The great opportunity of the development of rural tourism appears for new urbanization. Meanwhile, new demands and challenges are emerging. It is the rapid development of rural tourism and the scientific guidance of urbanization of rural areas that generate the significant and practical demand as well as the important and scientific proposition of new urbanization and the development of rural economy and society of China. By reviewing and rethinking rural tourism under the background of new urbanization, the realistic predicament of rural tourism is revealed such as environmental degradation, damage of rural culture, homogeneous competition of tourism, the low level quality overall, inadequate industrial training, shortage of fund and talent, lagging operation model, dislocation of land use, etc., at the same time, the in-depth study is required to solve many theoretic problems of complexity under the new situation. The paper proposes some suggestions, for example, the response to the demand of the major national strategy and the development of rural tourism in the new period should focus on some scientific problems including the features of rural tourism under the background of new urbanization, the influence and interaction mechanism of new urbanization on rural tourism, tourism led development mode of new urbanization, the recovery and reconstruction of rural tourism culture and nostalgic memory, the development of integration between rural ecological civilization and rural tourism, the spatial optimization of rural tourism as well as the spatial pattern and mechanism of the integration of urban and rural tourism, the product development of rural tourism and industrial integration and innovation, the solution to community participation in 'three rural issues' of rural tourism, the operation and management of rural tourism and the innovation of policies and institutions, etc. By deepening the theoretic research and strengthening the practical application, on the one hand, the upgrade of quality and efficiency of rural tourism can be improved, on the other hand, some qualified villages can be directed to the tourism-oriented road of new urbanization with Chinese characteristics. Finally, the complementary and coordinated development between urban and rural tourism can be achieved.
Traditional rural urbanization led by industry brings about many problems such as farmland reduction, environment pollution and hollow village. Can tourism avoid the disadvantages of former urbanization and become a path of new form urbanization? Firstly, this paper describes the process of tourism development in different stages in Licun village, and points out that Licun village have achieved the transition of occupational structure, pattern of production and living, ideology. Next, through theoretic explanation, it proves under the driving force of resource and leisure demand, tourism can take the lead in rural urbanization through the effective mechanism of host-guest interaction, demand-supply relationship and demonstration effect. And this kind of urbanization is a "green" path of urbanization which can avoid the disadvantages in traditional urbanization. At the same time, this paper summarizes problems such as infrastructure stortage, construction disorder and discordant landscape in current stage, and points out that the former "tolerant" policy from government indeed plays a positive role in the realization of rural urbanization. However, without powerful involvement and effective management of the government, this from-bottom-to-top form of rural urbanization is difficult to avoid "tragedy of commons".
Recently emerging beautiful villages in suburbs provide citizens very places for recreation, and can be considered as a new kind of urban residents' consumption space. From the perspective of actor-network theory, this study analyses the social-spatial reconstruction of Dashiao village. Through the tracing of translation, including four stages of problematization, interessement, enrollment and mobilization, the process and mechanism of the reconstruction of Dashiao beautiful village and the later consumption space was explored. It was manifested in the following four aspects: 1) In the process of the transformation from an usual village to a beautiful village, there was a heterogeneous actor-network, in which Jiangning District government played a focal role mainly by improving the physical environment of the village. 2) Heterogeneous actors changed their roles through urban residents' consumption activities. Along with the quit of incentives launched by government to rural residents, market mechanisms involved, district government and market forces of foreign business and consumers allied to become alternative focal actors, while villagers withdrew to the periphery of the actor network, which contributed to the re-establishment of actor network and the beautiful village's transformation to urban residents' consumption space. In order to meet consumers' demand, everyday lives of villagers' was represented partially to show the imaged rural life, but the real lives of villages was marginalized or hidden. Non-native culture and life style was transplanted or symbolically adopted, while the original village was fading away. 3) This paper explains the mechanism of social-spatial reconstruction of Dashiao village through the two sequential actor networks and how it transformed from the first to second. The transformation of intended target, which should be decided by focal actor of the actor network, the local government, from improving the physical environment to promotion of economic development determined the direction of the reconstruction of social space, as well as outside investment managers, and consumers attended and became key actors. Changes of structure and channel of interests in the actor network lead to the exit, redefinition and entering of actors. The reconstruction of social space is an ongoing process since the actor network is a dynamic connection, fulfilling of interests conflicts and negotiation. 4) From the actor-network perspective, beautiful village was not only a place for villagers' living and the tourists' poetic nostalgia, but also a networked space which is weaved of complex and dynamic relations of power. This paper points out the effectiveness and the time limitation of government and policy mechanisms, and the flexibility of the market mechanism, which brings about interest conflicts and social injustice. In the case of Dashiao, local residents withdrew from the masters of the village to marginalized role of urban residents' consumption space, and they have never played key actors during the establishment of the above two actor-networks.
