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    05 May 2019, Volume 39 Issue 3 Previous Issue    Next Issue
    The Initiation Time of the Holocene Coral Reef at the Chenhang Island (Xisha Islands) and Its Significance as a Sea Level Indicator
    Qin Yeman, Yu Kefu, Wang Rui, Jiang Wei and Xu Shendong
    2019, 39 (3):  319-328.  doi: 10.13284/j.cnki.rddl.003128
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    This study relies on analyses of the top layer of the material extracted from Well Chenke-2, which is part of a coral reef drilling program in the south-east of Chenhang Island, Xisha Islands. The age of the material at the bottom of the borehole was determined by high-precision uranium dating technology. Five coral samples were selected for the U-Th dating. The five groups of data can be clearly dated to the Holocene or to the Pleistocene. The Holocene part includes samples CK2-15, CK2-16, and CK2-17. Their age was determined as 7 914 ± 67, 7 552 ± 73, and 7 584 ± 55 years, respectively. The Pleistocene part includes samples CK2-18 and CK2-19. Their age was determined as 112 700 ± 700 and 128 100 ± 1 000 years, respectively. Furthermore, a MAT-253 isotope mass content of δ13C, δ18O, and strontium in 21 whole rock samples extracted in the depth interval 0-21 m. Based on the contents of these three elements, the interval can be divided into two parts. The content of δ13C, δ18O, and strontium in the depth interval 0-16 m is higher, with average values of 0.647‰, -3.392‰, and 0.843%, respectively, than that in the depth interval 17-21 m, with average values of -3.185‰, -7.994‰, and 0.174%, respectively. On the basis of the U-Th age, and considering that the contents of δ13C, δ18O, and strontium decrease evidently between 16 and 17 m, it can be concluded that the boundary between the Holocene and the Pleistocene corals is located at a depth between 16 and17 m in Well Chenke-2, and that the age of the corals determined by uranium dating in the upper part of the boundary represents the initiation time of the Holocene reefs. Therefore, it is concluded that the Holocene coral reefs in Chenhang Island started to develop 7 900 years ago, basically simultaneously with most of the Holocene reefs in the Indo-West Pacific, Central Pacific, and Caribbean. The Holocene reefs are 16.7 m thick, and are in unconformity with the late Pleistocene coral reefs (aged 110 ka). Considering the relative stability of the Neotectonic activities in the study area, as well as the fact that the reef flat of the modern coral reefs in the South China Sea is basically located at the low tide height, and that the borehole of Well Chenke-2 is located approximately 2.9 m above the modern reef flat, it is speculated that the top of Well Chenke-2 was originally located about 13.8 m below the low tide level of the modern sea. In other words, the sea level at Xisha Islands 7 900 years ago was about 13.8 m below the modern sea level. This result provides new information for understanding the development history of the Holocene coral reefs in the South China Sea and the sea level changes in the area.

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    Simulation of Living Coral Cover Changes around the Weizhou Island
    Zhang Huiya, Huang Rongyong and Yu Kefu
    2019, 39 (3):  329-336.  doi: 10.13284/j.cnki.rddl.003143
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    Owing to their extensive biodiversity-rich ecosystems, coral reefs are called the “tropical rainforests of the sea.” They are of great importance as they can help to maintain the ecological balance, biological resources, and species diversity on Earth. However, coral reefs are globally threatened by many factors, including human activities and climate change, and the live coral cover (LCC), regarded as the best measure of coral reef health, is declining. Therefore, it is necessary to manage and protect coral reefs when they are exploited and utilized. Such management and protection should be based on an understanding of the knowledge of the impacts of the environment on the ecological status of the coral reef. To aid our understanding of this knowledge, studies were conducted at The Weizhou Island. The corresponding live coral cover (LCC) data recorded in the historic documents and three environmental parameters obtained by MODIS (2003-2015), i.e. chlorophyll- a concentration (Chl-a), sea surface temperature (SST), and photosynthetically active radiation (PAR), were used to explore the relationship between the LCC and the environmental parameters. First, several environmental parameter statistics that have the greatest impact on LCC were calculated and chosen, and then principal component analysis (PCA) was used to remove the redundant information. Thereafter, to overcome the difficult caused by the absence of LCC data in some years for the study sites, a nonlinear constrained optimization method was used to construct the relationship between the LCC and the environmental parameter statistics. The coefficients of the environmental parameter statistics were found to be -0.109 04, -0.061 62, and 0.013 58 for Chl-a, SST, and PAR, respectively. These values indicate that the Chl-a around the Weizhou Island had the most negative impact on LCC, followed by SST, whereas PAR has the least negative impact on LCC. Finally, the future development of the LCC around the Weizhou Island was simulated. Accordingly, the LCC around the Weizhou Island was seen to become stable at approximately 10% if the environmental conditions remain constant. However, owing to the current climate warming trends, it is possible that the corals will begin to disappear in approximately 2120. Therefore, although the Weizhou Island is considered as one of the refuges of corals from global warming under the “Refuge Hypothesis” , the corals around the Weizhou Island are still at risk of disappearing as the global climate continues to become warmer. These factors were rarely considered in previous studies, so this study is an innovative application of remote sensing to the research on coral reefs.

