ABA contents increased obviously during the early developmental stages of C.mollissima and C.henryi seeds. The ABA contents of the seeds reached the peak of 1935ng/g at 105 days (C.mollissima) and 1573ng/g at 100 days (C.henryi) after flowering, then decreased gradually in both species. Moreover, the sensitivity to ABA of seeds and their isolated embryos decreased during development. The germination of two kinds of seeds 100 days after flowering inhibited by 15^-5 mol/L ABA, and failed to completely inhibit even by 10^-2 mol/L ABA if the seeds harvested at full maturity. The effects of ABA in promoting the synthesis and accumulation of protein storage in embryos was at the transcriptional level, in the later process of mature.

Callus derived from completed embryos of Ginkgo biloba L. were light green and crisp. And after subculture, some callus changed from crispy to compact. In MS medium supplemented with 2mg/L BA and 0.5mg/L NAA, somatic embryos were obtained from the compact callus. Embryoids originated from embryonic cell at the edge of callus, and embryoids at whatever stage (globular or heart) exhibited a slow growth, which delayed transfer onto subculture medium.

This paper deals comparatively with the runoff-producing, soil-water content, water balance and trees growth of two spacing (9m×2m and 5m×2m) artificial Locust Forest between water-harvesting and conventional treatment. The results showed that afforestation by water-harvesting can increase runoff harvest in the planting strip, raise soil water content, permeate more rain-water into deep soil under the roots range and prevent critical deficit of soil water continuously for a long time——soil desiccation, which results in declination of trees growth. In these treatments, the lowest density (8m² tamped) is desirable for effect, it is that more than 35% annual runoff yield is stored in soil, deep soil water is replenished effectively and growth of forest tress is promoted.

Although the natural triploids, the giant forms of poplar in volume growth have been found in a few species of genus Populus in many countries in the world, the work of natural triploids of indigenous tree of poplar species in China has not been done until the national program of poplar breeding was established since 1983.The national program selection and breeding of triploids of Populus tomentosa has being conducted by group of professors in Beijing Forestry University for over 15 years (1983-1997). As the breeding strategy of triploids of Populus tomentosa, the Populus tremula and Populus tremuloides were firstly followed. Research started with natural triploid selection from stands, observation of larger 2n pollen, and the artificial induction of triploids of Populus tomentosa by colchicine treatment. So far the results of these three mentioned aspects were obtained. In this paper the observation of 2n pollen and selection of natural triploids of Populus tomentosa were summarized.By pollen observation and chromosome accounting of Populus tomentosa, the results indicate: (1)There are larger pollen grains in the natural spectrum of pollen of Populus tomentosa the diameter of larger pollen varies from 35~45μm, they cover 3.9% of total pollen with 38 chromosomes (1n=2x=38), which proves the larger pollen grains to be unreduced 2n pollen, and the smaller pollen wth 19 chromosomes (1n=1x=19), are normal haploid pollen; (2)The natural triploids (2n=3x=57) of Populus tomentosa are existed in the distribution area of P.tomentosa. So far 5 clones of natural triploids of Populus tomentosa have been found, which distribute in northern, western, and southern parts of its distribution area, and they separated very far each from other. It shows, the existence of natural triploids of Populus tomentosa has universality; (3)The volume growth, fiber length, stem pattern and resistance to pest of natural triploids of Populus tomentosa are much better than the productive colony. The average genetic gain for volume growth of 5 natural triploids exceed 56.4% over the control; the best clone among the natural triploids, the B383 exceed 154% over the control. The discovery the selection and utilization of these natural triploids of Populus tomentosa is very important for both pulp and timber production and also for academic research of forest tree breeding. Today a large scale of cultivation of these best natural triploids of Populus tomentosa has been spread up through the north part of China.

According to the work of national cooperative group of Chinese fir provenance test, we chose seven representative provenances from seven Chinese fir provenance zones. Seven provenance samples were randomly collected from Xinyang gene pool(Henan Province), total DNA was extracted and purified from leaves.In this paper, the optimum PCR reaction conditions for RAPD analysis were constructed and intensive RAPD analysis was conducted for above samples through more than 300 PCR reactions. The polymorphic DNA sequence analysis was conducted for seven provenances using twenty-three primers. The result showed that the proportion of polymorphic RAPD loci for seven provenances was 79.8%, the genetic distance for seven provenances ranged between 0.225 and 0.4407, averaging 0.322. Those results reveal high variation among seven provenances.The natural distribution of Chinese fir is important for provenance test and breeding, but it is difficult to deduce the natural distribution of Chinese fir, since the Chinese fir has covered complicated circumstance and has a long cultivation history. The dendrogram of seven provenances was constructed on the basis of genetic similarity, the tree showed the relationships among different provenances, Napo、Rongshui、Huitong and Jinping got together, Jianwo、Hongya、Shangcheng gathered respectively. The dendrogram shows the provenances from the western part of Nanlins mountains are more similar than other provenances, so we deduce the center-western part of Nanlings mountain is the central distribution zones of Chinese fir, this result is as same as the provenance test.

