Spatial patterns and storage composition of woody debris in a natural secondary forest dominated by <Emphasis Type="Italic">Pinus tabulaeformis</Emphasis> on Loess Plateau,China

Woody debris (WD) is an important part of natural Pinus tabulaeformis mixed stands, and it affects the forest ecosystem stability and development. The WD spatial patterns are especially important structural characteristics that can provide insights into forest dynamics. In this paper, the WD storage, WD spatial patterns and WD associations among the main species were examined in the natural secondary forest on Loess Plateau in northwest China. Data were collected in a 1 ha (100 m × 100 m) permanent plot, and all the trees with a diameter at breast height of more than 3 cm were measured and stem-mapped. Ripley’s K functions from the spatial-point-pattern-analysis method were used to analyze the spatial distribution and associations. The results showed that: (1) The total storage of WD was 10.73 t/ha, fallen wood was the main source of WD, and the majority diameters were greater than 20 cm, and in intermediate levels of decay; (2) The overall spatial pattern was closely related to the spatial scale, which exhibited an aggregated pattern on a small scale, and a random pattern on a large scale. The spatial patterns of coarse woody debris also gradually transitioned from an aggregated pattern in fine scales to a random pattern in broader spatial scales, which matched the overall spatial pattern. The spatial intensity was gradually decreased with the increasing diameters, and increased with the decomposition classes; (3) The WD of Pinus tabulaeformis species was negatively associated with Betula platyphylla and Populus davidiana on a small scale but positively associated with these species on a large scale. The spatial pattern and interspecies relations were the results of long-term interactions between the natural secondary forest community and the surrounding natural environment. These findings would provide a scientific basis for the sustainable management and protection of natural secondary forest ecosystems on Loess Plateau.     

A novel model to assess soil productivity in the dry-hot valleys of China

Accurate evaluation of soil productivity has been a long-standing challenge. Although numerous models for productivity assessment exist, most are cumbersome to use and require substantial parameter inputs. We developed a new empirical soil productivity model based on field investigations of soil erosion, soil physicochemical properties, and crop yields in the dry-hot valleys (DHVs) in China. We found that soil pH, and organic matter and available potassium contents significantly affected crop yields under eroded conditions of the DHVs. Moreover, available potassium content was the key factor affecting soil productivity. We then modified an existing soil productivity model by adding the following parameters: contents of effective water, potassium, organic matter, and clay, soil pH, and root weighting factor. The modified soil productivity model explained 63.5% of the crop yield. We concluded that the new model was simple, realistic, and exhibited strong predictability. In addition to providing an accurate assessment of soil productivity, our model could potentially be applied as a soil module in comprehensive crop models.     

A back-propagation neural-network-based displacement back analysis for the identification of the geomechanical parameters of the Yonglang landslide in China

Xigeda formation is a type of hundred-meter-thick lacustrine sediments of being prone to triggering landslides along the trunk channel and tributaries of the upper Yangtze River in China. The Yonglang landslide located near Yonglang Town of Dechang County in Sichuan Province of China, which was a typical Xigeda formation landslide, was stabilized by anti-slide piles. Loading tests on a loading-test pile were conducted to measure the displacements and moments. The uncertainty of the tested geomechanical parameters of the Yonglang landslide over certain ranges would be problematic during the evaluation of the landslide. Thus, uniform design was introduced in the experimental design, and by which, numerical analyses of the loading-test pile were performed using Fast Lagrangian Analysis of Continua (FLAC^3D) to acquire a database of the geomechanical parameters of the Yonglang landslide and the corresponding displacements of the loading-test pile. A three-layer back-propagation neural network was established and trained with the database, and then tested and verified for its accuracy and reliability in numerical simulations. Displacement back analysis was conducted by substituting the displacements of the loading-test pile to the well-trained three-layer back-propagation neural network so as to identify the geomechanical parameters of the Yonglang landslide. The neural-network-based displacement back analysis method with the proposed methodology is verified to be accurate and reliable for the identification of the uncertain geomechanical parameters of landslides.     

Geomorphologic map of the 1<Superscript>st</Superscript> Mutnaya River,Southeastern Kamchatka,Russia

The Kamchatka Peninsula–situated in the Pacific “Ring of Fire”–has 29 active and over 400 extinct volcanoes. Since it is situated in the northeastern extremity of Russia, in subarctic climate, the volcanic landforms are overprinted by the 446 glaciers. This research focuses on the 1^stMutnaya catchment which drains the southern slopes of two active volcanoes: Avachinsky and Koryaksky. Those volcanoes are a permanent threat for the cities of Petropavlovsk and Elizovo, which are the 2 of 3 cities of the peninsula. Hence, most of the studies carried out in the area dealt with the natural hazards and only few focus on landscape evolution. Thus, the purpose of this study was to elaborate a cartographic approach which integrates classic geomorphology with state of the art GIS and remote sensing techniques. As result, different landforms and related processes have been analysed and included in the first general geomorphologic map of the 1^stMutnaya catchment.     

Limit equilibrium method (LEM) of slope stability and calculation of comprehensive factor of safety with double strength-reduction technique

When the slope is in critical limit equilibrium(LE) state, the strength parameters have different contribution to each other on maintaining slope stability. That is to say that the strength parameters are not simultaneously reduced. Hence, the LE stress method is established to analyze the slope stability by employing the double strengthreduction(DSR) technique in this work. For calculation model of slope stability under the DSR technique, the general nonlinear Mohr–Coulomb(M–C) criterion is used to describe the shear failure of slope. Meanwhile, the average and polar diameter methods via the DSR technique are both adopted to calculate the comprehensive factor of safety(FOS) of slope. To extend the application of the polar diameter method, the original method is improved in the proposed method. After comparison and analysis on some slope examples, the proposed method's feasibility is verified. Thereafter, the stability charts of slope suitable for engineering application are drawn. Moreover, the studies show that:(1) the average method yields similar results as that of the polardiameter method;(2) compared with the traditional uniform strength-reduction(USR) technique, the slope stability obtained using the DSR techniquetends to be more unsafe; and(3) for a slope in the critical LE state, the strength parameter φ, i.e., internal friction angle, has greater contribution on the slope stability than the strength parameters c, i.e., cohesion.     

