The spar is widely used in cable yarding on steep terrain. Spars are supported in an upright position by guylines. There are several methods for calculating stress in spar and guylines, but many of them have limitations. Prof. K. M. Askenazi and B. G. Zalegaler (VSSR) have suggested that it is the hardest situation when the major pull comes directly against one guyline. This will be true, however, only when the included angle between two guylines is less than 90 degrees. with the included angle more than qo degrees, that situation would not be the hardest. The major problem in calculating spar and guylines consist in frequent changing of inhaul pull direction, particularly in highlead systems. The guylines are attached to stumps arround the spar, which location may be anywhere. The aim of this paper is to provide an universal method and formula for calculating spar and guylines, and to explain the relationship between the spacing of guylines and the stress in both spars and guylines. Attempt has been made to find out the optimum guyline spacing, under which the guylines would be subjected to a minimum pull.

Sustained forest management at two cases are discussed, namely ideal center and non-ideal center. For ideal center, the cut is near maximum current annual increment, so that we have got a mathematical model as follows: (1/1+exp[-(1/2)λΔt])-(1/1+exp[(1/2)λΔt]=1/1+exp[(-1/2)λΔt] Where, Δt—a cutting cycle; λ—intrinsic rate of increase; D—selection cutting intensity expressed. by selection cutting quantity/present biomass of stand, unit time For various cutting cycles, relation between λ and D are tabulated and plotted, respectively. For non-ideal center, the cutting age is away from maximum current annual increment than ideal center, and relation, between λ and D are given. Various cutting limits are also discussed. Under continuous selective cutting condition, the mathematical model may be shown as follows: dω/dt=λω(1-ω/w)-Dω Where, ω——biomass of stand in unit area; W——maximum biomass of stand in unit area which is allowed by environment (Carrying capacity). A analysis of this formula shows also that forest has certain selfregulating capability that can maintain stabe when total cutting intensity(D)is lower than λ. On the contrary, when D λ, forest has lost its self-regulating capability, so that the biomass of stand becomes less and finally, the system would be destroied.

Wood plastic composites (WPC) made from Chinese white poplar (Populus tomentosa) and Canacian poplar (Populus canadensis) were studied. 1. Styrene containing a small amount of cis-polybutadiene, divinyl benzene, benzoyl peroxide, tert-butyl perbenzoate and hydroquinone was used as an impregnating liquid for preparing WPC. This impregnating liquid with rather long pot life could be polymerized in higher conversion. The properties of hardness, abrasive resistance, impact strength, static bending strength and dimensional stability of WPC prepared with this impregnating liquid were improved significantly, and increased with inereasing the polymer content in WPC. 2. The temperatures at centers of wood samples against polymeriztion temperatures, amount of initiators, dimensions of wood samples, antioxidants, U. V. stabilizer and time of polymerization were determined. From these, some better control of this kind of polymerization was proposed. 3. The influence on the properties of WPC prepared by the addition of an oil soluble surfactant——ОП—10, or a surface treating agent——toluene diisocyanate in this impregnating liquid was studied. It was found by scanning electron microscope, that the polymer was better distributed in WPC prepared by the impregnating liquid containing a small amount of ОП—10 than that without it, but the bonding properties between polymer and wood cells were still not tight enough.

This article deals with karyotype of Cunninghamia laceolata. The C. laceolata possesses Ⅱ pairs of chromosomes showing apparent differences. All of them are isoarms. Its 1-Ⅳ and Ⅵ pairs are metacentrics, while Ⅴ and Ⅶ-Ⅺ pairs are intercalary types, which are between metacentries and submetacentries. The C. lanceolata collected from Hunan province is found to contain supernumerary (B-) chromosomes, while no B-chromosome is existed in the C. lanceolata collected from Fujian province. The discovery is very interesting, for the existence of B—chromosomes could be used to trace the different origins of C. lanceolata.

