Abstract:Global atmospheric carbon dioxide concentration ([CO₂]) is increasing rapidly. The Intergovernmental Panel on Climate Change estimated that atmospheric [CO₂] has risen from approximately 280 μmol mol^-1 in pre-industrial times to approximately 381 μmol mol^-1 at present and will reach 550 μmol mol^-1 by 2050. In the absence of strict emission controls, atmospheric [CO₂] is likely to reach 730–1020 μmol mol^-1 by 2100. Rising atmospheric [CO₂] is the primary driver of global warming, but as the principal substrate for photosynthesis it also directly affects the yield and quality of crops. Food quality is receiving much more attentions recently, however, compared with grain yield, our understanding in the response of grain quality to elevated [CO₂] is very limited. Rice (Oryza sativa L.) is one of the most important crops in the world and the first staple food in Asia, providing nutrition to a large proportion of the world’s population. Elevated [CO₂] leads to numerous physiological changes in rice crops, such as changes in the photosynthesis and assimilate translocation, nutrient uptake and translocation, water relation, and altered gene expression and enzyme activity. These altered processes are very likely to affect the chemical and physical characteristics of rice grains. In this review, we first describe main characteristics of rice grain quality, and then summarize findings in literature related to the impact of elevated [CO₂] on grain quality falling into four categories: processing quality, appearance, cooking and eating quality, and nutritional quality, as well as the possible mechanisms responsible for the observed impacts. Elevated [CO₂] caused serious deterioration of processing suitability, in particular, head rice percentage was significantly decreased. In most cases, elevated [CO₂] increased chalkiness of rice grains. The evaluation of physicochemical characteristics together with starch Rapid Visco Analyser (RVA) properties indicated no change or small changes in cooking and eating quality under elevated [CO₂], and these changes could not be detected by sensory taste panel evaluation. Elevated [CO₂] significantly decreased nitrogen or protein concentration in rice grains, while in most cases other macro- and micro-nutrients showed no change or decrease in concentration. In addition, the responses of rice quality to elevated [CO₂] might be modified by varieties, applied fertilizer rates or gas fumigation methodologies. The available information in the literature indicates a clear tendency of quality deterioration and thus lower commercial value for rice grains grown under a projected high CO₂ environment. Understanding the factors causing quality deterioration in rice and the related biological mechanisms might be the utmost important scientific theme in future research. Here we also discuss the necessity of formulating adaptation strategies for rice production in future atmospheric environments, nevertheless, the increase in yield, the improvement in quality and stress resistance of rice should be combined and integrated into the adaptation approaches. Compared with enclosure studies, the field experiments using Free-Air CO₂ Enrichment (FACE) system provide sufficient experimental space and the most realistic mimic of a future high CO₂ atmosphere, and give scientists perhaps the best opportunity to achieve multiple goals.

Abstract:Mining activities lead to the destruction of soil properties and productivity. Accomplishment of soil properties which existed before mining can be used for successful reclamation of the mined out area. With this aim proposed bauxite mines in the Eastern Ghats, India, were studied with respect to the exchangeable fraction of Na, K, Li, Ca and Mg. Na in the soils ranged from 4 to 82 mg/kg, K 15.2–746 mg/kg, Ca 119.6–2875.2 mg/kg, Li 1.2–14 mg/kg and Mg 349.8–2391.9 mg/kg. The elements studied varied significantly among the locations (ANOVA, P < 0.05). Cation Exchange Capacity (CEC) was negatively correlated with most of the variables. Principal Component Analysis (PCA) accounted for 95.6% of the total variance. PC1 (first principal component) formed of pCa, rMg, Mg:Ca, rCa and pMg, indicated Ca type enrichment in the system. PC2 and PC3 reflected the influence of SAR, pNa, rNa and Na, and Mg and CEC, respectively. The study, aimed at documenting the background concentrations of base cations in the Araku soil system, India, will be useful in later years during mine restoration programme. It would also form a base document for the mine managers during mine restoration.

