不同除草剂的田间杂草防效及对糜子生长发育的影响

筛选糜子适宜除草剂来防范农田药害,是糜子高效安全生产和改善生态环境亟待解决的关键问题。本研究以粳性糜子品种‘榆糜2号'为材料,探究22种除草剂对糜子田间杂草的防除效果及对糜子生长发育的影响。结果表明: 1)喷施土壤封闭型除草剂谷友、丁草胺、莠去津、苄嘧·丙草胺和茎叶型除草剂苯唑·二甲钠、阔世玛、藤净、陶氏·优先、阔菲后,基本无药害作用,糜子幼苗生长正常,其余除草剂均对糜子有不同程度的药害影响;2)参试的22种除草剂在糜子田中对杂草均表现出一定的防除效果,总体而言,土壤封闭型除草剂的杂草防效相对优于茎叶型除草剂,但所有参试除草剂对糜子株高、功能叶片叶绿素含量、单株穗重均造成不同程度的影响;3)与人工除草相比,参试除草剂均导致糜子产量有不同程度的下降;但与不除草对照相比,部分除草剂有明显的增产增效作用。土壤封闭型除草剂中,谷友、丁草胺、莠去津、苄嘧·丙草胺的杂草防效较好,较不除草对照增产60%以上;茎叶型除草剂中,阔世玛、苯唑·二甲钠的杂草防效较好,较不除草对照增产50%以上。因此,在糜子出苗前可用38%莠去津或44%单嘧磺隆进行土壤封闭处理,或在出苗后喷施茎叶型除草剂3.6%二磺·甲碘隆或55%苯唑·二甲钠,农田杂草防效较好,且对糜子生长发育的负面影响较小。     

末次盛冰期以来观光木的潜在地理分布变迁

观光木(Tsoongiodendron odorum)是木兰科的古老残遗物种, 目前正面临严峻的生存威胁, 属于极小种群濒危植物。通过生态位模型(ENM)能够重建观光木地理分布格局的历史变迁, 探究气候变化对该物种分布的影响, 并了解其地理分布与气候需求间的关系, 从而为全球变暖背景下观光木的保护提供理论基础。该文基于96条现代分布记录和8个环境变量, 采用最大熵(MaxEnt)模型模拟观光木在末次盛冰期、全新世中期、现代和未来(2061-2080年, RCP 8.5)的潜在分布区, 利用SDM toolbox分析观光木的地理空间变化, 并综合贡献率、置换重要值和Jackknife检验来评估气候因子的重要性。研究结果表明: (1)观光木的高度适生区在南岭地区, 末次盛冰期时没有大尺度向南退缩, 很可能在山区避难所原地存活; (2)在全新世中期和未来两个增温的气候情境下, 观光木的分布区均表现为缩减, 其中未来分布的减幅更大, 表明气候变暖对观光木的生长有一定的负面影响; (3)总体上看, 观光木各个时期的地理分布范围相对稳定, 说明观光木对气候变化有一定的适应能力, 人为活动或自身繁育问题可能是致濒的重要原因, 并建议对广东和广西群体进行优先保护。     

生态系统服务功能与景观格局耦合协调度研究——以武陵山区退耕还林工程为例

生态系统服务功能与景观格局演变关系极为密切,研究生态系统服务功能与景观格局的耦合协调度对于区域发展具有重要意义。以武陵山区退耕还林工程为例,参照国家标准和行业标准,采用分布式测算方法、景观格局指数分析和耦合协调度模型等方法,旨在揭示武陵山区退耕还林工程生态系统服务功能与景观格局二者耦合协调关系。结果表明:(1)2005—2017年间武陵山区退耕还林工程各项生态服务功能物质量均以15倍左右速度增长,生态系统服务空间分布格局最佳区域由西部地区逐渐向东南扩大;(2)武陵山区景观演变存在时空差异,1995—2005年景观格局变化更为明显,变化区域集中在中西部地区,2005—2015年与之相比,景观格局变化空间上更为分散;(3)武陵山区退耕还林工程生态系统服务与景观格局演变存在较高水平的耦合以及高水平的协调性。研究结果可为武陵山区土地利用规划及退耕还林工程进一步实施提供科学依据。     

The complete chloroplast genome of Myriophyllum spicatum reveals a 4‐kb inversion and new insights regarding plastome evolution in Haloragaceae