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    Occurrence, Distribution and Source Analysis of Polycyclic Aromatic Hydrocarbons (PAHs) in the Surface Waters of the Lianzhou Bay and Sanniang Bay, Guangxi
    Wang Weiquan, Zhang Ruijie, Yu Kefu, Wang Yinghui, Pan Changgui and Zeng Weibin
    2019, 39 (3):  337-346.  doi: 10.13284/j.cnki.rddl.003141
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    Concentrations of 16 PAHs in 14 surface seawater samples were analyzed with solid phase extraction and gas chromatography-mass spectrometry. These samples were collected from estuaries and coasts of the Lianzhou Bay and Sanniang Bay in summer and winter. The results show that the average concentrations of individual PAHs were positively correlated with their solubilities and polarities. Two- and three-ring PAHs were the predominant compounds, with higher detection rates and concentrations than PAHs with 4-6 rings. In summer, the mean of ∑16PAHs (total concentration of 16 PAHs) was significantly higher in the estuaries (72.71 ng/L) than at the coast (56.28 ng/L) (t-test, p<0.01). In winter, the means of ∑16PAHs between estuaries (106.67 ng/L) and the coastal zone (92.43 ng/L) were not significantly different (t-test, p>0.05). The average ∑16PAHs for both estuaries and coast were significantly higher in winter than in summer (t-test, p<0.05). The concentrations of the 2-ring and 3-ring PAHs exceeded 97% of the ∑16PAHs. The proportion of 2-ring PAHs was significantly higher in winter (85%-86%) than in summer (68%-69%), while the proportion of 3-ring PAHs was higher in summer (29%) than in winter (14%). In either season, the proportions of PAHs in the estuaries and coastal waters were similar, indicating that they have the same source, and that the rivers have a significant impact on coastal pollution. In summer, ∑16PAHs was higher in the Nanliu River (74.98 ng/L) than in the Dafeng River (58.92 ng/L); while in winter the ∑16PAHs in the Dafeng River (154.94 ng/L) were significantly higher than in the Nanliu River (90.58 ng/L). In summer, the ∑16PAHs was higher in Sanniang Bay (56.62 ng/L) than in Lianzhou Bay (55.93 ng/L). In winter, the ∑16PAHs in the Sanniang Bay and Lianzhou Bay were both about 90 ng/L, which were 1.5 and 1.7 times higher than their corresponding concentrations in the summer. Whether in summer or winter, the PAHs in Sanniang Bay and Lianzhou Bay mainly consisted of 2-ring and 3-ring PAHs, accounting for over 90% of the total. Five-ring PAHs were only detected in Sanniang Bay. The total flux of 16 PAHs in the two rivers was 525.3 kg/a. The rainy season contributed more than 85% of the total flux, reflecting the apparent impact of the rivers on the coast during the rainy season. The Nanliu River discharged more than 87% of the total flux of the 16 PAHs for the two rivers, because of its massive runoff. The results of source analysis using principal component analysis and isomer ratio analysis both showed that the PAHs in the surface waters of Sanniang Bay and Lianzhou Bay were from mixed sources of combustion and petroleum in summer, but mainly from combustion sources in winter. Compared with other countries or regions worldwide, the levels of PAHs in Lianzhou Bay and Sanniang Bay were moderate. The ecological risk assessment results showed that the ecological risk from the PAHs in this study was low.

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    Accumulation and Migration of Heavy Metals in Mangrove Sediments and Plants in the Nanshan Town, Xuwen
    Luo Songying, Liang Yiqiong, Chen Bishan, Lin Mengting, Liang Jiaxin and Qiu Jinkun
    2019, 39 (3):  347-356.  doi: 10.13284/j.cnki.rddl.003132
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    In the present study, we investigated the distribution, accumulation, and migration of heavy metals in mangrove sediments and plants in Nanshan Town of Xuwen County. The mangrove sediments and different parts of mangrove plants (roots, stems, and leaves) were collected, and their heavy metal contents were determined and analyzed using enrichment factors, bioaccumulation factors, transfer coefficients, and correlation analysis. The results showed that: 1) The heavy metal content in the sediments of mangrove wetland exhibited the order Cr>Zn>Ni>Cu>Pb>As>Hg>Cd, with a moderate degree of variation. Except Ni, the other seven heavy metals did not exceed the national first-class standard, and except Pb, the other seven heavy metals exceeded the background value of soil environment in Guangdong Province, indicating the existence of a certain accumulation effect in the process of heavy metal deposition in the study area. 2) The Enrichment Factors of As, Cu, Zn, Hg, Ni, and Cr in the sediments were greater than 1.5, indicating a potential effect of slight human activities. The Enrichment Factors of Ni were greater than 5 at each station. Combined with the background of the study area, it reflected that the Ni content was affected by both natural and human inputs. 3) The heavy metals were mainly concentrated in the roots of Avicennia marina, but were relatively uniform in the roots, stem, and leaves of Rhizophora sty losa. The contents of heavy metals in different parts of A. marina were much higher than those in the corresponding parts of R. sty losa, indicating that the heavy metal adsorption capacity of A. marina was stronger than R. sty losa. Hg was concentrated in the leaves of plants, and the correlation between Hg and other heavy metals was not obvious, indicating that they had different sources. It was speculated that Hg mainly enters the plants through leaves, mostly from transportation pollution through atmospheric deposition. 4) Different mangrove plants exhibit different enrichment abilities for different heavy metals. The enrichment ability for different heavy metals followed the order Cd>As>Cu>Zn>Hg>Pb>Ni>Cr in A. marina and Cd>Cu>Hg>Zn>Pb>As>Ni>Cr in R. sty losa. Both A. marina and R. sty losa had strong transport capacities for Hg. Rhizophora sty losa has a strong ability to enrich and transport Cd, whereas A. marina has a strong ability to enrich Cd, but a weak ability to transport Cd, indicating that there is no direct relationship between the accumulation and transport capacity of heavy metals in mangrove plants.

