丽江市退耕还林工程造林树种选择评析

介绍了丽江市退耕还林工程实施的基本情况和树种选择的详细情况,分析了工程所选择树种的结构及分布,对所选树种的造林成效进行了评价,分析指出了存在的问题,提出了丽江市退耕还林工程树种选择的相关建议,推荐了一些适合在丽江退耕还林工程中选用的树种.     

新型建筑实木窗的生产发展

对新型建筑实木窗产生的背景和生产发展历程进行了系统阐述。就材料选择进行了分析并指出,落叶材质坚硬、纹理通直、力学强度高,是新型建筑实木窗的主要原料。给出了产品性能、产品结构、生产工艺和设备选用。     

核桃优质苗木培育技术研究

针对核桃产业开发对优质苗木的需要，通过对成县川坝、丘陵、山区不同立地类型区建立核桃苗圃、种子选择处理、嫁接砧木选用、嫁接时间方法、苗期管理技术和苗木出圃质量等指标进行了对比试验研究。结果表明：选择川坝区苗圃，选用黑核桃种子、沙藏催芽处理，高床地膜覆盖，培育优良砧木，春季单芽切接，夏季方块芽接，加强苗期管理，是培育核桃优势嫁接苗的关键技术措施。     

丽江市退耕还林工程造林树种选择评析

介绍了丽江市退耕还林工程实施的基本情况和树种选择的详细情况,分析了工程所选择树种的结构及分布,对所选树种的造林成效进行了评价,分析指出了存在的问题,提出了丽江市退耕还林工程树种选择的相关建议,推荐了一些适合在丽江退耕还林工程中选用的树种．     

木工硬质合金镶焊齿锯片的选用

介绍了木工硬质合金镶焊齿圆锯片及硬质合金材料的选用,阐述了锯片外径、齿数、齿形、角度参数以及特殊锯片和适张度的选择。     

我国城市市树选择应用现状及区域分布特征

市树是城市形象的重要标志和文化名片,科学选用市树对于优化城市人文生态环境、促进地方文化的传承和发展能起到积极的推动作用。本文利用国家林业局2017年全国市树调查统计数据,对我国34个省级行政区域的348个地级以上城市的市树选用情况进行统计分析和归纳汇总,探讨市树的选择程序与确定原则,分析我国市树选择应用整体状况、区域分布特征和市树应用中的有关问题,以期为我国城市市树选择应用与绿化工作提供参考。分析结果表明:我国目前共有245个城市已确定市树,占全部城市总数的70.4%,并有27个城市同时选用两个树种作为市树,其中,北京、天津和重庆三个直辖市及河北、江苏、浙江和江西4个省份的全部地级城市已完成市树的选定工作;从树种组成来看,市树种类涵盖29科56属的81个树种,主要集中在松科、豆科、蔷薇科、木犀科、柏科、樟科等,其中国槐、香樟和银杏是选用率最高的三大市树树种,分别被49、49和19个城市选做市树,占已选定市树城市总数的20.0%、20.0%和7.8%,同时,榕树、黄葛树和小叶榕等也是南方城市常用的市树种类;从地理区位的比较来看,我国北方地区城市选用国槐、雪松、油松、榆、垂柳和白蜡等树种作为市树较多,长江流域沿线城市市树选用香樟、油樟、栾树、玉兰等树种较多,东南沿海地区城市选择香樟、凤凰木、扁桃树、桂花等树种作为市树的城市较多;我国不同区域城市的市树选择各具特色,华北、西北地区国槐选用率最高,分别占该区域内已选定市树城市总数的53.3%和50.0%,华中、华东地区香樟选用率最高,分别占该区域内已选定市树城市总数的46.2%和20.3%,而港澳台地区则与华南地区城市在市树选择上有一定的相似性,其重合度达50%。同时,市树选用过程中还存在应用不广泛、运用不合理、名称不规范等诸多问题,科学规范地选用市树仍是我国城市绿化建设过程需要进一步加强的发展方向。     

园林地被植物的选择与应用

通过对地被植物概念的阐释,指出了地被植物选用的基本原则,在此基础上分析了园林地被植物种类的选择和应用的基本形式,并进一步提出了地被植物应用中应注意的主要问题。     

仁用杏的高产栽培

一、选用优良品种　仁用杏品种可选用大扁、次扁、一窝蜂、白玉扁、串铃扁。授粉树选山杏、串枝红。二、园地选择　仁用杏主要适宜在年平均气温6～ 1 2℃的地区 ,冬季最低温 - 38℃的地方仍可越冬。对土壤适应性很强 ,抗寒、抗旱、耐瘠薄 ,在平原沙荒、丘陵荒山、坡地梯田、田旁隙地都能丰产。主要影响生产的问题是花期和幼果期的晚霜冻 ,选择园地时一定要注意小气候条件 ,选择背风向阳地势高燥 ,地形开阔的坡田、梯田、避开风口 ,防治春季寒流侵袭和晚霜冷空气沉积造成冻花冻果。三、苗木定植　定植选用 2ａ生壮苗。以春季萌芽前定植为宜 ,…     

