Table of Content

20 May 2019, Volume 55 Issue 3

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Simulation and Experimental Study on the Effect of Large Granular Rocks in Lunar Soil on Drilling Load

PANG Yong, FENG Yajie, SUN Qichen, LAI Xiaomin, WANG Haiyuan, CHEN Xibao, LIANG Jieneng, LIU Tianxi

2019, 55(3):  397-404.  DOI: 10.13209/j.0479-8023.2019.008

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The dynamics of auger drilling into lunar soil with large granular rocks was studied by discrete element method (DEM) simulation and experiment, in which the large granular rocks with different configurations were arranged at different locations. The result of simulation and experiment indicate that the surface morphology is the key factor which controls whether the granular rocks could be removed in drilling process. The result would be an important support for China’s deep space exploration mission.

Studies on Energy Saving of Robot Fish Based on Reinforcement Learning

FU Rubin, LI Liang, XU Cheng, XIE Guangming

2019, 55(3):  405-410.  DOI: 10.13209/j.0479-8023.2019.025

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The authors studied energy saving in fish school utilizing a bio-inspired robotic fish platform. Specifically, two robotic fish were fixed in the flow tank against the current with constant left-right distance and front-back distance; the body posture of the front robotic fish was controlled to generate dynamic fluid environments, which would affect the rear robotic fish. Based on reinforcement learning, a relationship was established between energy cost and the body posture of the robotic fish. According to this relationship, the body posture could be acquired which resulted in minimum energy cost for the rear robot. This information was further transferred to the locomotion controller of the robot to adjust its body posture to save most energy.

Loop Corrections to the Decuplet-Octet Baryon Transition Axial Charges

LENG Changzhi, CHEN Xiaolin

2019, 55(3):  411-421.  DOI: 10.13209/j.0479-8023.2019.027

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The authors calulate chiral corrections to the decuplet-octet baryon transition axial charges through O(p³) using heavy baryon chiral perturbation theory (HBCPT). Theoretical predictions are presented. Chiral symmetry breaking, vertex correctiongs, wavefunction renormalization are included. The contributions from both the intermediate decuplet and octet baryon states are taken into account in the loops. The results show reasonably good convergence of the chiral expansion and agreement with the known experimental data.

Interpreting the Contrasted Magnetic Susceptibility Records for the Upper and Lower Parts of a Loess Section in the Southern Tajikistan, Central Asia

SUN Sijia, REN Xiaohuan, SONG Jingjing, ZHOU Liping

2019, 55(3):  422-436.  DOI: 10.13209/j.0479-8023.2019.033

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Loess sequences in southern Tajikistan, central Asia are characterized by the occurrence of alternating loess and pedocomplexes, a feature which is similar to that in the Loess Plateau of north-central China. Previous studies of Tajik loess revealed that below the third pedocomplex (PC3), the loess units and pedocomplexes have distinctly lower magnetic susceptibility than the upper part. No conclusive consensus has been reached on the paleoclimatic interpretation of such a pattern. Here, results of a systematic mineral magnetic study in combination with spectrophotometric measurements on selected samples from Darai Kalon loess section in the southern Tajikistan, central Asia are presented. The mineral magnetic properties suggest increasing concentrations of the ferromagnetic minerals as well as the superparamagnetic and single domain magnetic grains, together with the decreasing hard magnetic components (i.e. contents of hematite or goethite), from the lower part to the upper part of the sequence, which would point to enhanced pedogenesis through time. Such paleoclimate inference is supported by the higher content of hematite in the lower part of the sequence on the assumption that higher temperature and lower precipitation favor the formation of hematite. In this case, the dry climate in the lower part leads to weak pedogenesis. Therefore, there are less superparamagnetic and single domain magnetic grains, which are responsible for the reduced magnetic susceptibility in the lower part. However, the upwards decreasing goethite content revealed by the measurements of diffuse reflectance spectrophotometric data suggests a change towards a drying climate, as formation of goethite requires wet conditions. In this case, the lower magnetic susceptibility below the PC3 may be manifestation of dissolution of superparamagnetic and single domain magnetic grains due to a prevailing humid environment. While the high field (up to 2 Tesla) isothermal remanence shows that the upper part has a lower content of hematite-dominated hard magnetic components, the poor correlation between redness (a*) and the content of hematite in the upper part indicates the strong influence of the matrix effect in the diffuse reflectance spectrophotometric data. Hence, there exists a major uncertainty in the interpretation of the spectrophotometric result of hematite. The overall good negative correlation between the content of goethite and magnetic susceptibility may be interpreted as indicating a trend of drying climate from the lower part to the upper part of the sequence. Such an interpretation is compatible with previous palynological and geochemical studies in the region. This study highlights the complication in the paleoclimate interpretation of the magnetic susceptibility and even mineral magnetic data for loess-pedocomplex sequence in southern Tajikistan. It calls for caution in the application of the models based on the magnetic investigations of Chinese loess and indicates the need of the use of the multiple proxies.

