The recent advance of research on fungi in forest ecosystem is reviewed in this paper. It is shown that fungi are important components in forest ecosystem with their roles in establishing plant community, promoting succession of species population, retaining forest ecosystem stability and participating in the flow of energy and nutrition. The early colonization of land by plants was associated with fungi. Evidences have shown that the symbiosis between plants and fungi was established when the terrestrial life started. By co_evolution with plants, fungi are involved in the formation of the complex forest ecosystem. Mycorrhizae have apparently played an important role in the origin of terrestrial plants and they are the key to the development of forest. Mycorrhizal fungi are crucial not only to phosphorus uptake by plants, but also to other mineral nutrition. Decomposition of organic material and weathering of mine by fungi in forest contribute greatly to the biogeochemical and nutrient cycles on earth. Large biomass of fungi in forest forms important C and N sinks. Abundance and diversity of fungi in forest has significant influences on biodiversity and stability of forest community. Loss of fungal diversity may instable the forest ecosystem and, further, aggravate the greenhouse effects of the world. Enforcing research on fungal roles in forest ecology will facilitate conservation and sustainable development of forest and the forest ecological projects in China.

The plant breeding system has become the most active and promising area among the recent evolutionary studies. In its definition, the plant breeding system represents the sum of all sexual characteristics that could possibly in fluence the genetic c

Environmental temperature influences the carbon and nitrogen metabolis process and changes the growth rhythms of plants. Advances in photosynthetic rate, sucrose synthesis in leaves, nonstructural carbohydrates metabolism in sheath and stems, and starch synthesis rate in kernels of wheat and their responses to temperature were reviewed. It was concluded that kernel weight and yield would decrease when the temperature is above 30 ℃. Wheat quality is determined by the characteristics of gluten protein. We summarized some advances in protein formation, contents and components of wheat kernel and their relationships with temperature. According to the changes in gluten protein under different temperatures, the bake quality of wheat would become worse under heat stress. Global warming would enlarge the heat stress during the filling stage of wheat, and three suggestions were made for further research in this field: 1) studies on the co_influence of CO2 concentration and temperature evaluation on wheat yield and quality; 2) studies on the physiological mechanism of heat tolerance and planting regulation; 3) Identify the heat tolerant gene and breed heat tolerant cultivars.

A better understanding of the effect of temperature and moisture on soil microbial activity can improve our ability to predict soil N mineralization. The objective of this study was to evaluate the effects of temperature (t) and soil moisture (wfps: water filled pore space) on soil nitrogen mineralization in Chinese forest ecosystems. The soil cores were kept in PVC tubes, adjusted to different soil water content, and separately incubated at four temperatures for 30 days. The inorganic N in soil extracts before and after incubation was analyzed. The results showed that soil nitrogen mineralization rate (Rmin) and nitrification rate were linearly related to t and wfps (p<0.001). Three dimensional equations were developed to describe these effects: Rmin=e-7.60+0.07×t+14.74×wfps-10.41×wfps2. We scaled up the effect of temperature and moisture on soil nitrogen minerali zation to a national scale. Field measurements agree with the estimate of the re gression model.

