The temporal response of forests to CO-induced climate changes was examined for eastern North America. A forest stand simulation model was used with the assumption that climate will change at a constant rate as atmospheric CO doubles, and then as CO doubles again. Before being used to project future vegetation trends, the simulation model FORENA was verified by its ability to reproduce long, temporal sequences of plant community change recorded by fossil pollen and by its ability to reproduce today's vegetation. The simulated effects of changing monthly temperature and precipitation included a distinctive dieback of extant trees at most locations, with only partial recovery of biomass in areas of today's temperate deciduous forest. In the southern portion of today's deciduous-coniferous transition forests the simulated dieback was indistinct and recovery by deciduous tree species was rapid. In more northerly transition areas, the dieback not only was clearly expressed, but occurred twice, when new dominant species replaced extant conifers, then were themselves replaced, as climate change continued. Boreal conifers also underwent diebacks and were replaced by deciduous hardwoods more slowly in the north than in the south. Transient responses in species composition and carbon storage continued as much as 300 years after simulated climate changes ceased.

Land-use change models are important tools for integrated environmental management. Through scenario analysis they can help to identify near-future critical locations in the face of environmental change. A dynamic, spatially explicit, land-use change model is presented for the regional scale: CLUE-S. The model is specifically developed for the analysis of land use in small regions (e.g., a watershed or province) at a fine spatial resolution. The model structure is based on systems theory to allow the integrated analysis of land-use change in relation to socio-economic and biophysical driving factors. The model explicitly addresses the hierarchical organization of land use systems, spatial connectivity between locations and stability. Stability is incorporated by a set of variables that define the relative elasticity of the actual land-use type to conversion. The user can specify these settings based on expert knowledge or survey data. Two applications of the model in the Philippines and Malaysia are used to illustrate the functioning of the model and its validation.

Urban agglomeration has been the inevitable result of China's rapid industrialization and urbanization over the last 30 years. Since the early 2000s, urban agglomeration has become the new regional unit participating in international competition and the division of labor. China has declared urban agglomeration the main spatial component of new types of urbanization over the next decade as clarified at the first Central Urbanization Working Conference and in the National New-type Urbanization Plan (2014?2020). However, research on urban agglomeration remains weak and needs to be strengthened. From 1934 to 2013, only 19 papers published in Acta Geographica Sinica contained the theme of urban agglomeration (0.55% of the total number of articles published) and the first paper on urban agglomeration appeared less than 10 years ago. Despite a small number of divergent studies, this work has contributed to and guided the formation of the overall pattern of urban agglomeration in China. For example, spatial analyses have promoted the formation of the fundamental framework of China's urban agglomeration spatial structure and guided the National New-type Urbanization Plan; spatial identification standards and technical processes have played an important role in identifying the scope and extent of urban agglomeration; serial studies have facilitated pragmatic research; and problems with the formation and development of urban agglomeration have provided a warning for future choices and Chinese development. Future research into urban agglomeration in China should (1) review and examine new problems in China's urban agglomeration options and cultivation; (2) critically consider urban agglomeration when promoting the formation of the 5+9+6 spatial pattern; (3) rely on urban agglomeration to construct new urbanization patterns such as 'stringing the agglomerations with the axis, supporting the axis with the agglomerations'; and (4) deepen national awareness about resources, environment effects and environmental carrying capacity in high density urban agglomerations, management and government coordination innovation, the construction of public finance and fiscal reserve mechanisms, the technical regulation of urban agglomeration planning, and standards for identifying the scope and extent of urban agglomeration.

In this article, we examine the economic linkage and competition among cities in the great metropolitan region of Jing-Jin-Ji. Specifically we demonstrate that Beijing, Tianjin and Hebei Province have developed their unique industry structures and gained corresponding comparative advantages since the beginning of the reform and opening up. Accordingly, we propose the function orientation of Beijing, Tianjin and Hebei Province based on their industrial characteristics and the principle of strategic interest of the country.

Mega- urban agglomerations in China play a vital role in both national economic development strategies and national new-type urbanization, and undertake important historical responsibility with the world economic center transfer to China. However, they suffer a series of increasingly serious eco- environmental problems in the process of development. Thus,studies on the interactive coupled effects between urbanization and eco-environment in megaurban agglomerations are the frontier areas and high priority tasks in the earth system science for the future ten years. This paper analyses the basic theory frame of the interactive coupled effects between urbanization and eco- environment in mega- urban agglomerations systematically. In theoretical aspect, based on the nonlinear relationship and coupling characteristics of the natural and human elements in mega- urban agglomerations system, we could estimate the interactive coercing intensity, nearcoupling and telecoupling mechanism ofthe inside and outside mega-urban agglomerations system after scientific identification of the key elements, and then form the basic interactive coupling theory. Moreover, we could build a spatio- temporal coupling dynamic model, which is integrated with multi- elements, multiscales,multi-scenarios, multi-modules and multi-agents. The model will be used to develop the intelligent decision support system for urban agglomeration sustainable development. In methodology aspect, the mega- urban agglomeration is regarded as an open complex giantsystem. We should establish the standardized shared database for exploring the interactive coupled effects between urbanization and eco- environment. Then using new technology for analyzing big data and the integration methods incorporating of multi- elements, multi- scales,multi- targets, multi- agents, multi- scenarios and multi- modules, we can build a methodology framework to analyze the complex interaction coupling between urbanization and ecoenvironment. The technical route is to analyze spatiotemporal evolution characteristics, identifythe key elements, interpret coupling relationship, reveal the mechanism of coercing effect, find the general rules, filtrate the control variables, solve the critical thresholds, conduct regulation experiments, simulate different scenarios, propose an optimized schemes, and achieve national goals. Furthermore, we could put forward the overall optimization scheme. In general, this research could provide theoretical guidance and method support for the transformation and sustainable development in mega-urban agglomerations.

