Aims Understanding processes underlying spatial distribution of tree species is fundamental to the study of species coexistence and diversity. Our objective was to determine the spatial structure and identify the processes that may generate spatial patterns of trees in a tropical lowland rain forest community on Hainan Island of South China.
Methods Based on four models of point pattern analysis (homogenous Poisson process, inhomogenous Poisson process, homogenous Thomas process and inhomogenous Thomas process), we evaluated the potential contribution of habitat heterogeneity and dispersal limitation to the formation of spatial patterns of tree species in two 1-hm ² stem-mapped forest dynamic plots. The relative importance of each process was assessed at six different spatial scales (< 2 m, 2-5 m, 5-10 m, 10-15 m, 15-20 m and 20-25 m).
Important findings All stems combined revealed a strong aggregation at short distance (≤2 m), and the degree of aggregation decreased with increasing distance. Among the four models simulating tree distribution and patterning, the homogeneous Thomas process was the best-fit model. This result suggested that spatial patterns of tree species in tropical lowland rain forest might be formed by dispersal limitation. The homogeneous Poisson process that models the effect of spatial complete randomness was the second-best model. The inhomogeneous Thomas process and inhomogeneous Poisson process were equally important to forming spatial patterns of trees; they simulated the joint effects of habitat associations and dispersal limitation and modeled heterogeneity, respectively. The proportion of best-fit models differed across different scales. The dispersal limitation was a most important mechanism in spatial patterning of tree species at most scales, while complete randomness process was second in importance. The joint effects of habitat associations and dispersal limitation mainly influenced tree distribution at small scales (0-5 m). However, habitat heterogeneity only affected the distribution at larger scales (15-25 m).

Aims Trade-offs are fundamental to life-history strategies theory, and the leaf size and number trade-off is an important determinant of leaf-size evolution. It also has been proposed that this trade-off is dependent on habitat, but this is not well tested. Our objectives were to test whether the negative, isometric relationship between leaf size and number is conserved in different habitats and to explore the effects of altitude change on the relationship between the leaf size and number.
Methods Leaf area, mass and number and twig mass and stem mass of current-year twigs were measured for 61 deciduous broad-leaved woody species within three altitude-based habitats on Qingliang Mountain, southeastern China. The standardized major axis estimation method and the phylogenetically independent contrast method were used to examine the scaling relationship between leaf size (leaf mass and leaf area) and leafing intensity (twig mass and stem mass) within current-year twigs.
Important findings Significantly negative and isometric scaling relationships between leaf size and leafing intensity were found to be consistent in all three altitude-based habitats, regardless of whether leaf/twig size was expressed as area or mass. However, the intercepts of these relationships significantly decreased with increasing altitude, suggesting that habitats constrain the leaf size that can be supported by a given leafing intensity. The middle-attitude species usually had significant upper shifts along the common slopes relative to the high-altitude species. This suggested that the middle altitude is a more suitable habitat with high nutrients and moderate climate conditions for plants, compared to the high altitude with low temperatures and nutrients.

Aims Dense jujube (Ziziphus jujuba ‘Lizao’) plantations with a spacing of 2 m between trees and 3 m between rows have been established in the semiarid hilly region of the Chinese Loess Plateau. Our objective was to study characteristics of vertical and horizontal root distribution with different tree ages.
Methods Four stands formed a chronosequence 1, 4, 8 and 11 years old. We used the trench profile method to study root distribution. We excavated four trenches 6 m long × 1 m deep × 0.8 m wide for each stand age and measured root intersects as fine (< 1 mm), medium-sized (1-3 mm) and coarse (> 3 mm) roots.
Important findings The number of root intersects increased by tree age (especially fine roots) and decreased with soil depth. 1-year-old tree root intersects were concentrated at 0-40 cm depth, and the other three older tree root intersects were mainly at 0-60 cm depth. There was no significant difference with the fine-root intersects along the horizontal distance from the trunk regardless of tree age. Different diameter root intersects showed no significant difference in the same soil layer (0-20, 20-40 and 40-60 cm) regardless of tree age and horizontal distance from trunk. The efficiency of root distribution under the densely planted pattern was determined to ensure a sustainably high fruit yield. We suggest that jujube roots formed shallow patterns vertically under the water and nutrient management measures, while it formed net patterns when densely planted. Our findings can provide a theoretical basis for efficient root management in this region.

