Basing on the multivariate analysis—ordination, quantitative classification, and environmental interpretation of 163 plant community samples collected from Ngari, Xizang, the primary vegetation types, ecological gradients, and their quantitative relations with environmental factors of Ngari are given. The basic analysis contains the following three steps. 1) the two principal ecological gradients are brought to light by two vectors of ordination scores produced by detranded correspondence analysis (DCA); 2) the nonhierarchical and hierarchical classification systems of plant communities are produced from the 2-dimensional scatter polt of DCA ordination and two-way indicator species analysis (TWINSPAN), respectively; 3) environmental indexes (quantitative interpretation) of various vegetation types are given by the multivariate regression analysis which connects the ordination scores with environmental and geographical parameters. It is shown by the analysis that the vegetation types of Ngari and their distribution are mainly determined by the thermal and moisture gradients. The former could be expressed quantitatively with the mathematic expression of geographical parameters, the latter with the soil characteristics. The two gradients contain quite different vegetation types, species, and habitates, ranging from low montane warm desert to alpine periglacial vegetation, and from intrazonal bog and saline meadow to zonal plateau desert and steppe with their paricular position and ordination scores. That shows that the quantitative analysing method used here for handling the ecological data of plant communities with great ecological diversity is highly efficient.

GM(1,N) model of the Gray System Theory has been extensively applied to the analyses of systems of agriculture, forestry, ecology and many other life-related systems. The model is mathematically a linear system model with constants coefficients. However the development of both individuals and the population in biological systems is always, to different extent, affected or limited by finite resources and the competition among individuals and populations, which is known to be a primary contributor to the system nonlinearity. Hence the assumption of linearity behind GM (1,N) Model in general is not justified except some special cases. Even though the residual model of Gray Theory can be used to improve the accuracy of the system prediction, it contributes very little to the primary purpose of system modelling, i.e., to gain insight into the system and to capture the essence of system mechanism behind the observed data, because the residual model is usually difficult to interpret. This research is a study on the applicabil ityof GM(1,N) model on biological systems. Two different measurements of system behavior regarding the linearity, the system linearity (SL) and the significance of system nonlinearity (SSN) are defined to provide criteria and justification for the application of GM (1,N) model based on the system observations before final model solution is attempted. When the system does not satisfy the linearity criterion, it is better to seek alternative nonlinear models instead of relying on the residual model, Hence this paper is the also a early step to handle system nonlinearity regarding the Gray Model applications, The developed system behavior measurements were applied to computer-simulated systems of different nonlinearity, with results showing consistent measurements. In addition, a different formulation compared to the original GM(1, N) Model is used to obtain the model constants with more precise predictions and, in some cases, less amount of computation.

The Jiulongshan mountain district is situated in 28˚12′N. and 118˚52′ E. at the southwest of Suichang county in Zhejiang Province. The total area is more than 75 square kilometers, and the highest peak of which is 1724 meters above sea level.The flora of Jiulongshan area abounds with plants species and list of primary study includes 143 families, 584 gemera and more than 1149 species. In general, its origin is rather ancient. Its main compounents are those of subtropical and tropical areas.According to the result of numerical taxonomic analysis using the software of NTS system on microcomputer, 6 main vegetational types: the evergreen broad leaved forest, the mixed evergreen and deciduous broad leaved forest, the deciduous forest, the hilltop brushwood, the coniferous forest and the bamboo forest could be recognized. Basically, the evergreem broad leaved forest is the zonal vegetation, but the current representative vegetation there is the mixed evergreen and deciduous broad leaved forest.

After determination of the physiological property of photosynthesis and water relation of seven species of Saxoul forests including their intensity of photosynthesis and respiration, chlorophyll conent, stoma status, distribution of photosynthetical outcome, primary productivity and utilization efficiency of water, etc. It was discovered that Eremophyte species have high efficiency of photosynthesis and water utilization. The average intensity of photosynthesis of Haloxylon ammodendron during June to September is 8.02 CO2·mg/g dry weight. Hour, close to the Populus bolleana (8.39) which is amesophytes. The transpiration coefficient of Haloxylon persicum (250.12mg water/g dry weight) is about the half of Populus bolleana (502.45). The high efficiency of photosynthesis and water utilization of Eremophyte may be attributed to long adaptation to the ecological environment of high temprature and aridity. Currently, Saxoul forests are only used as firewood by local residents, which is neither economical nor rationable and needs improvement.