Abstract:The effects of nitrogen (N) deposition on Pogonatum cirratum (Sw.) Bird. subsp. fuscatum (Mitt.) Hyvoenen, a species of moss widely distributed in South China, were investigated. Plots subjected to a gradient of N treatments were established in 3 habitats with different illumination and humidity conditions. N was sprayed onto plots with NH₄NO₃ solutions, at doses equivalent to 20, 40 and 60 kg N ha^-1, in 4 applications during May 2006 and January 2007. The results suggest that high N deposition affects both carbon (C) and N metabolism of P. cirratum subsp. fuscatum, as well as the interaction between them. On the other hand, the sensitivity of the moss varied according to the humidity and light conditions. Moss in a habitat with high humidity and moderate light was more tolerant to an N deposition increase than moss in a habitat with low humidity and low light, as the latter was extremely sensitive to an increase in N deposition.

Abstract:The current cropping system of excessive tillage and stubble removal in the northwestern Loess Plateau of China is clearly unsustainable. A better understanding of tillage and stubble management on surface soil structure is vital for the development of effective soil conservation practices in the long term. Changes in surface soil structure and hydraulic properties were measured after 4 years of stubble management (stubble retained vs. stubble removed) under contrasting tillage practices (no-tillage vs. conventional tillage) in a silt loam soil (Los Orthic Entisol) in Dingxi, Gansu, the northwestern Loess Plateau, China. Our results indicated that after 4 years small but significant changes in soil properties were observed amongst the different tillage and stubble treatments. Surface soil (0–5 cm) under no-tillage with stubble retention had the highest water stability of macroaggregates (>250 μm), soil organic carbon (SOC) and saturated hydraulic conductivity. Significant correlation was found between water stable macro-aggregates and soil organic carbon content, indicating the importance of the latter on soil structural stability. The improvement in soil structure and stability was confirmed by higher soil hydraulic conductivity measurements. Consistently higher K_sat was detected in the no tillage with stubble retained soil compared to other treatments. Therefore, no-tillage with stubble retention practice is an effective management technique for improving physical quality of this fragile soil in the long term.

Abstract:Application of remote sensing (RS) and geographical information system (GIS) techniques has been increased in natural sciences. In fact, it is inevitable applying of these techniques in vegetation studies due to the existence of some problems in traditional methods (e.g. sampling, calculation, analysis and so on). On this scope, scientists must have sufficient information about the efficiency of these techniques as a useful tool in their studies. This study aims to evaluate the IRS-P6 LISS III and Landsat ETM⁺ efficiency in plant groups’ identification. In order to this purpose, 143 training samples were collected from areas that showed homogenous composition of plant species in at least area of 3600 m² (60 × 60 m). Coordinates of these training samples were recorded using a GPS device and transferred to a GIS database. Also, ENVI 4.2 package has used to process and analyze the satellites data. Several methods of processing such as; spectral separability, supervised classification and assessment of classification accuracy were used in order to gain a satisfy evaluation of the data efficiency. The results indicated that net farming of alfalfa and Juniperus polycarpus–Artemisia kopetdaghensisi community have the most separability on the satellite images (1.99 for Landsat and 2 for IRS). Against, the least separabilities on the Landsat data were between Ju. polycarpus–Onobrychis cornuta and Ju. polycarpus–Ar. kopetdaghensis communities (1.57) and between Ju. polycarpus–Ar. kopetdaghensis and Ju. polycarpus–Agropyron intermedium (1.53) on the IRS data. According to these results, it is concluded that the satellite data are somedeal able to identify plant groups when vegetation communities are sufficiently homogenous, abundant and spectrally and ecologically separable.

Abstract:The structure and dynamics of periphytic algae in Jinyang Lake, the largest man-made lake in Taiyuan, Shanxi, have been studied by examining the periphytic algae samples collected from four sampling stations, during March 2006 to February 2007. In total, 227 species of periphytic algae (including varieties), belonging to three divisions, 27 families, 62 genera, have been identified. Diatoms were the dominant periphytic algae group. Taken the Shannon–Weaver, Margalef and Simpson diversity index together, it showed obvious temporal and spatial dynamics among different seasons and different sampling stations. The highest periphytic community structure evenness appeared at sampling station I in spring, summer and autumn, while at sampling station III in winter. The average biomass of periphytic algae varied from seasons. Our data showed that major factors affecting the periphytic algae in Jinyang Lake was water temperature, nutrient levels as well as human activities. In addition, the main effect caused by thermal power plant has been discussed.

