The increase in UV-B radiation and airborne SO2 has become a serious environmental issue. In this paper the photosynthetic responses of 20 species of common tropical and subtropical greening trees to supplementary UV-B radiation and/or SO2 (simulated by sulfite solution) were studied. Trees were grown under natural conditions in the South China Botanic Garden. The relative resistances of these trees were estimated through the photosynthesis and chlorophyll fluorescence characteristics. Leaves were collected from the canopy of the 20 species and treated with UV-B radiation, NaHCO3 and UV-B+NaHCO3 for 72 h in the laboratory. Photosynthetic O2 evolution rate of these isolated leaves was then measured by leaf disc oxygen electrode system (Hansatech, King’s Lynn, UK), and their fluorescence emission (Fv/Fm) was tested using a PAM-Fluorometer (Walz, Effeltrich, Germany). Results showed that these plants can be classified into three types: high resistance, medium resistance and sensitive according to their resistant abilities to supplementary UV-B and/or SO2. They further showed that the UV-B radiation damage to the trees could be enhanced by treatment with SO2. The inhibition induced from a single stress factor, SO2 or UV-B, had a positive relationship with that from combined factors, UV-B+NaHCO3, in these tested trees. The response of chlorophyll fluorescence characteristics of these trees to environmental stress and applications of this technique for studying forest ecology, environmental physiology and stress physiology were also discussed.

The damage toLemna minor cells induced by Hg2+ was studied in this article. Most damage occurred to DNA primary structure and changes in antioxidant enzyme activities were investigated by using RAPD and DNA ladder methods. The results showed that obvious damage to DNA was found in the process of apoptosis induced by 5-10 mg·L-1 Hg2+, and 20 mg·L-1 Hg2+ had already caused necrotic injury. The RAPD method was the more sensitive of the two methods, and so could be considered as an important method for monitoring apoptosis. The results also indicated that reactive oxygen species (ROS) and antioxidant enzymes are involved in the process of apoptosis. The activities of antioxidant enzymes could be stimulated to eliminate active oxygen by exposing the Lemna minor to low Hg2+ concentration; the cells declined rapidly when ROS were unable to be eliminated effectively.

In the process of changing global climate, the increased carbon dioxide concentration and stimulated temperature are main focus. Carbon dioxide concentration and temperature are two key factors which can affect the growth and development of woody plants. At present, a lot of research has been carried out on the specific responses of woody plants to increased carbon dioxide concentration or stimulated temperature. At the same time, reviews of this research were publicized widely. However, reviews on the responses of woody plants to the interaction between carbon dioxide concentration and temperature were limited. In order to give some advice of use to the forestry industry, this paper reviewed how different woody plants responded to the interactions between carbon dioxide concentration and temperature. Increasing carbon dioxide concentration and temperature significantly affected photosynthesis, respiration, growth and development, biomass, and productivity. Moreover, the interactions between carbon dioxide concentration and temperature have significant effects on woody plants growth and development. In the process of photosynthesis, the main substrate was Rubp and Rubisco catalyze carboxylation and oxidization. Oxidization produces respiration consumption and carboxylation develops carbon fixation. Different plants responded to the interactions differently and individuals of the same species with different provenance did not have the same responses. At the same time, because of differences in photosynthesis of C4 and C3 plants, the exploration of the effects of interactions on C4 plants has a special significance.  Most studies showed that the interactions did stimulate photosynthesis; however, the effects on C4 plants were less than those on C3 plants. The ambiguous conclusions depend on the uncertainty in response mechanisms and different materials and treatments. Another interesting aspect was that under temperature and nutrient extremity, the physiological and chemical processes were influenced and the woody plants’ responses changed a little. Under high temperature, the decrease in percent carbohydrates thus limited respiration and growth. More photosynthetic products with increased carbon dioxide concentration stimulated respiration responses to increased temperature. However, a difference does exist between long-term and short-term respiration. Individual plant development and phenology can describe plant structural and functional changes in growth, maturity and senescence processes. The unequivocal results resulted from the limited methods and lack of sophisticated analysis. Further work is needed to be done. Increased carbon dioxide concentration can promote carboxylation and thus increase carbon fixation, biomass and productivity. Increasing temperature can have similar effects. The interactions between carbon dioxide concentration and temperature can promote the biomass increases and productivity. At the same time, the responses were specific.  Therefore, we suggest for future research and study: 1) strengthen the responses of photosynthesis to the interactions, including mechanisms and responses; 2) strengthen the study on the responses of woody plants to extreme temperature; 3) strengthen the individual development and phenology responses to the interactions and 4) pay more attention to woody plant responses to interactions at the ecosystem level.

