## 1 Introduction  
Low-carbon governance has become an important element of global carbon emission reduction. Urban expansion has a certain locking effect on the good operation of cities and the release of urban carbon emissions. Because the main strategy in low-carbon urban planning is urban spatial planning, the relationship between carbon emissions and urban spatial expansion has been the focus of relevant research. The existing academic literature mainly focuses on this relationship, particularly studying land use, urban spatial form, urban compactness, urban transportation and construction control. The research on land use and carbon emissions mainly includes three aspects: land-use carbon-emission effect, land-use carbon emissions accounting and low-carbon land-use policy. [PERSON] [1] and [PERSON] [2] studied the impact of land-use change on carbon emissions; [PERSON] [3], [PERSON] [4], [PERSON] [5] and [PERSON] [6] considered the spatiotemporal pattern, spatial differentiation characteristics, spatial correlation and influencing factors, focused on the impact of landout mode on carbon emissions; [PERSON] [7], [PERSON] [8], [PERSON] [9] and [PERSON] [10] analyzed the relationship between construction land expansion and carbon emissions or carbon-emission intensity by building a Tapio decoupling model, a gray correlation model, a Kuznets curve model and a coupling coordination model. The calculation of land-use carbon emissions is conducted by using the model method [11, 12], sample plot inventory method [13, 14], remote sensing estimation method [15; 16; 17] and other calculation methods to study the change in carbon emissions with the dynamic change in land use. From the perspective of low-carbon land-use policy, [PERSON] [18], [PERSON] [19], [PERSON] [20] and [PERSON] [21] and [PERSON] [22] considered the policy aspect of the subject and proposed a study of the relationship between land-use control regulations and carbon emissions at the policy level. On urban morphology and carbon emissions, [PERSON], [PERSON] [23] analyzed the potential for greenhouse gas (GHG) emission reduction under different scenarios for three potential urban forms in Utsunomiya, Japan; [PERSON] [24], [PERSON] [25] and [PERSON] [26] used time-series data to analyze the impact of carbon-emission evolution on the urban spatial morphology of four cities, including Beijing, Shanghai, Tianjin and Guangzhou, and 108 cities in China, including the Yangtze River Delta, and agglomeration, as research objects. [PERSON] [27] studied the coupling relationship between the shape index of 35 urban built-up areas and carbon-emission intensity in China. [PERSON] [28] analyzed the relationship between urban morphology and carbon dioxide emissions of 264 Chinese cities; [PERSON] [29] discussed the empirical relationship between urban morphology and the CO\({}_{2}\) emissions of 104 prefecture-level cities in China; [PERSON] [30] collected data from 295 cities in China and quantified the urban form compactness (UFC) from 2000 to 2015. The STIRPAT model is used to estimate the impact of UFC on CO\({}_{2}\) emissions, and the panel threshold regression model is used to estimate the threshold effect that limits the impact of compact urban morphology on carbon emissions. [PERSON] [31] used extreme gradient enhancement and a multiscale geographically weighted regression model to study the different importance, spatial multiscale change and spatial heterogeneity of the socioeconomic and urban form of the CO\({}_{2}\) emissions of 275 cities in China in 2005, 2012 and 2015. Urban compactness and carbon emissions: [PERSON] [32], [PERSON] [33] and [PERSON] [34] studied the interaction and driving factors between urban compactness and carbon-emission intensity of Xiamen and Changsha Zhuzhou Xiangtan urban agglomeration, respectively. Urban transport and carbon emissions: Research on the relationship between transport and carbon emissions can be divided into two schools: centralism and decentralization.