Vegetation greenup is closely related to seasonal dynamics of the lower atmosphere and, therefore, is an important variable influencing the feedback mechanisms of global climate variation to terrestrial ecosystem. Detecting vegetation greenup using remotely sensed data at regional or global scale has become an advanced topic in geography and ecology. However, current methods of remote sensing-based vegetation greenup detection are short of valid comparison and do not have a consistent results.

This paper utilizes computer simulation technique to explore the seasonal dynamics of typical steppe grassland in Xilingole, Inner Mongolia, using NOAA/AVHRR NDVI data from 1982 to 1999. Firstly, Savitzky-Golay filter algorithm is used to smooth NOAA/AVHRR time-series images from 1982 to 1999. Secondly, the curve-fitting technique is applied to phenological phase (turning green date and wilting date) in each year and to the average phenological phase and length of growing season from 1982 to 1999 for the typical steppe grassland in Xilingole, Inner Mongolia. Finally, the trend of change in phenological phase is analyzed for the typical steppe grassland in Xilingole during the 18 years.

The results indicate that 1) the turning green date in 1982, 1986 and 1992 was placed in normal level, but that in 1985, 1988, 1989 and 1991 was advanced in most areas. The wilting date in 1984, 1990 and 1993 was also placed in normal level and the wilting date in most years was mainly from the last ten-day of September to the first ten-day of October (290-310 days). 2) Turning green date of all typical steppe grassland showed large variability. The wilting date of southwestern area was earlier than that of central and northwestern area, but the length of growing season didn't show the same pattern of change. The length of growing season in southwestern area was the shortest and that in central area was the longest. 3) From 1982 to 1999, the phenological phase and length of growing season of the turning green date and the wilting date of typical steppe grassland showed the characteristics of advancing or delaying in different areas. The delay time for turning green date of typical steppe grassland in most areas mainly focused on 10-20 days, and the advance time for turning green date was less than 10 days. The advancing trend in wilting date was the greatest in northwestern area in Xilingole. The length of growing season showed a shortening trend and the shortening date was less than 10 days. Increase in the length of growing season was little in Xilingole, and it mostly focused on 0-10 days. 4)The research on phenology of the typical steppe grassland in Xilingole indicated that the turning green date of the typical steppe grassland advanced less than 10 days, the wilting date postponed for about 14±5 days, and the length of growing season increased about 15±5 days. Lastly, the precision of phenology phase in Xilingole is evaluated by the observation data in the field.

The southern fringe of Kumtag Desert is a transition zone for vegetation from rangeland desert type in the Gobi in front of eastern Aerjingshan to wind-accumulation desert type. The diversity of plant species in 20 plots in this area was investigated by calculating the indices of species diversity, richness, evenness and dominance from important values. The results indicated that: 1) The distribution of desert plant community differs with various habitats and landforms. Sympegma regelii community is distributed in the Gobi in front of the mountain; Populus euphratica, Tamarix ramosissima, Glycyrrhiza inflata communities are distributed at the alluvial river course or lowland; Haloxylon ammodendron community is distributed in transitional region from Gobi to desert; and Ephedra przewalskii, Calligonum mongolicum and Haloxylon ammodendron communities are distributed on the sandy mountain with low elevation. 2) The structure and composition of desert plant community are simple, and the species diversity is low. Sympegma regelii community, a rangeland desert vegetation, has the highest Shannon-Winner species diversity indices (1.706); the communities of Haloxylon ammodendron and Ephedra przewalskii, which have obvious feature of desert vegetation, are in the middle in species diversity indices (0.875-0.890); the communities of Calligonum mongolicum, Populus euphratica,Tamarix ramosissima and Glycyrrhiza inflata, characterized by desert forest of which saline desert bushes and saline meadows are scattered in the communities, have lowest value of the species diversity indices (0.079-0.495). 3) The structure of desert plant community is dominated by the bush layer. The species diversity indices of bush layer (0.769-1.451) is much higher than that of herb layer (0.193-0.254), and the diversity in herb layer is strongly influenced by bush layer. 4) The species diversity of desert plant communities shows a gradient of change with respect to longitude, latitude and elevation. For example, rangeland plant Sympegma regelii, with a high level of diversity indices (1.706), is in transition to desert plants Haloxylon ammodendronn community (with a low level of diversity indices of 1.379) in a longitude gradient and to saline Tamarix ramosissima community (with a low level of diversity indices of 0.376) in a latitude gradient. Calligonum mongolicum community, with a low level of species diversity (0.819), is in transition to Ephedra przewalskii (with a low level of diversity indices of 0.890) and Haloxylon ammondendron community (with the diversity indices of 0.645) in an elevational gradient. The transition zone of desert plant communities generally has high level of species diversity and relatively low degree of ecological dominance.

