The foundation of food production lies in cultivated land, and the protection of cultivated land is the cornerstone to ensure national food security. Based on the food consumption data of Chinese residents from 1987 to 2020, this study introduced the concept of virtual land and imported food data to estimate the cultivated land area required for food and virtual imported cultivated land, and analyzed the overall and zonal agricultural planting structure of China at this stage. On this basis, it constructed the zonal regulation and coordination mechanism of cultivated land protection in China in the context of "Greater Food" approach. The Chinese dietary structure presented the characteristics of increasing animal food consumption and gradually focusing on meat. Therefore, this study found the following conclusions on the regulation of cultivated land: (1) From 1987 to 2020, the cultivated land required by the Chinese dietary structure gradually approached the critical value. The virtual imported cultivated land increased by nearly 20 times, and the cultivated land demand was changing to the orientation of diversified planting demand. (2) The total agricultural planting structure in China has not yet met the dietary consumption demand of residents, and there are problems of structural imbalance, insufficient supply, and excess inventory. There are significant differences in the agricultural planting structure of the nine major agricultural areas of China. (3) The transformation of cultivated land protection should take the protection of existing cultivated land resources as the base, the transformation of planting structure, the regulation of agricultural production layout as the main force, the implementation of regional coordination and the guarantee of appropriate international imports as the assistance, and the transfer of pressure on cultivated land resources to the living community as the core from a systematic perspective, so as to build a multi-directional protection mechanism for China's cultivated land. This study can provide a scientific reference for the formulation of cultivated land protection strategy oriented by food balance demand and provide a theoretical menu for ensuring national food security and sustainable resource utilization in the new era.

Soil organic carbon (SOC) storage and soil carbon sinks play a crucial role in the global carbon cycle of terrestrial ecosystem. However, many previous studies of soil carbon storage and sinks utilized low-resolution land use dataset, with limited focus on soil carbon sinks from farmland and grassland management. To address this issue, this study employed a series of accounting models to estimate the carbon sink from farmland and grassland management, the carbon sink from forest management, changes in soil carbon storage, changes in carbon storage due to land use conversion from 2000 to 2020, as well as the soil carbon storage in China in 2000 and 2020 using a 30 m-resolution land use dataset. The results showed that the national carbon sink from farmland management in China was approximately 17.918 Tg C a^-1 and the carbon sink from grassland management was approximately 20.171 Tg C a^-1 during 2000-2020. The carbon sink from forest management in China was approximately 81.622 Tg C a^-1 during 2000-2020. The soil carbon storage (0-100 cm) in China increased from 86.074 Pg C in 2000 to 86.771 Pg C in 2020. The soil carbon storage increased by approximately 34.850 Tg C a^-1 from 2000 to 2020. The land use transformation during the study period resulted in a decrease of approximately 17.621 Tg C a^-1 in soil carbon storage. The findings of this study can help researchers understand China's carbon storage and provide scientific data to China's 2060 Carbon Neutrality Target.

