Artificial dispersal of endangered epiphytic lichens: a tool for conservation in boreal forest landscapes

Due to increasing fragmentation of the boreal forests of Fennoscandia, a number of epiphytic lichens are now becoming threatened. Since these species typically are limited by a poor ability of dispersal, one possible but largely unexplored strategy for conservation is to disperse lichen material artificially into suitable habitats. Therefore, the objective of this study was to evaluate survival and vitality in lichen fragments from Evernia divaricata (L.) Ach. and Ramalina dilacerata (Hoffm.) Hoffm. after transplantation into three different stand types situated in northern Sweden, using different fragment sizes and modes of transplantation. After one year, survival ranged between 85% and 97.5%, and new growth occurred at all transplantation sites. The study has shown that transplantations of small fragments might constitute a resource-efficient option for establishment of new populations of endangered lichen species, or for enlarging their populations at the present sites of occurrence. In addition, the mode of transplantation was of importance for fragment vitality.     

持续农业概念、特性、研究对象与解决的问题

论述了持续农业的概念及其特性，明确了持续农业的研究对象是农业新技术和在环境上安全与健康的农业生产开发管理战略的研究与开发，提出了我国持续农业研究应着重解决的几个问题。     

Wild-captive metapopulation viability analysis

We developed an interactive management model for wild and captive populations of the ploughshare tortoise or angonoka, Geochelone yniphora. Interactive management is based on the translocation of individuals between wild and captive populations to simulate a metapopulation. Demographic parameters of one captive and two wild populations of this rare tortoise were used to conduct a metapopulation viability analysis (MVA). The effectiveness of the conservation strategy proposed for this species was then evaluated by modifying the probability of extinction and growth of the metapopulation over a fixed period of time. Several alternative scenarios of interactive management were then tested and ranked in terms of their effect on the viability of the metapopulation. The model predicted that catastrophic events such as bush fires would likely have a negative effect on the future of remaining wild populations. However, the model also predicted that the use of captive-born offspring to establish additional wild populations would decrease the risk of extinction of the metapopulation as a whole. We believe that, when supported by sound knowledge of the demographic parameters of a species, the use of MVA as part of an interactive management program can be an effective conservation tool that allows assessment of the probable response of both captive and wild populations to different management alternatives. One of the most interesting aspects of this interactive management approach is the link between in situ and ex situ conservation.     

Long-term avian research at the San Joaquin Experimental Range: Recommendations for monitoring and managing oak woodlands

Experimental forests and ranges are living laboratories that provide opportunities for conducting scientific research and transferring research results to partners and stakeholders. They are invaluable for their long-term data and capacity to foster collaborative, interdisciplinary research. The San Joaquin Experimental Range (SJER) was established to develop appropriate land management practices on foothill rangelands in California. SJER has a long and rich history of avian research. Natural history observations recorded since 1935 demonstrate that oak woodlands are one of the most diverse habitat types in North America. Early avian studies focused on California quail (Callipepla californica) as a game species and led to insights on quail diet and habitat requirements. Starting in the late 1970s, the focus of avian research shifted to methods for detecting changes in wildlife populations over time and response to management practices. This research has led to important recommendations for implementing bird monitoring programs. Using data collected on bird numbers, in conjunction with monitoring reproductive success of all species, recent studies have examined life history strategies, source-sink dynamics, the effects of livestock grazing, and the impacts of an invasive species on native cavity-nesting species. We are currently in the process of examining population trends and predicting the effects of climate change using long-term data. SJER continues to provide unique opportunities for research and educational activities that increase our understanding of the foothill oak woodlands of California.     

全电路制动系统BBW的结构及其发展浅谈

随着汽车技术的进步和汽车行驶安全要求的提高，国外汽车界开始研究一种全新的汽车制动系统——全电路制动系统（the Brake—By—Wire system，简称BBW系统）。BBW系统采用电能来代替传统制动系统中的液压或者气压能．可以显著地提高汽车的制动安全性。介绍了BBW系统的一般结构，阐述了BBW系统的工作过程，并根据工作过程分析了BBW系统的制动效果，最后结合当前BBW系统的几个技术难点，分析了BBW系统的发展前景。     

Analysis of groundwater behaviour in a farmer controlled subsurface tile drainage system in Mardan, Pakistan

