The effect of eitrie acid and glucose on P uptake by different species of Cultivated and wild plants, and P fraetlonations of the soil was investigated in an acid Ultisol. Experiments were conducted in the greenhouse, using continuous addition of citric acid and glucose solutions, and a complete budget study designed to examine the changes of soil phosphorus in various fractions employing a P fraetionation procedure. Without inorganic P additions, citric acid increased P uptake by soybean (Glycine max (L.) Merr.) and sorghum (Sorghum bicolor), indicating that citric acid solubilized the P bound by A1 and Fe oxides. The addition of P (20mg P kg-1 soil)in combination of a continuous addition of citric acid solution resulted in higher P uptake by soybean and sorghum. The addition of glucose, with and without addition of P, did not change the P uptake by plants. However, the addition of glucose increased the organic P in NaOH fraction, and a decrease in inorganle NaOH fractions. A negative microbial P was obtained for all the treatments, especially when glucose was added. This suggests that the method described by Hedley is not suitable for determination of microbial P in very acid soils having little orgame matter content. The increase of P uptake by sorghum and a decrease of P in the NaOH fractions in the soil with the addition of inorganie P and citric acid suggests that organic llgands can prevent P from being fixed by soil particles. The addition of oak (Quercus spp.) and red clover (Trifolium pratense) litter to a similar acid soil resulted in a higher P uptake by pokeweed (Phytolacea americana). After a period of 7 months, the resin-P and inorganic bicarbonate P decreased substantially compared with the P at the beginning of experiment. This can be attributable to the P uptake by plant, P taken up by microbial organisms, an increase in organic P,and an increase in HC1 fraction.The results also showed thatboth clover and oak litter did not increase the inorganle P in NaOH fractions. This indicates that products of organic matter decomposition might have prevented the mineralized P from being immobilized by clay partleles and Fe- and Al-oxides. An attempt was also made to elucidate the mechanisms involved in the P solubilization by the products of organic matter decomposition, and the resuetion of P adsorption by Al- and Fe-compounds in the presence of organic ligands.

Global change has received more and more attention for the decades, CO2 concentration in the atmosphere is increasing at a much faster rate than that observed in the historical records. Understanding how terrestrial ecosystems would respond to global change induced by CO2-enrichment is necessary for ensuring the earth suitable for human existence and sustainable development in future climate. The study on climate-vegetation interaction is the basis for the research of terrestrial ecosystems′ responses to global Change, mainly including two important parts: climate vegetation classification and net primary productivity (NPP)of natural vegetation. A new method of climate-vegetation relationship is presented in the present paper. The potential evapotranspiration (PE) calculated Thornthwaite formula or Penman model represents PE from small evaporating area. It is not able to reflect a regional energy. However, regional potential evapotranspiration (RPE), which can reflect a regional energy, should be used in climate-vegetation relationship. Therefore, it is not suitable to use PE as the index of climate-vegetation relationship. According to Bouchet′s model and the regional actual evapotranspiration model established by Zhou Guangsheng and Zhang Xinshi(1995), RPE is readily calculated. Two indices of climate-vegetation relationship: thermal index (TI) and regional moisture index (RMI) are suggested. This system is used in China based on the data from 647 meteorological stations. The results show that this system can reflect the distribution of vegetation zones in China. The study will help to study on the distribution of vegetation, to predict the possible impact of global change on terrestrial ecosystems, and to make scientific strategies for the global change.

Photosynthesis and transpiration of main constructive plants (Artemisia ordosica, Caragana intermedia and Salix matsudana) in Mu US Desert were measured with model LI 6000 photosynthesis system in different periods. In addition, the photosynthesis active radiation, relative humidity, leaf temperature, air temperature, intercellular CO2 concentration, stomatal resistance, leaf water potential, soil moisture and so on were also measured. The results showed that photosynthesis and transpiration for different species at different periods were different and closely related to environmental conditions and plant internal factors. Photosynthesis active radiation was the dominant factor, and leaf stomatal resistance also played an important role in plant photosynthesis and transpiration. Different plant species had different responses to natural conditions, among them, Caragana intermedia was more sensitive than the other two species. The effect of soil moisture condition on leaf water potential of Artemisia ordosica was most noticeable. Water use efficiency of Caragana intermedia was also higher as compared with the other two species.

Amount of storage, annual increment and decomposition of coarse woody debris (CDW)were examined in a 76-year old Castanopsis eyrei forest of wuyi Mountains. A comparative analysis of CWD storage in an age sequence of C. eyrei stands was carried out and its role in nutrient cycling in the ecosystem was initially estimated. Amount of CWD storage, annual increment and decomposition were 7.349%, 1.425 and 0.512 tons·hm-2·a-1, respectively. As the age of C. eyrei forest increased, CWD storage increased initially, arrived at the climax gradually at the age of 58 years, and declined then. CWD is a relatively important components of C. eyrei forest ecosystem. It contributed to 0.09%～1.91% of total nutrient storage in the total biomass of the ecosystem. About 1.94%～4.84% of total returns of nutrient element was through this route.

