H. B. Shao

Spatio-temporal variation of rhizosphere soil microbial abundance and enzyme activities under different vegetation types in the coastal zone, Shandong, China

In coastal sandy soils, the establishment of a plant cover is fundamental to avoid degradation and desertification processes. A better understanding of the ability of plants to promote soil microbial process in these conditions is necessary for successful soil reclamation. The current study was to investigate the ability of four different plant species to regenerate the microbiological processes in the rhizosphere soil and to discuss which species were the most effective for the reclamation of the coastal zone. The rhizosphere soils were studied by measuring microbial abundance (bacteria, fungi, actinomycetes, and ammonifiers), enzyme activities (invertase, catalase, urease, and phosphatase) and their relationship. Microbial abundance greatly varied among rhizospheres of different plant species (p < 0.05). Phragmites australis supported the highest amount of bacterial, actinomycetes, and ammonifiers abundance, and Echinochloa crusgalli supported the highest fungi abundance. In addition, the significant differences in rhizosphere enzyme activities of different plant species were also observed. There was a significant linear correlation between rhizosphere soil microbial abundances and enzyme activities between bacteria and urease and between fungi and catalase, but no such significant relationship was found between all rhizosphere soil microbial abundance and phosphatases. It was concluded that different plant species in coastal areas have different rhizosphere soils due to the impact of the different root exudates and plant residues of the microbial properties. In addition, natural grasslands (P. australis and E. crusgalli) are the most effective for revegetating coastal sandy soils.

Simulated water balance of forest and farmland in the hill and gully region of the Loess Plateau in China

Abstract Large-scale vegetation establishment has not only helped to prevent serious soil and water loss on the Loess Plateau of China but also led to reduced water availability and soil desiccation. Examining the water balance of forested and farmed land allowed us to determine water consumption of vegetation and understand the mechanisms of soil desiccation, important factors for the sustainable conversion of farmland to forest in this area. The effects of forests and crops on the water balance within the soil–vegetation–atmosphere system were studied using a coupled water and heat flow model known as “CoupModel”, which was calibrated on the basis of field measurements of soil water content, surface runoff, throughfall, stemflow, leaf area index, vegetation cover, canopy height and depth of root system in the hill and gully region of the Loess Plateau. Data were collected between 27 May 2006 and 31 October 2007. Two types of planted vegetation (acacia forest and farmland) in the Yangou watershed in the northern part of the Shaanxi Province were chosen to examine water transfer in the absence of soil texture (silt loam) differences and to explore the importance of vegetation type in relation to water balance. The simulations indicated that vegetation type and slope aspect significantly influenced the magnitude of every water balance component in the soil–vegetation–atmosphere system. Compared to forest, farming the land reduced interception (69.1–78.3%) and transpiration (37.3–40.4%), while increasing surface runoff by a factor of 5.0–40.2 and soil evaporation by 3.1–32.0%. Thus, farming resulted in 1.1–1.2 times more soil water storage than afforestation. Therefore, canopy interception and transpiration are responsible for soil desiccation in plantation forests. Simulation differences in water balance between acacia forest and farmland highlight that when converting farmland to forest on the Loess Plateau of China, tree species should be selected with care; this is particularly important on south-facing slopes.

Ecological water demand of regional vegetation: The example of the 2010 severe drought in Southwest China

To determine the cause of the severe drought that hit five provinces (autonomous regions, municipalities) of Southwest China in 2010, the ecological water demand (EWD) of regional vegetation was explored. The key scientific question was whether the plantation of Eucalyptus and Hevea trees in this area could have led to the breaking of the regional EWD balance, thereby causing a regional drought. Therefore, major research progress and trends related to EWD of vegetation, such as characterization of vegetation water consumption from transpiration and eco-hydrological effects, were explored. Theories, methods, and practices regarding EWD of vegetation, and the correlation between regional vegetation types and droughts were evaluated. Finally, suggestions were made for specific scientific research on temporal and spatial evolution of typical artificial vegetation in Southwest China and on the relationship between EWD from regional vegetation and droughts. Thus, future research should include the following three aspects: (i) historical evolution and distribution pattern of regional artificial vegetation; (ii) water consumption from transpiration, water saving for drought prevention, and water and soil conservation of regional artificial vegetation; and (iii) the relationship between EWD of regional artificial vegetation and regional droughts. The proposed research focus is expected to provide a scientific basis for identifying the causes of regional droughts and the reasonable allocation of water resources. In addition, it will be of great importance in guiding restoration and reconstruction of regional artificial vegetation.

