共查询到20条相似文献，搜索用时 78 毫秒
1.
欧洲实践证明, 有效制定和实施林业政策能够推动城市林业的发展, 从而有效改善城市人居环境和促进居民身心健康。文中在收集关于中国和欧洲城市林业方面的文献以及对中国和欧洲进行城市林业实地考察的基础上, 对中国和欧洲城市林业政策与规划、城市林业管理手段、发展城市林业的工作方法进行了比较, 目的是吸收欧洲在城市林业政策制定和实施过程中的先进经验和最佳实践, 提高中国城市林业的政府决策者、管理人员、研究人员、利益相关者和社区在城市林业政策制定和实施方面的知识和能力, 改善中国城市和城市周边地区的环境质量, 最大限度发挥城市林业促进居民身心健康和福祉的作用。 相似文献
2.
随着经济发展和社会进步,人类对于森林的认识不断深化,人类保护和利用森林的方式不断创新。近年来,森林在全球经济社会发展和生态环境保护中的地位和作用日益突出和增强。 相似文献
3.
4.
今年第1季度,我国从海关进口原木和锯材数量分别为5601498m3和1523418m^3;价值金额分别为793935374美元和369089536美元。其中从南京海关和满洲里海关进口的原木和锯材数量分居全国第一、二名。从南京进口原木数量为1479780m^3、价值金额为243211027美元;分别占全部进口原木总量和价值金额的26．42％和30．63％。 相似文献
5.
6.
研究不同温度梯度(0℃、5℃和10℃)及不同处理时间(10d、20d和30d)对缬草种子萌发及过氧化物酶和淀粉酶活性的影响。结果表明:5℃30d条件下发芽率为39.7%,且种子中过氧化物酶和淀粉酶活性最高;0℃10d和0℃20d条件下发芽率仅分别为13.3%和19.3%,种子中过氧化物酶和淀粉酶酶相对较低。在同等低温条件下,种子的发芽率和发芽势随着处理时间的延长而增高,过氧化物酶和淀粉酶的活性也越高。低温处理能有效的提高缬草种子的发芽率和发芽势,不同处理会造成缬草种子发芽指标和酶活性的差异。 相似文献
7.
8.
《绿色中国(A版)》2014,(19):7-7
17个城市获＂国家森林城市＂称号
这17个城市是：山东省淄博市和枣庄市、河北省张家口市、江苏省镇江市、浙江省温州市、安徽省合肥市和安庆市、江西省吉安市和抚州市、河南省郑州市和鹤壁市、湖北省襄阳市和随州市、湖南省郴州市和株洲市、广东省惠州市、四川省德阳市。 相似文献
9.
10.
《防护林科技》2020,(4)
通过对沙枣进行扦插育苗和播种育苗试验,分析了2种育苗方法的效果,结果表明:沙枣扦插育苗苗木成活率65.0%,当年平均高生长量和地径生长量分别为58 cm和0.63 cm,第2年平均高生长量和地径生长量分别为104 cm和1.08 cm。春秋季种子育苗苗木出苗率分别为75.5%和93.5%,春季育苗当年平均高生长量和地径生长量分别为38 cm和0.37 cm,第2年平均高生长量和地径生长量分别为97 cm和0.86 cm;秋季播种1年生平均高生长量和地径生长量分别为40 cm和0.38 cm,第2年平均高生长量和地径生长量分别达到95 cm和0.87 cm。沙枣播种育苗出苗率高,单位面积载苗量大,经济效益高。 相似文献
11.
本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。 相似文献
12.
森林冠层结构与功能及其时空变化研究进展* 总被引：16，自引：0，他引：16
林冠是森林与外界环境相互作用最直接和最活跃的界面层 ,同时 ,它本身又承载了森林生物多样性的主体部分。森林冠层研究的方法和技术在近些年取得了长足发展 ,从而促进了有关林冠结构与功能的研究。这些研究深化了人们对于林冠结构与光能截获以及群落干物质积累之间关系的认识 ,同时 ,对于森林冠层的物质循环和能量传输以及冠层内各营养级之间相互关系动态也有了更为深入的理解。考察森林冠层的结构与功能及其时空变化是深入理解整个森林生态系统的格局、过程及其运作机制的重要基础。 相似文献
13.
《Scandinavian Journal of Forest Research》2012,27(1-4):457-469
The persistence of the four herbicides atrazine, hexazinone, lenacil and linuron was studied in forest nursery soils. The adsorption capacities of the soils for the chemicals were described by the distribution coefficients kj and koc. Due to the low content of organic matter in the soils the ka‐values were low, in several cases being <1 for hexazinone. Hexazinone also had the lowest k oc‐value (30) while the other substances had koc ‐values within the range 200–400. In some cases hexazinone showed great mobility under field conditions. The formula c=co‐kt1/2 was used to describe the disappearance of the herbicides from the various soils. The rate of degradation of the four herbicides correlated well with the rate of respiration in the same soils in laboratory experiments, and for linuron reasonably well also in field experiments. In the field experiments the herbicides penetrated the top soil layer. In the subsoil the risk of further transport downward to the drainage system or ground water increased, especially for hexazinone. Linuron as well as the fungicides maneb and tolylfluanid suppressed the decomposition rate of hexazinone in laboratory experiments. 相似文献
14.
