Aims To ultimately understand of the mechanisms of species coexistence, the Chinese Academy of Sciences, in collaboration with the Center for Tropical Forest Science (CTFS) of the Smithsonian Tropical Research Institute, has recently initiated an ambitious large-scale, long-term forest dynamics and diversity plots network. Following the protocols of the CTFS forest dynamism plots, the China Network has been designed to establish four 20-25 hm² plots along the latitudinal gradient from North to South China. The Changbaishan plot (the CBS plot), the northern most plot of the China Network, is established for the benefit of understanding temperate forest ecosystem. This paper aims to address the community composition and structure of the CBS plot, serving as baseline information accessible for a wide range of future studies.
Methods Following the field protocol of the 50 hm² plot in Barro Colorado Island in Panama, a 25-hm² broad-leaved Korean pine mixed forest permanent plot of 500 m × 500 m was established in the summer of 2004 in Changbaishan. All free-standing individuals with DBH (diameter at breast height) ≥1 cm were tagged, mapped and identified to species.
Important findings There are 38 902 genotype individuals (59 121 individuals with branch), belonging to 52 species, 32 genera and 18 families. Floristic characteristics of the community belong to Changbaishan plant flora, including some tertiary relic species and subtropical species. Three species comprise 52.5% of all individuals, and 14 species comprise 95.2% of all individuals, while other 38 species comprise fewer than 5% of all individuals. The statistics of species abundance, basal area, mean DBH, and important value showed that there are obviously species in the community. The size-class structure of main species in the overstory layer showed nearly normal or bimodal distribution, while the species in the midstory and understory layers showed invert “J" distribution, even “L" distribution. Spatial distribution patterns of the main species, Pinus koraiensis, Tilia amurensis, Quercus mongolica, Fraxinus mandshurica, Acer mono and Ulmus japonica, changed differently with size-class and scales. Meanwhile, spatial patterns of some other species also showed spatial heterogeneity.

Aims Natural secondary poplar-birch forest is one of main secondary forests in Changbai Mountain, which is formed by the restoration after clear-cutting or fire. And it is an important stage in the secondary succession of broad-leaved Korean pine (Pinus koraiensis) mixed forest. A 5 hm² natural secondary poplar-birch forest plot was established in Changbai Mountain Natural Reserve in 2005 in order to gain insights into the processes driving regeneration and succession of the forest and its climax community—broad-leaved Korean pine mixed forest. This paper aims to give some basic information on the forest, including species composition and community structure.
Methods In the plot, all free-standing trees at least 1 cm in diameter at breast height (DBH, 1.3 m above ground) were mapped, tagged, and identified to species, and their geographic coordinates were recorded following a standard field protocol. A total survey station was used to determine the elevations of edge points.
Important findings There are 16 565 genotype individuals (20 101 individuals with branch), belonging to 44 species, 28 genera, and 16 families. Floristic characteristics of the community are very prominent. At the generic levels, North temperate areal-type is the main part of genus areal-types. The statistics of species abundance, basal area, mean DBH, and important value showed that pioneer species Betula platyphylla and Populus davidiana are obviously dominant species. However, the regeneration of the two species is very poor by the analysis of size-class distributions, which indicated that they will quit the stage along with the succession of the community. Some tree species, such as Korean pine and Tilia amurensis, which are main species in broad-leaved Korean pine mixed forest, account for a large proportion in the understory layer. Therefore, they will replace the pioneer species and dominate the overstory layer. Spatial distribution patterns of species were analyzed. For pioneer species and those species that are main species in broad-leaved Korean pine mixed forest, there is no obviously clumped pattern captured. For the midstory and understory species, there are obviously clumped patterns of many species by the observation. There is no obvious correlation between the clumped patterns and the topography.

Aims Mainly distributed in China, subtropical evergreen broad-leaved forest is one of important vegetation types in the world. Here we report preliminary results of floristic characteristics, community composition, vertical structure, size class structure, and spatial structure of Gutianshan(GTS) forest plot.
Methods We established a 24-hm² (600 m×400 m) forest permanent plot from November, 2004 to September, 2005 in mid-subtropical evergreen broad-leaved forest of Gutianshan Nature Reserve, China. Following the standard census procedure of the Centre for Tropical Forest Science (CTFS), all free-standing trees ≥1 cm in diameter at breast height (DBH) in the forest were mapped, tagged and identified to species. We employed software R 2.6.0 to analyze our data.
Important findings The results of floristic characteristics indicates that the tropical elements are more than temperate elements. At family level, the proportion of the pantropic type is the greatest (28.6%), the number of the tropic elements are more than temperate ones (24/13). At genus level,there are 53 tropic genera and 44 temperate ones. As for community composition, there are 159 species, 103 genera and 49 families, 140 700 individuals in total. The evergreen tree species in community are dominant (i.e. 91 species, total relative dominance is 90.6%, importance value is 85.6%, accounts for 85.9% of the total abundance). GTS forest plot is typical mid-subtropical evergreen broad-leaved forest, which displays characteristics of both temperate deciduous broad-leaved forest and tropical rain forest. On the one hand, community composition has obvious dominant species, which is similar to temperate deciduous broad-leaved forest. There are 3 mostly dominant species, Castanopsis eyrei, Schima superba and Pinus massoniana. Large numbers of rare species (59 rare species, equal to or less than one tree per hm²) in the community account for 37.1% species richness, which is similar to tropical rain forest. Vertical structure is composed of canopy layer (63 species), sub-tree layer (70 species), shrub layer (26 species).The structure of DBH size class of all species in the plot generally appears reverse 'J' shape, which indicates successful community regeneration. Spatial distribution of several dominant species, from small to adult tree or old tree, shifts from closer aggregation to looser aggregation, and shows different habitat preference. Finally, we compare the large plot approach with conventional sampling method.