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    Application of Sentinel-1A Data in Offshore Wind Field Retrieval within Guangdong Province
    Wu Pinghao, Zhong Kaiwen, Hu Hongda, Zhao Yi, Xu Jianhui and Wang Yunpeng
    2019, 39 (3):  357-364.  doi: 10.13284/j.cnki.rddl.003137
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    Offshore wind energy resources are a common clean energy source. They have rich reserves and are widely distributed, inexpensive, and safe with few environmental constraints and large selection space. They exhibit considerable development and utilization prospects. In this paper, wind direction data were extracted based on wind stripes from Sentinel-1A data, and the CMOD5 retrieval model was used to invert the wind field in the offshore waters of Guangdong Province in March, May, July, and December 2017. Eight sites were selected, and 56 samples were compared with measured data; the sample wind speed was generally higher than measured wind speed. The mean absolute deviation (MAE) of wind speed retrieval was approximately 1.98 m/s, the root mean square error (RMAE) was approximately 2.74 m/s, and the correlation coefficient was 0.8. The wind speeds in March, May, and July were relatively close, and the MAE and RMSE were all under 2 m/s, while the average wind speed in December was above 8 m/s with a higher deviation in MAE and RMSE as the measured data did not exactly reflect satellite transit times. A comparison of the December CCMP data with the measured site data revealed a mean absolute deviation of approximately 2.96 m/s, root mean square error of approximately 4.02 m/s, and correlation coefficient of approximately 0.59. Differences were observed between the CCMP data and the measured data in December, which was similar to the retrieved wind speed data. G3358, G7427, G3704, and 59490 station errors were calculated by the four stations with the largest errors in December. The G3358 station exhibited the most significant errors: the mean absolute deviation was approximately 3.43 m/s and the root mean square error was approximately 5.01 m/s. The data period in which the G3358 station data exhibited the highest error was December 2017, and CCMP wind field data was interpolated to the study area at this period. It was found that the G3358 station is located at the wind speed stage of 12-15 m/s, which is nearest to the large wind speed area in all stations. The reason for the large deviation between the measured site data and the retrieval wind field and CCMP wind field may be related to the higher wind speed. The results of Sentinel-1A image retrieval were consistent with the measured data overall, which verifies that the COMD5 model is applicable to offshore high-resolution marine wind field data retrieval in Guangdong Province, and it provides a possibility for future research on wind energy resource and reserves estimation in Guangdong Province.