Aims Roots of Panax ginseng are a rare and famous Chinese medicine, in which the total ginsenosides are responsible for biological activities. Due to reduction of the wild resource, it is necessary to artificially cultivate P. ginseng in appropriate agricultural lands. Our objective is to explore suitable planting regions by analyzing the correlation between ginsenoside contents and ecological factors in various agricultural lands.
Methods Three ginsenoside (Rg1, Re and Rb1) contents in roots of five-years-old cultivated P. ginseng from Liaoning, Jilin and Heilongjiang provinces were measured by ultra-performance liquid chromatography (UPLC). Ten ecological factors including temperature, moisture and light at 16 planting sites in China were obtained from the ecological suitability database of the Geographic Information System for Traditional Chinese Medicine (TCM-GIS). They were evaluated by factor analysis to determine the suitable growing regions for P. ginseng. The assessment showed that planting bases in Jilin and Liaoning provinces were the best option for P. ginseng development. Ecological division of the three ginsenosides was assessed according to the results of factor analysis. The regression equation of ten ecological factors and ginsenoside contents was established by partial least-squares regression. Ecological divisions of P. ginseng agricultural lands in China were then classified.
Important findings There was a significant negative correlation between total ginsenoside contents and various temperature parameters, such as active accumulated temperature, mean annual temperature, average temperature in July and average temperature in January, indicating that low temperature is a key factor for accumulation of ginsenosides. Also, ginsenoside contents had weak correlations with moisture factors (e.g., relative humidity and average annual precipitation), geographical factor (e.g., altitude) and light (e.g., annual average sunshine hours). The results of ecological division showed that the best agricultural lands for P. ginseng were large areas of Changbai Mountains, part of Taihang Mountains and Yanshan Mountains.

Aims High near-surface ozone (O₃) has adverse effects on crop growth and yield. Our objective was to analyze the potential impact of O₃ concentration on winter wheat yield, the magnitude and change characteristic of O₃ concentration over a winter wheat field and the relationship between CO₂ flux and O₃ concentration.
Methods The research site was a winter wheat field at the Yucheng Experimental Station (Shandong Province) of the Chinese Academy of Sciences. We observed O₃ concentration with a portable ozone analyzer. We simultaneously measured micrometeorological and radiation factors such as air temperature, humidity, wind speed and global and net radiation. All data were recorded with a high frequency data-logger and averaged every 30 min.
Important findings There was a diurnal change pattern in O₃ concentration, with low and high mean O₃ concentrations at about 7:00 and 16:00, respectively. Mean O₃ concentration was (30.4 ± 20.1) nL·L ^-1(mean ± SE), and the maximum of the 30 min-averaged O₃ concentration was 93.1 nL·L ^-1. During wheat spring growing season (1 March to 31 May, 2011), mean O₃ concentration increased 0.17 nL·L ^-1·d ^-1. Daytime 7-hour and 12-hour mean O₃ concentration (M7 and M12) were 45.7 and 43.1 nL·L ^-1, respectively. Accumulated O₃ concentration above the threshold of 40 nL·L ^-1 (AOT40) was 9.8 μL·L ^-1·h. Accumulated O₃ concentration above 60 nL·L ^-1 (SUM06) was 12.6 μL·L ^-1·h. Weight-corrected O₃ concentration accumulation (W126) was 10.1 μL·L ^-1·h. When O₃ concentration is high (i.e., >60 nL·L ^-1), there is an inverse relationship between CO₂ flux and O₃ concentration. It implied that the threshold of O₃ concentration should be about 60 nL·L ^-1, which is higher than the 40 nL·L ^-1threshold widely applied by European scientists. By using yield-response models to O₃ concentration obtained in open-top chambers (OTC) by European and USA scientists, winter wheat yield is potentially decreased about 5.2%-8.8% at the current O₃ level in Northwest-Shandong Plain.

Aims Our objective was to determine the economic yield of the main stem and the primary (P), secondary (S) and tertiary (T) tillers from the 2nd to 9th nodes on the main stem of rice.
Methods We planted rice (Oryza sativa) variety ‘Shanyou63’ with one plant per hill (100 cm × 50 cm). Treatments consisted of limiting tillers to one main stem node only, on two or four consecutive main stem nodes at lower (L), middle (M) and upper (U) positions with the same 16 panicles and the constituents of each order tiller per plant.
Important findings The main stem leaf number and panicle weight increased as the number of tillering nodes decreased and tillering nodes shifted higher on the main stem. In the treatments with same number of the specific nodes, the average panicle weight of P was U > M > L. The average panicle weight of S was M > U > L in the treatments with one specific node and U > M > L in the treatments with two or four specific nodes. The average panicle weight of T was M > U > L in the treatments with one specific node, M > L > U in the treatments with two specific nodes and U > M > L in the treatments with four specific nodes. Consequently, the average panicle weight of whole tillers was M > U > L and U > M > L for one or two and four specific node(s). These results showed that the economic yield of tillers of L was not necessarily higher than the tillers of M or U, though the tillers of L emerged earlier and had more leaves than the tillers of M and U. Hierarchy (the percentage of mean panicle weight of each order tiller(s) to mean panicle weight of the main stem) of the average panicle weight of tillers increased as the positions of specific nodes shifted higher while the trend was slower as the number of specific nodes increased. These results indicated that in order to compare the productivity of lower, middle and upper nodes on the main stem, number of the tillering nodes and the makeup of tillers must be the same, and without this premise, it seemed that any conclusion was arbitrary.