Aims Lower subtropical evergreen broadleaved forest in Dinghushan is one of typical vegetations in Southern China. Its vegetation is protected very well. Because of its geographical location, the composition of its flora is transitional between the subtropical and tropical. A 20 hm² permanent plot of 400 m × 500 m was established in 2005 for long-term monitoring of the biodiversity in the forest.
Methods The plot was established following the field protocol of the 50 hm² plot in Barro Colorado Island (BCI) in Panama. All free-standing trees with diameter at breast height (DBH) at least one centimeter were mapped and identified to species.
Important findings There are 71 617 individuals, belonging to 210 species, 119 genera and 56 families. Its floristic composition is transitional between the subtropical and tropical. The vertical structure of the forest is clear. There are five layers from the top of the canopy to the ground floor, three tree layers (upper, middle and low), one shrub layer and one herb layer, respectively. Based on important value, Castanopsis chinensis, Schima superba and Engelhardtia roxburghiana are the three most dominant species in the upper layer. There are many shade-tolerant and intermediate light-demanding species, such as Cryptocarya chinensis, Xanthophyllum hainanense, Machilus chinensis in mid-layer. Species in low layer are rich and complex, which composition varies a lot. The species-area curve indicates that there is high diversity in the forest and the number of species is close to BCI. There is high proportion of rare species represented by <20 individuals which account for 52.38% of the total number of species. Among these rare species 45% of them lead to be rare by species characteristics, 20% by the floristic transitional nature of the plot, while the rest by disturbances.Size distribution of all individuals shows an invert J-shape, which indicates that the community is in a stable and normal growth status. Size distributions of the dominant species are classified into four types based on their size-class frequencies, unimodal in the top layer, inverse J-shape in middle layer, close to inverse J-shape in middle and low layer, and L-shape in low and shrub layer. Dominant species in different layers are aggregated by the spatial pattern analysis and the spatial patterns of these species in different layers vary with size-classes. However, spatial patterns of them also show complementary within the same size classes, especially in 10-40 cm DBH. The individuals with DBH>40 cm are randomly distributed.

Aims Tropical seasonal rain forest in Xishuangbanna is one of the most species-rich forest ecosystems in China. This area is also one of the biodiversity hotspots for conservation priorities of the world. For the purpose of monitoring long-term dynamics of tree populations, a 20-hm² plot was established in a dipterocarp forest in Mengla Nature Reserve in 2007 by Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences and Xishuangbanna Administration of Nature Reserves, in collaboration with Alberta University, Canada and Tunghai University (Taiwan, China).
Methods The construction technology and field protocol followed those applied in the establishment of the 50 hm² plot in the tropical forest of Barro Colorado Island in Panama, developed by Center for Tropical Forest Science, Smithsonian Tropical Research Institute in 1980. All free-standing trees with diameter at breast height (DBH) ≥ 1 cm were tagged, mapped, measured (girth) and identified to species in the plot. Spatial distribution patterns of four dominant canopy tree species (among different tree size classes) and 12 rare species were analyzed by using a point pattern analysis Ripley's L-function.
Important findings A total of 95 834 free-standing individuals with DBH ≥ 1 cm were recorded in the 20 hm² plot. Of which, 95 498 individuals were identified to species level. This plot included 468 species belonging to 213 genera and 70 families, except for another 336 individuals that could not be identified yet. The flora of plot was mainly composed of species in tropical families. Shorea wantianshuea that dominates the forest canopy was ranked the second in terms of importance value, although it had the largest basal area. Pittosporopsis kerrii, an understory tree species showed the highest abundance (20 918 individuals). The four canopy species had a large number of juveniles and exhibited size structures with reverse-J shape associated with continuously regenerating populations. Young trees (saplings and poles) revealed a clumped spatial distribution, but adults tended to have a random distribution. Most of the 12 rare tree species in the plot also showed aggregated distribution pattern.

A growing need for long-term condition and trend information across natural and anthropogenic landscapes is promoting interest in long-term permanent plot research. In this review, we introduced the 76-year history of management and research on forest dynamics in the Duke Forest, NC. This forest has been intensively studied since the early 1930s and has become a model system for ecological and environmental education and research in the eastern United States. We summarize and assess research in the Duke Forest on forest environment, the current network of long-term permanent vegetation plots, survey protocols, data management procedures, and major research findings from those long-term plot data. We also summarize more broadly the current status of long-term research on the natural dynamics of Piedmont forests of the southeastern United States. Lessons learned from the Duke Forest research site could inform the design of a world-wide, long-term network of research plots for monitoring and assessment of forest dynamics and trends in species composition and biodiversity.

Aims We sought to understand the impacts of climate change on vegetation in Northwest China and the relationship between normalized difference vegetation index (NDVI) and climate elements.
Methods Correlation analyses were done using the GIMMS NDVI data and monthly mean temperature and precipitation data from January 1982 to December 2003. We selected different regions in Northwest China, representing major types of vegetation, such as forest, grassland, oasis, and rain-fed cropland, for detailed study.
Important findings We found strong correlations between NDVI and temperature/precipitation, except for the Gobi and other desert areas. Correlation coefficients of NDVI and temperature are higher than them of NDVI and precipitation in almost all regions, particularly for the Hexi Corridor and most of the Xinjiang area. During the vegetation growth period, temperature has greater effect on the various types of vegetation than precipitation. The forests in the higher latitude of Xinjiang area are most sensitive to temperature. This sensitivity reduces in sequence from forests to oases, grasslands and unirrigated croplands. Grasslands are most sensitive to precipitation. The sensitivity to precipitation decreases from grasslands to forests, unirrigated croplands, and oases. In summer, the NDVI of forest decreased during the last 22 years, especially forest in the eastern portion of the northwest. This was related to decreases of precipitation and increases of temperature in these areas. The NDVI in most grassland increased. The trends were significant for high cold meadow and halophytic meadow. Climate warming is the main reason for grass growth speeding up. For oases, the NDVI increases were the most significant. The trends were the highest in Xinjiang oasis. Climate warming was one of the factors driving increases in NDVI. The impact of human activities, such as oasis expanding, crop structure change and crop varieties on the NDVI variation cannot be ignored. The NDVI interannual change was high and varied among the unirrigated croplands. NDVI had a strong positive correlation with precipitation and a negative correlation with temperature. The temperature increase and the precipitation decrease caused the NDVI decrease in these areas.