Promoting coordinated development of the Beijing-Tianjin-Hebei Urban Agglomeration is not only a major national strategy, but also a long-term complex process. It is necessary to apply scientific theories and respect the laws of nature to realize the strategic target of common prosperity, share a clean environment, share the burden of risk of development, and build a world-class metropolis for the Beijing-Tianjin-Hebei Urban Agglomeration. This article examines the scientific foundation and patterns of coordinated development of the Beijing-Tianjin-Hebei Urban Agglomeration. Synergy theory, game theory, dissipative structure theory, and catastrophe theory are the theoretical basis of coordinated development of the Beijing-Tianjin-Hebei Urban Agglomeration. Synergy theory is the core theory for the coordinated development of the Beijing-Tianjin-Hebei Urban Agglomeration. The coordinated development process of the Beijing-Tianjin-Hebei Urban Agglomeration is a non-linear spiral progress of game, coordination, mutation, game, resynchronization, and mutation. Each game-coordination-mutation process promotes the coordinated development of the urban agglomeration to a higher level of coordination, and the progress fluctuates. This process includes eight stages: assistance phase, cooperation phase, harmonization phase, synergy phase, coordination phase, resonance phase, integration phase, and cohesion phase. Further analysis shows that the real connotation of coordinated development of the Beijing-Tianjin-Hebei Urban Agglomeration is to realize the coordination of planning, transportation, industrial development, urban and rural development, market, science and technology, finance, information, ecology, and the environment, as well as the construction of a collaborative development community. The Beijing-Tianjin-Hebei Urban Agglomeration will achieve advanced collaboration from low-level collaborative phase through regional coordination on planning, construction of traffic network, industrial development, joint development of urban and rural areas, market consolidation, science and technology cooperation, equal development of financial services, information sharing, ecological restoration, and pollution control. This study may provide a scientific foundation and theoretical basis for the coordinated development of the Beijing-Tianjin-Hebei Urban Agglomeration.

Urban spatial expansion has been research hotspot of urban geography for a long time. However, urban spatial progress and its driving forces showed diversified state under the context of different political systems and different development phases in the world. For example, there are debates on metropolitan expansion path between Western countries and China. One view advocated that metropolitan spatial expansion showed a trend from clustered to dispersed under the role of scale-economy. Another view found that above theory could not explain metropolitan spatial expansion progress in developing countries, such as China and India. In these metropolitan regions, rapid urban spatial expansion existed in "urban-rural integration" areas, not central big cities of metropolitan regions. Thus, it was different from Western developed countries due to particular political and economic factors in developing countries. In order to clarify metropolitan spatial pattern in a transitional period from planned economy to market economy, we utilized nighttime light data to analyze Beijing-Tianjin-Hebei metropolitan area from 1992 to 2012 as a case. A series of measurement methods has been used in the study, such as expansion intensity index, spatial correlation model and multi-dimensional model. The results are as follows: (1) Beijing, Tianjin, Tangshan were hotspot regions of metropolitan expansion during the whole research period. "Triangle region" among Baoding-Tianjin-Hebei were coldspot regions of metropolitan expansion. (2) Although metropolitan expansion has showed a dispersed trend, centralized powers are still strong in the progress of metropolitan development. (3) Metropolitan driving forces showed a diversified state. Market power was the main driving forces, followed by administration power, exogenous power and endogenous power. Market power, administration power and exogenous power has showed an upward trend. However, endogenous power has showed a downward trend. (4) We put forward some policy suggestions to optimize metropolitan spatial structure, such as reducing administrative intervention, building market-driven mechanism, strengthening internal and external two-way reform and promoting industrial upgrade.

