The U.S. Wholesale Market for Marine Ornamentals

The market for marine ornamentals encompasses all live marine species (fish and invertebrates) destined for the aquarium trade. In 1998, U.S. imports and exports were valued at approximately US $1.5 billion at the border (all dollar values cited in this paper are $US). In Florida, cultured freshwater and collected saltwater species accounted for $70 million and $4 million, respectively, in annual dockside revenue. To help explain Florida's marine landings and provide suggestions for future resource management and market campaigns that reflect the perceptions of the industry, a survey of wholesalers was initiated in 1999. Preliminary results indicate that there are several intermediate wholesale markets. Florida firms are closer to the supply as many also collect. Wholesalers in other states handle more freshwater product, are larger, and tend to import a larger share of their inventory. Consolidation is expected to continue, but niche markets for eco-friendly firms are expected to grow. In Florida, marketing strategies should focus on the observed higher survival rates and increasing supply of the popular invertebrate species. Many wholesalers are concerned about additional regulations that could reduce the number of collectors and thereby increase supply variability, a noted weakness of the Florida industry.     

Analysis of regional variation of height growth and slenderness in populations of six urban tree species using a quantile regression approach

Inventory data of six urban tree species from seven cities across Germany were used to model regional variation of height growth, allometric scaling, and slenderness over a wide range of size and age using a quantile regression approach. Variation within and between species and cities was large. Height did not reach an asymptote but declined at higher ages, presumably because of reduction cuts. Allometric scaling and slenderness varied with wind climate, modulus of elasticity, and coefficient of drag. Our data do not support the use of a threshold value of slenderness in tree risk assessment.     

Total and free thyroid hormones in plasma of tropical marine teleost fish

Plasma levels of L-thyroxine (T₄) and 3,5,3-triiodo-L-thyronine (T₃) and the percentage of plasma T₄ and T₃ present in the free (dialyzable) form (%FT₄ and %FT₃) were measured in 16 species (11 families) of tropical marine teleosts from an inshore Barbados reef. Mean plasma T₄ varied from 0.2 ng/ml to 42 ng/ml; mean plasma T₃ varied from < 0.2 ng/ml to 50 ng/ml. The highest T₄ and T₃ levels were recorded in parrot-fish and the lowest levels in filefish. The %oFT₄ and %FT₃ varied from 0.05–3.41%. Estimated levels of plasma free T₄ and free T₃ levels ranged from 0.4–466 pg/ml. The extremely wide inter- and intra-species ranges in levels of free T₄ and T₃ do not support a previous suggestion, based on temperate freshwater salmonid species, that free T₄ and T₃ levels in fish may fall within a relatively range narrow comparable to that of homeothermic vertebrates.     

热带水稻优异种质资源的表型遗传多样性分析

有效管理和充分挖掘遗传多样性丰富的稻种资源对水稻育种具有重要意义。利用15个表型性状对来自9个热带国家和地区的127份热带水稻育种优异种质进行综合评价,比较分析不同来源热带水稻优异种质的表型差异和遗传多样性指数。结果表明：热带水稻种质资源表型性状差异明显,数量性状的变异系数为7.0%～23.8%,平均为12.04%,其中单株穗数比较大,谷粒长较小;Shannon-Wiener多样性指数分析结果表明,15个表型性状遗传多样性指数变化为0.603～2.066,平均为1.579,其中每穗总粒数比较高,穗型较小;9个不同来源地的热带水稻资源多样性指数为0.780～1.547,平均为1.219。不同来源的热带水稻种质各性状变异范围较大,各性状间存在显著差异,遗传多样性指数较高,可进一步发掘优异资源和有利基因,为培育和筛选优良热带水稻品种提供亲本来源。     

国家重要热带作物工程技术研究中心运行机制探讨

从国家重要热带作物工程技术研究中心现状出发,探讨工程中心的运行机制,提出了加快构建热带农业工程技术研究中心运行机制的对策和建议。     

Spatial variability of surface peat properties and carbon emissions in a tropical peatland oil palm monoculture during a dry season

