Relationships of climate change and tree ring of Betula ermanii tree line forest in Changbai Mountain

Based on the tree-ring growth characteristics of Erman＇s birch （Betula ermanii charm.） and the relationships between it and climatic ）＇actors at elevation of 1950m, the sensitivity of tree lines in Changbai Mountain to climatic factors was assessed. The results indicated tree line forest in Changbai Mountain had an obvious sensitivity to climate factors. However, difference from other study sits is that the main climatic control factor on tree-ring growth was not current growth season temperatures, as might be expected, but previous winter and current March temperature. Although the precipitation in the region was quite abundant, the tree-ring growth was still significantly correlated with the precipitation during previous winter and current spring. Additionally, climatic factors which influenced the Erman＇s birch growth were not the yearly variables, but seasonal and monthly variables. Therefore, the reported increase in yearly mean temperature and total yearly precipitation since 1980s was not responded by sustained increase in ring widths in recent decades.     

声发射检测技术及其在木质材料无损检测中应用的展望

介绍了声发射检测技术的定义、原理和特点, 回顾了声发射技术的发展历史以及它在木质材料无损检测领域中的应用; 在此基础上提出声发射检测技术在木材科学与技术领域的应用前景。     

长白山林区天然阔叶林培育大径木高产林分的结构分析

采用省级固定样地和伐区调查设计中小班全林每木样地相结合的方法，以天然阔斗林高产大径木林分结构为载体，详细分析了影响该林分结构的三个主要因子：林木最大保留直径（LDT），相邻径级立木株数之比（q）和林分保留断面积（RBA）。分析结果表明，培育大径木的林分结构条件是；LDT不超过54cm，q的取值范围为1．2～1．6，RBA不超过30m^2。     

快速判断与排除风力灭火机常见故障

由于风力灭火机结构的特殊性,没有专门的配气机构和润滑机构,容易引起汽油燃烧不彻底,导致汽缸内积炭增多,使机具极易出现故障,同时,部分操作人员又缺乏专业维修知识,难以使机具长期处于良好状态。针对这种情况,从风力灭火机常见故障的直观表现入手,归纳总结了几种判断与排除方法。     

一种提取刺槐叶片DNA的有效方法

以刺槐叶片为材料,摸索出了一套改良的SDS法。与传统方法相比,该方法DNA收取量大,操作简单、纯度高、完整性好,适用于遗传工程的DNA制备。     

城市森林火灾成因及预防扑救技术

随着经济发展和人们生活水平的提高,人们更愿意在森林中或靠近森林的地方居住。但伴随而来的是居民用火对森林造成威胁,与此同时,森林火灾也对居民住宅带来隐患。住宅在森林中的出现导致森林火灾的危险性增高,住宅、木棚、院落、车库及其他建筑物分布靠近森林,也给森林火灾的预防和扑救敲响警钟,近年来"家火上山,山火进城"的情况屡有发生,需加强有关研究。       

日本森林资源增长特点与采伐利用政策

早在20世纪70年代日本就成为世界第1大木材进口国,近50年来其森林蓄积量净增长1.6倍。一个森林资源大国,长期大量地进口木材以满足其国内需求,因此有观点认为日本大量进口木材是为了保护本国的森林资源。文中重点阐述日本森林资源增长特点、木材进口动向、国产材利用政策等问题,以阐明日本为什么长期依靠进口木材而未能有效利用本国的森林资源和近年来日本政府推行的国产材利用政策及其成效。     

河南省特有种——荷花柳(新考)

荷花柳是河南特有植物,公开发表的文献资料较少。针对荷花柳的现有文献资料及实物考察,对荷花柳叶近轮生及花的形态进行了考证;基于河南野生资源状况调查,探索了荷花柳繁殖技术,并对其景观利用价值进行简单分析。     

楸叶泡桐杂种无性系9503的组织培养技术研究

以楸叶泡桐和白花泡桐杂交无性系的枝条为外植体,开展了离体芽增殖技术,以及愈伤组织诱导、芽分化和不定芽生根等组织培养技术的研究。结果表明,增殖培养基采用MS+8mg/L6-BA+0.3mg/LNAA,不定芽的增殖倍数可达到9;利用其叶片进行愈伤组织诱导的最佳培养基为MS+12mg/L6-BA+0.4mg/LNAA,诱导率高达95%;愈伤组织分化的最佳培养基为MS+10mg/L6-BA+0.7mg/LNAA,不定芽生根的最佳培养基为1/2MS+0.5mg/LIBA+0.3mg/LNAA,生根率100%。     

Effect of nitrogen addition on DOC leaching and chemical exchanges on canopy leaves in Guangdong Province,China

The impact of nitrogen(N)deposition on dissolved organic carbon(DOC)fractions in throughfall is not well understood.We performed a laboratory experiment and compared DOC leaching from canopy leaves after dipping leaves in pure water(control)and NH4NO3 solution(N-treatment)for 18 h.Net changes of DOC,NH4^+,NO3^-,SO4^2-,K^+,Mg^2+,Ca^2+and H^+contents after dipping leaves were determined by comparing solutions with and without leaves.We recorded no differences of DOC leaching between control and N-treatment,implying that N deposition had minor impacts on canopy DOC production.This confirmed that previous experiments testing the effects of N addition on DOC dynamics without considering the effects of the canopy reaction successfully described the real situation.We also confirmed the previously-reported canopy exchange process in spite of a high background N deposition at our study site.N-treatment significantly increased base cation leaching,especially K^+,and the increase was positively correlated with foliar NH4?retention.Net leaching of H^+and SO4^2-was not affected by the N-treatment.