Objectives of the research were to determine the extent of internal cycling of Nitrogen (N) in Leymus chinensis grasslands using the compartment model method. The internal ecosystem was divided into five compartments: (i) Above_ground N, (ii) Standing dead and litter N, (iii) Living root N, (iv) Soil organic N, and (v) Soil mineral N. Above_ground biomass was harvested from five 1 m ×1 m quadrats in each plot while the underground biomass was collected from 25 cm×25 cm sections at 30 cm soil depth. The soil samples were washed, and dead roots were separated from living roots. Soil N for total N and mineral N test was sampled at two depths (0_15 cm and 15_30 cm). The above samples were collected at 4 weeks intervals between mid_April to mid_September with five replications. Standing dead and litter were collected from five 1 m×1 m quadrats in mid_October, 1994, each 100 g of the samples was put into one nylon net bags, total 30 bags of the samples were randomly scattered on grassland soil surface, and 5 samples were collected every month from mid_April to mid_Sep, in 1995. The remaining samples were weighed and N content was tested for each sample. The total N of plant and soil was measured using Kjeldahl digestion method. The amounts of NH+4-N and NO－ 3-N measured by distillation method. The result indicated that the soil_plant system contained 479.2 g·m-2 of N, nearly all in the organic form. The plant available N, about 1.5% of total N in the forms of NH+4 and NO－3,the seasonal changes of the two forms were great, the storage of soil mineral compartment was between 2.55-11.3 g·m-2，and the content of NO－3 -N was even higher than NH+4N, which is different from the other type grasslands, where the peak of NH+4-N contents appeared earlier than that of NO－3 -N contents. Plant root uptook N 3.48 g·m-2·a-1, the above_ground took up N 2.97 g·m-2·a-1, the N re_translocation was about 1.54 g·m-2·a-1 from above_ground to root. The N of above_ground biomass that turned to litter N is 1.43 g·m m-2·a-1. Approximately 1.08 g·m m-2·a-1 N in litter changed to soil organic N, and 1.51 g·m m-2·a-1 of N from the root changed into soil organic N. Comparison between Canadian mixed prairie and Northeast China L. chinensis grasslands indicates that the utilization efficiency of soil N for grasses is lower in L. chinensis grasslands than that in Canadian mixed prairie.

To quantitatively investigate the influence of plant nitrogen and lignin content on the residue carbon decomposition, CO2-C was measured from an incuba tion experiment with 19 plant residues plus soil under 25 ℃ and water conte nt of 400 g·kg-1 air dr

The changes of ionic absorption, secretion and the activity of POD on Aeluropus pungens under salinity conditions and the effects of silicon nutrition on those indices were studied using light microscopy, cytochemical localization, and quantitative and qualitative analysis for ions and physiological indices. The results were as follows: Under salinity conditions, the Na+ content increased and the Ca2+ content of the plant tissues decreased, while the other ions remained constant, and the concentrations of silicon in leaves increased with increasing salinity. The rate of ion secretion increased between 0 and 60 mmol·L-1 NaCl, and then declined when the NaCl concentrations in the roots reached 120 mmol·L-1. The content of soluble protein was unaffected but the POD activity was enhanced by the salt treatment. The amount of soluble proteins were higher in the roots than that in the leaves, while on the POD activity, the situation was the contrast. The water content did not change within 120 mmol·L-1 NaCl. The cytochemical location of Si distribution and POD activity techniques showed silica was distributed in rows along the leaf veins on the leaf surfaces, and some traces on the papillaes. On the salt glands Si accumulated on the top of the cap cell where the strong POD activi ty was found. By analyzing the elements, it was found that silicon tended to accumulate on the tissues of Aeluropus pungens. The Na content and the selective of Na, K of the shoots, which was not affected under 120 mmol·L-1 NaCl, was reduced under 60 mmol·L-1 NaCl by the addition of 3 mmol·L-1 Na 2SiO3. However, the Na content remained unaffected in the roots by the addition of Silicon to both salt concentrations. The above experiments demonstrated that halophyte Aeluropus pungens adapted to salinity conditions by adjusting water conditions, the ion distribution and POD activity on the plant tissues. The capacity of salt tolerance was improved, which was due to the inhibition of the Na transport from roots to shoots and the increasing abilities of antioxidative defense when silicon was added to the nutrient solutions.

