The article deals with the effect of CO2 enrichment on the Quercus liaotungensis, a dominant of typical and natural deciduous broad-leaved mixed forests in the warm temperate China. The results show that the stomatal resistance, the transpiration rate, the dark respiration rate, the net photosynthesis rate, the diurnal net photosynthates and the water use efficiency of the plants grown under the CO2-enriched environment were 106 %, 92%, 98.9%, 155%, 172% and 179 % of those grown under the CO2-unenriched environment (CK),respectively. The response of the plants to the CO2 enrichment were more obvious in the growing peak period(June, July), in terms of the last three characters mentioned above. The leaf area, the leaf dry weight and the plant height of the plants growing under the CO2-enriched environment were 107%, 140% and 331% of those growing under CK, respectively. It is evident that the plants responded positively to the CO2-enrichment in terms of most of the physiological and growth characters investigated, suggesting that, as long as other environment are proper for the plant, the doubled CO2 concentration may fertilize the plant and increase their physiological process and bioproductivity.

The niche breadths and niche overlaps of 12 main plant populations grown on the gradients of soil water, soil salt and soil organic content in Leymus chinensis grassland for grazing were measured using the formulas described by Shannon-Wiener and Pianka. The results show the niche breadths of Leymus chinensis, which were greater than other species, were 0.910, 0.869 and 0. 930 on the gradients of soil water, soil salt and soil organic respectively. The niche breadths of Lathyrus quinquenervius, Heleochalis intevsita and Phragmites communities were much narrower. Chloris virgata, which is one of the pioneer plant of grazing succession, had much greater niche breadths (average on the three gradients 0.707) than the other two species (Suaeda corniculata, Puccinellia tenuiflora ). The niche overlaps between the species with broad niche breadth and other species were much greater. The niche overlaps among the species distributed in the same/adjacent grazing stages or the species which have the same/similar environment requirements were great. Under grazing condition, the process of community succession was the one of species’ niche separate.

Self-thinning of Spruce population on sandy land was investigated with population density regulative law. Population density dynamical process was simulated as well. Owing to plastic growth, the relations among average DBH, average dry weight of individual plants and density of population varied among spruce populations in various types of forest. Main factors involved in population regulation were analysed with principal components analysis. The results are as follows: main factors which affect self-thinning process of spruce population were the following 7 factors: orientation of slope, type of community, position of slope, average water content of soil, elevation, average unit weight of soil, and density of coniferous leaves. Mechnism of self-thinning and its applications in population density management which is very significant for spruce population management were also discussed.

Based on the results obtained in recent two years and the previous study materials, the dynamic changes of the aquatic vegetation in East Lake during the past 30 years were investigated and the correlation between the changes and some controlling factors such as the eutrophic and the fishery was analyzed. It was shown that the adverse succession of aquatic plant communities in East Lake exhibited the following seres:Potamogeton maackianus stage;Potamogeton maackianus +Najas major + Ceratophyllum demersum + Myriophyllum spicatum stage ; Potamogeton maackianus disappear stage;Najas major ruins stage;secondary bare area stage. Najas major+ Myriophyllum spicatum+Vallisneria spiralis stage at the present time in some subregions was the early phase of secondary succession. The mechanisms of species replacement in the succession seres were also explored with some characteristics of morphology, structure, ecophysiology, life span and reproduction strategy and interspecific relationship, etc. The aim was to provide the theoretical basis for the restoration and artificial control of aquatic vagetation.

The population dynamics of the three main plant species with which different kinds of dunes in Maowusu sandyland were aerially seeded was investigated. The results show that Artemisia sphaerocephala could only maintain as dominant or condominant for a short period in the case of mixed seeding with other species. Its population coverage usually reached the maximum in 3 or 4 years after the seeding and then declined at different rates according to degrees of the dune development in the seeded areas. The more developed the dune was ,the slower of the decline rate. The coverage of Hedysarum laeves had been maintaining increase in the first 10～15 years after seeding, and the period of being dominant was much longer. Hedysarum scoparium, because of its sparse growth habit, had a lower predominance in the communities. Its coverage kept rising in the first 5 years following seeding, and then went slowly down or kept stable.

