甘肃中部地区青杨沙棘混交效果初探

在干旱贫瘠、水土流失严重的甘肃中部生态林业建设中，采用杨树沙棘混交模式，不仅能充分利用生长空间，而且杨树生长量提高1倍以上。单位面积上生物量增加，土壤养分显著提高，病虫害明显减少，水土流失得到有效控制，林业生态效果明显。     

阜新地区沙棘林地土壤理化性质研究

在阜新蒙古族自治县选择不同生长阶段的沙棘林下的土壤为主要研究对象,对其理化性质进行了测定。结果表明:随着沙棘年龄的增长,沙棘林下土壤容重逐渐降低,土壤总孔隙度、毛管孔隙度、最大持水量、毛管持水量、最小持水量均提高;土壤pH值随林龄增加而降低,土壤有机质、全氮、速效氮、全磷、速效磷等化学指标均随林龄增加而增加;全钾和速效钾含量随沙棘林龄的增加而减少。     

油松-沙棘混交模式对生境和油松生长的影响

在陕北黄土丘陵沟壑区,以油松纯林为对照,对油松与沙棘行状混交、行状混交沙棘平茬、带状混交、宽行混交和宽行混交沙棘平茬林地的沙棘郁闭度、高度、光照强度、土壤水分、土壤密度、土壤空隙度、土壤养分及油松的存活率、高度、地径、顶梢年生长量等进行13年的监测研究.结果表明:行状混交与宽行混交的沙棘郁闭度、高度均高于行状混交沙棘平茬、宽行混交沙棘平茬和带状混交;林地的光照强度为油松纯林的较高,带状混交、宽行混交沙棘平茬、行状混交沙棘平茬的居中,宽行混交和行状混交的较低;土壤储水量在11年后表现为行状混交与宽行混交的较高,行状混交沙棘平茬、带状混交与宽行混交沙棘平茬的居中,油松纯林的较低;土壤密度、土壤空隙度、土壤养分表现为沙棘郁闭度、高度越高,土壤密度越低,土壤空隙度、土壤养分越高.与油松纯林相比,行状混交和宽行混交油松的高度和地径在6年以后明显较低,存活率在7年以后显著降低;行状混交沙棘平茬、宽行混交沙棘平茬与带状混交的油松高度在7年以后较高,行状混交沙棘平茬与宽行混交沙棘平茬的油松高度在10年以后高于带状混交的油松;行状混交沙棘平茬、宽行混交沙棘平茬与带状混交的油松地径在9年以后大于油松纯林的油松地径;行状混交沙棘平茬、宽行混交沙棘平茬和带状混交的油松顶梢年生长量在6年以后较大,行状混交和宽行混交的较小.油松与沙棘混交,行状混交沙棘平茬、宽行混交沙棘平茬和带状混交促进了油松的生长,行状混交和宽行混交降低了油松的存活率,抑制了油松的生长.     

长江上游地区林业生态建设与治理模式(续)

6 .7　低山、丘陵区松栎混交模式6 .7.1　模式适宜条件　本模式处于低山丘陵地貌类型 ,年平均气温15℃ ,年降水量 110 0mm ,土壤为黄壤和紫色土。6 .7.2　技术思路　在立地条件较差的宜林荒山 ,可采用先封山育林 ,后补植补造的方法 ,培育松栎混交林。马尾松是乡土针叶树种 ,栎类是落叶阔叶树种 ,实施松栎针阔混交 ,有利于改善土壤结构 ,促进林分生长 ,防止病虫害 ,增强水土保持功能 ,形成稳定的森林生态体系。6 .7.3　主要技术措施(1)树种与配置　选择马尾松与麻栎带状混交 ,4行马尾松 2行麻栎。三角形配置。马尾松株行距 1.0m×1.5m ,每 6 …     

长江上游地区林业生态建设与治理模式(续)

<正> 6.8 农村能源开发薪炭林治理模式6.8.1 技术思路 在农村人口稠密,缺少煤炭、天然气等燃料的地方,合理布局薪炭林。薪炭林以选择萌生能力强、热值高、生物量大的树种为佳,解决当地烧柴问题,同时辅以改灶节柴等措施,与农村能源开发相结合。6.8.2 主要技术措施 (1)主要树种 麻栎、栓皮栎、刺槐、紫穗槐、黄荆、马桑、桤木、槲栎、柏木、马尾松等。     

长江上游地区林业生态建设与治理模式(续)

3.2干热河谷剑麻造林治理模式 干热河谷的部分地区极度干燥、干热,土壤承载力低,降雨又较集中,这些特点造成原有森林由于火灾而遭到毁灭性破坏.另一方面是新造林很难成活,适应树种极少.剑麻,原产坦桑尼亚,为多年生喜光草类,在阳光充足的地方植株生长壮旺,叶片多、刚硬、纤维产量高.     

