From ecological viewpoint, the most fragile drainage among the four basins in China (those are Zhujiang, Changjiang, the Yellow River and Heilongjiang) is Heilongjiang Basin of which the water resource is not abundant and the capacity of self-cleanning is low.The soil is thin; its structure is soft so as not to endure erosion.It has low capacity to restore the vegetation.Additionally, "paying more attention to utilization rather than to maintaining "has been taken in agriculture; " Paying more attention to getting rather than to giving"has been taken in for estry for a longtime.The resources are consumed extravagantly.The ecological environments evidently worsen.To check the situation above and carry out sustainable development of forestry, we have to change the basic concepts, to set up the nature viewpoint of human evolution together with the nature, to comfirm that forestry can produces not only economic products but special ecological and spiritual products as well of which the latter two can not enter markets for circulation so that a compensation system must be se up in the national economic system, to confirm the soil and water conservation functions of mountainous forests are the key in region planning, to keep that the minimum slope is 6 degree for safeguard the soil and water of mountainous area, and forcefully to develop ecological forestry of which the core is"low expense but high efficiency".

Effects of temperature and air relative humidity on net photosynthesis rate (P_n), light saturation point (LSP), light compcnsation point (LCP), apparent quantum yield (Φ), conductance of stomata (Cs) and transpiration were studied in controlled environments, using leaves of water-cultivated plants of four selected poplar clones:Populus simonii (Clone A), P.euromericana 28/86(Clone B), P.popularis 44(Clone C), and P.euromerlcana 25/86(Clone D).Results indicated that there was a variety of response patterns of LSP, LCP, Φ, Cs, maximum of P_n, and transpiration, to temperature and to RH among these four clones.This possibly reflects different ecotypic differences and provides evidence for early selection of poplar clones based on physiological characteristics.

A study on com parison of five methods for the transpiration water-comsum ption conducted in poplar plantation in Shandong province (Populus deltoides cv."Lux"ex.Ⅰ-69/55) and Ningxia Autonomous Region (Populus opera) from 1989 to 1991.The five measuring methods are whole-tree potometer, quick-weighing method, LI-1600 porometer, heat pulse technique and Penman-Monteith method.The results of the study are as follows:(1) Supposing that the relative value of daily transpiration waterconsumption per tree measured with whole-tree potometer is 100%, the relative value measured by quick-weighing method is 130%-140%, the relative value measured with LI-1600 porometer is 291% and the relative value measured by heat pulse technique is 90.14%.(2) Supposing that the relative value of the daily transpiration water-consum ption per tree measured by heat pulse technique is 100%, the relative value measured by quick-weighing method is 88% in 6-year-old tree and 112% in 2-year-old tree.(3) The value measured with LI-1600 porometer is 30%-90% higher than that measured by quick-weighing method in Ningxia arid zone and 140%-220% higher than that in more humid area of Shandong Province.(4) The value measured by Penman-Monteith method is very close to that measured with whole-tree potometer and that measured by heat pulse technique with errors less than 2%.

Starting from the concept of taper equation, the formulation of taper equation has been studied deeply, and considering the two problems existed currently in esta blishment of merchantable volume table, the general formula of optimal taperequation is presented in this paper.As an example, the special expression of optimal taper equation for Chinese fir in Hunan province is established furthermore.It is shown that the new model has advantages over all taper equations published before.

Genetic Algorithm is a new optimization and search algorithms, the paper sets forword Genetic Algorithm to determine the most effectual scheme under the restricted conditions of funds, variety and quantities of seedlings.The mathematical models and concrete methods are offered and discussed.The author have applied the programme design mentioned above to 97 subcompartments and have get the satisfactory result.

