[Effects of simulated precipitation changes on plant community characteristics of wetland in the Yellow River Delta, China]. / 模拟降雨量变化对黄河三角洲湿地植物群落特征的影响.

Under the changing climate scenario, changes in precipitation regimes are expected to alter soil water and salinity conditions, with consequences on the characteristics of plant community in estuarine wetland. Here, we used a six-year (2015-2020) precipitation manipulation experiment to examine how plant community characteristics responded to precipitation changes in the Yellow River Delta. The results showed that soil electrical conductivity significantly decreased, while soil moisture significantly increased with increasing precipitation. Precipitation changes altered plant community composition. Increased precipitation reduced the absolute dominance of Suaeda glauca and Suaeda salsa, but increased that of Triarrhena sacchariflora and Imperata cylindrica. Shannon index and Margalef richness index of plant community significantly increased with increasing precipitation. Compared with the control, both decreased and increased precipitation decreased the plant community abundance, frequency and coverage. The treatment of 60% increased precipitation significantly decreased plant community frequency by 54.9%, while the 60% decreased precipitation, 40% decreased precipitation, 40% increased precipitation and 60% increased precipitation treatment significantly decreased plant abundance by 38.9%, 33.8%, 35.8% and 45.7%, respectively. The aboveground biomass significantly increased with increasing precipitation, but aboveground plant biomass under 60% increased precipitation treatment being lower than that reducing under 40% increased precipitation treatment, probably due to the negative effects of flooding stress. In addition, Margalef richness index had a significantly positive relationship with aboveground biomass. Aboveground biomass, Shannon diversity index, Margalef richness index, and Simpson diversity index were negatively related to soil electrical conductivity, and aboveground plant biomass was positively related to soil moisture. Our results revealed that precipitation changes regulate growth characteristics, species composition, and diversity of plant community by altering soil water and salinity conditions in a coastal wetland.

[C:N:P stoichiometry in plants and soils of Phragmites australis wetland under different water-salt habitats]. / 不同水盐生境下芦苇湿地植被及土壤碳氮磷生态化学计量特征.

We examined the effects of channel diversion of Yellow River on the content and stoichiometry of carbon (C), nitrogen (N) and phosphorus (P) in the organs of reeds (stem, leaf, rhizome and fibrous root) and soils in three typical Phragmites australis communities in the Yellow River Delta, including P. australis community in the former Yellow River course abandoned in 1996, P. australis community on the new Yellow River course and the P. australis communities on the intertidal area (far from the abandoned and current channel but affected by the tides). The results showed that foliar C, N and P contents of P. australis were highest in the communities of abandoned Yellow River course. Leaf N, stem C and rhizome P contents were highest in the communities of new Yellow River course. Leaf N and stem C and P contents were highest in the communities of intertidal area. The average leaf C (409.48 g·kg-1) and P (1.09 g·kg-1) contents in the three habitats were lower than national and global average levels, while leaf N content (21.71 g·kg-1) was higher than that of national and global average levels. The mean leaf N:P (20.22) was higher than 16 and the mean soil N:P (0.87) was lower than 14, indicating that the P. australis growth in the three habitats was limited by P. Correlation analysis showed that EC was one of the main factors affecting C:N:P stoichiometry in P. australis. In general, the C and P reserves in P. australis in the study area were low, and N reserve was high. The soil organic carbon content was low, the soil C reserves were large, while the N and P were relatively scarce.

Co-regulation of rainfall amount and timing on soil carbon mineralization in a typical salt marsh of the Yellow River Delta, China.

