Aims Our objective is to understand leaf water uptake strategy of desert plants and the relationship between leaf water uptake capability and plant ecological functional types in the southeastern Junggar Basin, China.
Methods We collected or classified (by the inverse of the normal cumulative distribution function) information from 51 species from five plant communities: growth form, life form, leaf texture trait, leaf surface trait, leaf water uptake content, percentage increase in leaf water content, leaf water deficit, specific leaf area and leaf dry matter content. The correlation coefficient and degree of association were calculated between each pair of traits based on information theory. One-way analysis of variance and Fisher’s multiple comparison, if applicable, were carried out on means of different soft ecological functional types at the community scale, for comparing leaf water uptake content and the percentage increase in leaf water content.
Important findings Leaf water uptake content is more appropriate than percentage increase in leaf water for assessing plant leaf water uptake capability. Plant life form is the most rational soft trait to replace hard plant ecological functional ones in studying plant leaf water uptake strategy. There are tradeoffs between aboveground and belowground water uptake strategies and between leaf water consumption and uptake in the desert ecosystem.

Aims In arid and semi-arid environments such as deserts, nitrogen is often the most limiting nutrient for biological activity. Biological soil crusts (BSCs) are an important component of vegetation in the Shapotou region in the Tengger Desert, northern China. However, their importance as contributors to soil fertility such as nitrogen fixation is relatively unknown. This study was conducted to quantify the potential nitrogenase activity (NA) of different types of BSCs in artificial vegetation areas, as well as their responses to variation in moisture and temperature.
Methods Algae crust, lichen crust and moss crust were collected from an artificial vegetation area in the Shapotou region, and were incubated under three gradients of moisture (3, 5 and 10 mm simulated rainfall) and temperature in open-top growth chambers from June to October. The NA was measured using acetylene reduction assay. One-way ANOVA and general linear models (GLM) procedure were applied to compare NA between treatments and interactions between type of BSCs, water and temperature.
Important findings NA for each type of BSC was highly variable, ranging from 2.5 × 10³ to 6.2 × 10 ⁴ nmol C₂H₄·m^-2·h^-1. The NA of algae crust was higher than that of lichen crust and moss crust (2.8 vs. 2.4 and 1.4 × 10 ⁴ nmol C₂H₄·m^-2·h^-1, respectively). The three types of BSCs under the 3 mm simulated rainfall reached the maximum rate of nitrogen fixation, but > 3 mm did not affect NA. Significant negative correlation was observed between NA of all three types of BSCs and temperature. The optimal temperature for NA in algae crust, moss crust and lichen crust were 25-30 °C, 25-30 °C and 20-30 °C, respectively.

Aims Quercus liaotungensis forest, which occurs on shaded, semi-shaded and semi-sunny slopes at an elevation of 1 700-2 300 m, is the main natural secondary forest and zonal climax community in China’s Liupan Mountains. It is essential for forest management to better understand the natural regeneration processes and limiting factors in the restoration of degraded Q. liaotungensis shrubs and secondary Q. liaotungensis forest. Our objectives are to (a) investigate the important ecological processes associated with recruitment and seedling regeneration (seed production, seed bank composition, seed storage and seed/cotyledon predation) and (b) analyze potential bottlenecks limiting seedling regeneration.
Methods We surveyed the seed production of Q. liaotungensis shrubs and soil seed bank composition of secondary Q. liaotungensis forest in Daliang Mountain and Qiuqianjia forest region of Liupan Mountains, respectively. We also investigated the effects of moist sand and natural air-dry storage on seed life-span and the effects of cotyledon predation (by excluding animals) on seedling establishment.
Important findings The percentage of viable seeds of Q. liaotungensis shrubs was 27.51%, and the rate of seed predation/removal (41.51%) was significantly higher than that of other seed types (P < 0.01). The rate of germination and insect infection in soil seed bank of secondary Q. liaotungensis forest was 35.16% and 38.29%, respectively, while only 13.65% of seeds were viable in the soil seed bank. Seed predators played an important role in influencing the density of the soil seed bank by removing and hoarding seeds. Storage in moist sand for 60 d resulted in germination of 96.67% of Q. liaotungensis seeds, and both short-term moist sand and air-dry storage led to accelerated germination timing and enhanced germination percentage and germination index. However, with the extension of the storage period, germination was delayed and germination percentage, germination index and vigor index were decreased. Survival rates of seedlings treated by predator elimination caged seedlings were 80% and 83% in forest gap and under canopy, respectively, while only 25% and 31% of survival rate, respectively, were found for uncaged seedlings, indicating the important role of cotyledons in seedling establishment. The predation rate of cotyledons in forest gaps (85.00%) was higher than that under canopy (71.00%). Although the survival rate of seedlings with cotyledons in forest gaps (6.00%) was higher than that under canopy (15.50%), the survival rate of cotyledon-predated seedlings in forest gaps (18.50%) was similar to that under canopy (18.00%).