The forest vegetation was investigated through 40 carefully designed sampling plots in Hungou, Zhongtiao Mountain. Within each plot, the main environmental factors, such as altitude, slope, aspect and soil depth, were measured using portable GPS instruments and field tools. Soil samples also were collected and analyzed in the laboratory for total N, organic matter content, and pH. Topographic relative moisture index (TRMI) and annual total solar radiation were calculated using a Digital Elevation Model (DEM) (scale 1:50 000). Community types were classified using TWINSPAN and the relationship between the distribution and abundance of species to environmental gradients was analyzed using CCA ordination. The 40 plots were divided into 7 plant formations: Pteroceltis tatarinowii, Koelreuteria paniculata, Quercus aliena, Quercus variabilis, Carpinus turczaninowii + Acer grosseri, Acer truncatum + Carpinus cordata, and Quercus liaotungensis. The floristic composition of the arboreal species in each community represented the characteristics of the different deciduous broad-leaved forests in the warm temperate zone of North China. The distribution pattern of the community types classified by TWINSPAN was coincident with the environmental gradients shown in the diagram of the first two CCA axes. The first CCA axis mainly expressed altitude and soil fertility, and the second axis had distinct relationships with soil pH, TRMI, and slope gradient. These results, in general, indicate that the spatial distribution of tree species in Hungou is mainly controlled by altitude, soil fertility, and biotope humidity, whereas soil depth, annual global radiation and slope aspect are secondary controls. Environmental and spatial variation accounted for 46.14% of the spatial distribution of tree species, of which environmental variation alone explained 30.79%, spatial variation was 8.48%, and the interaction of spatial and environmental variation was 6.87% of the variation. These results indicate that we measured the important environmental factors regulating species distribution patterns in this forest.

In recent years, the relationship of biodiversity to ecosystem stability, productivity and other ecosystem functions have been researched by using theoretical approaches, experimental investigations and observations in natural ecosystems,however, results have been controversial. For example, simple systems were more stable than complex systems in theoretical studies, higher productivity was observed in man-made ecosystems with poorer species composition than in natural ecosystems with more diverse assemblages, etc. The role of biodiversity in ecosystem functioning, such as its influence on sustainability, stability, and productivity, still is not understood. Because accelerated soil erosion in various ecosystems has caused a decrease in ecosystem primary productivity, a logical way to study the relationship between biodiversity and ecosystem function will be to study the relationship between plant species diversity and soil conservation. In addition, biodiversity is a product of evolutionary history and soil erosion is a key factor controlling the evolution of the modern environment on the surface of the Earth. A study on the relationships between biodiversity and soil erosion processes could help to understand the environmental evolution of Earth and predict the future changes.

To test this, fifteen 10 m×40 m standard runoff plots were established to measure surface runoff, soil erosion and total P leaching in different secondary communities of semi-humid evergreen broad-leaved forests that varied in composition, diversity and level of disturbance and soil erosion. The following five communities were studied: AEI (Ass.Elsholtzia fruticosa+Imperata cylindrical), APMO (Ass. Pinus yunnanensis+Myrsine africana+Oplismenus compsitus), APLO (Ass.Pinus yunnanensis+Lithocarpus dealbatus+Oplismenus compsitus), AEME (Ass. Eucalyptus smith+Myrsine africana+Eupatorium enophorum) and ACKV (Ass. Cyclobalanopsis glaucoides+Keteleeria evelyniana+Viola duelouxii) in central Yunnan Province of China (101°28'18″ E, 25°24'09″ N, 1 950-2 015 m). Tree density, the diameter of trees at breast height and the hygroscopic volume of plant leaves were determined in each plot in order to analyze the relationship between plant species diversity and ecosystem function related to soil conservation and community structure. The degraded AEI, APMO, APLO and ACKV communities were restored naturally and the AEME was restored using plantation trees ofE. smith and E. maidenii at AEI. The sequence of the successional phases were: 1) AEI AEME ACKV; 2) AEI APMO APLO ACKV. The slope degree, slope position and soil types of all plots were similar so that the results of these plots could be compared based on differences in diversity and composition only.

The results indicated that surface runoff, soil erosion and total P leaching decreased according to a power function as plant species diversity increased and the three year average was 960.20 m³·hm^-2·a^-1, 11.4 t·hm^-2·a^-1, 127.69 kg·hm^-2·a^-1 in the plot with the lowest species diversity and 75.55 m³·hm^-2·a^-1, 0.28 t·hm^-2·a^-1, 4.71 kg·hm^-2·a^-1 in the plot with the highest species diversity. The low species plot was 12, 50 and 25 times, respectively, higher than in the high species plot. Soil conservation was enhanced with increasing plant species diversity. The coefficient of variation of surface runoff, soil erosion and total P leaching also followed a power function decreasing with increasing plant species diversity from 2001 to 2003. The coefficient of variation was 287.6, 534.21, 315.47, respectively, in the lowest species diversity plot and 57.93, 187.94 and 59.2 in the highest species diversity plot, which was 4, 3 and 5 times greater in the lowest species plot. Enhanced soil conservation maintained greater stability with increased plant species diversity. Plant individual density increased linearly and the degree of closeness and basic coverage increased logarithmically with increasing plant species diversity. The hydrological function of the leaves of the plant communities was strongest in ACKV, poorest in APMO, and intermediate in the AEME, APLO and AEI communities. The hydrological function of the leaves was enhanced as the plant species diversity increased. There were obviously relationships between plant species diversity with rainfall interception, coverage, plant individual density and they were related to soil conservation once more in the five successional forest communities.