Urban agglomeration plays a key role for China in attending the global divisions of labor, international competitions, as well as the integration of regional economy. Various scholars have dedicated to the study of urban agglomeration. However there is no consensus on the definition of urban agglomeration, which leads to the controversy. Relations between each city-pair in an urban agglomeration may form a complex network which brings a great challenge for researchers to use traditional method to synthetically analyze the spatial structure, due to the exponential calculation time increased by a great number of nodes. Based on the summary of different definitions, a novel method is developed to analyze the multi-level spatial structure of an urban agglomeration. We first find the core cities by calculating the urban centrality of each city in an urban agglomeration using several selected indices. To be specific, the spatial scope of the urban agglomeration can be defined as the 2-hour commute range of each core city. Then interaction intensities between each pair of cities are calculated based on the traffic accessibility and cities' scale. We develop an algorithm to analyze the spatial structure based on the so-called Multi-level Spatial Structure Tree (MSS-Tree), which can be used to analyze the urban agglomeration structure in detail. Finally, we carry out the sample study of Beijing-Tianjin-Hebei urban agglomeration to testify the model. The experimental results show that due to the centrality of Beijing downtown area, cities or towns around Beijing have much more interactions with Beijing than among themselves. It could be concluded that mature sub-center cities or towns around Beijing are needed to take the responsibility of service provision. In comparison, Tianjin downtown area and Tianjin coastal district have double cores in Tianjin. Hengshui city far away from Beijing downtown area has the potential to become a secondary central city in the near future. The case study also demonstrates that the algorithm based on the MSS-Tree data is an effective method for the spatial analysis of an urban agglomeration, and can play an important role in subsequent decision makings of urban agglomeration development.
Based on investigating and interpreting the characteristics of the size structure of regional urban system, this paper firstly aims to build a model on analyzing the relationships between reverse urban cumulative size and number of cities. Secondly, based on the sixth national population census data of 2010, traditional rank-size rule and the model of reverse cumulative size proposed in this paper are used to measure the inter-provincial differences and their spatial distribution characteristics of urban size structure in China. Thirdly, the geographic factors which have influence on regional urban system are discussed. The results show that the rank-size rule has few shortcomings in interpreting the characteristics of the size structure of regional urban system, especially for the urban system in which there is the distribution of primary city, two-centre city, or small number of cities. The shortcoming leads to the fact that there is no necessary linkage between the value of Q derived from the rank-size rule and the selected geographic variables. As a result, there are certain limitations in the comparative study between different regional urban system structures. Overall, the fitting provided by the model of reverse cumulative size given in this paper is better than that provided by the rank-size rule. Particularly, when the fitting provided by the rank-size rule is not ideal, the model of reverse cumulative size can overcome this shortcoming, and provides accurate fitting to more realistically and objectively reflect the characteristics of the size and structure of regional urban system. Moreover, the results also show that there is a close statistical relationship between the selected regional variables, such as regional economy, urbanization, population density and the composite index, and the value of β given by the model of reverse cumulative size. In the process of urbanization, path of the urban system coordinated with regional development should be explored in term of the tendency of development and characteristics of different regions. According to the statistics derived from the general regression model and spatial auto regression model, there is a weak spatial linkage between the formation and evolution of the regional urban systems of each province in China. That is to say, the formation and evolution of the regional urban systems of each province is in a close state of isolated development. The reason should be related to the strict administration and policies of household registration and the prevalence of local protectionism in China.
