Applied Mechanics and Materials Vols. 295-298

Abstract: Thirty rhizosphere and non-rhizosphere soil samples from different infection grades(0, I, III, V and VII) of three typical banana plots(Jianfeng, Shiyuetian, Chongpo) infected by banana fusarium wilt (Fusarium oxysporum f. sp. cubense) in Hainan province were collected to study the microbial community functional diversity applying Biolog-ECO microplates technology. The results are as follows: (1) Overall carbon source metabolic capacities of soil microbial community weaken with increasing of infection grades of banana fusarium wilt. (2) Richness indices, Simpson indices, Shannon indices and McIntosh indices of soil microbial community gradually decreased with increasing of infection grades of banana fusarium wilt. (3) Principal component analysis show that metabolic characteristics of soil microbial community significantly change between the healthy plants and diseased plants in the same banana plot. The results would provide information for explaining the pathogenesis of banana fusarium wilt and controlling its incidence by applying microbial ecology to regulate soil environmental measures.

Abstract: Carbon dioxide is major cause of the greenhouse effect which is believed to be warming the Earth’s climate, the balance between accumulation of soil organic matter (SOM) and its loss through microbial respiration has global implications. In our study we have investigated dynamics of SOM during 2003-2011. Field investigations were conducted at two fields: fallow land and land cultivated by Tamarix. The following soil chemical properties also were evaluated: pH, electrical conductivity (EC), total and available NPK. The results revealed that amount of nutrients in soils are varied within two fields.

Abstract: On condition that the heat release rate is 50kW•m-2, the volume of a gas velocity is 24 L•s-1, the combustibility of Pinus koraiensis、Pinus sylvestris var. mongolica、Picea koraiensis、Larix gmelinii in Heilongjiang Province were determined systematically through the use of the controlled atmosphere tapered calorimeter. Through the comparative analysis of the heat release rate and the smoke production rate and some orther burning parameters of the barks and the withered leaves, combine the moisture content of barks and withered leaves of each species, evaluate the fire resistance of this four coniferous species. The results shown: the heat release rate, HRR; total heat release, THR; specific extinction area and smoke produce rate are higher in the barks and withered leaves of Picea koraiensis but the fire performance index is low, these instructions that the fireproof performance is worse in Pinus sylvestris var. mongolica; each Picea koraiensis burning indexs of the Larix gmelinii is lower or the lowest, both the smoke production rate, SPR and the heat release rate, HRR are slow, the fire performance index is high. However, its absolute moisture content and relative moisture content is the highest, it’s flammble.So,we conclude its fire-resistance performance is higher, we could choose it as the fire-preventing priority screening tree species; the flammability of Pinus koraiensis and Pinus sylvestris var. mongolica between the above two species. the combustion characteristics of trees is the result of multiple factor joint, The difference between the different research results is resulted in the choice of the indexs, so it’s urgent need to establish a comprehensive and integrated evaluation index system.

Abstract: Cylindrocarpon root rot caused by Cylindrocarpon destructans is a serious disease on ginseng (Panax ginseng) in northeast China. Some allelochemicals (phenolic acids) from root exudates and decaying residues of ginseng plant may be related to Cylindrocarpon root rot. The antibiotic effects of phenolic acids on Cylindrocarpon destructans were studied to investigate the relationships between the phenolic acids and the fungus in the plant-microbe interaction. Results show that the hyphal growth of C. destructans was inhibited by salicylic, cinnamic and benzoic acid. At the highest concentration (1600 μg ml-1) of salicylic and cinnamic acid, the colony diameter of C. destructans decreased by 32.47% and 23.78%, respectively. C. destructans growth was powerfully repressed by benzoic acid in a concentration-dependent manner. However, activities of phytopathogenic enzymes (pectinase and cellulase) were greatly stimulated by the phenolic acids. It was concluded that phenolic acids inhibited the growth of C. destructans but dramatically stimulated activities of hydrolytic enzymes of C. destructans.

Abstract: By using the recursive method, the total mass of the leaves for the whole tree is determined by the small parts of the trees. On the basis of summarizing the growth law of the tree, and assuming the shapes, branches and leaves of the tree follow its growth law, the mass measurement model is established, and the mass of the leaves in the highest-level branch is estimated by establishing the mass equations of the leaves. The variables in this model are the crown width, the crown height, the branch angle and the number of branches on each level per unit length. The parameters of this model are easy to obtain, and the extension of this model will push the establishment of database for various relative parameters. Moreover, it is found that there exists a certain relationship between tree shape index and leaf index, thus a new leaf classification method is proposed, and its description is carried out.