刘宏明 《绿色中国(A版)》2005,(10):42-43
野生动物所有权是所有权的一种,它与其他所有权的区别在于客体的不同。文章阐述了野生动物的内涵,分析了野生动物的分类和野生动物与野生动物资源的区别。在明确野生动物含义的基础上,提出了野生动物所有权的概念,深入论述了野生动物所有权与野生动物资源所有权的差异和联系,并对野生动物所有权的主体、客体、内容进行了分析。 相似文献
15.
16.
Pedro Ah Shenga Peter Bomark Olof Broman Dick Sandberg 《Wood material science & engineering》2017,12(4):257-262
The sawmill industry is a very important link in the Mozambique forest products value chain, but the industry is characterized by undeveloped processing technology and high-volume export of almost unrefined logs. The low volume yield of sawn timber has been identified as a critical gap in the technological development of the industry. To improve the profitability of the industry, there is thus a need to develop methods and techniques that improve the yield. In this paper, different positioning of logs prior to sawing and the possibility of increasing the volume yield of crooked logs by bucking the logs before sawing have been studied. A computer simulation was used to study the cant-sawing and through-and-through sawing of the logs to determine the volume yield of sawn timber from the jambirre (Millettia stuhlmannii Taub.) and umbila (Pterocarpus angolensis DC.) species. The optimal position, i.e. the position of the log before sawing that gives the highest volume yield of sawn timber for a given sawing pattern when the positioning parameters, offset, skew and rotation, are considered gave a considerable higher volume yield than the horns-down position. By bucking very crooked logs and using the horns-down positioning before sawing, the volume yield can be of the same magnitude as that obtained by optimal positioning on full-length (un-bucked) logs. The bucking reduces the crook of the logs and hence increases the volume yield of sawn timber. 相似文献
17.
丽水市竹产业化建设进展与思考 总被引：4，自引：0，他引：4
丽水市是浙江省竹类的重点产区之一。竹子产业化是丽水市“十·五”期间农业产业化的重点。该文分析了丽水市竹产业化提出的背景 ,总结了竹产业化建设取得的主要进展 ,根据发展中存在的问题 ,在观念改变和机制创新、强化科技支撑作用、培植龙头企业、建立运销服务体系以及加强小径竹开发利用等方面进行了深入的思考。 相似文献
18.
Julia Janke Martina Bandte Christian Ulrichs Giselher Grabenweger Barbara Jäckel Hartmut Balder Carmen Büttner 《Journal of pest science》2009,82(1):47-53
The parasitoid wasp Pnigalio agraules (Wlk.) is a key natural enemy of the horsechestnut leafminer Cameraria ohridella Deschka and Dimić (Lepidoptera: Gracillariidae). As a basis for mark-release-recapture studies, aimed at investigating the
dispersal of this parasitoid in the field, adults of P. agraules were marked using a vertebrate-specific immunoglobulin (IgG). The marker was later detected by double antibody sandwich enzyme-linked
immunosorbent assay (DAS-ELISA). The IgG was either applied externally by spraying or internally by feeding an IgG-enriched
diet. Different concentrations of the marker were used and the influence of abiotic (climatic conditions, time elapsed between
marking and marker examination) and biotic factors (sex and age of the parasitoids) on the detection of the immunomarker was
tested. External marking by spraying led to more homogeneous labelling than feeding the marker. Parasitoids labelled with
0.25 mg rabbit IgG per ten individuals contained enough immunomarker to be easily distinguished from unmarked ones. Neither
the climatic conditions nor the sex or age of the insects had an influence on the detection of the marker. The IgG remained
well detectable during the entire lifespan of the parasitoids, which was not negatively affected by the marking procedure.
Serological marking can be used to investigate the dispersal behaviour of beneficial insects within mark-release-recapture
studies. 相似文献
19.
胡云楚 《中南林业科技大学学报(自然科学版)》1994,(2)
本文探讨了用苯芴酮萃取分光法测定微量锗的实验条件和步骤．结果表明，用此法测定微量锗灵敏度高、操作简便、准确，是测定微量锗的较好方法．可用于对植物和食品中的微量锗进行检测． 相似文献
20.
大兴安岭森林资源变化分析 总被引：11，自引：0，他引：11
阐述了人为破坏、过度采伐和自然森林火灾是引起大兴安岭森林资源变化的重要因子;通过对建国初到2002年大兴安岭森林资源在数量上和质量上的变化分析,得出了森林资源变化趋势。森林资源数量减少,且森林质量下降,大兴安岭的森林在经历着破碎化和年轻化的过程。 相似文献