Studying the effects of rainfall regimes such as rainfall amount and timing on soil carbon mineralization is of great importance for our understanding the mechanisms underlying the stability and accumulation of soil carbon in coastal salt marshes. In this study, we examined the responses of soil carbon mineralization (CO2 and CH4 fluxes) from undisturbed soil columns to rainfall events in different seasons (dry and wet seasons) with filed experiments in a primary Suaeda salsa region in the Yellow River Delta salt-marsh wetland, which is far away from the coast and not affected by tides. The results showed that rainfall amount and timing had a significant interaction in affecting soil CO2 flux rates. During the dry season, large rainfall events significantly reduced soil CO2 flux rates but had no significant effect in the wet season, which might be closely related to the significant increase in soil water content and salinity. Rainfall amount, rainfall timing and their interactions had no significant effect on soil CH4 efflux rates. Rainfall timing and rainfall amount did not affect CH4/CO2. CH4/CO2 increased with increasing soil water content and salinity. Soil water content and soil salinity showed similar increases to increasing rainfall amount. Our results suggested that the changing rainfall regime under climate change in the future would have a great impact on soil carbon mineralization and carbon sink function by regulating soil water and salt migration in this region.

[Effects of root abscisic acid on Na+ transport and photosystem 2 in Helianthus tuberosus under salt stress]. / ç›èƒè¿«ä¸‹èŠèŠ‹æ ¹ç³»è„±è½é ¸å¯¹é’ ç¦»å­è½¬è¿å’Œå ‰ç³»ç»Ÿâ ¡çš„å½±å“.

The effects of root abscisic acid (ABA) signal on Na+ transport and photosystem 2 (PS2) in Jerusalem artichoke (Helianthus tuberosus) under salt stress (150 mmol·L-1 NaCl) were examined by applying ABA synthesis inhibitor sodium tungstate to roots. Sodium tungstate inhibited ABA synthesis in roots, reduced root Na+ efflux, and increased the efficiency of Na+ transport from roots to leaves under salt stress. Salt stress increased leaf Na+ content and did not affect leaf membrane lipid peroxidation, PS2 reaction center protein and PS2 maximum photochemical efficiency (Fv/Fm ). The inhibition on root ABA synthesis significantly increased leaf Na+ accumulation, aggravated leaf membrane lipid peroxidation, impaired PS2 reaction center protein, decreased Fv/Fm, and induced PS2 photoinhibition. In conclusion, root ABA signal was beneficial to reducing leaf Na+ accumulation and preventing PS2 oxidative damage by inducing root Na+ efflux and inhibiting Na+ transport to the aerial part in H. tuberosus under salt stress.

Clonal integration in Phagmites australis mitigates effects of oil pollution on greenhouse gas emissions in a coastal wetland.

Clonal integration, i.e., resource sharing within clones, enables clonal plants to maintain biomass production when ramets (asexual individuals) under stress are connected to those not under stress. Oil pollution can strongly reduce biomass production, and connected ramets within clones may experience different levels of oil pollution. Therefore, clonal integration may help plants maintain biomass production despite oil pollution. Because biomass production is often negatively correlated with greenhouse gas emissions, we hypothesized that oil pollution would increase greenhouse gas emissions and that clonal integration would reduce such an effect. We tested these hypotheses in a coastal wetland dominated by the rhizomatous grass Phragmites australis near a major site of oil production in the Yellow River Delta in China. We applied 0, 5, or 10 mm crude oil per year for two years in plots within stands of P. australis and tested effects of severing rhizomes connecting ramets inside and outside a plot (i.e. preventing clonal integration) on biomass production, soil chemistry and greenhouse gas emissions. When severed, ramets inside plots with no added oil produced about 220 g aboveground biomass m--2 over the second growing season, and plots absorbed about 500 g total CO2 equivalents m-2. Adding 10 mm oil per year reduced aboveground biomass by about 30%, and caused plots to emit about 800 g CO2 equivalents m-2. Leaving ramets connected to those outside plots eliminated the negative effects of oil pollution on biomass production, and caused plots given 10 mm oil per year to emit about 50% fewer total CO2 equivalents. We conclude that oil pollution can increase greenhouse gas emissions and clonal integration can reduce the effect of oil pollution on biomass production and greenhouse gas emissions. Our study provides the first experimental evidence that clonal integration in plants can reduce greenhouse gas emissions.