The dynamics of soil NH4+-N and NO3--N in a pine forest of Dinghushan were investigated using ion exchange resin bag method. Soil NH4+-N and NO3--N both exhibited significantly seasonal variations, with the highest in spring and the lowest in summer. In the soil at 0～10 cm and at 10～20 cm depth, the mean values of soil NO3-N were 1. 722 and 1.429 μg·d-1· g-1 dry resin, respectively. However, in the soil at 0～10 cm and at 10～20 cm depth, the mean values of soil NH4+-N were 19.137 and 14.696 μg·d-1· g-1 dry resin, respectively. NO3--N was positively correlated with NH4+-N at both soil depths for most seasons (P<0.05) ,indicating the importance of ammonium supply in regulating nitrification rates.

Clonal diversity in six Cyclobalanopsis glauca populations were determined by means of allozyme analysis. Individuals per genotype were 1.270 and 1.508 at population and species levels, respectively. High clonal diversity was found in the populations. Mean Simpson’s diversity index for the six populations was 0.9882,and eveness averaged 0. 7921. 81.3% of the genotypes distributed locally. Only one genotype (0.5 %) distributed over more than 75 % of the populations. Correlation analysis shows a significant relation between Simpson’s index and total nitrogen (P< 0.05) ,and no significant relation were observed between clonal diversity and other environmental factors.

According to some climatological indexes, such as annual average temperature and precipitation,Kira’s warmth and coldness indexes,Penman’s potential evapotranspiration and aridity, Thornthwaite’s potential evapotranspiration and moisture index,Holdridge’s biotemperature and potential evapotranspiration ratio, the relationship between climate and dominants and companions of subtropical evergreen broadleaved forest in China were analysed. The results of TWINSPAN classification and DCA ordination of dominants and main companions show that these species could be divided into 8 kinds of types. These water-temperature distributional groups are :1) Megathermal humid type:Engelhardtia fenzelii , Castanopsis lamontii , Castanopsis fordii , Castanopsis fabri , Castanopsis fissa , Castanopsis kawakamii , Cyclobalanopsis chungii , Michelia maudiae , Manglietia chingii , Litsea rotundifolia var. oblongifolia , Cryptocarya chinensis , Cryptocarya densiflora , Cryptocarya concinna, Phoebe bournei , Gordonia axillaris , Adinandra millettii , Altingia chinensis , Altingia gracilipes, Exbucklandia tonkinensis , Schefflera octophylla , Ilex ficoides.2) Mega-mesothermal humid type :Myrica rubra , Engelhardtia roxburghiana , Engelhardtia colebrookiana , Castanopsis carlesii , Castanopsis jucunda , Castanopsis hystrix , Lithocarpus glaber , Lithocarpus hancei , Lithocarpus harlandii , Cyclobalanopsis nubium , Cyclobalanopsis jenseniana , Michelia foveolata , Manglietia fordiana, Manglietia insignis. Litsea elongata, Neolitsea aurata, Cinnamomum burmannii, Machilus thunbergii , Gordonia acuminata , Ternstroemia gymnanthera , Cleyera japonica, Schima superba, Distylium myricoides , Daphniphyllum oldhamii , Daphniphyllum macropodum , Elaeocarpus decipiens , Elaeoearpus japonicus , Sloanea sinensis , Dendropanax dentiger , Styrax suberifolius , Ilex purpurea , Ilex latifolia , Vaccinium bracteatum , Symplocos anomala , Symplocos sumuntia. 3) Micro-mesothermal humid type:Fagus lucida Castanopsis eyeri , Castanopsis fargesii , Castanopsis sclerophylla , Castanopsis tibetana , Cyclobalanopsis multinervis , Cyclobalanopsis gracilis , Cyclobalanopsis gilva , Litsea coreana var. sinensis , Litsea coreana var. lanuginosa , Neolitsea aurata var. chekiangensis , Cinnamomum chekiangensis , Machilus leptophylla , Phoebe sheareri , Liquidambar acalycina , Styrax odoratissima, Ilex suaveolens, Ilex wilsonii, Rhododendron latoucheae, Rhododendron ovatum, Rhododendron fortunei , Symplocos stellaris.4) Mega-microthermal moist subhumid type Fagus longipetiolata , Lithocarpus polystachyus , Cyclobalanopsis myrsinaefolia , Cinnamomum camphora ,Sassafras tsumu.5) Micro-microthermal subhumid type Platycarya strobilacea , Cyclobalanopsis glauca , Neolitsea confertifolia , Lindera megaphylla, Lindera communis , Cinnamomum subavenium, Liquidambar formosana, Rhododendron mariesii. 6) Microthermal subhumid type Myrica esculenta, Fagus engleriana, Castanopsis carlesii var. spinulosa, Lithocarpus cleistocarpus, Quercus phillyraeoides , Quercus engleriana , Cyclobalanopsis oxyodon , Phoebe zhennan, Schima argentea.7) Mega-microthermal dry subhumid typeCastanopsis orthacantha, Castanopsis delavayi , Castanopsis ceratacantha , Lithocarpus dealbatus , Cyclobalanopsis glaucoides , Cyclobalanopsis delavayi, Cinnamomum glanduliferum, Machilus ichangensis ,Phoebe chinensis.8) Micro-microthermal dry subhumid type Castanopsis platyacantha , Quercus spinosa , Quercus spathulata.