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    Variation in Turbulence Degree with Height and its Dependence on Urban Macroscopic Topography
    Li Daquan, Sun Wu, Ouyang Ruikang, Huang Sheng, Gao Mengyuan, Li Qingxiang and Huang Qiming
    2019, 39 (3):  365-376.  doi: 10.13284/j.cnki.rddl.003127
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    Wind speed and turbulence are two closely related indicators that measure the properties of a wind profile. Obtaining an insight into the development of turbulence over a complex urban terrain can help deepen the understanding of the performance of urban wind farms. In this research, three building models with vertical scales 1:2000, 1:1000, and 1:500, respectively, were constructed. Using large boundary-layer wind tunnels and generating wind from two directions (northwest and southeast), the variation in turbulence with height over a complex urban terrain, and its dependence on the macroscopic terrain characteristics, were analyzed in a neutral flow simulation. Based on the experimental data obtained in the wind tunnel, the two model coefficients A and B were determined with respect to four types of boundary-layer roughness, under neutral flow or with turbulence varying with height at different vertical scales. In both cases, the average correlation of the proposed model was about 0.8. A close relationship between the wind profile index and the turbulence at different heights was observed. Based on the profile index α the turbulence at different heights could be predicted, so that the variation in turbulence with height over a complex urban terrain could also be quantified. Generally speaking, the turbulence decreases with altitude, and the maximum turbulence develops at the bottom. However, there are exceptions. It is common that the turbulence of the hole at the lowest measuring point is not the largest, which makes the shape of turbulence change with the height like a hook. The shape of turbulence varying with height can be summarized into four types. The height at which the maximum turbulence occurs is found to be concentrated in the range 0-0.2 h (where h is the dimensionless unit), which makes up more than 80% of the total number. Therefore, in the height range 0-0.2 h above the urban terrain, the wind direction and velocity of the airflow showed complex patterns, and turbulence is extremely developed, with an important impact on the diffusion of urban pollutants and the transfer of heat. Using the existing model, the main coefficient of the turbulence model corresponding to a given height could be determined, with high precision accuracy, according to the four kinds of boundary-layer roughness and the different vertical scales. The development along the height of the non-maximum turbulence intensity depended on the difference between the actual wind profile and the standard wind velocity at the same height, whereas the maximum turbulence level under the given urban topography occurred within the narrow range 0-0.2 h. The turbulence degree index β was used to characterize the variation of turbulence intensity with height. The exponential β of the turbulence intensity decreased with increase in the exponential alpha of the profile, regardless of the shape of the terrain (e.g., a ridge or a flat terrain). It was shown that the overall turbulence profile increases from the upwind and top areas to the leeward area, and increases gradually along the wind flow direction. Turbulence profile also has a strong dependence on the terrain and the wind path, and has the same flow characteristics as those over a simple terrain. At the same time, the shape of the β isolines of the three models did not show the same overlap. On the contrary, great differences were observed. This shows that in the past, when the wind tunnel simulations were carried out, the method of ensuring the number of thunderbolts simply by increasing the vertical scale was affected by a large uncertainty.

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    Delimitation of Urban Development Boundaries Using Two Basic Evaluations and FLUS-UGB: A Case Study of Changchun
    Zhang Shaoyue,Liu Xiaoping,Yan Shizhong,Zhan Qiang and Liu Tongqi
    2019, 39 (3):  377-386.  doi: 10.13284/j.cnki.rddl.003136
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    The reform of the ecological civilization system and mechanism has provided a background upon which the “three lines” delineation acts as an important avenue for optimizing land organization and natural resource management. The urban development boundary-as the rigid bottom line for controlling town land use and expansion-is essential to the forced transformation of the city and the improvement of urban governance and governance capabilities. However, most existing methods of setting urban development boundaries emphasizes the urban factors alone or simply coordinates the urban development boundary with ecological and agricultural elements; they rarely examine urban development boundaries from the perspective of global pattern optimization, thus causing many issues to align with pre-technical, post-management management. Additionally, after the 18th National Congress, China entered a new governance stage that identifies problems using systematic problem solving and has gradually implemented this problem-solving framework. Therefore, the study of urban development boundaries should be reformed from a direct or partial perspective to a comprehensive perspective. By adopting systematic thinking, this study considers all elements of national land space and the coordination of various stages of spatial planning and then presents a systematic method with which urban development boundaries may be delineated, including two basic evaluations, three types of space division, and urban development boundary delimitation. Specifically, the section on the two basic evaluations identifies environment backgrounds by overlapping assessment. With the resource and environment carrying capacity evaluation, the resource endowment level and carrying capacity constraints can be identified by rating and summarizing major natural elements. And with the space development suitability evaluation, under three different developing orientation, the suitability level of ecological, agricultural and urban functions can be determined by rating and summarizing both natural and human factors. The section exploring three types of space division emphasizes land use type determination, the process by which authorities select the most suitable land designation based on the space development suitability evaluation result and functional development priorities, thus extracting urban development space. The urban development boundary delimitation section includes the FLUS-UGB model, which utilizes the random forest model to select input factors; the cellular automata model to simulate city dynamic evolution; and policy and planning factors that revise spatial growth trends and delimitate boundaries morphologically. This study presents Changchun City as an example, using land use data from 2010 to 2015 to perform model simulation and accuracy verification with an overall accuracy score of 0.922 3 and Kappa of 0.844 6, which indicates that this model is highly accurate. We then use this model to delimitate the urban development boundary of Changchun City in 2035 and formulate effective control measures. This method progresses from background values to suitable target values and control values, recognizing natural endowments and integrating function and optimize layout. Thus, it comprises a complete urban development boundary delimitation framework, which works toward establishing development and protection patterns of land space in Changchun City and provides a reference for further domestic research.

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    Exploration and Practice for the Third National Land Survey in China’s Rapidly Urbanizing Area: A Case Study of Dongguan
    Huang Yingbing, Xu Qiheng, Wu Yingbin and Lin Zhuoren
    2019, 39 (3):  387-396.  doi: 10.13284/j.cnki.rddl.003144
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    Four towns in Dongguan city in the Pearl River Delta were chosen as a typical urbanization region and as pilot sites for the third national land survey. The overall planning and design involved pilot contents, typical choice, pilot approaches, study route, quality control, etc. Data source category selection was proposed according to the quality of referable base maps for land surveys, and three data combination models were used for comparative experiments. From the perspective of investigative technology, the implementation approach consisted of three key stages: indoor operation for map interpretation or data analysis; field operation for investigation and verification; and final indoor operation for database construction. In this study, pilot exploration and practice utilized special reports, statistical tables, maps, and databases, yielding rich research findings. Taking the land use survey as an example, the differences and spatial pattern characteristics of each pilot area that has experienced rapid urbanization were analyzed. Meanwhile, seven key technical issues were discovered: the use of confidential basic data, proof of inconsistent map spots, processing of tiny map spot, identification standard of land class, spatial mismatch of multi-source data, database structure, and core association of identification code. The advanced and highly efficient implementation measures were studied to provide a series of pilot experiences. The pilot results provide an important basis for meticulous land management during a new period for the four pilot areas. Additionally, prior knowledge and reference samples were provided for the third national land survey in Dongguan or for other highly urbanized areas.