The expansion of oil palm monocultures into globally important Southeast Asian tropical peatlands has caused severe environmental damage. Despite much of the current focus of environmental impacts being directed at industrial scale plantations, over half of oil palm land-use cover in Southeast Asia is from smallholder plantations. We differentiated a first generation smallholder oil palm monoculture into 8 different sampling zones, and further divided the 8 sampling zones into oil palm root influenced (Proximal) and reduced root influence (Distal) areas, to assess how peat properties regulate in situ carbon dioxide (CO₂) and methane (CH₄) fluxes. We found that all the physico-chemical properties and nutrient concentrations except sulphur varied significantly among sampling zones. All physico-chemical properties except electrical conductivity, and all nutrient content except nitrogen and potassium varied significantly between Proximal and Distal areas. Mean CO₂ fluxes (ranged between 382 and 1191 mg m⁻² h⁻¹) varied significantly among sampling zones, and between Proximal and Distal areas, with notably high emissions in Dead Wood and Path zones, and consistently higher emissions in Proximal areas compared to Distal areas within almost all the zones. CH₄ fluxes (ranged between −32 and 243 µg m⁻² h⁻¹) did not significantly vary between Proximal and Distal areas, however significantly varied amongst sampling zones. CH₄ flux was notably high in Canal Edge and Understorey Ferns zones, and negative in Dead Wood zone. The results demonstrate the high heterogeneity of peat properties within oil palm monoculture, strengthening the need for intensive sampling to characterize a land use in the tropical peatlands.     

中国亚热带干旱多尺度时空格局及演变趋势

为探讨不同时间尺度下中国亚热带区域干旱的时空特征,利用1 km气象数据计算1959—2019年亚热带区域标准化降水蒸散发指数(SPEI),并且结合干旱线性变化趋势、影响范围、强度及频率,分析了不同时间尺度(1月、3月、6月、12月)下中国亚热带区域干旱的时空特征。结果表明:(1)干旱时期主要集中在2004—2014年,干旱化区域空间上呈现明显的东西对比,时间尺度上秋季的干旱化趋势最为显著;(2)各时间尺度的干旱影响范围都处于不断波动上升的趋势,尤其是在1995年之后,干旱影响范围上升趋势尤为明显;(3)季节和干湿季较大干旱强度零星分布在亚热带西南部及湖南、江西等省,年际较大干旱强度则主要集中在亚热带东南部;(4)秋季发生干旱的频率最高,年际发生中度及以上干旱频率最高,春季高频中度及以上干旱频率集中在四川、西藏等地,秋季和年际主要集中在四川、重庆和贵州的交界处,夏季、冬季以及干湿季则零星分布在亚热带各省份。综上,亚热带总体呈现干旱化趋势,季节、干湿季和年际尺度的干旱影响范围时间序列变化趋势较为相似,但干旱强度和干旱发生频率在空间上存在一定差异。     

基于DEM的热作区土地利用现状分析——以阳江农场为例

在GIS空间分析功能的支持下,利用数字高程模型(Digital Elevation Model,DEM)提取阳江农场高程、坡度和坡向数据,计算橡胶林、农用地及未利用地等3种土地利用类型的分级分布指数,准确描述农场主要用地类型的空间分布频率,总结分布趋势,为进一步制定热作区农场发展规划提供参考。     

南亚热带不同林龄人工针阔混交林物种多样性研究

为系统评价南亚热带不同林龄人工针阔混交林生物多样性的状况,在广东省佛山市云勇林场选择立地条件相近的针阔混交林,对乔木层、灌木层和草本层的生物多样性进行了比较。针阔混交林分为3个林龄段,其中针阔混交林Ⅰ为10-11a生,针阔混交林Ⅱ为7-9a生,针阔混交林Ⅲ为3-5a生。生物多样性用物种丰富度指数（S）、Shannon-Wiener指数（H′）、Simpson优势度指数（D）和Pielou 均匀度指数（E）衡量。结果表明：随着林龄的增大,针阔混交林乔木层和灌木层植物种数先减小再增大,草本层则先增大再减小。针阔混交林乔木层重要值最大的科均为杉科,其重要值随林龄的增大呈现出先升高后降低的趋势,表明杉木在演替过程中不断衰退,逐渐被阔叶树种所取代。不同林龄针阔混交林乔木层主要以樟科、金缕梅科、山茶科、大戟科、芸香科和木兰科占优。在乔木层,重要值较高的造林树种包括米老排、阴香、山杜英、藜蒴、香樟、火力楠、楝叶吴茱萸,这些树种适宜于本地区杉木林改造;重要值较高的自然更新乔木物种为鸭脚木、山苍子、山麻黄和银柴。在灌木层,重要值较高的物种因林分而异,藜蒴、鸭脚木、山苍子、山黄麻等乔木树种的幼苗具有较高的重要值,表明部分造林树种能够实现自我更新,群落处于正向演替过程中。草本层以蔓生莠竹、弓果黍、蕨、乌毛蕨和假臭草等为主。随林龄的增加,乔木层S呈上升的趋势,而H′、D和E表现为先降低后升高;灌木层S表现为先降低后升高,而H′、D和E呈现出下降的趋势;草本层所有指数则表现为先升高后下降。多样性指数的变化也反映出林分改造促进了群落的演替。