The complex relationships of plant species diversity with above-mentioned ecological processes indicated that plant species diversity was an important factor influencing the interception of rainfall reducing soil erosion and enhancing the stability of soil conservation, but the causal mechanism is not known. This experiment showed that plant species diversity promoted soil and nutrient conservation and was able to predict primary productivity of the ecosystem, and was thus a good way to study the relationship between biodiversity and ecosystem stability. Rainfall interception could be assessed easily using the hygroscopic volume of plant leaves of the plant community. Because there were strong correlations between plant species diversity and ecosystem functioning as related to soil conservation, the patterns of plant species diversity will show a certain level of predictability on the interactions of life systems with surface processes of the Earth.

The paper used TM and MODIS data to acquire ecosystem types and quality condition parameters. The process involved the following steps: 1) TM images were used to classify the land use/land cover of Huzhou; 2) A method was developed to decompose MODIS NDVI pixels (500 m×500 m) into the same resolution scale of classified TM image, and the observed weather data were combined to compute theNPP (Net primary productivity) of different ecosystems; 3) According to NPP and statistical data, ecological capital of different ecosystems was computed and applied into local socio-economic analysis.

The results showed that 1) the area of woodland, paddy field, shrub and bare land was about 87% of the total area of Huzhou on average in the past four years, and the proportion of grassland, water/wetland and dry land was about 13%. The area of woodland has been continuously decreasing. Bare land, shrub land, grassland and dry land have been steadily increasing, and the paddy land has been increasing in fluctuation. Water/wetland has been decreasing in fluctuation. 2) The average ecological capital of Huzhou in the past four years was 203.33 million RMB·a^-1, in which woodland made the main contribution at a rate of 73.22%. Ecological capital of different counties (districts) was ordered as: Anji County (91.76 million RMB·a^-1) > Changxing County (41.33 million RMB·a ^-1) > Wuxing District (29.31 million RMB·a ^-1) > Deqing County (28.27 million RMB·a ^-1) > Nanxun District (12.66 million RMB·a ^-1). 3) The percentages of ecological capital to GDP from 2001 to 2004 were ranked as Anji County >Changxing County>Deqing County>Municipal Districts, and such percentages showed a decreasing trend in general (only the percentage in Municipal Districts in 2002 was slightly higher than that in 2001, but it has generally been decreasing in the four years). Ecological capital per capita and per area during the four years were ranked as Anji County>Deqing County>Changxing County>Municipal Districts, and it showed a contrary trend of change compared to that ofGDP. That is, the regions with higher-speed economic development usually had relatively fewer ecological resources per capita and per area, and relatively low proportion of ecological capital in GDP, but the pollution level per capita and per area was relatively high. The regions with relatively lower-speed economic development were just contrary to that of the higher ones. All these observations reflected a pervasive problem of the current mode of economic development in Huzhou, that is, higher-speed development of economics has caused serious environmental problems.

Ground subsidence and its effects on environment have been the core content of ecological and environmental assessment in coal mining area. Although there are researches on these topics, the results and methods show some uncertainties and few involves forecast analysis. This paper forecasts the status of ground subsidence using ground subsidence forecasting mathematical model and classifies the heavy or slight influencing areas based on the degree of destructions of landscape. Based on remote sensing (RS) and geographical information system (GIS), this paper overlays the existing state map of the vegetation landscape and the map of the influenced areas. The influence of mining on environment is analyzed by comparison of the landscape patterns before and after ground subsidence in Dongda Mine of Jincheng, Shanxi Province. The results showed that: 1) in heavy influencing areas, there are some collapse or crack structure such as basin, saddle and wave etc. Soil erosion leads to obvious change in spatial distribution of soil nutrients. The environment near the collapse or crack areas worsens and becomes the source of nutrient loss. It is very difficult for the vegetation to recover in these areas. In nutrient-rich areas, the vegetation succession performs rapidly. Proper artificial disturbance can accelerate the recovery paces of the regional environment. 2) After the ground subsidence, the vegetation landscape is broken up and isolated severely. With the changes of landform and soil in space, the vegetation begins to perform a new round of succession. Because the degraded vegetation type, Bothrichloa is-chaemum-Thymus mongolicus community, will decrease, and the internal ecological function of the sub-dominance landscape is not quite affected, it is helpful to biodiversity and sub-dominance landscape succession. However, there is a linear relationship between the isolation of heavy influencing areas and the resulting patches, the obstacle for species to move from one patch to another in heavy influencing areas is obvious. Therefore, we should place more emphases on environmental conservation in coal mining area. On this basis, it is feasible to guide vegetation succession along the direction of Bothrichloa ischaemum-Thymus mongolicus community-Bothrichloa ischaemum-Themeda japonica community-bush-broad-leaved forest.