Extensive subsurface drainage system was installed in districtMardan in the North West Frontier Provinceof Pakistan in 1987 to control increasingwater logging and salinity problems due tocanal irrigation. Several recentlycompleted fields studies have indicatedthat subsurface drainage system hasenormously lowered watertable in certainareas due to extensive drainage network. Therefore, a study of controlled subsurfacedrainage technique was initiated in MardanScarp area to observe the temporal andspatial variations in water table depths ofthis specific case under various modes ofcanal irrigation and monsoon rains. Twoartificially drained areas, consisting of40 ha and 160 ha respectively, werecontrolled and selected for extensivemonitoring. A total of 98 observationswells (7.6 cm dia. and 4.1 m depth) wereinstalled in between lateral drains toobserve water table fluctuation. Theresults of this study are very interesting.Each of the two areas monitored in thestudy behaved differently. It was observedthat in one of the areas design water tabledepth at 1.1 m was maintained with properfunctioning of the controlled techniqueapplied to the subsurface drainage system. The results from this area showed that 25to 55% of the time throughout the yearachieved this objective whereas in thesecond area desired water table could notbe maintained and water table depth in thisarea remained between 2.0 to 2.7 m causingunnecessary water stress to plants. Alsoit was observed that watertable in theformer area is mostly controlled by thefunctional behavior of the irrigationcanal. In addition, the proper functioningof controlled techniques in subsurfacedrainage system supplemented veryefficiently to retain the groundwater levelto the optimal limits in dry season and tothe design ones in the others for timelyneeds of the crops. Also rainfalls havesignificant impact on the spatial andtemporal behaviors of water table depths inboth the areas during the monsoon season.     

浊水溪下游段河性分析与治理对策

台湾地区随着国民生活水准提升，都市土地充分利用后，有关河川之治水、利水、亲水、保水、活水等功能渐受沿岸居民重视。目前浊水溪下游段深水槽经调查发现已严重下陷约6m，当历经桃芝台风时其洪峰流量29000cms远超过100年洪水频率之洪峰流量24000cms，亦超过洪水频率200年之洪峰流量27000cms，但是下游段河防构造物却未受到任何损坏，反而集集拦河堰上游之陈有兰溪及南清水沟溪受到土石流严重的侵袭，造成人民生命财产重大的损失。探究原由乃是通洪断面增加，深水槽流路稳定，洪水未冲击堤防所致，故将检视浊水溪下游河段治理计划之合理性，探讨可否将以往浊水溪治理计划之两段式复式断面，因势利导致为三段式复式断面布置，更能符合河川治理之经济性、稳定性、可行性等需求。     

北方粳稻米业发展策略研究

简要介绍了北方粳稻市场的需求情况、市场竞争的制约因素及米业发展策略,阐述了乌苏里江米业集团通过借地扎根、借库储粮、借船出海、借会扬名、借梯登高、借店生财等手段,达到确保粮源、降低成本、扩大市场、树立品牌形象,建立市场销售网络的成功经验。     

Effects of three management strategies on the seedbank, emergence and the need for hand weeding in an organic arable cropping system

The effects of three different weed management strategies on the required input of hand weeding in an arable organic farming system, the weed seedbank in the soil and the emerging weed seedling emergence were studied from 1996 to 2003. Strategies were based on population dynamic models and aimed for (1) control of weeds as carried out in standard organic farming practice, (2) control of all residual weeds that grow above the crop and (3) prevention of all weed seed return to the soil. Under all strategies, the size of the seedbank increased during the conversion from conventional to organic farming systems. The increase under strategy 3 was significantly smaller than the increase under the other strategies. From 1999 onwards, the weed densities in plots treated with strategy 3 became significantly lower than the weed densities in plots treated with the other strategies. The time needed for hand‐weeding required to prevent weed seed return, in addition to the time needed in standard organic farming practices, reduced during the course of the study. A management strategy aimed at the prevention of seed return (strategy 3) can reduce the size of the increase of the seedbank, which is usually observed after transition from conventional to organic farming. This study provides unique real‐world data that are essential for evaluating population dynamic models. The results may contribute to the development of weed management systems based on ‘no seed’ threshold strategies and to a further decrease in the dependence on herbicides.     

美国学校中政治教育的演变阶段探析

本文试析了美国学校中政治教育的演变阶段先后为:建国后、南北战争后、1900年以后和21世纪60年代后，认为随着21世纪的到来，美国学校中的政治教育又进入了一个新的发展盯段，并且尝试探析了这种划分对我国政治教育的启示。