Aims Desertification results in ecological and biological diminution of the earth, and can happen naturally or cause by anthropogenic activities. This process especially affects arid and semi-arid regions, such as the Isfahan region, where the spread of desertification is reaching critical proportions. The aim of this study is to use remotely sensed data to review the trend of desertification in the northern of Isfahan, Iran.
Methods Multi-temporal images were employed to evaluate the trend of desertification, specifically the TM and ETM⁺ data of September, 1990 and September, 2001. Geometric and radiometric corrections were applied to each image prior to image processing and supervised classification, and vegetation indices were applied to produce a land use map of each image in nine classes. The land use classifications in the two map images were compared and changes between land use classes were detected over the 11 year period using a fuzzy and post-classification technique.
Important findings The maps and their comparison with false color composite images showed the differences efficiently. With the fuzzy and post-classification method the land use changes were sited on the map. Fuzzy confirmed 53% changed area and 47% unchanged areas in the study region. The results verify the desertification expansion in the study areas. Because of poor land management, agricultural lands converted to desert and abandoned areas, and some marginal pasture lands had to be changed to agricultural land which are desertification spreading according to United Nations Conference on Desertification (UNCOD). Also farmland and pastures have been converted to urban and industrial areas, and the rangelands have been spoiled due to opencast mine excavations. With the mine margins eroding as well as their debris accumulating on the pasture lands, desertification has become worse. Three areas of less-elevated mountains have remained unchanged. This study confirmed that the anthropogenic activities accelerated the desertification process and severely endangered the remaining areas.

Aims Our objectives were to determine the seasonal aspect stages of plant communities at seven sites in the temperate area of eastern China and analyze spatial-temporal variation of the onset dates of seasonal aspect stages and its relation to climatic factors.
Methods We developed a simulating method of phenological cumulative frequency to determine the seasonal aspect stages of plant communities. Basic ideas of the method were to establish a mixed data set composed of the occurrence dates of all phenophases of observed deciduous trees and shrubs for each site and each year, and then calculate the frequency and cumulative frequency of the occurrence dates of phenophases in every five-day period throughout each year and for each site. We used a logistic curve to simulate the phenological cumulative frequency and computed the corresponding dates of maximum changing rate of the curvature as the onset dates of seasonal aspect stages.
Important findings The annual mean dates of greenup and active photosynthesis onsets were delayed with increased latitude, whereas the annual mean dates of senescence and dormancy onsets advanced with increased latitude. Other than the onset dates, the annual mean lengths of greenup, active photosynthesis and senescence periods did not change obviously with latitude but the annual mean length of dormancy period was apparently prolonged with increased latitude. From 1982 to 1996, the regional mean onset date and duration of greenup period significantly advanced at a rate of 0.6 d·a^-1 and lengthened at a rate of 0.7 d·a^-1; the mean onset date and duration of active photosunthesis period were insignificantly delayed and shortened; the mean onset date and duration of senescence period slightly advanced and lengthened; and the mean onset date and duration of dormancy period slightly advanced but significantly shortened at a rate of 0.9 d·a^-1. The onset date of seasonal aspect stages generally correlates better with temperature than with precipitation. The regional mean greenup onset date shows a significantly negative correlation with mean temperature in the current month in a changing rate of 4.3 d·℃^-1, whereas the regional mean active photosynthesis onset date presents a significantly negative correlation with mean temperature during the former second month to the current month in a changing rate of 4.4 d·℃^-1. However, the regional mean senescence and dormancy onset dates do not correlate significantly with mean temperatures.

Aims We tested the neutral theory of biodiversity on subalpine meadows of the eastern Tibetan Plateau that exhibited comparatively complicated species composition. Our objective was to explain the species abundance distribution pattern and the underlying mechanism of biodiversity.
Methods We fit the neutral model to a randomly sampled data set obtained in three different habitats (north-facing slope, level field and south-facing slope) and used three methods to test the fitness of the neutral model to the real community: confidence interval, goodness of fit and diversity index.
Important findings We found no significant difference (p>0.05) between the neutral theory predictions and observed species abundance distributions in the three habitats according to the goodness of fit method. The observed data nearly completely fall into 95% confidence intervals of the neutral model predictions (only one out of 63 species in level field communities and 2 out of 75 species in the north-facing slope communities deviate from the 95% confidence interval). There is no significant difference between the neutral theory predictions and observed species abundance patterns, in which the fit of richness predictions is the best (0.49<p<0.56) and the fitness of evenness predictions is relatively poor. However, for the three different habitats, the fitness of these three indices in north-facing slope communities is perfect and the p-values vary between 0.49 and 0.70, but the fitness in level field communities is poorer (p-value of the Simpson diversity index is less than 0.1). Although the test results of the neutral theory by three different test methods and habitats are somewhat different, we conclude that the neutral model can predict species abundance distribution patterns in the three habitats of subalpine meadow.

