Population dynamics of volunteer oilseed rape (Brassica napus L.) affected by tillage

Volunteer plants of oilseed rape (Brassica napus L.) from persistent seeds in soil can affect subsequent crops. Apart from the agricultural disadvantages, the environment and the marketing of the seeds may also be affected, particularly if plants with special ingredients or genetically modified (gm) plants are grown. In order to investigate the influence of soil cultivation and genotype on seed persistence and gene flow via volunteers, a field experiment was set up testing four tillage treatments and two cultivars in a split-plot design. The cultivars tested were near-isogenic to two gm cultivars. To simulate harvesting losses, 10 000 seeds m⁻² were broadcast on a soil in July. The subsequent tillage treatments were combinations of immediate or delayed stubble tillage by a rotary tiller, primary tillage with plough or cultivator, or zero tillage. Over the following year, the fate of the seeds was determined. Immediate stubble tillage with following cultivator or plough resulted in 586 resp. 246 seeds m⁻² in the soil seed bank. After delayed stubble tillage with following plough, 76 seeds m⁻² were found, and no soil seed bank was built up in the zero tillage treatment. Nevertheless, in the zero tillage treatment, several robust volunteer plants survived the herbicide application before the direct drilling in autumn until following spring. In the zero tillage treatment and in the cultivator treatment, 0.19 volunteers m⁻² resp. 0.06 volunteers m⁻² flowered simultaneously to ordinarily sown oilseed rape in the following crop of winter wheat and produced 73 resp. 18 seeds m⁻². Delayed stubble tillage reduced the risk of gene escape via the soil seed bank, while zero tillage resulted in the highest risk of gene escape by pollen and by production of a new generation of seeds. In terms of a labelling threshold for gm food this number of seeds would be below the threshold of 0.9% of transgenic parts in conventially bred food or feed.     

高校图书馆志愿者管理模式探析

从高校图书馆引入志愿者管理流程着手,对志愿者管理机构、招募选拔、培训指导、绩效评估、激励机制、终止关系等方面进行分析;提出志愿者管理的协同管理原则、激励管理原则、动态调整原则和延展性原则;制定志愿者管理方法即合同管理、积分管理、人文关怀和信息保密。     

Emergence and performance of volunteer oilseed rape (Brassica napus) in different crops

Volunteer oilseed rape (OSR, Brassica napus L.) causes various agronomic problems in crop rotations and can contribute to gene dispersal by pollen and by seed admixture. A 4-year field experiment (2008–2011) was set up in south-west Germany to investigate the performance of volunteers derived from two OSR cultivars with different levels of seed dormancy. Volunteers of a high-dormancy (HD) and a low-dormancy (LD) OSR cultivar were deliberately generated by spreading 10,000 seeds m⁻² on a field in August 2008 and 2009. Four different crops were grown on that area in the first year following the seed rain: winter wheat (Triticum aestivum L.), winter turnip rape (Brassica rapa L.), spring barley (Hordeum vulgare L.) and field pea (Pisum sativum L.). In the second year, maize (Zea mays L.) was sown uniformly across all plots. Numbers of OSR seedlings emerging in early autumn shortly after seed rain were not connected with the size of the soil seed bank in early spring of the following year. The seeds of the HD-cultivar formed a much greater soil seed bank (up to 14% of the initially spread seed number) compared with the LD-cultivar (up to 1.3%) in the soil layer of 0 to 30 cm in early spring 2009 and 2010). Across all crops, considerably more volunteers of the HD-cultivar than of the LD-cultivar were present at several survey dates in the first year following seed rain. The highest number of volunteers originated from the HD-cultivar with up to 11 volunteers m⁻² in winter turnip rape compared with a maximum of 0.48 plants m⁻² in the other crops. Cultivar-specific differences in volunteer density were observed as well in maize two years after OSR seed rain. Flowering and seed setting volunteers were only present in 2010 and the flowering time was crucially overlapping with that of sown winter OSR. The reproductive ability (seeds produced m⁻²) of the LD-volunteers was five times lower in winter turnip rape than of the HD-volunteer; a similar trend was observed for the OSR volunteers in the other host crops.Strategies to definitely reduce unwanted effects of OSR volunteers, such as gene flow, should include the use of LD-cultivars with a low potential to form a soil seed bank, particularly if selective herbicides are not available, for instance in broad-leaved crops, or if the volunteers are herbicide-tolerant.     