[Food source and feeding habit of Helice tientsinensis from the common reed vegetation in high marsh of Yellow River Delta, China]. / 黄河三角洲高潮滩芦苇植被区天津厚蟹的食源食性.

Investigating the composition of food sources with stable isotope method can provide direct evidence for the top-down control in the coastal wetland. In this study, we examined food source and feeding habit of Helice tientsinensis of common reed (Phragmites australis) vegetation in high marsh of Yellow River Delta. The results showed that the density of crab was (5.5±1.5) ind·m-2, with the behavior of climbing P. australis to feed on the leaves at night. Under the same indoor experimental condition, H. tientsinensis showed feeding preference on fresh leaves of P. aus-tralis. The stable isotope food source analysis showed that the leaves of P. australis were one of the important food sources of H. tientsinensis in the field. There were temporal variations in the proportion of fresh leaves [May: (6.4±4.9)%, July: (5.8±4.9)%, September: (12.5±8.8)%] and dead leaves [May: (12.4±7.8)%, July: (15.5±9.9)%, September: (15.1±9.4)%]. Therefore, H. tientsinensis could inhibit P. australis's growth and affect litter decomposition through feeding disturbance behavior.

Control of invasive Spartina alterniflora: A review.

Spartina alterniflora has important ecological functions in its original place, such as bank protection and land reclamation, but often has negative impacts on the local ecosystem after it is introduced into new areas. This species is often considered as an invasive one. The invasion and control of S. alterniflora have caused a great concern. We reviewed the latest research progresses in the prevention and control of S. alterniflora from six different perspectives, including physical control, chemical control, biological control, biological substitution control, integrated control, and control strategies. The theoretical basis, technical details, control effect and environmental impact of the six kinds of control technologies were analyzed. We pointed out the shortcomings of existing control technologies and proposed some suggestions such as targeted control of different ecological risk zones.

[Construction of healthy wetland ecosphere in estuarine delta: Theory and method.] / 河口三角洲湿地健康生态圈构建:理论与方法.

The health of wetland ecosphere in an estuarine delta is determined by many factors, such as continuity of natural processes, ecosystem connectivity, habitat heterogeneity, and food web diversity. The contradiction between ecological and environmental protection and regional development in the estuarine delta is becoming more and more prominent. A series of man-made and natural processes directly and indirectly resulted in habitat fragmentation of wetlands, which has direct and strong impacts on the ecosphere health and the habitat function of wetlands. In this paper, we provided a perspective on researches on the basic theory of healthy wetland ecosphere, landscape ecological network system, hydrologic network construction, key food webs, and habitat heterogeneity. At the regional and landscape scales, with the linkages between land use and ecosystem integrity as the main line, we clarified the influences of habitat fragmentation on wetland ecological functions, especially the effects of landscape integrity and river connectivity on wetland habitat. At the community and ecosystem scales, emphasis should be given on the relationship between food web and ecosystem stability, especially the supporting role of food web diversity and habitat heterogeneity on the construction of wetland biosphere. Further efforts should focuse on the wetland habitats construction based on landscape integrity, hydrologic connectivity, habitat heterogeneity and food web diversity. These efforts could help to develop and optimize the theory and method of constructing wetland ecosphere and enhancing its ecological function, and promote the sound development of regional ecological environment and resource utilization in estuarine deltas.

[Effects of drying and wetting cycles induced by tides on net ecosystem exchange of CO2 over a salt marsh in the Yellow River Delta, China.] / 潮汐作用下干湿交替对黄河三角洲盐沼湿地净生态系统CO2交换的影响.

