Effects of several ground factors on evapotranspiration from the steppe communities were observed at Inner Mongolia Grassland Ecosystem Research Station of Academia Sinica. The results were as follows:1. Effects of the soil factors:(1)Under normal conditions ,evaporation ,transpiration and evapotranspiration from the community increased with increase in the soil moisture. When the soil was too wet, transpiration from tile community decreased due to that the plants were damaged by waterlogging. (2)Under low soil moisture condition, evaporation from the community decreased with increase in soil clay content. Under high soil moisture condition, evaporation from the community increased with increase in soil clay content. (3)Evaporations from the community having different soil moisture were increasing with increase in the soil compaction, and reached their maximums successively. The drier the soil was, the later the maximum reached.2. Effects of the grazing factors: Transpiration from the community was negatively correlated with the grazing pressure, but evaporation from the community was positively correlated with the grazing pressure. Decrement of the community biomass with the grazing pressure was the key reason for the positive and negative correlation.3. Evapotranspiration from the deteriorative and its recovery communities: Increase in evaporation and decrease in transpiration were caused by deterioration of the community, otherwise, decrease in evaporation and increase in transpiration were caused by recovery of the community. To a certain extent. T/E value of the community could be greatly changed by deterioration on recovery of the community, but evapotranspiration from the community kept constant.

The study on the water ecophysiological Characteristics of Caragana korshin skil shows that the transpiration rate (Tr) was 395.1±234.4 mg·g-1·h-1; the small branch water potential (Wp),-1.588±0.583 Mpa; the leaf water content (Wc), 60.12±3.29% and the transpiration coefficient, 72.82±19.88 gH2O·gDW-1. The correlations between soil water content and the Tr,Wp and Wc were statistically significant. The drought resistance was much stronger in the drought period (from June to July) and at the end of autumn (in October)than in the rapid growing periods (in May and from August to September), resulting from the responses to the annual changes in the growth and developmental stages as well as the environmental water conditions, from June to September, the Tr, the Wp and the Wc, respectively, were correlated negatively with the drought resistance index.

The productive capacity of the natural forests that dominated by Zenia insignis in North Guangdong limestone region was investigated, and compared to that of a 6-year-old artificial Zenia insignis forest. The results show that the biomass, stocking, increment, gross primary productivity of arbour layer and PAR energy use efficiency in the natural forest in natural Zenia insignis forest was 125.38t·hm-2, 86.35m3·hm-2,3.69t·hm-2,84284kJ·m-2·a-1 and 1.39%,respectively, suggesting that its biomass and productivity were lower than those of the evergreen broad leaf forest in humid region [1 ,2,10], but were higher than those of forest in subtropical semi-arid region [9]. The photosynthesis rates of Zenia insignis was higher, but the crown density and leaf area index of artificial forest was lower as compared to those of natural forest. So the gross productivity and solar energy utilization ratio of the artificial forest was low. All above indicate the higher productivity potential of the artificial forest.

The biomass and the some leaf characters in the seedlings of two dominant tree species in Dinghushan forests were studied under long-term elevated [CO2] conditions. Potted seedlings of Castanopsis fissa and Schima superba were grown in semiopen top chambers with ambient (350μl·l-1) and superambient (500 μl·l-1) [CO2] under natural light. With increasing [CO2], the total dry matter of whole plant increased by 16.6%～26.6%,and both the ratios of underground to total weight and the root/shoot ratio increased. Whereas, the increase in stem diameter of the basic part and the decrease of plant height were also observed under [CO2] enrichment. In addition, the increase of leaf density, leaf thickness and specific leaf weight were associated with the decline of internal space volume. When expressed on dry weight basis, the contents of total nitrogen, Mg, fructose, glucose and sucrose as well as the N/C ratio of leaf of C. fissa reduced obviously by elevated [CO2], but no obvious change in total carbon, soluble sugar, Ca, P and K was observed.

The effects of long-term elevated CO2 on functions of PSⅡ in soybean leaves were studied. The results showed that the potential activity and efficiency of primary conversion of light energy of PSⅡ , quantum of PSⅡ electron transport were stimulated, photochemical quenching coefficient was increased and non-photochemical quenching coefficient was decreased under elevated CO2. The improvement of PSⅡ functions could be one of important factors which result in increases of the photosynthetic rate and yield of soybean under elevated CO2.

A systematic study on dynamics of individual dry weight increment, net mean productivity, stand biomass and primary productivity of alder and cypress artificial mixed forest has been carried out in Yanting county, Sichuan province. The study on the biomass of stands at different ages shows that the biomass accumulation of different organisms at stand age and the proportion of trunk increased while those of leaf, branch and root system weight decreased. The average net productivity of alder tree increased from 2 and 12 years old and reached the peak in the period between the 12th to 14th year and then decreased gradually after the 16th year. The same tendency was presented in the alder biomass structure and in its vertical distribution. These indicate that the quantitative maturity of alder occurred as it was 18 years old in the mixed forests. The accumulation of cypress leaf showed a so-called "advanced phenomenon'. The net primary productivity of the cypress trees fitted "J" type of curve. The biomass structure and its vertical distribution were still in the state of dramatic differentiation in the duration between the 2nd and 18th year of plant growth. Among a few types of subtropical artificial forests, the biomass and net primary productivity of the alder and cypress mixed forest is the relatively high. Therefore, this kind of artificial forest may have integrated ecological and economic benefits.