Construction land is the main carrier of human activities such as production and living. Conducting the suitability evaluation of construction land on the Qinghai-Tibet Plateau (QTP) holds the significant implications for harmonizing the relationship between ecological preservation and human activities, as well as promoting the optimization of population and industrial spatial layout. However, there are no relevant studies which provide a complete assessment of the construction land suitability (CLS) on the QTP. In this paper, we developed a model- based CLS assessment framework coupling of patterns and processes to calculate the CLS across the entire QTP based on the CLS evaluation model. Then, using the land-use data of 1990, 2000, 2010, and 2020, we examined the adaptability of existing construction land to the assessment result of CLS through the adaptability index and vertical gradient index, and further analyzed the internal limiting factors of maladaptive construction land. Finally, we calculated the potential of reserve suitable construction land. This article includes four conclusions: (1) The area of CLS classes, including highly suitable, suitable, moderately suitable, marginally suitable, and unsuitable, are 0.33×10⁴ km2, 10.42 ×10⁴ km2, 18.06×10⁴ km2, 24.12×10⁴ km2, and 205.29×10⁴ km2, respectively, accounting for 0.13%, 4.04%, 7.00%, 9.34%, and 79.50% of the total land area, respectively, with the unsuitable class being predominant. The highly suitable, suitable, and moderately suitable classes are mainly distributed in regions such as the Qaidam Basin, Yellow River-Huangshui River Valley, Gonghe Basin, Songpan Plateau, Shigatse Valley, Lhasa-Shannan Valley, and Nyingchi Valley. (2) The construction land adaptability index are 85.16%, 85.93%, 85.18%, and 78.01% in 1990, 2000, 2010, and 2020, respectively, with an average adaptability index exceeding 80% on the QTP. The distribution of existing construction land generally conforms to the characteristics of construction land suitable space, but with a significant spatial difference. (3) From 1990 to 2020, the mal-adaptive and low-adaptive construction land on the QTP is mainly composed of rural residential land, transportation land, and special land, the proportions of urban construction land and other construction land are rapidly increasing. The vertical gradient of elevation and slope of construction land have gradually strengthened, and the spatial extent has expanded. Construction land in the southern Qinghai Plateau, western Sichuan alpine canyon region, and Qilian Mountains is subjected to constraints of both elevation and slope, while the main limiting factor in the northern Tibetan Plateau, Gangdise Mountains, and Himalayan Mountains is elevation. (4) The potential area of reserve suitable construction land on the QTP is 12.41×10⁴ km2, constituting 4.81% of the total land area, with suitable and moderately suitable classes dominant. The per capita potential area of reserve suitable construction land is 9928 m²/person. The Qaidam Basin has the richest reserve of suitable construction land, while the Gonghe Basin and Lhasa-Shannan Valley can serve as preferred destinations for ecological migration. The research results can provide decision-making references for ecological migration and optimizing the spatial distribution of human activities on the QTP.

It is of great significance to systematically reveal the multi-scale evolution patterns and future trends of cultivated land landscape fragmentation (CLLF) in China since 1990 for optimizing the utilization and management of cultivated land resources and promoting appropriate scale agricultural management. This paper first discusses the theoretical cognition of CLLF, then systematically analyzes the evolution of multi-scale characteristics and scale nesting effect of CLLF at agricultural, provincial, municipal and county scales in China from 1990 to 2020, and predicts CLLF long-term evolution trend based on the data of China's land use in the study period and the spatial analysis and mathematical statistics methods such as Theil Index, scale variance, and Markov chain. Results showed that: (1) The pattern characteristics of CLLF in China show obvious scale differences, manifested as a ladder pattern along the three steps of China's terrain at the county scale, a cluster pattern of dual core, ring core group and belt area relying on the "Hu Huanyong Line" at the municipal scale, and a gradually strengthened concentric circular layered structure from east to west and from northeast to southwest at the provincial scale. The average contribution of differences in county, municipal, provincial and agricultural scales to the overall difference of CLLF in China is 84.87%, 14.64%, 0.31% and 0.18%, respectively, indicating that the smaller the scale, the better it can reflect the spatial heterogeneity of CLLF. (2) CLLF showed a trend of enhancement on multiple scales during 1990-2020, but the growth rate slowed down over time. Among them, the development of CLLF was the most intense during 2000-2010. (3) CLLF in China during 1990-2020 generally increased in the east and decreased in the west, but there were great differences in spatio-temporal evolution of the trend, intensity and spatial range at different scales. Spatially, major grain-producing areas such as the Huang-Huai-Hai Plain, the central and eastern parts of middle-lower Yangtze Plain and the Sichuan Basin became high-value agglomeration areas with increased fragmentation. (4) The long-term CLLF in China will follow the development pattern of a gradual increase from low to high. The counties with low- or relative low level of fragmentation will decrease greatly, while the counties with higher- or high-level will increase significantly. Meanwhile, different neighborhoods will also lead to significant differences in the long-term evolution of CLLF.