Climatic indices for initial flowering in Osmanthus fragrans were analyzed statistically by comparing the phenological data and climate data from 1956 to 1984 and from 1999 to 2003 in Dongshan County, Suzhou, Jiangsu Province, China. The results showed that the initial flowering date of O. fragrans was closely related to daily minimum temperature and relative humidity. For early flowering O. fragrans, initial flowering occurred 3 to 12 days later following a condition that the daily minimum temperature of 10-day-moving-average (DMTMA10)≤23.0 ℃ and the daily minimum temperature <22.0 ℃, or 12 days later following a condition that DMTMA10 stays between 23.0 and 25.5 ℃ and the daily average relative humidity (DARH)≥88% for 3 or more than 3 days. It would not get flowering if the DMTMA10>25.5 ℃. For late floweringO. fragrans, initial flowering occurred 4 to 12 days later following a condition that the daily minimum temperature of 9-day-moving-average (DMTMA9)≤20.0 ℃ and the daily minimum temperature <19.5 ℃, or 6 days later following a condition that DMTMA9 stays between 20.0 and 21.5 ℃ and the DARH≥88% for 3 or more than 3 days. It would not get flowering if the DMTMA9>21.5 ℃. The date of initial flowering of early floweringO. fragrans and that of late flowering O. fragrans were significantly correlated (r=0.443 8, n=34). The initial flowering date of late flowering O. fragrans is, on average, 15 days later than that of the early flowering O. fragrans. The initial flowering date of both types of O. fragrans during 1999 and 2003 was postponed 7-8 days compared with that during 1956 and 1984 in Dongshan County due to global climate warming.

Sladenia celastrifolia has a scattered distribution in Southwest China, especially in Yunnan Province. However, characteristics of many populations have been largely altered by increasing human activities. Using age-diameter relationships, we analyzed the age structure, the life table and the survival curves of two populations of this species, which have been affected by human disturbance to different degrees. In the heavily disturbed population, there were fewer young-aged individuals. The individuals of the age class Ⅰ account for only 12.7%, whereas those of the age class Ⅱ, Ⅲ, and Ⅳ together account for 80.3% of the total individuals of the population, indicating a declining population. In contrast, the age structure of the less disturbed population appeared to be stable with sufficient numbers of young-aged individuals. The life tables of the two populations were different: the death rates of the age class Ⅰ and Ⅱ were negative, indicating a shortage of young-aged individuals. The survival curves of both populations were characterized by high death rates of young-aged individuals, while the death rates of all age classes of the less disturbed population were stable. The age structure and dynamics of the two populations of this species are similar to those of some other endangered species in China, such as Liriodendron chinense and Cathaya argyrophylla. Although S. celastrifolia has not been regarded as an endangered species until now, it has attributes typical of an endangered species according to the standards of IUCN. Therefore, more attention should be paid for the conservation of this species such as establishing nature reserves in its original habitat as well as ex-situ conservation efforts.

In order to understand more about mechanisms of and factors that influence CH₄ and N₂O production in wetlands, fluxes of CH₄ and N₂O were measured using static-chamber and gas-chromatography methods in a marsh wetland, located at the Honghe Farm in eastern part of Heilongjiang Province, China (47°35'17.8″ N, 133°37'48.4″ E), from June to September,2003. Three plant communities, Carex pseudocuraica, Carex lasiocarpa and Deyeuxia angustifolia, were selected to measure fluxes of CH₄ and N₂O to contrast the variance of the emission rates of both greenhouse gases in these different plant zones. Air temperature and soil temperature at 5 cm depth, soil redox potential (0-100 cm), and standing water depth at each site also were measured to determine the main factors that control CH₄ and N₂O emissions within and among plant zones.

The wetland was a source of both CH₄ and N₂O during the growing season and emissions showed conspicuous temporal and spatial variations. Similar temporal variations of CH₄ and N₂O fluxes were observed in the C. pseudocuraica and C. lasiocarpa sites. Emission rates of CH₄ were higher in July and August while emissions of N₂O were higher in July and September. However, the highest emissions of CH₄ and N₂O in the C. angustifolia site occurred about one month earlier than in the C. pseudocuraica and C. lasiocarpa sites. The highest CH₄ emissions observed in the wetland were in the C. pseudocuraica site on July 19 with a rate of 696.24 mg·m^-2·d^-1, and the highest N₂O emissions were in the D. angustifolia site on June 12 with a rate of 2.53 mg·m^-2·d^-1. The average CH₄ flux from the C. pseudocuraica site was 273.6 mg·m^-2·d^-1, the highest among the three sites over the growing season but was not significantly different from 259.2 mg·m^-2·d^-1 of the C. lasiocarpa site. However, both were significantly higher than the 38.16 mg·m^-2·d^-1 measured in the D. angustifolia site (p<0.000 1). These results showed that average CH₄ fluxes in submerged wetlands were higher than in seasonal wetlands. N₂O fluxes from the C. pseudocuraica, C. lasiocarpa and D. angustifolia sites were not significantly different (p=0.967) with an average flux of 0.969, 0.932 and 0.983 mg·m^-2·d^-1, respectively, suggesting that submerged and seasonal wetlands had similar rates of N₂O emissions.

