Aims Riparian zones encompass sharp environmental gradients with an unusually diverse array of landforms, habitats and communities. The land cover pattern of the riparian zone was studied in the upper Minjiang River, China, to determine: 1) the land cover pattern and 2) environmental factors affecting the pattern.

Methods Sixty-eight quadrats with 12 classes of land cover were sampled along the main stream of the river. Based on the spatial information and environmental factors, the pattern of land cover was investigated using two-way indicator species analysis (TWINSPAN) and detrended canonical correspondence analysis (DCCA).

Important findings Land cover was classified into high, moderate and low/non-vegetation types. These had different distributions, with the moderate type most predominant. The quadrats were classified into 8 groups, within which each quadrat had similar land cover. Based on land cover, the riparian zone could be divided into three parts: the upper part with mostly high vegetation types, the middle part, which occupied the greatest area, mostly with moderate vegetation types, and the lower part, mostly with the man-made land cover type. Temperature and elevation were the most important environmental factors related to the land cover pattern, followed by precipitation and human distribution. From upper to lower parts of the riparian zone, temperature, precipitation and human activity increase. The overall result is explicitly different land cover patterns in the three parts of the riparian zone. The pattern of dry valley is controlled by the interaction of water and temperature. Ordination was useful in interpreting the land cover pattern of the riparian zone in the upper Minjiang River. Environment factors had a larger effect on this pattern than human factors.

Aims Changes in the biomass of tropical forests play an important role in the global carbon cycle, but the biomass of these forests has been poorly quantified. A strategy for regional biomass estimation should supplement previous surveys with new data. Accurate data are necessary for reducing the uncertainty in the carbon budget of tropical regions.

Methods Biomass and its allocation were estimated for the tropical seasonal rain forest in Xishuangbanna, southwest China. Regression models relating tree biomass to DBH (diameter at breast height, 1.3 m) were developed, and a power-law allometric relationship W=aD^b was used to estimate the tree biomass, where W is the biomass of a tree (kg of leaves, branches, stems or roots), a and b are constants and D is the DBH (cm). Other biomass components were sampled in different quadrats in three 1 hm² permanent research plots: shrubs (ten 25 m² quadrats), herbs (ten 4 m² quadrats), dead wood (the whole plot), large fallen branches (twenty-five 25 m² quadrats) and litterfall (twenty-five 1 m² quadrats). This method was used for estimating above- and below-ground biomass of live and dead plants (trees, seedlings, shrubs, herbs, woody lianas, epiphytes, coarse woody debris and litterfall).

Important findings Total biomass for the three plots was 370.163, 550.119 and 351.442 Mg·hm^-2, with an average of (423.908±109.702) Mg·hm^-2 (95% confidence interval). Living biomass made up 95.28% of the total biomass, with coarse woody debris and litterfall comprising the rest. Most living biomass (98.09%±0.60%) (Mean±SD, n=3) of the seasonal rain forest was concentrated in the tree layer. In the allocation of total biomass, stems accounted 68.33% and roots, branches and leaves made up 18.91%, 11.07% and 1.65%, respectively. The biomass allocation among different DBH classes was concentrated in the middle and largest classes, with large trees (D>70 cm) accounting for 43.67% ± 12.67%. The most important ten species, in terms of biomass, made up 63.43% of the tree layer. Leaf area index (LAI) of the tree layer for the three plots was 5.73, 7.35 and 6.08, with an average of 6.39. Estimated aboveground biomass in our study sites fell within the range of published values for tropical moist forests and was lower than that of Malaysian and Cameroon rain forests, but higher than some neotropical rain forests. In terms of total biomass, Xishuangbanna tropical seasonal rain forest is also higher than moist forest in Brazil.

Aims There is a crucial need in grassland study for a vegetation index (VI)-biomass model simulating steppe biomass based on remote sensing.

Methods Thematic mapper (TM) images (spatial resolution of 30 m× 30 m) for the research area in 2005 and 1991 were rectified so that geometric errors were less than one pixel, then extracted the image of the research region in the soft of ERDAS. We used five vegetation indexes:RVI (ratio vegetation index), NDVI (normalized difference vegetation index), SAVI (soil-adjusted vegetation index), MASVI (modified soil-adjusted vegetation index) and RSR (reduced simple ratio index). They were correlated to plant biomass sampled on the ground at the same time as the TM images. We developed four kinds of regression models: linear, logarithm, second-degree polynomial and cubic polynomial.

