disturbance. Revegetation comparisons included the influence of fertilizer on plant establishment and development, the success of indigenous versus commercial seed, seedling response to microsites, methods of erosion control, and shrub transplant growth and survival. Plant density, cover, and biomass were measured 1, 2, and 4 years after revegetation implementation (1995–1998). Seeded native grass cover and density were the highest on plots fertilized with nitrogen and phosphorus, but by the fourth growing season, differences between fertilized and unfertilized plots were minimal. Fertilizers may facilitate more rapid establishment of seeded grasses following disturbance, increasing soil cover and soil stability on steep and unstable slopes. However the benefit of increased soil nutrients favored few of the desired species resulting in lower species richness over time compared to unfertilized sites. Elymus trachycaulus (slender wheatgrass) plants raised from indigenous seed had higher density and cover than those from a commercial seed source 2 and 4 years after sowing. Indigenous materials may exhibit slow establishment immediately following seeding, but they will likely persist during extreme climatic conditions such as cold temperatures and relatively short growing seasons. Seeded grasses established better near stones and logs than on adjacent open microsites, suggesting that a roughened seedbed created before seeding can significantly enhance plant establishment. After two growing seasons, total grass cover between various erosion‐control treatments was similar indicating that a variety of erosion reduction techniques can be utilized to reduce erosion. Finally shrub transplants showed minimal differential response to fertilizers, water‐absorbing gels, and soil type. Simply planting and watering transplants was sufficient for the greatest plant survival and growth.     

The bryophyte diaspore bank and its role after small-scale disturbance in a boreal forest

Abstract. The composition of the bryophyte diaspore bank in an old-growth Picea abies forest was studied before and after experimental disturbance of forest-floor patches. 40 species, both hepatics and mosses, emerged from spores, and probably also from gemmae and moss fragments, in greenhouse cultivations of soil samples. The three most abundant taxa were Pohlia nutans, Sphagnum spp. and Polytrichum commune/longisetum. Initially, the number of species from the diaspore bank in mineral soil, 9.9 species/sample, was higher than that in humus, 6.6. Four years after the disturbance took place, the reverse was found. Several species that are typical colonisers of disturbed soil were very common in the diaspore bank. By contrast, some of the most abundant forest floor species appeared to be absent. The diaspore bank of bryophytes appears to play a role similar to that of the seed bank in vascular plants: (1) it allows species to survive unfavourable periods (temporal dispersal); (2) it facilitates rapid colonisation after disturbance; (3) it influences the post-disturbance species composition and diversity. The results emphasise that the understanding of vegetation succession patterns is, to a large extent, dependent on quantitative data on the relative importance of spatial and temporal dispersal.     

小麦叶锈病新抗源筛选

小麦叶锈病是小麦生产的主要病害之一,发病严重时往往导致大幅度减产。叶锈菌生理小种的变异易导致抗病基因抗性的丧失,因此不断获得新抗源对小麦抗病育种至关重要。小麦近缘植物中含有丰富的小麦育种所需的抗病基因。本研究从小麦-近缘植物双二倍体、附加系、代换系或易位系等创新种质中筛选出小麦叶锈病新抗源,为利用这些新抗源打下基础。苗期对116份供试材料人工接种美国堪萨斯州流行的小麦叶锈菌混合生理小种 (Lrcomp) ,其中部分材料人工接种09-9-1441-1等5个中国当前流行的叶锈菌生理小种进行抗性鉴定,筛选获得新抗源。116份种质中,31份免疫、近免疫或高抗Lrcomp。含有希尔斯山羊草、尾状山羊草、拟斯卑尔脱山羊草、两芒山羊草、卵穗山羊草、沙融山羊草、柱穗山羊草、顶芒山羊草、小伞山羊草、偏凸山羊草、中间偃麦草、茸毛偃麦草、长穗偃麦草、粗穗披碱草、栽培黑麦、非洲黑麦、提莫菲维染色质的部分种质免疫或高抗Lrcomp,而含二角山羊草、无芒山羊草、沙生冰草、多年生簇毛麦和一年生簇毛麦染色质的种质表现中感至高感Lrcomp。希尔斯山羊草4S染色体、尾状山羊草C#1和D#1染色体和两芒山羊草、顶芒山羊草中可能含有未被报道的抗Lrcomp的新基因,值得进一步向小麦转育。小麦-粗穗披碱草1HtS.1BL罗伯逊易位系对Lrcomp及 09-9-1441-1和09-9-1426-1等5个中国当前流行叶锈菌生理小种近免疫,值得利用染色体工程等方法获得小片段抗病易位系应用于我国小麦抗叶锈育种。     

光照强度和肥力变化对垂穗披碱草生长的影响

在野外条件下,采用析因设计,对光照和肥力变化影响下垂穗披碱草的生长参数进行测定,评估垂穗披碱草对异质环境的适应特性。光照分为高光照(100%光照强度)、中度光照(43.5%光照强度)与低光照(6.74%光照强度);肥力分为施肥与不施肥。结果表明,垂穗披碱草在光照强度由高光照(100%)向中度光照(43.5%)变化情况下,地上生物量、分蘖数无变化,株高增大,光照强度减小到6.74%时,地上生物量、分蘖数、株高均减小。比叶面积(SLA)随光照强度的减弱而增加,相对生长率(RGR)随光照强度的减弱而减小,施肥对SLA和RGR无影响。根冠比在中度光照和低光照下各处理之间差异均不显著,高光照(100%)下增加肥力,根冠比增大。施肥时,叶分配随光照强度的减弱而增加,繁殖分配减小,不施肥时,叶分配与繁殖分配在高光照(100%)和中度光照(43.5%)下无差异,低光照(6.74%)下,叶分配增大,繁殖分配减小。施肥时茎分配在中度光照强度(43.5%)下最大,高光照强度(100%)下次之,低光照强度(6.74%)下最小,不施肥时,茎分配在高光照(100%)和中度光照(43.5%)下无差异,低光照(6.74%)下减小。研究表明:垂穗披碱草是一个光照耐受型物种,光照强度减小到全光照一半时仍可正常生长。在低光环境中,垂穗披碱草通过增加株高和大而薄的叶片,来适应环境,资源主要在叶分配、茎分配、繁殖分配之间进行了权衡。     