Long-term statistics of extreme tsunami height at Crescent City

Historically, Crescent City is one of the most vulnerable communities impacted by tsunamis along the west coast of the United States, largely attributed to its offshore geography. Trans-ocean tsunamis usually produce large wave runup at Crescent Harbor resulting in catastrophic damages, property loss and human death. How to determine the return values of tsunami height using relatively short-term observation data is of great significance to assess the tsunami hazards and improve engineering design along the coast of Crescent City. In the present study, the extreme tsunami heights observed along the coast of Crescent City from 1938 to 2015 are fitted using six different probabilistic distributions, namely, the Gumbel distribution, the Weibull distribution, the maximum entropy distribution, the lognormal distribution, the generalized extreme value distribution and the generalized Pareto distribution. The maximum likelihood method is applied to estimate the parameters of all above distributions. Both Kolmogorov-Smirnov test and root mean square error method are utilized for goodness-of-fit test and the better fitting distribution is selected. Assuming that the occurrence frequency of tsunami in each year follows the Poisson distribution, the Poisson compound extreme value distribution can be used to fit the annual maximum tsunami amplitude, and then the point and interval estimations of return tsunami heights are calculated for structural design. The results show that the Poisson compound extreme value distribution fits tsunami heights very well and is suitable to determine the return tsunami heights for coastal disaster prevention.     

Spatial-temporal pattern and differences of land use changes in the Three Gorges Reservoir Area of China during 1975�C2005

Regional land use changes are an important part of global changes. The research on land use changes in the Three Gorges Reservoir Area of China attracts a lot of attention owing to the Three Gorges Dam building. The Three Gorges Reservoir Area becomes one of the important research areas. This study analyzed the transforming processes and traits of each land use type and the regional differences of land use changes during the past 30 years, summarized the distribution of different land use types in different buffer zones and regresses the equation areas and different buffer distances based on buffer analyses and regression analyses, and then analyzed the transforming rules in different buffer distances, got the optimal influence distances. The research results indicate that, (1) cultivated land lies at the northwest of the reservoir and was decreasing, however, the construction land was increasing, especially the urban construction land, a large number of land was flooded because of the reservoir water level rise; (2) urban area was sprawling quickly in developed and neighboring areas, and a great deal of cultivated land and a considerable amount of grassland were occupied; in the earlier time, rural settlements occupied lots of cultivated land and a sum of forestry land in the later time; (3) the optimum influenced distances for cultivated land and forestry land were 10–35 km, and for urban and rural settlements were in 5–20 km. Overall, this research can reflect the spatial-temporal characteristics of land use changes during the 30 years, and it is helpful for urban planning and land use planning in the reservoir area.     

The hydrogen peroxide impact on larval settlement and metamorphosis of abalone <Emphasis Type="Italic">Haliotis diversicolor supertexta</Emphasis>

Abalone Haliotis diversicolor supertexta is an important economic mollusk. The settlement and metamorphosis are two critical stages during its development period, which has direct influence on abalone survival and production. The influence of reactive oxygen species （hydrogen peroxide） on abalone embryo and juvenile development were examined in this study. Larvae of Haliotis diversicolor supertexta were induced to settlement and metamorphose by exposure to seawater supplemented with hydrogen peroxide. They had the best performance at 800 μmol/L. The concentration of 1 000 μmol/L or higher was toxic to the larvae, as the larvae could settle down only at benthic diatom plates without complete metamorphosis. In addition, H2O2 adding time was critical to the larval performance. 24h after two-day post-fertilization was proved to be the optimal adding time. In this paper, two action mechanisms of hydrogen peroxide are discussed： （1） hydrogen peroxide has direct toxicity to ciliated cells, thus cause apoptosis; （2） hydrogen peroxide, as a product from catecholamines＇ autoxidation process in vivo, can reverse this process to produce neuro-transmitters to induce abalone metamorphosis.     

Non-specific immune response of bullfrog <Emphasis Type="Italic">Rana catesbeiana</Emphasis> to intraperitoneal injection of bacterium <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

Non-specific immune response of bullfrog Rana catesbeiana to pathogenic Aeromonas hydrophila was studied to 60 individuals in two groups. Each bullfrog in bacterium-injected group was injected intraperitoneally （i.p.） with 0.2 ml bacterial suspension at a density of 5.2 × 10^6 CFU/ml, while each one in control group injected i.p. with 0.2 ml sterile saline solution （0.85%, w/v）. Three bullfrogs in both groups were sampled at 0, 1, 3, 7, 11, 15 and 20 days post-injection （dpi） for the evaluation of non-specific immune parameters. It was observed that intraperitoneal injection of A. hydrophila significantly increased the number of leucocytes and that of NBT-positive cells in peripheral blood. Significant increases in serum bactericidal activity and serum acid phosphatase activity were also observed in the bacterium-injected frogs when compared with those in the control group. However, a significant reduction was detected in vitro in phagocytosis activity of peripheral blood phagocytes. No significant difference in changes in the number of peripheral erythrocytes, serum superoxide dismutase （SOD） activity, and lysozyme activity was detected between the two groups. It is suggested that bullfrogs may produce a series of non-specific immune reactions in response to the A. hydrophila infection.