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Abstract Low carbon intensive use of urban land is an important trend to achieve regional high quality development. In this study, with Kaifeng municipal district as an example, the catastrophe progression model was used to estimate and analyze the low-carbon intensive use level of urban land in Kaifeng City from 2011 to 2020, and the obstacle factors in the process of low-carbon intensive land use in Kaifeng City were revealed by using the obstacle degree model. The results showed that during the study period, the low-carbon intensive use of land in Kaifeng City showed a slow, fluctuating and declining trend, and the overall situation was in a generally intensive state. The land input level and land output level were on the rise, while the low-carbon level of land and the degree of land use were on the decline. Currently, the main obstacle factors restricting the low-carbon intensive use of land in Kaifeng City were the carbon structure coefficient of land use, energy consumption per square kilometer, carbon emissions per square kilometer, carbon emissions per capita, and non-agricultural land use efficiency. In the future, it is necessary to further improve the land use structure and promote the high-quality development of Kaifeng City.
Key words Low-carbon intensive use of urban land; Entropy value method; Catastrophe progression; Obstacle degree; Kaifeng City
Received: July 13, 2021 Accepted: September 15, 2021
Supported by Basic Scientific Research Business Expense Project of Scientific Research and Development of Henan Academy of Sciences (210601043).
Chenguang YUAN (1993-), male, P. R. China, master, devoted to research about land use and resource economy.
*Corresponding author.
As the scale of cities continues to expand, people’s demand for land continues to increase. Meanwhile, how to use urban land effectively with high quality has become a hot issue, and the low-carbon intensive use of land is closely related to people’s lives. Improving the efficiency of land use is conducive to promoting the high-quality development of urban land while combining national hotspot policies. At this stage, scholars have already made richer research results on land use. Scholars have made in-depth explorations on the influencing factors, evaluation systems, evaluation methods, and driving mechanisms of land intensive use from different spatial scales and research perspectives. For example, Wu and Qu［1］discussed the mechanisms affecting land use from the economic, institutional and ecological levels; Fan and Liu［2］explored land structure and land functions in depth; Zhu and Cao［3-4］constructed a PSR model to reveal the spatial differences in land use in Guangdong Province; Yin et al.［5］used RS and ANN evaluation methods to conduct in-depth discussions on the intensive use of urban land in Shijiazhuang City; and Fan and Liang et al.［6-7］analyzed the land use status and obstacle factors in the Beijing-Tianjin-Hebei region from the ecological and low-carbon perspective. Above studies mostly use subjective methods to determine the impact mechanism of land use, and seldom use standard deviations of indexes to determine the weight values in overall index systems and use models to determine obstacle factors. Therefore, in this study, the catastrophe progression and obstacle degree model were introduced to investigate low-carbon intensive use of urban land, so as to reveal the level of low-carbon intensive use of urban land and its obstacle factors in Kaifeng City from 2011 to 2020, and provide a reference for the high-quality development of Kaifeng City. Data Sources and Study Methods
Data source and processing
The data of this study were obtained from the 2011-2020 Kaifeng City Statistical Yearbook. Some statistics related to population, output value, etc. sourced from the website of Henan Provincial Bureau of Statistics (http:∥www.ha.stats.gov.cn). When calculating relevant data, data errors were eliminated by standardization, as shown in formula 1:
yij=xijmax (xij) (Positive effect index)
yij=1-xijmax (xij) (Negative effect index)(1)
In the formula: xij and yij respectively represent the original value and the dimensionless value of the jth index in the ith year, respectively.
Study methods
The entropy method
The entropy method is a method to determine the weight value according to the degree of dispersion among indexes. In this study, the entropy method was used to determine the specific degree of dispersion among the low-carbon intensive use indexes of land in Kaifeng City to determine the weight values. The formulas were giving below. In the following formulas, m is the number of statistical years, and n is the number of indexes.