Air temperature, soil temperature, soil redox potential and standing water depth were important factors influencing emission rates of CH₄ and N₂O from the wetlands. Relationship analysis showed that CH₄ fluxes were correlated weakly with air temperature and soil temperature at 5 cm depth within a site (0.201<r<0.560) but not correlated with standing water depth ((0.100<r<0.176). Strong correlations were found between N₂O fluxes and standing water depth (r₁=-0.701; r₂=-0.528), but no correlation between N₂O fluxes and air temperature and soil temperature at 5 cm depth in the C. pseudocuraica and C. lasiocarpa sites (-0.089<r<0.211) was found. However, in theD. angustifolia site, there were no correlations between N₂O fluxes and the three factors (r<0.344). These results indicated that temperature was more important in influencing CH₄ emissions in the seasonal and submerged wetlands whereas standing water depth was more important in influencing N₂O emissions in the submerged wetlands. Furthermore, standing water table was the main control of the difference in CH₄ emissions among plant zones. However, there appeared to be similar rates of N₂O emissions among plant zones in the wetlands with strongly anaerobic conditions.

Soil is an important component of the terrestrial ecosystem and plays a critical role in global carbon cycle. Better understanding the distribution pattern of soil carbon storage along environmental gradients will facilitate the projection of global change on terrestrial C cycling. This study was conducted to examine soil organic carbon and nitrogen contents in major grassland types along elevation gradients in the source region of Yangtze, Yellow and Lantsang Rivers. Soil organic carbon and nitrogen contents were greater at the highest (5 120 m a.s.l.) and lowest (4 176 m a.s.l.) sites and lower at middle site. Soil organic carbon and nitrogen contents increased with soil moisture along the altitudinal gradient. Partial correlation analysis showed that spatial variability of soil organic carbon and nitrogen contents at 0-30 cm soil layers could be primarily explain by soil moisture with partial correlation coefficients of 0.946 5、0.905 9 (p<0.01), respectively. In addition, soil organic carbon and nitrogen contents showed positive linear correlations with plant cover and productivity and negative correlation trend with soil pH and total salt content.

Measurements of soil respiration, soil temperature and rice biomass were made during the rice growing season in the hill region of the central Sichuan Basin from April to September 2003. Characteristics of the daily and seasonal variations of soil respiration and their controlling factors are presented. The results showed that daily variations of soil respiration could be modeled with a single peak curve. The minimum and maximum soil respiration values from rice fields occurred at 7∶00 and 15∶00, respectively. Daily soil respiration rates were highly correlated with 5 cm depth soil temperature measurements. The mean rate of soil respiration was 121.76 mg·m^-2·h^-1, ranging from 18.00 to 269.69 mg·m^-2·h^-1 during the growing season. Rice root biomass and 5 cm depth soil temperatures were the major factors influencing soil CO₂ emissions during the entire growing season. There was a significant relationship between the rate of soil respiration and root biomass of rice during the initial growing season. From the middle/late stages to mature stage, 5 cm depth soil temperatures played a key role in regulating soil CO₂ emissions from rice fields, while the relationship between the rate of soil respiration and water levels in the rice fields was not obvious.

Minirhizotrons provide a nondestructive, in situ method for directly viewing and studying fine root dyanmics. In this paper, we introduce the minirhizotron methodology for measuring root systems, compare results between the minirhizotron and the soil corer method, and compare root growth dynamics under different soil water conditions. The experiments were conducted on a re-vegetated Caragana korshinskii quadrat at the Water Balance Experimental Field (WBEF) of Shapotou Desert Research and Experimental Station, Chinese Academy of Sciences (CAS) during the growing season in 2004. Shapotou is located at 37°33' N, 105°02' E in Ningxia Hui Autonomous Region at the southeastern edge of the Tengger Desert in northern China, elevation 1 250 m with a mean annual precipitation of 186.2 mm. It is classified as a steppified desert zone and is a transitional zone between desert and oasis. In September,2003, a block of soil was excavated from the C. korshinskii quadrat and 3 minirhizotrons were placed at a 45° angle at a distance of 20, 50 and 100 cm from the sample plant and the soil repacked. Beginning on March 27,2004, root images were collected every two weeks, and the soil water content was measured by neutron probe and TDR. Roots were colleted with a soil corer each month from a depth of 0-200 cm at 10 cm depth intervals. The results indicated that 10 months were required to allow the roots to recolonize the soil following the tube installation. The 2-D minirhizotron images were equivalent to a 2.6 mm depth of field (DOF) around the tube, within which all roots were observed. The root growth dynamics of C. korshinskii supplemented with soil water resulted in a great deal of root growth; however, root water uptake and evapotranspiration by C. korshinskii subsequently would reduce the soil water content and slow growth. The interactions between root growth and soil water content went through two cycles, and the lag time between growth of root apices and reductions of soil water content was about 20 days.