Important findings The correlations between sampled biomass and the five VIs were highly significant, with four (NDVI, SAVI, MSAVI, RSR) being positive and one (RVI) negative. Multiple correlation coefficients (R²) of the 15 regression models were >0.6, indicating that a VI-biomass regression model was a simple method to monitor the biomass of steppe grassland. The R² of the NDVI-biomass model was the highest, indicating that it was better suited to simulate the biomass of typical steppe than the other VIs. For TM image, all four kinds of models were significant at the 0.01 level, with the cubic polynomial model as the best to simulate the biomass, followed by the second-degree polynomial, linear and logarithm models. Therefore, the cubic polynomial regression model based on NDVI-biomass was the best model, and was used to simulate the biomass of the research region. Simulated biomass was higher in the east than in the west of the research region and higher in the southeast than in the northwest. Simulated biomass was consistent with sampled biomass in 2005.

Aims Many desert plants show clumped or aggregated distribution patterns, but the adaptive advantage of this spatial pattern is rarely studied. We selected several representative desert plant communities in Sand Lake, Ningxia Autonomous Region and examined the distribution patterns of common desert species to determine adaptation to arid conditions through aggregation. Aggregation was measured by the clump diameter of the caespitose species and the aggregation scale of the scattered species, and relationships between degree of aggregation and soil properties were examined.

Methods We used point pattern analysis to calculate the aggregation scale of scattered species in plots and collected data on soil steady infiltration rate and community characteristics such as species composition and abundance, as well as diameters and central coordinates of individuals or clumps. Soil moisture content was measured in five different depths: top soil, 0-10 cm, 10-30 cm, 30-60 cm and 60-100 cm.

Important findings Caespitose and scattered species have different degrees of aggregation in different communities. Herbaceous caespitose species, such as Achnatherum splendens, usually had a lower degree of aggregation with better site conditions. A. splendens had the smallest average clump diameter in the only plot with a tree canopy that blocked direct solar radiation and reduced evaportranspiration. Other caespitose species exhibited a similar phenomenon, e.g., the clump diameter of Nitraria tangutorum was the largest in a plot where habitat conditions were poor. Scattered species had a higher degree of aggregation in a plot that had a high steady infiltration rate, indicating that high soil permeability could enhance the degree of aggregation. Point pattern analysis indicated a wide range of aggregation of Reaumuria soongoric in plot 3 (0-2 m, 2.3-3.75 m and 4-4.5 m), while another dominant, Kalidium foliatum, was aggregated at 0-5 m. The study indicates that aggregation of desert plants is correlated with habitat conditions. The degree of aggregation tends to be greater in habitats with high solar radiation, hot and dry wind, open stand structure, high soil moisture content and high soil hydraulic permeability. Low aggregation is associated with low transpiration stress and soil water supply. Desert plants could form a micro-habitat by aggregation, reducing evaportranspiration stress and serving as an important adaptive strategy at the community level.

Aims Vegetation and soil surveys were conducted in the summer of 2004 to study the relationship between vegetation types and soil of inter-dune lowland of Otindag sand land. Of 102 vegetation samples collected, 99 were herb-dominated, the others shrub-dominated. We analyzed soils for total nitrogen, soil organic matter, soluble sodium, soluble potassium and pH. Vegetation samples were classified based on species composition and species functional groups. We used detrended canonical correspondence analysis (DCCA) to determine the main environmental factors related to the distribution of plant communities.

Methods The 102 samples were classified into twenty-eight groups dominated by Artemisia annua, A. intramongolica, Bromus ircutensis, Chenopodium acuminatum, A. sieversiana, Oxytropis gracilima, Setaria viridis, A. scoparia, A. frigida, Carex duriuscula, Cleistogenes squarrosa, Agropyron cristatum, Stipa krylovii, Leymus chinensis, L. secalinus, Bromus inermis, Saussurea amara, Potentilla tanacetifolia, Achnatherum splendens, Iris lactea, Salix microstachya, Phragmites australis, Calamagrostis epigejos, Potentilla anserine, Halerpestes ruthenica, Puccinellia tenuiflora, Scirpus tabernaemontani and Suaeda glauca.

