This study analyzes the evolution characteristics of “production-living-ecological” space in Zhangjiakou City during the period of 2000–2020, measures its carbon effect in the vertical and horizontal directions, and discusses its ecological relationship and its impact on carbon effect, based on the relationship between “production-living-ecological” space and carbon source/carbon classification system. The results show that “production-living-ecological” space in Zhangjiakou has changed significantly during 2000–2020, with an increase of 710.24 km² in ecological space, 652.55 km² in production-living space and a decrease of 1362.79 km² in production-ecological space. The transformation of the three types of space has become more intense from 2000 to 2020 in Zhangjiakou City. Vertically, the carbon flux of Zhangjiakou City increases from 26.9518 million tons to 48.9436 million tons. Carbon emission is more than carbon uptake and the imbalance of carbon budget is serious during 2000–2020. Horizontally, the carbon absorption intensity of ecological space gradually increases, and the carbon emission intensity of production-ecological space and production-living space continues to decline in Zhangjiakou City. In the past 20 years, the positive carbon flow has increased by 8.23 million tons, and the negative carbon flow has decreased by 11.82 million tons, but the overall net carbon flow is still negative. The spatial ecological relationship among the “production-living-ecological” space has obvious conflicts, mainly manifested as plundering-restriction and competition relationship, showing a negative impact on the carbon.

Taking Zhangjiakou City, the central city of mountainous area of northern Hebei Province, as a study area, the spatial pattern and evolution characteristics were analyzed by using land transfer matrix, land use dynamic degree and landscape index, from the aspects of quantitative structure, spatial layout, vertical gradient and landscape spatial pattern. The results were as follows. 1) There was great regional diversity in the evolution characteristics of the “production-living-ecological” (PLE) space of Zhangjiakou City. The ecological space was mainly distributed in Yanshan mountain and Taihang mountain in the east of the study area, and production-living space and production-ecological space were concentrically distributed in Yanghe river valley basin, Sanggan river basin and Huliu river basin, potential space was scattered around the central and western production-living space. 2) In the past 25 years, the PLE space of Zhangjiakou City had different degrees of mutual transformation, while the mutual transformation of ecological space and production-ecological constituted the main type of evolution of the territory space pattern. Compared with 1990–2000, the PLE space changed more frequently from 2000 to 2015. 3) The types of territorial space were more diverse in middle and lower mountain and gentle slope zones from the vertical spectrum. In the past 25 years, ecological space expanded to high-altitude and high-slope zones, while production-ecological space transferred to low-altitude and low-slope zones. 4) The landscape pattern of the PLE space in Zhangjiakou City tended to be fragmented and complicated. 5) The natural geographical environment was the natural basis and spatial carrier of the spatial distribution of the PLE. The aggravation of industrialization and urbanization, social and economic development and policy factors were the reasons for the spatial pattern changes of the PLE space in Zhangjiakou City.

In order to support the scientific forest conservation policy and sustainable development, through collecting and analyzing the domestic and foreign academic literature about “Forest Transition”, this paper summarized the concept, connotation, theories, research framework, methods and impact factors, put forward the future research focus and prospect of “Forest Transition”, and proposed an integrated theoretical framework of “Forest Transition”, The main conclusions are as follows. 1) The concept of “Forest Transition” refers to the reversal trend of forest area from reduction to increase, which is the result of the mutual adaptation of socialeconomic-environment system. “Forest Transition” is the comprehensive reflection of land use. The main core issue of “Forest Transition” research is the driving factors and internal mechanism of reversal trend. 2) “Forest Transition” has the characteristics of particularity, occasionality and concurrency. It has the characteristics of nonlinear dynamics, obvious turning point and multi-dimension. 3) “Forest Transition” has many paths (economic development path, forest scarcity path, globalization path, national forest policy path, intensive of peasant land use path). At present, the mechanism of “Forest Transition” is mainly explained by relative rent of forest-land use, land quality adjustment and social-ecological feedbacks. 4) Currently, the achievements about “Forest Transition” are plentiful but still need to integrate multi-source data and methods in accordance with a more comprehensive theoretical research framework of overall analysis, follow the research line of “concept-process-mechanism-effectapplication”, focus on systematic scale synthesis and heterogeneity, expand the scope of case studies, deepen interdisciplinary research, and strengthen policy application.

Based on land use data of Zhangjiakou in 2000, 2010 and 2015, this paper investigated the spatiotemporal variation of habitat quality pattern of Zhangjiakou City by using InVEST, in order to understand the spatial patterns associated with the change of land use and habitat quality change, further introducing the geographical weighted regression (GWR) model, to quantitativly analyze the influence of cultivated land, woodland, grassland and construction land change on the evolution of habitat quality. The results showed that in the year 2000–2015, cultivated land, forest land and grassland were the main types of land use in Zhangjiakou City, during the reduction of cultivated land, forest land and construction land kept increasing, with farmland to woodland, grassland and construction land, grassland to forest landand construction land as the main transfer directions of change. During 2000–2015, Zhangjiakou City habitat quality was at a higher level overall and kept improving. Habitat quality was highest in northeast mountain area, Bashang plateau and the the Sanggan River valley region was lower, and the lowest level of habitat quality was in Yanghe River watershed. The influence of each land use type on habitat quality had significant spatio-temporal heterogeneity, and the change of forest land was positively correlated with habitat quality overall and most influential. The grassland had a positive correlation with the habitat quality, and its regression coefficient decreased from north to south. The main performance of cultivated land, construction land and habitat quality was negative correlation in space, but some area was positive correlation. The reason for the large heterogeneity of the regression coefficients in different regions lied in the different dominant types of habitat quality changes in different regions. The change of habitat quality in the plateau area and the northeast mountain area was mainly affected by woodland and grassland changes, and in Sanggan River and Yanghe River, the change of habitat quality basin for cultivated land and construction land.