Aims Environment varies greatly along the sandy coast of China, as does the crown architecture of Pinus thunbergii. Our objective was to determine the adaptive relationship between the two, including the wind-breakage resistance of the branching pattern, in order to provide guidance for managing coastal protective forests.
Methods We studied three belt transects at 0-50, 200-250 and 400-450 m from the coastline (named transect I, II and III, respectively) in P. thunbergii forest in Lingshan Bay National Forest Park in Shandong from May to September 2009. In each belt transect, we used 20 m × 50 m samples to survey the length and angle of bifurcation, numbers of branches and percentage of dry branches. We imitated natural wind to analyze branch wind-breakage resistance in the different transects.
Important findings The branching pattern of P. thunbergii showed strong plasticity under different environment conditions. Crown architecture was asymmetrical in transects I and II due to the direction of prevailing wind. Average length and angle of bifurcation and branching numbers on the windward side in transect I were significantly smaller than those on the leeward side, while percentage of dry branches was significantly higher on the windward side. This trend weakened gradually with increasing distance from the coastline. In transect III, branch distribution was uniform in each quadrant and there was little difference in average length of bifurcation, average angle of bifurcation, branch numbers and percentage of dry branch among quadrants. Wind was the primary factor influencing the deflection of the branching angle, percentage of dry branches and crown asymmetry. In addition, the wind-breakage resistance of P. thunbergii branching in transect III is higher than that in transect I, and the relationship between imitated wind speed and the force needed was logistic.

Aims The earlier second generation seed orchards of Pinus massoniana have been going to normal blossom stage in China. Our objective was to study the pollen dispersal and constitution of the male parents of open-pollination progenies to provide a theoretical basis for the design and genetic management of advanced generation seed orchards.
Methods We identified 320 open-pollination progenies from 8 clone individuals and 48 clones as candidate male parent using 11 polymorphic SSR loci. CERVUS was used to assign the paternity of each progeny based on maximum likelihood analysis.
Important findings We detected 61 alleles at 11 loci, and the number of alleles ranged from 2 to 11 (average of 5.55). The average observed and expected heterozygosity (H_o and H_e) were 0.428 and 0.433, respectively, and the average polymorphic information content (PIC) was 0.387. Among 320 progenies, 232 progenies (75.50%) could be assigned paternity at a confidence level of 80%. Progenies were produced by each mother tree with 19 male trees. The self-crossing rate reached 1.72% in open-pollination condition, and outcrossing was the primary mating mode. The reproduction contribution varied from 1.00 to 4.00% for most male parents, with an average of 2.17% (produced 5 progenies). Strong negative correlation existed between pollination distance and reproductive success of male parents with the same mating distance. In accord with a normal distribution, the main pollination distance ranged from 0 to 100 m; maximum dispersal distance was 192 m. The pollen contamination ratio was 4.06%. Compared with the north progenies of crown, there was an increasing trend of the mating distance of parents in the south progenies of crown, while there was no obvious trend in the male parent numbers of the south and north progenies of crown.