Air pollution is a major environmental problem in cities. Much progress have been achieved in air monitoring and quality assessment at regional and national level based on emission inventories and measurements of ambient air concentrations taken by physical and chemical methods. The results of ambient air measurements make it possible to decide whether or not to limit the emission of certain pollutants. However, they do not permit direct conclusions on the effects of the measured pollutant concentrations on living organisms. The purpose of this study is to test the sensitivity of 30 2-3 year-old garden species transplanted into pots and exposed to differently polluted sites for 4 months during the growing season. Measurements on gas exchange parameters were made by using LCA-4 photosynthesis system. Based on these measurements, assessments of possible effects of air pollution on plants and their tolerance were also made. Monitoring data showed that the heavy traffic area received a much higher concentration of NOx than the industrial site, and both sites had high concentrations of SO2. The sites can be categorized from heavy to less pollution level in the order of heavy traffic area, industrial area, and relatively clean area by using an integrated pollution index. The Pn, E,gs differed among species and decreased for most species under polluted area. The Pn and E were closely linearly correlated with the gs under the relative clean site and polluted site，suggesting that most species had the ability to adapt to the pollution stress by adjusting stomatal operation. The evidence that the correlation of the Pn and E with g s had been weakened under the pollution stress also showed the unparallel nature and complexity in changes of Pn, E and gs. Based on the change in Pn, plants might be ranked as follows by their sensibility to air pollution： species that exhibited high sensitivity included Michelia maudiae, Allemanda schottii, Crateva trifoliate, Magnolia delavayi, Bischoffia jacanica, Lysidice rhodostegia, Michelia macclurei and Hibiscus rosa-sinensis. Species showing moderate sensitivity were Tristania confera, Bombax ceiba, Schefflera arboricola, Elaeocarpus hainanensis, Manglietia hainanensis, Elaeocarpus apiculatus, Swietenia mahagoni, Sterculia lanceolata, Fagraea ceilanica, Manifera persiciformis and Ficus macrocarpa, and those showing low sensitivity included Pittosporum tobira, Ficus altissima, Ficus microcarpa, Kigelia africana, Ficus benjamina, Mimusops elengi, Ormosia pinnata, Ficus elastica, Acmena accuminatissima, Nerium indicum and Ilex rotunda.

Net photosynthetic rates (Pn), transpiration rates (E) and water se efficiencies (WUE) of 97 species among different habitats of Hunshandak Sand Area in Inner Mongolia were investigated. The results showed that some species such as Salsola collina, Setaria viridis, Agriophyllum pungens, Artemisia ordosica, Caragana microphylla and some other species which possess the C4 photosynthe

tic pathway or with nitrogen fixation ability had higher net photosynthesis rates > 30 μmol

CO2·m-2·s-1), while most of the species which possess the C3 photosyntheti

c pathway or lacked nitrogen fixation ability had lower photosynthesis rates (1.

29-10 μmol CO2·m-2·s-1). Species with transpiration rates between 2-10 mmol

H2O·CO2·m-2·s-1 comprised 71% of the species studied. The selected species which

have high photosynthetic capability should be preferentially used in rehabilitating

degraded grassland. Of the plants measured, C4 species are mainly distributed on

fixed sand dunes. The differences between C4 and C3 species decreased graduall

y with increasing soil moisture. Of the habitats studied, the values of both Pn

and E of grasses and shrubs were found to be in the order of wetland > lowla

nd > fixed dunes, whereas those of trees were in the order of fixed dune > lowland.

The order of WU was opposite to those of Pn and E. Gas exchange traits

of three growth forms growing in different habitats were widely different.

In fixed dunes, Pn of three growth forms were not greatly different,

while the highest E and WUE were found in grasses and trees, respectively.

Light utilization efficiency (LUE) directly influences the distribution

of energy and rate of photosynthesis in all layers of vegetation. LUE is very valuable

in deciding the integrated limits of environment to photosynthesis and plant growth

allocation of aboveground, and is an important index in weighing functions of system.