Photosynthetic and water use characteristics in three natural secondary shrubs on Shell Islands, Shandong, China

Ziziphus jujuba var. spinosa Hu, Periploca sepium Bunge, and Securinega suffruticosa (Pall.) Rehd are mainly natural secondary shrubs on Shell Islands of the Yellow River Delta. The physiological characteristics of leaves of the 3-year-old shrub species, including photosynthesis, apparent quantum yield (AQY), dark respiration rate (RD), light compensation point (LCP), light saturation point (LSP), transpiration rate (E), and water use efficiency (WUE) and so on, were studied by using a Li-Cor6400 portable photosynthesis system. The results showed that the modified rectangular hyperbola model could simulate the photosynthesis–light response curves better, with a compound correlation coefficient (R2) greater than 0.996. There were significant differences in the photosynthetic capacity, AQY, RD, LCP, LSP, E, and WUE among the three shrub species. The three shrub species displayed different photosynthetic ability in the same environment; the photosynthetic capacity of Z. jujuba was 1.49 times that of S. suffruticosa. Z. jujuba had the highest ability to use low light, and its AQY was 0.058, and that of other two species was among ordinary species. The consumption of photosynthetic products of S. suffruticosa was highest and it had the most active physiological metabolism. Z. jujuba had higher shade tolerance, while these three species were photophilous. The sequence of water-consuming ability by transpiration was in the order of Z. jujuba>P. sepium>S. suffruticosa. The water-consuming ability of P. sepium and S. suffruticosa did not show significant correlation with meteorological factors. P. sepium had the highest WUE, followed by Z. jujuba, and S. suffruticosa had the least. The net photosynthetic rate ( Pn ) and WUE had evident threshold responses to the variations of soil moisture to maintain high efficient water use. The relative moisture content (Wr) of Z. jujuba, P. sepium, and S. suffruticosa was within the range of 36.18–68.89%, 42.31–81.76%, and 46.87–91.62%, respectively, in which three natural secondary shrubs had higher levels of Pn and WUE. In summary, P. sepium had higher development potential, and Z. jujuba had physiological characteristics of higher photosynthetic ability, transpiration, and WUE, and is the most suitable shrub species for afforestation.

Direct production of bioethanol from Jerusalem artichoke inulin by gene-engineering Saccharomyces cerevisiae 6525 with exoinulinase gene

Jerusalem artichoke (Helianthus tuberosus L.), an important crop, containing over 50% inulin in its tubers on a dry weight basis is an agricultural and industrial crop with a great potential for production of ethanol and industrial products. Inulin is a good substrate for bioethanol production. Saccharomyces cerevisiae 6525 can produce high concentrations of ethanol, but it cannot synthesize inulinase. In this study, a new integration vector carrying inuA1 gene encoding exoinulinase was constructed and transformed into 18SrDNA site of industrial strain S. cerevisiae 6525. The obtained transformant, BR8, produced 1.1 U mL− 1 inulinase activity within 72 h and the dry cell weight reached 12.3 g L− 1 within 48 h. In a small-scale fermentation, BR8 produced 9.5% (v/v) ethanol, with a productivity rate of 0.385 g ethanol per gram inulin, while wild-type S. cerevisiae 6525 produced only 3.3% (v/v) ethanol in the same conditions. In a 5-L fermentation, BR8 produced 14.0% (v/v) ethanol in fermentation medium containing inulin and 1% (w/v) (NH4)2SO4. The engineered S. cerevisiae 6525 carrying inuA1 converted pure nonhydrolyzed inulin directly into high concentrations of ethanol.

Influence of outbreak of macroalgal blooms on phosphorus release from the sediments in Swan Lake Wetland, China

Macroalgal blooms have occurred worldwide frequently in coastal areas in recent decades, which dramatically modify phosphorus (P) cycle in water column and the sediments. Rongcheng Swan Lake Wetland, a coastal wetland in China, is suffering from extensive macroalgal blooms. In order to verify the influence of macroalgal growth on sediment P release, the sediments and filamentous Chaetomorpha spp. were incubated in the laboratory to investigate the changes of water quality parameters, P levels in overlying water, and sediments during the growth period. In addition, algal biomass and tissue P concentration were determined. In general, Chaetomorpha biomasses were much higher in high P treatments than in low P treatments. Compared with algae+low P water treatment, the addition of sediments increased the algal growth rate and P accumulation amount. During the algal growth, water pH increased greatly, which showed significant correlation with algal biomass in treatments with high P (P < 0.05). P fractions in the sediments showed that Fe/Al–P and organic P concentrations declined during the algal growth, and great changes were observed in algae+low P water+sediment treatment for both. As a whole, the sediments can supply P for Chaetomorpha growth when water P level was low, and the probable mechanism was the release of Fe/Al–P at high pH condition induced by intensive Chaetomorpha blooms.