The requirements of cities for forest have being increased since the environment of cities being deteriorated as a result of industry development and citilization. It is the task of top priority to build a complete urban forest ecosystem, to differentiate urban forest range rationally, and to manage urban forest in a high economic benefit way. The forest type and the differentiation principle, which influence the differentiation of urban forest, the coordinating relationship between cities and forest areas, and the management strategics under the conditions of market economy were discussed in this paper.

The experimental forests and dementstration forests of five Larches including L.gmelini, L.olgensis, L.principis-rupprechtii, L.sibirica and L.kaempferi have been established in three different locations of the west of Heilongjiang Province. Through eighteen years observation and comparision, results have been obtained: L.principis-rupprechtii is not suitable for introduction and forestation due to its little growth. The timber production of L.olgensis is higher over 100% than L.gmelini and may become main planting tree species. L.kaempferi was for the first time introduced in the semiarid zone of N48°13′ with rainfall about 500 mm, and its growth in this area was better than in Liaoning and Shandong provinces. Average height of the tree is 12.9m, DBH is 14.5cm and the stand volume is higher above 100% and 50%~100% than L.gmelini and L.olgensis, respectively. As the native tree species, L.gmelini has adaptive capacity to resist the locate cold and drought, so it should be used for planting common timber and protection forests. It is necessary to comhine seletion of tree species with that of superior provenance for raising stability and productive capacity of the larch plantation. The authors suggest that it is better to use the seeds tamed under the China's continental climate in the introduction of L.kaempferi.

The fungus belonging to the genus Exobasidium (Basidiomycotina, Ustomycetes, Exobasidiales) is known as the pathogen of cell's hyperplastic and hypertrophic disease of several tree plants. In this study, thirty-five isolates (isolated from Japan) of twelve species and one variety of the genus were divided into eighteen groups based on the fuzzy analysis of cultural properties (shapes and characters of colonies; growth curve of the isolates under different temperatures, pHs, nitrogen sources and carbon sources) and the analysis of 28S rDNA-PCR-RFLP. Among the eighteen groups, nine groups were identical with the species identified by the traditional taxonomy. These species are E.vexans Mass、E.reticulatum Ito et Sawada、E.camelliae Shirai、E.cylindrosporium Ezuka、E.shiraianum P. Heen.、E.hachijoense Otani, Kakishima et Iijima、E.bisporum Sawada et Ezuka、E.pievidis-ovalifoliae Sawada and E.symploci-japonicae Kusano et Tokubuchi. Tested seven isolates of E.gracile (Shirai) Sydow were differentiated into four groups that showed the differentiation related to geographical environment and hosts in the species. Tested seven isolates of E.japonicum Shirai were differentiated into five groups that showed the differentiation related to hosts in the species. Tested isolates of E.yoshinagai P. Heen., E.otanianum Ezuka var. satsumense Zhang et Arai and the three isolates of tested seven isolates of E.japonicum were classified into one group.

Distribution patterns of the pine sawfly (Neodiprion xiangyunicus) were investigated in relation to site elevation and forest stand density. The pine sawfly was found to be restricted to pure stand of its host at specific elevations based on transect studies. Defoliation and oviposition on Yunnan pine(Pinus yunnanensis) by N.xiangyunicus was confined to a specific elevational band (1900~2100m) within the host range of the area(1650~2100m). Stand density did not appear to have a significant influence on N.xiangyunicus distribution pattern. The defoliation and oviposition by N.xiangyunicus were divided into different levels based on the site elevation. The toughness, length and width of pine needle in 1700m and 1950m sites, the needle dry weight, total nitrogen, tissues of needle, terpenes of needle oils in 1700m, 1950m and 2050m sites were researched. It was found that the toughness of needle in 1700m and 1900m sites, the thickness of epidermis, the diameter of resin ducts, the total nitrogen and the dry weight of needle in 1700m, 1950m and 2050m sites had a close relation to the defoliation and oviposition by N.xiangyunicus. The pine sawfly was distributed in the site with higher elavation lower needle toughness, smaller thickness of epidermis, lower nitrogen content and lower dry weight of needle.