(1) Calculation of the proportion Rij of the index value xij:
Rij=xij/∑mi=1xij(2)
(2) Calculation of the entropy of the jth index:
ej=-1lnm∑mi=1Rij×lnRij(3)
(3) Calculation of information entropy redundancy:
dj=1-ej(4)
(4) Calculation of the weight of the jth index:
Wj=dj/∑mi=1dj(5)
Catastrophe progression method
The catastrophe progression method is to perform multi-layer decomposition of a target, and its specific quantification using catastrophe theory and the principle of normalization, so as to comprehensively evaluate the target［15-20］. In this study, we carried out the evaluation of the low-carbon intensive use of urban land following the steps of constructing an evaluation index system, ranking indexes, establishing a multi-level hierarchical structure model, and using a normalization formula to calculate the value of the catastrophe membership function step by step.
Obstacle degree model
The diagnosis of obstacle factors was to analyze introduced factor contribution degree Uj, index deviation degree Vj, and obstacle degree Mj to determine main obstacle factors that affect the low-carbon intensive use of land and their degrees of influence. The specific calculation process was as below［15］:
Uj=wij(6) Vj=1-zj(7)
Mj=Uj×Vj∑nj(Uj×Vj)×100%(8)
Cj=∑Mj(9)
In the formula: wij is the weight of the jth index factor of the ith layer; zj is the standardized value of the jth index of the ith layer; and Mj and Cj are the obstacle degrees of the index-layer factor and the criterion-layer factor, respectively.
Evaluation index system for low-carbon intensive use of urban land
We believed that the core of low-carbon intensive use of land is to create higher benefits with lower emissions and consumption［8-11］to achieve high-quality development. According to the characteristics of the rationality, high efficiency, and conservation and intensiveness of land use, combined with related research［6,8,10-14］, such four indexes as land input level, land use degree, land output benefit, and land low-carbon level were selected as a criterion level, and 15 indexes were selected on this basis to construct an evaluation index system for the low-carbon intensive use of urban land in Kaifeng City, as shown in Table 1.
Case Analysis
Determination of the weights of evaluation indexes for the low-carbon intensive use of land in Kaifeng City
According to formulas (3)-(6), the specific weights of the evaluation indexes for the low-carbon intensive use of land in Kaifeng City were obtained, as shown in Table 2.
Evaluation level division
Generally, the evaluation values of the low-carbon intensive use of urban land calculated by the normalization formula are relatively high, and the differences between values are small, so the degree of distinction is not high, and it is difficult to evaluate the quality of the target. Therefore, it is necessary to design an evaluation standard suitable for the catastrophe progression method［16-18］. According to the catastrophe theory, the catastrophe level value was divided into five levels: highly intensive (0.8-1.0), relatively intensive (0.6-0.8), generally intensive (0.4-0.6), relatively extensive (0.2-0.4), extensive (0-0.2), as shown in Table 3.
Analysis of results
Evaluation results of the low-carbon intensive use of urban land in Kaifeng City
According to the index weights determined by the entropy method, the catastrophe progression model was used to calculate the low-carbon intensive use level of urban land in Kaifeng City from 2011 to 2020. The results are shown in Table 4.
Combining with Table 4, the land use change status of Kaifeng City was analyzed from two aspects: index level and comprehensive level. ① Index factor analysis: The land input level and land output level in the index layer from 2011 to 2020 showed an upward trend. The evaluation value of the land input level increased from 0.924 0 in 2011 to 0.934 2 in 2020, and the evaluation value of the land output level increased from 0.951 7 in 2011 to 0.999 3 in 2020, which is due to the continuous improvement of the core area for foreign trade development in Kaifeng City in recent years, the steady improvement of economic conditions, and the steady increase of government and enterprise investment in land along with the improvement of policies. From 2011 to 2020, the land use degree and land low-carbon level showed a significant downward trend. The land use degree dropped from 0.900 2 in 2011 to 0.722 4 in 2020, and the low-carbon level of land dropped from 0.887 6 in 2011 to 0.790 4 in 2020, which is because with the increase of land input, and idle land is also increasing, which makes the degree of land use continue to decrease, resulting in "negative external effects". Especially in daily life, affected by carbon sources and carbon sinks, low-carbon use of land is seriously threatened.