Aims Quantifying forest soil respiration (R_S) components is vital to accurately evaluate carbon sequestration of forest ecosystems. Our objectives were to determine (1) seasonal variations in R_S and its components of autotrophic (R_A) and heterotropic respiration (R_H) in subtropical forests, (2) the relative contributions of R_A and R_H to R_S in the three subtropical forests and (3) relationships between R_S and temperature and water content.
Methods We used the trenching-plot and infrared gas exchange analyzer approaches to determine R_A and R_H in the soil surface CO₂ flux for monsoon evergreen broad-leaved forest (MEBF) and its early succession communities, coniferous and broad-leaved mixed forest (MF) and coniferous masson pine forest (MPF) in southern China. Rate of R_S was measured twice a month in the hot, humid season (April-September) and once a month in the cool, dry season (October-March). Soil temperature and soil water content were measured at the same time.
Important findings R_S, R_A and R_H varied markedly during the year with high rates in the hot, humid season and low rates in the cool, dry season. R_S rate measured in the trenched plots (R_H) at these forests showed an increasing trend with succession, but the change was not statistically significant. R_S and R_A followed a similar seasonal trend and were highest in MEBF and lowest in MF. Contribution of R_A to R_S was (39.48±15.49)%, (33.29±17.19)% and (44.52±10.67)% in MPF, MF and MEBF, respectively. Repeated measurement ANOVA indicated that soil temperature was the main factor that affected R_S and its components, and there was a significant exponential relationship between them. While there was no significant relationship between soil water content and soil respiration flux, there appears to be a mild inhibition phenomenon. Soil Q₁₀ values increased with succession, whereas autotrophic respiration (R_A) is more sensitive to temperature in all stands.

Aims Knowledge of fine root morphology, anatomy and tissue chemistry is critical to understanding root functions (e.g., longevity), but little is known about these root traits and their relationships in woody plants. We investigated root morphology, anatomy and tissue chemistry of the first five orders in four tropical tree species (Altingia obovata, Cryptocarya chinensis, Elaeocarpus sylvestris and Endospermum chinense) in Jianfengling of Hainan Island, China. Our objectives were to: 1) examine how root morphology (diameter, length, specific root length (SRL) and tissue density), anatomy (cortex thickness and stele to root diameter ratio (V/R)) and tissue chemistry (N and C content) changes with root branch orders and 2) reveal the relationships between anatomical structures and root diameter or tissue N or C concentrations in the four tree species.
Methods Tree roots of the four species were sampled in August 2009, and root samples were sorted into different orders. Root morphology of the first five orders was analyzed by the Win-RHIZO system. Root tissue C and N concentrations in roots of each order were analyzed by the Vario MACRO Element Analyzer. Individual roots in each order were made into paraffin slices stained by safranin and fast green to observe root anatomical structures and to calculate cortical thickness, stele diameter and V/R.
Important findings From the first to fifth order, root diameter, length and tissue density as well as stele diameter and V/R increased, and SRL and cortex thickness decreased in all species. The first two or three orders exhibited primary development with an intact cortex and lower V/R ratio, whereas higher order roots showed secondary development with no cortex and higher V/R ratio. Correlation analysis indicated that cortex thickness can explain 97% of the variations of root diameter and 70% of stele diameter. In all species, tissue N concentration decreased and tissue C concentrations increased with ascending root order. Moreover, C/N ratio in roots was mainly affected by tissue N rather than tissue C concentrations. These results suggest that there are systematic differences in root morphology, anatomy and tissue chemistry among different orders, and root morphology and tissue chemistry are closely linked to root anatomical traits such as cortex thickness in these tropical tree species.

Aims Planting patterns have direct effects on soil microorganisms. Because of different plants and human activities, planting patterns change soil fertility. Our objective is to understand the effects of different planting patterns on soil microbial community structure.
Methods We carried out a long-term field experiment at Jilin Agriculture University that used phospholipid fatty acid analysis method to study the effects of three planting patterns of corn: continuous cropping, non-continuous cropping and uncultivated.
Important findings Different planting patterns affected soil microbial community structure. Continuous cropping of corn had the lowest total phospholipid fatty acids and bacterial phospholipid fatty acids (33.12 nmol·g^-1 and 18.09 nmol·g^-1, respectively). Fungal phospholipid fatty acids and fungi/bacteria with non-continuous cropping were 0.61 nmol^.g^-1and 3.06%, respectively, and were significantly lower than with uncultivated and continuous cropping (p < 0.05). But the ratio of gram positive phospholipid fatty acids/gram negative phospholipid fatty acids was greater with non-continuous cropping. The uncultivated treatment had greater total and bacterial phospholipid fatty acids (42.98 nmol·g^-1 and 24.68 nmol·g^-1, respectively), higher contents of gram positive phospholipid fatty acids and gram negative phospholipid fatty acids, and a lower ratio of gram positive phospholipid fatty acids/gram negative phospholipid fatty acids. Principal component analysis showed that soil microbial community structure with cropping was significant different (p < 0.05) with that of uncultured in first principal component. Non-continuous cropping and continuous cropping were negatively positioned in first principal component with principal component scores of -2.48 and -1.84, respectively. Uncultivated was in a positive position in first principal component with a principal component score of 2.31. Redundancy analysis of soil microbial community structure and environmental variables showed that soil pH and soil-water stable aggragates had the strongest positive correlation with phospholipid fatty acids and that total nitrogen and available phosphorus were also positively correlated with phospholipid fatty acids.