The control trail of Acantholyda piceacola was carried out by using insectcides, such as, Dimilin, Cyhalothrin, Deltamethrin etc., and the integrated control method of the Acantholyda piceacola was advanced in this paper. The results show that the essential way to control the pest in a long term is to carry out the measures of closing the forest, improving stand environment, protecting their natural enemies. The integrated control method should be used in harmed area. The death rate of the 2d instar larvae was over 95% by using Diflubenzuron No.3 25% (100×~500×). In the hatching peak period, the mortality could exceed 96% by using low volume aerial spraying once with mixed emulsion of 25% Diflubenzuron No.3 (600g/hm²) and cyhalothrin (105g/hm²)

The relationship between softwood longitudinal permeability and its structure was systematically studied based upon the principles of flow. The results showed that the specific permeability coefficient (K) was proportional to the number of flow paths every unit area, the ratio of average tracheid length to the equivalent thickness of the pit membrane and the specific permeability coefficient of pit openings. The results had been tested and were in a good agreement with the data presented by Jiang(1993).

To satisfy of chain saw the trend needs to increase the speed of the saw chain pitch also tends to reducing. The chain sprocket design theory is applicable for more than 15mm(t≥15mm) chain pitch of chain saw and chain sprocket design in the domestic and overseas, but for less than 10 26mm(t≤10.26mm) chain pitch chain sprocket design the application of current chain sprocket design has some faults and limitation.This paper set up an improved theory for design and calculation in the saw chain sprocket.Using this chain sprocket design theory the utilization of energy can be improved vibration reduced, and the piece using time enlonged.

J-50 tractor is the machine widely used in wood production of forest zone. But, the operator's physical and psychological endurance and his working efficiency are much influenced by severe vibration of the machine, and the machinery service life is much influenced as well. Firstly this paper aims at the researching on the relative theories and experiments in vibration and evaluation of riding comfort for J-50 tractor in recent years. Then, some proposals are put forward concerning the further studies on vibration and evaluation of riding comfort for J-50 tractor:(1) study on vibration for the tractor can simplify the mechanics model of four freedoms system; (2)electronic computer can be used in the study on vibration damping for the tractor, mode parameters of whole tractor can be distingushed; (3)study on the main cause of vibration of the tractor engine, and take vibration damping measures to it, parameter of damper are chosen to make use of optimization design; (4) vibration damping measures can be made for drive room and seat to improve the work environmental suitable to forest region. Through some sorts of ways above, vibration of the tractor will be reduced greatly.

Microscopic examination shows that Robinia pseudoacacia seedlings inoculated with rhizobia produces a variety of root hair forms. Part of the root is much swollen with long and thick root hairs around until form of nodules. Observation of TEM on the ultrastructure of swollen root parts indicated that there is a large amount of wall ingrowths which are well developed on the extangential wall of common epidermal cells among hairy cells. It is verified that these epidermal cells with wall ingrowths are transfer cells induced by rhizobia on root epidermal cells of Robinia pseudoacacia.

In the stem-form curve formula of Pinus tabulaeformis y=[a₀x^a₁-a₂+a₃/(a₄-x)]^0.5, three conditions must be satisfied: (1)a₄ is given value beyond the range 0~H, H stands for the tree height; (2) -a₂=-a₃/a₄; (3) The value of expression within radical sign must be positive on any point of the tree stem. Fitting curve based on 129 P.tabulaeformis trees leads to the results: Sharing 89.9% at the condition of R²>0.98, the absolute value of systematic error < 3% coves 79.1%, and the absolute value of systematic error is less than 7% at the most. Comparing the tree stem valume derived form formula of stem-form curve of the one derived from sectional measurement by means of Smalin's formula, the absolute values of error are not more than 4%, where below 1% shares 76.7% of sample trees. The systematic error of 129 trees is 0.53%. The proposed formula of stem-form curve in this paper can reflect the stem-form profile of P.tabulaeformis very suitablely.

The crown area proportional coefficient of pure artificial even-aged stand means the ratio of the area of the stand to its crown. Standard density refers to the theoretical density of the pure artificial even-aged stand area when its crown density is 1.0. According to the method of studing the forest site classification and evoluation in Nanling mountainous region, when the arrangements of forest tree in a stand are the rectangle and isosceles triangle, the crown area proportional coefficient and range of its variation have been concluded in this paper, if canopy density is 1.0. And we calculate stand standard density (stem number) of two kinds of arrangements, which provides the scientific bases for precisely determing the standard density and quantitative intermediate cutting of a pure artificial even-aged stand.

Application of growth model forecasting method in epidemic forecasting of the poplar bacterial canker was discussed. The result of nonlinear regression analysis was that the Logistic growth model was superior by testing for appropriateness. The accuracy of the model was higher by predicting and examining with the data outside the model, so its practicability was verified. It also showed that this disease was a polycyclic disease, so that appropriate management tactics of disease control and forecasting should be taken.