Chenguang YUAN et al. Evaluation and Obstacle Diagnosis of Low-carbon Intensive Land Use in Kaifeng City ② Comprehensive level analysis: From 2011 to 2020, the evaluation value of low-carbon intensive land use in Kaifeng City was in the range of 0.915 9-0.861 6, showing a slow declining trend. This trend was divided into three stages: from 2011 to 2013 (the first stage), the comprehensive value changed from 0.915 9 to 0.936 5, and reached its peak in 2013, which was due to the sharp decrease in energy consumption, especially coal consumption; from 2013 to 2018 (the second stage), the comprehensive value changed from 0.936 5 to 0.828 3, which was mainly due to the continuous increase of urban construction land, the continuous development of the Central Plains Economic Zone, and the rapid increase in energy demand for infrastructure construction and industrial development; and from 2018 to 2020 (the third stage), the comprehensive value changed from 0.828 3 to 0.861 6, which was mainly because in recent years, high-quality development policies have been continuously introduced, the use of various types of land has been continuously balanced, the structure of related industries has been continuously adjusted, and people’s awareness of low-carbon protection has continued to increase, which has promoted the improvement of land use level. Diagnosis results of obstacle factors for low-carbon intensive use of urban land in Kaifeng City
According to the evaluation results in "Evaluation results of the low-carbon intensive use of urban land in Kaifeng City", the obstacle degree of each index was calculated using the obstacle degree model in "Obstacle degree model", as shown in Table 5.
In order to directly reflect the obstacle factors affecting the low-carbon intensive use of land in Kaifeng City, taking the basic year and the final year as the time nodes, the main obstacle factors with obstacle degrees ranked in the top 5 were selected, and the obstacle degree was calculated according to the formulas in "Obstacle degree model". The details are shown in Table 6.
It can be seen from Table 6 that in the basic year of 2011, obstacle factors for the low-carbon intensive use evaluation of Kaifeng City’s land were concentrated in the green coverage of built-up areas, per capita road area, population density, GDP per square kilometer, and retail sales of social consumer goods per square kilometer; the obstacle factors in 2020 were concentrated in the coefficient of land use carbon structure, energy consumption per square kilometer, carbon emissions per square kilometer, carbon emissions per capita, and use efficiency of non-agricultural land. The analysis showed that the obstacle factors in the basic year were manifested in land use output and benefit, and the obstacle factors in the final year period were manifested in the low-carbon use of land, that is, as time progresses, low-carbon use of land has become the main basis for the high-quality development of urban land. According to the method under "Obstacle degree model", the obstacle degrees of the index layer were calculated as shown in Table 7.
It can be seen from Table 7 that the obstacle degree of low-carbon intensive use of land in Kaifeng City from 2011 to 2020 showed significant differences. In 2011, land output benefit became the main obstacle factor to land use; and in 2020, the low-carbon level of land became the main obstacle factor. Analyzing the overall trend, the obstacle degrees of land input and output were decreasing, and the obstacle degree of low-carbon land was increasing. It can be predicted that in the next few years, low-carbon use will become the focus of urban development. Therefore, balancing the demand for land, improving the land structure, and ensuring the orderly and stable development of the urban land market are the main means to promote the high-quality development of Kaifeng City. Conclusions
In this study, we attempted to use the catastrophe progression and obstacle degree model methods to characterize the change trend of the low-carbon intensive use level of urban land in a small-scale space. Combining the evaluation criteria, the entropy method was used to objectively assign weights, and the catastrophe progression and obstacle degree model methods were introduced to reveal the low-carbon intensive use of urban land in Kaifeng City from 2011 to 2020 and its obstacle factors. The main conclusions were given as below.