There has been a phenomenon in wheat production of attaching importance to nitrogen fertilizer but ignoring potassium fertilizer. Employing nitrogen fertilizer solely results in excessively growing, soft stemmed, wheat, leading to a reduction in kernel yield. Also, the soil hardens and the environment is destroyed. As one of the indispensable elements, potassium has become an important limiting factor in wheat kernel yield increasing. This article studied the effect of potassium on photosynthetic rate, sucrose content, activity of sucrose_phosphate synthase (SPS)—the key enzyme in sucrose synthesis—in flag leaves, and on the sucrose content, activity of sucrose synthase (SS) (the key enzyme in sucrose decomposition), activity of adenosine phosphorate glucose pyrophrylase (ADPGPPase) (the key enzyme in starch formation), and starch accumulation rate of kernels of wheat. The study was carried out in 1999 on an experimental farm of Shandong Agricultural University, Taian,China,using the variety `Lumai 22’which has high yield potential. The experiment set three potassium treatments (K0, K1 and K2); the potassium amounts supplied were 0 kg K2O, 168.75kg K2O, 225.00 kg K2O per hm2 respectively,using KCl as the potassium fertilizer. Each treatment had three replicates. The plot area was 2 m×6 m=12 m2, with sowing on October 11 in 1999. The basic seedling number was 120 per m2. Single stems flowering on the same day were selected and marked using hanging cards during the anthesis period. These marked stems were used as the sample. The results suggest that potassium can prolong the peak period of photosynthetic rate, increase the supply of photosynthetic products in flag leaves, improve the activity of SPS after anthesis, accelerate sucrose synthesis during the early and middle periods of kernel filling in flag leaves, and increase sucrose content in flag leaves. Potassium also enhanced the supply of sucrose in the kernel during kernel filling, increased the activity of SS which favors sucrose decomposition in the kernel, and produces sufficient precursor for starch synthesis; improved the activity of ADPGPPase which favors starch formation; accelerated the rate of starch accumulation during the peak period of starch synthesis, and finally increased spike number, kernel weight and yield in wheat. Among the three treatments, each index had the greatest value in the K1 treatment. So the K1 treatment produced the highest kernel yield.The physiological effects of potassium on yield in wheat were discussed from two points of view, namely, from the point of photosynthetic product supplying intensity in flag leaves and precursor supplying intensity in kernel sink, concentrating on key enzymes. It was considered that potassium could increase kernel weight and yield by increasing the activity of SPS in the flag leaf and increasing the activities of SS and ADPGPPase in the kernel, but the physiological and biochemical mechanisms underlying this action should be investigated further. Furthermore, this article also discussed the reason why the K1 treatment is superior to the K2 treatment. It is possible that root absorption of K+ and NO-3 -N are inter- related, and so an excessive K+ concentration could affect the absorption of NO-3 -N in the root. This would result in an effect on nitrogen absorption and transportation throughout the wheat plant, causing a reduction in wheat yield. The physiological mechanisms behind this effect require further study.

Soil respiration is not only an indicator of belowground metabolic activity of roots and soil microbes, but also a necessary component of carbon cycle. Measurement of the CO2 efflux from soil and the determination of the relationship between soil respiration and environmental factors such as temperature and water regime are of great importance in understanding the carbon cycling processes in terrestrial and aquatic ecosystems. To evaluate the role that the degraded steppe ecosystems in the temperate China play in global carbon cycle and to determine the factors that regulate soil respiration in these ecosystems, we conducted field experiment to examine the soil respiration rate by using the alkali absorption technique in a degraded steppe community in the Xilin River Basin, Inner Mongolia. We also evaluated the influence of temperature and soil moisture on soil respiration rate. The research site is located in the Baiyinxile Livestock Farm (43°55′ N, 116°19′ E, with an altitude of about 1 200 m). This region has a typical temperate and semi_arid climate. The topography is basically flat with mild relief and the soil is classified as chestnut. The original vegetation was Leymus chinensis steppe, and, due to over_grazing in the past decades, the vegetation has degraded to some extent depending on habitat types and grazing intensity. More than 30 species of plants can be found in the region, among which Achillea frigida，Cleistogenes squarrosa and Carex korshinskyi are the most dominant, followed by L. chinensis, Stipa grandis, Agropyron cristatum, Heteropappus altaicus and Kochia prostrata in terms of their importance value. In addition,Caragana microphylla is sparsely scattered. The maximum coverage is about 40%.The seasonal pattern of CO2 efflux was irregular, though the rate of CO2 evolution was greater in summer than in other seasons. Significant relationships were found between CO2 evolution rate, ambient air temperature and soil temperature (the surface, 5 cm depth, 10 cm depth, 15 cm depth and 20 cm depth, respectively), which could be best described by exponential equations (R2=0.407-0.571 4, p=0.001 8-0.014 1). The influence of temperature was more conspicuous at lower temperature than at higher temperature conditions. This was consistent with the results reported by other researchers. Soil respiration rate was linearly correlated with soil gravimetric water content at 0-10 cm (R2=0.422 5, p=0.011 9) and 10 20 cm (R2=0.500 9, p=0.004 6), but more significant power functions could be obtained after removing the confounded effect by temperature (0-10 cm: R2=0.551 8, p=0.003 9; 10-20 cm: R2=0.645 1, p=0.000 8). The relationship between soil respiration rate (y) and the two variables of air temperature (Ta) and soil moisture at 10-20 cm soil depth (M2) could be described by the following multiple regression equation: y=5 911.648×e0.042 16Ta×M20. 907 58 (R2=0.858 4,p<0.000 1). This equation has much more predicative power than that using temperature and water as single independent variables. The mean soil respiration rate during the study period was 661.35 mg C·m-2·d-1, and the calculated Q10 values based on air temperature and soil temperature at surface, 5 cm, 10 cm, 15 cm and 20 cm depth were 1.63, 1.47, 1.52, 1.70, 1.90 and 1.97, respectively. Both Q10 and soil respiration rate were lower at our study site than at the original L. chinensis community studied by Li et al. (2000) in the adjacent area, possibly due to the difference in water content in the two sites. Our results implied that drought in the growing season tended to have lower Q10 values and lower soil respiration rate. We suggested that the variations in soil respiration and Q10 between degraded and undegraded L. chinensis steppe ecosystems as affected by other environmental factors need to be further studied.