This paper proposes the community travel low carbon index (CTLCI) model to demonstrate the spatial pattern and regional difference of CTLCI in Guangzhou. And then, it uses traditional ordinary least squares (OLS) model and geographically weighted regression (GWR) to examine the spatial heterogeneity of the relationship between CTLCI and influence factors. The results indicate that CTLCI is increasing from central city to the periphery in Guangzhou, being three-layer structure obviously. The internal difference of CTLCI is the least in the inner layer, and the biggest in the middle transition layer. From global statistical modeling, the community population density has positive effects on CTLCI, and public transport supply level and density of the road network have negative effects on CTLCI. The relationships between explanatory variables and CTLCI vary across the study area. The area where effects of the community population density on CTLCI are positive is mainly distributed in the outer layer and the middle transition layer. It is larger than that where effects are negative, which is mainly distributed in the inner layer. The community public transport supply level and the community density of the road network both have negative effects on CTLCI in most of the regional space. But the former covers more communities than the latter, because the effects of them have spatial difference. The paper points out the different influence of community population density, public transport supply level and density of the road network on CTLCI in different space specifically. This provides a scientific basis for reducing CO2 emissions from urban transport, constituting different policies to different districts and building urban spatial structure toward a low-carbon society.
For a long time, emphasis on the relationship between job and residence and its impact on commuting have been placed by the academia at home and abroad. In China, because of the excessive population concentration, the construction of large-scale residential districts in suburban areas has become the significant method for the metropolis and megalopolis to relieve the population stress of their central city. Hence, the parties related, including city government, academia and residents themselves, focus on the commuting feature of large-scale residential districts. Taking a case study of the Gucun community, Baoshan District, Shanghai, this paper analyzes the residents' worksite and commuting willingness, using methods of questionnaire, comparative analysis and regression model, etc. Based on the residents' general commuting feature, this paper compares 4 classes of population groups at Gucun, including residents in commercial housing, transferred residents from downtown, transferred residents from local village and residents in rental housing. The results show that: from the job-housing relationship, the majority of residents are apt to work nearby, and most of them have relatively high level of commuting satisfaction in general. However, huge differences in the commuting exist between different population groups. The results of regression model of commuting distance and logistic regression model of commuting satisfaction show that the residents' commuting distances are relative to their personal factors, such as income, education, Hukou, family scale, and their commuting satisfaction degrees are mainly affected by commuting distance and commuting willingness, except for the income.
Since China's reform and opening up in 1978, the scale of inter-provincial migration increased sharply, especially from 2000 to 2010. The redistribution of inter-provincial migration has had significant influences on China's urbanization and socio-economic development. Using data from China's 2000 and 2010 censuses, this paper investigates inter-provincial migration by describing its spatial patterns and estimating its impacts on urbanization development with various indictors, such as geographic concentration index, gravity center of migration, composite index of migration, network analysis, and coefficient of variation. The results are as follows: 1) There have been escalating dispersion trends for the distribution of in- and out-migration, especially the out-migration. At the same time, the gravity center of in- and out-migration both move towards north and east. Besides, the destinations of migration has shifted from one single polar (Guangdong) in 2000 to multi-polar (Guangdong, Zhejiang, Shanghai, Jiangsu, Beijing, Fujian) in 2010; while Anhui, Sichuan, Henan and Hunan become the new top four sources of migration in 2010. 2) With the rapid growth of floating population, the network trend of inter-provincial migration is more prominent. Overall, the migration network of 2010 becomes more compacted, connective and balanced than that of 2000. At the regional scale, the migration of population is mainly from central and western to eastern China. The eastern region become the main destinations, while the central and western regions of China have become the main sources of inter-provincial migration, especially the "mid-belt subsiding" is more prominent. At the provincial scale, the increased migration flows mainly to Shanghai, Zhejiang, Jiangsu, Beijing, Tianjin, Fujian, etc. Besides, the migration flows formulate different models due to the effects of regional development disparities, migration distance and migration stocks. 3) The regional types of inter-provincial migration could be divided into four kinds: active regions have a larger floating population and their in-migration is much more than out-migration, which is mainly located in the eastern coastal provinces and Xinjiang; active regions have a larger floating population and their out-migration is much more than in-migration, which is mainly located in the central and western China; active regions have a larger floating population and their in-migration is nearly equal to out-migration; inactive regions have a smaller floating population, such as some provinces with a large ethnic minorities population. 4) Inter-provincial migration has a positive effect on the development of urbanization. It contributes to 18.13% of the increment of urbanization rate and it also narrows the disparities of urbanization rate among provinces, during 2000-2010. However, migrant workers account for most of the inter-provincial migration, and make great contributions to the development of urban socio-economy, but they cannot share the same identity with the citizens due to the household registration system. Therefore, it is necessary to accelerate the reform of household registration system and promote the citizenization of migrant workers.