In China, the studies on LUE focus usually on crops, rarely on natural vegetations,

and mostly calculate mean LUE over the country. The studies on LUE of natural

vegetations in some regions are limited to one or two types of vegetation. Thus,

it is very difficult to reflect the total conditions of all vegetations over these

regions in different periods.

In the study, leaf area index (LAI) that greatly influences LUE of vegetation was

received from remote sensing images. The ecosystem productivity process model at

landscape scale (EPPML) that described carbon cycle and water cycle of system was

built by computer program (Visual C++), and seasonal dynamics and spatial

distributions of total solar radiation, net primary productivity (NPP) and LUE

in Changbai Mountain Nature Reserve were simulated. Geographical Information

System (GIS) was used to process, analyze and display spatial data. Thus, we could

extend and convert the studies on physiological ecology of plants from small scale

to a larger scale. EPPML uses the principles of Century, BIOM_BGC, Forest-BGC and

BEPS for quantifying the biophysical processes governing ecosystem productivity,

but the original model is modified to better represent Changbai Mountain region.

A numerical scheme is developed to integrate different data types: remote sensing

data (TM), gridded vegetation, soil and topographic maps at 30-m resolution in

Albers projection; daily meteorological data in Changbai Mountain station in 1995,

including precipitation, maximal temperature, minimal temperature, mean

temperature, solar zenith angle at noon, air pressure and wind speed; diameter

data from field measurement and national forest survey; data from literatures for

inputs to EPPML and validation of EPPML. Vegetation index is derived from remote

sensing data for estimating daily LAI and biomass at landscape scale. The

information about vegetation type, soil type, elevation, slope and aspect can be

derived from vegetation, soil and topographic maps. EPPML uses the biochemical

model for photosynthesis of leaves developed by Farquhar et al.(1980) to

simulate the rate of photosynthesis. NPP is the organic matter eliminating

respiration from gross photosynthetic productivity (GPP). In addition, EPPML uses

the sub-module MT-Clim in Forest-BGC to calculate total solar radiation. In EPPML,

the spatial scale is 30 m and temporal scale is daily and yearly. The whole

simulating process is easily understood and realized. EPPML is run and values are

cumulated in each pixel. The major outputs include seasonal dynamics and spatial

distributions of some carbon cycle and water cycle variables including NPP and

LUE. The results indicated that the seasonal variation of LUE of vegetations in

Changbai Mountain was similar to that of NPP with peak value in July (2.9%). The

LUE in spring, summer, autumn and winter averaged 0.551%, 2.680%, 0.551% and 0.047%

respectively. The annual LUE of all vegetation types averaged 1.075%, varying from

-3.272% to 3.556%. The maximal annual LUE appeared in mixed broad-leaved and korean

pine forests (1.653%), minimum in alpine grasses (0.146%), others being Changbai

larch forest (1.227%), spruce-fir forest (1.019%), meadow (0.983%), broad-leaved

forest (0.728%), shrub (0.478%), alpine tundra (0.442%) and Betula ermanii forest

(0.298%). Though the LUE of mixed broad-leaved and korean pine forests were very

high, it still had great increasing potential. 

In conclusion, EPPML could well and truly simulate NPP and total solar radiation

of main vegetations at landscape scale in Changbai Mountain Nature Reserve.

Therefore, it could well reflect the seasonal dynamic and spatial distribution

of LUE. The LUE values simulated from EPPML were mostly in the range of those

of Chinese forests. It indicates that we can simulate LUE of natural vegetation

at the middle and large scale by model. The study supplies a gap in developing

dynamic model for LUE of natural vegetation at the middle and large scale in

China. However, because of lack of field survey data about LUE of different

vegetation types, only limited validations were carried out in the study.

Most rangelands in northern China are water-limited ecosystems. Even small

changes in precipitation amount or season can affect the biological components that

maintain nutrient, water and energy movement within and through these ecosystems.

