Adequate design of control treatments in long term agroforeestry experiments with multiple objectives

Agroforestry experiments usually include control plots of either pure crop or pure tree stands. A clear distinction should be made between intensively managed biophysical controls and farming system controls with realistic labour input and management regimes. Trying to draw biophysical conclusions from farming system controls (or the reverse) is often not justifiable. The design and management of these elusive control plots is a complicated issue which is often overlooked. Many factors beyond the control of the experiment manager can disturb long term field agroforestry experiments. Some examples from French agroforestry experiments illustrate how uncontrolled factors may bias the results, including the proportion of harvested to planted trees, the weeding regimes, and the use of tree- shelters. The analysis of agroforestry data could be more efficient when considering a continuum of tree – crop mixture management options between the agroforestry plot and the non agroforestry plot. The concept of biophysical control plots becomes then less essential. A relevant modelling approach of interactions between trees and crops should 1) perform correctly for any tree/crop proportion and even for pure stands, when setting the parameters of the other component to zero, 2) provide for the inclusion of new, uncontrolled factors that could emerge through time. The biological efficiency of agroforestry systems may however be a subordinate criterion for agroforestry adoption, as observed at the moment in France. Agroforestry systems with poor biological outcomes can even be very attractive in some ecological or sociological conditions, and only farming system controls may bring this aspect to light. This revised version was published online in June 2006 with corrections to the Cover Date.     

单克隆抗体捕获ELISA检测鸡多杀性巴氏杆菌IgM抗体

应用抗鸡ＩｇＭ单克隆抗体建立了检测鸡抗多杀性巴氏杆菌（Ｐ．ｍ．）血清中特异性ＩｇＭ抗体的单克隆抗体捕获ＥＬＩＳＡ,其敏感性、特异性、重复性优于间接ＥＬＩＳＡ。用于检测鸡抗Ｐ．ｍ．的特异性ＩｇＭ抗体发现：鸡在注射免疫Ｐ．ｍ．灭活苗后第４天即可检测到ＩｇＭ抗体,并且上升较快,峰值在第２周为１：５１２０;鸡在口服免疫Ｐ．ｍ．弱毒活苗后ＩｇＭ抗体上升缓慢,峰值在第４周左右,滴度较低为１：３２０;鸡在由不同途径感染不同的Ｐ．ｍ．强毒后第８天时,ＩｇＭ抗体滴度都明显上升。同时应用间接ＥＬＩＳＡ检测ＩｇＧ抗体滴度进行比较。本项研究对建立检测鸡抗其它病原微生物特异性ＩｇＭ抗体方法具有借鉴意义。     

浙江省单拖渔业现状分析与研究

利用2001~2006年浙江省单拖渔业典型性调查数据和2005~2008年的单拖作业监测资料,从浙江省单拖捕捞力量和产量分布、渔获对象和资源密度变化及经济效益、劳动力组成等几个方面进行了初步分析。结果表明,近几年浙江省单拖作业船数保持在2200艘左右,产量在40×104t左右,单船净利润存在年间波动,以2005年最高;单拖作业渔场分布较广,渔获物以头足类和中下层鱼类为主;近年来经济鱼类比例下降,而其它低值鱼类比例上升。文章最后提出了当前浙江单拖渔业存在的问题,并提出了相应管理建议以供参考。     

水产养殖水下机器人研究进展

水产养殖是世界范围内食品领域发展最快的行业之一,为人类提供了超过一半的水产品。但是,水产养殖目前面临机械化、自动化程度较低以及产量及效率不高等问题,因此迫切需要转型升级。水下机器人是一种机动灵活的水下作业装备,与传统的水下作业手段相比,在作业方式、范围、适应能力等方面具有明显的优势,应用于水产养殖监测及作业后,有望改变现有养殖模式,推进水产养殖业向机械化、工程化、智慧化、智能化转型,缓解水产养殖业的发展危机。尽管水下机器人近年来得到了蓬勃发展,但是目前在水产养殖业的推广应用仍非常有限,而且尚有诸多技术瓶颈未得到解决。本文面向水产养殖水下机器人的应用实际,对水质监测、视频监控及传输、目标识别与定位、高精度水下导航、智能规划与控制、机器人-机械手系统精准作业等关键技术进行了详细分析,并展望了未来的发展方向,以期为水产养殖水下机器人的研究和应用提供综合性参考。     