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    Simulating the Change of Terrestrial Carbon Storage in China Based on the FLUS-InVEST Model
    Liu Xiaojuan,Li Xia,Liang Xun,Shi Hong and Ou Jinpei
    2019, 39 (3):  397-409.  doi: 10.13284/j.cnki.rddl.003138
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    The dynamics of terrestrial carbon are a key factor driving climate change and are greatly influenced by terrestrial processes. Land-use changes as a specific terrestrial process extensively influence terrestrial carbon storage through the alteration of biomass and soil organic matters. However, the direct effect of future land-use changes on terrestrial carbon storage is limited by the refinement of future land-use simulation. In this paper, we propose a FLUS-InVEST (future land use simulation-Integrate valuation of ecosystem services and trade-offs) model to assess the impact of projected land-use change on terrestrial carbon storage in China. The FLUS-InVEST model is composed of fine land-use projection and terrestrial carbon change detecting. Based on the representative showed that: 1) the area with deceased carbon storage shifts from North China to Northeast and the area with increased concentration pathways (RCPs) scenarios, we projected a future land-use change with 30 m resolution for 2100 in China and simulated the changing in terrestrial carbon storage. The FLUS results had a Kappa value of 0.74 and an overall accuracy with 0.80, which indicated that the FLUS performed well in fine land-use projection on a national scale. In addition, carbon storage shifted from Northwest to Southwest between 1995 and 2010. 2) In the RCPs scenario, carbon storage in the forests continues to increase, but decreased in grassland. Specifically, the carbon storage in ?he forest was predicted to increase by 2 332.64 Tg (1 Tg = 1012 g) and 1 754.59 Tg in RCP 6.0 and RCP 8.5, respectively. The carbon storage in grassland was predicted to decrease by 1 719.03 Tg and 2 468.80 Tg in RCP 6.0 and RCP 8.5, respectively. 3) In RCP 6.0, the carbon stored in aboveground vegetation and soil was projected to increase by 127.12 and 83.67 Tg. Conversely, the carbon stored in RCP 8.5 was projected to decrease by 24.67 Tg and 32.41 Tg in aboveground vegetation and soil, respectively, which indicated that RCP 6.0 contributes more to the future carbon sink than RCP 8.5. 4) In the RCPs scenario, the area with increased carbon was mainly located in lines of Hengduan-Qinling-Taihang-Great Khingan and Xufeng-Taihang-Great Khingant, and the area with decreased carbon was distributed throughout the Yunnan-Guizhou Plateau, Sichuan Basin, and Beijing-Tianjing-Hebei Region.

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    Coupling Coordination Degree Analysis between Multifunctionality and Security of Cultivated Land at Town Scale in Zhuhai
    Li Jiayi and Dong Yuxiang
    2019, 39 (3):  410-419.  doi: 10.13284/j.cnki.rddl.003130
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    Cultivated land can be regarded as a coupled system defined by human-nature interaction. The multifunctionality and security of it are therefore critical to the sustainable development of both the cultivated land and the human society. Furthermore, studying the coupled and coordinated development between the multifunctionality and security of the cultivated land is also the key to enhance its utilization and protection. For the town of Zhuhai, in particular, it is important to carry out such a study in a period of rapid urbanization. Therefore, taking Zhuhai as the study area, and utilizing land use data and socio-economic statistical data covering the period 1990-2015, this work investigates the temporal and spatial variation of the coupling coordination degree between multifunctionality and security of cultivated land by means of the comprehensive index evaluation method and the coupling coordination degree model. Besides, by using a new statistical method, the Geodetector, this article work also reveals the main factors controlling the development of the coupling coordination degree. Conclusions are drawn as follows: 1) the temporal variation of the coupling coordination degree between multifunctionality and security of cultivated land at town scale in Zhuhai is relatively steady in the period 1990-2000 but drastic in the period 2000-2015; in general, it decreases from 0.65 to 0.59 from 1990 to 2015; 2) the spatial variation of the coupling coordination degree exhibits an increasing trend in the western area, and a decreasing trend in the eastern area from 1990 to 2015; on the whole, its spatial distribution pattern shows that the western area is higher than the central and eastern areas; 3) according to the Geodetector, different factors have a different impact on the development of the coupling coordination degree: land reclamation rate, planting industry's proportion in GDP, output of crops, amount of chemical fertilizers and pesticides are the main factors affecting the development of coupling coordination degree, since they affect the cultivated land resource endowment, the utilization efficiency, the planting structure, and the input of chemical substances.