(1) The land input and land output levels in the index layer between 2011 and 2020 showed an upward trend, which is due to the continuous improvement of the core area of foreign trade development in Kaifeng in recent years, the steady improvement of economic conditions, and the steadily increase of government and enterprises’ investment with the improvement of policies. The degree of land use and low-carbon level of land showed a significant downward trend, which is because with the increase of land input, the number of idle land is also increasing, which makes the degree of land use continue to decrease, resulting in "negative external effects".
(2) From 2011 to 2020, the overall level of low-carbon intensive land use in Kaifeng City showed a slow downward trend. This trend was divided into three stages: the gradually increasing stage from 2011 to 2013 (the first stage), which was due to the sharp decrease in energy consumption, especially coal consumption, the stage of decreasing comprehensive value from 2013 to 2018 (the second stage), which was mainly due to the continuous increase of urban construction land, the continuous development of the Central Plains Economic Zone, and the rapid increase in energy demand for infrastructure construction and industrial development, and the stage of increasing comprehensive value from 2018 to 2020 (the third stage), which was mainly because in recent years, high-quality development policies have been continuously introduced, the use of various types of land has been continuously balanced, the structure of related industries has been continuously adjusted, and people’s awareness of low-carbon protection has continued to increase, which has promoted the improvement of land use level.
(3) The obstacle factors to the low-carbon intensive use of land in Kaifeng City had gradually changed from land output benefit and the degree of land use to low-carbon level of land and the degree of land use. In the future, Kaifeng City should transform the economic development mode, adjust the industrial layout, balance the demand for various types of land, curb the disorderly expansion of construction land, and promote the improvement of low-carbon intensive use level of urban land and the high-quality development of the city. Discussion
(1) There have been many studies on the low-carbon intensive use of land, but there are relatively few studies using the catastrophe progression and obstacle degree model methods to analyze the obstacle factors that affect the degree of land intensive use. Based on full consideration of the economic and social development of Kaifeng City, this study established an evaluation index system suitable for the actual situation of Kaifeng City, and used the obstacle degree model to analyze the obstacle factors affecting the degree of land use. The correlation between land use and urban development can be judged through research, which can provide a reference for high-quality urban development.
(2) The index system established by this study still needs to be tested, which is because there are many factors that affect the low-carbon intensive use of land, and the influences among the factors are different. Furthermore, the time period selected in this study is relatively short. In future studies, it is necessary to expand the time scale and explore the spatial differences of land use influencing factors to provide a more valuable basis.
References
［1］ WU YL, QU FT. Mechanism of intensive urban land use in China: Theoretical and practical study［J］. Resources Science, 2007(6): 106-113. (in Chinese)
［2］ FAN H, LIU WD, WU ZB. Spatio-temperal characteristics of internal coordination of intensive urban land use: A case study of the downtown of Wuhan［J］. Geographical Science, 2014(6): 696-704. (in Chinese)
［3］ ZHU YZ, CAO Y. Assessment of urban land intensive use based on PSR model: A case study of guangdong province［J］. Economic Geography, 2011(8): 1375-1380. (in Chinese)
［4］ CUI JM, JI WG. AHP-based fuzzy comprehensive evaluating for land intensive use level［J］. Research of Soil and Water Conservation, 2011(4): 122-125. (in Chinese)
［5］ YIN J, XIE JQ, WANG LD. The evaluation of urban land intensive use based on RS［J］. Journal of Natural Resources, 2007(5): 775-782. (in Chinese)
［6］ FAN PF, LIANG LT, CHEN CY, et al. Urban land intensive use evaluation and obstacle factor diagnosis: Based on ecological health and low-carbon development［J］. Bulletin of Soil and Water Conservation, 2016(4): 273-279. (in Chinese)
［7］ WANG YJ, WU CF, LUO WB, et al. Research on evaluation of city land-use system based on recycling economic development: A case study of Wuhu City in Anhui Province［J］. China Land Science, 2008(4): 25-31. (in Chinese) ［8］ LI KQ, CHEN YR, CHEN JR. An evaluation model for the low-carbon and intensive urban land use using analytic network process［J］. Economic Geography 2013(2): 156-161. (in Chinese)
［9］ LU FX, WANG X, QIN YC, et al. Theoretical basis of low-carbon development research［J］. China Population, Resources and Environment, 2012(9): 8-14. (in Chinese)
［10］ YANG YN, CHEN HG, CHEN LG. The intensive utilization of urban land based low-carbon economy［J］. Environmental Science and Management, 2011(3): 145-148. (in Chinese)
［11］ SHANGGUAN CX, WANG Y, GUO HJ. Study on intensive use of construction land in Henan Province based on low-carbon concept［J］. Research of Soil and Water Conservation, 2014(1): 234-239. (in Chinese)
［12］ SUN WW, MEI Y, CHEN YR, et al. Decoupling analysis of low-carbon economy and intensive land utilization of Zhengzhou City［J］. Bulletin of Soil and Water Conservation, 2015(4): 172-181.
