The changes in endogenous ABA, IAA and zeatin levels of control,NAA-treated and NAA+BA-treated cuttings(bud,bark) of Populus alba,P.tomentosa and P.davidiana during rooting process were investigated by using HPLC and GC.The experiments showed that the rooting ability of hardwood cuttings was determined by both presence of latent root primodia and balance of endogenous hormones bark.The high IAA/ABA ratio and zeatin content in bark of P. alba allowed the latent root primodia to resume their growth, and the cuttings could root and survive spontaneously.For P.tomentosa, because of its low IAA/BA ratio and zeatin content,approprite amount of exogenously applied NAA and BA was needed for stimulating latent root primodia to grow.P.davidiana had no ability to form bark-or-ignated adventitious roots, although treated with NAA and BA, the cuttings needed longer time to developl callus-originated adventitious roots. Finally, the action mode of exogenous NAA and BA in rooting process of cuttings was discussed.

Suppressed axillary buds and persisting meristems,which show the regeneration ability were investigated in the axile of seedlings and sprouts of Chinese fir(Cunninghamia lanceolata(Lamb.)Hook). But adventitious buds were not observed in the same material.The suppressed axillary buds can develop into secondary dormant buds with the secondary growth of the main stems.Sprouts may arise from secondary dormant buds or suppressed axillary buds directly, and may also originate from persisting detached meristems by forming additional buds.Such axillary structures have profound significance to sprout regeneration of this coniferous species.

The Chinese fir silvicultural system(SS)is a comprehensive system of cultivating pattern and component culture technics SS can not only be used to organize and manage Chinese fir cultivating, but can also be used as an important means of combining utilization of soil fertility with presevation of fertility. Essentially,it is a regulation and control system for Chinese fir ecosystem.The basic aim of SS is to make sustained use of the forest land and make a continueously fast-growing and high-yield stand which must follow certain order to set up SS. The main problems of SS in practice suggestions for the improvement and further development of SS for Chinese fir are also put forward by the author.

In this paper, collection time,processing method,techniques soaking and hastening germination of walnut seed were studied. Physiological analyses of seed were made to verify the causes of walnut seed rotting and its germination conditions.The result shows that early collection and long time piling of seeds with green skin always cause seed rotting, but insufficient water absorbed by sceds is the main reason for seed rotting during stratification or after seeding.It has been established that mechanical restrain of the walnut shell is the principal cause making seeds germinating slowly, and that high environmental temperature and sufficient water content in seed are suitable conditions for germination of walnut seeds. Such measures as late collection,rational processing,soaking in water before stratification,sunning the seeds to shell crack before sowing,raising the soil temperature after seeding, can be taken to decrease seed rotting,accelerate the speed of seed germination and increase the rate of seedlings emergence.

Aiming at the feasibility of conducting plantation on the site of renewed land by powder of coal(the coalpits filled with the fine coal ash from electri factory, then covered with soil layer of 30cm)and the selection of appropriate tree species, investigation on the distribution and growth characteristics of root-system of 4-5-yearold plantations of P.Xeuramericana, Salix matsudana,Ulmus pumila and Robinia pseudoacacia were carried out. The results are as follows:1. Root-system of all the 4 tree species can grow normally and the distribution depth can reach over 180cm in the soil, of which the weight and length of the root in the ash amount to 68% and 87% of the total,and those in the 30cm soil layer, 32% and 13%,respectively; and me horizontal root range around 8m.2.The total root length and weight of the poplar,willow,elm and locust are:49.29,29.45,25.42 and 68.08 km/plant,and 7.45,7.54,10.05 and 13.37kg/plant respectively.

By means of stem tip culture after temperature treatment, the MLO-free plantings were obtained from witches'broom diseased Paulownia tissue culture.1cm long stem segments with two sidebuds were cultured in MS medium,and incubated in the growth chambers at different temperatures.Tee results showed that all the stem segments died in 24-48 hours at 45℃,and within 3 Weeks at 40℃.On the otherhand, the new shoots sprouted from the stem segments, but these still showed typical witches' broom symptoms at 30℃ for 5 weeks. When the stem segments infected with MLO were cultured at 35℃,the apparently healthy shoots sprouted and retained their form more than 178 days.Fluorescence Microscopy revealed that the MLO fluorescence could not be detected in tile sieve tubes of the newly sprouted shoots within 35-40℃ treatments and the intensity of fluorescence in the original stem segments was reduced gradually from 1 to 4 weeks.The stem tips(0.5cm long)were taken as explants from these treated tissue culture at 35℃ for 29,33,55 and 80 days,and then transformed into MS or modified MS medium again.Apparently healthy roots and shoots developed from all these explants at 25℃.The detection with fluorescence microscopy and electron microscopy showed that all such plants had been free from MLO.

In this paper,the population dynamics of Dendrolimus spectabilis was studied in east Yanshan mountainl reasons for death and mortality variability in each stage were analysed;the key-stage and key-factor which effect the mortality of generation were discovered.The models to simulate population dynamics within the generation were developed.

The present paper deals with the residue dynamics of carbendazim in spruce seedling and soil using ¹⁴C-carbendazim to control thesnow blights and molds of spruce under simulated early winter and snow covered conditions.The rate of ¹⁴C-carbendazim used was 2g/m².The results showed that almost all the ¹⁴C-carbendazim was absorbed on the surface of the needles and that the degradation was so slowly that 22.78μg/g residue was still on the needle surface after 150 days(just as late snow-melting period).89%¹⁴C-carbendazim gathered in the surface soil of 0-6cm depth.The residue on the needle surface greatly oversteps the EC₍₅₀₎(5.2μg/g).The results proved the controlling effects of carbendazim,forinstance,Thiophanate methy 1,and Thiadimefon in the field tests.

