The starch variation of normal and abnormal embryo systems during the embryonic selection in Cunninghamia lanceolata is carried out in the normal seeds, starch grains are always present in the active growth areas and their adjacent cells. There are two cases in the formation of the abnormal seeds:1. The abortion of the embryos. No starch grains exist in the embryos and suspensor cells. In the female gametophytes, starch grains are present or absent. 2. The abortion of the female gametophytes. At the beginning the embryo systems are well-developed and the distribution of starch frains is the same as that of the normal embryos-a layer of starch grains are accumulated in the cells of the female gametophyte around the embryos and the outer cells crinkle towards the centre while the crinkled areas enlarge starch grains diminish. At last, the female gametophytes die and embryos systems degenerate.The former case could be the result of the inbreeding depressions, the latter case maybe the reason that causes the formation of the aborted seeds.

The dynamic changes of soil fertility of different ground clearances are studied through the fixed position observation of twelve run-off plots for six years. The results show that the great differences between the soil fertility of control burning and that of non-burning are resulted by the different ground clearances. The soil fertility was increased by control burning shortly and decreased rapidly because of the erosion till the stand closed. According to the dymamic changes of soil fertility in control burning site, three soil fertility periods are designiated. Control burning periodically in same land is main factor that causes soil degradation of Chinese fir timber plantation. Where as the nutrient were enriched in surface layer of non-burning land and soil fertility was improved due to the decomposition of site slash.The changes of soil fertility of non-burning land in six years also can be devided into three periods but quite different from that of the control burning.

The allelopathy in the mixture of Chinese Pine (Pinus tabulaeformis)and Liaotung Oak (Quercus liaotungensis) is studied. The results show that:The leachates of litter, half decaying litter and surface layer soil under Pineoak mixture and each pure stand have significant effect on seed germination, seedling radicle and stem growth of Chinese Pine and other plants.Generally, the leachates of higher concentration show significant inhibitory effect and those of lower ones show stimulate effect or no effect. In laberatory, pine seed germination, seedling radicle and stem growth treated by oak litter leachate(1:10)were showed to be reduced by 40.4%, 25.5% and 12.8 %.The inhibitory effect of litter in mixture (1:10) is lower than those of two pure stands. Studies indicate that mixed planting of Pine and Oak can lead to accumulating heavily of allelopathic chemicals in the stand in some conditions(such as drought, no proper mixture proportion and pattern). This can cause poor growth of Chinese Pine and forest production reduced. The phenomenon of nature Pine-Oak mixed stands is explained and Scientific basis for planting Pine-Oak mixture is provided.

Combined chromosome doubling with interspecific crossing and pollen, seeds radiation, a number of artificial allotriploids of Populus tomentosa were bred firstly in the Institute of Populus tomentosa of Beijing Forestry University, China. The best one of allotriploids (clone B301) shows great increment of wood volume in 3m×3m spacing for 8 years old stands. Wood production of B301 obtains 399m³/hm² approximiatly 50 m³/hm² per year, as high as 3 times of the control, shows growth rapidly. But among the different clones of allotriploids their rates of growth are different, it shows the selection is a very important tool necessary not only for using in diploid tree population but also in triploid stands. The new achievements indicate that so far China has had already her own triploids of white poplars and used them in wood production.

The effect of the same crop, the first crop and the second crop of poplar forest, and the poplar mixed forest with Robinia pseudoacacia L., Hippophae rhamnoides L. and Amorpha fruticosa L. on the soil nutrients, the soil micorbes and the activities of soil enzyme were studied with the data from 48 sample plots in Shandong Province, Liaoning Province, Henan Province, Hebei Province and Beijing. The results showed that (1) the soil nutrients of the same crop forests tended to be reducing with the growth of the forest in the same condition of the site. (2) the soil nutrients and the growth of the second crop forest were evidently reduced compared with those of the first crop forest. (3) the poplar mixed forest could increase the soil fertility, which was an effective way to provent soil degadation.

