Application of acoustic Doppler current profiler combined with a scientific echo sounder for krill Euphausia pacifica density estimation

ABSTRACT:   An application of the acoustic Doppler current profiler (ADCP, 153.6 kHz) in combination with a scientific echo sounder (EK60, 38 and 200 kHz) was investigated to estimate the density of krill Euphausia pacifica . The acoustic backscattering strength from sound scattering layers was compared with biomass estimates from midwater trawls. Euphausia pacifica was targeted among mixed species populations in the sound scattering layer in the offshore Funka Bay area of Hokkaido, Japan. The frequency characteristics of acoustic backscattering by krill were calculated using a distorted wave Born approximation scattering model at three frequencies. Krill aggregations identified from the EK60 data were extracted as the mean volume backscattering strength difference between two frequencies. They were then used to identify similar aggregations in the ADCP data by matching observation times and depths for the two methods, which were applied simultaneously. Results from the comparison of the mean volume backscattering strength and the density calculated from the ADCP and EK60 showed that ADCP can be used to measure density and spatial–temporal distribution of krill aggregations. Current speed and direction at the study site were found to be 16.1 cm/s and 187.0°, respectively, and krill speed and direction (including the current component) were found to be 19.8 cm/s and 172.2°, respectively. Based on the ADCP data, the net speed and direction of the krill aggregations were found to be 5.9 cm/s and 128.0°, respectively.     

木荷容器苗技术应用和推广模式

介绍在浙南地区发展较快的木荷容器苗的技术应用和推广模式,分析木荷容器苗的特点、技术应用,分析木荷容器苗的生产规模、生产方式以及应用前景方面存在的问题并提出一些对策和建议.     

木荷播种育苗的关键技术

采用随机区组设计,对影响木荷播种苗产量和质量的4个主要因素--播种方法、施肥种类、覆土厚度和播种量进行了系统研究,观测了在4种技术条件下种子的发芽率、苗木的高、地径、主根长、侧根数、苗木总产量和合格苗产量,然后运用数理统计方法,从不同的角度分析了苗木质量和产量指标的变异情况.通过观测分析,总结出一套能保证木荷丰产优质的育苗技术.     

木荷种子贮藏方法试验初报

对木荷种子进行低温冷藏和常温贮藏试验。结果表明：低温冷藏7个月、常温贮藏8个月的种子发芽率分别为20．8％和3．8％，t检验结果为两种处理的木荷种子发芽率差异极显著。说明不同的贮藏方法对木荷种子的发芽有显著的影响。     

木荷地理种源苗期性状遗传变异研究

对采自6省(区)37个木荷种源种子进行了苗期试验,结果表明：木荷种源间苗高、地径、生物量有着极显著的差异,且有较高的广义遗传力。木荷苗高生长以8-9月份为速生期,这时期的生长占年生长的50％～56％,苗高和地径生长与纬度呈极显著负相关,说明通过木荷种源选择,能取得较好的效果,并初步筛选出广东开平、阳山、韶关,福建华安,江西上犹等苗期生长表现突出的种源。     

木荷优良家系的组织培养研究

以新选育的木荷（Schima superba）优良家系为试材,开展组织培养。结果表明,木荷适宜的初代培养基为GD+6-BA 1.50 mg·L-1+NAA 0.50 mg·L-1,继代培养基为GD+6-BA 1.00 mg·L-1+ IAA 0.30mg·L-1,生根培养基为1/4 MS+ IBA 1.00 mg·L-1+IAA 0.40 mg·L-1。芽苗增殖倍数为3.1倍,生根率达96.67％。探索出适宜的驯化、移栽和后期管理技术,使优良家系生根苗的移栽存活率达到92.2％。     

怀集县木荷防火林带的防护效能

怀苎县营建的木荷生物防火林带，经测试具有很好的抗火性、耐火性、难燃性等特点，可阻隔地表火和林冠火的蔓延，起到防火的作用，并可改善林地环境，防止水土流失，其经济效益、生态效益和社会效盖显著。文章还介绍了木荷防火林带的营建技术。     

木荷芽苗移栽育苗技术

根据木荷育苗实践，总结出了一套木荷芽苗移栽技术，单位面积产苗量可达54万株/hm^2，且苗木质量较好。     

马尾松-木荷混交造林效果的调查研究

我国南方立地条件差的低丘岗地,营造马尾松纯林易遭病虫危害,水土流失严重,林地肥力降低,难于成材,为此,对江西高安县9年生马尾松-木荷混交林及其纯林进行了综合调查研究,设立标准地,进行林分生长量、生物量、叶面积、根系、土壤、植被、病虫害、枯落物、水土流失、小气候等观测研究。结果表明,混交林的树高、胸径、每公顷立木蓄积量分别比纯松林大30 9%、31 7%、10 7%,生物量是纯松林的2 24倍,枯落物是纯松、荷林的3 37、1 96倍,病虫害的株发生率、水土流失、小气候等的改善均优于纯松林。松 荷混交林是我国亚热带地区,尤其是低丘岗地上值得推广的优良针阔混交类型。在生产上,建议进行株间、行间或小块状混交,或星散状混交,马尾松、木荷混交比例为5～3∶1,初植株行距为1 2m×1 2m、1 5m×1 5m或2m×2m,密度为4440～6944株·hm-2。     

木荷凋落物分解及对土壤作用规律的研究

在福建省永春碧卿林场开展的木荷凋落物分解及土壤淋溶试验表明 :木荷人工林凋落物量和养分积累量下坡 >中坡 >上坡 ,养分积累量Ca >N >K >Mg >Fe >P >Zn >Cu ;凋落物分解的失重率Ws与时间t之间存在Ws =34 45 2Lnt -3 0 741(R =0 98)的对数关系 ;木荷凋落物可通过增加土壤有机质 ,提高土壤和下渗液的盐基量 ,提高土壤pH值 ,降低土壤水解性总酸度等途径来缓解土壤的酸化作用