The endogeneous in hibitors in masson pine (Pinus massoniana Lamb) cuttings (MIn) from the ortets with different ages, from different provennanes, and by different reproductive modes were purified and separated by the methods of extraction and high pressure liqid chromatography (HPLC).The properties of the MIn were preliminary proofed by means of chemical detection and ultraviolet absorption spectra followed by biological assay with straight growth of wheat coleoptile section.It was found that there were 7 components in MIn in every kind of cuttings, which were flavones and phenols. Thesurvival percentage of each kind of cuttings negatively correlated with their MIn contents.The contents of MIn from different cuttings were compared by HPLC autointeg rator.The MIn content in cuttings from seedling ortets was higher than that from cutting ortets.MIn contents in the ortets from the southern subtropical provenance were lower than those from the northern subtropic provenances.The difference between provenances implied that the clone selective breeding of masson pine would be reliable and effective.The MIn contents increased with the age increasing of the ortets, which was one of the causes of cyclophysis in masson pine cuttings.Masson pine ortets could be rejuvenated by serial cuttage.Stopping the express of the MIn genes would be the successful way for increasing the cutting survival percentage.

This paper presents the preliminary study on nitrogen-fixing bacteria from the roots of Masson pine saplings. The results show that nitrogen-fixing bacteria can be isolated universally from the roots of masson pine saplings planted in six kinds of soils, but the effects of isolation among six kinds of soils were different. 142 strains of the nitrogen-fixing bacteria were obtained by two methods, of which one strain A'10 is identified as Alcaligenes paradoxus. Inoculation of seeds of masson pine with twenty-six strains were done, while inoculation of nine strains were successful. Nitrogenase activity of four strains, i. e. A'10, A'13, G1 & g2w, were measured, and the results are as following: A'10, 2. 10—3. 50 mgN/g glucose; A'13, 4. 20—5. 13 mgN/g glucose; G1, 3. 66—6. 83 mgN/g glucose; g2w, 1. 93—2. 60 mgN/g glucose.

The scale insect Quadraspidiotus perniciosus (comstock) is one of the important pests of jujube. In Shanxi Province, this insect has two generations a year and overwinters as 2nd instar nymph of the 2nd generation on the branch. The overwintering nymphs begin to harm the host in late March the following year. The nymphs of male and female have two instars. The adults of the second and the first generations emerge in early May and in mid-July, respectively. The sex ratios of the two generations are 1: 0. 26 and 1: 0. 35, respectively. The ralationship between the population density and natural death rate and the different parts and directions of the host plant are also investigated. Besides, the distribution of the nymphs on the jujube leaf, the effect of the branch age and the density of the pest on the fluctuation of the population, the forecasting to the occurance of the nymphs and adults, and the temperature and moisture on the development of the pest, and the methods of control are also studied.

The radial variation patterns of wood fibre length of 15 clones of Populus×euramercana were geneerally the same. But there existed a certain degree of interclonal and intraclonal variation. Average fibre length at various ages and the parameters related to variation patterns as well varied significantly among clones. This encourages the improvement of both the average level of fibre length and its variation patterns by selection and breeding. The radial variation patterns of fibre length of 15 clones were divided into three groups by classical analysis and expressed using the methematical model Y=C₁+ C₂×X₂+C₃exp (-C₄×X₁). There existed intersection betw een fibre length profiles of different clones, but the age- age correlation were significant, indicating that the early - selection among clones is feasible.

In order to design the reasonable vibrating im plements for harvesting fruits or nuts, the connection force of fruits and their stalk are measured, the experiments of stimulation and dislodging of fruits by vibration on the branches are carried out. The vibrating ex periment on the branches of living tree are done outdoors. At last, the most suitable stimulation frequency, acceleration of vibration, time of vibration were obtained by the analyses of data. The useful technological parameter is offered to the design of implements for shaking the branches of orchard trees todislodge fruits or nuts.

The mycorrhizal fungi resources on poplar are very rich. There are 30 species of ectomycorrhizal fungi and 5 species of VA mycorrhizal fungi with which it can form ectomycorrhizae and VA mycorrhizae. It is well known that morphological and anatomical characters of mycorrhizae are closely related with different fungi. Mycorrhizal fungi can enhance the seedling growth, increase water and nutrients absorption, strengthen drought resistance, induce PO (peroxidase), PPO (polyphenoloxidase) and PAL (phenylalanine ammonialyase) activities of poplar, promote synthesis of resistance materials, and enhance the canker-resistance of poplar.

The authors have used the Lagrange mechanics principle for analysing the traverse sta bility of log-truck-train, and established the four freedom of motion traverse vibration equation, and derived the equation according to the measure ddate. This method has important significance for researching the traverse stabitity of the log-truck-train and determining the structure type and size of the trailer.