Inner Mongolia steppe is generally semi-arid with most of the precipitation coming

during the summer from June to August. Land-management practices, such as livestock

grazing, are affecting ecosystem structure and function and these activities may

accelerate impacts of climate changes. Grazing-related changes to ecosystems become

more pronounced as humans shift from nomadic or unrestricted practices of livestock

management to practices that focus on human settlement. At the scale of a management

unit (e.g., watershed, allotment or paddock), precipitation amounts do not always

correlate positively with vegetation productivity. Nutrient availability may

strongly influence botanical composition and productivity. In general, spring and

summer precipitation favors herbaceous vegetation that is more efficient in

extracting water and will favor plants with C4 (warm-season) vs. C3 (cool-season)

photosynthesis. The northern China steppes have few C4 plants. Little experimental

work is being done in the field to examine the ecological impacts of climate change

and grazing and their interactions on C4 plants in this region.

Cleistogenes squarrosa is a C4 plant. It is a short, perennial bunchgrass

with drought tolerance, and tends to occupy medium degradation grassland in

Inner Mongolia steppe. Therefore, it is a good indicator to study effect of

climate change and grazing on C4 plants. In order to understand the responses

of Cleistogenes squarrosa populations and ecological strategies to climate

change and grazing, we monitored the data of climate (precipitation and

temperature),C. squarrosa population and its community for 18 years under

non-grazing conditions. The grazing (free grazing outside of fence) and

non-grazing (fenced) experiment was conducted for 6 years. The nutrient

efficiency ratios of the main herbages were evaluated in this study.

The experiment was conducted in the Leymus chinensis grassland of the Inner

Mongolia Grassland Ecosystem Research Station located at 43°26′-44°08′ N, 116

°04′-117°05′ E with elevation about 1 000 m above sea level. The results showed

that aboveground biomass and its proportion in the community increased with annual

mean temperature, and the regression equation between its aboveground biomass and

mean temperature (t) and total rainfall (r) from April to August was: y=-12.451

1+0.018 7r+0.060 1t2 (R2=0.533，p=0.003). Generally, grazing significantly

reduced plant height and aboveground biomass per bunchgrass, whereas its coverage,

density and total aboveground biomass per square meter increased under grazing.

Its nutrient efficiency ratios, such as N and S, were higher compared with other

dominant species, such as L. chinensis. 100 g C produced required 3.17 g N and

0.31 g S for C. squarrosa, while L. chinensis population requires 4.24

g N and 0.41 g S under grazing. The high nutrient efficiency ratios maybe benefit

C. squarrosa populations under competition with other species in the infertile

soil.

In this study, we investigated resources allocation in intra-inflorescence

of Ligularia virgaurea in different habitats and population densities based

on the characters of reproductive allocation that have been studied. The material

we studied was collected from Nima (101°53′ E, 35°58′ N, altitude 3 500 m) in

Maqu county, Gansu province, in the first turn of Yellow River, North-East region

of Tibetan Plateau. This region belongs to the alpine meadow rangeland type.

The plot contained habitats of different degrees of degradation. L. virgaurea is

a perennial herb of Compositae. The flowering phase lasts from July to August,

with blooming starting at the top of the raceme. The frutescence is in September,

about 10 days. It is the dominant weed in alpine meadow now because of the toxic

milky material, selective predation and over-grazing by livestock. The aim of our

research is to reveal the reproductive strategies of L. virgaurea at the

level of the inflorescence. 

During the latter period of seed maturation of L. virgaurea in September 2000,

we sampled randomly from three habitats, floodland, hillside and lowland, and two

populations of different density in each habitat. There were 10-16 quadrates per

plot, 1-3 seed producing ramets per quadrate were sampled, and brought to the

laboratory. The vegetative and reproductive structures were separated, heated 24

hours in 75 ℃ drying oven, and weighed using an electronic balance (g/10 000).

The ramet, raceme, capitula of different positions on the raceme, and the number

of capitula per raceme were measured. The data were analyzed by ANOVA and linear

regression. The measures are: the size of ramet and raceme represented by their

biomass; mean weights of capitula (the ratio of biomass and numbers of capitula

per raceme); the available capitula of top, middle and bottom represents

separately the top, the position of 1/2 RI and the bottom; the resource allocation

of capitula at different position means the biomass percent of capitula /raceme;

available capitulum means it could produce seeds, unavailable capitulum means it

did not.The results show: 1) different habitats or population densities differ

in resource investment of raceme and capitula of different positions within raceme,

and it exhibits some trends as follows: floodland > hillside > lowland, uncovered

land > covered land, and low population density > high population density; 2)

although most of the correlation coefficients are small, there are negative

correlations between the characteristics of racemes (such as the size of raceme

and capitula, the number and mean weight of capitulum) and population densities,

and no correlations between the size of capitula of different positions within

the raceme and population densities; 3) there is a position-based effect within

inflorescences, such as the significant decrease in the resource investment

between the early-formed or top capitulum of the raceme and later-formed bottom

or middle capitula of the raceme; 4) there are significant negative correlations

between the size of the raceme and the allocation of capitula at different

positions of the raceme.