Research into urban expansion patterns and their driving forces is of great significance. Under the background of the integrated development of the Beijing-Tianjin-Hebei (Jing-Jin-Ji) urban agglomeration, it is important to study the temporal and spatial patterns of urban land expansion and the driving forces development. This paper uses land-use data of the Jing-Jin-Ji urban agglomeration from 1990 to 2015 and reveals the multi-dimensional characteristics of the urban land expansion patterns. We then combine the urban spatial interaction and the spatial and temporal nonstationarity of the urban land expansion process and build the center of gravity-geographically and temporally weighted regression (GTWR) model by coupling the center of gravity model with the GTWR model. Using the center of gravity-GTWR model, we analyze the driving forces of urban land expansion at the city scale, and summarize the dominant mode and core driving forces of the Jing-Jin-Ji urban agglomeration. The results show that: (1) Between 1990 and 2015, the expansion intensity of the Jing-Jin-Ji urban agglomeration showed a down-up-down trend, and the peak period of expansion was in 2005-2010. Before 2005, high-speed development was seen in Beijing, Tianjin, Baoding, and Langfang, which were then followed by rapid development in Xingtai and Handan. (2) Although the center of gravity of cities in the Jing-Jin-Ji urban agglomeration showed a divergent trend, the local interaction between cities was enhanced, and the driving forces of urban land expansion showed a characteristic of spatial spillover. (3) The spatial development mode of the Jing-Jin-Ji urban agglomeration changed from a dual-core development mode to a multi-core development mode, which was made up of three function cores: the transportation core in the northern part, the economic development core in the central part, and the investment core in the southern part. The integrated development between functional cores led to the multi-core development mode. (4) The center of gravity-GTWR model analyzes urban land expansion as a space-time dynamic system. The model proved to be feasible in the analysis of the driving forces of urban land expansion.

Quantifying the impact of urbanization on extreme climate events is significant for ecosystem responses, flood control, and urban planners. This study aimed to examine the urbanization effects on a suite of 36 extreme temperature and precipitation indices for the Beijing-Tianjin-Hebei (BTH) region by classifying the climate observations into three different urbanization levels. A total of 176 meteorological stations were used to identify large cities, small and medium-size cities and rural environments by applying K-means cluster analysis combined with spatial land use, nighttime light remote sensing, socio-economic data and Google Earth. The change trends of the extreme events during 1980-2015 were detected by using Mann-Kendall (MK) statistical test and Sen's slope estimator. Urbanization effects on those extreme events were calculated as well. Results indicated that the cool indices generally showed decreasing trends over the time period 1980-2015, while the warm indices tended to increase. Larger and more significant changes occurred with indices related to the daily minimum temperature. The different change rates of temperature extremes in urban, suburban and rural environments were mainly about the cool and warm night indices. Urbanization in medium-size cities tended to have a negative effect on cool indices, while the urbanization in large cities had a positive effect on warm indices. The significant difference of urbanization effect between large and medium-size cities lay in the daily maximum temperature. Results also demonstrated the scale effect of the urbanization on the extreme temperature events. However, the results showed little evidence of the urban effect on extreme precipitation events in the BTH region. This paper explored the changes in temperature and precipitation extremes and qualified the urbanization effects on those extreme events in the BTH region. The findings of this research can provide new insights into the future urban agglomeration development projects. (C) 2019 Elsevier B.V.

For quantitatively explaining the relationship between the vascular plant abundance and habitat factors in the Qinghai-Tibet Plateau, a spatial simulation method has been developed to simulate the distribution of vascular plant species abundance. In this paper, seven datasets covering 37 national nature reserves were used to screen the best correlation equation between the vascular plant abundance and habitat factors in the plateau. These datasets include imformation on the vascular plant type, land cover, mean annual biotemperature, average total annual precipitation, topographic relief, patch connectivity and ecological diversity index. The results show that the multiple correlation coefficient between vascular plant abundance and various of habitat factors is 0.94, the mean error validated with the vascular plant species data of 37 national nature reserves is 2.21 types/km2, and the distribution of vascular plant species abundance gradually decreases from southeast to northwest, and reduces with increasing altitude except for the desert area of Qaidam Basin on the Qinghai-Tibet Plateau. Furthermore, the changes of vascular plant species abundance in the plateau during the periods from 1981 to 2010 (T0), from 2011-2040 (T2), from 2041to 2070 (T3) and from 2071 to 2100 (T4) were simulated by combining the land cover change in China and the climatic scenarios of CMIP5 RCP2.6, RCP4.5 and RCP8.5. The results from T0 to T4 show that the vascular plant species abundance in the plateau would decrease in the future, the vascular plant species abundance had the biggest change ranges under RCP8.5 scenario and the smallest change ranges under RCP2.6 scenario. In short, dynamic change and interaction of habitat factors directly affect the spatial distribution of vascular plant species abundance on the Qinghai-Tibet Plateau.

From the policy allowing couples to have a second child if one parent is an only child to universal two-child policy, fertility policy in China had changed in succession, which had caused extensive social concerns and would have an influence on Chinese demographics in the future. This article projects the trend of total population and demographic structure in China after implementing the universal two-child policy by queue group element method from the demographic perspective, and analyzes the influence of the policy on Chinese population spatial distribution from a geographic perspective. The results show that: (1) Implementing a universal two-child policy can reduce the declining trend of the total population, aging of the population, and dropping of working age population. (2) Eastern China has the highest population density, followed by the central, northeastern, and western regions. Implementing a universal two-child policy can increase the population density of the area to the southeast of the Hu Line, but there will be little change to the northwest of the Hu Line. The current population spatial distribution pattern will continue to exist. (3) Based on the provincial-level annual change intensities of population density, China can be divided into rapid population growth zone, medium-speed population growth zone, slow population growth zone, and stable population zone.