The urban green belt is critical to combat the urban sprawl and improve the ecological security pattern. The recreation development of the green belt can not only increase recreational space of a metropolis, but also enrich the utilities of greening. In this paper, we take 6 types of recreational spaces in the second greenbelt, Beijing, China as a case study. Based on the spatial analysis, such as kernel density estimation, we examine the overall spatial pattern, scale, capacity features of the greenbelt's recreational spaces in Beijing, as well as the spatial features and causes of various types of recreational spaces in the greenbelt. Several main conclusions can be drawn as follows: ① In respect of the overall spatial pattern, the greenbelt has presented a number of recreational assembling zones. The green belt's recreational space is characterized by "dense north, sparse south". There are a great number of recreational agglomerations in the north. On the contrary, the recreational space is sparse in the south. ② As far as the scale and capacity are concerned, the structure feature of the recreational space in the greenbelt is characterized by "large agglomeration, small scatter". There are 6 large scale recreational agglomerations with high density. ③ The causes for spatial characteristics of 6 types of recreational spaces have been identified: The cluster of resources and environment is the main reason for the attractions in the recreational spaces of greenbelts. Comparatively, suburban leisure parks are evenly distributed due to the related urban plans. The important river systems have formed an excellent landscape and an ecological buffer barrier for the sport recreational space, which shows a highly spatial correlation with the important river systems. The theme-park recreational spaces place emphasis on the visiting groups' cultivation, thus they are close to the trunk roads. The conference and resort spaces are highly connected to the distribution of the geothermal resources in Beijing. The folk-custom-experience recreational spaces are mostly distributed around the Shangzhuang Reservoir in Shangzhuang Town, Haidian District. On the one hand, the local governments encourage the recreational development; On the other hand, the good natural reservoir environment attracts a large number of local visitors, and has a high revisit ratio due to the public praise. Finally, in terms of the features and causes of the greenbelt recreational space in Beijing, we can see that there are rules to follow as to the suburban greenbelt recreational space of a metropolis. To provide a reference for the development and management of greenbelt recreation of China, the governments at all levels should pay close attention to the construction of greenbelt recreation system, the adjustment of the existing layout structure of greenbelt recreational spaces, as well as the further development of various recreational spaces.