Tropic Ageratum (Ageratum conyzoides) ,a common weed in south China,was reported to have allelopathic potentials in our previous paper. In this paper, the allelochemicals from aerial parts of the herb were isolated and identified. Their allelopathic potentials were investigated. Two compounds,which were chromatographed by TLC and HPLC were obtained in pure form. They were identified to be 6,7-dimethoxy-2,2-dimethylchromene (ageratochromene) and stigmastra-5,22-dien-3β-ol by means of IR,NMR(1H,13C) and MS. Bioassay results show that the ageratochromene was highly inhibitory to the seedling growth of the acceptor plants. The treatment with 500 ppm ageratochromene inhibited the seedling growth of barnyardgrass (Echinochloa crusgalli) and radish (Raphanus sativas) up to 100 % and 90 %, respectively. Treatment with 25 × 10-6ageratochromene had statistically significant inhibition to the seedling growth of barnyardgrass and the shoot growth of radish.

The variations of SOD activity, POD activity, permeability in winter with six hybrid clones of Populus tomentosa were investigated. The results show that the SOD activity variation of the clones can be divided into two types and the variation patterns of other indexes were similar. The difference in the indexes value among the clones was significantly different, in December the permeabilities in all clones examined were lowest and the ability of cold resistance was highest. The results of comprehensive evaluation according to the indexes also show significant differences among the clones. There were significant correlation between the indexes and the result of comprehensive comparison.

In order to understand how the Yangtze River shelter forest community highness class construction be made of, we investigated plant community highness class number of plants, cover degree and number of species in 11 model of run-off plots of vegetation types in this area. The plant community highness class was regarded as coordinate axis. A series of new targets and equations, e. g. lost stable rate of plant number, cover degree fluctuative rate and species sharing degree, were put forward, for examining plant population or community dynamics and community construction. With this targets and equations, we quantitatively analyzed this series of highness class constructions of run-off plots of vegetation types and compared these models′advantages and shorters for their soil and water conservation effect.

Psychotria rubra and Rhodomytus tomentosa are the common shrubs in south China. The morphological, physiological and ecological characters of the shrubs were compared in this paper. The results show that: the number of root system, branch ,leaf of Rhodomytus tomentosa were larger than that of Psychotria rubra,the branch angles and distance of intervascular of Rhodomytus tomentosa were smaller than that of Psychotria rubra; the thickness of leaf and palisade tissue of Rhodomytus tomentosa were smaller than that of Psychotria rubra; Rhodomytus tomentosa was suited to sunny environment while Psychotria rubra grew well in shaded environment. In lower-subtropics, the light-transmissibility of community of 30% was the light undition under which the Psychotria rubra was able to invade but Rhodomytus tomentosa was not able to grow. The ecological strategies of the Rhodomytus tomentosa and Psychotria rubra were of r-strategist and K-strategist,respectively. The average photosynthetic rate, light compensation point, light saturation point, conductance and dark respiration rate of Psychotria rubra and Rhodomytus tomentosa were 5.9±1.6 and 11.9±0.4μmol CO2·m-2·s-1,0.005 and 0.012m mol·m-2·s-1,0.04 and 0.39,0. 053±0.037 μmol CO2·m-2·S-1 and 0.101±0.013mol·m-2·s-1 ,0.42±0.01 and 0.16±0.15μmolCO2 ·m-2·s-1, respectively. The morphological difference and plant physiological characters of the shrubs were closely related with their habitat.