The method of J. Moravec (1972) used to research the correlation between homotoneity and constancy of species has been applied to the steppe communities in the southern part of the Song-Nun Plain. The result shows a regularity of quantitative correlation of the species constancy in a community, frequently Ⅴ>Ⅳ⋛ Ⅲ< Ⅱ< Ⅰ. The homotoneity of releves is mainly dependent on the number of high-constancy species and their constancy per releve. From this relation, the homotoneity-coefficient of set of releves is calculated. The lowest value is 39.6% and the highest is 72.3%. By using these values and qualitative analysis, the steppe communities in the southern part of the Song-Nun Plain can be divided into 11 community types. The above is recommended as a simple quantitative method for classification of plant communities.

The Chinese arborvitae, as an important species of silvicultural tree, is a kind of evergreen coniferous tree widely distributed in the northern part of China. It can even grow in the crevices of limestone due to its ability to endure poor soil and dry habitat. Natural secondary forests or cultivated trees are widely distributed on sunny and half-sunny slopes of mountains in the district of Beijing at elevations of 200–900m. The floristic composition of natural Chinese Arborvitae forest is mainly consisted of various species of Compositae, Graminae, Leguminosae, Liliaceae and Rosaceae. Especially, species of Compositae and Gramineae are abundance.The plant life form spectrum of Chinese arborvitae forest shows that Hemicryptophytes and Phanerophytes are rich, they make up 38% and 37% of total species, respectively. Geophytes occupy 12% of total species, Therophytes and Chamaephytes are 8% and 5%, respeetively. According to significant corelation between diameter at breast height, height of tree and the dry weight of stem, leaves and roots, the optimum models are obtained by the dry weight of various tree parts (W) against diameter at breast height of tree: W(stem) =l69.82D1.92 (P<0.001),W(branch)=28.64D2.41 (P<0.01), W(leaves)=10D2.82(P<0.001), W(roots)=e4.99+0.387D(P<0.001).The biomass of stem, branches, leaves and roots in Chinese arborvitae plantation are 15.56 t/ha., 6.57 t/ha., 5.16 t/ha. and 5.29 t/ha., respectively. The total biomass of tree layer is 32.58 t/ha. The biomass of shrub and herb layers shows seasonal change, they are 7.17 t/ha. In September. The total biomass of Chinese arborvitae plantation are 39.75 t/ha.

The Gongga Mountain is located on the southeast fringe of the Qinghai-Xizang Plateau, i. e. the middle part of the Great Snow Mountain Range of the Hengduan Mountain Ranges. The Gongga Mountainous region is situated in 29˚20′—30˚00′N. and 101˚30′—102˚10′E., with its main peak being 7556m above sea level. There are 2500 species of vascular plants belonging to 869 genera and 185 families in Gongga Mountainous region. The main floral characteristics of the Gongga Mountainous region are shown as the antiquity of the origin of the floristic composition; marked differentiation of species; abundant endemic species; complex composition and obvious geographical replacement phenomenon. The main vegetation types of the Gongga Mountains are: Subalpine conophorium of Abies, Picea; mid-mountain eonophorium of Pinus and Tsuga; low-mountain conophorium of Pinus, Cunninghamia, Cupressus, and Keteleeria; mixed wood of conophorium and broad-leaf forest of Tsuga, Acer and Betula; evergreen forest of Cinnamomum, Phoebe, Machilus, Lithocarpus and Cyclobalanopsis; deciduous broad-leaf forest of Quercus, Betula, Acer, Populus and Alnus; hard-leaf evergreen forest of Alpine-Quercus; alpine bush-wood of Rhododendron, Salix and Sabina; river-valley busy-wood of Acacia, Opuntia and Bunhinia; alpine meadow and “rock stream” sparse vegetation of Kobresia, Festuca, Allium, Saussurea, Soroseris, etc.The horizontal zones of vegetation in the Gongga Mountainous region is the aiphyllium with the characteristics of the east and west parts of subtropics in China.The vertical belts on the eastern slope are: 1. Evergreen broad-leaf forest belt at alt. 1100—2200m. 2. Coniferous and broad-leaf mixed forest belt at alt. 2200–2500m. 3. Subalpine coniferous forest belt at alt. 2500—3600m. 4. Alpine bush and coryphilum belt at alt. 3600–4600m. 5. Open vegetation belt of alpine “rock stream” belt at alt. 4600–4900m.6. Alpine nival belt at alt. 4900m.The vertical belts on the western slope are: 1. Subalpine coniferous forest belt at alt. 2800—4000m 2. Alpine bush and meadow belt at alt. 4000–4800m. 3. Open vegetation belt of alpine "rock stream" belt at alt. 4800—5100m. 4. Alpine nival belt at alt. 5100m.