Vegetation productivity is closely associated with the productive and daily activities of human beings. Vegetation provides them with food, raw materials and fuels, and also has such functions as wind prevention and sand fixation and air purification. Moreover, they are key factors in the regulation of carbon source and carbon sequestration of the ecosystem. The absorption of carbon dioxide and release of oxygen by the green plants through photosynthesis helps to strike a balance of CO2 and O2 in the atmosphere. In particular, with developments in socioeconomic sectors, a sharp rise in the CO2 concentration in the atmosphere as well as abnormal conditions in the global climate, vegetation's ability to fix carbon and release oxygen and the value thereof appear to be of particular importance. Based on the remote sensing data and measured data at meteorological stations from 1980 to 2010, we have evaluated the net primary productivity of the vegetation in Northern Shaanxi using the CASA model (a refined version from the light energy utilization model), calculated the value of carbon fixation and oxygen release of the vegetation and analyzed the characteristics of its changes. The findings suggest the following: (1) There is a major difference in different land-use patterns. In a descending order, the NNP averages are respectively forest land, grass land, arable land, construction land and unused land. From 1980 to 2010, the variation in the total value of NPP has been featured by the trend of "increase-decrease-increase", with the amount of NPP rising by 35.60% over the past 30 years; (2) In a descending order, the amount of carbon fixation and oxygen release for different land-use patterns are successively grass land, forest land, arable land, unused land and construction land; and (3) In 1980, 1990, 2000 and 2010, the total value of carbon fixation and oxygen release are respectively 267.208×108 yuan, 276.725×108 yuan, 260.796×108 yuan and 362.318×108 yuan. During the period of 1980-2010, the total value of carbon fixation and oxygen release have been increased by 95.110×108 yuan. In terms of spatial distribution, Fugu and Shenmu counties in the southern and northern parts of Northern Shaanxi have seen marked fluctuations in the total value of carbon fixation and oxygen release, while the northwestern part of Northern Shaanxi has seen mild interannual variation in the total value of carbon fixation and oxygen release; in terms of land-use patterns, the standard variation has shown a trend of "forest land, grass land, arable land, unused land and construction land" in a descending order. (4) Over the past 30 years, the total value of carbon fixation and oxygen release has shown a general trend of continuous increase. In terms of land-use patterns, the average rate of change in the total value of carbon fixation and oxygen release has respectively been unused land, construction land, arable land and grass land in a descending order. (5) On the whole, the value of carbon fixation and oxygen release in an ecosystem is positively correlated with the precipitation and negatively correlated with the monthly average temperature. Changes in the value of carbon fixation and oxygen release typically respond intensely to those in precipitation. The temperature has a great impact on the value of carbon fixation and oxygen release by coupling with other climatic systems. The difference in land coverage has been a major factor contributing to the marked difference between the northern and southern parts of Northern Shaanxi in the value of carbon fixation and oxygen release in terms of spacial distribution. As the southern part is located in the semi-humid region with a high ratio of vegetation cover and is dominated by broadleaved deciduous forest, the amount of CO2 fixation and O2 release is relatively large. It should be noted that the general trend of rise in the value of carbon fixation and oxygen release in Northern Shaanxi during the period of 1980-2010 is, to a great extent, related to the advancement of the beginning period of the growing season, an extended growing season of the vegetation and to global warming. In such a case, the accelerated moisture vaporization on the earth's surface and aggravated drought stress will lead to an increase in the intensity of carbon sequestration by the vegetation.
In order to study the intensity and frequency characteristics of extreme runoff over the Huaihe River Basin, this paper used 21 distribution functions to fit the AM (Annual Maximum) and POT (Peak Over Threshold) extreme runoff series at 13 hydrological stations which were located in the coverage area of trunk and tributary of the middle and upper Huaihe River Basin. In addition, M-K test was used to study the variation trend of intensity and frequency of extreme runoff. The results are as follows: (1) Intensity of extreme runoff at 6 stations has a positive trend while that at the other 7 stations has a negative trend; temporal frequency of extreme runoff at 8 stations has a positive trend while that at the other 5 stations has a negative trend. (2) In AM series, the frequency distribution of runoff value obeys the Weibull function rather than the widely used GEV function on the whole, while in POT series, the frequency distribution of runoff value still obeys the GP function on the whole. (3) Compared with other 12 stations, the frequency distribution of extreme runoff value of Bantai station is the most intensive with a peak frequency of 0.27, and the frequency distribution of extreme runoff value of Wujiadu station is the most homogeneous with a peak frequency of 0.0475. (4) The extreme runoff value is high in the middle basin and Mengwa region in the study area. (5) The error rate of extreme runoff estimated based on GP function is the lowest, whose error rates of most regions is lower than 0.2. In particular, the estimation accuracy of GP function is higher than that of Pearson III function, so that the engineering standard in the upper reaches of the basin may need to be adjusted. Moreover, affected by the function form, the estimation accuracy of best-fit function is lower than that of the GP and GEV functions.