Here, we studied the effects of ethylene production inhibitors (cobalt chloride (CoCl₂) and aminoethoxyvinylglycine (AVG)) on the leaves of Vicia faba seedlings under heat stress. Ethylene production in the leaves was inhibited significantly before heat stress and after 12 h heat stress when the seedlings were irrigated with 20 μmol·L ^-1 CoCl₂ or 20 μmol·L ^-1 AVG solution for 7 days. Treatment with 20 μmol·L ^-1 CoCl₂ increased significantly the activities of SOD, CAT and APX before heat stress, while the treatment with 20 μmol·L ^-1 AVG had no significant influences. Treatments with 20 μmol·L ^-1 CoCl₂ and 20 μmol·L ^-1 AVG did not influence the contents of putrescine (Put), spermidine (Spd), spermine (Spm), chlorophyll, and the production rate of reactive oxygen species (ROS). However, after 12 h heat stress of 45 ℃, treatments significantly promoted the above values. These results showed that when plants suffered 12 h heat stress of 45 ℃, treatment with 20 μmol·L ^-1 CoCl₂ and 20 μmol·L ^-1 AVG inhibited ethylene production, increased the content of these amines and enhanced the activities of the anti-oxidative enzymes, restrained the enhancement in the content of ROS, and alleviated the reduction in membrane stability index, by which the leaves of Vicia faba seedlings were protected.

In order to examine the effects of Pb pollution on photosynthesis, quality, and yield of tobacco cultivar, pot experiment was carried out at the Research Station of Henan Agricultural University during 2002-2004. Cultivar of `Yunyan 85' was treated with seven concentration levels of Pb²⁺ (0, 150, 300, 450, 600, 750 and 1 000 mg·kg^-1) applied with (CH₃COO)₂Pb after transplanting. Twenty leaves were saved after topping. The net photosynthetic rate (P_n), intercellular CO₂ concentration (C_i), and stomatal conductance (G_s) of three identical functional leaves from the same position were measured during rosette, budding, and harvest stages respectively using a Li-6400 Portable Photosynthesis System. Maximal fluorescence (F_m),fixed fluorescence (F_o), and steady fluorescence (F_s) were determined in the dark (for 30 min) and maximal fluorescence in the light (F_m') with a Hansatech FMS2 photo-fluorometer. PSⅡ activity (F_v/F_o), PSⅡ maximum light energy transformation (F_v/F_m), chemical quenching coefficient (q_P), non-photochemical quenching coefficient (NPQ), apparent photosynthetic electron transport rate(ETR), and the ratio of photochemical quantum yield of PSII (Ф_PSⅡ) were calculated.The reductive sugar, total N, nicotine, Kalium contents of tobacco leaves and yield per plant were investigated.

The results showed that P_n, G_s, and C_i occurred at the Pb concentrations of 300 mg·kg^-1 in budding stage and the Pb concentrations up to 150 mg·kg^-1 in rosette and harvest stages. F_v/F_o, F_v/F_m, q_P, NPQ, ETR, and Ф_PSⅡ decreased with increasing Pb concentrations, resulting in declining ability of photosynthetic pigments assimilating light, photosynthetic light use efficiency, and P_n of tobacco leaves. Higher Pb concentrations led to increases in the ratios of reductive sugar/nicotine (9.52-11.96) and total-N/nicotine (1.05-1.23), which are used as the quality indexes of tobacco leaves, above the standards (7 and 1) of high quality of tobacco leaves, and then deteriorated the fragrance of tobacco leaves.

With the development of molecular marker techniques, researchers have begun to study the genetic mechanisms that control the chlorophyll content (CC) of plants. Researchers have mapped some of the quantitative trait loci (QTLs) controlling CC in different genetic rice populations. Because drought is the major obstacle to agriculture production, this study was carried out under well water and water stressed conditions to map QTLs affecting CC, and to analyze correlations between the CC and photosynthetic rate (P_n) with a recombinant inbred line (RILs) population. The objective was to provide a theoretical foundation for better understanding the molecular genetic mechanisms of CC under different water conditions, breeding with marker assistance selection, and development of drought tolerant and water saving rice cultivars. A significant positive correlation between CC and P_n (r=0.185 7^**) was found under normal watering conditions, but there was no significant correlation (r=0.076 6) under drought stress. A total of 13 main QTLs related to CC were detected and located on chromosomes 1, 2, 3, 4, 5, 6, 10. Of these, 6 QTLs were identified under drought stress with an accumulated contribution of 47.39% and 7 QTLs were identified under normal conditions with a total contribution of 56.19%. A total of 16 pairs of digenic interactions were detected including 4 pairs under drought stress with a total contribution of 18.57% and 12 pairs under normal conditions that accounted for 38.49% of the total.

