玉米灰斑病空间流行动态模拟模型组建及传播距离研究

 以玉米品种郑单958为试材接种灰斑病菌,在田间形成不同发病梯度,分析病害传播的空间流行动态,利用SAS9.13统计软件分别构建病害传播梯度的一维、二维和三维模型。结果表明:1.指数模型和GOMPERTZ模型是沈阳地区玉米灰斑病单向传播梯度的最佳模拟模型;2.高斯模型是模拟病害平行于垄向和垂直于垄向方向传播的最佳模型;3.含有(x²+y²)形式的圆形模型和含有a (x²+y²)+bx+cy+d形式的椭圆形模型是模拟病害在二维平面上传播过程的最佳模型。通过模型推导得到病害的传播距离约20~50m。     

基于GIS模型的林火蔓延计算机仿真

在GIS的支持下,建立了林火蔓延的空间背景数据库,在此基础上采用了王正非林火蔓延模型和遍历各点算法,在空间背景数据库之上,用Visual C 6.0 MapObject2.1控件技术进行了林火蔓延的动态模拟,以实现任意地点、任意气象条件下的林火蔓延动态仿真模拟,直观地掌握林火的发生、发展和蔓延的过程,以及林火蔓延的方向等。通过对模拟结果的分析得出,在模拟的过程中计算机运行比较快,模拟效果很好。     

Root biomass and distribution of five agroforestry tree species

Knowledge of the quantitative assessment and structural development of root systems is essential to improve and optimize productivity of agroforestry systems. Studies on root biomass recovery by sieves of different mesh sizes (2.0, 1.0, 0.5 and 0.25 mm) and root distribution for four-year-old individuals of five agroforestry tree species viz.; Acacia auriculiformis A. Cunn. ex Benth, Azadirachta indica A. Juss, Bauhinia variegata L., Bombax ceiba L. and Wendlandia exserta Roxb. were conducted at the research farm of Rajendra Agricultural University, Pusa, Bihar, India. The results indicated that the 0.5 mm sieve was adequate for recovery of the majority of roots. All the tree species exhibited a large variation in root depth and horizontal root spread four years after planting. The maximum root depth was recorded in W. exserta (2.10 m) and minimum in B. variegata (1.00 m). Horizontal root spread was 2.05 m in B. ceiba and 8.05 m in A. auriculiformis. Root spread exceeded crown cover for all species. The primary roots were more horizontal than the secondary roots. The length and diameter of the main root were highest in A. indica (108.3 cm) and B. ceiba (23.2 cm), respectively. Highest length and diameter of lateral roots were recorded in B. variegata (201.6 cm) and A. indica (1.8 cm), respectively. Total root biomass among different species accounted for 18.2–37.9% of the total tree biomass. Results of this study infer that although all the species have potential to conserve moisture and improve fertility status of the soil, A. auriculiformis is the most effective for promoting soil fertility. The deep rooted W. exserta and A. auriculiformis will be preferred for cultivation under agroforestry systems and could reduce competition for nutrients and moisture with crops by pumping from deeper layers of soil.     

锈色粒肩天牛扩散规律研究

通过对3块标地资料的分析,得出锈色粒肩天牛的扩散规律遵从指数曲线y=aebx(b<0),只是在不同虫口密度下,参数a、b取不同的值,进一步确定带虫苗木调运是锈色粒肩天牛蔓延扩散的主要传播途径,加强检疫是防止锈色粒肩天牛蔓延扩散的有效手段。     

饲用抗生素细菌耐药性的研究进展

饲用抗生素的不当使用,尤其是抗生素促长剂的滥用,导致动物体内细菌耐药性的产生并不断增强。耐药性细菌及其耐药基因会在动物、环境、人体之间水平传播,从而对人类健康造成了严重威胁。为此一些发达国家纷纷采取措施限制饲用抗生素的使用。研究表明,抗生素促长剂停用后,畜禽体内及动物性食品中耐药菌显著减少,相应地人体内耐药菌携带率亦随之显著下降。     

DEM在林火行为模拟中的应用

林火行为具有时间和空间特征,利用DEM(Digital Elevation Model)对林火行为进行3维模拟是一个很有前景的研究方向。本研究利用ArcView实现DEM数据源的提取、模型转换,通过林相图和地形图的配准,将影响林火蔓延的可燃物因子与DEM结合,进行效果图显示,为林火行为的3维模拟进行了有益的实践。     