Germination tests of two water regimes were used to evaluate traits, mainly

community structure, of the soil seed bank of Honghu wetland withdrawn from

long-term rice culture.

One-way ANOVA was employed by means of diversity, richness and evenness

indices, and seed density. To evaluate the role of seed bank in restoration of wetland

communities, a soil core was sampled in June 2000, December 2000, March 2001 and

May 2001. Furthermore, the delamination of the seed bank was conducted by comparing

seed densities at different depths in the soil in the March 2001 sample. The results

showed that: 1) seed density in different seasons varied a lot, from 2.90×10 4

ind.·m-2 in June 2000 to 2.61×10 5 ind.·m-2 in December 2000. The size of the seed

bank in Honghu wetland is the largest among all the types of seed banks. The seed

bank belonged to the IV type of the Thompson and Grime model of soil seed banks of

different habitats. 2) For the community of the soil seed bank of Honghu wetland,

Simpson and Shannon-Wiener diversity indices, and Shannon evenness index were

maximal in June 2000, and minimal in December 2000. 3) The number of species had

no significant difference between soil depths of 0-5 cm and 5-10 cm. The seed density

in the upper layer accounted for 78% of the total seed number of the two layers,

which indicated that it was creditable to study only the upper level (0-5 cm) in

this kind of research. 4) Seed germination was affected by water depths in both number

of species and number of individuals of seedlings. 5) Degrees of similarity between

species composition of soil seed banks and that of the wetland vegetation during

December, March and May were 33.3%, 20.8% and 15.4%, respectively. They were

considerably high compared to those of some other types of habitats. 6) Seeds of

typical wetland species were scarce in all sampling periods, suggesting that in order

to restore the vegetation of the disturbed wetland more quickly, external seed banks

with abundant wetland species need to be introduced rather than only depending on

the original ones.

In order to investigate the status of arbuscular mycorrhizae (AM) in

tropical dipterocarpaceae forest, rhizospheric soil with roots of seventeen species

of dipterocarpaceae plants grown in both native forests and plantations in tropical

region Xishuangbanna, Yunnan Province, were sampled to determine their mycorrhizal

colonization, spore density, isolation frequency, relative abundance and species

richness of AM fungi. The mycorrhizal colonization rate of host plants were measured

under a BX50 Olympus Microscope with Automatic Photo Micrographic System (320-640

×) after staining with 0.5% acid fuchsin. Spores of AM fungi in aliquots (20 ml)

of each soil were isolated by wet-sieving decanting and cane sugar centrifugal method,

hich were used to identify according to the newest taxonomic system described by

Morton and Redecker (2001). Species richness was measured as the number of species

compared with the number of individuals in the community. Results showed that most

roots collected were colonized by AM fungi, typical arbuscules and vesicles were

formed with various colonization rates (up to 40%, grade VIII), and 0-1.86 vesicles

per mm root length. Species richness on Parashorea chinensis was the highest

(4.31),while Shorea assamica showed the lowest (1.63). Hopea mollissima gave

the maximum spore density (7.76), Vatica astrotricha the minimal (3.09).

Thirty_two AM fungal species belonging to the genera Acaulospora, Glomus,

Paraglomus, Achaeospora and Scutellospora were identified. The frequencies

and relative abundances of AM fungi varied. Acaulospora and Glomus were

likely the dominant proportion in the rhizospheric soil of dipterocarpus plants in

the tropical region. It was suggested that most dipterocarpus plants can form typical

AM and there was high species diversity of AM fungi in tropical dipterocarpaceae

forest. The functional role of these AM fungi in the physiology of dipterocarpus

plants needs further research.