Importunt findings The Artemisia annua, A. intramongolica, Bromus ircutensis, Chenopodium acuminatum, A. sieversiana, Oxytropis gracilima, Setaria viridis and A. scoparia associations are mostly distributed on sites often covered by quicksand. The level of the groundwater is low, the lixivium of the soil is neutral and the average soluble K⁺, Na⁺, total nitrogen and organic matter are low. Artemisia frigida, Cleistogenes squarrosa, Agropyron cristatum, Stipa krylovii, Potentilla tanacetifolia, Leymus secalinus, Carex duriuscula and L. chinensis associations are rooted mostly in stable sand, where soil water, organic matter and total nitrogen are high. Bromus inermis, Saussurea amara, Puccinellia tenuiflora, Phragmites australis and Potentilla anserine associations grow in wet sites, where organic matter and total nitrogen are relatively high. Achnatherum splendens, Iris lacteal, Calamagrostis epigejos, Salix microstachya and Halerpestes ruthenica associations are on saline sites that have high groundwater and alkalinity. The Suaeda glauca association occurs in a highly saline lake, where water and salinity levels are very high. The Scirpus tabernaemontani association occurs in a marsh. The first DCCA axis denoted gradients in ground water level (GWL) and factors related to ground water level such as pH, soluble sodium and soluble potassium. The second axis reflected gradients of total nitrogen and soil organic matter. The third axis reflected a pH gradient. Ground water level, pH, soluble sodium, soluble potassium, total nitrogen and soil organic matter significantly correlated with the distribution of plant communities.

Aims Seeds stored in soil are important for plant regeneration and ecological restoration. Seeds are dispersed from parent plants stochastically, and this results in a non-uniform distribution of seeds across the litter and soil. Soil samples must be collected to overcome this variation and to obtain a reasonable richness and density of seeds. However, extracting seeds from soil is time-consuming and studying the germination of seeds from soil samples requires much space. Therefore, it is important to determine a reasonable sample size for soil seed bank studies. However, the relationship between soil sampling area and seeds has rarely been explored in China.

Methods We collected 100 soil samples of 10 cm×10 cm in a Karst forest in central Yunnan. Species and seed density were determined with the seedling emergence method after washing soil samples through 4 and 0.21 mm mesh sieves to eliminate coarse and fine materials, respectively. Soil samples were treated as quadrats and arrayed in a regular but non-contiguous grid to establish a species-area relationship.

Important findings A total of 2 536 seedlings from 69 species (7 trees, 6 shrubs and 56 herbs) emerged from the samples. There were 3-67 seeds from 1-14 species in a soil sample, with an average of 23.4 seeds and 7.1 species. The percentage of samples in which a species germinated ranged from 1% to 90%. The number of total, tree, shrub and herb species had significant quadratic and logarithmic relationships with area. The bases of total species and herb species were large and the slopes of their species-area curves were steep. In contrast, the bases for tree species and shrub species were small and showed little increase. The increase of total species leveled out at 0.15-0.2 m², i.e., 15-20 samples (10 cm×10 cm). This study indicates that 15-20 samples with total surface area of 0.15-0.2 m² can serve as a reference for soil seed bank studies in areas similar to this study. However, the seedling emergence method, even with the total sample area in this study, needs to be improved or replaced to determine the sampling requirement for tree and shrub species.

Aims Fractal theory, a study tool popular in recent years, offers a new means to quantitatively investigate soil structure. Soil structure is the basis of soil fertility, which is the basic property of soil. It can be comprehensively reflected by soil physical, chemical and organism properties, and change of soil structure will result in changes in other soil properties. Fractal features of soil aggregate structure under natural evergreen broadleaved forest and regeneration of artificial systems is rarely studied. We chose to study natural evergreen broadleaved forest and three artificial plantations of Sassafras tzumu, Cryptomeria fortunei and Metasequoia glyptostroboides in southern Sichuan Province. Our objective was to determine a) effects of artificial regeneration on fractal features of soil aggregate structure, b) effects of different plantations on fractal dimension of soil aggregate structure, c) relationships between fractal dimension and soil physical properties, nutrient content and microbe number, and d) use of fractal dimension of soil aggregate structure for evaluating the water conservation, fertility and microbe activity of soil.

Methods Soils were collected from each forest to determine a) fractal dimension of soil aggregate structure using Yang Peiling's approach and b) soil physical and chemical properties and soil microbe number. The relationship between fractal dimension and soil physical properties, nutrient content and microbe number was analyzed with regression analysis.