甘肃省绿色通道建设探讨

铁路、公路沿线绿化，是国土绿化的重要组成部分。根据本省目前铁路、公路绿化存在的问题，提出了结合退耕还林（草）政策，加快全省绿色通道建设的对策：合理选择树种，做到适地适树；采用先进造林技术，提高造林成活率；加强抚育管护；统一协调管理和制定合理计划，确保绿色通道建设。     

杨树黑斑病测报模型的研究

在北京郊区黑杨林地内设置固定样地,进行杨树黑斑病Marssonina brunnea病原菌孢子捕捉和病情调查。运用数量化理论I系统分析了病情指数与气象因子之间的关系,结果表明:当平均气温20～28℃、平均相对湿度80%以上、降雨量为60 mm以上时,杨树黑斑病的病情发展迅速。同时建立了杨树黑斑病的数量化测报模型:^yi=-5.236 1x(1,1)+7.388 4x(1,2)-3.045 7x(1,3)-6.231 5x(2,1)-4.540 9x(2,2)+6.261 8x(2,3)+20.496 3x(2,4)+1.146 6x(3,1)+3.613 4x(3,2)+7.025 7x(3,3)+19.680 2x(3,4)。对测报模型检验的预测精度在88.49%～96.43%之间。     

浅析河西地区城市居住区园林绿化建设

通过对河西地区城市居住区环境绿化状况的调查，分析了目前居住区环境绿化所取得的成绩，同时据存在的主要问题，提出今后河西地区城市居住区环境绿化应从建设机制、规划设计１科学管理和提高居民环保意识等方面进一步提高，才能真正建成可持续发展的人文环境，以满足居民对物理文明和精神文明的需求。     

杨树纸浆林优化栽培模式的研究

从 1 991～ 2 0 0 0年历时 9a时间 ,进行了杨树纸浆林造林模式、土壤施肥、叶面喷肥、林粮间种、纸浆林基地建设等研究和开发。结果表明在辽西地区杨树纸浆林的造林模式为 :造林品种应优先选择辽宁杨、荷兰 3930杨、盖杨、辽河杨等 ;造林最佳密度为 1 1 1 1～ 1 6 6 6株 /hm2 ;配置方式应以宽行密植和宽行窄带为主 ,如 1m× 6m、1 5m× 6m、(1× 4 )m× 8m、(1 5× 4 )m× 8m等。纸浆林的主伐年龄为 6～ 7a。在金城原种场的立地条件下 ,无论是土壤施肥 ,还是叶面喷肥对林木生长影响均不显著。林粮间作方面 ,改变造林由常规方式为宽行窄带和宽行密植后 ,间种年限可提高 1～ 2a ,间种面积可提高到 2 0 % ,产量提高 30 %～ 5 0 % ,经济效益显著提高     

林农复合种植模式在城市绿地中的应用

通过对城市绿地的功能和林农复合种植模式的研究,将"林农复合"理念引入城市绿地建设,构建具有生产、生态、景观和社会文化交流的多功能相互关联、紧密相连、和谐的景观绿地,进一步完善和拓宽了城市绿地系统,同时在城郊结合部营造城市中的田园景观提供了案例。       

窄冠黑杨、窄冠黑白杨的选育及应用

通过杂交育种 ,选出了 6个窄冠黑杨、1个窄冠黑白杨无性系 ,材积生长量分别接近对照I—6 9/ 5 5、中林4 6和窄冠白杨 3号。窄冠黑杨单株立木干物质产量超过中林 4 6 ,冠幅比对照小 1/ 2～ 1/ 3,适用于农田林网及农林间种。窄冠黑杨耐盐碱能力较强 ,容易扦插繁殖 ,造林成活率高。木材基本密度 36 0～ 394kg/m3 ,木材纤维长 1mm左右 ,随年龄增长而加长 ,5a生时趋于稳定。因此从制浆造纸来看 ,以 5a生以上利用为好。经制浆及检测、胶合板制作证明 ,木材适用于制浆造纸及作胶合板原料。     