Aims Our objective was to determine 1) the phenotypic variation of cone and seed in natural populations and 2) the relationship between phenotypic variation of natural population and different distribution areas in Picea crassifolia.
Methods Field investigation and analysis of the natural distribution of P. crassifolia in Qilian Mountain led to our selection of four cone characters and four seed traits in 10 trees from each of 10 populations. We examined morphological diversity among/within populations based on analysis of eight phenotypic traits. Variance analysis, multi-comparison, correlation analysis and hierarchical cluster analysis were used to analyze experimental results.
Important finding Analysis of variance for all traits showed significant differences among/within populations except for cone dry weight and cone length/cone width. The mean phenotypic differentiation coefficient (Vst) among populations was 27.18%, compared to 72.82% within populations. In different individuals within populations, the CV of cone length, cone width, cone dry weight, cone length/cone width, seed length, seed width, seed length/seed width, 1 000 seeds weight was 10.08%, 5.80%, 19.29%, 9.66%, 8.38%, 15.34%, 6.52% and 13.94%, respectively. Most of the cone and seed traits were positively correlated. The cone dry weight, seed length, 1 000 seeds weight, cone length, cone width were thought to be the most important cone and seed traits that were easy to measured in P. crassifolia. The spatial variation of traits of natural populations was related most strongly to longitude. According to UPGMA cluster analysis, the 10 populations of P. crassifolia could be divided into four groups. This study indicates that there is rich phenotypic variation of cone and seed in natural populations of P. crassifolia in Qilian Mountain and thereby provides theoretical references and basic data for genetic resources conservation, utilization and improvement in P. crassifolia.

Aims An important aim of plant ecology is to identify and quantify key dimensions of ecological variation among species and to understand the basis for them. The leaf size-twig size spectrum is an important dimension that is under development. Our aims were to determine if there is an invariant allometric scaling relationship between leaf size and twig size in subtropical evergreen broad-leaved woody species and to determine what indicates this relationship.
Methods We investigated leaf and stem traits—including leaf and stem mass, individual leaf area, total leaf area, stem cross-sectional area, leaf number and stem length—at the twig level for 68 evergreen broad-leaved species on Meihuashan Mountain in the subtropical zone of East China. We determined the scaling relationships between leaf traits and stem traits at the twig level.
Important findings Twig cross-sectional area has an invariant allometric scaling relationships with leaf mass (SMA slope 1.29), total leaf area (1.23) and individual leaf area (1.18), all with common slopes being 1-1.5. Leaf mass is isometrically related to stem mass and leaf area. This suggests that there would be different metabolic ways between animal body and plant. Species with larger leaves deployed a greater total leaf area distal to the final branching point than smaller leaved species, with this leaf surface made up of fewer leaves per twig, even though the twigs were longer. This might result from the humid climate and weak light in subtropical evergreen broad-leaved forest of this region.

Aims A comprehensive survey on anatomical features of the leaves of Carex moorcroftii and Stipa purpurea, two dominant species in Tibetan Plateau, has been conducted. Quantitative analysis on the relation between ecological factors and leaf structure variation was carried out in order to find out how they are acclimated to environments and whether these two species with different reproductive behavior have different adaptation mechanisms.
Methods A transect was set along the Qinghai-Tibet Road from Xidatan to Yangbajing, with great change in ecological features: altitude from 4 586 to 4 901 m, growing season precipitation from 384 to 202 mm, growing season monthly average temperature from 5.1 to 1.4 ℃, growing season monthly average humidity from 65% to 54%, growing season evaporation from 1 242 to 798 mm, and growing season monthly average wind speed from 2.4 to 4.0 m·s^-1. We collected leaf samples along the transect, embedded them in paraffin, stained embedded sections by astra blue-basic fuchsin, and measured them. Variation coefficient, multi-comparison, correlation analysis and regression analysis were used to analyze structural diversity and the relation between diversity and ecological factors.
Important findings The leaf of S. purpurea curls inward, with lower epidermis outside, and stomata and epidermal hairs appear only on the upper epidermis inside. The leaf of C. moorcroftii usually unfolds like “V” in cross section with well-developed aerenchyma, and stomata and epidermal hairs appear only on the lower epidermis. The leaf structure of both species differs remarkably among populations. Multiple linear step by step regressions revealed for S. purpurea that there are significant linkages between soil available K and the size of mesophyll cells, growing season monthly average cloud coverage and lower epidermis thickness, growing season monthly average cloud coverage and phloem area, growing season monthly average humidity and single vessel semi-diameter, and growing season monthly average humidity and average vessel transverse section area. For C. moorcroftii, there are significant linkage between growing season monthly average lowest temperature and upper epidermis thickness, continentality and thickness of bulliform cells, soil pH value and size of upper epidermis cells, soil available phosphorus and vessel numbers, soil available phosphorus and phloem area, and soil available K and leaf aerenchyma area. Comparison of variance coefficients showed that C. moorcroftii had greater integrative variability than S. purpurea.

Aims Saussurea parviflora is the dominant species on the Qinghai-Tibetan Plateau. This study addresses the following: 1) correlations between S. parviflora's sexual organs and altitude, 2) correlations among S. parviflora's sexual organs, and 3) reasons for S. parviflora's adaptation to this stressful environment.
Methods During the flowering phase in August-September 2005, we collected 11 populations of S. parviflora from different altitudes. We harvested 20 individuals from each population and randomly selected 10 capitula from each individual. We randomly selected 20 flowerlets from different capitula from the same altitude and fixed them in FAA (18:2:2, alcohol:formaldehyde:glacial acetic acid). We measured the length of sexual organs in 20 fully-opened flowerlets and counted pollen in 10 mature flowerlets with undehisced anthers. At the fruiting stage in October 2005 and 2006, we harvested 10 individuals of each population and randomly selected 200 capitula to count the maturation rate. All experimental data were analyzed with the statistical analysis software SPSS11.5.
Important findings There was a strong positive correlation among filament length, anther length and altitude (p<0.01) and a strong negative correlation between pollen number and altitude (p<0.01). Moreover, there were strong positive correlations among 1) style length, length of style ramification and altitude (p<0.01) and 2) style length, length of style ramification, filament length and anther number (p<0.05), and between maturation rate and altitude (p<0.05). Therefore, variation of intraspecific sexual organs under specific environmental condition made S. parviflora adapted to the Qinghai-Tibetan Plateau. With reduced pollen number and insect diversity, abundance and activity with increased altitude, the style ramification lengthened and maturation rate improved. This enhanced the sensitivity to pollinators, ensuring that the decreased pollen was sufficiently spread by them, resulting in increased success of reproduction and dominance in the stressful environment.