Seafloor Bathymetry Response to Different Time Scale of Magmatic Supply Fluctuation

YUN Xiaorui, LI Jianghai, WU Tongwen, SONG Juechen

2019, 55(3):  437-444.  DOI: 10.13209/j.0479-8023.2018.025

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The finite-difference numerical simulation is used to reproduce the seafloor bathymetry near mid-ocean ridges. The magma supply in the model changes regularly with fluctuation period and amplitude. The results indicate that only when the magmatic supply fluctuation period is greater than the time interval between the formation of two faults on the same side of mid-ocean ridge, the formation process of the seafloor bathymetry can be influenced and recorded. Combined with numerical simulation results and different types of ocean ridge topography, this paper considers that the fast spreading mid-ocean ridge is the only ridges type that can record three magmatic supply fluctuation period of Milankovich cycles (eccentricity (100 ka), obliquity (41 ka) and precession (23 ka)) on the bathymetry. Bathymetry in mid-speed mid-ocean ridges and part of slow spreading midocean ridges with sufficient magmatic supply may be related to the magmatic supply fluctuation period on the 100 ka time scale. seafloor bathymetry in most of the slow-spreading mid-ocean ridges is not affected by magmatic supply fluctuation period of 100 ka or less.

Quantitative Analysis of Potential Tsunami Hazard in the South China Sea

XU Liwen, CHEN Xiuwan, YANG Ting, LI Fei

2019, 55(3):  445-450.  DOI: 10.13209/j.0479-8023.2019.015

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The COMCOT model was used to analyze the potential hazards of the tsunami source in Manila Trench. By changing the information of the two tsunami initial fields — magnitude and source depth, the quantitative relationship between the first wave amplitude and the two is revealed when the tsunami landed in China’s coastal areas. The results show that the influence amplitude of different focal depths on the amplitude of the first wave can reach 50%. With the different magnitude of earthquake, the influence of the focal depth on the amplitude of the first wave is also different. The amplitude of the first wave of the tsunami landing basically increases with the magnitude. However, during the process of the tsunami spreading to the near shore, the tsunami wave will overlap with the reflection wave near the shore, which may cause the first wave landing amplitude to decrease abnormally. When the magnitude reach Mw 8.6, the tsunami level is 1 and some coastal areas will be threatened by tsunami.

Using Artificial Intelligence to Pick P-Wave First-Arrival of the Microseisms: Taking the Aftershock Sequence of Wenchuan Earthquake as an Example

CAI Zhenyu, GE Zengxi

2019, 55(3):  451-460.  DOI: 10.13209/j.0479-8023.2018.036

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In order to accurately and quickly pick up P-wave first-arrival of a large number of seismic events, deep learning method is introduced into the micro seismic P-wave first-arrival picking problem. The structure of convolution neural network is adjusted to apply to the characteristics of the seismic waveform data and first-arrival picking problem. The algorithm takes a 10s-window three-component seismic waveform data as input instead of scanning the continuous waveform. So the running time is far less than traditional methods such as STA/LTA and template matching. The algorithm is applied to aftershocks of 2008 Wenchuan earthquake in July and August, using 7467 manual picked first-arrival data as training dataset. Among the 1867 testing data, 98.9% of the P arrival times picked using this algorithm have an error less than 0.5 s compare to the results picked manually. This method can still maintain good pick-up capability under the condition of low signal-to-noise ratio.

