Since 1987 to 1999,a study on the density management of Chinese fir plantations of 9-year-old was made continuously in the Experimental Center for Subtropical Forestry under the Chinese Academy of Forestry (CAF) located in Fenyi County, Jiangxi Province. Based on the establishment of 5 fixed sample plots in the stands with different retained density after thinning, the undergrowth vegetation had been observed for 13 years, the soil fertility in the stands had been tested for 9 years, the soil erosion as well as the amount of litters and their decomposition rates had been monitored for 8 years in the stands. The results showed that in all thinned stands with different thinning intensity, the undergrowth vegetation had developed very well, with the number of undergrowth plant species being increased to 30～36 species, the coverage of undergrowth vegetation being increased to 80%～90% , and the biomass of undergrowth vegetation being increased to 5t·hm^-2 in 13 years, while in the dense stand without thinning the undergrowth vegetation developed poorly and 8～9 years later to reaching the same level than that in the thinned stands. The reasonable stand density management could also increase the amount of micro organisms by 2.42 times in the soil, which resulted in faster decomposition of litters in the stands with lower density and well-developed undergrowth vegetation. Generally, when the Chinese fir plantation grows into the middle-aged,the content of organic mater starts decreasing more or less in the soil, particularly in the soil layer at depth of 16～30 cm underground , the content of available nitrogen and phosphorous decrease significantly. So, in the dense and fast growing stands, the higher the stand density is , the more the available nitrogen and phosphorous decrease significantly in the soil. Therefore, the reasonable decreasing of stand density by means of thinning can conserve the soil fertility, so that the long-term productivity of forest land can be maintained.

The effects of rotating plantation on the soil fertility of forest land and the stand growth were studied in Songxi County,Fujian Province.The results were as follows:Compared with the soil of continuous plantation,the microorganism quantities of soil in rotating plantation were increased,enzyme activities were strengthened,the contents of phenolic substance was decreased,acidity was reduced,base content was raised,base saturation degree and available nutrient contents were increased,and from these,stand growths were improved.The essence that the soil fertility in rotating plantation stand were improved and stand growth was increased lie in:Because the substitute species was different from the fore species,the microorganism species and quantities of soil of rotating plantation were increased and the enzyme activities were strengthened,and thereby,acidity was reduced,toxic compounds were decreased and available untrient contents were improved.

In order to find out the effects of root-root interactions on their production in the mixed stand,root growth and distribution studies were carried out both in the field and greenhouse.In the field studies,root density was studied on pure Fraxinus mandshurica,Larix gmelinii,and the zonal mixed plantations,all 10 years after planting,using a soil corer technique.Samples were taken along transects at the middle of plantation rows.Each sample was divided into three depth classes (0～10 cm,10～20 cm and 20～30 cm).In greenhouse,ash pure,larch pure and the mixed were planted both at pots and seedbed.4 seedlings were planted in one pot and 12 in one seedbed. The results from field experiments showed:horizontal distribution of root was different between ash and larch.Root density of ash was 3237.2g\5m^-3 and 3130.2g\5m^-3 between two species rows and between row 1 and 2 in the ash belt (including 3 rows,row 1 is on the side of other species),respectively.But the differences were not significant.However,root density of larch is only 939.4g\5m^-3 between two species rows,much lower than 2745.3g\5m^-3 between row 1 and 2 in the larch belt (including 5 rows).This result demonstrated that ash root had the tendency to invade to larch,and root distribution of larch was inhibited by ash.The vertical distribution of roots along the soil profile was more even in mixed plantations compared to pure plantations.Between two species rows,the proportion of root biomass within 0～10 cm, 10～20 cm and 20～30 cm depth soil layers was 41.9 %,28.7 % and 29.4 % of the total root biomass respectively, but 61.0 %,31.6% and 7.4 % in ash pure stand,55.6 %,27.9 % and 16.5 % in larch pure stand. Root density of ash is 3718.0g\5m^-3,higher than that of larch of which was 3040.7g\5m^-3. Greenhouse plantation results showed that the below-and above-ground biomass of ash was higher in mixed plantation than in pure planted both for potted or seedbed seedlings,particularly of that fine-root biomass (≤2 mm in diameter).Fine-root mass of potted and seedbed seedlings were increased about 28.8 % and 36.5 % respectively.In contrast,below-and above-ground biomass of larch was lower in mixed than in pure planted.Root/shoot ratio of ash was 0.78～0.81 for potted seedlings and 0.52～0.55 for seedbed seedlings,2 times higher than that of larch.The total root mass of ash was 4～6 times higher than that of larch. With relatively larger root mass and root/shoot ratio,ash is a superior competitor.Root system of ash developed rapidly and distributed widely,but slowly and straitly for larch under the condition of the mixed.It was this competition differences that had resulted in the significant increase of ash production in the mixed plantations.