Aims Many xerophilous plants in the West Erdos region of Inner Mongolia share the same vegetative reproduction, fissurate growth, which is an important adaptation to drought environments. There are few correlated studies of fissurate growth.
Methods We studied the morphogenesis of fissurate growth of Reaumuria trigyna by sequential slicing and determined changes in the content of ABA, IAA, GA₃ and ZR using ELISA (Enzyme-linked immunosorbent assay).
Important findings Fissurate growth started from the base of stem. During certain phases of growth, the cambium layer of this part was asymmetric and the vessels of secondary xylem became smaller and fewer, while the amount of xylem fiber increased. The constriction formed here. Then the cells gradually disintegrated and the constriction became deeper. One constriction connected with the next one when they extended to the center of the fissurate part. The entire vascular bundle split into many single vascular bundles, and they separated from each other. There was abnormal structure in the fissurate part of R. trigyna, as xylem was divided into several rings by several layers of flat living cells. This could play a role in fissurate growth. IAA and ZT were more concentrated in the fissurate part of transitional plants than in roots, which probably regulated and promoted the growth and splitting of cells in the fissurate part.

Aims Spartina alterniflora, originating from North America, has become an invasive species in Europe and China. Meanwhile, Phragmites australis, a species experiencing 'die-back' in Europe, has invaded coastal ecosystems in North America. Each species is invading the other's native habitat. We studied changes of leaf characters for the two species under different nitrogen and planting densities in the greenhouse to 1) compare the relative competitiveness and invasive capacity of the two species and 2) reveal potential mechanisms that determine successful invasion in different regions.
Methods We grew artificial populations of Spartina alterniflora (S) and Phragmites australis (P) at three different densities in monoculture (S, SS, SSS and P, PP, PPP) and mixed-culture (SP, SPP and PSS), and under three levels of nitrogen (0, 60 and 120 mg·kg^-1). Plants were harvested after 15 weeks, and their leaf characteristics, including area, length, width, thickness and number were measured.
Important findings Nitrogen addition increased leaf area in both species whether in monoculture or mixed-culture (p<0.05), but the change in leaf area of P. australis in mixed-culture decreased with high nitrogen level, which may be due to greater interspecific competition from S. alterniflora. In monoculture, the effects of nitrogen addition on leaf number were greater than on the other leaf traits (p<0.01), while the effects on leaf number (S. alterniflora) or leaf width (P. australis) were greatest (p<0.05) in mixed-culture. Plant densities decreased leaf area of the two species in all treatments (p<0.05). In monoculture, the effects of plant densities on leaf number were greatest (p<0.05). However, in mixed-culture, P. australis mainly reduced leaf width and leaf number of S. alterniflora (p<0.05), while S. alterniflora reduced all the parameters of P. australis (p<0.05). The intensity of competition which S. alterniflora imposed on P. australis was greater than the reverse with low and high nitrogen levels, but this outcome was reversed with medium nitrogen level. At high nitrogen levels, S. alterniflora dominated interspecific competition, with its increased leaf area restraining the leaf growth and reducing the leaf area of P. australis; this may be a mechanism for the successful invasion of S. alterniflora into P. australis populations.

Aims Our objectives were to 1) examine relationships between N and P contents in aquatic macrophytes, water and sediment in Taihu Lake, a eutrophic ecosystem, and 2) explore factors controlling N and P contents in plants in relation to plant characters, such as growth status and developmental stage.
Methods We selected 32 sampling sites in the emerging-plants-free water zone of Taihu Lake and collected plant samples twice with the quadrat method, sampled sediment with column-shaped samplers at different depths, and measured relevant parameters. Concentrations of total phosphorus and total nitrogen of sediment samples with and without macrophytes were measured with the Kjeldahl method and ICP-AES atomic absorption spectrometry, respectively, and those in tissues of aquatic plants were measured by Kjeldahl automatic N analyzer and molybdate-ascorbic colorimetric determination, respectively.
Important findings The N and P contents of tissues of submerged macrophytes were higher than floating-leaved macrophytes, and the nutrient contents were higher in May than in September. Significant correlations were found between the concentrations of N and P in plants and in water, but not in sediments. The N and P contents in plants were highly dependent on plant growth status and developmental stage. Our study provides the insight for the restoration of the eutrophic Taihu Lake ecosystem.

Aims Herbicides applied to rice fields may contaminate nearby aquatic systems through a variety of mechanisms, including drift, surface runoff and leaching, and may have adverse effects on non-target aquatic plants that play a major role in the aquatic ecosystem. The second category of the key protected wild plant, Ceratopteris pteridoides, is frequently observed in paddy fields and adjacent lakes and ponds. Its sexual reproduction phase coincides with herbicide application; therefore, its gametophytes are likely exposed to rice herbicides. The objective of this study is to assess the ecological hazard of herbicide contamination on this aquatic plant.
Methods We cultured spores of C. pteridoides in aqueous solutions of different bensulfuron-methyl concentrations and observed gametophyte growth and sex organ differentiation.
Important findings Bensulfuron-methyl had no effect on spore germination of C. pteridoides. However, it inhibited gametophyte growth with the EC₅₀ of 0.086 μg·L^-1, which was below the reported environment concentration. Bensulfuron-methyl reduced the ratio of hermaphrodite gametophyte and delayed archegonium differentiation of C. pteridoides with the increase in concentration. When bensulfuron-methyl concentration was 10 μg·L^-1, gametophytes ceased growth and did not form archegonia. Therefore, bensulfuron-methyl inhibits gametophyte growth and sex organ differentiation of C. pteridoides at low concentration and may pose a risk to sexual reproduction of C. pteridoides in the field.