［13］ LI KQ, CHEN YR. Evaluation on the intensity of urban land use based on low-carbon concept: A case study of Nanjing City［J］. China Land Science, 2013(1): 61-66. (in Chinese)
［14］ ZHANG JF, ZHANG AL, DONG J. Study on relationship of intensive land use and carbon emission: A case study of Wuhan urban agglomeration［J］. Research of Agricultural Modernization, 2013(6): 717-721. (in Chinese)
［15］ WANG X, PENG HJ, FAN PF, et al. Intensive use evaluation of cultivated land and diagnosis of its obstacle factors: Based on catastrophe progression method［J］. Resource Development & Market, 2016(8): 902-906. (in Chinese)
［16］ WEI HJ, ZHANG YF, ZHU N, et al. Evaluation on development level and coordination of low-carbon economy based on catastrophe progression model: A case study of Shaanxi Province［J］. Bulletin of Soil and Water Conservation, 2014(6): 305-310. (in Chinese)
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［19］ LIANG LT. Evaluation of rural ecol-environmental stress based on catastrophe progression method［J］. Journal of Arid Land Resources and Environment, 2013, 27(7): 46-51. (in Chinese)
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Key words Low-carbon intensive use of urban land; Entropy value method; Catastrophe progression; Obstacle degree; Kaifeng City
Received: July 13, 2021 Accepted: September 15, 2021
Supported by Basic Scientific Research Business Expense Project of Scientific Research and Development of Henan Academy of Sciences (210601043).
Chenguang YUAN (1993-), male, P. R. China, master, devoted to research about land use and resource economy.
*Corresponding author.
As the scale of cities continues to expand, people’s demand for land continues to increase. Meanwhile, how to use urban land effectively with high quality has become a hot issue, and the low-carbon intensive use of land is closely related to people’s lives. Improving the efficiency of land use is conducive to promoting the high-quality development of urban land while combining national hotspot policies. At this stage, scholars have already made richer research results on land use. Scholars have made in-depth explorations on the influencing factors, evaluation systems, evaluation methods, and driving mechanisms of land intensive use from different spatial scales and research perspectives. For example, Wu and Qu［1］discussed the mechanisms affecting land use from the economic, institutional and ecological levels; Fan and Liu［2］explored land structure and land functions in depth; Zhu and Cao［3-4］constructed a PSR model to reveal the spatial differences in land use in Guangdong Province; Yin et al.［5］used RS and ANN evaluation methods to conduct in-depth discussions on the intensive use of urban land in Shijiazhuang City; and Fan and Liang et al.［6-7］analyzed the land use status and obstacle factors in the Beijing-Tianjin-Hebei region from the ecological and low-carbon perspective. Above studies mostly use subjective methods to determine the impact mechanism of land use, and seldom use standard deviations of indexes to determine the weight values in overall index systems and use models to determine obstacle factors. Therefore, in this study, the catastrophe progression and obstacle degree model were introduced to investigate low-carbon intensive use of urban land, so as to reveal the level of low-carbon intensive use of urban land and its obstacle factors in Kaifeng City from 2011 to 2020, and provide a reference for the high-quality development of Kaifeng City. Data Sources and Study Methods
Data source and processing
The data of this study were obtained from the 2011-2020 Kaifeng City Statistical Yearbook. Some statistics related to population, output value, etc. sourced from the website of Henan Provincial Bureau of Statistics (http:∥www.ha.stats.gov.cn). When calculating relevant data, data errors were eliminated by standardization, as shown in formula 1:
yij=xijmax (xij) (Positive effect index)
yij=1-xijmax (xij) (Negative effect index)(1)
In the formula: xij and yij respectively represent the original value and the dimensionless value of the jth index in the ith year, respectively.