Vallisneria natans is a dominant submerged macrophyte in Lake Taihu. The biomass and quantity of propagules of V. natans were investigated in Lake Taihu in October, 2003 and in March, 2004. Seed and tuber germination, and development of seedlings produced from tubers under different conditions were also studied in the laboratory. Our objectives were to understand characteristics of the reproductive ecology in V. natans. The results showed that the biomass of asexual and sexual propagules was 10.1%±7.0% and 25.0%±13.8% of total biomass, respectively, and the biomass of sexual propagules was greater than asexual propagules. The average number of female flowers was 22.9±13.8 per individual plant, and seedset rate was 73.3%±17.9%. There were 11-33 spathes per individual male plant and 364±38 male flowers inside each spathe. Based on ourin situ investigation, we estimated a density of 6.29×10⁵-1.89×10⁶ microspores·m^-2 around V. natans populations in Lake Taihu. Seedlings produced from seeds were not able to survive in Lake Taihu, which is likely caused by factors such as wind, wave and water depth. Most populations in V. natans reproduced asexually from root tubers. We estimated a mean tuber density of 90-226 per square meter. Light, temperature, sediment, thermal fluctuation and seed age had a marked influence on germination rates. Germination rates of seeds stored for 4 months under water in the lake was 8.35%±1.89%, 56.73%±6.42% and 43.55%±4.34% at 10, 20 and 30 ℃, respectively. Seed germination rates stored for one year was 35.53%±3.53% under natural light conditions and decreased to 12.63%±2.86% under dark conditions. Germination rates of seeds stored for one or two years was 35.53%±3.53% and 12.63±2.86%, respectively. Germination rates of seeds stored for four years was near zero. Germination rates of seeds decreased under conditions without sediment. Tubers did not require light for germination. There was an optimal temperature of 20 ℃ for tuber germination to occur that was as high as 90.2%±12.6%. Biomass accumulation in seedlings produced from tubers under light conditions was greater than that in the dark, while leaves of seedlings grown in the dark were longer. Seedling increases in length mainly depends on the stems of the lower end of leaves. We present suggestions for restoration efforts of populations ofV. natans in Lake Taihu.

Crofton weed gall fly (Procecidochares utilis) has been used widely as a natural enemy to control the invasive plant, crofton weed (Eupatorium adenophorum), but the effectiveness and mechanisms of crofton weed gall fly in controlling and preventing the weed have not well been studied. In this paper, we surveyed parasitism of gall fly on crofton weed in ecosystems that had been damaged by crofton weed in the western Panzhihua Prefecture, Sichuan Province, Southwest China. We studied the effects of the gall fly on the growth and reproduction of crofton weed by comparing the parasitism rates of individuals and branches with different ages in different habitats. The diameter, quantity of blossom branches, capitula and seeds between parasitized and normal branches also were compared. The results showed that: 1) there were significant differences (p<0.05) in the parasitism rates based on individuals (71.67%) and branches (17.30%). There were, on average, 17.48 parasitized branches per square meter in the adult population; branches with one insect gall accounted for 92.30% of the total parasitized branches. 2) The parasitism rate of branches (20.27%) in the humid habitat was markedly higher than that in the drought habitat (p<0.05). 3) The parasitization rate of branches differed significantly among individuals of different ages. Parasitism rates of seedlings (36.36%) and one-year-old individuals (21.56%) were significantly higher (p<0.05) than older individuals (13.50%, 8.82%, and 12.16% for two-year, three-year, and four-year old individuals). 4) Crofton weed gall fly had no significant effect on the diameter of branches, quantity of blossom branches, capitula or seeds of crofton weed, suggesting that parasitism of crofton-weed gall fly would not impact the growth and reproduction of crofton weed.

The relationship between plants and environmental conditions is one of the most basic characteristics of plant communities. The humid hilly regions are a complex habitat that has various degrees of disturbance related to water erosion. At an intermediate-scale level, the region can be divided into an upper and lower hillslope area divided by an erosion front. At a more detailed-scale, the sections can be divided further into micro-scale geomorphological units. The upper hillslope area contains a crest slope, upper sideslope and head hollow etc. and the lower hillslope contains a lower sideslope, foot slope, flood terrace and river bed etc. The upper and lower hillslopes are two basic functional land area types for assessing species composition and forest structure. On the upper hillslope area, the vegetation changes gradually and continuously from the crest slope, to upper sideslope and head hollow. On the lower hillslope, however, the micro-landform units have little effect on vegetation structure as disturbance plays the most important role in regulating vegetation patterns. The lower hillslope area is characterized by active soil erosion, landslides and slope failures. Thus, the plant communities that develop on it are early successional communities, and their regeneration depends on active surface disturbance. However, the plant communities that develop on the upper hillslope areas are climate climax communities as it has been stable for a long time, and their regeneration can be explained based on the gap dynamic theories. Topography is the most basic and important habitat factor affecting vegetation patterns. Habitat niche differentiation related to topographic variation supports the coexistences of species and results in high species diversity at small spatial scales.

Mycorrhizal fungi form the most important mutualistic symbioses on earth with plants. The most prevalent type of mycorrhizal fungi are the arbuscular mycorrhizal (AM) fungi. Much research has shown that the development of AM fungi is correlated with plant secondary metabolism. AM fungi can directly or indirectly affect plant secondary metabolic processes. Secondary metabolites are classified into 3 groups, terpenoids, phenolics and alkaloids. In this paper, we summarize the effects of AM fungi on the 3 groups of secondary metabolites.