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    Young Chinese People’s Motivation to Participate in International Volunteer Tourism and Its Influencing Factors
    Tian Ziling, Bai Kai and Liu Chen
    2019, 39 (3):  420-429.  doi: 10.13284/j.cnki.rddl.003139
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    This study explores the motivation of young Chinese people to take part in international volunteer tourism, drawing on the records of empirical research conducted on Chinese university students. In the past 10 years, young people have shown an increased interest in volunteer tourism. Many of them have participated in volunteer tourism. On the basis of 26 semi-structured interviews, we conduct a qualitative analysis of the factors that motivate them to participate in volunteer tourism, how these factors were generated in the social and cultural contexts within China, and the kind of responsibility mechanism that has been formed through their behavior. Developing on the existing academic works on motivations that drive volunteer tourism, this study divides motivation into two types: altruistic and self-centered motivation. With altruistic motivation, volunteer tourists have the desire to provide aid in tourist destinations; self-centered motivation refers to personal benefits gained from volunteer activities, which include self-actualization (experiencing diversity, participating in special projects, and interacting with local people), personal interests (traveling to niche destinations, travelling abroad conveniently and making new friends), self-development (cultivating work experience and skills, gaining volunteer experience and certificates). These motivations are influenced by the following factors: the geographical imaginations shared by volunteer tourism providers, tourist images of the destination, the content of volunteer programs, and personal capabilities. We find that that self-centered motivation is the primary motivation for young Chinese international volunteer tourists. Altruism, which is deemed to be one of the most important motivations by Western-oriented studies, was seldom mentioned by the respondents. Compared with strong willing to conduct true destination aid, their care about destination communities and the natural environment is more influenced by commercial expectations. Hedonic experience, a concept frequently mentioned in Western studies, is only one of the factors that constitute personal interest. The other factors that motivate these volunteer tourists are cultural contact, convenient travel, and personal development, the last two factors being more important for them. Based on their personal interests, young Chinese volunteer tourists manage to fulfill their responsibilities towards the destinations. They also manage to fulfill their personal goals by connecting responsibility to destination with their choice of destinations and volunteer projects, and thus even though it can be seen as an egoistic activity, volunteer tourism can benefit the local environment and communities. Due to the dual nature of volunteer tourism: the combination of volunteer service and tourism activities—young Chinese people’s motivations for this type of tourism are varied. They are in fact influenced by both altruistic motivations and self-interest. Moreover, similar to previous studies, we argue that volunteer tourism involves the tourist’s responsibility towards both the destination and themselves. This research contributes to the internationalized understanding of volunteer tourism motivations through an empirical case study in the Chinese context, and the paper serves as an academic report on the commercial platforms for volunteer tourism in China.

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    Construction of Tourist’ Emotional Experience in the On-site Stage: Theoretical Model and Empirical Investigation
    Sun Xiaolong, Gao Jie, Lin Bishu and Li Lei
    2019, 39 (3):  430-439.  doi: 10.13284/j.cnki.rddl.003134
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    The on-site stage is important for tourists’ emotional experience; “integrity” of the tourism experience depends on the congruence and efficient operation of experiential elements. Currently, there is an incomplete understanding of the “essence” of tourists’ experience, and a research gap in understanding the implicit characteristics of tourists’ experiences remains. Based on the theory of social constructivism, this study analyzes the theoretical framework of tourists’ emotional experience construction in the on-site stage and proposes two direct factors that influence emotional experience construction. The theoretical framework is tested, and the interaction between various construction elements is analyzed by Structural Equation Modeling (SEM). Research reveals that the physical and social situations are two conceptual elements that comprise both tourists' actual and theoretical emotional experience in the on-site stage. Short-term contact between the individual and the destination leads to the realization of the tourism experience, and its essence is the emotional interaction between the human and the physical situation. The emotional interaction between tourists and local residents, traveling peers, and even scenic service staff can directly affect the degree of emotional experience. Sense of place and relationship commitment are direct factors that construct tourists' emotional experience in the on-site stage. Place identity and dependence positively influence tourists’ emotional experience from both emotional and functional perspectives. Tourists' emotional experiences in the on-site stage are primarily borne from place dependence-that is, the individual's bodily experience at the destination is the first point of the tourist experience. Place identity affects emotional experience through the “human-human social relationship” approach. This paper develops the scale of relationship commitment in the context of tourism experience. Relationship commitment refers to the emotional engagement that tourists actively experience with others that yields a positive experience. As a latent construct of the second-order structure, relationship commitment is composed of the emotional connection between the tourists with peers and local residents. In addition to directly influencing the emotional experience, relationship commitment also mediates the influence of sense of place on emotional experience. Compared with emotional connections with local residents, the emotional connection between tourists and their peers can influence the tourists’ perception of relationship commitment more strongly, which in turn affects the construction of emotional experience. Therefore, the emotional interaction between tourists and their peers is the core of the emotional experience construction. Finally, the article suggests several avenues for improving tourists’ emotional experience in national cultural scenic destinations: strengthening the display of the national cultural characteristics of tourism destinations, strengthening the influence of tourists’ bodily experiences on the meaning of tourism destinations, enhancing the community residents’ affinity for tourism, and establishing a good social interaction environment.