Litter decomposition and its nutrient dynamics of a pine forest in Dinghushan Biosphere Reserve were studied in a period of 572 days. Mass loss in both decomposing pine needles and mixed litter (about half pine needles and half understorey litter) showed linear decrease with time during the experiment. The decomposition coefficients (k) were 0.44 a-1 and 0.37 a-1 for pine needles and mixed litter, respectively. Nitrogen was the only element that showed increase, in the first period, in concentrations (in the first 329 days for needles, 117 days for mixed litter) and in contents (at about 200～250 days), and thereafter showed decrease over the rest of the experiment. P and Ca exhibited similar pattern in terms of concentrations and contents, close to the linear rate of mass loss. K is the most mobile element. Its patterns of concentrations and contents in decomposing litter were similar: the greatest loss during the first period (30 to 50 days), after then slightly fluctuate. Mg showed a relatively rapid initial loss in terms of concentrations and contents, thereafter followed a steady decline in contents but slowly increased in concentrations. The nutrient mobilities of the five elements in both processes of decomposing litter followed the following order: K>Mg>P>Ca>N.

As clonally growing in heterogeneous environments, a single genet may place its ramets in different microhabitats. In this process, mortality (risk) of the genet is spreaded. Risk-spreading makes a great contribution to maintenance of or even increase in genet fitness. Therefore, clonal growth was considered having adaptive value, particularly in fine-scale heterogeneity of environment. Responses of a pseudoannual clonal herb, Trientalis europaea, to a nutrient gradient provides an example of genet riskspreading. Meanwhile, a hypothesis on the relationship between the maintenance of ramet-between connection and the enviromental heterogeneity is proposed.

Relationships between vegetation and climate,numerical regionalization of vegetation in Shanxi Plateau were studied using the detrended canonical correspondence analysis (DCCA) and two-way indicator species analysis (TWlNSPAN). It is shown that the first DCCA axe expresses the variation of vegetation and climate along latitude in Shanxi plateau. The vegetation types and their distribution along latitude were mainly correlated with the thermal and water-condition gradients. The second DCCA axe expresses the variation of vegetation and climate along longitude in Shanxi Plateau. The vegetation types and their distribution in this direction were mainly related with the annual precipitation and the evapotranspiration. In the plateau the changes in vegetation and climate along altitude are much greater than those along longitude because it extends longer from south to north than from east to west. Shanxi Plateau was divided into 17 vegetation districts using TWlNSPAN and DCCA. Three poles and a canter were recognized in the figure of DCCA ordination plot.

Stepwise clustering, one of the methods for non-hierarchical classification, has been introduced in this paper, and was applied to the classification of Elaeagnus mollis community in Shanxi. The results show that the stepwise clustering accomplished the objective process of the optimal classification through minimizing the sum of the squared deviations within plot group and by maximizing the sum of the squared deviations between plot groups. This led to minimum homogeneity within plot group and maximum heterogeneity between plot groups. The results of stepwise clustering tallies with the reality. Furthermore, it allows the work more efficient because we only need calculate the centroid distance from one sample to another. Compared with fuzzy c-means algorithm and with TWINSPAN, the result of stepwise clustering is similar to that of fuzzy c-means algorithm which has greater homogeneity within plot group. In addition, the stepwise clustering is superior to the TWINSPAN procedure, providing that the classification results do not require an obvious hierarchy among plot groups.

Species composition, diversity, distribution and growth of the seedlings in a natural forest stand and on a newly formed highway slope into the forest (considered as a special gap) were studied. Species abundance and Shannon-Wiener diversity of the seedlings were similar to that of the stand in which the plots were sampled (99 species cf. 117,5. 43 cf. 5.43) and higher than that in a comparable sample area on the highway slope(59, 4.21). For the seedlings in the forest, there were, in comparison with that on the highway slope, higher percentage of tree species (46. 15 cf. 34. 04) and lower one of herb species (23. 08 cf. 31. 92); higher similarity to the stand for woody species (coefficient of S ф rensen 0. 500 cf. 0. 171). Similarity between the two seeding floras was low (0. 247).Most of the dominant polulations in both habitats presented contagious pattern of distribution. Population on the highway slope seemed to have more intay slope smped characteristics.Seedings of pioneer tree species had higher or comparable RGR ( mean RGR for 1 ~ 5 years: 0.944 ~ 1.555 cf. 0.765 ~ 1.402 g ·g-1·a-1) but slower accumulative biomass growth than the seeding in the forest in much poorer soil. Shadetolerant seedings did not show dormant characteristics in the forest. Seedings of pioneer trees allocated higher percentage of biomass to leaf but those of late-successional species allocated more biomass to root.