Retrieval of Semi-transparent Cloud Top Height Using Split Window Histograms Method

LIANG Yubing, LI Wanbiao, HUANG Yipeng

2019, 55(3):  461-472.  DOI: 10.13209/j.0479-8023.2019.032

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The split window histograms method was applied to retrieve the cloud top height of semi-transparent clouds in the area of 90°?140°E, 15°?55°N using the AHI data on board Himawari-8 from April 1 to September 30 in 2016. A threshold technique was used to screen the pixels of semi-transparent clouds. The cloud top heights of the pixels were retrieved by using the data of 10.4 ?m and 12.4 ?m split window channels of Himawari-8, and the data of temperature and geopotential on pressure levels from ERA-Interim reanalysis. The retrieved cloud top height was compared with the matched data of CloudSat. It is found that the split window histograms method works well, and the root mean square error of the result is 1.45 km, and the type of land or sea has no significant impact on the result. The method has strong applicability and can be used to the split window channels of different satellites, especially for the theoretical algorithm of FY-4, a new generation of geostationary meteorological satellite in China.

Feature Analysis of City’s Tourism Districts Based on Social Media: A Case Study of Suzhou

WANG Wenfu, CHEN Zihao, SUN Qi, ZHANG Yi

2019, 55(3):  473-481.  DOI: 10.13209/j.0479-8023.2018.033

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A new method is proposed using area feature-tourism districts as analysis unit. Firstly, spatial-temporal behaviors of individual tourists are extracted from social media data. Secondly, the city’s tourism districts are extracted based on spatial-temporal behaviors. Finally, tourism districts are analyzed by 3 kinds of features — ourist activity features, tourist origin features and the structure features of tourism district network using tourism districts as nodes and tourist flow as edges. In the empirical research of Suzhou, 7 tourism districts are extracted based on spatial-temporal behaviors. The spatial structure of tourism districts is generally the same as “1-core-1-corridor-3-district” pattern in Suzhou tourism planning. The feature analysis of Suzhou tourism districts indicates that the Ancient City Tourism District and the Ancient Town Tourism District are the core tourism districts, which attracts tourists from various and distant origins. The tourism districts in and near Suzhou urban area attract more tourists. Suzhou tourism districts have already formed into a multi-core structure. This research shows the effectiveness of extracting city’s tourism districts based on social media data and researching city’s tourism with tourism districts as analysis unit, providing a new approach for research on urban tourism.

Electrochemical Oxidation Mechanism of Sulfamethoxazole in BDD Electrode System

JIANG Huan, WANG Ting, ZHENG Tong, REN Yanfen, Ni Jinren

2019, 55(3):  482-488.  DOI: 10.13209/j.0479-8023.2019.019

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By choosing sulfamethoxazole as the typical pollutant, this paper studied influences of current density and electrolyte solution on electrochemical oxidation by BDD electrode. The degradation mechanism was illustrated through cyclic voltammetry (CV) and intermediates detection using GC-MS. As results, the optimal conditions for SMX degradation were 20 mA/cm² for current density and 0.05 mol/L Na₂SO₄ for electrolyte solution, at which the removal efficiency of SMX was 100% within 50 min, and the degradation kinetics followed pseudo-first order model. At lower current density, the SMX dimer was fabricated due to the electron losen of phenylamino group, which could be directly electrochemical oxidized. While at higher current density, the indirect oxidation by ?OH was the main process. Two possible pathways could occur, one way was conducted due to the break of S-N bond, and the other was the attack to the heterocyclic ring resulting in the breakage of benzene ring. Finally, SMX was mineralized to CO₂, H₂O and inorganic ions. 

Land Use/Cover and Influence Factors in the Lower Yellow River

XIE Yuqian, CHENG Shupeng, ZHANG Yanqing, ZHANG Qi, JIANG Hanlin, LI Zhenshan, ZHAO Zhijie

2019, 55(3):  489-500.  DOI: 10.13209/j.0479-8023.2019.013

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Based on the satellite remote sensing image of the lower Yellow River in 2015–2017, adopting the method of manual interpretation, with ArcGIS, the paper analyzes the present distribution of land use/cover type of the lower Yellow River. Based on social and economic statistics, analyze the factors are analyzed affecting the distribution of land use/cover in the lower Yellow River. The results show that the land use/cover on the lower reaches of the Yellow River is mainly used for development, among which the most priority is the cultivated land without facilities, which is accounting for 77.99%, followed by land for survival, accounting for 6.63%. The width of river, the area of the land, the village and the land for industry of the part from Taohuayu to Gaocun is more than that of other parts. The type of land use/cover of the lower Yellow River is quite simple. The area of the land of the lower Yellow River, the economic situation, the attraction of the city development and the water conservancy facilitie around affects land use/cover. The area of the village, the farm land with facilities and brickyard grows with the area of land. The fish ponds and the land for industry appear mostly in lands with better economic situation. Farm land with facilities and land for industry appear mostly in those lands near downtown.