The eucleid Phlossa jianningana Yang et Jiang is the most important insect pest of Chinese fir tree in South China, infesting leaves only, its injury being severe to the growth of the young trees in recent years. The paper deals with its bionomics and the control measures conducted during 1989-1991 in Fujian Province. Laboratory rearing and field observation showed that this insect has one generation each year in Jianning County, Fujian Province. There are seven larval instars. Overwintering takes place as mature larva (prepupa) within its own cocoon under shallow soil. Overwintering prepupas begin to pupate in early May of the following year. Adults begin to appear in late May, but most of which emerge in mid-June. The eggs are laid in mass on the underside of leaves. The peak period of the fourth instar larvae emerge in mid-August and they begin to cocoon, at maturity, reaching peak in early-September. The two periods are the best period for chemical control. The control methods of the pest are as follows:1.Spraying with 50% Phoxim EC 1000-1500 ×or Beauveria Bassiana Powder to eliminate mature larvae before cocooning into soil.2.Before the fourth instars larvae population reach maximum, it is very effective to spray with Dipterex, Methamidophos, Omethoate, Decamethrin & C.3.Cleaning of fields in early winter to eliminate the overwintering cocoons.4. Establishing mixed stand of Chinese fir, to reduce the infestation obviously.

In 1989-1993, systematic observations on 1st-3rd generation of Ancylis sativa Liu were carried out in Taigu County, Shanxi Province. Based on those investigatory data, 15 natural population life table, one average life table of 1st-3rd generations in five years were developed. The results showed as follows:1. The eggs and 1st-2nd instar larvae of 1st generation are a weak link of the life history and the generation; 2. The trend index of population of 1st-2nd, 2nd-3rd and 3rd to next 1st generations were 2.45, 2.7 and 0.21, the populations in the life history were from going up to balance; 3. The major controlling factors to the population were the death of 1st generation by rain and wind, of the 4th-5th instar larvae and pupae of 2nd generation parasitized by insects and of 3rd generation by picking fruit, natural enemies and dying out of winter; 4. The key factors were the predation of natural enemies to the 4th-5th instar larvae 1st generation, the pupae of 2nd generation parasitized by insects and the 4th-5th instar larvae of 3nd generation parasitized by funguses and the pupae of 3rd generation dying out in winter; 5. A new method suggested by the authors was what the key factor analysed by using the grey sequence degree.

Selected trees from healthy and different acid rain and air pollution damaged class (Pinus massoniana) forest were analysed for their water, basic density, chemic composition and element content as well as for their content of soluble sugars and starch to evaluate the possible impact on their wood properties. They were performed year ring-wise. The sapwood and heartwood portion of damaged trees showed a lower water content than that of healthy trees, in addition the sapwood and heartwood portion of serious damaged trees were about 30% and 20% less, but the basic density between different damaged class trees did not significantly differ. The chemical composition of different damaged class trees showed significant difference; the lignin and extractive content in damaged trees was higher than that in healthy trees; however, the α-cellulose content was about 1% to 3% less. The content of glucose in trees growing serious damaged forest were lower about 2% than that in healthy foreast ones. The content of sodium, calcium, magnesium, aluminium, iron, titanium and zinc differed between healthy and damaged trees of the same site; especially, the content of aluminium and iron was about one time and zinc was about three times higher than that in healthy trees. The content of soluble sugars and starch in damaged trees was lower than that in healthy trees. Those results indicate that there are lot of difference between the wood chemical properties of the trees from acid rain and air pollution damaged forest and healthy forest.

The factors significantly affacting the physical-strength properties of the composite are studied by using the quadratic orthogonal roatable combined design scheme. A couple of optimum regression models fiting for various thickness are obtained. According to the theories of wood-panel prosessing and structural machanicals of composite material, analysing the interaction among the critical factors and the strength properties, a combine devalution function about the important indexes is set up. Under the control of the cost bodage, using the princial and methed of optimality, a group of optimum structural-technological parameters adapted for actual production are found. The test results demonstrat that the thickness and the density of the composite and the bamboo sheet thickness critically affact the product strength properties, the adhesive level of the particle take a bigger role, and the hot pressing time have the smallest effect. The interaction among the factors, MOR or MOE is indicated with a group of quadratic surfaces. MOR = 119.4+13.83x₁ + 10.61x₂ - 8.22x₃- 22.86x₅ + 10.01x₁x₃ + 7.29x₁x₅-5.99x₁²-4.39x₂²+7.22x₃². MOE = 10090 + 373.7x₁ + 555x₂ -13778x₅ + 263.3x₁x₂ + 372.2x₁x₃-316.7x₂²