In this paper, by means of the principles of LS estimation and ridge estimation, using the rule of residual mean squares(RMS_q), the main information that effect the estimation of forest canopy density is screened out from the RS and GIS information of the ground sample plots through computer simulation. Then, based on the analysis of possible limitation of LS estimation, the ridge estimation is put forward to establish the equation of canopy density estimation. The practical example indicates that when there are some multi-collinearities between the RS and GIS information that effect canopy density estimation, ridge estimation is prior to LS estimation.

The concentrations of chlorophyll, anthocyanin and flavonoid in Ginkgo biloba leaf were assayed in 1999. The results indicate that there are two peaks of flavonoid content, one on July 4 and the other that has greater value on Nov.1. Chlorophyll shows a declining trend after reaching its peak value on June 13. Anthocyanin shares a similar trend with flavonoid, but its curve fluctuates larger than that of flavonoid. With the help of Microsoft Excel to deal with data, there is a significantly positive relationship between flavonoid and anthocyanin, a significantly negative relationship between flavonoid and chlorophyll.The regression equation,Y(flavonoid)=220.9558-0.7722X′₁(chlorophyll)+0.4343X′₂(anthocyanin), is statistically significant at the 1% level. How to regulate the flavonoid concentration on the physiological and biochemical viewpoints is discussed.

Relationship between water status, endogenous hormone and sprout rate of 2 years old China seabuchthorn under water deficit was analyzed. The main results are: water deficit made water content, free water, water potential and endogenous GA_1/3 of seabuckthorn seedlings decreased, while endogenous ABA level increased obviously during dormancy stage in winter and sprout period in spring, so ratio of GA_1/3/ABA droped and came to threshold value later. As a result, the germination day delayed, especially that of seedlings under serious water deficit was postponed even for 25 days. Besides, seedlings grew slowly after sprout. Seabuckthorn suffered slight injure from a long time of medium soil water stress and sprout date was also delayed a few days and growth after sprout was restrained to a small extent.

Vertical slab polyacrylamide gel electrophoresis was used to examine inheritance of five isoenzymes in megagametophytes of Taxus Yunnanensis.Genetic diversity and genetic differentiation in three natural populations of Taxus Yunnanensis in Northwestern Yunnan were analyzed at ten loci coding for five enzyme systems.The percentage of loci polymorphism was 0.77.The average observed heterozygosity of all populations was 0.302,and the average expected heterozygosity was 0.320.The average number of alleles detected per locus was 2.05.The effective number of alleles per locus was 1.466.Measurement of gene diversity for ten loci showed that interpopulation genetic differentiation was 14.66%,and about 85% of the total gene diversity resided within population.The mean genetic distance was 0.118.

In this paper,based on overall analyses of effects of tending techniques on growth,population structure,species diversity of vegetation,biomass soil erosion and tending cost in young Chinese fir plantation,Multi-target decision of different tending techniques by means of grey situation decision theory was carried out.The results showed that block tending and overall tending were favourable to elevate survival rate and promote growth of young Chinese fir plantation.The structures of hiehgt and basal diameter of Chinese fir populations were certainly affected by tending techniques,especially basal diameter structure.The cost of overall tending was greatest,non-tending smallest,block tending medium.Block tending was favourable to form multi-layer stand structure and elevate species diversity of vegetation. The synthetical evaluation results showed that block tending was a better tending way for young Chinese fir plantation in southern forest region,it could not only decease competition between Chinese fir and vegetation,and keep up normal growth of Chinese fir,but decrease tending cost,and conserve soil fertility and species diversity as well.These have important practical significance for guiding tending of young Chinese fir plantation.

