Aims Our purpose was to investigate the response of soluble protein content, lipid peroxidation and antioxidant system in roots of Oryza sativa to different ozone concentrations.

Methods Rice grown in open top chambers in the field were exposed to four ozone concentrations from June 29 to Sept 30, 2007: charcoal-filtered air (CF, 20 nl·L-1), non-filtered air (NF, 40 nl·L-1) and elevated [O3] (75 and 150 nl·L-1, MO and HO). We determined root activity, contents of soluble protein, malonaldehyde (MDA), hydrogen peroxide (H2O2) and ascorbate (ASA), activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD).

Important findings Relative to CF, elevated [O3] (MO and HO) significantly decreased root activity and soluble protein content and increased MDA and H2O2 contents and CAT and POD activities with elongated ozone exposure. However, SOD activity was increased in the early period and decreased in the late period with elevated [O3]. Furthermore, ASA content did not show significant difference between MO/HO and CF, except in the 9th week in MO treatment. With the exceptions of root activity and soluble protein content in late growing season, there were no significant differences in investigated variables between NF and CF during the growing season. All results indicated that elevated [O3] has significant effects on rice roots, including short supply of strong, active roots with prolonged ozone exposure.

Aims Dendrobium officinale is an invaluable Chinese medicinal herb in China that has been threatened by over-collection and habitat deterioration. Understanding the relationship between orchids and mycorrhizae is important for the conservation of orchids. Our aim is to examine the rela-tionship between seedling of D. officinale and mycorrhizae.

Methods The strain of GDB181 was identified by internal transcribed spacer (ITS) sequencing. We inoculated tissue culture seedlings of D. officinale with GDB181 (Epulorhiza sp.) and used ICP-AES to measure the mineral element content of the seedlings. We observed slices of the orchid mycorrhizae under light and electron microscopes.

Important findings Seedlings of D. officinale and the inoculation strain formed symbiosis effectively. The growth of seedlings was promoted by the mycorrhizal fungus. As compared with the control, in-oculated seedlings had 84.8% greater average rate of increase of fresh weight. The mineral contents were elevated except Zn; the contents of B, Si, Fe, Cu and Mn in inoculated seedlings were increased by780%, 533%, 192%, 191% and 128%, respectively. Fungal hyphae entered the exodermis by breaking the velamen randomly and infected other cells continuously by means of penetrating the cell wall. Lastly, the hyphae inhabited the large cells of the cortex and were digested. The cell wall of the cortical cells were distorted and deformed by infection by the hyphae, and many pelotons formed in exodermis and cortex. Pelotons were often found near or encircling the nucleus. The invaded fungal hyphae were surrounded and dissolved by lysosomes partly or completely. With changes of the hyphae from losing cell wall or cytoplasm to remaining cavum, the lysosomes disappeared gradually. More hyphae were dissolved and deformed if there were more lysosomes near them. The cortex cells containing degenerated hyphae were frequently recolonized by hyphae, and the hyphal digestion and the reinfection of cortex cells occurred repeatedly throughout all growing stage of D. officinale.

Aims Global climate changes, including changes in atmospheric nitrogen (N) and precipi-tation, have altered biogeochemical cycling in ecosystems and are expected to affect plant nutrient economy. Our objective was to investigate the potential effects of global climate changes on nutrient use strategy of species.

Methods We studied leaf-nutrient traits in green leaves of Leymus chinensis in relation to N, phos-phorus (P) and water changes using three pot experiments. The N experiment and the P experiment in-volved additions of 0, 0.5, 1, 2, 4, 8, 16, 32, 64 and 128 g-m-2. The water supply experiment involved additions of 3 600, 4 000, 4 500, 5 143, 6 000, 7 200, 9 000, 12 000, 18 000 and 36 000 ml-pot-1, respectively.