Important findings Natural evergreen broadleaved forest and artificial regeneration resulted in increased fractal dimension of soil aggregate structure and percent of construction damage, poorer soil physical properties and reduced nutrient content and number of microbes. The higher the content of aggregates, water-stable aggregates and water-stable big aggregates in soil, the smaller the fractal dimension of soil aggregate structure. With wet sieving condition and decreased fractal dimension, the percent of construction damage decreased. There were close relationships between fractal dimension of soil aggregate structure and soil natural water content, bulk density, capillary porosity, non- capillary porosity, original infiltration coefficient, stable infiltration coefficient, content of organic matter, total-N, hydrolysis-N, total-P, available-P, total-K, available-K and the number of bacteria, fungi and actinomyces. Different stands had different effects for maintenance of soil structure, which resulted in changes of soil physical, chemical and organism properties under natural evergreen broadleaved forest and artificial regeneration, and changes of soil aggregate structure had an effect on the value of fractal dimension. This indicates that fractal dimension can be used as a comprehensive quantitative index to evaluate water conservation function, fertility states and microbe activity of soil for natural evergreen broadleaved forest and artificial regeneration. It provides a solid foundation for protecting natural evergreen broadleaved forest, choosing appropriate trees for its artificial regeneration, managing soil after artificial regeneration and choosing trees for converting farmland to forest.

Aims It is an important aspect that the soil organic carbon and nitrogen sequestration or release contribute to the soil fertility and atmosphere CO₂. However, soil organic carbon and nitrogen dynamics has been argued during the process of desertification, the soil organic carbon and nitrogen is rarely explain during the re-vegetation process in the arid desert region. Furthermore, there have some debates about the relation between the soil particle content and soil organic carbon and nitrogen. So, the following questions toe will be sought (a) Does soil organic carbon and nitrogen content during the re-vegetation process differs in time and space? (b) How is there the relation between soil particle content and the soil organic carbon and nitrogen content?

Methods The distributions of particle size fractions, organic carbon and total nitrogen content in soils profile of 0-5 cm (include soil crust), 5-10 cm, and 10-20 cm at different years since re-vegetation were analyzed.

Important findings The results showed that soil organic carbon and nitrogen contents increased with time since re-vegetation but decreased with soil depth. Fine sand (0.1-0.05 mm), silt and clay (<0.05 mm) content showed similar temporal and spatial patterns. However, sand (0.5-0.1 mm) content decreased with time since re-vegetation and soil depth. Soil organic carbon and nitrogen contents positively correlated with the contents of fine sand and silt+clay (p<0.01) and negatively correlated with the sand content (p<0.01).From the point of view of the reversed desertification or re-vegetation process, our results suggest that change of land use can result in carbon sequestration because of the increment of soil protected carbon content in arid desert region. The spatial and temporal changes of soil organic carbon and nitrogen contents as indices for soil fertility may positively feed back to vegetation succession.

Aims This study investigated the pattern of expansion of the exotic Spartina alterniflora for seven years after its introduction into the neonatal Jiuduansha shoals in the Yangtze River estuary, Shanghai. These time-based data are an important first-step in providing a scientific basis for wetland management and biodiversity conservation.

Methods Remote sensing (RS), combined with geographical information systems (GIS) and global positioning systems (GPS), was used to map the distribution of S. alterniflora salt marshes on the Jiuduansha shoals. Findings were checked using field surveys of selected areas.

Important findings S. alterniflora populations expanded from 100 hm² in 1997 to 1 014 hm² in 2004. The pattern of expansion was typical of invasions, i.e., initial colonization, a lag time and rapid population growth and range expansion. In the first year (1997) of planting, S. alterniflora populations colonized the shoals, and about 35 hm² S. alterniflora survived. The period between 1998 and 2000 was a lag time with a mean annual expansion rate <1%. The onset of rapid population growth and range expansion began in 2000, and the annual expansion rate increased to 25%-116%, which exceeded the indigenous species and indicated the strong competitive capability, rapid range expansion and wide ecological niche of S. alterniflora. RS, combined with GIS and GPS, provides a potential tool for monitoring population dynamics and range expansion of invasive species on a large scale. Results of this study indicate this approach can provide timely data for biodiversity conservation of intertidal zones, resource management and sustainable development on coastal regions.