Aims Plant-plant interaction is fundamental in plant ecology. Many studies have examined the effects of environmental factors such as light, nutrients and water on plant-plant interactions, but few have tested the effects of waterlogging. Our objective is to investigate the effects of waterlogging on intraspecific interactions and test the hypothesis that waterlogging can modify the type and intensity of intraspecific interactions.
Methods We grew plants of Alternanthera philoxeroides outdoors at three densities (1, 4 or 16 plants in one pot) and four levels of waterlogging severity (water levels of -20 (no waterlogging), 0, 20 or 40 cm). After three months, plants were harvested and data were collected.
Important findings With increasing plant density or waterlogging severity, growth of A. philoxeroides decreased significantly. However, the effect of density differed greatly under different levels of waterlogging severity. With no waterlogging, the effect of density on growth was negative and the competition intensity was high. With water levels of 0 and 20 cm, the density effect was still negative, but the intensity decreased. With a water level of 40 cm, however, the density effect was positive. Moreover, waterlogging severity significantly affected the relative neighbor effect and its values increased gradually from negative (under no waterlogging) to positive (in 40 cm). The results support a stress-gradient hypothesis and suggest that waterlogging can affect intraspecific interactions. With increasing waterlogging severity, intensity of competition decreases while that of facilitation increases.

Aims Nitric oxide (NO) and hydrogen peroxide (H₂O₂) function as signaling molecules in plants. A role for NO and H₂O₂ in the regulation of many abiotic stress responses, including drought, salt, heat, heavy metal and Al stresses, has been proposed. Our objective was to investigate (a) the Al-dependent accumulation of endogenous NO and H₂O₂ in root tips and (b) the role of exogenous NO and H₂O₂ in alleviating Al toxicity in root tips and root border cells (RBCs).
Methods Seedlings of soybean (Glycine max) ‘Zhechun No. 3’ were divided into two groups for hydroponic and aeroponic cultured experiments. In order to investigate the response of endogenous NO and H₂O₂ in root tips to 50 μmol·L^-1Al, we determined root elongation, Al content in root apexes, endogenous NO and H₂O₂ content and their location in hydroponic cultured experiments. In the aeroponic culture experiments, seedlings were pretreated with exogenous NO and H₂O₂, then RBCs viability as well as the indicators in hydroponic cultured experiments were tested to clarify the role of exogenous NO and H₂O₂ on alleviating Al toxicity in root tips and RBCs.
Important findings Al inhibited root elongation, increased Al content in root apexes and induced endogenous NO and H₂O₂ accumulation with the hydroponic culture. Results of the aeroponic experiments demonstrated that both 0.25 mmol·L^-1NO donor sodium nitroprusside (SNP) and 0.1 mmol·L^-1 H₂O₂ alleviated the inhibitory effect of Al, decreased Al accumulation in root tips and enhanced RBCs viability. The 0.05 mmol·L^-1 NO scavenger cPTIO (carboxy-PTIO) and 150 U·mL^-1 H₂O₂ scavenger CAT (catalase) reversed the alleviating effect. Furthermore, the results indicated that exogenous NO promoted the accumulation of H₂O₂ in root apexes, while exogenous H₂O₂ did not significantly affect NO content in root apexes. All of these results suggested that the rise of NO and H₂O₂ were in accordance with defense response in root apexes and RBCs to Al toxicity in soybean, and the increase of NO may regulate the H₂O₂ production to protect soybean from Al toxicity.