热带大西洋金枪鱼延绳钓兼捕鲨鱼种类组成和渔获率及其与表温的关系

根据2007年12月~2008年3月采集的热带大西洋(05°37′~12°01′N、29°00′~36°51′W)金枪鱼延绳钓渔获物数据,分析了金枪鱼延绳钓兼捕鲨鱼的种类组成、渔获量、渔获率及其与表温的关系。本次调查共捕获鲨鱼8种,隶属3目7科7属,总渔获尾数为633 ind,总渔获量达26 837.4 kg,其中大青鲨为主要兼捕种类。各种鲨鱼渔获率平均值在0.003~1.524 ind/1 000 hooks之间,其中大青鲨最高,其值为1.524 ind/1 000 hooks,大眼砂锥齿鲨最低,其值为0.003 ind/1 000 hooks。各种鲨鱼渔获率月变化不明显(ANOVA,P=0.901)。鲨鱼总渔获率和大青鲨渔获率与表温都呈显著性负相关。大青鲨主要出现渔场的表温范围为24.6~25.8℃。     

Effects of water flow velocity and fish culture on net biofouling in fish cages

The effects of water flow, fish feed and cage position on net biofouling was examined in a floating cage fish farm. Fouling of 16 mm mesh net panels suspended inside and outside net cages and exposed to different treatments were monitored weekly until net apertures were completely occluded by the fouling organisms (8 weeks). Results indicate a dramatic reduction in water flow velocity throughout the fish farm due to the cage units themselves and net biofouling. The reduced water flow (<10 cm s^?1) inside net cages promoted rapid net biofouling, while rapid water flow outside the net cages (>25 cm s^?1) kept the net fouling organisms at bay. Although fish rearing in net cages with inputs of commercial pellet feed increased sessile biofouling (222% higher than outside the net cages) and non‐sessile biofouling (570% higher), the type of fish feed used did not significantly affect biofouling development. The study recommends that the geometry of serially arranged net cages, as commonly deployed in tropical tidal estuaries, be reconfigured to improve flow through in order to minimize the impact of fouling.     

Better land husbandry in Honduras: towards the new paradigm in conserving soil,water and productivity

Land shortages are forcing more smallholder farmers to cultivate tropical steeplands. Resulting accelerated soil erosion is being countered by the promotion of soil conservation (SC) technologies, such as cross‐slope barriers, which aim to reduce soil loss and preserve land productivity. However, farmer adoption rates tend to be low. This is often attributed to the farmers' conservatism or lack of education. Research in Honduras's steeplands demonstrates that farmers value SC, provided that it promotes agricultural production. Field research from 1995–98, involving farmed test plots on slopes greater than 35 per cent (19 degrees), demonstrates that at least one typical SC technology—live barriers of Vetiveria zizanioides (vetiver grass)—has little or no impact on maize yield. This means that farmers see little benefit from their investment in the SC method. They find that erratic rainfall, pests and diseases and a lack of economic resources are far greater threats to their livelihoods than soil erosion. Consequently, SC has a low priority. Keeping soil in place avoids major off‐farm disbenefits. However, the SC technique tested here made no discernible difference to slope foot sediment yields during the life of this study. In sum, a new approach is needed. Promoting ‘Better Land Husbandry’ strategies, which seek to combine farmers' concerns about productivity with conservationists' concerns about reducing soil erosion—often via cover‐management—seem to be the best way forward. Copyright © 2002 John Wiley & Sons, Ltd.     

Effects of liana load,tree diameter and distances between conspecifics on seed production in tropical timber trees

Seed production in tropical timber trees is limited by abiotic resources, pollination and pre-dispersal seed predation. Resource availability is influenced by the number of competing trees and by lianas that often reach high densities in disturbed parts of tropical forests. The distance between conspecific trees affects pollination efficiency and seed predation intensity, and may therefore indirectly affect the long-term sustainability of selective logging. Here we investigate how reproductive status and the number of seeds dispersed per tree are affected by liana load, distance to the nearest conspecifics, number of competing neighbours and tree diameter in the timber trees Cariniana ianeirensis and Terminalia oblonga. The study is based on a large-scale silvicultural experiment in lowland Bolivia. We found that the reproductive status of the two species was negatively correlated with liana cover and positively with tree diameter. In C. ianeirensis the most liana-infested trees dispersed fewer seeds. In T. oblonga the intensity of pre-dispersal seed predation decreased with distance to the nearest conspecifics. There was no evidence that seed viability or seed production decreased with distance to nearest conspecifics in either species as would be expected if isolation resulted in increased self-pollination. Our results indicate that reproduction can be severely reduced in timber trees if the largest, most healthy and least liana-covered trees are logged, but that liana cutting on the remaining seed trees can considerably improve seed production. In some species seed production may be further improved by ensuring that seed trees are located far apart.     