Aims Elodea nuttallii and Hydrilla verticillata have similar morphology. E. nuttallii is an alien aquatic plant introduced into China in 1980s. Both species occupy similar habitat; therefore, they are potential competitors. We investigated: 1) weather inter-specific competition occurred, 2) which species had superior competitive abilities, and 3) what factors influenced competitive results.

Methods Two replacement series experiments were carried out to analyze interspecific competition between E. nuttallii and H. verticillata. In replacement series experiments, the planting densities of the two species were varied but the total density was held constant. The first experiment assessed competitive ability at two levels of soil fertility, and the second investigated the long-term competitive growth of E. nuttallii and H. verticillata.

Important findings E. nuttallii had superior cold resistance and advantages in competing for space-time during winter and spring, so it grew well in the long-term experiment and eventually replaced H. verticillata. In the short-term experiment, H. verticillata formed an upper canopy, giving it advantages in competing for light and occupying the water surface, causing imbalanced competition between H. verticillata and E. nuttallii. H. verticillata was the stronger competitor at both levels of soil fertility, and increased soil fertility could strengthen its competitive abilities; however, it could not replace E. nuttallii and they could coexist in the mixed population. This study suggests competitive abilities are integrated abilities of plants and those morphological traits, life history traits and environmental factors could affect the results of competition. Therefore, investigations of plant interactions should encompass a wide array of factors.

Aims Our objective was to determine foliage biomass and leaf area index (LAI) of four types of conifer plantations in Qianyanzhou Experimental Station in subtropical China.

Methods We developed allometric equations between foliage biomass and stem diameter at breast height (DBH) and obtained specific leaf area (SLA) from data on leaf length, width and weight for different ages and types of leaves from three dominant species: slash pine (Pinus elliotii), masson pine (P. massoniana) and Chinese fir (Cunninghamia lanceolata).

Important findings Allometric equations for foliage biomass of slash pine, masson pine and Chinese fir were W=12.074 1D^{2.151 5}, W=6.972 7D^{2.197 3} and W=5.261 9D^{2.302 7}, respectively. Foliage biomass of slash pine plantation (0.822 kg·m^-2) was the highest among all stands, followed by mixed coniferous plantation (0.679 kg·m^-2), Chinese fir plantation (0.572 kg·m^-2) and masson pine plantation (0.528 kg·m^-2). For each species, SLA of new leaves was larger than old ones, and that of three-needle leaves was larger than two-needle ones. Mean specific hemisurface area of masson pine (8.62 m²·kg^-1) was the largest, followed by Chinese fir (7.91 m²·kg^-1) and slash pine (6.04 m²·kg^-1). Regression equations between stem DBH (D) and mean hemisurface area (LA) for slash pine, masson pine and Chinese fir were LA=0.073 D^{2.151 5}, LA=0.060D^{2.197 3} and LA=0.042D^{2.302 7}, respectively. LAI was 5.03 for slash pine plantation, 4.31 for both masson pine plantation and Chinese fir plantation, and 4.77 for mixed coniferous plantation, all larger than that measured with CI-110 plant canopy digital imager.

Aims Fine-roots (≤2 mm diameter) are important in controlling energy and matter exchange between tree and soil. Fine-root longevity is a critical determinant of fine-root turnover and therefore carbon allocation and nutrients returned to the soil. However, little is known about variation in fine-root longevity in relation to spatial and temporal heterogeneity in availability of soil resources (such as temperature, moisture and nitrogen). How does availability of soil resources affect fine root longevity? Do different tree species, soil depths and root cohorts have different fine-root longevity in the same forest site? To answer these questions it is important to understand the fate of fine roots in soil with heterogeneous resource availability. The objectives of this study were to: 1) compare fine-root longevity between ash (Fraxinus mandshurica) and larch (Larix gmelinii) in the same site, 2) define patterns of fine-root longevity in different soil depths and elucidate the effect of availability of soil resources on fine-root longevity and 3) analyze seasonal changes of fine-root longevity for both species.

Methods Mini-rhizotrons (root observation tubes) were used to estimate fine-root longevity. We established three 20 m×30 m plots in an ash and larch plantation, and installed six clear PVC (polyvinyl chloride) mini-rhizotron tubes (90 cm long × 5.5 cm inside diameter) in each plot in October 2003. From 16 April to 30 October in 2004, video images were collected from the mini-rhizotron tubes at approximately two-week intervals and analyzed with an image analysis system (RooTracker software). We compared differences in longevity between tree species, soil depths and seasonal root cohorts using cumulative survival rate and median root longevity (MRL) of fine roots by Kaplan-Meier methods in survival analysis.