浅议大同市高速公路两侧及周边荒山造林绿化

笔者对大同市各县区高速公路两侧及周边荒山绿化工程进行了调查分析,从造林苗木的选用、包工队的选择、造林时间的选择3个方面阐述了造林设计中需要注意的问题,提出了合理设计浇水路线、整地、起苗、栽植、后期管理等造林技术要点,最后讨论了造林绿化过程中的组织与管理问题。     

小议提高用材林森林生产力的途径

通过选用适当的培育方式、遗传改良、林分结构的配置、立地的选择和调控等4个方面的分析论证,论述了寻求提高用材林的森林生产力的途径。     

Forest thinning and soil respiration in a ponderosa pine plantation in the Sierra Nevada

Soil respiration is controlled by soil temperature, soil water, fine roots, microbial activity, and soil physical and chemical properties. Forest thinning changes soil temperature, soil water content, and root density and activity, and thus changes soil respiration. We measured soil respiration monthly and soil temperature and volumetric soil water continuously in a young ponderosa pine (Pinus ponderosa Dougl. ex P. Laws. & C. Laws.) plantation in the Sierra Nevada Mountains in California from June 1998 to May 2000 (before a thinning that removed 30% of the biomass), and from May to December 2001 (after thinning). Thinning increased the spatial homogeneity of soil temperature and respiration. We conducted a multivariate analysis with two independent variables of soil temperature and water and a categorical variable representing the thinning event to simulate soil respiration and assess the effect of thinning. Thinning did not change the sensitivity of soil respiration to temperature or to water, but decreased total soil respiration by 13% at a given temperature and water content. This decrease in soil respiration was likely associated with the decrease in root density after thinning. With a model driven by continuous soil temperature and water time series, we estimated that total soil respiration was 948, 949 and 831 g C m(-2) year(-1) in the years 1999, 2000 and 2001, respectively. Although thinning reduced soil respiration at a given temperature and water content, because of natural climate variability and the thinning effect on soil temperature and water, actual cumulative soil respiration showed no clear trend following thinning. We conclude that the effect of forest thinning on soil respiration is the combined result of a decrease in root respiration, an increase in soil organic matter, and changes in soil temperature and water due to both thinning and interannual climate variability.     

基于单片机的水温恒温模糊控制系统设计

提出一种基于单片机的水温恒温模糊控制系统,利用温度传感器18B20对水温进行实时采集,通过3*3键盘输入温度设定值,对检测值与温度设定值进行比较,以温度偏差量和加热时间为输入信号,以不同温度调节器的工作状态为输出量,通过模糊控制算法实现水温恒温的自动控制。     

高温热处理木材吸湿特性

【目的】研究高温热处理对人工林樟子松、杉木、美洲黑杨木材平衡含水率和吸湿特性的影响,为科学评价热处理木材吸湿特性提供理论基础,为人工林木材高附加值利用和实际高温热处理木材生产提供参考。【方法】以水蒸气为保护介质,设定180、200和220 ℃3个温度进行高温热处理,采用双室温、湿度控制法,在25 ℃环境中以8种不同类型饱和盐溶液精确控制水蒸气相对湿度进行等温吸附试验,运用Hailwood-Horrobin模型拟合等温吸附曲线,分析高温热处理对木材水蒸气等温吸附曲线线形、平衡含水率、单层分子吸附水和多层分子吸附水的影响。【结果】 180、200和220 ℃处理后,试样吸湿平衡含水率均值相当于素材含水率均值的80%、70%和50%左右;3个树种素材试样和高温热处理材试样均表现为第2类等温吸附曲线形态特征,Hailwood-Horrobin模型能够较好拟合不同树种素材和高温热处理材等温吸附曲线,不同热处理条件试样等温吸附曲线的拟合度均高于0.980 0,处理温度越高,等温吸附曲线越接近直线;高温热处理后代表含有单位摩尔数吸附位的绝干木材质量参数( W )显著增加,不同相对湿度下高温热处理材的单层分子吸附水和多层分子吸附水含量也随之降低;180、200和 220 ℃处理后,木材试样单层分子吸附水含量相较于素材下降20%、30%和50%左右,高温热处理对多层分子吸附水含量影响规律与之相近;高温热处理后单层分子吸附水、多层分子吸附水和吸附水总量的最大值相较于素材明显下降,且处理温度越高,下降幅度越大。【结论】高温热处理可明显降低3个树种试样的吸湿平衡含水率,且处理温度越高,平衡含水率下降幅度越大;高温热处理会一定程度影响木材等温吸附曲线线形,Hailwood-Horrobin模型可用于描述高温热处理材等温吸附曲线,且拟合度较高;高温热处理可明显降低3个树种试样等温吸附过程单层分子吸附水和多层分子吸附水含量,且处理温度越高影响越明显,单层分子吸附水和多层分子吸附水最大含量均明显降低,进而影响吸附水总量最大值。     

华山松种子不同处理方法育苗试验

采用正交试验设计,研究不同层积时间、不同水温浸种以及变温和恒温处理方式对华松山种子播种育苗的影响的结果表明:华松山种子层积60天效果好于90天,温水浸种好于凉水浸种,变温处理优于恒温处理,其中以温水浸种7天后,变温层积60天,华山松出苗率最高,且地径生长量最大。     