The effects of Amomum villosum cultivation on biodiversity in Xishuangbanna

tropical rainforest attract much attention. This research, which lasted two years,

was carried out to study ecological restoration after removal of Amomum villosum

in the rainforest of Xishuangbanna. The results were as follows: 1) the number of

plants in the rainforest increased significantly, compared with the number in

primary rainforest, which has the same type of vegetation but has never been planted

with Amomum villosum. However, there are no significant differences between the two

kinds of rainforests as to the species richness, plant diversity and evenness, which have increased prominently in both kinds of rainforests. The flora develops to that of tropical rainforest. The dominant species is not prominent, but the number of herbs and ferns increases significantly. 2) in the wet season, the seedlings grow faster in removed Amomum villosum rainforests than in primary rainforests, but there is no difference in dry season growth. The biomass of seedlings reached (636.1 ±43.4) g·m-2 after two years, exceeding that of primary rainforest, especially due to the fast growing herbs and ferns; 3) water content of soil was improved, as was the water capacity, with no difference to that of primary rainforests. The organic matter content of deep soil increased significantly, while the available phosphorus content needed long-time vegetation restoration to increase. Much of the available phosphorus of the surface was lost by the stream-water of rain. A new pattern of Amomum villosum rotation in tropical forests was recommended, which would be a good approach to the minority of mountain area in Xishuangbanna, because it could partly harmonize the contradiction between conservation and development.

Shorea chinensis forest of Xishuangbanna (21°29′ N, 101°34′ E) is a rainforest type of tropical rainforest in South-east Asia entering into Xishuangbanna, which is significant in connecting with the flora of tropical rainforests in South_east Asia and elucidating characteristics of tropical rainforest in Xishuangbanna. In southern Mengla county, Xishuangbanna, Shorea chinensis forest grows on the mountain in altitude 700-900 m, the soil is latosol, annual mean temperature is 21.1 ℃, and annual mean precipitation is 1 500-1 600 mm. In order to know the soil nutrient content, organic matter, total N, P, K, available N, P, K and their seasonal changes under Shorea chinensis forest in Xishuangbanna, we took soil samples in the top soil (0-10 cm) and under the top soil (10-25 cm) from 47 plots among 10 different patches of Shorea chinensis forest in May and November, 1999. 23 plots were located in valleys and 24 plots in lower mountainous areas. The results showed there are obvious difference in the soil nutrient content in different soil layers, in different seasons and in different areas: 1) in different soil layers, nutrients were rich in the top soil (0-10 cm) and poor under 10 cm depth. The content of nutrients under 10cm depth was about 56%-75% of the nutrients in top soil; available P content was only 0.039% of the nutrients in top soil. 2) Soil nutrient content changes with seasons; nutrients were higher before the rainy season than after the rainy season. The content of organic matter, total N, total P and total K in top soil after rainy season was 94%, 90%, 94% and 82% of the content before rainy season respectively, and the content of available N and available K in top soil after rainy season was 89%, 92% of the content before rainy season. Available P decreased sharply in top soil after rainy season; the content of available P in top soil after the rainy season was only 0.078% of the content before the rainy season. The change in nutrient content under top soil after rainy season was the same as the change in nutrient content in top soil. 3) Concerning soil nutrient content in different area, nutrients were also higher in valleys than in lower mountainous areas. The content of organic matter, total N, total P and total K in top soil in lower mountainous area were 79%, 80%, 84% and 83% of the content in valley respectively, while the content of available N, available P and available K were also lower in top soil in lower mountainous area than in valleys. From the above results, we can conclude that seasonal changes significantly affected total K and available P, but only slightly affected total P, available K and organic matter, and affected N content more in lower mountainous areas than in valleys. In the rainy season P content in soil is very poor. The environment and plant growth rhythm of Shorea chinensis forest have some effects on the soil nutrient content.

Both interspecific association and interspecific segregation can be used to study the spatial affinity between different species. They are connected but different. Interspecific association is more related to habitat, while interspecific segregation