Study methods
The entropy method
The entropy method is a method to determine the weight value according to the degree of dispersion among indexes. In this study, the entropy method was used to determine the specific degree of dispersion among the low-carbon intensive use indexes of land in Kaifeng City to determine the weight values. The formulas were giving below. In the following formulas, m is the number of statistical years, and n is the number of indexes.
(1) Calculation of the proportion Rij of the index value xij:
Rij=xij/∑mi=1xij(2)
(2) Calculation of the entropy of the jth index:
ej=-1lnm∑mi=1Rij×lnRij(3)
(3) Calculation of information entropy redundancy:
dj=1-ej(4)
(4) Calculation of the weight of the jth index:
Wj=dj/∑mi=1dj(5)
Catastrophe progression method
The catastrophe progression method is to perform multi-layer decomposition of a target, and its specific quantification using catastrophe theory and the principle of normalization, so as to comprehensively evaluate the target［15-20］. In this study, we carried out the evaluation of the low-carbon intensive use of urban land following the steps of constructing an evaluation index system, ranking indexes, establishing a multi-level hierarchical structure model, and using a normalization formula to calculate the value of the catastrophe membership function step by step.
Obstacle degree model
The diagnosis of obstacle factors was to analyze introduced factor contribution degree Uj, index deviation degree Vj, and obstacle degree Mj to determine main obstacle factors that affect the low-carbon intensive use of land and their degrees of influence. The specific calculation process was as below［15］:
Uj=wij(6) Vj=1-zj(7)
Mj=Uj×Vj∑nj(Uj×Vj)×100%(8)
Cj=∑Mj(9)
In the formula: wij is the weight of the jth index factor of the ith layer; zj is the standardized value of the jth index of the ith layer; and Mj and Cj are the obstacle degrees of the index-layer factor and the criterion-layer factor, respectively.
Evaluation index system for low-carbon intensive use of urban land
We believed that the core of low-carbon intensive use of land is to create higher benefits with lower emissions and consumption［8-11］to achieve high-quality development. According to the characteristics of the rationality, high efficiency, and conservation and intensiveness of land use, combined with related research［6,8,10-14］, such four indexes as land input level, land use degree, land output benefit, and land low-carbon level were selected as a criterion level, and 15 indexes were selected on this basis to construct an evaluation index system for the low-carbon intensive use of urban land in Kaifeng City, as shown in Table 1.
Case Analysis
Determination of the weights of evaluation indexes for the low-carbon intensive use of land in Kaifeng City
According to formulas (3)-(6), the specific weights of the evaluation indexes for the low-carbon intensive use of land in Kaifeng City were obtained, as shown in Table 2.
Evaluation level division
Generally, the evaluation values of the low-carbon intensive use of urban land calculated by the normalization formula are relatively high, and the differences between values are small, so the degree of distinction is not high, and it is difficult to evaluate the quality of the target. Therefore, it is necessary to design an evaluation standard suitable for the catastrophe progression method［16-18］. According to the catastrophe theory, the catastrophe level value was divided into five levels: highly intensive (0.8-1.0), relatively intensive (0.6-0.8), generally intensive (0.4-0.6), relatively extensive (0.2-0.4), extensive (0-0.2), as shown in Table 3.
