Early Coppice Sites in the New Forest, Hampshire

Recently discovered historical evidence of the development ofcoppice woods in the New Forest indicates that this system ofmanagement declined during the 15th and 16th centuries. Thistrend coincided with economic changes and an increased demandfor naval timber. It is suggested that the unenclosed woodsin the Forest are of a natural origin.     

我国育林技术新发展概述

本文扼要地对林木种子繁育，苗林培育，更新和森林经营等方面的科研成果进行了分析，反映出这些领域的科研现状和动向，说明研究的广度和深度已经达到了相当高的水平，具有从生产实际需要出发，基础理论与应用技术相结合的鲜明特点，同时指出了研究中的某些薄弱环节。     

Natural abundance N in soil and litter across a nitrate-output gradient in New Hampshire

Stable isotopes of nitrogen are potentially a valuable tool for regional assessments of nitrogen saturation because they provide an integrated measure of the past nitrogen cycling history of a site. We measured δ¹⁵N of soil and litter, as well as net nitrification potential, at three sites across a nitrate-loss gradient in the White Mountains, New Hampshire to test the hypotheses: (1) that δ¹⁵N in soil and litter increase across a spatial gradient of nitrate loss; and (2) that δ¹⁵N in soil and litter is elevated when nitrification is elevated. δ¹⁵N was found not to vary significantly among the three sites. Patterns of leaf litter and forest floor δ¹⁵N, however, were strongly influenced by species composition in individual plots. Beech litter had significantly higher δ¹⁵N than yellow birch, sugar maple, and red maple. The conifer-dominated plots had significantly lower δ¹⁵N in both the organic soil horizons and in litter than did the hardwood-dominated plots. When we adjusted for spatial heterogeneity in mineral soil δ¹⁵N values by using an enrichment factor, δ¹⁵N_foliar − δ¹⁵N_Bs, in place of absolute soil δ¹⁵N values, a positive relationship was found with net nitrification for hardwoods. δ¹⁵N may also be a useful tool for evaluating species differences in nitrogen cycling and nitrogen uptake. The distinct pattern we observed of decreasing δ¹⁵N across the continuum from hardwood-dominated to conifer-dominated sites may suggest that local drivers (for example, nitrification rate) regulate the absolute value of foliar δ¹⁵N, while species-driven factors (e.g., timing and type of uptake) control the foliar δ¹⁵N value of one species relative to another in the same plot.     

Long-term species and structural changes after cleaning young even-aged northern hardwoods in New Hampshire,USA

The effects of four cleaning practices (including a control) on species composition and structural characteristics were studied over a 31-year period following treatment of an even-aged 25-year-old northern-hardwood stand that originated after complete clearcutting in 1933–1935. The treatments consisted of: a heavy and a light crop tree cleaning; a drastic species-cleaning treatment that removed nearly all pin cherry (Prunus pensylvanica L.f.), aspen (Populus tremuloides Michx. and grandidentata Michx.), striped maple (Acer pensylvanicum L.), and red maple (Acer rubrum L.) sprout clumps followed by a crop-tree cleaning; and an uncut control. There were no significant differences among treatments in species and structural characteristics in the 56-year-old stand at the end of the study period, except for the presence of a moderate aspen component in the light cleaning and the control. Although previous research shows that cleaning treatments in young northern hardwoods may have silvicultural and economic benefits, the impact of such treatments on long-term stand development is relatively minor.     

棕黑疣螈种组分子系统发育分析及大围山疣螈新种描述

采用贝叶斯法对棕黑疣螈种组13个个体的线粒体DNA ND2基因重建了系统发育关系,结果表明,（1）该种组物种形成1个单系群;（2）红瘰疣螈不是棕黑疣螈的同物异名,支持红瘰疣螈物种地位的有效性;（3）采自云南省红河州屏边县大围山的2个标本与红瘰疣螈亲缘关系较近,并构成姐妹群,其种间遗传距离已达到种级水平。其地理居群物种为一未描述新种,定名为大围山疣螈。新种的主要鉴别特征为,前肢长于后肢或后肢略长;头部和前后臂为棕黑色,颞部和指、趾端为棕黄色。     

中国长珠蚧属一新种记述(同翅目:蚧总科:珠蚧科)

报道发现于北京国槐上的蚧虫一新种--槐树长珠蚧(Neogreenia sophorica Wu,sp.nov.),详细记述并描绘该种各虫龄的形态特征,编制长珠蚧属(Neogreenia MacGillivray)世界种类的分种检索表.     

美国大平原防护林概况

本文对美国大平原防护林的发展、研究进行了系统介绍,主要包括:大平原防护林发展简史、规划设计、营造技术、效益评价、经营管理等内容。为我国防护林建设提供一些经验、教训。     

药用野生植物资源开发利用简述

文章通过阐述我国药用植物资源的概况,总结开发利用现状,并提出目前存在的问题和今后的发展方向。以期为充分合理地开发利用药用植物资源,实现经济、生态和社会效益和谐统一的目标提供参考。     

国外松简介及江西省各生态区适栽松种的选择

简要介绍了美国主要南方松的天然分布、生长习性、本土人工种植情况、遗传改良状况及主要工业用途等。提出了江西省各生态区适栽松种。     

角胚跳小蜂属在我国的首次记录及其一新种记述(膜翅目:跳小蜂科)

本文报道两种寄生螟蛾科害虫的跳小蜂,即采自越南河内寄生稻纵卷叶螟Ｃｎａｐｈａｌｏｃｒｏｃｉｓ ｍｅｄｉｎａｌｉｓ Ｇｕｅｎｅｅ的螟克角胚跳小蜂Ｃｏｐｉｄｏｓｏｍｏｐｓｉｓ ｎａｃｏｌｅｉａｅ（Ｅａｄｙ）和采自山东泰安寄生刺槐谷蛾Ｈａｐｓｉｆｅｒａ ｂａｒｂａｔａ （Ｃｈｒｉｓｔｏｐｈ）的三节角胚跳小蜂Ｃｏｐｉｄｏｓｏｍｏｐｓｉｓ ｔｒｉｓｅｇｍｅｎｔｉｓ Ｘｕ,ｓｐ．ｎｏｖ．新种。对新种进行了描述     

简述森林的生态效益

分析了森林对人类生存环境和农牧业的影响,提出协调森林效益的措施和建议。     

半干旱区造林技术探讨

文章探讨了在半干旱区目前应用较广的几种造林技术及其优势,为半干旱地区的造林提供参考。     

介绍一种带电磁过滤装置的机油专用滤油机

带电磁过滤装置的机油专用滤油机是利用电磁线圈产生的直流磁场,作用于具有较大导磁系数物,从机油中除去铁、铜等金属氧化物及其他杂质的一种装置。机油中的铁、铜等金属会被带磁的多层不锈钢网吸附住,达到过滤的作用。本文介绍了一种能对机油中含有的铁、铜等金属进行有效分离的滤油机。