Competition control in juvenile hybrid poplar plantations across a range of site productivities in central Saskatchewan,Canada

The response of hybrid poplar plantations established on former agricultural land in Saskatchewan to competition from weeds on a range of site productivities was studied. The short-term impact of competition control on the growth of juvenile trees and how tree responses to competition control differed across the productivity gradient was of particular interest, as was the determination of which resource was most highly competed for and was most important in determining tree growth. Eight sets of paired plots in juvenile hybrid poplar plantations were established in central Saskatchewan across a range of site productivities. In each pair, one plot had complete weed control (weed-free) while in the other plot weeds were allowed to grow. The best soil predictor of tree growth was soil texture, represented by a combination of the percentage silt and clay, with finer textures showing better growth. Competition control significantly increased tree growth on all sites with the benefit being greatest on the higher productivity sites. Soil water appeared to be highly competed for between trees and weeds and was a dominant resource controlling growth. For soil nutrients, nitrogen and phosphorous were highly competed for between trees and weeds. However, leaf phosphorous concentration of the weed-free plots had a strong positive relation to tree growth while nitrogen did not, indicating that when trees are free of competition they can access sufficient nitrogen from these soils.     

Elastic parameters of poplar wood with end-cracks

? In this study, longitudinal specific modulus of elasticity along the grain (specific MOE_L = MOE_L/ρ) as well as radial and tangential shear moduli (G _LR and (G _LT ) of Populus Deltoides wood were examined in free flexural vibration in a free-free bar method, where end-cracks produced manually in LT plane along and parallel to annual rings in four different sizes.

? The effects of four different crack sizes (0, 6, 12, and 18 cm) on elastic parameters of the bars were examined for their vibration properties based on Timoshenko bar equations, in order to find a procedure to make a confident choice of a clear specimen among the cracked ones, considering three initial modes of vibration.

? Based on research findings, a significant correlation existed between radial and tangential shear moduli of the clear bars as G _LR was approximately 15 percents higher than (G _LT . After making the shortest crack sizes, however, this correlation entirely faded. Statistically for 6 cm crack, decreases in specific MOE _L for measurement on the tangential impact were not significant though they were for longer cracks.

? It was also revealed that in specimen under the study if longitudinal specific modulus of elasticity from both LR and LT flexural vibrations were almost equal and G _LR was slightly larger than (G _LT , the user could be confident enough to consider the specimen without severe longitudinal cracks.

     

南方型杨树人工林经营模型系统及其应用

针对南方型杨树各主栽区多为混系造林的生产实际,将南方型杨树整体作为研究对象,开展了南方型杨树人工林经营模型系统的研究。根据213个南方型杨树同龄林标准地资料,建立了集经营模拟、经济效益评价、优化决策于一体的南方型杨树人工林经营模型系统并开发了相应的软件,介绍了该系统的结构与功能并举例说明其应用。南方型杨树人工林经营模型系统的建立为南方型杨树模式化定向培育理论的实现提供可靠的工具,对南方型杨树人工林经营具有直接的指导作用。     

Experimental study of the mechanical behaviour of thin slices of maturating green poplar wood using cyclic tensile tests

In this study, longitudinal cyclic tensile tests were performed on green wood samples of Populus cv I4551. Complex mechanical behaviour, such as permanent set in terms of displacement and strain-dependent stiffness, was found. A linear relationship between stiffness and strain enabled each sample to be characterized. A large-scale experimental campaign led to the observation of the evolution of temporal and spatial intra-ring mechanical behaviour of intra-ring sliced specimens during wood maturation and tree gravitropic response. The results showed that tension wood lamellas exhibit strain hardening behaviour whereas normal wood lamellas exhibit strain softening behaviour. Temporal variations in the strain hardening behaviour of tension wood lamellas occurred once cell wall deposition was achieved. Moreover, no correlation was found between infradensity and mechanical behaviour of lamellas. These results show that cells undergo temporal variations in their properties due to a complex maturation process.