Diurnal dynamics of CH4, CO2 and N2O fluxes in the saline-alkaline soils of the Yellow River Delta, China

Salt-affected soils are extensively present and constitute about 7% of total land surface. However, our knowledge about greenhouse gas (GHG) turnover between the atmosphere and the saline soils is very limited. In order to evaluate the potential of GHG consumption in saline soils, we measured gas fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from the soil surface to the atmosphere under saline-alkaline mudflat and various community types in the Yellow River Delta in China. In general, the emissions of GHG of different ecosystems showed a unique peak diurnal pattern, with the peak at 13:00 h and the lowest value at 07:00 h. The CH4 and N2O emission of different ecosystems followed the order: saline-alkaline mudflat>T. chinensis>S. salsa>P. australis, while the CO2 emission followed the order: T. chinensis>P. australis>S. salsa > saline-alkaline mudflat. On the whole, saline-alkaline mudflat and different vegetations acted as CO2 and N2O source in spring, while saline-alkaline mudflat and P. australis communities acted as CH4 source and CH4 sink, respectively. However, T. chinensis and S. salsa communities acted as CH4 sink before 12:00 h and CH4 source after 12:00 h. Although measurements of the CO2, CH4 and N2O fluxes were taken simultaneously, CH4 and N2O fluxes were strongly correlated with soil moisture, temperature and electrical conductivity, while no significant correlation was found between CO2 flux with above environmental factors. These results probably suggest that factors other than soil temperature, moisture and salinity exerted a larger impact on fluxes than on CH4 and N2O release and/or that there were not enough samples for CO2 flux measurements because of its higher spatial and temporal variability.

Threshold effects of photosynthetic efficiency parameters of wild jujube in response to soil moisture variation on shell beach ridges, Shandong, China

To investigate the threshold effects of photosynthetically active radiation (PAR) and soil mass water content (MWC) on photosynthetic efficiency parameters of Ziziphus jujuba Mill var. spinosa and to understand the adaptability of Z.jujuba to light and soil moisture variation, we determined optimal MWC and PAR for Z. jujuba which maintained higher net photosynthetic rate (PN) and water use efficiency (WUE). Using a Li-6400 portable photosynthesis system, we measured light response of PN, transpiration rate (E), WUE, and other gas-exchange parameters of 3-year-old Z. jujuba shrubs in a range of soil moisture conditions. The results showed that the leaf photosynthetic rate and WUE of Z. jujuba had a significant response to MWC and PAR. Given increases in the MWC (7.1–17.6%), the plants light compensation point decreased and its light saturation point (LSP), apparent quantum yield, and maximum PN increased. When MWC was at 17.6%, the low and high light use efficiency of Z. jujuba was all maximal. PN obviously increased with increasing MWC (9.2–17.6%). However, PN decreased when MWC was too high or low. When PAR ranged from 800 to 1200 μmol m− 2 s− 1, PN and WUE were higher and the LSPs of PN and WUE ranged between 706 and 1209 μmol m− 2 s− 1. These data indicate that Z. jujuba possessed higher adaptability to light conditions. Based on photosynthetic efficiency parameters, the soil moisture availability and productivity of Z. jujuba were classified and evaluated. For Z. jujuba woodland, MWC < 9.2% and MWC>21.5% resulted in low productivity and medium WUE, 19.8–21.5% of MWC resulted in medium productivity and low WUE, 9.2–11.2% of MWC resulted in medium productivity and medium WUE, and 11.2–19.8% of MWC resulted in high productivity and high WUE. The optimum high productivity and high WUE of MWC were at 17.6%, and the corresponding optimum PAR was 1209 μmol m− 2 s− 1.

RECENT STUDY ON PLANT-SOIL INTERACTIONS IN CHINA - PART I Some progress in the study of plant-soil interactions in China

Plants and soil are the base for sustainably surviving human beings on the globe as the role of materials, energy, resources and environment (Shao & Chu 2008; Shao et al. 2008, 2009, 2010, 2012a,b; Liu & Shao, 2010; Ruan et al. 2010; Xu et al. 2010, 2012; Shao 2012; Huang et al. 2013). This topic has been extensively investigated for 100 years with more achievements in many sectors and practical significance in conducting high-efficient agriculture and eco-environmental construction. The plant–soil interaction is the core issue of this topic, which has been given much attention for the past 30 years (Wu et al. 2007, 2010; Zhang et al. 2011, 2013; Xu et al. 2012, 2013).

Optimizing medium for producing ethanol from industrial crop Jerusalem artichoke by one-step fermentation and recombinant Saccharomyces cerevisiae

In order to obtain a high ethanol yield from the Jerusalem artichoke raw extract and reduce the fermentation cost, we have engineered a new recombinant Saccharomyces cerevisiae strain that could produce ex-inulinase. The response surface methodology based on Plackett–Burman and Box–Behnken design was used to optimize the medium for the ethanol production from the Jerusalem artichoke raw extracts by the recombinant strain. In the first optimization step, Plackett–Burman design was employed to select significant factors, including concentrations of yeast extract, inoculum, and MgSO4·7H2O. In the second step, the steepest ascent experiment was carried out to determine the center point with the three significant factors; the selected combinations were further optimized using the Box–Behnken design. The maximum ethanol production rate was predicted at 91.1 g/l, which was based on a medium consisting of yeast extract 9.24 g/l, inoculum 39.8 ml/l, and MgSO4·7H2O 0.45 g/l. In the validating experiment, the ethanol fermentation rate reached 102.1 g/l, closely matching the predicted rate.