热带亚热带地区8种旋花科植物的元素含量分析

摘要：对热带亚热带地区8种18个旋花科植物样的元素含量特征进行了分析,结果显示,平均含量＞1%的有N、K、Ca,0.2～0.5%的有S、Mg、P,0.01～0.05%的有Fe、Mn,＜0.01%的有Zn、B、Cu、Hg、Pb、As、Cr、Mo、Cd,其含量顺序为N＞K＞Ca＞S＞Mg＞P＞Fe＞Mn＞Zn＞B＞Cu＞Hg＞Pb＞As＞Cr＞Mo＞Cd;参考全国有机肥料品质四要素分级标准和全国有机肥料品质总分分级标准对参试样品的肥用价值进行评价,18个参试样品富含N、K,而P的含量居中下等水平,其中云南多花山猪菜达到一级标准;6个常量元素的变异系数在0.30～0.60之间,微量元素中除B、Cu的变异系数较低外（分别为0.40和0.48）,其余均在0.70以上,其中Pb、Mo、Cd的变异系数超过了1.00（分别为1.13、1.32、1.54）;N与P,Ca与S,Cr与Mo、Cd,Pb与Mo、Fe间呈显著的正相关,K与B,Pb与Cr、Mo间呈极显著的正相关, 而As与Cu,N与Mn,P与Cd、Mn间呈显著的负相关;72%的植物中B的含量极低,云南多花山猪菜和云南山猪菜中Cu的含量极低,广西百色市掌叶山猪菜的Mo含量极低（未检测出）,50%的植物中Mn的含量超标;用测试植物的元素含量与一般植物元素含量范围上限比值分析植物污染量时, 云南山猪菜、海南厚藤及虎脚牵牛的As含量,4个植物样的Cd含量,约61%的Cr含量,空心菜的Zn含量,云南掌叶山猪菜和广西五爪金龙的Pb含量比值大于1。     

火龙果果实氨基酸含量及组成分析

以火龙果和9种常见热带、亚热带水果为材料,对比分析了氨基酸含量及组成.结果表明:火龙果含有17种氨基酸,种类较齐全.其氨基酸总量排名第4位、人体必需氨基酸含量和儿童必需氨基酸含量分别排名第2位和第4位.火龙果的E/T值为35.07%,E/N值为0.54,基本符合理想蛋白质的要求.火龙果中各种人体,必需氨基酸,异亮氨酸、亮氨酸、蛋氨酸+胱氨酸、苯丙氨酸+酪氨酸、苏氨酸、缬氨酸的含量占氨基酸总量的比例,与1973年FAO/WHO修订的人体必需氨基酸含量模式谱基本一致,仅赖氨酸中度缺乏.火龙果中鲜味类、芳香族、甜味类氨基酸含量分别居第6、2、2位.     

灰色关联分析在热带气旋灾害等级评估中的应用

利用1970～2007年影响海南省的86个热带气旋的灾情资料,从灾害对人的影响、灾害范围和灾害造成的经济损失量3个角度分析,选取受灾人口、死亡人口、农作物受灾面积、倒塌房屋、直接经济损失等5种灾害数据作为灾害等级评估的基础数据,利用灰色关联分析方法对热带气旋灾害等级进行评估,得到较为合理的结果,表明灰色关联分析方法可作为热带气旋灾害等级评估的实用方法.     

湖南省兰花产业发展现状及对策

分析当前国内外兰花发展趋势,结合湖南省兰花产业发展实际,探讨湖南省发展兰花产业的对策。     

我国热作地区绿色食品生产与质量安全控制探讨

通过对我国主要热作地区的农产品生产现状和绿色食品标志使用现状的调查研究,分析影响热带农产品质量安全生产的主要因素,提出热区绿色食品质量安全控制的建议,为热作地区绿色食品的发展和产品质量安全的控制提供参考。     

热带草莓生产状况及展望

简述我国热带草莓生产状况和目前生产中存在的问题,并对发展前景进行了探讨。