Drought, one of the most complex natural hazards, affects agriculture, water resources, natural ecosystems, and society. The negative societal consequences of drought include severe economic losses, famine, epidemics, and land degradation. However, there are few studies on the complexity of drought characteristics, both at multiple time scales and with variations in evapotranspiration. In this study, drought occurrences were quantified using a new drought index, the standardized precipitation evapotranspiration index (SPEI), based on observed meteorological data of monthly mean temperature and precipitation from 1961 to 2013 in Henan province, central China. This can help decision-makers improve their level of preparedness and adopt appropriate policies for agricultural management. Based on the SPEI values of each weather station in the study, the frequency and severity of meteorological droughts were computed, and the monthly, seasonal, and annual drought frequency and intensity over a 53-year period were analyzed. The spatial and temporal evolution, intensity, and the primary causes of drought occurrence in Henan were revealed. The results showed that the SPEI values effectively reflected the spatial and temporal pattern of drought occurrence. As the time scale decreased, the amplitude of the SPEI increased and droughts became more frequent. Since 1961, drought has occurred at the annual, seasonal, and monthly scales, and the occurrence of drought has increased. However, regional distribution has been uneven. The highest drought frequency, 35%, was observed in the Zhoukou region, while the lowest value, 26%, was measured in the central and western parts of Henan. The most severe seasonal droughts occurred in the spring and summer months, followed by autumn. Annually, wide-ranging droughts occurred in 1966-1968, 1998-2000, and 2011-2013. The drought intensity distribution showed higher values in northern and western Henan, and lower values in its east and south. The maximum drought intensity value was recorded in Anyang, and the minimum occurred in Zhumadian, at 22.18% and 16.60%, respectively. The factors with the greatest influence on drought occurrence are increasing temperatures, the Eurasian atmospheric circulation patterns, and the El Niño effect.
The sedimentary structure of dune systems provides available information about the development of dunes. Along the coast of Changli County, Hebei Province, China, a high large transverse coastal dune has been formed. This place is a typical coastal sand dune field in China, where the highest point of the dune reaches up to 40 m above sea level. The transverse dune runs NNE-SSW and the dominant wind direction is NE or NNE in the study area. In order to gain more detailed data of the sedimentary structure and to understand its formation better, we performed a study to detect the inner structure of the transverse dune using ground-penetrating radar (GPR) and to analyze the grain-size characteristics. GPR is a non-invasive technique that allows the study of the structure of dune systems when outcrops are limited. The images of sedimentary structure at a depth of 0-20 m obtained from the GPR reveal dip direction, dip angle and distribution of the bedding. There is a strong reflector at about 6 m depth inside the dune. Above the reflector, high-angle cross bedding is generally found; the dip direction of the bedding is SWW and the dip angle ranges from 30° to 32°. The high-angle cross bedding formed by onshore wind is a kind of foreset beds. We can also find some reactivation or erosion surfaces on the windward slope which are influenced by the secondary changes of wind. On the top of the transverse dune, trough cross-bedding caused by the seasonal variation of wind direction is developed. Below the surface, cross-lamination shaped by the wave action is found. The cross-lamination develops both in landward and seaward slopes, where it dips landwards and seawards respectively. The results of grain-size analysis indicate that the sediment is well-stored medium sand. But the grain size at the base of the dune is coarser than that at the top of the dune. The sediment at the base deposited under the action of wave, while the sediment at the top deposited under the action of wind. Therefore, based on the characteristics of sedimentary structure and grain size, we conclude that the strong reflector is the interface of an old beach barrier and aeolian dune. Integrating previous studies on the changes of the coastline since late Holocene in the study area, around 2000 years ago suggest that the beach barrier controlled by wave action exposed above sea water and the Qilihai Lagoon formed on the landward side. The transverse dune developed based on the beach barrier outside the Qilihai Lagoon since 2000 aBP and it was eroded by wave, at the beginning of the formation of the aeolian dune. The high large transverse dune is the result of steady accretion under the action of wind for a long time.