Abstract:Allelopathy of diterpenoids extracted from plants of the genus Robdosia on three common species of soil ciliates, Colpoda inflata, Colpoda cucullus and Euplotes muscicola, was studied by acute toxicity test, sub-lethal effect test and morphological observation. Acute toxicity test showed that there was remarkable toxicity of the diterpenoids on the individuals of the three soil ciliate species, and there was close correlation between toxicity and concentration of the diterpenoids. 12 h-LC₅₀ values of the diterpenoids on the individuals of C. inflata, C. cucullus and E. muscicola were 161.40 mg L^-1, 94.80 mg L^-1 and 83.70 mg L^-1 respectively, and 24 h-LC₅₀ values were 114.90 mg L^-1, 92.30 mg L^-1and 65.80 mg L^-1 separately. Sub-lethal effect test of soil ciliates suggested that there existed significant inhibition of the diterpenoids on population growth of the three ciliates with dose-dependant relationships, population density and growth rate of the test group was obviously lower than that of the control group. Morphological observation indicated that diterpenoids affected the body shapes of the three ciliates and made them shorter and thicker, and the higher the concentration of diterpenoids, the greater the affection. The results are of great significance for understanding the functions of ciliates and their relationships to other organisms, and for the application of allelopathy in biological pest control in the soil ecosystems.

Abstract:Arbuscular mycorrhizal (AM) fungi colonize the roots of over 80% of terrestrial plant species, forming mutually beneficial symbioses. During the colonization process, symbiotic partners recognize each other, and undergo observable morphological and physiological changes; indicating that symbiosis formation involves multiple factors that are finely regulated. Sometimes host plants generate a transient, weak, defense response. This response and its down-regulation play a very important role in the development of AM symbioses. Although AM fungi can infect a wide range of host root tissues, which host defense may play a crucial role is hypothesized from the fact that hyphal expansion is only observed in the root cortex.
We discuss five defense mechanisms. (1) The degradation of exogenous elicitors. The host’s weak defense response may be due to the degradation of the exogenous elicitor chitin, or the prevention of release of an endogenous inductor from the plant cell wall. (2) The inactivation of defense signal molecules. Some defense signal molecules such as hydrogen peroxidase, salicylic acid (SA), and jasmonic acid (JA), are inactivated in host plants. This helps to avoid the turn-on of defense-related genes and facilitate mycorrhizal formation. (3) The regulation of plant hormones and plant photosynthates. Plant hormone levels and plant photosynthate metabolism both change during AM colonization. These mechanisms need further exploration. (4) Changes in levels of phosphorous (P), and (iso)flavonoids. High P levels can induce some defense genes to express hydrogen peroxidase, chitinase, and glucanase. These gene products can repress colonization by AM fungi. The plant defense response regulatory effect for different (iso)flavonoids varies, and their levels are regulated by P. (5) The suppressed expression of symbiotic genes. Some symbiosis-related genes inhibit plant defense responses, but it is still unclear which mechanisms underlie gene regulation. We provide here a theoretical basis for research into AM symbiosis that may promote study of host plant resistance and the mechanisms of symbiosis formation.
We provide a deeper insight into the signal transduction pathways of mycorrhization that will aid understanding and analysis of plant defense mechanisms in the AM context. The on-going development of genome sequencing technology will contribute greatly to the detailed study of symbiosis-related genes, and pathogenesis-related protein genes. These related genes may be induced to express corresponding proteins, be repressed, postpone expression or even shutdown, or both may work together to form symbioses. Elucidation of these features will help us understand the roles that plant defenses play in mycorrhizal formation; providing an unprecedented opportunity for research into mycorrhizal molecular biology and the interaction of symbiotic partners, and allowing the underlying mechanisms to be gradually uncovered.