A Preliminary Metabolomics Study on Air Pollution Associated Acute Biomarkers of Health Effect Based on a Migration Panel between Los Angeles and Beijing

XIE Tianning, LIN Yan, QIU Xinghua

2019, 55(3):  501-508.  DOI: 10.13209/j.0479-8023.2019.014

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A panel study was conducted between Los Angeles and Beijing with 14 healthy young subjects of exchange students from University of California Los Angeles. Urine samples were collected repeatedly and analyzed with a metabolomics approach based on gas chromatography-mass spectrometry (GC-MS) to investigate the markers of early biological response. Multivariate statistical analyses were applied to screen the significantly changed metabolites, which were further identified based on GC-MS signals. Meanwhile, concentrations of ambient air pollution in the communities where subjects lived were cited from monitoring stations, and a linear mixed-effects model was used to estimate the association between oxidative damage biomarkers and concentration of gaseous pollutants and PM2.5. The results indicated that these discriminating metabolites between Los Angeles and Beijing were related to energy metabolism, oxidative damage, gastrointestinal flora, metabolism of protein and RNA (such as cell apoptosis). Effect of oxidative damage especially stood out in Beijing, with allantoin as well as L-cystine and pseudouridine as significantly changed biomarkers. The results also showed a potential positively association between allantoin and PM_2.5 in prior 0–96 h, CO in prior 0–24 h, NO₂ in prior 24–48 h, O₃ in prior 48–72 h, and SO₂ in prior 24–72 h. These evidences might suggest that the different pollution between Los Angeles and Beijing could change the oxidative burden, and body might relieve this burden through energy metabolism in return.

Response of Habitat Quality to Land Use Change Based on Geographical Weighted Regression

WANG Hui, XU Yueqing, LIU Chao, HANG An, LU Longhui, ZHENG Weiran

2019, 55(3):  509-518.  DOI: 10.13209/j.0479-8023.2019.017

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Based on land use data of Zhangjiakou in 2000, 2010 and 2015, this paper investigated the spatiotemporal variation of habitat quality pattern of Zhangjiakou City by using InVEST, in order to understand the spatial patterns associated with the change of land use and habitat quality change, further introducing the geographical weighted regression (GWR) model, to quantitativly analyze the influence of cultivated land, woodland, grassland and construction land change on the evolution of habitat quality. The results showed that in the year 2000–2015, cultivated land, forest land and grassland were the main types of land use in Zhangjiakou City, during the reduction of cultivated land, forest land and construction land kept increasing, with farmland to woodland, grassland and construction land, grassland to forest landand construction land as the main transfer directions of change. During 2000–2015, Zhangjiakou City habitat quality was at a higher level overall and kept improving. Habitat quality was highest in northeast mountain area, Bashang plateau and the the Sanggan River valley region was lower, and the lowest level of habitat quality was in Yanghe River watershed. The influence of each land use type on habitat quality had significant spatio-temporal heterogeneity, and the change of forest land was positively correlated with habitat quality overall and most influential. The grassland had a positive correlation with the habitat quality, and its regression coefficient decreased from north to south. The main performance of cultivated land, construction land and habitat quality was negative correlation in space, but some area was positive correlation. The reason for the large heterogeneity of the regression coefficients in different regions lied in the different dominant types of habitat quality changes in different regions. The change of habitat quality in the plateau area and the northeast mountain area was mainly affected by woodland and grassland changes, and in Sanggan River and Yanghe River, the change of habitat quality basin for cultivated land and construction land.

Relative Abundance of Anammox Bacterial Marker Genes in the Lower Yangtze River and Their Affecting Factors

