Local genetic structure in the critically endangered,cave‐associated perennial herb Primulina tabacum (Gesneriaceae)

The local spatial genetic structures of cave‐associated plants are seldom studied. Given that these plants are mainly confined to small areas in and around the entrances of caves, we hypothesized that they might lack genetic structures at local scales. To test this hypothesis, we sampled two large populations (named D and T) of a critically endangered perennial herb, Primulina tabacum, which is endemic to karst caves in southern China. We analysed nine microsatellite loci and sequenced four chloroplast DNA (cpDNA) intergenic spacer regions to study the genetic diversity and structure within and between both populations. Both populations have distinct genetic characteristics. Samples from two subpopulations in population D showed considerable genetic divergence. This is not consistent with the hypothesis that P. tabacum has a weak genetic structure at a local scale. However, 94% of the individuals in population T shared the same multilocus genotype, which indicates little genetic structure within this population. The contributions of seed flow, pollen flow and (sub)population history to the genetic diversity and structure in each and both populations are discussed. Our study is the first to investigate local genetic diversity and structure in a cave‐associated plant, and provides valuable information for the sustainable conservation of such species. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 747–756.     

Induction of systemic resistance against Fusarium crown and root rot disease by blast processing

The effect of fan-forced wind on the severity and growth of Fusarium oxysporum f. sp. radicis-lycopersici (FORL) was examined in this study. The discoloration severity of the total root system was significantly reduced in plants treated with air blasting for 30?min at a wind speed of 4?m/s compared with the control. In addition, the number of colony-forming units of FORL per gram of fresh root weight was significantly reduced (p?≤?0.05) in plants treated with air blasting at a wind speed of 4?m/s for 30?min, and the root extracts of these plants had a significantly lower production of FORL budding cells. Booster wind treatments significantly reduced the severity and growth of FORL compared with single and control treatments. Furthermore, RT-PCR analysis indicated that the expression of defense-related genes was induced in the leaves of seedlings treated with air blasting at a wind speed of 4?m/s.     

Invasions by alien plant species of the agro-pastoral ecotone in northern China: Species-specific and environmental determinants

The establishment, reproduction, dispersal, and distribution of alien plants are affected by various factors during the transition from being newly introduced in a habitat to being invasive. In the agro-pastoral ecotone of northern China, comprising farmlands and natural grasslands, the biological characteristics of alien plant species were the key intrinsic factors (propagation characteristics and competitive ability), followed by such extrinsic factors as human interference and environmental heterogeneity. Among biological characteristics, the life form may be an important and useful indicator of the invasive ability of a species, and the risk of invasion is greater from alien species that are poisonous, inedible, and have traits that facilitate wide dispersal. Farmlands may serve as initial shelters for alien species, from which they spread into neighbouring habitats, whereas natural grassland may act as a barrier to plant invasions. Management practices detrimental to grasslands, including overgrazing, reclamation, and road construction, often facilitate the invasions; therefore, counter measures such as reseeding and a ban on grazing need special attention. Environmental factors including precipitation, nutrients, prevailing winds, fires, and topography may be other factors that promote or block the process of invasion. In studying ways of preventing or controlling such invasions, alien plants with short life cycle, prolific seed production, and strong competitiveness, deserve particular attention and so do human activities that may damage the environment and fragile habitats.     

内蒙古土地利用变化对生态系统防风固沙功能的影响

土壤风蚀是内蒙古的严重环境问题之一。在对内蒙古2000年到2010年的土地利用变化特征进行分析的基础上,分析了内蒙古土地利用变化的主要特征,以RWEQ模型估算了内蒙古2000年和2010年的固沙物质量,采用空间统计分析评估了固沙功能对土地利用变化的响应,结果表明:(1)2000—2010年土地利用变化以城镇高速发展、草地和湿地面积锐减、林地灌丛有所恢复以及荒漠环境改善为主要特征。(2)2000—2010的十年间内蒙古固沙物质总量增长了17.75%,草地总面积虽有所降低,但是部分区域草地覆盖度的上升增强了草地固沙能力,而林地的固沙物质量则由于农田、草地改为林地的短期内地表保护力的下降而有所降低。(3)十年间农田退耕还草、荒漠环境的改善、草地质量提高等土地利用变化方式有益于生态环境质量的提高,使生态防风固沙功能得以增强,造成固沙物质量提高了约0.25亿t。(4)农田开垦、城镇发展、荒漠化发展、湿地萎缩以及草地的退化等土地利用变化会使生态环境质量降低,生态系统防风固沙功能下降,累计造成的固沙物质量的减少总量约为0.19亿t。从十年间综合来看,内蒙古的土地利用变化对区域固沙功能有一定的增强作用,但是尚存在城镇发展过快、草地湿地转化压力过大、草地退化、荒漠化对固沙功能的弱化问题,需要在今后的土地利用规划和管理工作中予以改进以进一步增强区域固沙功能,构建北方地区生态安全屏障。     

Adverse wind conditions during northward Sahara crossings increase the in‐flight mortality of Black‐tailed Godwits

Long‐distance migratory flights are predicted to be associated with higher mortality rates when individuals encounter adverse weather conditions. However, directly connecting environmental conditions experienced in‐flight with the survival of migrants has proven difficult. We studied how the in‐flight mortality of 53 satellite‐tagged Black‐tailed Godwits (Limosa limosa limosa) during 132 crossings of the Sahara Desert, a major geographical barrier along their migration route between The Netherlands and sub‐Saharan Africa, is correlated with the experienced wind conditions and departure date during both southward and northward migration. We show that godwits experienced higher wind assistance during southward crossings, which seems to reflect local prevailing trade winds. Critically, we found that fatal northward crossings (15 deaths during 61 crossings) were associated with adverse wind conditions. Wind conditions during migration can thus directly influence vital rates. Changing wind conditions associated with global change may thus profoundly influence the costs of long‐distance migration in the future.     