Myriophyllum, among the most species‐rich genera of aquatic angiosperms with ca. 68 species, is an extensively distributed hydrophyte lineage in the cosmopolitan family Haloragaceae. The chloroplast (cp) genome is useful in the study of genetic evolution, phylogenetic analysis, and molecular dating of controversial taxa. Here, we sequenced and assembled the whole chloroplast genome of Myriophyllum spicatum L. and compared it to other species in the order Saxifragales. The complete chloroplast genome sequence of M. spicatum is 158,858 bp long and displays a quadripartite structure with two inverted repeats (IR) separating the large single copy (LSC) region from the small single copy (SSC) region. Based on sequence identification and the phylogenetic analysis, a 4‐kb phylogenetically informative inversion between trnE‐trnC in Myriophyllum was determined, and we have placed this inversion on a lineage specific to Myriophyllum and its close relatives. The divergence time estimation suggested that the trnE‐trnC inversion possibly occurred between the upper Cretaceous (72.54 MYA) and middle Eocene (47.28 MYA) before the divergence of Myriophyllum from its most recent common ancestor. The unique 4‐kb inversion might be caused by an occurrence of nonrandom recombination associated with climate changes around the K‐Pg boundary, making it interesting for future evolutionary investigations.     

Predation of potential insect pests in oil palm plantations,rubber tree plantations,and fruit orchards

In human‐modified landscapes, important ecological functions such as predation are negatively affected by anthropogenic activities, including the use of pesticides and habitat degradation. Predation of insect pests is an indicator of healthy ecosystem functioning, which provides important ecosystem services, especially for agricultural systems. In this study, we compare predation attempts from arthropods, mammals, and birds on artificial caterpillars in the understory, between three tropical agricultural land‐use types: oil palm plantations, rubber tree plantations, and fruit orchards. We collected a range of local and landscape‐scale data including undergrowth vegetation structure; elevation; proximity to forest; and canopy cover in order to understand how environmental variables can affect predation. In all three land‐use types, our results showed that arthropods and mammals were important predators of artificial caterpillars and there was little predation by birds. We did not find any effect of the environmental variables on predation. There was an interactive effect between land‐use type and predator type. Predation by mammals was considerably higher in fruit orchards and rubber tree than in oil palm plantations, likely due to their ability to support higher abundances of insectivorous mammals. In order to maintain or enhance natural pest control in these common tropical agricultural land‐use types, management practices that benefit insectivorous animals should be introduced, such as the reduction of pesticides, improvement of understory vegetation, and local and landscape heterogeneity.     

含氮有机物在污水处理过程中的生物转化机制与模型研究进展

随着市政污水处理厂的提标改造,出水总氮浓度逐渐降低,但溶解性有机氮(Dissolved Organic Nitrogen,DON)在总氮中的占比却越来越高,对含氮消毒副产物的生成和受纳水体富营养化的潜在贡献不可忽视。正因如此,近年来有关污水处理系统中DON的研究不断增加。本文重点综述了污水处理厂DON特征、生成转化规律及其生态影响。目前通过混凝沉淀、消毒等物理化学工艺的联合最高可去除70%左右的进水DON,但生物处理单元的微生物代谢活动会生成新的DON,主要包括氨基酸、聚胺等,其藻类生物可利用性较高。在已有DON模型基础上,本文提出了更加完善的ASM3-DON模型,纳入了包括内源呼吸、细胞生长、微生物产物再利用在内的6个过程,可用于对DON生成转化进行更加精确的模拟。未来围绕污水处理过程的DON研究应重点关注DON的快速精确定量分析、生成转化规律探究以及高效去除方法开发。     

途径特异性调控因子介导的链霉菌来源天然产物的产量提升

链霉菌是活性天然产物的重要来源。基因组学研究揭示了链霉菌有巨大的生物合成潜力,平均每株菌拥有20–40个生物合成基因簇。在常规的实验室条件下,大多数链霉菌来源的天然产物产量较低,影响了对其进一步研究和产业化开发。由于链霉菌中天然产物的生物合成受到严格的调控,对于这些调控因子和调控网络的深入研究将有力地促进链霉菌来源的天然产物的发现和开发利用。文中主要综述了近5年来链霉菌来源天然产物生物合成中途径特异性调控因子的研究进展,重点介绍其在提高相应天然产物产量中的应用。