As a unique hydrological characteristic, the tidal action can strongly affect carbon balance in a salt marsh despite their short duration. Using the eddy covariance technique, we measured the net ecosystem CO2 exchange (NEE) and its environmental factors and tidal change over a salt marsh in the Yellow River Delta. It aimed to investigate the effect of tidal process and drying and wetting cycles induced by tides on NEE. The results showed that the tidal process promoted the daytime CO2 uptake, but it didn't clearly affect the nighttime CO2 release. Tidal inundation was a major factor influencing daytime NEE. The diurnal change of NEE showed a distinct U-shaped curve on both drought and wet stages, but not with substantial variation in its amplitude during the drought stage. The drying and wetting cycles enhanced the absorption of daytime CO2. Under drought stage, the mean of the maximum photosynthetic rate (Amax), apparent quantum yield (α) and ecosystem respiration (Reco) were higher than those in wet stage. In addition, the drying and wetting cycles suppressed the nighttime CO2 release from the salt marsh but increased its temperature sensitivity.

[Predicting the potential distribution of dominant species of the coastal wetland in the Yellow River Delta, China using MaxEnt model]. / 基于MaxEnt模型的黄河三角洲滨海湿地优势植物群落潜在分布模拟.

Soil and vegetation community were investigated using the method of kilometer grid sampling. In addition, using the maximum entropy (MaxEnt) and the GIS spatial analysis technique, the potential distribution of dominant species in the Yellow River Delta and their major environmental variables and ecological parameters were quantitatively analyzed. The results showed that the dominant species of the coastal wetland were Tamarix chinensis, Phragmites australis and Suaeda salsa in the Yellow River Delta. Among the environmental variables, six variables were significant contributors to the potential distribution model of T. chinensis: NO3--N, salt, slope, Mg, altitude and NH4+-N. The environmental variables influencing the distribution of P. australis were NO3--N, salt, TP, pH, altitude and NH4+-N. NO3--N, salt and NH4+-N were the significant factors determining the potential distribution of S. salsa. The probability of presence of dominant species of the coastal wetland in the Yellow River Delta was positively correlated with salt, but it was negatively correlated with the other major environmental variables. The model predicted that the core potential distribution of dominant species in the Yellow River Delta was mainly in the coastal areas. In addition, P. australis had a wider range of distribution, compared with T. chinensis and S. salsa.

[Research and prospects for response mechanisms of soil respiration to experimental warming]. / æ¨¡æ‹Ÿå¢žæ¸©å¯¹åœŸå£¤å‘¼å¸å½±å“æœºåˆ¶çš„ç ”ç©¶è¿›å±•ä¸Žå±•æœ›.

Soil respiration (Rs) is the main efflux of carbon pool from soil to atmosphere. Increasing Rs caused by rising temperature can result in significant change in the global carbon balance. Global mean land-surface temperature is predicted to rise by 0.3-4.8 ℃ by the end of 21 century. Therefore, how Rs responds to simulated experimental warming in the natural field is one of the critical issues in global change research. Here, we reviewed the response characteristics of Rs to simulated warming under different temporal and spatial patterns. Experimental warming can increase Rs at the short time scale, but there was no uniform law in the long-term warming experiments, and there were differences among different ecosystems. This paper also reviewed the mechanism underlying the simulated warming response of Rs. Warming can directly affect Rs, and warming can also affect Rs indirectly by affecting the environmental factors (e.g., soil water, soil salt, soil physical and che-mical properties), and the regulation of biological factors (e.g., photosynthesis, litter decomposition). Furthermore, we synthesized the formation mechanism of adaptability of Rs to warming, including adaptability of microbes, roots and enzymes to warming, water restriction, and regulation by excessive nitrogen and the substrate supply. Finally, the future research directions were proposed. The study of micro-ecosystem of rhizosphere, characteristics and mechanism of Rs under asymmetric warming should be strengthened. Also, more attention should be paid to the measurement of Rs in typical phenological periods and typical weather in different seasons. The research network of Rs response to simulated warming should be constructed for networking test.

[Effect of environmental and biotic factors on net ecosystem CO2 exchange over a coastal wetland in the Yellow River Delta.] / çŽ¯å¢ƒå’Œç”Ÿç‰©å› å­å¯¹é»„æ²³ä¸‰è§’æ´²æ»¨æµ·æ¹¿åœ°å‡€ç”Ÿæ€ç³»ç»ŸCO2交换的影响.