Important findings N addition increased specific leaf area (SLA) and N concentration, but did not significantly affect P concentration. In contrast, P addition increased SLA, N concentration and P concentration. Water addition increased SLA, but decreased N concentration and did not affect P concentration. These results suggested that changes in N, P and water availabilities affect green-leaf nutrients, and thus plant nutrient economy and nutrient cycling in the plant-soil ecosystem.

Aims Boesenbergia longiflora (Wallich) Kuntze is a perennial protandrous ginger widely distributed in Asian tropics. It usually grows in crevices of calcareous rocks of limestone monsoon rainforests or in sedimentation soil on the roadside, forming patches in the understory. Its floral longev-ity is 2 days. Flowers are in male stage during the first day and in female stage during the second day of flowering. Autogamy is avoided because two sexual functions are not overlapping in a single flower. Our objectives were to investigate if any other floral mechanism reinforced protandry to avoid geitonogamy and to determine the pollinators and their visiting patterns on the flowers in different sexual stages of different populations.

Methods Flowering phenology was monitored once a week for two years. Floral morphology was studied and compared for three populations of different habitats. Flowering pattern was studied by investigating number of flowering inflorescences and flowers in male or in female stage in four populations and under cultivation. We also investigated natural seed-sets and plant density for different populations. Pollinators were observed in three populations.

Important findings Most of individuals of B. longiflora had only one flowering inflorescence at a time and produced one flower every other day. About 10% of all individuals investigated had male and female stage flowers at the same time, both in four natural populations and under cultivation. The pollination system was generalized with different insects as pollinators, including Apis florae, Bombus sp., Amegilla fimrata, Anthophora plagiata, Amegilla yunnansis, Nmia ellioti and Apis cerana in different populations. Plant and floral sizes did not differ significantly among populations. The flowering pattern of most individuals was one flower every other day, which reinforced protandry and avoided selfing.

Aims According to forest-growth-cycle theory, forest communities are dynamic, mosaic systems composed of patches in different developmental phases. Our purposes were to describe the patch mosaic patterns, quantify the distribution patterns of different patch types and compare the species composition and similarities of different patch types in the forest cycle.

Methods We recognized four distinct growth phases or patch types in Larix chinensis forest on Mt. Taibai, China and studied patterns of patch mosaics and changes in species diversity. We measured and analyzed diurnal changes in light and temperature regimes in different patch types.

Important findings The percentages of different patch types were gap phase 40.3%, building phase 34.0%, mature phase 17.2% and degenerate phase 8.5%. Environmental factors changed significantly, both diurnally and during the forest cycle. Light intensity and soil surface temperature changed more in the gap phase than the other three phases. There were significant differences in tree densities in the forest growth cycle. Average diameter at breast height (DBH), height, basal area, volume per individual and stand volume all increased during the forest cycle. Changes of species diversity with the forest growth cycle showed a wave-like pattern. The theories of natural disturbance and patch dynamics have dramatically advanced our knowledge of biodiversity maintenance.

Aims Cercidiphyllum japonicum, an endangered tree species confined to East Asia, grows mainly in the riparian zones of the Shennongjia mountainous region of central China. Our objectives were to explore regeneration and maintenance mechanisms of C. japonicum populations in montane riparian zones by examining age structures, life tables and radial growth processes, as well as disturbance history.

Methods We surveyed four rivers in the Shennongjia mountainous region and placed 12 quadrats (ranging from 10 m × 20 m to 35 m × 60 m) in riparian zones with sizable C. japonicum populations. In each quadrat, diameter at breast height (DBH) (or basal diameter if tree height < 1.3 m) and height of each tree was recorded. For multistemmed trees, the largest stem was treated as the main stem and the rest as sprouts. Scattered C. japonicum occurring along our routes were also recorded. Cores were extracted from 60 large C. japonicum stems at 1.3 m height and basal discs were taken from 10 young stems at slightly >1.3 m for dendrochronological procedures and subsequent DBH-age regression. Increment sequences >40 years were used for detection of release-events based on a percentage growth change filter.