Epigallocatechin gallate content change of the fresh tea leaf homogenates extracted by different methods in extraction and preservation

Introduction Tea polyphenols, extracted from tea leaves, is a hydroxyl phenol compound. Of the components of green tea (Camellia sinensis), the content of (?)-epigallocatechin gallate (EGCG) is high, and this catechin has been extensively studied (Harold …     

鄂西红豆古树、初果树种子不同水温处理发芽对比试验

以鄂西红豆古树和初果树种子为材料,采用不同温度热水分别对两批种子进行浸种处理,再在圃地上进行播种发芽试验。结果表明:古树批种子发芽率高低的顺序为始温90℃热水浸种24h始温80℃热水浸种24h始温70℃热水浸种24h始温60℃热水浸种24h;初果树批种子发芽率高低的顺序为始温80℃热水浸种24h始温70℃热水浸种24h始温90℃热水浸种24h始温60℃热水浸种24h。古树批种子用始温90℃热水浸种24h处理方法发芽率最高,达84%;初果树批种子用始温80℃热水浸种24h处理方法发芽率最高,达85%。相同方法处理的种子(除始温90℃热水浸种24h外),初果树批种子比古树批种子的发芽率高。用90℃高温热水浸种处理,会造成初果树种子烫伤,严重影响发芽率,而古树种子不受影响。     

非等温条件下木片碎料中的水分迁移特性

实验表明,木片碎料中的水分迁移量与温度梯度场相似。从而应用最小二乘法拟合求算了两物理量场的相似倍数,建立了质流率与温度梯度间的通量关系式,揭示了温度梯度是水分迁移的主要推动力。其机理是通过湿空气在气相的自然对流和相伴产生的蒸发-凝结过程进行的。本文建立的水迁移通量关系式简化了现有的理论模型,为分析非等温条件下木片碎料中的水分迁移提供了新的理论思路,简化的理论模型可为实际应用带来方便。     

Water transport in wood particle material

An analogy between water flux and the field of temperature gradient in a column of wood fuel chips was discovered by these experiments. The heat—mass transfer coefficient was determined by least squares method. An equation relating water flux and temperature gradient was developed and it was demonstrated that the temperature gradient was the main driving force for water transport. The mechanism was evaporation—condensation of water vapor through natural convection in air phase. The study gives a theoretical explanation for analyzing the problem of water transport in wood particle material.     

Factors affecting relative humidity during wood vacuum drying

Effects of pressure and temperature in the chamber during vacuum drying on the relative humidity and evaporation of wood surface were investigated by using the vacuum chamber. The setting temperature during vacuum drying included dry-bulb temperature td, the wet-bulb temperature tw and the temperature difference between the air in the vacuum chamber and the cooling water in the condenser. Results indicated that relative humidity during vacuum drying was affected by the dry-bulb temperature td, the wet-bulb temperature tw and the temperature difference between the air in the vacuum chamber and the water in the condenser. Relative humidity of wood decreased with the increase in temperature at the given temperature of the water in the condenser. The relative humidity was affected slightly by pressure in the vacuum chamber pA, and it decreased from 70% to 65% with pA increased from 50 kPa to 101 kPa. Moreover, there was nearly no evaporation under the vacuum without external heating.     

Different sensitivity of isoprene emission, respiration and photosynthesis to high growth temperature coupled with drought stress in black poplar (Populus nigra) saplings

The effects of the interaction between high growth temperatures and water stress on gas-exchange properties of Populus nigra saplings were investigated. Water stress was expressed as a function of soil water content (SWC) or fraction of transpirable soil water (FTSW). Isoprene emission and photosynthesis (A) did not acclimate in response to elevated temperature, whereas dark (R(n)) and light (R(d)) respiration underwent thermal acclimation. R(d) was ~30% lower than R(n) irrespective of growth temperature and water stress level. Water stress induced a sharp decline, but not a complete inhibition, of both R(n) and R(d). There was no significant effect of high growth temperature on the responses of A, stomatal conductance (g(s)), isoprene emission, R(n) or R(d) to FTSW. High growth temperature resulted in a significant increase in the SWC endpoint. Photosynthesis was limited mainly by CO(2) acquisition in water-stressed plants. Impaired carbon metabolism became apparent only at the FTSW endpoint. Photosynthesis was restored in about a week following rewatering, indicating transient biochemical limitations. The kinetics of isoprene emission in response to FTSW confirmed that water stress uncouples the emission of isoprene from A, isoprene emission being unaffected by decreasing g(s). The different kinetics of A, respiration and isoprene emission in response to the interaction between high temperature and water stress led to rising R(d)/A ratio and amount of carbon lost as isoprene. Since respiration and isoprene sensitivity are much lower than A sensitivity to water stress, temperature interactions with water stress may dominate poplar acclimatory capability and maintenance of carbon homeostasis under climate change scenarios. Furthermore, predicted temperature increases in arid environments may reduce the amount of soil water that can be extracted before plant gas exchange decreases, exacerbating the effects of water stress even if soil water availability is not directly affected.