Using the eddy covariance technique, we measured the net ecosystem CO2 exchange (NEE) and its environmental and biotic factors over a coastal wetland in the Yellow River Delta to investigate the diurnal and seasonal variation in NEE and quantify the effect of environmental and biotic factors on NEE. The results showed that the diurnal change of NEE showed a distinct U-shaped curve during the growing season, but not with substantial variation in its amplitude during the non-growing season. During the growing season, the wetland acted as a significant net sink for CO2, while it became carbon source during the non-growing season. On the scale of a whole year, the wetland functioned as a strong carbon sink of -247 g C·m-2. Daytime NEE was mainly dominated by photosynthetically active radiation (PAR). Apparent quantum yield (α) and daytime respiration of ecosystem (Reco,d) reached maximum in August, while maximum photosynthesis rate (Amax) reached its maximum in July. Nighttime NEE had an exponential relationship with air temperature (Ta). The mean value of temperature sensibility coefficient (Q10) was 2.5, and it was positively related to soil water content (SWC). During the non-growing season, NEE was negatively correlated with net radiation (Rn), but not with other environmental factors significantly. However, during the growing season NEE was significantly correlated with Rn, Ta, soil temperature at 10 cm depth (Ts 10) and leaf area index (LAI), but not with aboveground biomass (AGB). Stepwise multiple regression analysis indicated that Rn and LAI explained 52% of the variation in NEE during the growing season.

[Effects of environmental and biotic factors on soil respiration in a coastal wetland in the Yellow River Delta, China.] / çŽ¯å¢ƒå› å­å’Œç”Ÿç‰©å› å­å¯¹é»„æ²³ä¸‰è§’æ´²æ»¨æµ·æ¹¿åœ°åœŸå£¤å‘¼å¸çš„å½±å“.

Using the Li-8150 multichannel automatic soil CO2 efflux system, soil respiration was measured continuously over a one-year period in a coastal wetland in the Yellow River Delta, China. Environmental and biological factors were measured simultaneously, including temperature, soil water content, aboveground biomass and leaf area index. The results showed that the diurnal variation of soil respiration presented a single-peak curve, but it appeared as multiple peaks when disturbed by soil freezing and surface flooding. Soil respiration showed obvious seasonal dynamics and a single peak curve. The average annual soil respiration was 0.85 µmol CO2·m-2·s-1, and the mean soil respiration rate was 1.22 µmol CO2·m-2·s-1 during the growing season. On one-year scale, soil temperature was a major factor influencing soil respiration in the coastal wetland, which explained 87.5% of the variation in soil respiration. On the growing season scale, soil water content and leaf area index accounted for 85% of the seasonal variation of soil respiration.

[Effect of air temperature and rainfall on wetland ecosystem CO2 exchange in China].

Wetland can be a potential efficient sink to reduce global warming due to its higher primary productivity and lower carbon decomposition rate. While there has been a series progress on the influence mechanism of ecosystem CO2 exchange over China' s wetlands, a systematic metaanalysis of data still needs to be improved. We compiled data of ecosystem CO2 exchange of 21 typical wetland vegetation types in China from 29 papers and carried out an integrated analysis of air temperature and precipitation effects on net ecosystem CO2 exchange (NEE), ecosystem respiration (Reco), gross primary productivity (GPP), the response of NEE to PAR, and the response of Reco to temperature. The results showed that there were significant responses (P<0.05) of NEE (R2 = 50%, R2=57%), GPP (R2 = 60%, R2 = 50%) Reco (R2 = 44%, R2=50%) with increasing air temperature and enhanced precipitation on the annual scale. On the growing season scale, air temperature accounted for 50% of the spatial variation of NEE, 36% of GPP and 19% of Reco, respectively. Both NEE (R2 = 33%) and GPP (R2 =25%) were correlated positively with precipitation (P<0.05). However, the relationship between Reco and precipitation was not significant (P>0.05). Across different Chinese wetlands, both precipitation and temperature had no significant effect on apparent quantum yield (α) or ecosystem respiration in the daytime (Reco,day, P>0.05). The maximum photosynthesis rate (Amax) was remarkably correlated with precipitation (P <0.01), but not with air temperature. Besides, there was no significant correlation between basal respiration (Rref) and precipitation (P>0.05). Precipitation was negatively correlated with temperature sensitivity of Reco (Q10, P<0.05). Furthermore, temperature accounted for 35% and 46% of the variations in temperature sensitivity of Reco (Q10) and basal respiration (Rref P<0.05), respectively.