Important findings DBH of C. japonicum grew consistently rapidly in the first 30 years. There were two release events before canopy accession at about 60 years. Differentiation in DBH and height took place at 90-120 years. After two mortality peaks in ≤20 and 60-100 years, C. japonicum approached and sustained optimum vitality up to 180 years when senescence occurred. Its survivorship curve was generally between Deevey type II and III. Young individuals were abundant. Regeneration, however, was discrete over longintervals. Cohorts with an age range of about 50 years that established in the 1920s and 1970s and culminated in the 1940s and 1990s were remarkably discernable in most local populations. Regeneration by sprouting was predominant and strongly correlated with stand age and community cover. Dates of heavy disturbances (1920s, 1970s and 1990s) roughly corresponded with dates of population recruitment pulses. We suggest that individual growth and developmental characteristics and moderate-to-long-interval disturbances played important roles in driving C. japonicum population dynamics. For short to moderately long periods, C. japonicum can maintain its population due to adequate young individuals, especially sprouts.

Aims Study of niche characters of dominant species of the tree layer in Rhinopithecus roxellana forest habitat can assist in understanding how populations use biological resources, interact and adapt, as well as coevolve with tree-inhabiting primates.

Methods We quantitatively analyzed niche breadth, niche overlap, and niche similarity proportion of the dominant species of Rhinopithecus roxellana habitat in Qianjiaping, Shennongjia National Nature Reserve, Hubei Province and analyzed niche effects of dominant species on the survival of Rhinopithecus roxellana.

Important findings We recorded 255 woody plants from 44 families and 105 genera in a 64 000 m2 quadrat; there were 129 trees from 23 families and 51 genera, 113 shrubs from 22 families and 49 genera and 13 lianas from 9 genera and 7 families. Dominant families included Rosaceae, Lauraceae, Aceraceae, Caprifoliaceae, Fagaceae and Cornaceae. Maximum niche breadth in the arboreal layer occurred in Betula albo-sinensis (5.261), followed by Pinus armandii (4.545), Abies fargesii (4.289) and Betula utilis (3.256). Maximum in the shrub layer occurred in Rhododendron erubescens (2.245), followed by Salix polyclona (2.064), Crataegus wilsonii (1.508) and Malus kansuensis (1.453). Thirty species (11.67% of the plants) had a niche breadth >1; 21 of these species are forage plants, accounting for 10.40% of such plants. Eighteen of these plants account for 74.50% of the importance value of the top 25 species. Niche overlap occurred in dominant species, and seven pairs of these species had an overlap index >0.4. Nearly 83.82% of the species had a niche similarity proportion of 0-0.3. Results suggested that the plant composition of Rhinopithecus roxellana habitat in Shennongjia National Nature Reserve is diverse and the most dominant species are forage plants, but the dominant species are similar, with overlapping niches and strong competition. The survival of Rhinopithecus roxellana would be disadvantaged by changes in the current population structure and plant composition, shortage of grazing plants and decreased habitat. Therefore, it is crucial to protect the current habitat and to construct a more appropriate habitat for Rhinopithecus roxellana in Qianjiaping, Shennongjia National Nature Reserve.

Aims Forest litter contains many components, including remains of leaves, twigs, flowers and fruits, and is important in the transfer of energy and nutrients to the soil and plants by decomposition. Our objective is to study the functions of forest litter by analyzing litter production, nutrient concentration and nutrient return.

Methods We focused on litter production and nutrients by collecting litter from Abies fargesii natural forest and analyzing it in the lab.

Important findings Annual litter production was 5 702.99 kg·hm-2, which approximates litter production in the subtropics. The majority was leaf litter, accounting for 46.00% of total production. The annual pattern exhibited two peaks: October-November 2006 and April-May 2007. The rankings of nutrient concentration and nutrient return were: N>K>Ca>P>Mg. With its large production, leaf litter also had the largest nutrient return.