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    Effect of High-speed Rail on Producer Services’ Agglomeration in Chinese Urban Agglomerations
    Cao Xiaoshu, Hong Haolin and Liang Feiwen
    2019, 39 (3):  440-449.  doi: 10.13284/j.cnki.rddl.003133
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    Taking 16 Chinese urban agglomerations as research cases, this paper studied the effect of high-speed rail on producer services’ agglomeration in urban agglomerations, and its spatial variation based on the data of producer services’ employees of prefecture-level cities, railway origin-destination travel time, and train data for 2007 and 2017. The research was carried out in two steps, from static and dynamic points of view. The first was a static analysis of the spatial relationship between producer services’ agglomeration patterns and the high-speed rail network. The second analysis used the multiple linear regression model, taking the dynamic increment of producer services’ agglomeration level during 2007-2017 as a dependent variable. The conclusion consists of three viewpoints. First, high-speed rail positively contributes to the progress of producer services’ agglomeration, although this effect is concentrated mainly in eastern urban agglomerations, especially the Pearl River Delta Urban Agglomeration, the Yangtze River Delta Urban Agglomeration, and the Beijing-Tianjin-Hebei Urban Agglomeration. Within urban agglomerations, cities with a higher producer services’ agglomeration level in 2007 have benefited more from high-speed rail operations. Second, the effect of high-speed rail is restricted by the stage of economic development and the spatial structure of urban agglomerations. Relative diffusion of producer services from core cities to peripheral cities with sufficient support conditions along high-speed railways is more likely among eastern urban agglomerations because of their polycentric spatial structure. Third, besides the time-space compression effect, the organization of passenger transportation represented by the number of trains per day also significantly influences the agglomeration level of producer services. Population agglomeration, market demand increment, information level promotion, and positive government involvement are indirect approaches of the effect.

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    The Coupling Relationship between Multi-dimensional Urbanization and the Service Industry: A Case Study of Guangzhou
    Wang Shaojian, Liu Zhitao, Zhang Tingting, Wei Jiayi and Huang Fuzhong
    2019, 39 (3):  450-460.  doi: 10.13284/j.cnki.rddl.003129
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    With the advancement in the modernization level of cities, the development of the service industry has been playing an increasingly important role in promoting urbanization. Therefore, the coordination of the concurrent development of urbanization and the service industry has become an important issue in promoting the healthy development of cities. Using the coupling model of physics to calculate the coupling coordination between the service industry and comprehensive urbanization and its subsystems in Guangzhou, we thoroughly explored the characteristics and state of internal coupling coordination at different levels and the internal mechanism of the coordinated development between the service industry and urbanization. The study found that, since the beginning of the 21st century, the development level of the service industry and comprehensive urbanization in Guangzhou has increased significantly and continuously from 2000 to 2017. The coupling degree between the two has exceeded 0.9000 since 2002 and has reached the coupling stage. The overall coordinated development of the two is sound, and the degree of coupling coordination has increased from 0.171 0 to 0.974 1, reaching the stage of polar coupling coordination. The results show that the coupling coordination degree between four types of urbanization subsystems and the service industry has reached the stage of polar coupling coordination, from the stage of low coupling coordination. The coupling coordination degree of the population urbanization and economic urbanization subsystems and the service industry is rising continuously, with a high increase rate, while the coupling coordination degree of the social urbanization and, especially, spatial urbanization subsystems and the service industry is on the rise, with relatively high volatility and a low increase rate. From the perspective of stage change, the coordination and coupling stage of the service industry and population urbanization has changed fast, having reached the stage of polar coupling coordination by 2013, while the coordination and coupling stage of the service industry and economic urbanization has changed at the slowest speed. The results of the coordinated influence of four subsystems of urbanization show that good coupling of population urbanization, social urbanization, and spatial urbanization with the service industry plays a driving role in the coordinated development of comprehensive urbanization and the service industry, while economic urbanization plays a blocking role. Therefore, maintaining the advantage of pulling and solving the disadvantage of blocking will help to accelerate the development of Guangzhou. By comparing the research results of different spatial scales, we found that when regional development reaches a certain level, it becomes an irresistible trend that the development of the service industry and the urbanization process keep moving towards the best coordination state. We also found that when compared with other cities’ coupling coordination degrees of urbanization and the service industry, Guangzhou’s coupling coordination degree is above the national average. Combined with the national conditions and the development situation of Guangzhou, social development can have an impact on the degree of coupling and coordination between urbanization and the service industry.