The relationship between terpenoids and AM fungi have been well studied, and some research has explored interactive mechanisms at the molecular level. Blumenin was first isolated and identified from mycorrhizal cereals, and its biosynthesis has been proven via the Glyceraldehyde 3-phosphate/ pyruvate pathway (MEP) by an isotopic labeling method. Since then, the accumulation of blumenin induced by AM fungi and differences in blumenin levels among different kinds of AM fungi have been observed. Studies on 1-deoxy-D-xylulose-5-phosphate synthase (DXS) and 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), two key enzymes in the biosynthesis of carotenoid metabolism via the MEP pathway, have found to increase the transcription of DXS and DXR in plants with AM fungi. Moreover it was temporarily and spatially correlated with the accumulation of apocarotenoids. Subsequently, two genes were identified: TC78589 encoding DXS2 which is highly expressed in roots inoculated with AM fungi, and TC77051 encoding mevalonate disphosphate decarboxylase, which is catalysed in the synthesis of terpenoids in the mevalonate pathway. Although both genes separately encode enzymes in different pathways, an enhancement of carotenoid biosynthesis has been observed.

The interaction between phenolic compounds (such as phytoalexin, wall-bound phenol, flavonoids, isoflavonoids and their derivatives) and AM fungi also has been investigated intensively. It has been shown that some flavonoids stimulated the spore germination and hyphal growth of AM fungi, and the contents of flavonoids increased before the infection of AM fungi. Therefore some investigators hypothesized that flavonoids were a signal compound during the formation of AM fungi. Afterward, increased levels of flavonoids were found after the formation of AM fungi which was related to specific species of AM fungi. In addition, some experiments have indicated that the activity of peroxidase (POD), phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO) were significantly enhanced in AM plants. In phenylpropamoid metabolism, there are two different signaling pathways in the accumulation of secondary metabolites induced by the mycorrhizal fungus: one is through the induction of PAL and chalcone synthase (CHS), and the other is through the suppression of isoflavone reductase (IFR).

Although little research seldom has examined the relationship between alkaloids and AM fungi, a recent study has shown that the formation of AM is beneficial to the accumulation of alkaloids. This study also showed the species specificity in AM affected biosynthesis of alkaloids.

Canopy-dwelling epiphytes and their associated dead organic matter are important floristic, structural and functional components in montane moist forests. Because of the difficulties related to access, the biodiversity and ecosystem-level functional attributes of epiphytes have received little attention in forests. With an increase in our understanding of epiphytic biodiversity and their roles in ecosystem-level interactions, combined with improved access to the forest canopy, studies on epiphytic organisms in forest canopies have progressed from the individual level to the ecosystem level. Biodiversity and biomass of epiphytes and their functional roles at the ecosystem-level are becoming a hot topic of recent study. Recent work in tree canopies in a variety of forest types, however, has pointed out that the role of epiphytes in ecosystem-level interactions are more important than previously thought due to their anatomical, morphological, and physiological characteristics. Considerable research conducted worldwide has shown that the forest canopy is a favorable habitat supporting a much richer epiphytic flora than previously thought. It was estimated that there are 29 500 epiphytic species, including 24 000 vascular epiphytes that account for 10% of the total vascular species in the world. There are large differences in the epiphytic biomass of forests worldwide ranging from 105-44 000 kg·hm^-2. The biomass of epiphytic material of forest canopies was greater than the leaf biomass of host trees in some old growth forests. Epiphytes have a tremendous leaf area index (LAI). Epiphytes play an important role in biodiversity, water and nutrient cycling in forest ecosystems, and are sensitive indicators of environment change, due to rich species, high biomass and special morphological traits and their position at the forest-atmosphere interface. The epiphyte community also provides a source of food and habitat for a variety of birds, mammals, amphibians, reptiles, and insects.

Species composition, growth and distribution of epiphytes are influenced by environmental factors and human disturbance. Research on epiphytes in forest canopies still is very active due to a lack of field data at the ecosystem level for a lot of forest types under different environmental conditions in many regions. International forest canopy networks have been established worldwide. To understand the relationship among community characteristics, environmental factors and epiphyte dynamics, and develop effective and standard methods and technologies for the study of forest canopies, more work is needed in this field. In China, there has been very little work on the ecology of epiphytes in forest canopies, and this remains a challenging and fruitful area for future research.

The genetic diversity and genetic variation within and among three natural Carya dabieshanensis populations were studied using RAPD analysis. The result showed that 238 loci were detected by using 20 random primers (10 bp) of which 162 loci were polymorphic (68.1%). Species genetic diversity indicated by Shannon's index was 0.476 1, 58.18% of which was due to within population genetic diversity and 41.82% among population variation. Species gene diversity indicated by Nei's index was 0.314 5, gene diversity within populations (H_S) was 0.186 5, gene diversity among populations (H_ST) was 0.128 0 and the coefficient of gene differentiation (G_ST) among the populations was 0.406 7, 59.33% of which was within populations and 40.67% was among populations. The gene diversity estimated by Nei's index was consistent with that estimated by Shannon's index. These results suggest that there is rich genetic within population variation, which offers excellent prospects for seeding selection. The estimate of gene flow from G_ST (N_m) was 0.730 6, indicating that genetic recombination between populations is quite small, which probably is related to environmental adaptations of C. debieshanensis and population isolation in their high mountain habitat.