The upper reaches of Bailong River, a significant branch of the Yangtze River, is one of the important regions in the Yangtze River Natural Forest Protection Project. Based on the survey and the data from 36 plots, characteristics of species diversity of plant communities in the upper reaches of Bailong River were discussed in this paper. The study showed that richness index varied as follows: tree layershrub layer>tree layer; b) moss-A. fargesii community: tree layer > shrub layer> herb layer; and c) other communities: shrub layer > herb layer> tree layer. Diversity indices in tree layer were lower than that in herb layer and in shrub layer. While the diversity indices between herb layer and shrub layer varied with shade density, i.e. greater the shade density, lower the diversity indices in herb layer. When shade density of stand was about 45%, diversity index in herb layer were almost equal to that in shrub layer; when shade density of stand was about 30%, diversity index in shrub layer were lower than that in herb layer; when shade density of stand was above 55%, diversity indices in shrub layer were higher than that in herb layer. General richness index, evenness indices and species diversity of Pinus tabulaeformis community distributed on the sunny slope were higher than that of the grass-Picea asperata community growing on the shady slope along the same elevation zone (2 500-2 700 m). The study detected that general species diversity and general evenness indices of different plant communities decreased gradually from broadleaf mixed community dominated by Quercus liaotungensis at 2 400 m elevation, to grasses-Picea asperata community at 2 600 m elevation, to bamboo　(Sinarundinaria nitida)-A. fargesii community at 2 800 m elevation, to moss-A. fargesii community at 3 000 m elevation, to R. fastigiatum - A. fargesii community at 3 200 m elevation zone, and then progressively increased in R. fastigiatum shrubs from 3 400 m, with altitudinal increase. The study also indicated that species diversity and evenness index gradually increased from shrubs stage dominated by Spiraea alpina and Sibiraea angustata to broadleaf mixed forest stage dominated by Betula albo-sinensis, to broadleaf and needleleaf mixed forest stage dom inated by B. albo-sinensis and Picea purpurea, and then decreased at the needleleaf community stage dominated by P. purpurea in the natural succession series of P. purpurea community after artificial logging.

Increasing quadrat area or quadrat number for the study of interspecific associations in plant communities aims at adding overall sample area. The ovell sample area that was chosen by many scholars on studying interspecific association were between 3 000 m2 and 40 000 m2, and the quadrat areas were 25 m2、100 m2 and 400 m2. The overall sample areas were limited in some cases (e.g endangered species or monodominant communities) because the distribution areas are often limited. Therefore overall sample area for studying interspecific association could not be determined arbitrarily. Under condition of fixed overall sample areas, the sampling strategy needs to be explored.The typical sampling area of Quercus liaotungensis forest in Dongling Mountain in Beijing was chosen. The transect that its overall area was 1 250 m2 （5 m ×250 m） was designed. Three quadrats that its overall area were 1 200 m2 (3 ×20 m×20 m) was chosen for the study. The transect was segmented equably according to long border, the area summation of all quadrats was equal to that of the overall transect. Because three quadrats were discontinuous, every one was divided according to definite border or area, and the area summation of all divided quadrats was equal to the overall area of three quadrats. The sample area was divided into some grids. The coordinate and quantity of every individual was measured in all grids.Under conditions of given sample area, some interrelations of quadrat number and area and affects of interspecific association were discussed based on quadrat and transect design. The results showed that positive and negative interspecific association ratio, species average appearance ratio, total multi-species χ 2-test, χ2-test and significant ratio of species pairs and variation range of interspeific association coefficient could be adopted and applied synthetically to choose optimal quadrat number and area. Under condition of 1 200 m2 sample area, regularity of those parameters was showed obviously on transect design for sampling technique of Quercus liaotungensis forest, and the choice of 50 quadrats and 25　m2 for each quadret were optimal quadrat number and area for analysis of interspecific association in this area. The quadrat design was revealed some shortages, and total sample area must be added for gained optimal quadrat number and area. Based on study results of interspecific association analysis according to optimal quadrat number, effects of transect design were better then that of quadrat design. Therefore, under condition of limited total sample area, transect design was better choice for analysis of interspecific association.