Ginkgo biloba and Metasequoia glyptostroboides are two endemic tree species of China. In this paper, the decomposition rates of their litter placed under Ginkgo and Metasequoia forests in the parks in Beijing have been studied. The weight loss rate of the ginkgo litter placed under ginkgoes for 380 days was 55.63% and that for the metasequoia litter placed under metasequoias for 338 days was 53.39%. The exponential decay model was used and the annual decay rate of litter was estimated to be 0.771 g/(g·year) for the Ginkgo, and 0.824 g/(g·year) for the Metasequoia. Analysis of the chemical composition change in the litter showed that the changing tendency of the weight loss rate was in agreement with the net loss of the chemical composition in the litter. During the annual decmoposing process, the ratio of the carbon content and the nitrogen content of the litter decreased with the passage of time.

Plant residues are the main component of peat and its mineral bodies. The composition of plants in the peat has close relations with the decomposition degree and the nutrition status of peat. The composition of plant residues is an important basis for making the classification of peat. The mineral bodies of peat in China are now tentatively divided into 11 groups of 4 types, which are classified according to the principle of taxonomy by the features of these mineral bodies and their qualitative differences, and on the basis of the components of the plant residues in the mineral layers.

Based on the suitabilities of Poacynum hendersonii to the soils, which were formed by the combined effect of different topographic positions, soil salinity, the depth of groundwater level and other ecological factors, the present authors differentiate the soils in the Tarim Basin with stands of P. hendersonii communities into five soil habitat types: meadow soil in flood land, saline soil with high groundwater level, saline soil with middle groundwater level, saline soil with low groundwater level, and desertification desert forest soil in the light of plant appearance, plant growth, chemical composition and other characteristics of the P. hendersonii grown on such soils, and suggest that we should use and protect properly this natural plant resource depending on the different soil habitat types.

In field trials in 1981–1982,33 experimental sites were established in Pucheng County Shaanxi, for studying water consumption (WS) of winter wheat under dryland condition. About 303–476mm of water were consummed by wheat in its whole life at different sites, which yielded grain range from 45 to 333 kg per mu respectively, with its water use efficiency (WUE)varying from 0.38 to 1.15. The correlations between the grain yield and the WS or the WUE were close, and all of those were positively correlated with the shoot growth rate of wheat in the seedling stage before regrowth in the following early spring. It was concluded that under non-irrigation condition, wheat growth and yield were dependent markedly on the available water preserved in the soil of its root distributed layer from the rainy season. To raise the crop productivity of dryland wheat, a system that can promote wheat root to strike downward to deeper into the soil and raise its drought resistance power and grain yield in different water conditions is recommended.

This paper discusses the interference of forest fire in forest ecosystem proposes to use the forest fire destructive force which called FOREST FIRE SEVERITY INDEX (FFSI) as a measuring standard and also suggests to use the volume of forest (timber) as the index of the state of its forest ecosystem. According to the physical analysis of the process of the spreading of forest fire, a combustion spreading equation is deduced as a model and the destructive force of the fire of the Xingan-mountain larches is calculated at different spreading speeds. On the basis of the investigation results of the consumptive available fuels, the authors point out how forest fire influences forest ecosystem at different levels of FFSI and how forest fire should be dealt with according to its intensity.