Pometia tomentosa, is a dominant uppermost canopy tree and a symbol species of vallyland forest in Xishuangbanna tropical rainforest. In addition to anatomical and physiological characteristics, diurnal changes in chlorophyll fluorescence parameters were measured with a modulated chlorophyll fluorescence monitoring system (FMS2) in order to explore the difference of diurnal photoinhibition in leaves of two developing stages, young fully expanded leaves and mature leaves of Pometia tomentosa in the rainy season. The difference in the effect of midday strong light and high temperature on the activities of partly protective enzymes was also briefly analyzed. The results showed: leaf thickness, chlorophyll contents, stomatal conductance, carboxylation efficiency, maximum net photosynthetic rate and light saturation point of mature leaves were much higher than those of young fully expanded leaves, while the stomatal density and guard cell length were similar between two leaves. On clear days in the rainy season, the highest photon flux density can exceed 2 200 μmol·m-2·s-1, the highest leaf temperature was 7-8 ℃ higher than air temperature, and the highest leaf temperature of mature leaves was 1.5-2℃ higher than that of young fully expanded leaves. Non-photochemical quenching (NPQ) was increased, the initial photochemical efficiency (Fv/Fm) and actual photochemical efficiency ［(Fm′-Fs)/Fm］ decreased gradually in the morning, and reached the lowest values at about 15∶30. The reverse changes occurred in the afternoon, at dusk these parameters could recover to nearly the original dawn level. The decrease in Fv/Fm was mainly caused by a decrease in Fm, because initial fluorescence (F0) did　not change significantly over the course of the day. This suggested that the photoinhibition observed in Pometia tomentosa was due to photoprotective process and not to photoinhibitory damage. The initial photochemical efficiency (Fv/Fm) of young fully expanded leaves was lower than that of mature leaves, and exhibited more sensitiveto strong light and high temperature treatment, but their diurnal photoinhibition was statistically similar in the field. After field strong light at midday the protective enzymes (SOD, APX) increased, while H2O2 content was stable and the lipid peroxide level was lower in young expanded leaves compared with mature leaves. We concluded that the alleviated photoinhibition in young expanded leaves might be caused by its lower photochemical efficiency and leaf temperature, as well as active protection by higher activities of protective enzymes under the field conditions.