WANG Haiying, PAN Rui, LIU Shufeng, ZHAO Yunpeng, DANG Chenyuan, NI Jinren

2019, 55(3):  519-525.  DOI: 10.13209/j.0479-8023.2019.021

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In order to investigate the distribution of anammox bacteria in river ecosystems, water and sediment samples were collected at 6 sites along the lower Yangtze River in spring and autumn in 2014. Clean reads of metagenomic sequencing were BLAST against self-constructed datasets of anammox bacterial marker genes hzsA, hzsB, hzsC and hdh, and valid hits were used to calculate their relative abundances. As results, average relative abundances of hzsA, hzsB, hzsC and hdh genes in water were extremely low due to the excess dissolved oxygen which was not suitable for anammox bacteria. Whereas, the average relative abundances in sediments were much higher, i.e., 4.540×10^-10, 4.939×10^-10, 4.333×10^-10 and 2.859×10^-10, respectively. Due to the temperature rise, average relative abundances of hzsA, hzsB, hzsC and hdh genes in sediment samples in autumn were higher than those in spring. From the changes alongside the river, average relative abundances of hzsA, hzsB, hzsC and hdh genes at Datong, Nanjing and Xuliujing were relatively higher, which was due to anthropogenic activity and salinity increase in the estuary. Based on the results of taxonomic identification, anammox bacteria in the lower Yangtze River mainly consisted of Candidatus Brocadia and Candidatus Jettenia at genus level. Relative abundances of hzsA, hzsB, hzsC and hdh genes were related to NO₂^--N, NO₃^--N and NH₄⁺-N concentration, of which NO₂^--N concentration was the restrictive factor as it was much lower than NH₄⁺-N concentration.

Grain for the Green Spatial Pattern Optimization in the Middle Reaches of Heihe River Based on Water Carrying Capacity

MENG Jijun, ZHOU Zhen, KUO Lijen

2019, 55(3):  526-536.  DOI: 10.13209/j.0479-8023.2019.030

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This paper takes the middle reaches of Heihe River as the study area, where has the most concentrated oasis in Northwest China with fragile ecological environment and huge conflict between water supply and demand. The water carrying capacity was analyzed based on SD model. Then, the land use quantity structure optimization was carried out by grey linear planning model under the constraint of water resource carrying capacity. Next, the probability of cultivated land, forest and grass land was calculated by the space optimization module of Dyna-CLUES model, and the optimized spatial pattern were identified through probability game. The results show that when the balance between the supply and demand of water resources is achieved in 2020, the research area can support 1.44 million people, 7.973 billion industrial added values, separately the forests, grass land and cultivated land that the research area can support is 953.535 km², 3947.115 km² and 3027.88 km². The best landscape quantity structure include 2742.49 km² cultivated land, 846.456 km² forest, 2184.57 km² grass land, 170.671 km² water area, 364.509 km² construction land and 13289.23 km² unutilized land. The implementation of returning cropland to forests can enhance the ability of oasis areas to resist hazards caused by wind and sand, mainly in Gaotai, Linze and Ganzhou. The locations of returning cropland to grassland focus in Shandan and Sunan with high altitude, steep slope and poor water, which have poor soil condition and is inappropriate for forest. Forest plantation locations focus in the periphery of cropland in Minle and Shandan, and those areas mainly are flat unused land with good water resource conditions, which are of great significance for water and soil conservation, wind prevention and sand fixation.

Analysis of the Premium of Second-Hand Housing Prices in Surrounding Communities in Middle School Districts: Taking Shenzhen as an Example

LIANG Liyu, GUO Zhiqiang, LI Junxiang, LÜ Bin

2019, 55(3):  537-542.  DOI: 10.13209/j.0479-8023.2019.024

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This paper selects the data of 185 residential quarters in three major urban districts of Shenzhen, and establishes a characteristic price model by quantitatively analyzing the quality of secondary schools to study the impact of secondary education facilities in Shenzhen on the degree of capitalization of housing prices. The results show that among the factors affecting the second-hand housing prices in the surrounding areas of middle schools, the characteristics of the school have significant influences. Among them, the rate of higher education, teachers and key schools above the school are positively boosting the prices of second-hand houses, while the effect of the student-teacher ratio is negative. At the same time, there are differences in the characteristics of schools between provincial middle schools and non-provincial middle schools affecting the second-hand house prices. Among them, the prices of second-hand houses in non-provincial middle schools are mainly influenced by school characteristics such as the rate of enrollment and student-teacher ratio, while in the vicinity of provincial middle schools, the price is mainly influenced by the number of teachers and the student-teacher ratio. The distance from the subway, CBD and the age of the building have a negative impact on the housing prices around the middle school, and each additional 1 km from the major commercial service centers and subway stations, house prices fell by 13.9% and 28.7% respectively. For every one year of building age, house prices fell by 6.8%. This study reveals the impact and extent of the quality characteristics of secondary education on residential prices, and more comprehensively reflects the impact mechanism of housing prices in Shenzhen secondary school districts.