Aims We studied (a) spatial patterns in typical Leymus chinensis and Stipa grandis steppe communities along two grazing gradients and (b) changes in plant species composition and community structure over a 20-year period in Inner Mongolia, with the objective of understanding grazing-associated grassland dynamics.

Methods Grassland communities were investigated in 1985 and 2005 on 15 field sites, seven along a grazing gradient in S. grandis steppe and eight along a grazing gradient in L. chinensis steppe. Changes in spatial and temporal patterns of these steppe ecosystems were examined and analyzed in association with changes in land use intensity in the region.

Important findings For the S. grandis steppe, five of the seven sites showed a trend towards increas-ing dominance of S. grandis after 20 years, whereas the other two sites showed signs of degradation. For the L. chinensis steppe, six sites exhibited a trend towards restoration of community composition and structure and two sites displayed the reverse trend. Changes in spatial and temporal patterns in both S. grandis and L. chinensis successional communities were mainly due to a shift in grassland management regimes in 1985-2005. Long-term heavy grazing accelerated grassland degradation, and decreased grazing intensity promoted grassland restoration processes. During the past 20 years, especially after 2003, the change in grassland management policy has not resulted in overall grassland degradation in the region; rather it has brought about a more spatially balanced grassland use.

Aims Our objectives were to develop an appropriate procedure for scaling up the sap flow from individual stems to the whole shrub and to the plot and to assess the utility of using sap flow gauges to determine the stand-level transpiration of shrub plantations in a semiarid sandy environment.

Methods Sap flow rates of stems in a 15-year-old Caragana microphylla shrub in Horqin Sandy Land, China were measured using the stem heat balance techniques in June 2006 to determine transpiration of the C. microphylla plantation. The gauge-equipped stems, ranging in basal diameter from 0.4 to 1 cm, were selected on the basis of statistical analysis within the representative sampling plot for determining the “mean stem”. Synchronously, total leaf area of the plant was measured by the basal cross-sectional area method and the leaf area density (LAD) method. We took advantage of the sparse distribution of C. microphylla and the ease of directly measuring LAD for individual shrubs to create a new scaling method based on these direct LAD measurements for shrubs in the study plot. We extrapolated the measurements of water use by individual stems to determine the area-averaged transpiration of the shrubland. The method used for the extrapolation assumed that the transpiration of a shrub was proportional to its leaf area.

Important findings We found daily differences of <14.3% between transpiration estimated with sap measurements and with a weighing lysimeter reference, suggesting that the scaling procedure can be used to provide reliable estimates of transpiration from the shrub C. microphylla in Horqin Sandy Land.

Aims Climate change is expected to cause changes of carbon cycling in forest ecosystems, and prediction research suggests there is dramatic spatial heterogeneity and uncertainty in responses of carbon balance of forest ecosystems to climate change. The goals of our research were to predict and analyze impacts of climate change on the carbon cycling of warm temperate forests in Beijing mountain area in the next 100 years and to understand the heterogeneity and uncertainty on the ecosystem scale with LPJ-GUESS model.

Methods The ecosystem model was used to learn how forest ecosystem productivity and carbon bal-ance change in a long-term time scale and to learn about differences of carbon balance among various ecosystems by comparing ecosystem components of carbon balance. The dynamic vegetation model (LPJ-GUESS), used for the first time in China and driven by A2 and B2 greenhouse gas emission sce-narios of the Special Report on Emissions Scenarios (SRES) of IPCC, projected climate change impacts on carbon balance for three typical warm temperate forest ecosystems (oak, birch and Chinese pine forests) in the Dongling Mountain area of Beijing, China.