The effects of elevated CO2 concentration on growth and development of terrestrial plants have been studied intensively, but less scientific interest has been raised on aquatic plants. In this study, a greenhouse experiment with submersed species Potamogeton crispus, one of dominant species in lakes along Yangtze River Basin, was studied comparatively in higher (1 000±50 μmol·mol-1) and ambient （about 380 μmol·mol-1） CO2 concentration to tst whether CO2 has significant impacts on phenotypic and some physiological and biochemical characteristics as main effect. In addition, allometric analysis was applied to distinguish whether phenotypic changes such as total leaf area are induced by environment (plastic) or plant size dependent (non-plastic).The results showed that phenotypic characteristics of P. crispus leaf in elevated CO2 concentration changed significantly compared with that in ambient CO2 concentration. Leaf shape was more stubby, but leaf width, single leaf area, total leaf area per plant and leaf area ratio increased significantly in elevated CO2 concentration. However, specific leaf area and leaf length did not differ between treatments. Total leaf area per plant was closely correlated with plant weight, indicating that change in this phenotypic characteristic may depend on plant size. The result of allometric analysis certified that this change was a non-plastic response, but plant size dependent. In addition, higher CO2 concentration led to the changes in pigment concentration. Chlorophyl a, chlorophyl b, total chlorophyl, carotenoid concentration and the ratio of chlorophyl a/b decreased in elevated CO2 concentration. The soluble sugar concentration increased, but protein, N and P content decreased under higher CO2 condition. It is concluded that elevated atmospheric CO2 concentration results in significant changes in some physiological and biochemical characteristics, especially increase of soluble sugar concentration, but not necessary in leaf phenotype. Maybe “true” adjustment in leaf phenotype is under strong genetic rather than CO2 control.

The eco_physiological responses of dominant trees (Atraphaxis frutescens andElaeagnus angustifolia) to ground water availability were investigated in a controlled environment at the Plant Transpiration Consume Water Observation Station in Minqin Desert Botanical Garden, Gansu province. In this experiment, the depths of groundwater (DGW) were designed as 1.4 m, 2.4 m and 3.4 m. In each treatment, the two desert species were transplanted to the observation sites with different DGW after growing naturally for 3 or 4 years. The results showed that: 1) the changes of DGW resulted in the significant changes of net photosynthetic rate (Pn), the transpiration rate (E), stomatal conductance (Gs), leaf contents of chlorophyll a (Chl a), chlorophyll b (Chl b) and the total chlorophyll (Chl a + Chl b), the ratio of Chl a and Chl b (Chl a/Chl b), the quantum yield efficiency and the CO2 carboxylation efficiency; 2) although these two desert species were well adapted to the water stress environment at 3.4 m DGW, their adaptive strategies were different. In response to the water stress environment, A. frutescens  reduced its photosynthetic rate and maintained the level of water use efficiency, while E. angustifolia largely decreased the transpiration rate and thus increased the water use efficiency; 3) in different DGW, the optimal temperature of photosynthesis in these two desert species did not change significantly, but the net photosynthetic rate under the optimal temperature range declined markedly. Since E. angustifolia  is a nitrogen fixation species, further studies are needed to verify whether or not the differences of drought adaptation between these two species are related to the nitrogen fixation.

In order to elucidate the adaptation and ability of different xerophilous plants to soil water availability and provide the theories of vegetation regeneration for western desert areas in China, the photosynthetic physio_ecological characteristics and the contents of leaf chlorophyll, soluble sugar, starch, nitrogen, phosphorus and kalium of two desert plants (Atraphaxis frutescens and Elaeagnus angustifolia in response to ground water availability were investigated in a controlled environment at the Plant Transpiration Consume Water Observation Station in Minqin Desert Botanical Garden, Gansu province. In this experiment, the depths of groundwater (DGW) were set at three levels: 1.4 m, 2.4 m and 3.4 m. In each treatment, the two desert plants were transplanted to the observation sites with different DGW after growing naturally for 3 or 4 years. The contents of leaf chlorophyll, soluble sugar, starch, nitrogen, phosphorus and kalium of the two desert plants were measured by the methods described in “Experimental manual of plant physiology” and the photosynthetic measurements were conducted by using an open gas_exchange system (LI_6400P, LI_COR Inc. Lincoln, NE,USA).The results showed that: 1) the three different DGW treatments resulted in a marked soil moisture gradient; 2) The changes of DGW led to significant changes in the leaf content of chlorophyll a (Chl a), chlorophyll b (Chl b), total chlorophyll (Chl a+Chl b) and the ratio of Chl a to Chl b (Chl a/Chl b) (p<0.01); 3) The increment of DGW depths caused the increase of soluble sugar content and the decrease of starch content irrespective of plant species, but the extent of these changes varied between the two species; 4) Increased DGW caused a decrease in the content of nitrogen, phosphorus and kalium; 5) The changes of either increase or decrease in chlorophyll a, chlorophyll b, total chlorophyll, nitrogen, phosphorus, kalium, soluble sugar, starch and the ratio of Chl a and Chl b of A. frutescens and E. angustifolia varied with DGW. The original conclusions were drawn as follows: compared with A. frutescens, E. angustifolia may be more adaptive to the dry desert environment. Since E. angustifolia is a nitrogen_fixing species, further studies are needed to verify whether the differences between these two species are related to nitrogen fixation. 