In order to find the best way of managing shelterbelts,5 poplar tree species were selected from shelterbelts for studying fiber length.Based on the relationships between the fiber length and tree species,fiber length and site conditions,and fiber length and ages,the following results were obtained:the fiber length is determined mainly by species and age,and it is not significantly related to special site conditions of shelterbelts.Based on the distribution of fiber length, and the relationship between fiber length and age,a series of models about fiber length-age were established, and the relatively stable ages of fiber length were also obtained,the height of tree at the relatively stable ages can be considered as Hi(L=n^*Hi)during designing shelterbelts.The above results can provide feasible evidence for shelterbelt management.

The relationship between wood density and cutting resistance of 15 Chinese hardwoods was studied following the corresponding studies on 11 coniferous woods. The main discovery made during the latter and further confirmed herein is that the change of the relation between wood density and cutting resistance affected by chip thickness,knife rake angle, and wood moisture content exhibited a common tendency, no matter which one of the three factors changes.the higher the resultant level of cutting resistance,the larger the regression coefficient and the remained standard deviation of the densitycutting resistance correlation. The regression equations describing this tendency for hardwoods are presented. Furtheremore, the factors affecting the scatter of the density-cutting resistance relation were investigated and discussed.A more detailed general report in English is available from the author.

Spiral thickenings in the yessels elements of 51 species belonging to 44 genera and 20 families chinese hardwoods were investigated by SEM and TEM.They were found in the vascular or vasicentric.Four types or spiral thickening were proposed,namely,brached,nonbrached,swirled and vestured;their forms,functions,distributions and origins were described in detail.Occurrence or non-occurrence and distribution of the spiral thickenings must be considered as a useful identification of hardwood.

Host plants provide lac insects with food and habitats,therefore constituting the material base of lac production.Approximately 300 species of lac hosts have been found in China through our years'researches and investigations, among which 13 favourable species have been sorted out.These 13 species are of wide adaptablity and can produce more and higher-quality lac than others.Quite a few achievements have been obtained in our study of physiology,ecology,biology,breeding and lac plantation establishing techniques of these excellent plants.What we have done has greatly promoted lac production and helped to realize intensive management in lac production and to secure high and stable lac yield.

Using the AVHRR data from NOAA satellite,the green index and temperature field both before and after the forest fire in 1987 in the area were calculated. The results show that the vegetation has been renewed,and the green cover area become large fast.The forest fire has not made notable influence on temperature field.

This test was carried out with three-years-old precocious walnut seedlings(Juglans regia)cultivated in soil pots.The water contents of pot soil were weighed to 100%,75%, 50%, 30% of Field Capacity (FC) respectively from two to six weeks after the pistillate flower bloom (the sib of May).After this period, the seedlings were watered nomally till fruit ripeness. The results showed that:leaf,shoot and nut growth were all best in 75% FC treatment.Water stress(50%FC,30%FC)and waterlogging(100%FC)reduced the leaf water potential and net photosythesis rate and obviously inhibited the growth of leaf,shoot and nut.This inhibition was not made up by watering or draining after this period.The leaf structure was mainly influenced by water stress.Drought resistance of walnuts was also discussed in this paper.

In order to test the drought tolerant ability,the six poplar clones were treated with PEG(mW 6000)solution at three osmotic potential levels(-0.4 MPa, -1.0MPa,-1.6MPa),and their net photosyathesis rates(Pn)were siudied in growth culture chamber. The results show that under -1.6MPa stress Popelys simonii,P.poplaris 36 and 44 kept more photosynthesis product accumulation until the second day, however,that of P.nigra,P.euramericane 25/86 and 28/86 decreased to consumption level since the first day.And also there was the same trend in Pn decline under -1.0 MPa stress.According to this significant difference in Pn of different clones under medium and severe water stress,the concept of water potential conpensation point of net photosynthesis rate(Pn=0)is determined as a indicator evaluating drought tolerance.Thus, the six poplar clones can be divided into two types:The former group in which the water potnetial compensation point appears later,has a higherability to drought tolerance,and the latter group has a lower drought tolerance since the Water potential compensation point appears earlier.This will be significantly important for early identificantion and selection of genetic variation in drought tolerance for poplar clones.

According to characters of the relation between the population dynamics of Dendrolimus punctatus and the related environment and Nicholson-Bailey Model,this paper recommends a timedelay structure and stable control item,and establishes a simulation model of Dendrolimus punctatus population dynamics with difference equation methods.Based on the model,the mechanism of the population dynamics is discussed. Following results are obtained:the stronger the ability for the pest control by forest itself,the lower the equilibrium position of the population is and the better the stability is;the larger the inner growth rate of the population,the higher the equilibrium position is and the worse the stability is.

The axial tensile strength of rattan canes belonging to four species were reported.Bark and core of Calamus simplicifolius were found to be the strongest among these four species indicating it has a relatively good technological quality. Daemonorops margaritae has comparatively strong bark and a weak core.Being too slender the cane of C.tetradactylus was very difficult to separate its bark and core,and the cane as a whole is slightly stronger than that of C.dioicus in axial tensile strength.Additionally,there is an evidence indicating canes of wild growing rattan might be stronger than those of the cultivated ones.