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    Impact of Urbanization on Urban Air Quality Based on Spatial Econometric Models
    Jiang Lei, Zhou Haifeng and Bai Ling
    2019, 39 (3):  461-471.  doi: 10.13284/j.cnki.rddl.003142
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    China has been experiencing rapid urbanization and has also suffered from a serious air pollution problem. Hence, the main aim of this research was to investigate how urbanization affects air pollution in China based on a unique cross-sectional dataset of 289 cities in China for the year 2016. Specifically, we used the Air Quality Index (AQI), an accurate, well-recognized, and comprehensive indicator, to describe urban air pollution and employed nighttime light data to denote urbanization levels. Then, we considered spatial spillover effects and applied spatial lag models to test the impact of urbanization on air pollution. The findings of the study are as follows. From the results of spatial autocorrelation tests for the air pollution of the 289 cities by means of four spatial weights matrices, we observed that the air pollution of the cities exhibited strong spatial clustering. Additionally, according to the results of the spatial lag models, we found that the spatial autoregressive coefficient was statistically significant and positive, indicating that spatial spillover effects were present. In other words, local air quality is affected by the air pollution of neighboring cities. In addition, the variable of urbanization was also found to be significant and positive, implying that urbanization has a positive impact on air pollution. A possible interpretation is that the increase in the level of the urban economy at the early stage of rapid urban sprawl increases built-up areas and subsequently degrades the air quality of the city. The variable of regulation was found to be significant and positive. This was the case because close relationships between governments and enterprises hinder air pollution prevention and control because of lower and laxer environmental regulations to increase the competitive advantages of local firms and contribute to the local economy. However, the environmental awareness variable was found to have a negative impact on the AQI. It is projected that air pollution will be reduced greatly as income levels and environmental awareness continue to increase. Regarding the variable of PM2.5, the primary air pollutant, an increase in PM2.5 concentrations drives up the AQI because the estimated coefficient is significantly positive. Lastly, we observed that the variable of highway freight traffic was highly insignificant. One possible reason for this result is that we lack a satisfactory indicator for this variable. From the above analysis, policy implications based on the findings of the research may be threefold. One is that the trade-off between urbanization development and air quality cannot be overstated because the severe problem of urban air pollution poses a huge threat to the sustainability of China’s cities. The second is that making joint efforts and implementing efficient regional policies by local governments to prevent and control urban air pollution should be the first priority in an attempt to realize long-term and sustainable urban development. The last one is that innovation capacities should be increased and encouraged by local governments through a series of policies, e.g., tax relief, because improvements in the technological levels of cities will promote efficiency of cities and reduce air pollutant emissions, which may help to improve air quality and the environment.

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    Research Progress on Innovation Networks and Regional Growth from the Perspective of Economic Geography
    Cao Xianzhong and Zeng Gang
    2019, 39 (3):  472-478.  doi: 10.13284/j.cnki.rddl.003135
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    “Innovation-driven and transformative development” is a national development strategy that has been implemented by the central government of China. Scientific and technological innovation is gradually surpassing the driving effects of investment and an export-oriented economy on regional economic growth, thus becoming the new catalyst for economic growth. The relationship between innovation and regional growth has become an important area of study for economic geographers. As the innovation modality has transformed from single-actor independent innovation to multi-actor cooperative innovation, research on regional growth based on the perspective of innovation networks is a new focal point for economic geographers. This study reviews recent research literature on the measurement of innovation networks, the relationship between innovation networks and regional growth, and innovation networks’ effects on regional growth. It was found that social capital may be used to represent informal linkages in innovation network; however, it is not clear whether social capital can promote regional growth. The unquantifiable characteristics of social capital restrict further research. As a computable relational investment, network capital can be used to represent formal linkages in innovation networks and function as an explanatory mechanism for understanding the economic value of firm innovation networks. Innovation networks have a positive role in promoting regional growth, but we cannot ignore the phenomenon of regional innovation networks “local embeddedness” and “over-embeddedness” that leads to regional development “path-locking.” An academic consensus has been reached: regional growth is characterized by networking. Extant research has explained the impact of innovation networks on regional growth from different perspectives; knowledge flow and multi-dimensional proximity are widely used to explain the regional growth mechanisms. Spatial proximity knowledge networks are also considered to be integral to increase regional competitiveness, knowledge flow, and proximity by better explaining the relationship between innovation networks and regional growth. However, the substitutive and complementary effects resulting from the proximity of innovation networks actors and the influence of code and tacit knowledge flow on innovation and development must be further investigated. Regional growth is a topic that economic geographers have consistently emphasized; however, explaining regional growth from the perspective of innovation networks differs from other approaches that utilize the perspective of capital, investment, human capital, and related factors. Thus, this approach has important theoretical significance. This study aimed to analyze the mechanism by which network capital affects regional growth by focusing on three basic characteristics: coordination, complementarity, and homogeneity of regional internal and external innovation knowledge. Exploring the influence of entrepreneurship, psychological and behavioral characteristics of innovation actors on innovation networks and regional growth. This study concludes with suggestions for further research, such as empirical research on different types of innovation networks and regional growth, testing and reflecting on the relationship model between the two, and summarizing the general rules of innovation networks effects on regional growth.

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