In Beijing Dongling Mountainous area, the coppiced populations of Liaodong oak (Quercus wutaishanicaMayr) usually appear as an associated tree species of the Chinese pine (Pinus tabulaeformis Carr.) artificial forest. In some places the artificial pine forest is replaced by mixed crops of Chinese pine and Liaodong oak, or the oak takes the place of the pine as the dominant species in some specific habitats along the ridges and the upper slopes of hills. In order to compare and understand the recruitment and establishment of Liaodong oak seedlings under Chinese pine artificial forest as well as the natural regeneration mechanism of the oak forest, an artificial forest of Chinese pine with Liaodong oak as an associated species in Beijing Dongling Mountainous area was selected, and comparative experiments on the recruitment and establishment of seedlings were conducted by sowing the acorns of Liaodong oak about 2 cm below the floor surface in two habitats, under the canopies and along the boundaries of the artificial forest. The results showed that in the mast year of the oak, though the difference of loss of the acorns planted in these two habitats was not significant, yet there were highly significant differences in the recruitment and establishment of seedlings. Since activities of small forest animals, rodents in particular, have both positive and negative effects on oak forest regeneration, through acorn consumption and germination facilitation, close attention was paid to the phenomenon of cotyledon loss of acorns and the consequences of the loss. As the acorns germinated as soon as they fell from the mother tree in autumn, before the seedlings sprouted their caudices, the taproots would have grown 10_20 cm long and formed primary root systems, implying that certain amount of the nutrition stored in the cotyledons had been transported to the roots. From the field experiments it was found that the acorn cotyledons were consumed by the predator in three ways during the early seedling stage: 1) the seedlings lost their cotyledons without harming any other parts, which often occurred along the forest boundaries, accounting for 29.69% of the germinated acorns; 2) the whole seedlings were drawn out of the soil, which almost always happened under the forest canopies, accounting for 62.43%; 3) the stems of seedlings were broken at the bases where the cotyledons are connected, occurring 50.88% along the boundaries, more frequently than under the forest canopies where only 8.41% of germinated acorns occurred. Only the latter two ways caused the seedlings to die, while cotyledon loss after seedling emergence from the soil had little negative effects on the growth and survival of the seedlings. These phenomena might result from different soils between these two habitats; soil along the boundaries has little humus and is much harder and drier than that of the forest floor under the canopy. Also, the taproots were much longer along the boundaries. So when rodents predate the seedlings along the boundaries, it would be easier to split the cotyledons from the seedlings instead of pulling out the whole root from the soil. At the end of the first living period, the survival rate of the seedlings along the boundaries was close to 20%, the average height of the stems reached 7.94 cm, average buds were 11.24 per seedling, and the average dry weight of leaves was 81.14 mg per seedling. Moreover, almost all of the surviving seedlings along the boundaries lost their cotyledons. The survival rate under forest canopies was less than 2%, the average height of stems reached 4.74 cm, average buds were 7.52 per seedling, and the dry weight of leaves was only 42.27 mg per seedling, but the surviving seedlings under canopy did not lose their cotyledons. The above results showed that the habitats along the forest boundaries and similar areas would be more beneficial to the recruitment and establishment of oak seedlings.

The study on species abundance pattern started in 1930’s, which is the origination of population and community ecologies. The species abundance pattern analysis can be conducted at two levels. 1) At the beginning stage, it was focused on the community level, which seeked to provide a common global pattern among different communities. The often-used methods include geometric series, log-series, log-normal and broken stick models, and each model represents different ecological process. 2) Nowadays, it highlights the species level, which focused on regional distribution of species and its ecological mechanisms. There are three kinds of species distribution-abundance relationships, that is positive, negative and no correlation. Species tend to be widely spread in region with high local abundance whilst restrictedly distributed with low local abundance. The regional distribution of species abundance is unimodal by niche model prediction, and some “hot spots" are often emerged. It is bimodal by meta-population model prediction, which may be determined by the properties of environmental resources, species niches and dispersal processes. 3) The dynamics of species abundance pattern is similar to its spatial variation in that it represents the temporal heterogeneity of those underlying ecological processes. 4) The scale variation of species abundance pattern is often self-similar though it does not always exist, because biodiversity is normally determined by different processes at different scales, and they are not necessarily self-similar all the time. 5) Abundance (rarity) is the basis for species preservation, while species abundance models could provide indication to the variation of ecological or perturbation processes on community structure. The research of species abundance pattern is still insufficient in mechanism explanation,modeling techniques, and conservation applications, and the development of relevant researches would advance the understanding of distribution mechanisms and the effective preservation of biological diversity in the future.

Ecology and genetics initially overlapped in the concept of population. Preliminary literature demography showed that studies on the formation and maintenance of population genetic structure are becoming mainstream approaches at the present time. With the rapid development of genomics, cloning ecologically important genes and comparing their subtle expression patterns has become a new field of study. By analyzing characteristics of related cases, it is proposed that ecology will provide important contributions towards the solution of questions arising from gene_oriented studies.