Aims This study aimed at better understanding the physiological mechanisms involved in the moderately high temperature treatment, particularly those relating to partitioning of absorbed light energy in some dominant tree species of low subtropical broad-leaf forest in South China, which would affect vegetation succession.
Methods Two-year old saplings of three tree species, Schima superba, Castanopsis hystrix and Cryptocarya concinna, which represent different successional stages in subtropical broad-leaf forest were treated with moderately high temperature (38 ℃). Their photosynthetic rate and chlorophyll fluorescence parameters were measured using a photosynthesis measurement system (Li-COR 6400 and leaf chamber fluorometer) in order to evaluate the effects of moderately high temperature on photosynthesis and partitioning of absorbed light energy under subsequent irradiance.
Important findings Exposure to moderately high temperature caused decrease of photosynthetic capacity of all experimented tree species under the subsequent irradiance, and such decrease was more obvious in sun plant, S. superba and mesophytic plant, C. hystrix than in shade-adapted plant, C. concinna. The fraction of energy consumed by photochemical reaction decreased in the exposed leaves of S. superba, in comparison with those in control at 25 ℃, and a similar response was also found in C. hystrix and C. concinna. The results showed that moderately high temperature could restrict the fraction of absorbed energy utilized in photochemical reaction in leaves treated with moderately high temperature under the subsequent irradiance. The portion of total absorbed light energy that was excessive and the fraction of energy absorbed by the inactive PSⅡ also increased in the exposed leaves at 38 ℃ irrespective of species difference, and the increments were more remarkable in C. concinna than in C. hystrix and S. superba. Different responses to moderately high temperature were dependent on tree species in subtropical broad-leaf forest. The results may mean that the increase of ambient temperature by changing climate would more severely restrict photosynthetic process in the late-successional species, C. concinnia than in the early- or mesophytic species, S. superb and C. hystrix.

Aims Our objective was to determine the effects of elevated CO₂ concentration on photosynthetic characteristics, growth rate, flowering percentage and activity of photosynthetic enzyme in Guzmania 'Denise' and Guzmania 'Cherry'.
Methods We measured P_n, G_s and T_r under various growth conditions using the Li-6400 and used the data to calculate WUE (water use efficiency, WUE=P_n/T_r). We determined chlorophyll and total soluble sugar levels by the method of Zhang & Qu (2003), starch content by the method of Xu et al. (1998) and rubisco and glycolic acid oxidase levels by the method of Ye et al. (1993).
Important findings Under two elevated CO₂ concentrations, net photosynthetic rate increased by 6.24%-31.91% and 11.92%-41.48% over plants grown in ambient CO₂ concentration during 30 d. Elevated CO₂ concentration caused a marked rise in soluble sugar and starch accumulation in leaves, but significantly reduced stomatal conductance and transpiration rate. In addition, Rubisco activity was increased, and glycolate oxidase activity obviously was decreased. Plant height and leaf area increased 6.94%-14.63% and 1.66%-7.06% over plants grown in ambient CO₂. There were 9.71%-20.85% and 2.87%-11.62% increases for (900±40) μmol CO₂·mol^-1. Dry and fresh weights also increased with elevated CO₂ concentration, as was flowering in Guzmania 'Cherry'.

Aims Methane (CH₄) plays an important role in the greenhouse effects. Our objectives were to evaluate the CH₄ budget, understand seasonal variation of CH₄, and explore effects of temperature and moisture on CH₄ flux in a mid-subtropical pine plantation to provide data for estimating the influence of subtropical forest ecosystems on greenhouse effects.
Methods We analyzed CH₄ flux from soils in the Qianyanzhou red earth hill region of China for 16 months from September 2004 to December 2005, using a static chamber-gas chromatograph technique.
Important findings The soil of this type of pine plantation was a sink of CH₄ to the atmosphere as a whole; annual CH₄ flux ranged from 7.67 to -67.17 μg·m^-2·h^-1 with average of -15.530 μg·m^-2·h^-1 under a forest soil treatment and from 9.31 to -90.36 μg·m^-2·h^-1 with average of -16.53 μg·m^-2·h^-1 under a litter-free treatment. CH₄ absorption had similarly seasonal variations with a sequence of autumn > summer > spring > winter for both treatments, but differed in variation ranges and time. The litter-free soil had larger ranges of seasonal variations, maximum CH₄ sink was in October and minimum sink was in March. Meanwhile, the corresponding maximum and minimum CH₄ sinks in the forest soil were in the September and February, respectively, a month earlier than litter-free treatment. Analysis of correlations between CH₄ flux and temperature and moisture showed that CH₄ flux had a significant positive correlation to soil temperature at 5 cm depth and a significant negative correlation to soil water content at 5 cm depth. Partial correlations showed the combined effects of moisture and temperature on CH₄ flux in different seasons. Temperature was a limiting factor for soil absorption of CH₄ during winter (December to February), but soil absorption increased during the rainy season (March to May). From July to August, CH₄ absorption increased with the declining soil moisture but was restricted by high temperature. During the fall (September to November), CH₄ absorption reached the maximum value for suitable combined effects of temperature and moisture. In summary, CH₄ absorption increased with soil temperature and decreased with soil water content, but was restricted by high temperature.

Aims Our objectives are to explore the relationship of leaf area and stand density and determine a convenient way to measure stand leaf area.
Methods Using direct and indirect methods during the growing season (from May to October) of 2004, we measured seasonal variation of the leaf area of tree and shrub species: Robinia pseudoacacia stands with four densities (3 333, 1 666, 1 111 and 833 plants per hm ²), Platycladus orientalis stands with three densities (3 333, 1 666 and 1 111 plants per hm ²), Caragana korshinskii, Hippophae rhamnoides and Amorpha fruticosa. We developed formulas for leaf area by correlating leaf fresh weight, diameter of base branch and leaf area.
Important findings Maximum leaf area and leaf area index (LAI) occurred in September for trees and August for shrubs. There is a significant power relation between leaf area and leaf fresh weight for Robinia pseudoacacia, significant linear relation between leaf area and leaf fresh weight for P. orientalis, C. korshinskii, H. rhamnoides and A. fruticosa, significant power relation between leaf area and diameter of base branch for C. korshinskii, and significant linear relation between leaf area and diameter of base branch for H. rhamnoides and A. fruticosa. After the planted vegetation in Loess hilly-gully region enters into a rapid growth stage, the LAI of R. pseudoacacia stands with different densities converge and LAI is not affected by initial or current density. This was also observed for P. orientalis stands. However, the leaf area of individual trees is negatively linearly related with stand density. Robinia pseudoacacia stands and P. orientalis stands have reached their maximum bearing capacities in the Loess hilly-gully region as a result of limited soil water. Therefore, to improve the quality of individual trees, we recommend stand densities not exceed 833 and 1 111 plants per hm ² for R. pseudoacacia and P. orientalis, respectively. To improve the quality of entire stands, we suggest reducing the density a little.