Chinese fir (Cunninghamia lanceolata) is recognized as a highly productive, valuable tree species in the sub_tropical region of China. Chinese fir is monoecious, and self-fertilization is possible because time of pollen dispersal and seed cone recep

A preliminary study was conducted on the reproductive features of different populations of Veratrum nigrum along an altitudinal gradient in Dongling Mountains, Beijing. V. nigrum is a perennial, andromonoecious herb. We use P/O ratio (Pollen/ovule ratio) as an estimate of the level of outcrossing. Resource allocation was measured by means of dry weights.We found that the flowering individuals within a population were larger than the non-flowering individuals. The resource allocated to reproduction was strongly correlated with that allocated to vegetative growth. Individuals of V. nigrum would not produce flowers and fruits until a threshold size was reached, which ranged from 1.11 g to 3.98 g in different populations. The minimum size showed no trend along the altitudinal gradient, indicating that an invariable minimum vegetative biomass for the species might exist. Pooled together, a minimum size of 2.61 g for reproduction followed from the regression line. Above the threshold there existed a relatively simple linear relationship between vegetative and reproductive biomass. Population density decreased firstly and then increased along altitudinal gradient, but it seemed that density is not related, in a straightforward way, to the reproductive features of V. nigrum in the study region.Many workers had shown that the flowers of self-incompatible and other xenogamous taxa produced more pollen grains than closely related self-compatible and/or autogamous taxa, while the number of ovules per ovary was rather conservative, in contrast to other floral characteristics. In this article, we estimated P/O ratios both at the level of a hermaphrodite flower and at the level of an individual (including male flowers). We found that the difference in mean hermaphrodite flower P/O ratios among populations was not significant. Hermaphrodite flowers had P/O ratios from 799 to 1 090. However, the difference in mean individual P/O ratios among populations was strongly significant. The lowest individual P/O ratio was 1 601 and the highest was 4 146. According to the correlation between P/O ratios and mating systems established by Cruden, V. nigrum in Dongling Mountains was facultatively xenogamous. There was a positive correlation between the P/O ratios of hermaphrodite flower and the ratios of reproductive to vegetative biomass.Hermaphrodite flowers are mainly distributed at the tip raceme of the panicle, while males are at the lateral racemes. Sometimes, flowers near the base of the lateral racemes are hermaphrodite. Hermaphrodite flowers bloom earlier than male flowers, and the two flower types differed in dry weights. Hermaphrodite flowers averaged 5.10×10-3 g while male flowers averaged 4.04×10-3g. Hermaphrodite flo wers were on average 26% more massive than male flowers. Flower diameter was (1. 42±0.01) cm for hermaphrodite flowers and (1.24±0.01) cm for males. Hermaphrodite flowers were on average 15% larger than male flowers. However, the pollen producti on of hermaphrodite and male flowers remained almost the same. The results docum ented here suggest male flowers of V. nigrum provide resource savings to the plant compared to hermaphrodite flowers. Since male flowers have lower resource use for equal pollen production in comparison to hermaphrodite flowers, they are more efficient at male function than hermaphrodite flowers. These results lend support to the optimal resource allocation hypothesis for the function of male flowers within an andromonoecious sexual system.