This insect occurs throughout the regions where the hosts grow in Shensi Province, but outbreaks only occurs in certain parts of them. Young trees of Pinus tabulaeformis, P. armandi and P. massonixna are severly attacked. There is one generation per year in Shensi Province. Winter is spent as full-grown larvae in silken cocoons in the litter or below the surface of soil. Many soecies of natural enemies have been collected, of which 10 belong to bracoidae, ichneumonidae and trichogrammatidae. The parasitism of larvae and pupae is about 40 per cent. The results of experiments showed that fenitrothion, monocrotophos and parathion were very effective for the control of the larvae. The appication of ultra-low-volume technique in the control of this pest is recomerded.

It was observed anatomically that, abieninic resin ducts are distributed mainly in the cortex of bark and the needles. Those in the cortex connect to each other to form networks the resin inside could be collected by tapping. According to the openion of the authors resin ducts in the cortex are formed due to the enlargement of intercellular space amongst parenchymatous cells and disorganization of the gigantic parenchymatous cells. The external factors influencing resin formation are also investigated.

Tissue cultare experiments were carried out with Populus hopeiensos, P. tomentosa and P. alba, all of sect Leuce Duby. Plantlets were induced from isolated branch tissue of trees about 20-year old. Number of adventitious buds would be increased if the tissue was excised on media consisted of 1/2MS macroelements and full MS microelements supplemented with BAP 0.3mg/1+NAA 0.05mg/1+sugar 2.5%or those supplemented with BAP 0.3mg/1+sugar 2%. The best medium tested for rooting is that of 1/2MS macroelements and full MS microelements, supplemented with NAA 0.02mg/1+sugar 1.5%. Plantlets of these three species were transplanted in the nursery, and grew to a height of about 120cm.

Studying the productivity of Chinese fir, We surveyed four hundred and eight thouand mu of Chinese fir plantations from twenty four tree-farms covering mountaineus areas, hills and lowhills throughout the province in 1978. At the same time, 556 sample areas and stem analysis of 560 sample tree were studied. It was found that the Volume-growth is different among mountainous areas, hills and lowlills. They are high, moderate and low respectively. Besed on this study, It is considered that mountainous areas is the best one for the estabilishment of Chinese fir.

The zygaenid, Artona funeralis Bulter, is an important pest of the bamboo. It has four to five generations per year in Guangzhou, Guangdong Province, and hibernates in the form of matured larva within its coccoon. The first generation appears from February to June, the second from May to July, the third from July to September, the fourth from August to October or to April next year and the fifth from October to April next year. In general, the larva has six instars but the larva of fifth generation has seven instars. A field survey showed that it has seventeen natural enemies including parasites and predators. The effective control measures for this pest are: spraying with dipterex, dichlorvos, malathion, fenitrothion, carbaryl, pyrethrins, evisect, dimehypo, pyridaphenthion, dimilin or TH6038; and also by early destroying infested leaves.

It is well known that Eucommia ulmoides Oliv. is an endemic tree species of China. According to historical data, it has been two thousand years since the bark of eucommia was used by man. In this paper, we shall deal with the forms, distribution and introduction of Eucommia ulmoides. According to forms of the bark, Eucommia ulrnoides may be classified as the form of coarse bark and that of lubricious bark, the former looks like oak bark (See fig. 1) and the latter like chinese aspen bark (See fig. 2). Eucommia ulmoides is widely distributed in china, they are distributed in latitude 25—35 N, in longitude 104—119 E. The vertical distribution of Eucommia ulmoides, in general, is located at about the altitude of 300—1,300 meters. In this region of climatic optimum there are several tree species frequently met with. they are aleurites fordii, Toxicodendron vniciflua, Quercus variatilis, Quercus acutissima, Trachycarpus fortunel, Cupressusfunebris, Sapiun seliferum, Firmixna simplex, Juglans regix, Taxus chinensis, Cunnighamia lanceolata, Pinus massonixna, Liquidanbar formosana, Castanea mollissima, as well as Sophora Japonica. At home, Eucommia ulmoides was introduced into many places on a large scale in the fifties. At present the introduction of Eucommia ulmoides has obtained success in many places. In the light of Beijings introduction, it has removed 5 degrees in latitude about from the south to the north. that is just the region we called the southern temperate zone. The mainly indicator of temperature in this zone are: the temperature of plant growing (≥10℃) is 3,100°-3,400℃ to 4,250°-4,500℃, the absolute minimum temperate is-30°-0℃.