It has been found that Tamarix can migrate and reside naturally in nonriver-bank region of desert. The necessary conditions for the plant to germinate are: big rain fall, which leads to waterlogging in growth season, suitable soil structure and the seed source. These conditions are seldomly satisfied in Xinjiang at the same place and time, thus the seedling group is very rare, and the age distribution is uncontinuous. On the other hand, the bush wood usually has a long life. Without artifical disturbance, these bush woods will regenerate by filling up the seedling continuosly.

Throughfall, stemflow and canopy interception, water retaining capacity of the litter, variational soil water content, soil losses and surface runoff of the plot of retained litter and lost litter as well as the input of elements (N, P, K, Ca and Mg) by rainfall and the output of elements by surface soil erosion in evergreen broad-leaved forest and Pinus yunnanensis forest have been studied in Tonghai county during the rain seasons of 1986 and 1987.The results showed that the ability of regulating rain water of two forests was different. In evergreen broad-leaved forest, average annual percentage of canopy interception was 18.2% of the rainfall and was 13.4% in Pinus yunnanensis forest. The average annual percetage of stemflow for two forests was only 0.3–0.5% of the rainfall. The soil water content of evergreen broad-leaved forest was 15–40% higher than that of Pinus yunnanensis forestThe amount of soil erosion in two forests were closely corre lated to the litter loss. After loss of forest litter, the amount of soil losses and surface runoff increased by 11.4 and 1.3 times in evergreen broad-leaved forest and 12.9 and 3.3 times in Pinus yunnanensis forest. The input and output of nutrients in two forests also were different. The amount of NH4-N, P, K, Ca and Mg input by rainfall in evergreen broad-leaved forest was 15.2, 0.5, 50.4, 18.9 and 8.6 kg/ha.a respectively, and the same quantities in Pinus yunnanensis forest were 11.2, 0.6, 40.2, 11.4 and 7.5kg/ha·a respectively. The total amount of the elements output by soil erision in the former forest was 1.6kg/ha·a and that for the latter forest was 0.8 kg/ha.a, and the amount of the elements by soil erosion in two forests increased by 2.4 and 4.2 times respectively after loss of litter layer.

This paper has studied the growth rhythm, dry weight of grasses of seven species and relationship between factors of environment. The quality of grasses in Kobresia humilis meadow, which is main vagetation type of Qinghai Xizang plateau, is excellent, so they occupy a very important place in animal husbandry. The results are as follows:The distribution is an aggregated dispersal on grasses of seven species in Kobresia humilis meadow. The number of individual tillers after green up increases with increase of precipitation, sunshine time and accumulated tem, greater than 3℃ and reaches peak in early booting period.The critical value of low tem. is 3℃ for growth of grasses population. The populations begin to bud bursting at average daily air tem. ≥3℃.The course of development become quickly at average daily air tem. ≥ 5℃. The aboveground dry weight of an individual after green up begins to increase with increase of≥5℃, ≥10℃ accumulated tem. and precipitation. The dry weight is biggest at late August or early September.The populations need about 134 days from green up to ripeness of seed. In this period, the accumulated tem. of≥ 5℃ is about 949.7℃; accumulated tem. of≥10℃ is about 485.6℃; sunshine time is about 812.0 hours, amount of accumulated precipitation is about 324.9mm. The primary factor affecting growth is temperature (p<0.01) , and the second is precipitation and water content of soil (p<0.01)

Height and coverag of Aneurolepidium chinense community had a good correlation with its biomass above ground(R= 0.9316). A multivariate regression equation was established for estimating aboveground biomass of the community. Data of spectral reflectance for simulated band3(0.63—0.69 um) and 4 (0.76—0.90um) of thematic mapper or landsat4or5,were collected with a handheld radiometer in three principal grassland plant communities (Aneurolepidium chinense community ,Aneurolepidium chinense + forbs community and Stipa baicalensis community)during plant growing seasons in 1988.The study showed that vegetation index(VI)had the best exponential correlationship with aboveground biomass in comparison with that of IR or IR/R for each of the communities. Therefore, with change of the growing seasons nine different spectral models related to VI for estimating aboveground biomass of the communities were established.

Ecological experiments on wheat in sowing stages of spring were arranged on Shijiazhuang,Yulin, Yinchuan and Zhangye during 1983—1985.These locations have similar latitudes, but their longitudes and elevations are very different. Mianyang 11 is a spring wheat. Its growth period from sowing to maturation for the experimental wheat variety has apparent difference between different locations. Experimental results showed that average day air temperature in growth period of wheat could decrease for about 0.3℃ and the growth period could be increased by 2 or 3 days with every 100 metre increment in elevation has go up. On the other hand, this period of growth could be reduced for about two days with one degree decrease in longitude in the range between 38˚N and 39˚N in China.