Important findings Cumulative survival rate of fine roots decreased gradually with time. Survivorship curves showed that cumulative survival rate of fine roots in ash was significantly higher than that in larch (p<0.001);MRL was 111±7 d in ash and 77±4 d in larch. Higher fine root mortality was found in 0-20 cm soil, asMRL was 62±11 d for larch and 111±6 d for ash, contrasting with 95±11 d for larch and 124±20 d for ash in deep soil. This study also indicated longer lifespans of fine roots produced in summer (82±6 d for larch) than spring (47±13 d). Similar seasonal pattern was found for ash. Fine-root longevity was different between tree species due to different root genetics, physiology and architecture. High soil temperature and high N content can decrease fine root longevity. In summer, photosynthates are allocated to roots and fine roots grow rapidly and have increased longevity. Our results suggested that fine-root longevity is correlated with genetics of the species, physiological status and soil resource availability.

Aims Gentianopsis barbata displays showy flowers and conspicuous nectaries and has stigma and anthers at different positions (herkogamy) until the fifth day after flower opening. All of these floral syndromes were assumed to favor outcrossing.

Methods We studied pollination biology of this species at Haibei Station on the Qinghai-Tibetan Plateau for three years to test this assumption.

Important findings Contrary to expectation, reproduction in the studied population was mainly through self-pollination. Pollinator visitation was rare, and bagged flowers with anthers set abundant seeds. Both stigma receptivity and pollen viability extended beyond five days. Although stigma receptivity based on seed number decreased after the fourth flowering day, contact of anthers and stigma during floral development resulted in delayed selfing in this species. This delayed selfing retained the floral syndromes and mechanisms for outcrossing, avoided competition between selfing and outcrossing and insured reproduction of G. barbata despite lack of pollinators in arid habitats of the Qinghai-Tibetan Plateau.

Aims The two main methods for estimating CO₂ flux from forests are the eddy covariance micrometeorological method and the ecophysiological component summation method. Eddy covariance is a standard method for long-term, direct measurement of forest CO₂ and is used in studying large-scale terrestrial carbon budgets, while the ecophysiological method can estimate each component (e.g., stem, leaves, branches, roots, as well as soil microbes) of total CO₂ flux of forests. Because forest CO₂ flux study, including eddy covariance measurement, is a recent development in China, it is important to compare results from these two methods for understanding scaling-up of forest carbon budgets. We did a preliminary comparison during a typical month of the strongest sink capacity (June 2002). Our aim was to determine how the methods differed in carbon budget estimation and evaluate implications for future research.

Methods A micrometeorological tower with the eddy covariance system was used to directly estimate net ecosystem exchange of a larch (Larix gmelinii) plantation at Laoshan station (45°20' N, 127°34' E). Ecophysiological measurements by a Li-6400 system were used to measure leaf photosynthesis and respiration of the tree canopy and herbaceous understory, stem respiration, branch respiration and soil respiration. Root respiration, soil microbe respiration and litter respiration were measured by the pre-installed trenched box and litter exclusion method. We converted each photosynthesis and respiration value from an organ-area base to a soil-area base using leaf area index measured by LAI-2000 and stem area index and branch area index estimated by standard tree sampling.

Important findings Energy balance was estimated to be 75% using half-hourly flux data, but improved when 5 days of accumulated data were used, indicating that the eddy covariance method is suitable for this site. In relative cloudy weather (mean photosynthetic active radiation, PAR<400 μmol·m^-2·s^-1), light use efficiency was much higher than on days with a mean PAR>500 μmol·m^-2·s^-1. This may be related to diffuse light on cloudy days. Expressed on a soil area base, gross primary productivity (GPP) of the larch plantation was 20-50 μmol·m ^-2·s^-1 estimated by the eddy covariance method. This value was much higher than the total photosynthetic capacity of dominant canopy leaves of 9.8-23.4 μmol·m ^-2·s^-1 (mean of 16.2 μmol·m ^-2·s^-1); however, it was equivalent to the summation of dominant canopy and understory photosynthesis, indicating the critical importance of understory photosynthesis in the carbon balance of the studied plantation. Ecosystem respiration estimated by eddy covariance on a windy night was 3-9 μmol·m ^-2·s^-1, which is about 50% lower than estimated by the ecophysiological method (14.2 μmol·m ^-2·s^-1). This large discrepancy between the two methods would lead to a large difference in carbon sink estimation. Therefore, methods of estimating respiration need additional study.