Pollution Characteristics and Ecological Risk of Perfluorinated Compounds in a Rapidly Urbanizing Catchment

WANG Zhifen, LIANG Xinxiu, ZHAN Bicheng, WU Jiang, GAO Yue, XU Nan

2019, 55(3):  543-552.  DOI: 10.13209/j.0479-8023.2019.029

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To investigate the pollution characteristics of eleven perfluorinated compounds (PFCs) in a rapidly urbanizing catchment, water samples from the Guanlan River in Shenzhen were collected during the dry season and the wet season. All the samples were pretreated by solid-phase extraction and analyzed using ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry with electron spray ionization (UPLC-ESI-MS/MS). The results indicated that the concentrations of PFCs in the mainstream of Guanlan River during the wet season and dry season were 179.15–613.68 and 37.04–103.70 ng/L, respectively. Perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS), perfluorohexanoic acid (PFHxA), and perfluorooctanoic acid (PFOA) were the predominant pollutants. The concentration of PFCs in the wet season was higher than that in the dry season, and the concentration of PFCs in the downstream was higher than that in the upper and middle stream. Compared with other water body in the world, the levels of PFCs in Guanlan River were relatively high due to the rapid urbanization in the region. The ecological risk of PFCs to aquatic organisms was neglectable.

Seasonal Patterns and Their Determinants of Non-structural Carbohydrates in Different Tree Species at Xeric Timberline

SHANGGUAN Huailiang, LIU Hongyan, HU Guozheng, GUO Weichao

2019, 55(3):  553-560.  DOI: 10.13209/j.0479-8023.2019.016

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To examine the seasonal patterns of non-structural carbohydrates (NSC) in different tree species and the roles of biotic (tree species) and abiotic (climate) factors on these patterns at xeric timberline, the authors monitored seasonal patterns of non-structural carbohydrates in four different tree species (Pinus sylvestris var. mongolica, Betula platyphylla, Populus simonii and Larix principis-rupprechtii) in southeastern Inner Mongolian Plateau of China. The results show that tree species with different foliar habit types have broadly similar seasonal non-structural carbohydrates (NSC) patterns (NSC concentration increased at the beginning of the growing season, and reduced in summer because of high growth rate, then increased slowly in the end), which suggests a climatic determination. Significant differences (p<0.05) in NSC concentrations are observed between four tree species. NSC concentration in birch is significant higher than that in pine, reproducing the pattern that deciduous species have higher NSC pool than ever green ones, which suggests a biotic determination. Due to the relatively drier climates, NSC concentration in larch and poplar turn to be lower than that in pine, implying a combined effect of both biotic and abiotic factors. The sugar and TNC (total non-structural carbohydrates) concentrations in leaf are significantly higher than those in stem, but the starch concentration in leaf is lower, which is consistent with the different roles of leaf and stem. 

Study on Nitrogen Release from Reservoir Sediments and Nitrogen Removal by Aerobic Microorganism

XIE Minzheng, CHEN Qian, DANG Chenyuan, PAN Boyue, AN Rui, WU Zhe, ZHOU Ming

2019, 55(3):  561-570.  DOI: 10.13209/j.0479-8023.2019.018

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This study focuses on the Danjiangkou reservoir, and investigates the release regulation of total nitrogen, nitrate, nitrite and ammonia from sediments as a function of temperature, perturbation and aeration conditions. Moreover, a simulation reactor was set up to explore the elimination of endogenous nitrogen pollution through high-efficient aerobic denitrification microorganism augmentation. Effects of high-efficient aerobic denitrification microorganisms on the microbial community structure in the sediments was also evaluated by means of high-throughput sequencing technology. The results indicated that increasing temperature could promote the release of nitrate and nitrite from sediments, while inhibiting the release of ammonium. Disturbances of water was beneficial to nitrogen release from sediments, and the nitrogen amount accumulated in the overlying water was proportional to the agitation speed. Concentrations of dissolved oxygen had great effects on the nitrogen release from sediments. It was found that the aeration treatment significantly reduced the release of total nitrogen and nitrite from sediments, and the subsequent accumulation in water. After addition of the a high-efficient aerobic denitrification bacteria Pseudomonas stutzeri (PCN-1) into the simulation reactor, concentrations of all the forms of nitrogen in the reactor increased at first and then decreased. On the 65th day of the experiment, removal rates of total nitrogen and nitrate released from sediments were as high as 75.87% and 79.96% respectively, suggesting effective control of the endogenous nitrogen. The relative abundance of Proteobacteria, Bacteroidetes and Spirochaetes in sediments was significantly increased after PCN-1 addition, so the microbial community structure in the sediments was changed by microbial augmentation treatment with PCN-1 as well.