Analysis of results
Evaluation results of the low-carbon intensive use of urban land in Kaifeng City
According to the index weights determined by the entropy method, the catastrophe progression model was used to calculate the low-carbon intensive use level of urban land in Kaifeng City from 2011 to 2020. The results are shown in Table 4.
Combining with Table 4, the land use change status of Kaifeng City was analyzed from two aspects: index level and comprehensive level. ① Index factor analysis: The land input level and land output level in the index layer from 2011 to 2020 showed an upward trend. The evaluation value of the land input level increased from 0.924 0 in 2011 to 0.934 2 in 2020, and the evaluation value of the land output level increased from 0.951 7 in 2011 to 0.999 3 in 2020, which is due to the continuous improvement of the core area for foreign trade development in Kaifeng City in recent years, the steady improvement of economic conditions, and the steady increase of government and enterprise investment in land along with the improvement of policies. From 2011 to 2020, the land use degree and land low-carbon level showed a significant downward trend. The land use degree dropped from 0.900 2 in 2011 to 0.722 4 in 2020, and the low-carbon level of land dropped from 0.887 6 in 2011 to 0.790 4 in 2020, which is because with the increase of land input, and idle land is also increasing, which makes the degree of land use continue to decrease, resulting in "negative external effects". Especially in daily life, affected by carbon sources and carbon sinks, low-carbon use of land is seriously threatened.
Chenguang YUAN et al. Evaluation and Obstacle Diagnosis of Low-carbon Intensive Land Use in Kaifeng City ② Comprehensive level analysis: From 2011 to 2020, the evaluation value of low-carbon intensive land use in Kaifeng City was in the range of 0.915 9-0.861 6, showing a slow declining trend. This trend was divided into three stages: from 2011 to 2013 (the first stage), the comprehensive value changed from 0.915 9 to 0.936 5, and reached its peak in 2013, which was due to the sharp decrease in energy consumption, especially coal consumption; from 2013 to 2018 (the second stage), the comprehensive value changed from 0.936 5 to 0.828 3, which was mainly due to the continuous increase of urban construction land, the continuous development of the Central Plains Economic Zone, and the rapid increase in energy demand for infrastructure construction and industrial development; and from 2018 to 2020 (the third stage), the comprehensive value changed from 0.828 3 to 0.861 6, which was mainly because in recent years, high-quality development policies have been continuously introduced, the use of various types of land has been continuously balanced, the structure of related industries has been continuously adjusted, and people’s awareness of low-carbon protection has continued to increase, which has promoted the improvement of land use level. Diagnosis results of obstacle factors for low-carbon intensive use of urban land in Kaifeng City
According to the evaluation results in "Evaluation results of the low-carbon intensive use of urban land in Kaifeng City", the obstacle degree of each index was calculated using the obstacle degree model in "Obstacle degree model", as shown in Table 5.
In order to directly reflect the obstacle factors affecting the low-carbon intensive use of land in Kaifeng City, taking the basic year and the final year as the time nodes, the main obstacle factors with obstacle degrees ranked in the top 5 were selected, and the obstacle degree was calculated according to the formulas in "Obstacle degree model". The details are shown in Table 6.
It can be seen from Table 6 that in the basic year of 2011, obstacle factors for the low-carbon intensive use evaluation of Kaifeng City’s land were concentrated in the green coverage of built-up areas, per capita road area, population density, GDP per square kilometer, and retail sales of social consumer goods per square kilometer; the obstacle factors in 2020 were concentrated in the coefficient of land use carbon structure, energy consumption per square kilometer, carbon emissions per square kilometer, carbon emissions per capita, and use efficiency of non-agricultural land. The analysis showed that the obstacle factors in the basic year were manifested in land use output and benefit, and the obstacle factors in the final year period were manifested in the low-carbon use of land, that is, as time progresses, low-carbon use of land has become the main basis for the high-quality development of urban land. According to the method under "Obstacle degree model", the obstacle degrees of the index layer were calculated as shown in Table 7.