Important findings Net ecosystem primary productivity (NPP) and heterotrophic respiration (Rh) will increase in the three forests, and the A2 scenario was associated with larger changes in NPP and Rh than the B2 scenario. Because of differences in species composition among the forests, increases in NPP and Rh were different and changes in net ecosystem exchange (NEE) were different among the forests: oakforest switched from a sink to a small source of carbon, birch forest remained as a smaller sink of carbon, and Chinese pine forest became a larger carbon sink over the next 100 years. Also, carbon biomass will generally increase in the forests by 2100. Comparing SRES A2 with B2, there was larger carbon storage in the relative lower emission scenario (B2). Projected differences in carbon balance among these forests in the same area were more dependent on species composition than climate factors (A2 and B2 scenarios) under future climate change.

Aims Our major objectives were to quantify methane fluxes and variations during growing season and understand key factors controlling methane fluxes in five natural forested swamps.

Methods We measured methane fluxes from natural forested swamps in Xiaoxing’an Mountains from early June to late October 2007, using the static opaque chamber and gas chromatography technique.

Important findings We observed large seasonal variations in methane fluxes in Alnus sibirica swamp, Larix gmelinii-moss swamp and Larix gmelinii-Sphagnum spp. swamp, but smaller variations in Betula platyphylla swamp and Larix gmelinii-Carex schmidtii swamp. Episodic flux was detected in Larix gmelinii-Sphagnum spp. swamp, which greatly influenced methane fluxes during the growing season. Alnus sibirica swamp, Larix gmelinii-moss swamp and Larix gmelinii-Sphagnum spp. swamp were sources of atmospheric methane, but Betula platyphylla swamp and Larix gmelinii-Carex schmidtii swamp were sinks, and the average methane emission rates during the growing season were (56.08 ± 200.38), (15.34 ± 14.89), (0.64 ± 0.88), (-0.88 ± 1.76) and (-0.94 ± 3.00 ) mg·m-2·d-1, respectively. Average methane emission rates were higher with higher water table among the forested swamps, except for Larix gmelinii-Sphagnum spp. swamp. There was a critical point of atmospheric methane source or sink when the water table was at -34.5 ~ -30.8 cm; forested swamps with average water table below this value were atmospheric methane sinks. Effects of temperature on methane fluxes were complex, as temperature may show positive or negative and significant or non-significant correlations. Aboveground biomass of trees may be the best indicator of methane emissions from these forested swamps, because there were strong negative correlations between them.

Aims Much research has focused on the effects of competition and stress tolerance on plant zonation in wetlands, but few studies have explored the role of propagule availability. This study examined the relative importance of niche limitation and species pool limitation in structuring lakeshore plant communities.

Methods We sampled the soil seed banks from the hygrophyte, emergent-plant and submerged-plant zones in a subtropical lakeshore marsh, Longgan Lake, China and used the seedling germination method to examine the density and species composition of seed banks. To assess the effects of species pool and water depth on community establishment, we exposed seed bank samples to three water-level treatments (depths of 0, 25 and 50 cm) and, 45 and 90 days later, compared the species richness and functional groups of the communities that established.

Important findings Species of the seed banks were grouped according to their ability to tolerate or respond to water-depth gradients. The established vegetations varied significantly among sites and treatments. For all three sites, mud-flat and emergent communities established at the 0 water-level treatment, while submerged communities established at the 25 and 50 cm water-level treatments, show-ing that the species belonging to different functional group have different tolerances to water depths and that water depth (niche limitation) was important in shaping plant zonation in freshwater marsh. Only the simplest community developed when the seed bank of the emergent-plant zone was exposed to the 25 and 50 cm water-level treatments, as well as when the seed bank of submerged-plant zone was exposed to the 0 water-level treatment. This shows that community species richness depends primarily on the composition and viability of the seeds in the soil seed bank. These findings suggest that the structure and distribution pattern of the wetland community were determined by both niche limitation and species pool limitation. Their relative importance may depend on the stability of the water regime.