Abstract:In the present work, we evaluated the feeding selectivity of starved Daphnia magna on two freshwater green algae Chlamydomonas sajao and Chlorellapyrenoidosa. Compared to C. pyrenoidosa, food quality of C. sajao are better in food palatability (cell size and digestibility), but poor in nutritional content (total carbon content). D. magna was starved for 0 and 8 d, and then was allowed to graze on a mixture of C. sajao and C. pyrenoidosa with following proportion: 5 × 10⁴: 35 × 10⁴ cells ml^-1, 20 × 10⁴: 20 × 10⁴ cells ml^-1 and 35 × 10⁴: 5 × 10⁴ cells ml^-1. The results indicated that the ingestion rate and filtration rate of starved D. magna, comparing with satiated groups, on C. pyrenoidosa increased significantly, while, inverse trends was observed in C. sajao. Base on selectivity coefficient of D. magna, we observed that when D. magna was in satiation C. sajao will be preferred, while, C. pyrenoidosa will be selected when D. magna was in starvation, and moreover, these foraging behaviors were not influenced by the relative food abundance of each green alga. Therefore, a tradeoff between food palatability (physical makeup) and food nutritional content (chemical composition) can be hypothesized in the foraging behavior of D. magna, which is modified by the starvation of feeder. High valuable food is always selected by D. magna as predicted by optimal foraging theory. However, when D. magna is in satiation food diets with adequate size and easy digestibility will be preferred, while, those foods with relatively higher lipid or total carbon content will be selected when D. magna is in starvation.

Abstract:In order to investigate the effect of organic volatiles from poplar species on the host plants orientation of Saperda populnea, the essential oil in the 2–3 years old branches from the sapling or mature trees of Populus simonii Carr. and P. simonii Carr. × P. nigra L. were extracted using the steam distillation method. The chemical composition and relative content in essential oil from those branches was analyzed by GC–MS. The main components contained in those volatiles from the four kinds of branches are mainly aromatic compounds such as 1,2-cyclohexanedione, 2-cyclohexene-1-one, p-xylene and 1,2,3-trimethylbenzene and so on. The relative content of aromatic compounds contained in branches from saplings was higher than that contained in branches from old tress. EAG response and behavioral reaction of S. populnea L. to those four kinds of distillated essential oil were tested. The results shown that male and female adults of S. populnea L. shown significant choice behavior and strong olfactory response to those essential oil distillated from branches of P. simonii Carr. and P. simonii Carr. × P. nigra L.. The EAG bioassay of S. populnea L. to 10 kinds of monomers compounds which had relative higher contents was tested. The results shown that the EAG response of female adults of S. populnea L. to 1 mol L^-1 p-xylene was intensest and reached 1.027 mV, the strength of their EAG response to 0.1 mol L^-1 phenol took the second place. The EAG response of male adult of S. populnea L. to 1 mol L^-1 p-xylene was strongest and reached to 0.824 mV, the strength of their EAG response to 1 mol L^-1 salicylaldehyde took the second place. In the choice behavior test of S. populnea L. adult to monomeric compound carried out in ‘Y’ type olfactometer have found that female and male adult of S. populnea L. all appeared obvious positive taxis to 0.1 mol L^-1 p-xylene. The selection rate of female and male adults ware (76.7 ± 4.1)% and (71.7 ± 2.6)%, respectively. The selective reaction to 0.1 mol L^-1 1,2-cyclohexanedione and 2-cyclohexene-1-one were not obviously than that to 0.1 mol L^-1 p-xylene. The male and female adult of S. populnea L. appeared repelling behavior to 0.1 mol L^-1 salicylaldehyde.

