Construction of a Territorial Space Classification System Based on Spatiotemporal Heterogeneity of Land Use and Its Superior Territorial Space Functions and Their Dynamic Coupling: Case Study on Qionglai City of Sichuan Province, China

Territorial space classification (TSC) provides the basis for establishing systems of national territory spatial planning (NTSP) and supervising their implementation in China, thus has important theoretical and application significance. Most of the current TSC research is related to land use/land cover classification, ignoring the connection of the NTSP policies and systems, failing to consider the spatiotemporal heterogeneity of land use superior territorial space functions (TSFs) and the dynamic coupling between land use and its superior TSFs on the result of TSC. In this study, we integrated the factors influencing the connection of NTSP policies and systems and established a theoretical framework system of TSC from the perspective of spatial form and functional use. By integrating the q-statistic method with spatiotemporal geographical analysis, we propose a method to construct a TSC system for Qionglai City of Sichuan Province in China based on the spatiotemporal heterogeneity of land use superior TSFs and the dynamic coupling between land use and its superior TSFs. It makes up for the deficiency of directly taking land use/land cover classification as TSC and solves the problems of ignoring the spatiotemporal heterogeneity of land use superior TSFs and the dynamic coupling between land use and its superior TSFs. Using this method, we found that the TSC of Qionglai City consists of 3, 7, and 14 first-, second-, and third-level space types, respectively. The key findings from this study are that land use superior TSFs show spatiotemporal heterogeneity in Qionglai, and coupling effects in spatial distribution were noted between land use types and their superior TSFs, as was temporal heterogeneity in the coupling degree and the structure of the TSFs corresponding to the land use types, which show obvious dynamics and non-stationarity of the functional structure. These findings confirm the necessity of considering the spatiotemporal heterogeneity of land use superior TSFs and the dynamic coupling between land use and its superior TSFs in TSC. This method of establishing a TSC system can be used to address a number of NTSP and management issues, and three examples are provided here: (a) zoning of urban, agricultural, and ecological space; (b) use planning of production, living and ecological space; (c) delimitation of urban development boundary, permanent basic farmland protection redline, and ecological protection redline.

The spatiotemporal heterogeneity of the relationship between PM2.5 concentrations and the surface urban heat island effect in Beijing, China

Air pollution and the urban heat island (UHI) effect are two serious problems in many cities and have become increasingly serious with accelerated urbanization. The relationship between fine particulate matter (PM2.5) and the UHI effect has become a research topic of major interest to help avoid the vicious cycle of the UHI effect and air pollution, but recent studies still focus on correlation analysis, lacking attention to the spatiotemporal heterogeneity of their relationship. Combining remote sensing and in situ data, this study analyzed the spatiotemporal heterogeneity of the interaction between the UHI effect and PM2.5 in Beijing over four seasons by using a coupling coordination degree model, and the characteristics of spatiotemporal heterogeneity were analyzed from both biophysical and socioeconomic aspects. The modified normalized difference water index (MNDWI) and normalized difference vegetation index (NDVI) were selected as the indices from a biophysical perspective. Urban functional areas derived from points of interest (POIs) were used to represent the area’s socioeconomic background. The results showed that the relationship between PM2.5 and the UHI effect has spatiotemporal heterogeneity. The areas exhibiting high degrees of coupling coordination were most widely distributed in spring, and the highest degree of coupling coordination appeared in summer. The four seasons of high coupling coordination areas occurred over four seasons, covering more than 58.3% of Beijing’s area, mainly concentrated in business-related functional areas. Areas where the positive interaction between the UHI effect and air pollution was weak tended to have a higher proportion of vegetation. The results of this work are of theoretical and management value for mitigating the threat of rapid urbanization to human health.

Spatiotemporal heterogeneity of <i>b</i> values revealed by a data-driven approach for the 17 June 2019 <i>M</i>_S 6.0 Changning earthquake sequence, Sichuan, China

The spatiotemporal heterogeneity of b values has great potential for helping in understanding the seismogenic process and assessing seismic hazard. However, there is still much controversy about whether it exists or not, and an important reason is that the choice of subjective parameters has eroded the foundations of much research. To overcome this problem, we used a recently developed non-parametric method based on a data-driven concept to calculate b values. The major steps of this method include (1) performing a large number of Voronoi tessellations and Bayesian information criterion (BIC) value calculation, selecting the optimal models for the study area, and (2) using the ensemble median (Q2) and median absolute deviation (MAD) value to represent the final b value and its uncertainty. We investigated spatiotemporal variations in b values before and after the 2019 Changning MS=6.0 earthquake in the Sichuan Basin, China. The results reveal a spatial volume with low pre-mainshock b values near the mainshock source region, and its size corresponds roughly with the rupture area of the mainshock. The anomalously high pre-mainshock b values distributed in the NW direction of the epicenter were interpreted to be related to fluid invasion. The decreases in b values during the aftershock sequence along with the occurrences of several strong aftershocks imply that b values could be an indicator of the stress state. In addition, we found that although the distribution characteristics of b values obtained from different methods of investigation are qualitatively consistent, they differ significantly in terms of their specific values, suggesting that the best way to study the heterogeneous pattern of b values is in the joint dimension of space-time rather than separately in time and space. Overall, our study emphasizes the importance of b-value studies in assessing earthquake hazards.