It can be seen from Table 7 that the obstacle degree of low-carbon intensive use of land in Kaifeng City from 2011 to 2020 showed significant differences. In 2011, land output benefit became the main obstacle factor to land use; and in 2020, the low-carbon level of land became the main obstacle factor. Analyzing the overall trend, the obstacle degrees of land input and output were decreasing, and the obstacle degree of low-carbon land was increasing. It can be predicted that in the next few years, low-carbon use will become the focus of urban development. Therefore, balancing the demand for land, improving the land structure, and ensuring the orderly and stable development of the urban land market are the main means to promote the high-quality development of Kaifeng City. Conclusions
In this study, we attempted to use the catastrophe progression and obstacle degree model methods to characterize the change trend of the low-carbon intensive use level of urban land in a small-scale space. Combining the evaluation criteria, the entropy method was used to objectively assign weights, and the catastrophe progression and obstacle degree model methods were introduced to reveal the low-carbon intensive use of urban land in Kaifeng City from 2011 to 2020 and its obstacle factors. The main conclusions were given as below.
(1) The land input and land output levels in the index layer between 2011 and 2020 showed an upward trend, which is due to the continuous improvement of the core area of foreign trade development in Kaifeng in recent years, the steady improvement of economic conditions, and the steadily increase of government and enterprises’ investment with the improvement of policies. The degree of land use and low-carbon level of land showed a significant downward trend, which is because with the increase of land input, the number of idle land is also increasing, which makes the degree of land use continue to decrease, resulting in "negative external effects".
(2) From 2011 to 2020, the overall level of low-carbon intensive land use in Kaifeng City showed a slow downward trend. This trend was divided into three stages: the gradually increasing stage from 2011 to 2013 (the first stage), which was due to the sharp decrease in energy consumption, especially coal consumption, the stage of decreasing comprehensive value from 2013 to 2018 (the second stage), which was mainly due to the continuous increase of urban construction land, the continuous development of the Central Plains Economic Zone, and the rapid increase in energy demand for infrastructure construction and industrial development, and the stage of increasing comprehensive value from 2018 to 2020 (the third stage), which was mainly because in recent years, high-quality development policies have been continuously introduced, the use of various types of land has been continuously balanced, the structure of related industries has been continuously adjusted, and people’s awareness of low-carbon protection has continued to increase, which has promoted the improvement of land use level.
(3) The obstacle factors to the low-carbon intensive use of land in Kaifeng City had gradually changed from land output benefit and the degree of land use to low-carbon level of land and the degree of land use. In the future, Kaifeng City should transform the economic development mode, adjust the industrial layout, balance the demand for various types of land, curb the disorderly expansion of construction land, and promote the improvement of low-carbon intensive use level of urban land and the high-quality development of the city. Discussion
(1) There have been many studies on the low-carbon intensive use of land, but there are relatively few studies using the catastrophe progression and obstacle degree model methods to analyze the obstacle factors that affect the degree of land intensive use. Based on full consideration of the economic and social development of Kaifeng City, this study established an evaluation index system suitable for the actual situation of Kaifeng City, and used the obstacle degree model to analyze the obstacle factors affecting the degree of land use. The correlation between land use and urban development can be judged through research, which can provide a reference for high-quality urban development.
(2) The index system established by this study still needs to be tested, which is because there are many factors that affect the low-carbon intensive use of land, and the influences among the factors are different. Furthermore, the time period selected in this study is relatively short. In future studies, it is necessary to expand the time scale and explore the spatial differences of land use influencing factors to provide a more valuable basis.
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