Nitrous oxide (N₂O) is one of the important kinds of greenhouse gases, and it mainly comes from soil ecosystem.The soil N₂O emission flux in the plantation of Acer truncatum and Pinus tabulaeformis woodland was measured in situ using static closed chamber technique at the year of 1997～1998 in Xishan area,Beijing,China.The annual N₂O emission flux ranges from -1.2 to 7.92 μg·m^-2h^-1 with mean of 3.16 μg·m^-2h^-1.It has seasonal variation as the highest flux in summer,the second in spring and autumn,and the lowest in winter.The N₂O emission flux is mainly determined by soil temperature,soil moisture and the precipitation within 5 days before the N₂O emission rate also has undulated diurnal variation that comes the lowest in 6'oclock and the peak in 9 and 18'oclock.

In this paper the relationships between the rooting of the cutting of the chimera of Chinese white poplar (Populus tomentosa Carr.)and the activities of peroxidase,indoleacetate oxidase and the contents of phenol,flavoid materials were analyzed.In the stages of cutting rooting of the chimera of Populus tomentosa,the activity of peroxidase increased after cutting and got to the first peak at the 5th day,and followed to decrease and got to minimum at the 7th day,the second peak appeared at the 17th day.The change curve found in normal Populus tomentosa was reverse to the chimera at first 7 days.The indoleacetate oxidase activity was contrary to peroxidase.The changes in contents of phenol and flavoid were accordant in the uptrend,and were similar to the activity of peroxidase,that of normal Chinese white poplar were reverse to the chimera.As a conclusion,the chimera rooting phase were related to the activities of peroxidase and indoleacetate oxidase as well as the contents of phenol and flavoid materials.Normal Chinese white poplar did not easily root because it could not satisfy the relative conditions.

triploids had been obtained by using different concentrations of colchicine solution and different methods for treating female flower buds of Populus tomentosa×P.bolleana,P.alba×P.glandulosa and P.abba×P.tomentosa.The results were as follows:①It was a moderate treating time for chromosome doubling of female gamete from female flower buds on the female flower branches which had been cultured in water for 1～5 days.This period of time was a sensitive phase of female gamete that was treated.② 3 methods of treating female flower buds with colchicine solution were effective.The better method was dipping female flower bud in the bottle of colchicine solution.③ The effective colchicine concentrations were 0.25 % and 0.50 %,the better one was 0.50 %.④The selected triploids had rapid growing,gigantic and vigorous properties at seedling period time.

The studies on the concentration of aero anion in some south China forest recreation areas showed: (1) The aero anion concentration has differences in different forest types. (2) In forest surroundings, the correlation between aero anion concentration with temperature and moisture are significant. (3) Water body has different effect on aero anion concentration in forest recreation areas. (4) There have been aero anion daily variance and yearly variance. (5) The structural material has effect on aero-anion concentration.

Trichoderma harzianum T88 and T.atroviride T95 in dual culture with Cytospora chrysosperma and Dothiorella gregaria were studied. Whether antagonists produced volatile antibiotic which inhibited the growth of pathogens and nonvolatile antibiotics which inhibited the dry weight of mycelium of pathogens were tested. Mycoparasitic activities of Trichoderma spp. were studied against two serious plant pathogens, Cytospora chrysosperma and Dothiorella gregaria by microscopy and scanning electron microscopy (SEM). Macroscopic observations of fungal growth in dual cultures revealed that T.harzianum T88 and T.atroviride T95 made hyphal contact with the pathogen within 3 days after inoculation, leading to the inhibition in pathogen growth. The volatile antibiotic which antagonists produced inhibited the growth of pathogen in varying degrees. The most inhibition rate reached 80.30% under the airtight condition. The non volatile antibiotics inhibited very strong the growth of pathogens. The dry weight of mycelium was evidently less than that of the control. The non volatile antibiotics were not-sensitive to the heating. The microscopy and SEM investigations showed that T.harzianum T88 and T. atroviride T95 appeared to inhibit pathogens by mycoparasitism, with evidence of either parallel and waved growth, or by penetrating hyphal cells of pathogens by forming hooks, haustoria and appressoria like structures which invariably led to hyphal cell cytoplasm concentration and disruption.