Litterfall and its dynamics in the forests dominated by C. glauca in Zhejiang were studied from September 1986 to August 1992. The results show that the mean annual litterfall was 5547.6kg·hm-2·a-1. Dead leaves, dead branches, dead fruits and other components of the litter contributed to 68.32%, 14.82%, 15.045% and 1.82% of the litter mass, respectively. Each of the litterfall type in the forests had evident seasonal dynamics and inter-annual fluctuation. The features of litterfall reflect general biological and ecological characteristics of the plant community to a certain degree.

Based on the field monitoring data, this paper deals with the hydrologic ecology of R. pseudoacacia plantation in the hilly loess region, northwestern Shanxi. The results show that the soil water conduction of the plantation was very poor and the available water content was very low during the growing season. The transpiration intensity (TRI) of the species was 0.1140g·g-1·h-1±0.0586 in growing season. The daily change in TRI was very significantly correlated with light intensity, but less with air temperature. Moreover, it was not significantly correlated with relative humidity. The water potential (WP) of the species was 1.759-MPa±0.457 in growing season. The daily change in WP was significantly correlated with air temperature, but less with relative humidity. Moreover, it was not significantly correlated with light intensity. The correlation between seasonal change in TRI and soil water content was not significant, but that between seasonal change in WP and the later proved significant. The correlation between the seasonal changes in TRI or in WP and the light intensity, the air temperature and the relative humidity was not significant. The water consumption through tree transpiration and the water consumption by the community evapotranspiration accounted for 16.3% and 68.0% of the precipitation, respectively, during the same period.

Based on the matrix model and spatial pattern distance method, the structural and dynamical characteristics of the Pinus Kwangtungensis population, one of pioneer and constructive species in the forest succession series in Karst mountain of Maolan were studied. The results showed that:(1) The population was a senescent population. (2) The relation between the age (E) and the diameter at breast height (D) of the popuiation was E=59.968/(4.041-lnD). (3) The spatial pattern of the population was characterized by a iniform distribution of patches in which individuals were clumped. (4) Population donsities (DS) in each diameter class tended to change with diameter at breast height (DG), the relation was DS=1/(0.058+0.018e-DG). (5) The population is a pioneer population. At certain special habitats, the species, together with other species could form a relatively stable community. (6) To a certain extent, the distance method and matrix model can be effectively used in the analysis of the spatial pattern for subtropical forest species.

The middle-mountain moist evergreen broadleaved forest is the major forest type in the vertical vegetation zone of subtropical mountains. Its typical representative is the forests in Ailao Mountain, dominated by Lithocarpus xylocarpus, L. chintungensis and Castanopsis wattii. The biomass and mean annual net accumulation for the pre-matured and the matured or over-matured forest communities were estimated through harvesting and correlation: The results show that the biomass was 508.57t·hm-2 and 293.04t·hm-2 in the prematured and the matured or over-matured forests, respectively. Mean annual net accumulation was 12.1051 tons·hm-2·a-1 and 7.7443 t·hm-2·a-1, respectively. The causes for the differences were also analyzed. The leaf area index (LAI) of the two forest stands were 10.04 and 8.96, respectively. The regression models by which the biomass of different organs of dominant tree species in the community was estimated were established. The status of construcrive species in the communities was also explained in the light of biomass production.

Ephemerals are a group of plants in arid and semi-arid area. By analyzing weight dynamics of 10 species of ephemerals in Fukang Desert Ecosystem Observation and Experiment Station of Xinjiang, The Chinese academy of Sciences in 1991, the following was found out:1. The weight of most ephemerals greatly changed during their growth and development processes. There was one peak on the growth curves of most ephemerals except for Eremurus anisopteris (Fig. 1) 2. The weight of most ephemerals increased rapidly in May. Their weight peaks took place during the middle ten days of July (Table 2).3. The growth characteristics were evidently different among the species of ephemerals. According to the differences the ephemerals could be divided into three types: perennial vegetative propagation type, perennial vegetative and seed propagation type and seed propagation type (Fig. 2, 3).4. The proportion of fruits to the aboveground weight of ephemerals was obviously higher than that of long life cycle herbage (Table 1). The Lowest was 21.5% and the highest was 77%.5. Weight dynamics of most ephemerals were closely related to their height and phenological phase (Fig.1). The shapes of weight and height growth curves were similar during the earlier period of growth and developnent. The weight of most ephemerals increased rapidly in the period of reproduction.

Based on both species-abundance relationship and species diversity, nature of community structure was analyzed under different grazing intensities in alpine meadows and alpine bushlands. The results show that the relative abundance, which accords with the lognormal distribution, demonstrated regular change with growing intensities. Though the community structure changed, the values of indices (e. g. Simpson′s diversity index, λ, shannon′s diversity index H′, McIntosh′s diversity index Dmc evenness index E and species richness R) that are normally used to descibe the nature of communities of different grazing intensities. All above indicate that the changes in community structure can not be explained perfectly by comparing values of species diversity indices only, This result also confirmed the West′s supposition.