Propensity for seed-mediated gene flow from potato crops and potential consequences for the coexistence of GM and non-GM potato systems

Potato is a critical crop to European growers, both economically and agronomically as a break crop in the standard cereal rotation. As studies investigating the agronomic performance and environmental impact of disease resistant, GM potatoes come to an end across several sites in Europe, past discussions on achieving the effective coexistence of GM and equivalent non-GM crops have too often focussed on the purported risk of excessive pollen-mediated gene flow. Dependent on the crop in question, the impact of seed loss pre- and/or post-harvest presents a greater challenge to securing efficient coexistence practises. To examine this issue for potato, a total of 51 fields that had been commercially cultivated with potatoes were surveyed in two separate cohorts for post-harvest tuber loss and/or volunteer emergence. Across 17 fields studied, the average post-harvest tuber loss was recorded at 141,758 ± 911 tubers ha⁻¹, with volunteer establishment in the following crop ranging from 400 ± 59 ha⁻¹ to 55,698 ± 47 ha⁻¹. In parallel, by surveying a separate cohort of 34 commercial fields an average of 30,789 ± 2658 volunteer ha⁻¹ was recorded in the subsequent cereal crop, with a repeat survey made after an additional year indicating an 87.2% reduction in this mean number of volunteers across the 34 fields (P < 0.001). Of the additional variables studied only location (P < 0.001), herbicide application (P = 0.037) and potato variety used (P = 0.045) significantly influenced volunteer proliferation. Volunteer fecundity was confirmed with upto 3 tubers produced per 1st generation volunteer, with tuber yield from the 2nd generation volunteers reduced significantly (P < 0.001). Assessments of the tuber lots from these 2nd generation volunteers confirmed their ability to sprout post-dormancy, therefore, indicating the potential for 3rd generation volunteers to emerge. Combined, the datasets confirm the potential for significant seed-mediated gene flow from commercial potato systems; indicating that the regulated 0.9% coexistence threshold would in all probability be compromised if GM potatoes were grown in rotations of 1:4 years or less, in the absence of a comprehensive tuber loss and/or volunteer management system.     

高校图书馆引入贫困大学生义工的实践与思考

对贫困大学生义工的管理是新时期高校图书馆的一项新的工作。本文结合实际从明确工作目标、采取科学管理进行了探讨，并就取得的双赢效果进行了分析。     

Validating mammal monitoring methods and assessing the performance of volunteers in wildlife conservation—“Sed quis custodiet ipsos custodies ?”

Many conservation organisations rely heavily on volunteers, and the government often relies on them to achieve tasks for which funding is insufficient—for example, the monitoring of trends in biodiversity on a national scale. Thus, it is critical to deploy non-professionals effectively. In this study we validated and calibrated the data collected by 155 volunteers, assisting with mammal monitoring at Wytham Woods, Oxfordshire, between April 2000 and December 2001. Tasks included small mammal trapping and handling, surveying and censusing for badgers, estimating deer population sizes from dropping counts, and transect surveys for mammal field signs. We analysed the effects of age, gender, previous experience, physical fitness and aptitude on volunteer performance using quantitative measures and qualitative scores. We found that (1) techniques that could be taught to volunteers without lengthy or specialist training were sufficiently accurate to yield reliable data, (2) with approximately half a day of training in each task, volunteers could produce reliable data, verified by professionals, and (3) volunteer teams brought considerable time savings to many tasks, compared with a single professional researcher. Our analyses show that physical fitness was a significant predictor of a volunteer's ability to perform tasks well and, in our particular sample, a male-bias in volunteer aptitude was apparent in some tasks. Previous experience as a conservation volunteer did not enhance performance over that of novices nor did age have any effect on volunteers’ ability. The overall veracity of volunteer data compared well with data collected using more specialist methods or collected by professional researchers using the same method. Volunteers required more time per task and, while they showed a tendency to underestimate population sizes, their results were consistent. Additionally, the programme helped to raise the environmental awareness of volunteers and their understanding of woodland ecology.     

Urban forestry priorities of Massachusetts (USA) tree wardens

As part of a survey we sent to tree wardens (individuals responsible for public trees) in communities in Massachusetts, USA, we examined which urban forest management tools and activities were most important to tree wardens themselves. Tree wardens generally agreed that inter-departmental communication and Chapter 87 (a state law promulgating the powers of a tree warden) were more important than having a qualified tree warden, an advocacy/advisory group, or a management plan (measures recognized by the USDA Forest Service in the Community Accomplishment Reporting System). Nearly all tree wardens prioritized removing dead and hazard trees. We discuss management implications of our results, paying particular attention to the importance of state laws in supporting urban forest management.