Aims This research studied effects of light intensity on leaf anatomical characteristics of three alfalfa (Medicago sativa) cultivars (‘Victoria’, ‘Ameristand 201’and ‘Eureka’) with different fall dormancy during overwintering in climatic transitional regions from north to south China. Our objective was to determine leaf anatomical characteristics sensitive to light intensity and correlate fall dormancy and shade tolerance of overwintering alfalfa.
Methods We cultured seedlings of the alfalfa cultivars for 70 days under four light intensity levels: 100%, 43%, 21% and 7% of full natural light intensity. Using the paraffin section method, fluorescence microscopy technique and Image-Pro Plus 6.0, we measured leaf epidermises, mesophyll tissues, and some leaf-integrated characteristics under different shade conditions to examine effects of light intensity on leaf anatomical structures.
Important findings Cuticle thicknesses of lower and upper epidermis and stomatal densities and apertures of the cultivars significantly decreased while thicknesses of upper and lower epidermis increased under with shading. Widths of spongy cell increased and thicknesses of palisade parenchyma, layers of palisade parenchyma and palisade-spongy ratio significantly decreased with decreased light intensity, but thicknesses of spongy parenchyma and widths of palisade cells had different trends among the cultivars. Leaf, mesophyll and midrib thicknesses and cell tense ratio of the cultivars significantly decreased, and vein protuberant degree did not significantly change when the spongy ratio increased significantly with increasing shade. Significant differences in range and plasticity indexes of leaf anatomical characteristics among the cultivars under different shading conditions showed different shade-tolerant mechanisms among them. Pearson correlation analysis showed that stomatal density, thickness of palisade parenchyma, mesophyll thickness, leaf thickness and palisade-spongy ratio were positively correlated with light intensity, which meant that these leaf characteristics may be anatomically sensitive in response to light intensity. ‘Victoria’ had fewer leaf anatomical characteristics correlated with light intensity and also had weaker association to some of these five characteristics than the other cultivars. Results suggested that fall dormancy of alfalfa could be relevant to its shade tolerance during overwintering, and semi-dormancy cultivar of alfalfa has a higher shade tolerance than other cultivars. The order of shade tolerance of three alfalfa cultivars is semi-dormancy cultivar ‘Victoria’ > dormancy cultivar ‘Ameristand 201’ ≥ non-dormancy cultivar ‘Eureka’.

Stable isotope technique has been widely used in ecology research with the increasing concern on global change. Our objectives are to better understand the impacts of nitrogen addition and other environment changes on the nitrogen cycling of terrestrial ecosystem, predict the consequent changes in environmental conditions, and provide a reference for policy making to help ensure the sustainable development of terrestrial ecosystems. Based on the relationship between nitrogen (N) isotope composition (δ ¹⁵N) in ecosystem N status and soil N cycle, we summarized the effects and mechanisms of N input and other environment changes on δ ¹⁵N of plant and soil. Most studies show significant positive relationships between N input and δ ¹⁵N values of plant and soil. Higher N input increases soil N availability, which leads to ¹⁵N enrichment in soil because of mass discrimination during soil N cycling processes. Foliar δ ¹⁵N also will be higher as plants take up the relatively ¹⁵N-enriched soil available N. ¹⁵N natural abundance can be a useful tool for assessing nitrogen saturation and N cycling.

Functional traits influence ecosystem services through their effects on ecosystem attributes, processes and their maintenance. Research on the relationship between functional diversity and ecosystem function can contribute to investigating the mechanism of ecosystem functioning and services supplied, which provides insight on ecosystem services. This study reviewed research on functional traits and framework of ecosystem services, relationship between functional diversity and ecosystem function and application of functional traits in ecosystem services. We proposed a framework of ecosystem services based on functional traits. First, abiotic factors and functional diversity indices that significantly affected ecosystem function should be investigated. Second, (a) quantitative relationships between abiotic factors and functional indices and ecosystem function and (b) quantitative relationships between ecosystem function and ecosystem services should be developed. Third, quantitative relationships between functional diversity and ecosystem services should be constructed. At the same time, community assembly theory and species co-existence mechanism should be incorporated into the investigation of the mechanism relationship between functional diversity and ecosystem function to analyze the mechanism of formation and variation of ecosystem services. The results of ecosystem services based on functional traits can support a scientific basis for the process of decision-making in ecosystem management.