[Net ecosystem CO2 exchange and its environmental regulation mechanisms in a reed wetland in the Yellow River Delta of China during the growth season].

By using eddy covariance technique, this paper measured the net ecosystem CO2 exchange (NEE) in a reed (Phragmites australis) wetland in the Yellow River Delta of China during the growth season of 2011, and investigated the variation patterns of the NEE and related affecting factors. The average diurnal variation of the NEE in different months showed a U-type curve, with the maximum net CO2 uptake rate and release rate being (0.44 +/- 0.03) and (0.16 +/- 0.01) mg CO2 x m(-2) x s(-1), respectively. The NEE, ecosystem respiration (R(eco)), and gross primary productivity (GPP) were all higher in vigorous growth season (from July to September) and lower in early growth season (from May to June) and late growth season (from October to November). Both R(eco) and NEE reached their maximum values in August, while GPP reached its peak value in July. During the growth season, the ecosystem CO2 exchange was mainly dominated by photosynthetic active radiation (PAR), soil temperature (T(s)), and soil water content (SWC). There was a rectangular hyperbolic relationship between the daytime NEE and PAR. The nighttime ecosystem respiration (R(eco,n)) was exponentially correlated with the T(s) at 5 cm depth, and the temperature sensitivity of the ecosystem respiration (Q10) was 2.30. SWC and T(s) were the main factors affecting the R(eco,n). During the entire growth season, the reed wetland ecosystem in the Yellow River delta was an obvious carbon sink, with the total net carbon sequestration being 780.95 g CO2 x m(-2).

[Evolution process and related driving mechanisms of Yellow River Delta since the diversion of Yellow River].

Based on the 23 sheets of remote sensing images from 1976 to 2009, in combining with the water and sediment data from Lijin station and the annual precipitation data of Yellow River Basin from 1976 to 2008, this paper quantitatively analyzed the features of water and sediment discharge from Yellow River, and the evolution process of Yellow River Delta and related driving mechanisms. In 1976-2008, the annual runoff and the annual sediment discharge into sea changed largely and frequently, but overall, presented a decreasing trend. Since the course of the Yellow River changed its direction to Qingshui channel in 1976, the Delta coastline and area were generally in a silting-up state. The evolution process of the Delta could be approximately divided into three stages, i.e., 1976-1985, 1986-1995, and 1996-2009, and the increasing rate of the Delta decreased with the stages. The coastline and area of the Delta were significantly exponentially correlated to the sediment accumulated at Lijin station, and the inter-annual variation of the precipitation of the Yellow River Basin had a strong correlation with that of the sediment at Lijin station, suggesting that the annual variation of the precipitation in Yellow River Basin was the main factor affecting the runoff and sediment discharge into sea.

[A new bibenzyl derivative from Bletilla striata].

AIM: To study the chemical constituents of Bletilla striata. METHODS: Various column chromatographies with silica gel and Sephadex LH-20 were employed for the isolation and purification. The structures of the compounds were elucidated on the basis of spectral analyses and chemical methods. RESULTS: Three compounds were isolated from the roots of Bletilla striata (Thunb.) Reichb. f. and identified as 5-hydroxy-4-(p-hydroxybenzyl)-3'-3-dimethoxybibenzyl (I), schizandrin (II), 4,4'-dimethoxy-(1,1'-biphenanthrene)-2,2',7,7'-tetrol (III). CONCLUSION: Compound I is a new bibenzyl derivative and II was isolated from this plant for the first time.