Aims Forest fires are widespread disturbance factors in most forest ecosystems. The structure and function of forest ecosystems have a close relationship with fire disturbance. Exploring the effects of natural fire disturbance is important for understanding forest succession. Our objective was to study the effects of fire disturbance on the structure of tree species in the Kanas tourism district to explain the role of natural fire disturbance in forest dynamics.

Methods We recorded the height and quantity of each tree species in 78 plots of 30 m × 30 m dimensions in the Kanas tourism district. The dates of fire disturbance were determined by fire scars. Data were analyzed using SPSS software.

Important findings Stands with and without natural fire disturbance had different tree structure. Forest seasonal structure and tree composition were affected by natural fire disturbance, and the indexes of tree structure were higher in disturbed plots than that in undisturbed plots. Moreover, the proportion of tree species and tree species richness were significantly different for eight different periods of fire disturbances (p<0.01). Fire disturbance was one of the main factors controlling structure of tree species.

Aims Our objective was to examine the response of soil nitrogen mineralization in natural grassland to N addition, which is pertinent to global N deposition and grassland fertilization management.

Methods We began a long-term N addition experiment in 2000 in typical steppe, Leymus chinensis community, in Inner Mongolia of China, at four N addition levels: control (N0), 5 g NH4NO3·m-2 (N1.75), 30 g NH4NO3·m-2 (N10.5) and 80 g NH4NO3·m-2 (N28). In 2002, soils were collected from two adjacent sites ― A and B (fenced since 1979 and 1999, respectively), with simultaneous fertilization. The soils were incubated under optimal temperature (25 °C) and moisture (60% of water holding capacity (WHC) ) in the laboratory to examine effects of nitrogen addition on the potential net N mineralization in 5 weeks by using a periodically leaching method.

Important findings Nitrogen addition significantly influenced accumulated mineralized nitrogen (Nm) in all plots of the two grassland sites. The highest N addition level (N28) was associated with the lowest Nm, whereas the N1.75 had the highest Nm among the four nitrogen addition levels. Accumulated nitrate nitrogen in N0 and N1.75 was higher than ammonium nitrogen, but that was not the case at the higher N addition levels (N10.5, N28). N addition significantly decreased soil pH value, but no significant correlations were found between Nm and soil pH value, total organic C or total N. N addition causes higher Nm at site A (fenced from 1979) than at site B (fenced from 1999).

Aims Interactive effects of elevated atmospheric CO2 concentration [CO2] and nitrogen (N) deposition on terrestrial ecosystems play an important role in global carbon cycling. Ecosystems in subtropical and tropical areas occupy a large percent of the global biomass, but few studies have been done in these areas. Therefore, our objective was to conduct an experiment to improve our understand-ing of atmospheric [CO2] enrichment and N deposition effects on biomass accumulation and allocation in subtropical and tropical forests.

Methods A model forest ecosystem was constructed of five tree species native to South China: Schima superba, Castanopsis hystrix, Ormosia pinnata, Acmena acuminatissima and Syzygium hancei. The species were exposed to a factorial combination of elevated CO2 and high N deposition in open-top chambers beginning March 2005. There are four experimental treatments, including CN (elevated [CO2] of (700±20) μmol·mol-1 and high N of 100 kg N·hm-2·a-1), C+ (elevated [CO2] of (700±20) μmol·mol-1 and ambient N), N+ (ambient [CO2] and high N of 100 kg N·hm-2·a-1) and CK (ambient [CO2] and am-bient N). Each treatment was replicated two to three times.