珠江河口及其附近水域银鲳生长与死亡参数估计

对珠江河口及其附近水域银鲳的生长与死亡参数进行估算,得von Bertalanffy生长方程的相关参数为：L∞=36．0cm,K=0．230,t0=-1．137;根据生长方程进一步计算得到自然死亡系数为0．586;20世纪9H0年代捕捞死亡系数为0．944,是20世纪80年代的近2倍;根据等渔获量曲线图分析,若在当前的捕捞规格(开捕叉长为12．0cm)下仍维持现行的捕捞强度(捕捞死亡系数),资源将受到破坏,而且不符合经济效益的要求。依据性成熟特征,开捕叉长最小应为15．0cm;综合考虑性成熟特征、当前可能的捕捞强度及经济效益,在提高产量而不破坏资源的前提下,建议珠江河口及附近水域银鲳的开捕叉长应由12．0cm增加至15．0cm。     

近20年来陕西省农作物碳截获的时空特征

[目的]研究近20a陕西省农作物碳截获的时空特征及其影响因素,为区域生态系统碳循环研究提供参考依据。[方法]基于陕西省主要作物的产量、播种面积等数据,运用系数法、灰色关联模型等进行估算与分析。[结果](1)1991—2012年陕西省主要作物的碳截获量呈波动式增加,其中粮食作物的碳截获量大于经济作物,且粮食作物的年际波动比经济作物稳定。(2)研究区主要作物碳截获量及其变化存在明显的空间差异,4个地理区作物碳截获量的大小依次为:关中地区陕南地区陕北黄土高原区陕北风沙区,且除陕南地区外,其他3大区域的作物碳截获量都呈增加趋势。主要作物碳截获的重心位于西安和咸阳地区,呈由西南向东北方向移动的变化趋势。(3)在各因素中,作物的有效灌溉面积、旱涝保收面积和播种面积对其碳截获量的影响较大,且各因素与作物碳截获量的关联度存在明显的空间差异。[结论]陕西省作物生长过程中起到明显的碳汇作用,但其碳截获的增速小于中国大部分地区,提高有效灌溉率和人为投入,有利于增加作物的碳截获量,对缓解区域碳减排的压力具有现实意义。     

Behavioral interactions between black mudfish (Neochanna diversus Stokell, 1949: Galaxiidae) and mosquitofish (Gambusia affinis Baird & Girard, 1854)a

The behavior of black mudfish (Neochanna diversus Stokell, 1949: Galaxiidae) and mosquitofish (Gambusia affinis Baird & Girard, 1854: Poeciliidae) was investigated in laboratory tanks. Black mudfish are indigenous to northern New Zealand, and mosquitofish are introduced; both species are sympatric in wetlands in the Waikato region. By comparing position, feeding rates and aggressive behavior of both species, we found that black mudfish were increasingly able to compete with mosquitofish as they grew from fry to adults. Mosquitofish were more aggressive towards mudfish fry and juveniles than were these two life stages towards mosquitofish, but adult mudfish were aggressive towards mosquitofish. Both small (18–24 mm total length (TL)) and large mosquitofish (25–36 mm TL) showed high aggression towards mudfish fry (13–18 mm TL), and fry were eaten by large mosquitofish. However, 3 interspecific differences appear to allow coexistence of these two species. Firstly, mudfish reproduce in winter, whereas mosquitofish reproduce in summer, resulting in mudfish fry being present when mosquitofish are at their lowest abundance. Secondly, mudfish can survive in seasonally dry habitats by aestivation, while mosquitofish cannot. Thirdly, adult black mudfish are nocturnal, whereas mosquitofish are primarily diurnal.     

A simple model for predicting ecological impacts of introduced aquatic organisms: a case study of common carp, Cyprinus carpio L., in the Sepik-Ramu River Basin, Papua New Guinea

Abstract Practical models for predicting the impacts of introduced biota are urgently required to assess the benefits and risks of introductions. The simple method described predicts the ecological consequences of an introduction through potential competition between species based on elementary niche classifications. The model's predictions are tested against field data for common carp, Cyprinus carpio L., which escaped from fish farms during a study of the feasibility of fish stock enhancement in a large river basin. Recorded effects of carp are based on pre- and post-carp gillnet catches, observations of local villagers, socio-economic censuses and other sources of data. The predicted ecological interactions of common carp are in broad agreement with those recorded. The method can assist pre-introduction assessments and is particularly useful where limited data exist. In this particular study, common carp have contributed significantly to an improved capture fishery by fortuitous accident; production from aquaculture was negligible. High niche overlap between carp and certain resident fish species is predicted and this may be of more consequence in highland than lowland regions. Organisms introduced/transferred for aquaculture should be assessed within a much wider forum. The intended impacts of an introduction/ transfer, which in the case study were entirely erroneous, is an area in need of considerable attention.