Community Structure Characteristics of Phytoplankton and Their Relationship with Environmental Factors in the Typical Section of Chin-sha River

GAO Qi, NI Jinren, ZHAO Xianfu, CHEN Wenzhong

2019, 55(3):  571-579.  DOI: 10.13209/j.0479-8023.2019.022

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To study the community structure characteristics and main influencing environment factors of phytoplankton in the Shigu-Yibin section of Chin-sha River, six sites were set up in the autumn of 2014 to monitor planktonic algae communities. A total of 52 species of 6 phyla, 30 genera of algae were identified through microscopy. Diatoms were dominant species, which accounted for 65.38%, 74.07%, and 80.65% by species numbers, cell density, and biomass respectively. The total algal density and biomass of phytoplankton decreased at the dam and gradually increased under the dam. They were the highest in Shigu and the lowest in Xiangjiaba. The diversity of phytoplankton communities in Panzhihua was the highest, and that of Xiluodu and Xiangjiaba were much lower. The redundancy analysis (RDA) showed that total nitrogen was the main factor affecting the phytoplankton community structure. The correlation between the dominant species and the environmental factors showed that six diatoms, including Synedra acus and Achnanthes sp., were positively correlated with water level and negatively correlated with water temperature, indicating that they were suitable for low temperatures, while Cyclotella sp. was suitable for growing at high temperature. Coelastrum reticulatum, Scenedesmus sp., Chroomonas acuta and Cyclotella sp. were positively correlated with total nitrogen, while Cymbella Affinis and Nitzschia palea were positively correlated with total phosphorus, which demonstrated that they could indicate corresponding nutrients in water.

Soil Temperature Triggers Sap Flow Onset and Offset of Pinus tabulaeformis

WANG Yue, YAN Chunhua, QIU Guoyu

2019, 55(3):  580-586.  DOI: 10.13209/j.0479-8023.2019.028

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TDP (thermal dissipation probe) technology was used for continuous observation and preliminary study of the secondary dominant tree species Pinus tabulaeformis in Jiuzhai Valley. A temperature sensor was used to collect soil temperature gradients from 2013 to 2015 with 6 depth gradients at 3, 10, 20, 30, 40, and 50 cm below the tree. The analysis showed that the temperature of surface soil in the shallow 3 cm soil layer in early spring had a stronger influence on the sap flow intensity than the deep soil temperature and air temperature (correlation coefficient was 0.852). The temperature gradient analysis reported that the optimum temperature for the root system was 4.0–7.9°C. With the increase of soil temperature, the characteristics of sap flow initiated by Pinus tabulaeformis in March and April would exacerbate the decrease of early spring runoff in Jiuzhai Valley. 

Responses of Herbaceous Community Characteristics and Biomass to Nitrogen Addition in a Larix principis- rupprechtii Plantation

QU Tiantian, YAN Tao, ZHANG Wen, ZENG Hui

2019, 55(3):  587-596.  DOI: 10.13209/j.0479-8023.2019.023

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The research was conducted in a sapling Larix principis-rupprechtii, plantation set three nitrogen addition levels (0, 20 and 50 kg N/(ha·a), called N0, N20 and N50), in order to assess the influence of nitrogen addition on plant communities characteristics and above-ground biomass. The results showed that nitrogen addition altered soil micro-environment, reduced soil temperature and significantly increased soil moisture. Nitrogen addition partly promotes the growth of herb community (increased by 6.83% and 6.83% in N20 and N50 in 2014, respectively, compared with the control; while increased by 9.80% and 6.83% in N20 and N50 in 2016, respectively, P>0.05). The community coverage and aboveground biomass were significantly and positively correlated with soil moisture (P<0.05). The diversity and evenness had no significant response to nitrogen addition, but N20 significantly increases the species richness per area (significantly increased by 23.33% in N20 samples in 2014, P<0.05). Nitrogen addition exerted different influences on plant functional groups, i.e., nitrogen addition promoted the growth of polygonaceae and cyperaceae plants, restrained gramineae and compositae plants and had no influence of leguminous plants. The results suggested that herb communities are sensitive to nitrogen addition in temperate Larix principis-rupprechtii plantations, and nitrogen addition partly promotes the growth of herb plants and changes competition among different herbaceous plants functional groups.