Abstract:Haloxylon ammodendron is one of the main shrubs that were used in desertification control project in China. Large area (2700 km²) of H. ammodendron plantation, especially more than 10 years plantation, has degraded outside Minqin oasis, northwest China. It is hard for H. ammodendron plantation to utilize ground water deeper than 20 m and to use precipitation with only mean annual 116.2 mm and uneven distribution in growing season. Thus, soil water might be the main water source of H. ammodendron plantation. Moreover, following H. ammodendron grows up, more soil water will be needed. In this study, it is hypothesized that H. ammodendron plantation would utilize deeper soil water as its age increased. Water use characteristics of different ages of H. ammodendron plantation (2 years, 5 years, 10 years, 20 years and 30 years) were examined by stable oxygen isotope technology outside Minqin oasis in July 2009. The δ¹⁸O values of water in H. ammodendron xylem, six different depths of soil (20 cm, 30 cm, 50 cm, 100 cm, 150 cm and 200 cm), rain and ground water (replaced by well water) were compared to determine major water source of H. ammodendron plantation. Meanwhile, the density, height, length and width of individuals were measured, and soil water contents were examined at the six depths in these plantation. The results showed that in 5 years H. ammodendron plantation, soil water content in 50 cm was significantly lower than moving sand dune and other ages, and soil water content in 100–200 cm was lower than moving sand dune and 2 years H. ammodendron plantation. The main depth that H. ammodendron used soil water increased as the age increased; 2 years H. ammodendron mainly used 50–200 cm soil water; 5 years H. ammodendron used 100–200 cm soil water and started to use ground water; 10 years H. ammodendron used 150–200 cm soil water and ground water, plant density of H. ammodendron declined and soil water content recovered gradually; 20 years and 30 years H. ammodendron mainly used ground water. Therefore, excessive consumption to soil water of high plant density might be one of the reasons for the degradation of H. ammodendron plantation. The critical age of H. ammodendron plantation is 5 years outside Minqin oasis because it consumed excessive soil water. If the density of 5 years H. ammodendron plantation was not decreased by selective cutting at present, it would degrade as the stand age increased later. It is suggested that initial density of new H. ammodendron plantation outside Minqin oasis must be reduced to slow down its consumption of soil water in future, and then the stability of H. ammodendron plantation could be sustained for a longer time.

Abstract:The interface between decaying plant residues and soil is a focus for soil ecological processes because of resources from the residues diffusing into the soil, and microfauna that proliferate in the adjacent soil. Given that the recovery of soil function following disturbance depends on immigration, colonization and establishment of exotic organisms from adjacent un-disturbed habitats, and the availability of bio-available resources, we hypothesized that the soil–litter interface could contribute to soil functional stability. In laboratory pot trials, soil was separated into two parts by a mesh bag with the inner section amended, or not amended, with rice straw; an outer layer of unamended soil, adjacent to the litter (1.5 cm thick, either heated or not), provided a soil–litter interface. This enabled us to examine the dynamics of dissolved organic carbon (DOC), mineral nitrogen, microbial biomass carbon (MBC), nematode assemblages and functional stability during 35 days incubation. Either 1 mm or 5 μm meshes were used, which allowed nematodes to migrate (SR1) or not (SR5) through the mesh to the soil–litter interface; thus also enabling us to evaluate the role of nematodes in soil functional stability. Higher DOC and MBC but lower mineral nitrogen concentrations were found at the soil–litter interface. Heating increased the availability of soil resources such as mineral nitrogen and DOC, but decreased the MBC and total nematode abundance in the soil. The soil–litter interface was characterized by a higher abundance of nematodes, particularly microbivores, regardless of mesh aperture or disturbance. The difference in nematode abundance between SR1 and SR5 indicated that nematode propagation, due to resource diffusion and nematode migration through the mesh, contributed to the changing numbers of microbivorous nematodes depending on incubation time. The soil functional stability was calculated as a relative change in the functioning of short-term barley decomposition. Soil functional resistance, defined as the instantaneous effect of disturbance on decomposition measured on the first day, was highest in the SR5 treatment. However, soil functional resilience, defined as the recovery of soil function over the whole incubation period (35d), was highest in the SR1 treatment, which is most probably attributed to the functioning of microbivorous nematodes. Our results suggest that small-scale spatial heterogeneity, due to organic residue decomposition, can help maintain soil functions following disturbance.