The "Semi-Karst", as a special part of karst ecological environment of Guizhou, is a typical ecological fragile zone. Clearly defining and fully understanding its concept and connotation, combined with analysis of characteristics of its landscape, is an important way to cognize this special landscape. In this paper, the concept of "Semi-Karst", as well as its landscape characteristics and ecological environmental effect, have been involved in a preliminary discussion. Analysis holds that "Semi-Karst" is a transitional landscape developing in impure carbonate rocks and the interlayer of carbonate rocks and non-carbonate rocks. It is another kind of karst landscape different from typical karst and non-karst in development of stratum and lithology, landscape characteristics and ecological environment effect. "Semi-Karst" is mainly constituted by impure carbonate rocks and interlayer of carbonate rocks and non-carbonate rocks. Carbonate rocks mainly include the argillaceous dolomite and argillaceous limestone, with middle Triassic Guanling Formation (T2g) as most typical. And non-carbonate rocks mainly include interbedded reservoir of Daye Formation (T1d), Ziyun Formation (T1z), and Luolou Formation (T1l). In "Semi-Karst" regions, rocks mostly contain high argillaceous composition; karst development is not as good as in typical karst regions; landforms mainly include hill and valley, low and middle hill, shallow cutting low and middle mountain; terrain fluctuation and surface cutting level are relatively small; slope is nearly between 8 and 35 degrees; peak cluster and peak forest are rare, which are common in typical karst regions. At the same time, few underground karst caves can be found, and karst caves are relatively small on height and length; modulus of groundwater resources is big, and drought and surface water shortage are not as serious as in typical karst areas. Due to rock in "Semi-Karst" of high content of argillaceous rock composition and insoluble residues and low rate of dissolution, these regions are featured by rich soil parent material, fast soil formation rate, thick soil layer, and medium pH of soil. "Semi-Karst" regions have a large amount of cultivated lands and high agricultural value, which can relieve the conflict between people and land to a certain extent. In addition, in "Semi-Karst" areas soil covers are continuously distributed, natural vegetation grows densely, Pinus massoniana and cypress are widely distributed, the ecological environment effect is good, and the ecosystem is relatively stable. However, due to factors such as human activities, the quantity of soil erosion in "Semi-Karst" area is larger than that in typical karst area under the same conditions. Therefore, more significance should be attached to "Semi-Karst" area and a lot of related researches are needed in the future.
Landscape structure of a large artificial forest planted area tends to be homogeneous by the intensive disturbance of human activities, and the landscape function has been greatly changed as well as landscape structure. Therefore, it is particularly important to introduce landscape function into landscape ecological security research, which can reflect the change characteristics of landscape ecological security systematically and objectively. Taking Ximeng county, a large artificial forest planted area as the study area, this paper established a landscape ecological security model by landscape structure safety index and landscape function safety index. The landscape structure safety index consists of landscape interference degree and landscape fragile degree, and landscape function safety index consists of ecosystem service value. Then spatiotemporal changes of landscape eco-security in Ximeng from 2000 to 2010 were analyzed by dividing the security degree into three levels from low to high:Ⅰ,Ⅱ,Ⅲ level. The results showed that: 1) The landscape ecological security model can effectively reflect the ecological safety of every landscape type, and the order of ecological safety degree of landscape type in 2010 is forest>rubber>waters>shrubbery>paddy field >grassland >dry land >construction land. 2) The plantation of large area of artificial forest in the past 10 years has caused the levels of landscape ecological security in Ximeng converted from Ⅲ to Ⅰand Ⅱ. The ecological security degree in the whole county decreased but still stayed at an intermediate level. 3) The landscape ecological security in Ximeng is significantly different in space, which presents an overall pattern of "high in northeast and southeast, and low in northwest and southwest". Landscape ecological security of Zhongke village is the best, while that of Mengsuo village is the worst.
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