Important findings The first 3 years of study indicated that responses of biomass accumulation to different treatments varied among species. Total biomass of S. superba, A. acuminatissima and S. hanceiexhibited significant positive responses to N+ treatment, while biomass of A. acuminatissima and O. pinnata were significantly enhanced under C+ treatment. Biomass accumulation of all species except C. hystrix differed significantly between CN and CK treatments. Furthermore, responses of biomass allocation to treatments differed among species. N+ treatment stimulated aboveground biomass accumulation, with decreasing root:shoot ratio. C+ treatment significantly increased biomass allocation to below-ground biomass in C. hystrix and S. hancei, but enhanced biomass allocation to aboveground biomass in S. superba and O. pinnata. However, CN treatment only resulted in significant belowground biomass accumulation in S. hancei. Responses of the whole community to treatments depended on changes of biomass accumulation and allocation among dominant species and how they performed in the community.

Aims Our objective was to investigate diversity within soil microbial communities and tomato yields and qualities under different soil water and fertilization treatments.

Methods PCR (polymerase chain reaction) with long random primers and intron-splice junction primers were used to study greenhouse soil microbial diversity with tomato cultivated under different treat-ments.

Important findings A total of 182 bands were detected with 6 primer combinations, and 142 (78.02%) of the bands were polymorphic. Soil microbial community diversity was affected by the different soil water contents and fertilizations. Diversity was positively correlated with yields, VC contents and solu-ble protein contents, but negatively correlated with soluble solids contents. The highest soil microbial community diversity index was detected under the treatment of medium water level and high fertilization; the VC contents, soluble protein contents and yields of tomato fruits were significantly higher and the soluble solids of the tomato fruits was lower than those in other treatments. This showed that treatment can enhance the soil microbial community diversity and stability and to improve soil ecological environments and tomato quality.

As a significant cross-discipline of dendrochronology and forest fire ecology, dendropyrochronology is the science that uses tree rings to date and study past and present changes in wildfires, dating the fire scars left in tree rings to determine how often fires occurred in the past. Dendropyrochronology has great advantages in forest fire history research due to its exact dating, high yearly resolution and long temporal span. This paper briefly reviews advances in Chinese and foreign dendropyrochronology. Chinese dendropyrochronology research is still at the beginning stage, while the study abroad mainly focuses on three items. 1) Spatio-temporal regimes of fire history, which mainly includes fire return interval, spatial extent and severity, spatio-temporal interaction, relationship between forest fire occurrence and standing environment, effect of forest fire on species succession, integration of fire scar and other methods to precisely date fire occurrence. 2) Influence of global climate change on fire history. Temperature and precipitation are the main climatic factors influencing fire occurrence. For example, when it is dry in a year after relatively wet years, forest fire is inclined to occur. Fire history is also related to large-scale climatic events. For instance, fire always occurs in the years of transition from El Niño to La Niña, and phase combination of large-scale climatic events is more likely than a single event to lead to fire. 3) Relationship between fire history and human activity and land-use. Wars and increased population easily lead to fire occurrence, while grazing activity can decrease fire occurrence. Forest fire exclusion since the beginning of 20th century has decreased fire occurrence while increasing the possibility of large fire. The prospects of dendropyrochronology research mainly include: scale effect of fire spatio-temporal pattern, driving mechanisms of fire variation on climate change and human activity and development of fire history research methods.

Floral longevity, the length of time that a flower remains open and functional, is an important floral trait that influences plant reproductive success. Recently, there has been a large increase in research on floral longevity. Many advances have enriched our understanding of evolution and ecology of floral longevity. These studies focused on the effects of both pollination and non-pollination factors on variation of duration of flower anthesis, interactions between floral longevity and floral display, and relationships between floral longevity and reproductive assurance. However, no review has been available on these developments. We briefly summarize the development of theoretical studies on floral longevity and review the progress of empirical studies. The life history evolutionary theoretical mode suggested floral longevity was determined by costs of maintaining flowers and the fitness accrual rate, which was supported by many empirical studies. Experimental studies demonstrated that flower senescence is advanced by deposition of pollen grains on the stigma but pollen removal does not significantly affect floral duration. Some of these plants have a minimum longevity during which the flower never abscises. Environmental factors, such as temperature and water availability or humidity, can change costs of maintaining flowers and then change floral longevity. Because of the costbenefit of floral display, plants often adjust floral longevity to alter display size. Floral longevity also can adjust according to resource allocation. Long floral duration can provide reproductive assurance, but may suffer some fitness costs. Although progress has been made, many questions remain and we propose new ideas. For theoretical studies, male and female conflict provides a new perspective to understand the evolution of floral longevity. For empirical studies, we suggestthat evolutionary biologists should pay more attention to male fitness and analyze cost-benefit of floral longevity at the inflorescence level.