Forested areas of eastern China are predominatly evergreen broad_leaved forests which are typically zonal or climatic climax vegetation in subtropical areas, dominated by Castanopsis fargesii Franch.(Fagaceae)，a shade-tolerant and long-lived species. The observation and study of its reproductive characteristics in the field still remain poorly understood. Based on the methods of Randomized Branch Sampling and observation of labeled individuals, the flowering phenology, flower number and spatial distribution of Castanopsis fargesii Franch. from the Schimeto-Castanopsietum fargesii Association in the Tiantong National Forest Park (TNFP) were studied in this paper. The results showed that the floral bud flushing and inflorescence elongation of C. fargesii emerged at end of April and the trees flowered after leaf emergence. The onset of mass flowering occurred at late May, and its duration within population could last more or less eight days, while the flowering time among individuals experienced less difference. The refore C. fargesiidisplays synchronous flowering. Given the lower precipit ation and gradually increasing temperature during April_May, synchronous flowering and therefore pollination in C. fargesii is a beneficial adaptation. Floral buds commonly located at the first-order branch, which made up 91.92% of all the reproductive branch, nearly 7.07% and 1.01% at the second and the third branch, respectively. There was an apparent difference between the floral bud initiation at the toward-sun reproductive branch and the toward_shade ones within a crown (p<0.01) and the floral bud initiation were 78%±5.7% and 67%±5.7% respectively. Within a crown, there were about 4.89±1.82 panicles per reproductive branch at sun-side and 3.08 ±2.08 at shade-side.The number of male inflorescence of C. fargesii is more than that of the female and male inflorescence occupied 77.9% of the total and female inflorescence 22.1% respectively. There were 67.9±16.7 staminate at one male inflorescence and 26.1 ±5.08 pistillate at one female inflorescence. Furthermore, the flower numbers were male biased during spring censuses and the ratio of staminate to pistillate was about 9.2∶ 1.Mass staminate could produce higher pollen concentration during synchronous period 2.and should increase the pollination efficiency. Therefore flowering in spring exerted 3.great influence on the reproductive output ofC. fargesii.

The monsoon evergreen broad-leaved forest, located in Dinghushan, near the Tropic of Cancer is well protected and has been considered as a climax community in lower subtropical area, with the Castanopsis chinensis-Schima superba-Cryptocarya concinna community as the representative community. The structure, function and dynamics of this community have been well documented in previous studies. Most studies reported that a climax community generally viewed fluctuates spatially and temporally. However, few studies have quantitatively analyzed its changes over time. Therefore, our study aimed to i) monitor the dynamics of the Castanopsis chinensis-Schima superba-Cryptocarya concinna community; ii) examine the fluctuations of plant density and biomass of this community and iii) try to provide information for forest resource managers and policy makers to promote long_term ecosystem sustainability. Based on the plant density and biomass obtained from three consecutive sites (1992 to 1999), a comparative study and paired-samples t-test were conducted. The results demonstrated: 1) plant density generally declined, indicated by 3 979, 3 822 and 3 531 individuals·hm-2 in 1992,1994 and 1999, respectively, with statistical difference between 1994 and 1992 (p<0.05), 1999 and 1992 (p<0.05). Similarly, biomass fluctuated from 293.1 in 1992 to 248.5 t·hm-2 in 1999，with no statistical difference. 2) Plant density and biomass also differed in various DBH (Diameter at Breast Height) classes. Individuals with DBH≤30 cm, including DBH≤10 cm, 10 cm＜DBH≤20 cm and 20 cm＜DBH≤30 cm, differed statistically between 1999 and 1992, 1994 and 1992. Individuals with DBH>90 cm decreased by 50% from 1992 to 1999. The biomass for trees of DBH ≤40 cm and DBH >90 cm did not differ statistically. For middleDBH trees, especially for 40 cm