Aims The Qinghai-Tibet Plateau is characterized by high elevation, thin atmosphere and high solar transparency. Strong solar radiation is a major stress factors during the growing season. Means of defense and dissipation of strong solar radiation rarely have been explored. Our objective is to determine solar utilization and dissipation characters in two native alpine plants, Anisodus tanguticus and Rheum tanguticum.

Methods We used data obtained from a portable pulse amplitude modulation fluorometer (FMS-2, Hansatech Co., UK) to explain the characteristics of utilization and dissipation and components of non-photochemical quenching.

Important findings Strong solar radiation could cause the photoinhibition of photosynthesis, but this constitutes reversible destruction to PSⅡ reaction center in both alpine plants. Quenching analysis of chlorophyll fluorescence indicated thatA. tanguticus could dissipate more excess excitation energy in PSⅡ antennae through non-photochemistry progress thanR. tanguticum, as the fraction of energy utilized in photochemistry was decreasing. Dark relaxation kinetics analysis showed that “fast" component q_Nf was the main fraction of q_N, then “slow" component q_Ns. “Middle" component q_Nm was lower than q_Ns, but it had an increasing tendency accompanied increased light at noon, which indicated that q_Nm still played an important role in non-photochemical quenching. Diurnal variations of NPQ_S and q_Ns were similar in the two plants; the same as q_Nf, rapidly relaxing quenching NPQ_F was also the main component in non-photochemical quenching NPQ, and both NPQ_F and q_Nf were significantly higher in A. tanguticus than in R. tanguticum (p<0.05). The fraction of light energy absorbed in PSⅡ antennae, which is utilized in PSⅡ photochemistry (P), was significantly lower in A. tanguticus than in R. tanguticum (p<0.01), but the fraction that was dissipated thermally (D) was significantly higher in A. tanguticus than in R. tanguticum (p<0.01). The midday depression of the excess excitation that was neither utilized in photosynthetic electron transport nor dissipated thermally (Excess) showed that there was a light stress acclimation in the two alpine plants. The study indicates relatively lower proportion of P and q_P in A. tanguticus than in R. tanguticum and the higher fraction of D and NPQ and q_N, so actual photochemistry efficiency Φ_PSⅡ was lower in A. tanguticus than in R. tanguticum. Higher level of NPQ and q_N mainly results from the NPQ_F and q_Nf, as well as NPQ_S and q_Ns in A. tanguticus compared to R. tanguticum.

Aims Understanding genetic differences in photosynthetic capacity of different wheat materials evolved from diploid to hexaploid and octoploid is important for breeding and cultivation management, but the physiological basis for late-growth photosynthetic characteristics and grain yield of different wheat evolutionary materials is unclear. This study investigates evolutionary patterns in photosynthetic and fluorescent parameters by examining grain yield during late growth period in different wheat evolutionary materials.

Methods Pot experiment used ten wheat materials: four diploid species (Triticale boeoticum, T. monococcum, Aegilops squarrosa and Secale cereale), three tetraploid species (T. dicoccoides, T. dicoccum and T. durum), two hexaploid cultivars (`Yangmai 158' and `Yangmai 9') and one octoploid species (Triticale). Each pot contained 7.5 kg of sieved soil containing 14.8 g·kg^-1 organic matter, 1.2 g·kg^-1 total N, 82.3 mg·kg^-1 available N, 30.9 mg·kg^-1 available P and 126.7 mg·kg^-1 available K. Before sowing, 0.9 g N, 0.9 g K₂O and 0.36 g P₂O₅ were applied to each pot and topdressing of 0.3 g N was added at jointing stage. Fourteen seeds were sowed and thinned to seven plants in each pot at five-leaf stage. The experiment was arranged in a completely randomized design with ten replications per treatment.