Root parasitic plants are a class of special angiosperms that obtain water and nutrients by attaching to the root of a host plant. Their seed germination requires induction of germination stimulants from the host. This review focuses on the distinctive characteristics of seed germination of root parasitic plants and signals known to stimulate this course, as well as their regulation mechanism and biosynthesis pathway. We detail the recognition mechanism between seed and stimulants and the function of signals in establishing the parasitic relationship between root parasitic plants or arbuscular mycorrhizal fungi and hosts. We also discuss present research problems and reflect on the future of this field.

Aims Our objectives were to evaluate the CO2, CH4 and N2O budget for exploring the relationship of source or sink of carbon and nitrogen, to understand seasonal variations of CO2, CH4 and N2O and to explore the effects of temperature and moisture on CO2, CH4 and N2O fluxes in a marsh ecosystem over a growing season.

Methods We analyzed temporal fluxes and factors that influenced CO2, CH4 and N2O fluxes in a Carex schmidtii marsh of Xiaoxing’an Mountains from June to October 2007, using a static chamber and gas chromatograph technique.

Important findings CO2 flux was the highest (99.61%), followed by CH4 (0.39%) and N2O (0.000 7%) in greenhouse gases emission from the marsh. The marsh was a sink of carbon (53.93%) and nitrogen (0.04%). Average CO2, CH4 and N2O fluxes were 487.89, 1.88 and 0.004 mg·m-2·h-1, respectively, and displayed large seasonal variations. The highest emissions of CO2 and N2O were observed in summer (from June 24 to August 14 and from July 14 to August 14, respectively), and the highest emissions of CH4 were in summer and fall (from August 24 to September 24). The CO2 fluxes were significantly correlated with temperature (p < 0.05) (air temperature and soil temperature at 0, 5, 10, 15 and 20 cm), the CH4 fluxes were significantly correlated with air temperature (p < 0.01) and the N2O fluxes were negatively significantly correlated with standing water depth (p < 0.05).

Aim Roadside soils can be polluted by heavy metals from traffic exhaust. These heavy metals can be absorbed by plants, pass through food chains and ultimately harm humans. Our objectives were to investigate spatial distribution, accumulation and contamination of heavy metals (Pb, Cd, Zn, Cr and Cu) in a roadside soil-wheat system and assess the health risk of heavy metals for persons eating the wheat.

Methods We collected samples of soils, wheat seedlings and wheat seeds at different distances from the road edge in the Putian section of Zhengzhou-Kaifeng highway. Soil samples were digested with HCI-HNO3-HF-HClO4. Plant samples were digested with a dry incineration method for Cu, Zn and Cr and the HNO3-HClO4 method for Pb and Cd. Cr, Cu, and Zn in soil and plants were determined by flame atomic absorption spectrometry, while Pb and Cd were determined by graphite furnace atomic absorption spectrometry.

Important findings Heavy metal concentrations in the samples initially increase and then decrease with the distance from the road. Concentrations in soils are higher than that in wheat seedlings, and the concentrations in wheat seedlings are higher than that in wheat seeds. The enrichment coefficient order of heavy metals in wheat seeds and seedlings is Cu>Cd >Zn>Pb>Cr, and the coefficients of the seedlings are higher than those of the seeds. The cadmium health risk of eating wheat seeds is critical, but there are no health risks from copper, lead and zinc in all samples.