Importance value-area curve is used as a criterion for Judging the minimal area of a community. It seems to be better and more significant than other ones.Importance value-area curve used as a sampling technique, is suitable for tropical rain forests and montane rain forests in Hainan, and subtropical evergreen-broadleaf forests and evergreen needle-leaf forests in Guangdong. It has been shown that importance value-area curve has higher precision and higher efficiency.This paper suggests the formulas:used for the importance value-area curve to determinine minimal area.

In the south of the Song-Nen plain there is a temperate semimoist continental climate. The zonal vegetation in this region is meadow steppe. The distribution and combination of plants appear to be controlled mainly by the edaphic condition.Using qualitative and quantitative analyses, the vegetation can be divided into 11 communities. Based on ordination and biotope analyses, the 11 communities may be grouped into 5 ecological combinations (1) The salt-alkali tolerant and hygrophilous combination, including the Sueada corniculata, the Sueada glauca and the Puccinellia tenuiflora communities; (2)The slightly salt-alkali tolerant and mesophilous combination, including the Leymus chinensis community; (3) The moist-eutrophilous combination, including the Calamagrostis-Leymus, the Leymus- Potentilla and the Leymus-Hemarthria communities; (4) The Stipa baicalensis community on drainage rich soil; (5) The ammophilous- xerophilous plant combination, including the Stipa grandis-Filifolium, the S. grandis and the Ulmus communities.As a example, a 2-dimensional ordination of 23 releves shows that the vegetation in the field is a mixture in varying proportions of continuity, and discontinuity In g-dimensional ordination, the communities may be plotted according to the axes related to the saline content and alkalization of soil as well as soil moisture gradients in ordination field. The positions on each axis and the distance values between communities can quantitatively reflect the difference and relationship between communities.

Observations were made of stomatal behaviour of groundnut growing in glasshouses. Stomatal resistance or its reciprocal, conductance, varies throughout a canopy: between different parts of a leaf, between upper and lower surfaces, between leaves and between plants. The response of stomatal behaviour to environmental factors was analysed. Fig. 4 shows an example of responses of conductance to environmental factors such as air temperature, irradiance and vapour pressure deficit. It is also seen that leaf conductance increases with soil moisture. Under full cover of plants and with wet soil, the following relation between canopy conductance and environmental variables has been found:

gc = 0.299 (IR/VPD) - 0.089, (r = 0.94)

where gc—canopy conductance (cm/s), IR—intercepted radiation (W/m2), VPD—vapour pressure deficit (mba), r—correlation coefficient.

The biomass structures of different stands of Phyllostachys heteroclada were studies by the allometric method based on 18808 bamboo culms, 47 rhizome quadrats and 38 samples of bamboo of different ages (1—6 yrs.) and diameter classes (0.5—3.0) from 39 sample plots. The biomass of culm, branch-leave and rhizomes in relation to diameter breast height fit out the regression equation by statistical procedures.The results obtained show that the total above ground biomass increases with the increase in diameter classes, and the distribution of the ratios of culm weight at different diameter classes to the total stand weight is as follows: 16% for 1.5 diameter classes, 30.5% for 2.0 classes, 26.1% for 2.5 classes and 16.0% for 3.0 classes, respectively. The total above ground biomass decreases with the increase of the age class and the distribution is 31.7% for age class Ⅰ, 22% for age class Ⅱ, 17.5% for age class Ⅲ, and 28% for age class Ⅳ or above.A. high-yield stand is defined as: vigorous rhizomes 50—60%; rhizome capacity 2.0—2.5‰, ratio of total above ground weight to total under ground weight 1.0—1.5; leaf area index 4—6; yield 4000—7000 jin per mu.

As a kind of renewable resource, vegetation, including both natural and cultural ones, has long been a subject studied earnestly by remote sensing application specialists. Vegetation classification is one of the significant aspects of vegetation research. The use of satellite image to classify vegetation has been studied by important scholars both at home and abroad. This paper chooses the vegetation of the waters and the sand bars in the Dongting Lake as the subject matter for study, and tries to study the method of vegetation classification with remote sensing data. Based on the mutual dependent relationship between vegetation and environment and their comprehensive reflections in remote sensing images, the paper advances an analystic method of landscape-ecology analysis Jay these images, i. e. to combine the tone and shape structure features in the image with the ecological rules of the community to analyse, and consider this as the basis of the methodology for vegetation visual interpretation. On this basis, the waters and sand bars in the Dongting Lake are divided into 5 landscape-ecological models, and the vegetation of lake regions is divided into 17 basic vegetation types.

The stomatal diffusive resistance of plants has close relation with the particle pollution in the environment. We can even use this physiological index to indicate the degree of particle pollution in the environment and to select species which have strong resistance to pollutants and consume less water.The results of research show that the degree of stomata diffusive resistance differs in different areas. In Tianjin it is in the following order: the Smeltery area (a polluted heavy-industry area)>the Water Park area (a sight-seeing area)>the Quanyechang area (a business area) >the outskirts of the Chemical Works (a chemical polluted area)>the Panshan area(a clean area). In Beijing the order is: the Sleeping Buddha Temple-Cherry Vale area(a sight-seeing area)>the Dongdan area(a heavy traffic area)>the Capital Iron and Steel Works area(a polluted heavy industry area).The reasons for the difference are not only concerned with industrial pollution, but also with the activities of the people in the two cities, for example, the heavy-industry areas in both cities are heavily polluted by dusts in the air and the stomatal diffusive resistance of plants, becomes higher, but it is lower in the Capital Iron and Steel Works area in Beijing, it is than in the Smeltery area in Tianjin, because the leaves of trees are often washed with watered in the former. In parks and business areas a large crowds of people may cause the raising of dusts, which also results in higher stomatal diffusive resistance. The results of research also show that when dusts in the air would increase, the stomatal diffusive resistance of plants increases and reduce the rate of transpiration, becomes smaller correspondingly

In this paper, the deviation sum of squares method of the clustering analysis is used to deal with the herbs beneath the frigid-temperate coniferous forest. The herbs are distributed on the shady slopes and semi-shady slopes of the mountains with an altitude of 1800–2800m above sea level in north Guan Qin-Shan area. The clustering analysis results are interpreted in combination with the environmental factors. The result indicates that the most important environmental factor which influences the distribution of herbs is altitude. Altitude has more-influence on herbs beneath trees than forest types. Thus the latter become the secondary factor of influence. The vertical zoning of herb distribution is as follows: 2850—2500m, 250D—220Dm and 2200—1800m. In the same altitude range, variation of the distribution of herbs beneath trees also exists owing to different behaviours of upper arbores, some physical and chemical characters of the soil and activities of human beings.

The authors have explored characteristics of nodulation and nitrogen fixation of several tree legumes, the influence of soil condition and their growth through field investigation and pot-culture experiment. It is of great significance for greening wasteland, soil amelioration and promoting ecological balance that Cajanus cajan, Tephrosia candida and Robinia pseudoacacia are planted on the cinnamon red earth of the southern subtropical zone, and that Albizzia kalkora and Robinia pseudoacacia on the purplish soil of the middle Subtropical zone.