The resistance of seven jujube strains (species),5 of these,Zizyphus jujuba var. Dunzizao,Zizyphus jujuba var. Changhongzao,Zizyphus jujuba var.Mayazao,Zizyphus jujuba var. Hupingzao and Zizyphus jujuba var. Hamazao,selected from Chinese genebank of jujube in Shanxi Fruit Tree Research Institute,other two of these:Zizyphus jujuba var.Pozao and Zizyphus Spinosa selected from Tang County,Hebei province,to jujube witches-broom disease was determined by using the method of grafting diseased bark onto the seedlings from 1995～1999.The results are as follow:The percent of seedlings infected by the disease for Z.jujuba var.Dunzizao is 100%,Z.jujuba var. Mayazao is 78.57%, Z.jujuba var.Changhongzao is 66.67%, Z.jujuba var.Pozao is 100%, Zizyphus Spinosa is 80%,Z.jujuba Hamazao is 0% and Z.jujuba var. Hupingzao is 0%.This indicates that Z.jujuba var. Hupingzao and Z.jujuba var. Hamazao have high resistance to the jujube witches-broom disease.112 seedlings belonging to 45 individuals of Pozao jujube selected from the epidemic area of the disase in Taihang Mountain,Hebei province,were planted in experiment site in Tang County in 1995.From 1996～1997,by using the grafting method the phytoplasmas caused the disease were infected artificially twice.In the third time,the phytoplasmas were artificially infected by grafting some infected twigs onto the seedlings of jujube selected in April 1998.The results investigated in October 1999 showed that 6 seedlings belonging three individuals have not been infected by the disease.Though 3 of these belonging to 2 individuals grew some little diseased twigs in May and June 1998 just after grafting diseased twigs on them, these diseased twigs all died in next spring,and the seedling have grown well.

The effects of the color, shape, sticky surface area and height in the crown of the sex pheromone traps on capture of Cydia trasias (Meyrick) male moth were evaluated in Zhongguancun, Beijing, in 1999. The white, green and yellow traps were much more effective than blue one. Triangle traps were much more effective than double disc and boat shape traps. The triangle trap of 500.0cm² were much more effective than those of 250.0cm² and 166.7 cm². The triangle traps hung in upper-middle part of the crown were much more effective than those of in middle and lower-middle parts. Thus, white, triangle traps of 500.0cm² provided a reliable tool for monitoring and control in pheromone system of Cydia trasias, when hung in the upper-middle part of the crown.

The sex attractant for yellow tortrix, Acleris fimbriana Meyrick,(E)-11,13-tetradecadienal(E11,13-14:Ald),was synthesized via Wittig reaction from two readily available starting materials. Field trials were undertaken in Beijing during May-October, 2000. The tests showed that E11,13-14:Ald gave strong attractive activity to the male yellow tortrix . The optimum dose of E11,13-14:Ald to catch male yellow tortrix was 1.0mg. Single E11,13-14:Ac was not attractive to the male moths, but it could highly enhance the attractive effect when it was added to E11,13-14:Ald. On the other hand, E11,13-14:OH, E11-14:OH and E11-14:Ald inhibited the attractive effect when they were added to E11,13-14:Ald respectively.

The developments of the studies on chaotic dynamics are simply summarized in this paper.Further such thoughts as non-linear dynamics systems of forestry engineering,the studied objects and methods are discussed,and one simple model are considered. Finally the possible advancements of the studies on the application of chaotic dynamics in forestry engineering are mentioned.

The conventional weight analysis(CWA),i.e.,the percent weight loss of the wood specimens was used as an index to evaluate the wood degrading ability for 64 wood-rotting. fungi to degrade korean pine,Pinus koraiensis Sieb. et Zucc.,cathay poplar,Populus cathayana Rehd., Asian white birch,Betula platyphylla Suk.The percent weight loss and the color change of wood specimens were measured after 46 days of culture. The results showed that their wood degrading ability was significantly different.Nigrofomes castaneus (Imaz.)Teng. collected from the Chang Bai Mountain Forest Reserve in Northeastern China is the strongest brown-rot fungus to degrade wood in all the measured species,it caused 64.9%,52.2% and 16.9% weight loss of Asian white birth, cathay poplar and korean pine wood specimens respectively;Tyromyces albidus Donk.,Ganoderma lucidum Karst.,Polyporellus brumalis Fr.,Lenzites tricolor Fr.,Favolus alveolaris Quel.,Pycnoporus cinnabarinus Karst., Coriolus versicolor Quel. were some species of white-rot fungi with high and higher wood degrading ability.