Aims Our objectives were to 1) explore the feasibility of using individual height and basal diameter as substitutes for age, and 2) determine the influence of using these parameters on survival curve analysis for Pinus armandii and P. tabulaeformis populations in an area damaged by water disaster in the northern Qinling Mountain.
Methods We investigated two dominant species, P. tabulaeformis and P. armandii, which had regenerated after damage by water disaster 17 years earlier. We measured height, basal diameter and age of two species in 6 plots (total plot area was 11 900 m ²). We determined age by counting number of whorls of branches.
Important findings It was infeasible to use basal diameter and tree height in place of age for P. armandii because the relationship to age was an exponential function for both parameters; therefore, we used logarithmic values for basal diameter and tree height. In contrast, the functions were linear for P. tabulaeformis. The survival curves were all linear type with no type differences between base diameter, tree height and factual age. Our study indicates that it is feasible to use basal diameter and tree height as indices for factual age when the relationships of basal diameter and tree height to age are linear. Investigation of relations of age and size and their influential factors is important for the analysis of plant population demography.

Aims It is well known that desert algae play significant and irreplaceable roles in the early formation and structural maintenance of the biological soil crusts. Although species composition and community structure of algae have been widely studied, only a few investigations have been made on the vertical distribution of soil algae in deserts. Our objective was to further reveal species community structure and ecological distribution of desert algae in vertical layers.
Methods We selected typical sand dunes in the Third Site of the southern Gurbantunggut Desert and collected 112 soil samples twice in summers of 2005 and 2006. Using a fixed section from different locations of the sand dunes, we gathered soil samples at serial sections of 0-0.5,0.5-1,1-2, 2-5 cm depth respectively. Algae species were identified by direct microscopic observation and liquid culture observation (dominant species were identified by direct observation). Each sample was checked three times, with ten observations for each sample. Algae biomass was determined by measurement of chlorophyll a.
Important findings Algae species composition differ among soil layers. Dominant algae species are mainly in the 0-2 cm layers and seldom exist in lower layers. The most dominant algae species in most layers is Microcoleus vaginatus. In 1-2 cm layers of interdune and windward, Oscillatoria pseudogeminata is the most dominant. In addition, Synechocystis crassa, Navicula sp. and Amphora ovalis are more dominant than other algae. Except for the top of sand dunes, algae biomass in different layers exhibited highly significant differences (p<0.01) at other locations. Algal biomass dramatically decreased with soil depth from the surface to lower levels. At the same soil depths, algae biomass declined from the inter dune position to the windward and leeward, to the top, with differences highly significant (p<0.01) or significant (p<0.05).

Aims Our objectives were to measure the soil microbial biomass carbon (SMB C), soil microbial biomass nitrogen (SMB N) content and soil microbial activity, and determine the relationship between these parameters and other soil properties (including organic carbon, total nitrogen content and water content) in montane forest (dominated by Picea crassifolia), steppe and alpine meadow ecosystems in Qi Lian Mountains, China.
Methods We measured SMB C and SMB N content using fumigation-incubation method and soil microbial activity using substrate-induced respiration.
Important findings The SMB C content under forest was 60% and 120% higher than under steppe and alpine meadow, respectively, and it was 40% higher under steppe than alpine meadow. The SMB N content was 64% and 111% higher in 0-5 cm soil depth under forest than alpine meadow and steppe, respectively, and it was 29% higher under alpine meadow than steppe. Also, it was 7% and 191% higher in 5-15 cm soil depth under forest than steppe and alpine meadow, respectively, and it was 171% higher under steppe than alpine meadow (p<0.05). The ratio SMB C (SMB C-to-SOC (Soil organic carbon), 0.4%-2.8%) was 32% higher under forest and steppe than alpine meadow, and the ratio of SMB N (SMB N-to-total soil N, 0.5%-2.8%) in 0-5 and 5-15 cm soil depths was 150% higher under forest and steppe than alpine meadow (p<0.05). Soil microbial activity in 0-5 or 5-15 cm soil depth was 26% higher under forest or alpine meadow than steppe, and in 15-35 cm soil depth it was 28% higher under forest than steppe and alpine meadow (p<0.05). The SMB C and SMB N content was positively correlated with SOC content, and the SMB N content or its ratio was also positively correlated with the SMB C content and its ratio (r²>0.30, p<0.000 1). The SMB N content, SMB C ratio, SMB N ratio and microbial activity were significantly negatively correlated with soil pH. The SMB C content, SMB N content and their ratio and microbial activity were positively correlated with soil water content.