Abstract: Survival and germination of overwintering oospores of two strains from Gansu,China compared with two standard from Wageningen, the Netherlands of Phytophthora infestans were determined in 2010-2011. It was found that compatible mating strains of P. infestans A1 and A2 produce oospores abundantly in paired cultures on tomato-rye agar medium.The survival rate of overwintering was ranged from19.57% to 24.59%.The germination rate of overwintering was ranged from 3.58% to 8.49%, and there were no significant differences in germination rate of oospores between alternating light at day/night and whole darkness at day/night. Furthermore, the soil extract liquid was more suitable for oospore germination than distilled water.

Abstract: Buxus ichangensis is a rare shrub specifically distributed along the banks of the Yangtze River in Three Goreges Reservoir area. In order to bring a basis for population reconstruction and ex situ conservation, we surveyed the flood-tolerance capacity of B. ichangensis together with its close species, Buxus microphylla. The results showed that B. ichangensis plants were more tolerant to waterlogging stress. Through further investigation of the physiological responses of 2 Buxus species, we supposed a possible mechanism for flooding adaption that physiological factors, especially photosynthesis rate, stomatal conductance, chlorophyll content and root livingness, were highly correlated with flooding-tolerance.

Abstract: LI-6400-09 soil CO2 flux chamber (LI-COR, NE USA) and Subtraction method were used to investigate the diurnal and seasonal variations of soil respiration and the contribution of root respiration to total soil respiration in a temperate broad-leaved Korean Pine forest ecosystem, China. Soil temperatures at 5 cm depth were recorded by Hobo thermal recorder (at 1 h interval) and year-round soil respiration and the contribution of root could be calculated based the Q10 relationship. The results indicated that: Diurnal variations of total soil respiration (TRs) and root-severed soil respiration (RRs) were highly associated with variations of soil temperature at 5 cm depth in a day. total soil respiration, root-severed soil respiration (RRs) and root respiration (Rs) followed a similar seasonal trend that varied markedly during the growing season with high rates in summer and low rates in spring and autumn, coinciding with summer wet and high temperature, and in spring and autumn, with the lower temperature. The mean rates of TRs, RRs and Rs was 3.68, 2.02 and 1.63 µmol m-2 s-1, which were 1392.63, 764.43 and 616.84 g C m-2 y-1 respectively from May to September in 2004. TRs, RRs and Rs were exponentially correlated with temperature during growing season. However, there were no correlations between soil respiration and soil volumetric moisture. The Q10 values for TRs, RRs and Rs were 2.40, 2.42 and 2.50 respectively. The root was a major component of soil respiration, accounting for from 29.3 to 58.7% of the total soil respiration from May to September in 2004. The year-round mean of TRs, RRs and Rs were 1.95, 1.07 and 0.81 µmol m-2 s-1, which were 737.94, 404.92 and 306.53 g C m-2 y-1 respectively. Root respiration contributed 41.0% to the annual total soil respiration.

Abstract: From a greenhouse gas policy standpoint, forests play an extremely important role in the exchange of carbon dioxide between the land and atmosphere. Because forest management has a potentially large effect on the entire forest carbon (C) cycle, and the biological and industrial systems are tightly coupled in the North region of China, simulation of varying management and forest product production scenarios are needed to explore trade-offs of managing forests for multiple objectives. Thus, an important consideration in management of forests is their present and future capacity to sequester C from the atmosphere. In this paper, C balance of the biological system was simulated under different management scenarios that were designed to test effects of plant configuration.

Abstract: Phosphorus is the main nutrient element for plant growth, whereas most of phosphate in soil is fixated by calcium, aluminum, iron and organic compounds. Available phosphate deficiency has been the main limiting factor that influences the yield and quality of agricultural products. P solubilizing microorganisms have been widely reported of solubilizing different forms of insoluble phosphates. P solubilizing Rhizobium, especially for strains with the ability of secreting 3-Indole acetic acid, which is also capable of fixating N and inoculation, is found excellent in promoting growth and yield of legume crops, which decreases the cost of agricultural production and the side effect of P application to the environment. The mechanism and amount range of P solubilization for Rhizobium are varied among strains. These results and phenomena from different studies are discussed in this paper.