In the face of the changing global environment and disciplinary hot spots, the first National Physical Geography Conference —with the topic of "New Development and New Challenges of Physical Geography in the Context of Change"— was held in Nanjing on 20-22 November 2017. The forefront contents of contemporary physical geography research, namely combination of geography and sustainable development, integration of physical geographical elements and processes, and system decision with spatial data mining have been the focus. At present, Chinese physical geographers have made the subject theories more concise; deepened the physical geographical process studies; achieved preliminary integration of physical geographical processes in critical regions and basins based on theoretical and methodological innovations; and practically supported decision making for the sustainable development of the coupled social-ecological system. In future research, we should deepen the process research of subdisciplines in physical geography, promote the development of a comprehensive physical geography, and improve the observation and simulation of the land surface system. These will further consolidate the position of physical geography as a foundation in geographical sciences, and make important contributions to global sustainable development and meet the demands of national key development strategies.

Land change has long been the research hot-spot of geography, and is also the focus of multiple disciplines including resource and environment economics, ecology, and urban planning. Land change models and simulations are an effective approach for understanding the mechanism of human-environment interactions. The modeling results are also valuable for the government to make resource management and environmental policies. Researchers of different fields have applied various approaches based on their theories to develop land change models. Attention has evolved from modeling land cover types to representation of human decision-making behaviors. The methods have shifted from statistical to cellular automata that can better characterize spatial patterns, and to economic methods and agent-based methods that can better represent the processes and mechanisms of land change. Future land change models should focus coupling multiple methods cross scales. Land change processes should be better represented. The complexity of the human-environment system can be better explained by a combination of land change models and other earth system models. The application of models to support policymaking also needs more attention.

Ecosystem services bridge the natural environment and human well-being, and are the key content of coupled human-environment system research. This article puts forward a framework of research on ecosystem services for coupled human-environment systems, and systematically reviews the research hotspots of ecosystem services evaluation, ecosystem services trade-offs, ecosystem services driving factors, ecosystem supply-flow-demand, and identifies the key areas for future ecosystem services research. This article argues that: (1) international research on ecosystem services models have experienced a rapid development, and SAORES model is the outstanding representative of ecosystem service evaluation model in China; (2) ecosystem service trade-off analyses are relatively complex, and its mechanism depends on distinguish the relationships among ecosystem structure-process-function-service at multiple spatial and temporal scales; (3) natural factors are the basis of ecosystem services distribution, land use change can modify ecosystem structure, function, and services, and social and economic factors can lead to differences in ecosystem services trade-off and demand; (4) in order to clarify the coupling relationship between ecosystem service supply and demand, it is urgently needed to further identify the pathes of ecosystem service flowes; (5) future research of ecosystem services should include strengthening the analyses on the response of ecosystem services to global change, ecosystem services supply and demand flow focusing on the sustainable development aspect, integration and optimization of the dynamic evaluation of ecosystem services, the coupling of ecosystem services and human-environment systems, and the integration of ecosystem services and big data.

The integrated carrying capacity of regional resource and environment systems is an important foundation for the harmonious and sustainable development of the human-environment system, and thus has become a hot topic of integrated physical geography research. Great progress has been made in the study on the carrying capacity of regional integrated resource and environment systems. The main achievements include the establishment of a comprehensive and extensive evaluation index system, a focus on the coordination of human-environment relationships, development and application of comprehensive research methods, and a focus on the spatial and temporal dynamics of the integrated carrying capacity of resource and environment systems. At present, study on integrated carrying capacity of resource and environment systems are applied to regional economic development program management, such as spatial development, industrial planning, post-disaster reconstruction, and resource and environment monitoring and early warning. Future research, however, still needs to improve the evaluation index system and strengthen research on appropriate scale of analyses and dynamic changes of the integrated carrying capacity of resource and environment systems, in order to deepen the theoretical and empirical studies of integrated physical geography. This will provide supports for the research on the sustainability of regional resources, society, and ecological environment.

Regionalization is a fundamental way for geographers to cognize the world. As an important part of integrated physical geography, terrestrial system regionalization aims at revealing rules of regional differentiations of terrestrial system features and their interaction processes, supporting the development of reasonable land management policies. The topics and methods of terrestrial system regionalization are constantly changing and innovated with the development of society and economy. After a brief review of research on terrestrial system regionalization in China, this study summarized the progress of Chinese scholars in the research frontier, i.e., dynamic regionalization, quantitative optimization of multi-regionalization schemes, and automatic demarcation. The study of dynamic regionalization could effectively depict the pattern and process of terrestrial system, with important guidance for regional sustainable development in the context of global change, while the study of quantitative optimization of multi-regionalization schemes and automatic demarcation might offer significant theoretical and technical supports for automatic regionalization. Furthermore, this study discussed the research challenges faced today, including the challenges of undertaking terrestrial regionalization for coupled human and natural systems, integrating qualitative and quantitative methods, and carrying out regionalization from the global to local scales.

The geographical system is a complex system including multiple spheres and their interactions. A geographical system model is a coupled human and environmental system model for understanding and predicting changes in patterns and processes of the system. Geographical system models are important tools for supporting sustainable development policy making, and thus is a key scientific research area. During the past decades, geographical system models have been developed to examine global environmental problems such as global change and sustainable development. However, the existing geographical system models have limited ability to simulate and project changes in the complex coupled human-environmental system. This study reviewed the history of development of geographical system models, which is characterized by transitions from single process to multiple process, statistics-based to process-based, static to dynamic, and site level to regional and global scale simulations. We also summarized two important development trends of geographical system models: toward coupled human and natural processes and their interactions, and model-data synthesis. To support policy making for sustainable development in China and globally, developing geographical system models is urgent for the Chinese physical geography research community.