Aims Optimization of resource structure is important for improving the yield of intercropping systems. Our objective was to clarify the contribution of above- and below-ground interactions to the intercropping advantage.
Methods We employed a micro-plot experiment and root barriers in a wheat-maize intercropping system with or without maize plastic sheet mulching.
Important findings Non-plastic sheet mulching wheat-maize intercropping system has a yield advantage with land equivalent ratios (LERs) for grain yield and biomass of 1.30 and 1.29, respectively. Plastic sheet mulching with maize can significantly increase the yield advantage of intercropping, with LERs for grain yield and biomass of 1.41 and 1.40, respectively. There is increased nitrogen, phosphorous and potassium uptake in the non-plastic sheet mulching wheat-maize intercropping and with plastic sheet mulching with maize. In the non-plastic sheet mulching intercropping system, the relative contribution to the intercropping advantage is 75% above-ground and 25% below-ground, but in the plastic sheet mulching intercropping system it is 67% above-ground and 33% below-ground. The relative contribution of above- and below-ground interactions to nutrient advantage are 67% and 33% for nitrogen and phosphorus and 50% and 50% for potassium, respectively, in non-plastic sheet mulching intercropping; however, plastic sheet mulching with maize can increase the below-ground contribution to nitrogen and phosphorus advantage in the intercropping (there is no significant influence to potassium advantage). Intercropping advantage can be obtained by crop matching and controlled by plastic sheet mulching. Plastic sheet mulching with maize can significantly increase yield advantage, nutrients absorption advantage and the below-ground contribution.

Aims Row spacing is a cultivation technique used for many field crops, but not wheat, for which traditional row spacing of 20 cm is used regardless of spike-type wheat cultivar. Our objective was to examine the effects of row spacing on canopy structure, its microclimate and yield in heavy-ear winter wheat, Triticum aestivum.
Methods We conducted a field experiment on the farm of National Engineering Research Center for Wheat, Zhengzhou, China, using heavy-ear winter wheat cultivar 'Lankao Aizao 8'. Three row spacing treatments (15, 20 and 30 cm) were used in a randomized complete block arrangement with three replications.
Important findings Leaf area index decreased and canopy openness increased with increased row spacing. Moreover, light interception at different layers, extinction coefficient, and relative humidity decreased, canopy temperature at each layer increased, and the spread of carbon dioxide was unchanged. Yield could be increased by reducing row spacing to have an even plant-to-plant distribution that could weaken competition. Our finding that 15 cm row spacing was beneficial to canopy structure and yield indicated that heavy-ear winter wheat cultivar 'Lankao Aizao 8' should not be planted in conventional 20 cm row spacing.

Aims Water stress is one of the most important ecological factors affecting yield and quality of rice (Oryza sativa), and osmotic adjustment is the main mechanism for the crop to adjust to drought. Our objective was to elucidate the effects of water stress on osmolytes at different growth stages in leaves and roots of rice.
Methods We used the rice variety Feng-Hua-Zhan grown in pots to study the effects of water stress on inorganic and organic osmolytes in leaves and roots. Water was withheld 15 d at the growth stages of tillering, panicle differentiation, heading and filling.
Important findings Water stress significantly decreased leaf water potential. Organic osmolytes including soluble sugar, proline and free amino acid and inorganic osmolytes including K⁺ and Mg²⁺ in leaves and roots increased significantly after drought treatment at different growth stages. These osmolytes could be reduced to normal levels after re-watering at the tillering stage, but not at the panicle differentiation and heading stages. Osmolytes accumulated to higher levels after drought treatment at panicle differentiation and heading stages than at other growth stages, and organic osmolytes accumulated to higher levels than inorganic osmolytes in the different treatments. The order of osmotic adjustment (OA) ability at different growth stages was: heading, panicle differentiation, filling and tillering. The OA in roots was lower than but positively correlated to OA in leaves. Roots were more sensitive and had a more rapid response to water than did leaves. The order of contribution for osmotic adjustment in leaves and roots with different osmolytes was: K⁺ > Ca ²⁺ > soluble sugar > Mg ²⁺ > free amino acid > proline.

We summarized the research on theory and method related to maximum size-density rules. There are two main theories, Yoda's 3/2 power law based on Euclidian geometry and West, Brown and Enquist's fractal scaling rules (WBE model). However, both are based on static analysis rather than dynamic competition between plants, which is the direction attempted by recent researchers. In spite of this, some researches have not eliminated the reliance on these untenable assumptions, such as the instead of whole population by the average plant size. Further work is needed. In addition, there is ongoing debate regarding assumptions, mathematical deduction and original data points used for estimating parameters. Each model is formulated based on special situations and assumptions, it is not all-purpose; therefore, these models can be coupled, depending on practical situations. Moreover, various methods are used for estimating parameters because of different perceptions and criteria. Therefore uniform criteria need to be established.

Endophytes, especially asexual and systemic endophytes in grasses, are generally viewed as plant mutualists based on the action of their alkaloids. Enhanced drought tolerance is a well-known benefit of endophytic infection in tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne), and increased tolerance to other environmental stresses like heat, low light and low soil fertility has also been reported. Three endophyte life histories have been recognized: symptomatic of life cycle where the fungus horizontally transmits by meiotic ascospores which induce sterilization of the host, asymptomatic life cycle where the fungus remains internal and there is vertical transmission by plant seeds throughout the season and a mixed mechanism of life cycle, which can be plastic. Neotyphodium endophytes are closely related to sexual Epichloı species, which are the grass choke pathogen, and likely evolved either directly from sexual Epichloı species or by interspecific hybridization of distinct lineages of Epichloı and Neotyphodium. In vertical transmission, only one fungal genotype is transmitted to the seed progeny, which are usually produced by outcrossing in the host. The same fungal genotype is present in seeds that are genetically variable, and the high level of genetic specificity is probably tied to genetic incompatibility constraining the diversity of successful genotype-genotype combinations of the systemic seed-borne endophytes and the host grasses. The defensive mutualism depends on a certain grass-endophyte genotype combination and environmental conditions. Recent studies have suggested that there is a mutualism-parasitism continuum for the symbiosis between asexual endophytes and grasses and that the symbiosis existing in native grass-endophyte symbionts has a more complex mechanism than in agricultural ecosystems. The host-specific endophyte, with negligible biomass, may alter plant community structure, reduce plant diversity and control food-web structure by disrupting the transfer of energy from plants to upper trophic levels. Future studies should focus on how ecology and genetics interact to shift fungal life history traits between the extremes of sexuality and asexuality and antagonism and mutualism. These questions require a more comprehensive understanding of the genetic basis and phenotypic plasticity of traits of the grass-endophyte interactions.