Important findings The photosynthetic rates (P_n) of diploids and tetraploids were higher than that of hexaploids before anthesis, because diploids and tetraploids had higher stomatal conductance (G_s), maximum photochemical efficiency (F_v/F_m) and actual light transformation efficiency (Φ_PSⅡ). However, the P_n of diploids and tetraploids declined faster and became lower than those of hexaploids beginning 5 days after anthesis, except in S. cereale. Moreover, F_v/F_m, Φ_PSⅡ and chlorophyll content (SPAD value) of diploids and tetraploids declined faster, while intercellular CO₂ concentration (C_i) increased, which resulted in non-stomatal inhibition to P_n. Furthermore, the leaf area per plant of hexaploids and the octoploid declined slower after anthesis, as compared with diploids and tetraploids, although diploids and tetraploids had higher leaf area before anthesis. Mean number of spikes per plant of diploids and tetraploids was higher, but the kernels per spike, 1 000 kernels weight and grain yield were lower than those of hexaploids and the octoploid, indicating grain yield was related to the increased kernels per spike and 1 000 kernels weight. This study indicate that improved photosynthetic capacity and duration after anthesis are important physiological bases for enhancing grain yield from increased grain weight during evolution from diploid to current normal wheat.

Aims Excretion of salt by gland had been studied, but the response of salt glands to heavy metals was rarely explored. A hydroponic cultivation experiment was conducted in glasshouse with excretohalophyte to investigate: 1) if salt gland is able to excrete Cd²⁺ ions, 2) extent of Cd²⁺ tolerance for secretohalophyte, and 3) possible mechanisms by which the excretohalophyte is able to resist Cd²⁺ stress.

Methods Branches of Tamarix laxa plants were cut into 15 cm sections and propagated for 3 months. They were then transferred into hydroponic cultivation with a Hoagland's nutrient solution for 20 days and treated with 0, 10, 50, 200 and 500 μmol·L ^-1 Cd²⁺ for 2 weeks to determine the uptake and excretion of Cd²⁺.

Important findings There were no significant differences in the relative growth rate or water content of the plants between the treatment with 10 μmol·L ^-1 Cd²⁺ and the control. When Cd²⁺ levels exceeded 50 μmol·L ^-1, the shoots of T. laxa suffered toxicity. Cd²⁺ excretion through salt glands was detected in all Cd²⁺-added treatments, but the total amount was lower, although the amount of secreted Cd²⁺ from salt gland was increased with increasing of Cd²⁺ levels. Salt glands excreted Cd²⁺, but the secretion plays less important role in Cd²⁺ toxic resistance for excretohalophyte.

Plant traits link environmental factors, individuals and ecosystem structure and functions as plants respond and adapt to the environment. This review introduces worldwide classification schemes of plant functional traits and summarizes research on the relationships between plant functional traits and environmental factors such as climate (e.g., temperature, precipitation and light), geographical variation (e.g., topography, ecological gradients and altitude), nutrients and disturbance (including fire, grazing, invasion and land use), as well as between plant functional traits and ecosystem functions. We synthesize impacts of global change (e.g., climate change) on plant functional traits of individuals and plant communities. Research on plant functional traits is very fruitful, being applicable to research on global change, paleovegetation and paleoclimate reconstruction, environmental monitoring and assessment and vegetation conservation and restoration. However, further studies at large scale and including multi-environmental factors are needed and methods of measuring traits need to be improved. In the future, study of plant functional traits in China should be accelerated in a clear and systematic way.

Aims Davidia involucrata is a rare and endangered plant endemic in China. Research has focused on its geographical distribution, morphological description, population ecology and synecology, introduction, reproduction, etc., but its developmental biology and pollination ecology have rarely been studied. Color has always been considered as an attraction to pollinators. Ecologists formerly studied the relationship between color and pollinator using filters and photography. Flavonoids are one of the most important pigments in flowers, and techniques for extracting and separating flavonoids have been developed; however, there have been no studies of the relationship between flavonoid variation and pollinators' visiting frequency. In this paper, we sought to determine whether flavonoids differ significantly and whether flavonoid variation affects pollination.

Methods We determined flavonoid composition in bracts, stamens and leaves. We also observed the visiting frequency of pollinators.

Important findings With floral development, the general flavonoid content of bracts, stamens and leaves all decreased. There were significant differences between each stage (p<0.001). The visiting frequency of Hymenoptera was high at the gynoecium stage, but no Coleoptera appeared. Flavonoids at the gynoecium stage may function in defense and inducement. Several flavonoid compounds increased and some others decreased, strengthening the contrast between flowers and leaves. It is likely that the contrast serves to attract pollinators.