Study on population genetic diversity, population genetic structure and population differentiation has become the main part of population genetics and the important content of species diversity along with establishment and improvement of molecular biological technique, electrophoresis, isozyme staining, RFLP, and so on. Simultaneously, breeders have also paid more and more attention to these. So it becomes one of the most important realms. In this paper, the models and methods are briefly introduced and discussed.Some new explanations about the distributions of genetic variations in populations are given.

The systematic underestimation error of forest timber by using standard sample trees was pointed out. And 2 correction methods were proposed with easy estimation of the correction factors from the sampling data. The traditional formula is In contrast. the corrected formula is where V_TE and are V_TE¹ the estimated timber volume for whole quadrat using the original formula and the corrected formula respectively. V_BK and A_BK are respectively the measured timber volume and breast height cross-sectional area of K'th standard sample tree. A_T is the total breast height cross-sectional area in the quadrat; h_B and d_B are respectively the height and breast diameter of the tree with average breast height cross-sectional area; d_w is the average breast height diameter weighted by breast height cross-sectional area; an db is the slope of the tree height curve at d=d_B, d_B, h_B and d_w can be es timated by sampling in the quadrat. b can be obtained either from given tree height curve or by applying linear regression to the same sample data for estimation of d_B, h_B and d_w. The second correction of tEe formula has exactly the same form as the above equation, except the n standard sample trees are selected to have breast height diameters closest to the average breast height diameter in the quadrat. Thus d_B and h_B should be replaced by statistically estimated average breast height diameter and average tree height in the quadrat.

Yellows disease of betel nut palm Areca cathecu was observed in a commercially operated herbal farm in Danzhou County, Hainan Province in 1981.Since then this disease has affected over 90% of betel nut palms in this farm and is found in other betel nut growing areas in the island. Symptoms of the infected palms include the overall leaf yellowing, water soaking marks on leaflets, reduced spear leaf size, proliferation of auxiliary buds, recrosis of inflorescence and premature nut falls. The death of infected palms occurred one year after symptom expression. Electron microscopic examinations revealed that bacteria-like organism (BLO) was found in thin sections of vascular bundles and parenchyma cells of the infected tissue. The BLOs were measured at 460-780nm×360-570nm with 30-40nm thickness of cell walls. In addition, the mycoplasma-like organism (MLO)was found in sieve cells of phloem tissue.The sizes of MLOs ranged from 380 to 560nm. The thickness of unit membrane was measured at 10nm. No BLOs and/or MLOs were found in thin sections of healthy tissue.

The relationships between the differentiation ratio of the third generation of the pine caterpillar Dendrolimus punctatus Walker and the environment, climate, population density and the development of the larvae were studied in this paper. The population density and peak day of hatching were proved to be the key factors influencing the ratio of the third generation. The ratio of the third generation in stands with high population density or early peak day of hatching will be higher than that with low density or late peak day of hatching. It will be significantly low when the needle loss exceeds 70% of the needles in a tree. There is not significant relationships between the ratio of the third generation and the ground vegetation, forest canopy and sides of low slope sides(< 20°). The ratio of the third generation in a region is relatively stable in a given. Area in different years, while in different regions, it may change greatly according to the meteorological factors. A predication figure was established according to the peak hatching day of the second generation.

This paper briefly reports the prodUction and trial of manufacturing GradeⅠ plywood by using the mixed glue solution that is made from the Phenol-Formaldehyde Resin in which Larix ssp tanning extract is added as a modifier, and discusses the effects of the solution concentraction of the tanning extract, the amount of auxiliary, the molar ratio of PF, the condensation limit, the mixing ratio, the heat-pressing condition etc on the viscosity of glue solution, stability, gluing quality, in general ourline.The results showed that the quality of the produced Grade Ⅰ plywood fulfil the standard requirement and greatly lower the cost of the glue.