To look for impact of trunk rot on growth and wood properties of poplar tree on beaches along Yangtzer River, the growth of poplar tree was investigated and some wood properties were determined. The value of green moisture content of internal part of rotted poplar tree is smaller than that of normal one. The values of basic density and ratio of drying shrinkage of rotted poplar tree are higher than that of normal one. The tension wood was detected in rotted poplar wood by scan electronic microscope. Fungi and bacteria attack the poplar trees through check of bark pocket . The mycelium spreads from vessels and ray cells to fiber cells in poplar wood.

The forests of Picea crassifolia in Qilian Mountains are typical mountain forests in arid and semi arid area of west China, its unique hydrological roles lay a foundation for the steady development of oasis ecological economic systems in the corridor. In this paper, the effects and functions of the forest on hydrological cycle and rainfall distribution were summarized through the long term fixed observing and studying . The results showed that the forests could reduce the amount and intensity of precipitation and evaporation inside forests by canopy interception, which could avoid the surface runoff, soil and water loss and keep the high air humidity and soil moisture content, provide shadow environment and enough water conditions for shade plants. The air humidity of forests area is larger than grasslands or bare lands at the same height because of the forest evaporation. In addition, forests change the regional air circulation, make material preparation for precipitation and take effect in increasing rainfalls of forest areas.

Genetic diversity and differentiation of four natural populations of Quercus mongolica in Northeast China were studied with the method of RAPD.Through the amplification with 48 random primers,344 repeatable loci were detected and 245 loci were polymorphic.Percentage of polymorphic loci was 71.22%.According to the measurement of Shannon index,genetic diversity of Quercus mongolica was on relative high level and genetic variation mainly distributed within population (64.50%).In the studied populations of Quercus mongolica,the level of genetic diversity of OLJ was the highest,that of OHH was the lowest, and that of OSZ and OHL were the middle.The average genetic distance within populations was 0.0962,that among populations was 0.1290.Abundant genetic diversity of Quercus mongolica assured the steady existence and development of its populations.

strains of Metarhizium were cultivated in submerged culture. The results indicated that the submerged conidia could be produced by means of microcyclic sporogenesis for some strains of Metarhizium,but perhaps, the occurrence of microcyclic sporogenesis depended on the nature of strains. Submerged sporulation of M337 strain was emphatically observed in the media containing different nutrient elements. The results showed that the submerged sporulation depended on a delicate equilibrium in the composition of the medium. Various carbon and nitrogen sources affected the production of submerged conidia greatly. Sucrose, soluble starch and lactose were effective for sporulation of submerged conidia. Peanut cake powder, yeast extract and peptone were ideal nitrogen sources for submerged sporulation. The influence of trace elements on submerged sporulation was most spectacular. Molybdenum was the most important element. Zinc was stimulatory. When all 6 elements (B,Cu,Fe,Mn,Mo,Zn) were added together, it yielded highest production of submerged conidia. Vitamins affected submerged sporulation significantly. VB₆+VH and compound vitamin B were more effective for producing submerged conidia. In addition, the infectivity of submerged conidia of M337 strain was tested in laboratory, which showed higher virulent to the 3rd～4th instar larvae of Dendrolimus punctatus. From experiment results, we can appreciate the fact of worth while making a thorough study on production of conidia of Metarhizium cultivated in submerse fermentation.

Soil and water conservation mechanism of vegetation has been explained through analysing the effects of vegetation at different layers on rainfall. The vegetation cause the result of reduction of runoff amount,runoff energy and runoff carrying sediment. and vegetation improving soil to make a great role of soil and water conservation because of vegetation increasing resistant soil erosion. The research point out soil and water conservation function of vegetation is due to using out runoff amount continually by vegetation at different layers, and the accumulation effects of vegetation at different layers lead quickly reduction of soil erosion amount as to realize bring function of vegetation soil and water conservation into full play.