基于“风感”的紧凑型城市开放空间风环境实测和CFD模拟比对研究

城市开放空间的风场不仅影响微环境的"风感"舒适度还影响宏观尺度的城市气候。从景感生态学的角度出发,首先阐述"风感"的定义,总结了街道峡谷空间风场的基本规律和特点。运用Kestrel NK4500手持气象站对城市开放空间的风环境进行实测,采用CFD(Computational Fluid Dynamics)模拟软件Fluent 14.0对不含绿地的同一空间进行风环境模拟,通过两者的数据比对来研究紧凑型城市开放空间内绿地对行人高度风场的实际干扰程度。结果发现,紧凑型城市开放空间的"风感"受建筑和绿地空间布局的共同影响。当建筑高于绿地时,风场受建筑的控制;当林带高于建筑时,林带对风环境的影响程度受其疏密度影响。疏密度较高的常绿林带对风向和风速影响很大,而疏密度较低的林带会影响风速,对风向影响不大。影响风速的主要因素是空间围合所形成的空气域,相比实体、多孔介质,空气域对风的阻力要小的多。如铺装、草坪上方的通风廊道是影响行人高度层通风、导风的关键因素。紧凑型空间内的绿地在行人高度应保持通畅以保证通风,并通过建立平面和竖向上的通风、导风廊道体系,促进空气循环。     

冻融作用对土壤理化性质及风水蚀影响研究进展

冻融侵蚀在我国分布范围广,是主要土壤侵蚀类型之一,而冻融作用与其他营力复合进行侵蚀的分布范围比单纯的冻融侵蚀更广,所造成的危害也更大.本文基于国内外已有研究成果,总结评述了冻融作用对土壤理化性质及风蚀和水蚀影响的相关研究进展.冻融条件下,土壤水分发生运移,结构被破坏,土壤孔隙度、容重、抗剪强度、团聚体稳定性和有机质等理化性质均发生变化,其变化趋势和幅度与土壤质地、冻融程度有关.冻融作用通过改变土壤理化性质,增加土壤可蚀性,从而影响土壤风蚀和水蚀发生及过程,导致侵蚀强度增大.目前,冻融研究以室内模拟为主,与野外实际冻融过程差异较大,且由于试验条件不同,得到的结论无法统一,甚至相反.因此,通过室内模拟与野外实测相结合,加强冻融条件下土壤侵蚀机理研究是下一步的重点,这对季节性冻融区解冻期侵蚀预报和防治具有重要意义.     

樟子松固沙林林水关系研究进展及对营林实践的指导

中国有着世界上最大面积的人工林, 如何维持人工林的可持续性已成为气候变化背景下需要面对的重大挑战。樟子松(Pinus sylvestris var. mongolica)以其抗旱、抗寒、耐贫瘠等优良特性成为中国北方生态治理中最主要的常绿针叶树种之一, 近70年来发挥了巨大的防风固沙与生态固碳功能。然而, 随着林分的生长与气候变化, 樟子松人工固沙林正经历着越来越严峻的环境胁迫, 部分地区出现了林分“早衰”或死亡的现象, 引起了人们对樟子松固沙林适应与应对气候变化能力的担忧。该文在回溯樟子松基本生物学特征与引种推广历史, 系统总结近年来樟子松林林水关系研究新成果的基础上, 全面分析了樟子松固沙林林水关系存在的主要矛盾, 并提出了基于林水关系相协调的林分经营措施的调整: 由倡导防护功能为主的单一目标向包含林分稳定性、生态固碳功能、可持续发展等多目标平衡方向调整; 由以沙地森林景观培育为主向以良好土壤生境培育为主的方向调整; 由倡导天然更新为主向以人工造林与天然更新相结合的世代更新方向调整。在立足于北方沙地脆弱生境与气候变化客观现实的基础背景下, 应坚持樟子松在固沙林生态系统演化过程中的先锋种与建群种地位, 基于“以水定绿”原则, 采取“隔行带伐+再造林”等方式开展林分密度动态调控, 促进林分向异龄林结构演化, 促进樟子松固沙林生态服务的优质化和生态固碳功能的最大化。     

Reliability of ultrasound speckle tracking with singular value decomposition for quantifying displacement in the carpal tunnel

Inhibited movement patterns of carpal tunnel structures have been found in carpal tunnel syndrome (CTS) patients. Motion analysis on ultrasound images allows us to non-invasively study the (relative) movement of carpal tunnel structures and recently a speckle tracking method using singular value decomposition (SVD) has been proposed to optimize this tracking. This study aims to assess the reliability of longitudinal speckle tracking with SVD in both healthy volunteers and patients with CTS.Images from sixteen healthy volunteers and twenty-two CTS patients were used. Ultrasound clips of the third superficial flexor tendon and surrounding subsynovial connective tissue (SSCT) were acquired during finger flexion-extension. A custom made tracking algorithm was used for the analysis. Intra-class correlation coefficients (ICCs) were calculated using a single measure, two-way random model with absolute agreement and Bland-Altman plots were added for graphical representation.ICC values varied between 0.73 and 0.95 in the control group and 0.66–0.98 in the CTS patients, with the majority of the results classified as good to excellent. Tendon tracking showed higher reliability values compared to the SSCT, but values between the control and CTS groups were comparable.Speckle tracking with SVD can reliably be used to analyze longitudinal movement of anatomical structures with different sizes and compositions within the context of the carpal tunnel in both a healthy as well as a pathological state. Based on these results, this technique also holds relevant potential for areas where ultrasound based dynamic imaging requires quantification of motion.