As a transitional zone from closed forest to alpine vegetation, timberline is sensitive to climatic change in two aspects, fluctuation of its boundaries and changes to its structure. Therefore, the demarcation of vegetation limits and clarification of vegetation patterns of alpine timberline is critical to studies on the response of alpine timberline to climatic change.Mt. Wutai, with a summit of 3 058 m a.s.l., is the highest mountain in North China. It is also one of several mountains which reach the climatically controlled alpine timberline in the temperate broadleaved forest zone in China. Former studies were focused on the vegetation classification of meadows, vertical changes of plant species diversity and micro to meso-scale patterns of the meadow near the summit. Vegetation analysis on a large scale is still essential to understand the characteristics of vegetation near the timberline.Vegetation investigation was made at 10 m elevation intervals on the shady slope and 20-25 m on the sunny slope from the upper forest limit to the mountain summit. A total of 280 relevès on the shady slope and 75 on the sunny slope were made. TWINSPAN was used to do vegetation classification of herbaceous communities,and to show the relationship between distribution of plant communities and environmental conditions was shown using DCA. After classification and ordination of herbaceous communities and analyses of distribution of trees and shrubs, vegetation boundaries of alpine timberline were delimited and vegetation characteristics of the upper forest boundary were clarified in this paper. On the shady slope, alpine timberline ranges from 2 810 m to 3 015 m a.s.l. The timberline is dominated by Larix principis_rupprechtii with Picea meyeri and Betula albo-sinensis. The quantity of cones demonstrates that the regeneration ability of Larix principis-rupprechtii is much better than that of Picea meyeri. On the sunny slope, alpine timberline ranges from 2 605 m to 2 790 m a.s.l.. It is dominated by Picea meyeri with some Larix principis-rupprechtii. 4 herbaceous communities, understory herbaceous layer, meadow at forest edge, subalpine scrubby meadow and alpine meadow, were distinguished by TWINSPAN on both slopes. The herbaceous communities change markedly with altitude. Understory herbaceous layer, meadow at forest edge, subalpine scrubby meadow and alpine meadow occur in sequence from upper closed forest to mountain summit on both shady and sunny slopes. DCA results showed that elevation is closely related to the changes of herbaceous communities, implying a key role of climate conditions in the spatial differentiation of herbaceous communities.

The study was conducted at Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences in Xilingol Region, 43°20′-44°00′N，116°06′ -117°05′E. The goal of the study was to provide some scientificbasis for the restoration of degenerated grassland. Many statistical methods were used to study the succession laws of degenerated steppe of Leymus chinensis after shallow ploughing. After the data over a period of 18 years were analyzed, the results showed that the method of shallow ploughing could improve community density in degenerated steppe of L. chinensis due to overgrazing. The index of diversity and homogeneity of plant species resulted in a open-up parabola for 18 years. The relative density reached maximum at the fifth year, then gradually decreased. It tended to horizon since the fifteenth year. The important value of L. chinensis appeared open-down parabola. The process of community succession can be divided into four stages. The first stage was a community of L. chinensis+annual and biennial synusia (1-3 years after shallow ploughing). The constructive synusia was rhizome grass. Dominant synusia were annual and biennial synusia. The second stage was a community of L. chinensis(4-9 years after shallow ploughing). The constructive synusia was rhizome grass. Dominant synusia were thick grass and rhizome Carex. The third stage was a transition community of L. chinensis+Agropyron michnoi+rosette grasses(10-13 years after shallow ploughing). The constructive synusia was rhizome grass. Dominant synusia were short thick grass and rosette grass. The fourth stage was a community of L. chinensis+A. michnoi, thick grasses, rosette grasses (14-18 years after shallow ploughing). The constructive synusia was rhizome grass. Dominant synusia were thick grass and rosette grass. Through 18 years of restoration, the degenerated steppe was different from the primary communities of L. chinensis. Therefore, it is predicted that succession will continue until a stable community establishes.

The overall weed infestation indexes and density of all weed populations occurring in both the rice_cotton crop rotation and continuous dry-cropping systems of the main cotton belts in Jiangsu Province were surveyed over five years continuously. The succession patterns of weed communities and weed occurrence were studied through statistical analysis in space and time. The results showed that there was a close relationship between the structure of weed community and the level of weed infestation and cropping systems. Under the rice-cotton crop rotation system, the density of hydrophilous weeds such as Echinochloa crusgalli, Alternanthera philoxeroides and Malachium aquaticum was the highest, while that of xerophilous weeds (e.g.，Digitaria sanguinalis) was lowest. However, there was marked linear relationship between abundance and time, with abundance of hydrophilous weeds (e.g.，E. crusgalli) decreasing, and that of xerophilous weeds as (e.g．，D. sanguinalis) increasing with time, when cotton was grown continuously in the fields with the rice_cotton rotation system. After four years continuous cotton growing, the structure of weed community seemed to tend to stable condition. In the cotton fields with cotton cropping system, there were dense density of xerophilous weeds as dominants and no marked change of weed community structure between different years. Moreover, the marked difference of weed community structure and weed density occurred between two different cropping systems. The influence of cropping systems on weed community was much more sign ificant than that of geographical factors.