保水剂是一种高分子聚合物,其具有抗旱、节水、保水的作用,可大大提高干旱地区的造林质量.在我国保水剂在油松、侧柏等多个树种的推广与应用效果明显,由于其保水效果好、成本低,在我国的应用越来越广泛.文章主要针对抗旱造林中保水剂的应用技术进行分析.

扦插育苗造林能保存原优良植株的性状,生产力和经济效益较高,是扩大森林培育面积,营造速生丰产林的有效手段.本文从插穗条的培育、微量元素的使用、覆膜扦插三个方面探讨了杨树扦插育苗的造林技术.

通过采取生物防治、化学防治、物理防治和加强抚育措施，对森林鼠害治理进行防治效果对比实验，在研究治理成效的同时，从成本分析其投入与生态效益和经济效益产出比例，结果显示：物理防治树干套管措施和割灌除草投入成本最低，产生的经济效益和生态效益最佳。

In this paper ,the occurrence and control measures of the forest rodent pest in the mountainous area of northern Hebei Province are studied ,using the trap capture and the sta-tistical method to investigate rodent species and density .Through step-driving investigation the number of main rodent species was determined and prevention effects of five measures in-cluding chemical control ,physical control ,biological agent control ,biological control and silviculture ware comparatively analyzed .The results showed that Clethrionomys ruf ocanus is the main rodent threating the security of regional forest resources and mainly harming pines with the damage peak occuring in July and August as the key prevention and control period .The physical control (stem casing) and silvicultural measure (brush weeding) proved to have the best control effect ,reaching 83% and 89% respectively ,with high maneuver-ability ,and feasibility for generalization in large area w hile biological control as a fundamen-tal solution to the forest rodent pes had a long-term effective cycle ,without obvious effect in the short time .As for the biological agent control it provwed to be the poorest .

The diameter structure is very important for managing forests.On the basis of 15 plots of Larix principis-rupprechtii Mayr. plantation in Chengde Xinfeng Forest Farm,this paper analyses the diameter distribution of Larix principis-rupprechtii Mayr. plantation by Weibull distribution,and then uses x2 test to test the result of Weibull distribution.The result shows that 66.7% plots fit the Weibull distribution without rational fitting effect,which indicates an unreasonable diameter distribution of Larix principis-rupprechtii Mayr. plantation and therefore,the stand density should be corrected.

采用相对生长模型W=a（D2H）b对不同林龄华北落叶松人工林生物量进行了研究。结果显示,随着林龄的增大,树干的生物量增长的速度最快,树皮、树枝和树叶的生物量所占全株的比例随着林龄的增大而减小;6 a生林中,乔木层各器官生物量分配规律为树枝＞树干＞树皮＞树叶＞树根;12 a生林2、2 a生林和32 a生林中,分配规律为树干＞树枝＞树根＞树皮＞树叶;灌木层和草本层所占比例随着林龄的增大而减小,由6 a生林的9.28%和15.72%减小到0.46%。

火炬树引入我国半个多世纪以来,表现了优良的生物学特性,引起大面积栽植,近年又适逢退耕还林工程,火炬树开始大量繁殖,成为林业界专家们讨论的焦点,其是否应该划入入侵树种行列存在两种截然不同的观点,该文论述了火炬树当前现状,指出应慎用火炬树。

Application of the typical plot survey method and relative growth method of the biomass of Larix principis-rupprechtii Mayr.plantations in Yanshan mountainous regions were studied,In order to reveal the biomass allocation.the results show,The size order of every organ′s biomass in arbor layer was trunks>branchs> roots>leaves>barks,the trunks of 12 years old and 34 years old to the total biomass were 35.16%-37.95% and 51.12%-53.40%;the better site conditions,the greater tree age,the greater biomass,stand more stable,the small coefficient of variation;this study also obtained that the small upper leaf crown biomass,but due to the small BNR,the large BNI and FC,compared with lower crown greatly improve the photosynthetic efficiency.

Biodiversity and biomass of plantation community in three different types of Larix princicpis-rupprechtii Mayr.in Yanshan Mountainous Region were studied in this paper.The results showed:(1) The number of plant species of both mixed stand of Larix princicpis-rupprechtii Mayr.and Betula platyphylla Suk.and that of Larix princicpis-rupprechtii Mayr.and Populus davidiana Dode.was higher than the one of Larix princicpis-rupprechtii Mayr.forest.The dominant species were significantly different in three types of plant communities;(2) The order of α biodiversity index of three types of plant communities from high to low was herb layer,shurb layer and tree layer,and α biodiversity index in mixed stand was higher than that of pure stand.(3) In Larix princicpis-rupprechtii Mayr.stand,the propotion of biomass of tree layer was 99.33%,which was higest among three types of plant communities.The order whose allocation of different organ biomass was trunk branches root bark leaves,and the propotion of each organ in the whole biomass was different.