下垂虫草的重寄生现象及重寄生菌的鉴定

在安徽省岳西县鹞落坪自然保护区,发现了1种寄生于下垂虫草(Ophiocordyceps nutans)的重寄生菌。通过形态特征观察和ITS序列分子生物学分析,将其鉴定为枝多头霉(Polycephalomyces ramosus)。其孢梗束着生于下垂虫草子实体的可孕部,顶部膨大呈球形。本种具有产生单个卵形的A型分生孢子的顶侧生排列的A型瓶梗和能形成分生孢子链的B型瓶梗,并在培养基上的气生菌丝和孢梗束的柄部都观察到梭形、链生的B型分生孢子。GenBank中相关种的ITS序列与拉丁名可能有误。     

野生垂穗鹅观草醇溶蛋白遗传多样性研究

利用酸性聚丙烯酰胺凝胶电泳(Acid-polyacrylamidegel electrophoresis)法对来源于内蒙古、山西、甘肃、新疆、云南、四川和西藏的25份垂穗鹅观草材料进行醇溶蛋白检测。研究结果表明,供试材料可分离出30条相对迁移率不同的谱带,每份材料可电泳出11～22条谱带,其中只有1条(3.45%)带纹是25份材料共有的,其余29条谱带均具有不同程度的多态性,多态性谱带数目占分离出总条带的96.67%,说明野生垂穗鹅观草具有较丰富的遗传多样性。聚类分析发现,材料的遗传相似系数(GS)变异范围为0.111～0.9286,平均值为0.4821。在GS值为0.4821的水平上供试材料可聚为6个类群,某些具有相同地理来源的材料聚成一类或亚类,即醇溶蛋白图谱类型与材料的生态地理环境具有相关性。     

氮磷硅添加对青藏高原高寒草甸垂穗披碱草叶片碳氮磷的影响

以甘南高寒草甸常见牧草垂穗披碱草(Elymus nutans)为研究对象,比较不同氮磷硅添加下,垂穗披碱草叶片对元素添加的反应。研究发现:氮添加显著提高土壤中硝态氮和铵态氮的含量;磷添加提高了土壤中全磷和速效磷的含量;高浓度的硅单独、硅与氮或磷混合可提高土壤中硝态氮的含量或全磷和速效磷的含量;氮和磷单独添加分别能提高垂穗披碱草叶片全氮和全磷含量,高浓度的硅单独、硅与氮或磷混合添加都能提高垂穗披碱草叶片全氮和全磷的含量。就硅元素而言,高浓度的硅添加,硅与氮或磷混合添加能提高土壤硝态氮、全磷和速效磷的含量,促进垂穗披碱草对土壤中氮磷的吸收,从而使植物叶片中氮磷的含量增加。     

Physical mapping of repetitive sequences and genome analysis in six Elymus species by in situ hybridization

Genome constitution and genetic relationships between six Elymus species were assessed by physical mapping of different repetitive sequences using a technique of sequential fluorescence in situ hybridization and genomic in situ hybridization.The six Elymus species are all naturally growing species in northwest China,namely,E.sibiricus,E.nutans,E.barystachyus,E.xiningensis,E.excelsus,and E.dahuricus.An StStHH genome constitution was revealed for E.sibiricus and StStHHYY for the remainder species.Each chromosome could be clearly characterized by physical mapping with 18S-26S rDNA,5S rDNA,Afa-family,and AAG repeats,and be allocated to a certain genome by genomic in situ hybridization.Two 5S rDNA sites,each in the H and St genomes,and three 18S-26S rDNA sites,two in the St genome and one in the Y genome,were uncovered in most of the species.The strong Afa-family hybridization signals discriminated the H genome from the St and Y genomes.The H and Y genome carried more AAG repeats than St.A common non-Robertsonian reciprocal translocation between the H and Y genomes was revealed in E.barystachyus,E.xiningensis,E.excelsus and E.dahuricus.Comparison of molecular karyotypes strongly suggests that they can be classified into three groups,namely,E.sibiricus,E.nutans,and others.     

老芒麦和垂穗披碱草rDNA-ITS序列分析

分析了老芒麦和垂穗披碱草rDNA-ITS序列,为这两个种的鉴别提供分子指纹图谱,为系统发育提供分子生物学依据。结果表明,22份材料的ITS、ITS1、5.8S、ITS2序列长度均相同,依次为604bp、222bp、164bp、218bp,GC含量依次为62.25%～63.08%,62.16%～63.06%,59.76%,64.22%～65.60%。除5.8S外,碱基位点都有不同程度的变化,一些变异位点有明显的种性变异规律,可作为老芒麦和垂穗披碱草种质DNA指纹特异鉴别位点。7个ITS序列的同源性98.7%～99.8%,遗传分歧0.2～1.3,具有保守性,为非近期分化类群。系统发育分析表明不同来源地的同种材料,差异主要表现在DNA变化快慢及碱基替换数,但相同的种归为一类,进一步反映了种内的遗传稳定性。