设施栽培草莓不同施肥方法增铵效果

利用设施栽培草莓,对几种可能的增铵施肥方法进行了研究,结果表明,铵态氮肥撒施可以增加土壤中铵态氮浓度,达26 mg.kg-1,比不施肥处理高160%;提高铵态氮与硝态氮之比,达0.16,比不施肥处理高23%,但铵态氮及硝态氮浓度与2者之比下降很快,铵态氮和硝态氮浓度施肥后2个月分别降至16 mg.kg-1和76 mg.kg-1。腐殖酸钠与铵态化肥混施降低了铵态氮与硝态氮之比,具有较强的保肥能力。袋控缓释肥有效提高了土壤中铵态氮浓度、降低了硝态氮浓度,提高铵态氮与硝态氮之比,且能够长时间保持,铵态氮与硝态氮浓度分别维持在18 mg.kg-1与80mg.kg-1。袋控缓释肥和铵态氮肥添加腐殖酸钠撒施处理都能提高设施草莓产量,以袋控缓释处理产量最高,每666.7 m2产量达1577 kg,但是前期产量以铵态氮肥添加腐殖酸钠撒施处理最高,每666.7 m2产量达620 kg。     

Harmonic radar: efficacy at detecting and recovering insects on agricultural host plants

BACKGROUND: In pest management research, harmonic radar systems have been largely used to study insect movement across open or vegetation‐poor areas because the microwave signal is attenuated by the high water content of vegetation. This study evaluated whether the efficacy of this technology is sufficient to track insects in vegetative landscapes. RESULTS: Field efficacy data were collected using portable harmonic microwave radar and electronic dipole tags mounted on adults of three economically important pests: Leptinotarsa decemlineata (Say), Diabrotica virginifera virginifera (LeComte) and Conotrachelus nenuphar Herbst. Detection and recovery of tagged Colorado potato beetles, plum curculios and western corn rootworms was high within and among potato plants, moderate within apple trees and high within, but not between, corn plants respectively. The efficacy of the radar depends on the ability of the operator to move around the host, scanning for a signal ‘sightline’ with the tagged insect among plant structures. CONCLUSION: The detection rate of tagged insects by harmonic radar systems is high enough to track the walking path of pests through low row crops such as potato, tall row crops such as corn or tall but well‐separated trees of orchard‐type crops by adapting the scanning procedure to the vegetative architecture. Copyright © 2010 Crown in the right of Canada. Published by JohnWiley & Sons, Ltd     

中国马铃薯引进与传播之辨析

马铃薯在南美已有上万年的栽培驯化历史,然其在大陆间的传播仅发生在近代数百年间,海路是唯一可能的途径,但马铃薯引入中国的时间和途径却无定论。本文根据航海史料及最早发现大陆间特异物种的时间推测,马铃薯引进中国的时间可能为明永乐二十一年(1423年)郑和的第6次航海返回之时。根据典籍方志所载分析,马铃薯最初200年主要种植于北京,逐步成为皇宫珍肴。清朝时期于相互毗邻的乌蒙山区、武陵山区和秦巴山区广为栽培,是我国马铃薯最早的集中产区。     

Recruitment potential from asexual and sexual reproduction in Polymeria longifolia

Sexual and asexual reproduction in the perennial Australian weed Polymeria longifolia (polymeria take-all), was assessed using glasshouse and field studies. These studies aimed at elucidating the contribution that each reproductive mechanism makes to the success of the species as a weed in cotton in Australia. Asexual reproduction, including vegetative fragment movement because of cultivation and regeneration from in situ rhizome material, was the predominant means of dispersal and recruitment of the species. Sexual reproduction had a relatively minor but significant role in the reproductive biology of P. longifolia. Seedling establishment was <5% from buried seed in both the glasshouse and field. In the field, seedlings comprised <1% of the total number of new shoots recruited at the start of two consecutive seasons, with <3% of these reaching reproductive maturity. Vegetative fragments were more likely to survive and lead to subsequent shoot production when they were large and intact. Intensive cultivation, where plants of P. longifolia are cut into small fragments, may reduce the survival of fragments moved by cultivation and reduce recruitment from existing populations. Long-term management strategies should focus on reducing the large vegetative flushes of this weed, as well as controlling the small number of seedlings recruited.