Comprehending the dynamic change characteristics of land use/cover and the driving factors causing the change are prerequisites for protecting land resources. This paper analyzes changes in cultivated land, the driving factors that cause them, and their tremendous impact on landscape pattern changes in the Dongting Lake Basin. For this purpose, we used mathematical statistics, buffer analysis, trend analysis, landscape pattern index, and logistic regression model to analyze the land use data of the study area from 1980 to 2018. The results show that the cultivated land showed a decreasing trend, with the total area decreased by 4.76% (or 716.13 km²) from 1980 to 2018, and the activity of mutual transformation with other land use types decreased. The spatial distribution pattern of cultivated land and landscape shows the change characteristics gradually from Dongting Lake to the surroundings. Among the driving factors of cultivated land changes, the influence of human activities was gradually increasing, while the natural factors were decreasing. The cultivated land landscape pattern index and the overall landscape pattern index have a significant positive correlation, showing relatively consistent change trend and spatial distribution characteristics. We believe that the decrease of cultivated land area has a certain relationship with the increase of landscape fragmentation in the Dongting Lake Basin. Our research is expected to provide a reference for strengthening regional cultivated land management and rational development and utilization of regional land resources.

Ecosystem water use efficiency (WUE) plays an important role in maintaining the carbon assimilation–water transpiration balance in ecosystems. However, spatiotemporal changes in WUE in the subtropical region of China (STC) and the impact of driving forces remain unclear. In this study, we analyzed the spatiotemporal variation in WUE in the STC and used ridge regression combined with path analysis to identify direct and indirect effects of climate change, vegetation growth, and elevated atmospheric CO₂ concentration (Ca) on the interannual trend in WUE. We then quantified the actual and relative contributions of these drivers to WUE change based on the sensitivity of these variables on WUE and the trends of the variables themselves. Results reveal a mean WUE of 1.57 g C/m²/mm in the STC. The annual WUE series showed a descending trend with a decline rate of 0.0006 g C/m²/mm/year. The annual average temperature (MAT) and leaf area index (LAI) had strong positive direct effects on the WUE, while the vapor pressure deficit (VPD) had a strong negative direct effect. Opposite direct and indirect effects offset each other, but overall there was a total positive effect of Ca and VPD on WUE. In terms of actual contribution, LAI, Ca, and VPD were the main driving factors; LAI caused WUE to increase by 0.0026 g C/m²/mm/year, while Ca and VPD caused WUE to decrease by 0.0021 and 0.0012 g C/m²/mm/year, respectively. In terms of relative contribution, LAI dominated the WUE trend, although Ca and VPD were also important factors. Other drivers contributed less to the WUE trend. The results of this study have implications for ecological management and restoration under environmental climate change conditions in subtropical regions worldwide.

Shape similarity measurement model is often used to solve shape-matching problems in geospatial data matching. It is widely used in geospatial data integration, conflation, updating and quality assessment. Many shape similarity measurements apply only to simple polygons. However, areal entities can be represented either by simple polygons, holed polygons or multipolygons in geospatial data. This paper proposes a new shape similarity measurement model that can be used for all kinds of polygons. In this method, convex hulls of polygons are used to extract boundary features of entities and local moment invariants are calculated to extract overall shape features of entities. Combined with convex hull and local moment invariants, polygons can be represented by convex hull moment invariant curves. Then, a shape descriptor is obtained by applying fast Fourier transform to convex hull moment invariant curves, and shape similarity between areal entities is measured by the shape descriptor. Through similarity measurement experiments of different lakes in multiple representations and matching experiments between two urban area datasets, results showed that the method could distinguish areal entities even if they are represented by different kinds of polygons.

The karst area in northwestern Guangxi is poor, underdeveloped, and ecologically fragile. It is experiencing rocky desertification, which creates challenges that are more severe than those of other regional ecological environments. In this paper, the ecological footprint (EF) model is used to analyze the ecological carrying capacity (EC) in northwestern Guangxi from 1995 to 2015, and the differences in karst counties with different poverty levels are discussed. The results show that (1) since 1995, the EC of northwestern Guangxi has continued to decrease, the EF has continued to increase, the ecological deficit (ED) has been expanding, and the status of the region has been unsustainable for a long time. (2) The evolutionary patterns, EF and EC of karst counties with different poverty levels are different. The county with the lowest poverty rate has the fastest growth rate of the per capita EF. The county with the largest proportion of karst area has the lowest EC. (3) It is recommended that different types of counties take different measures, including strengthening ecological environment protection, carrying out rocky desertification control and ecological resettlement projects, and reducing energy consumption. This study can provide information for the sustainable development of the karst region and provide decision support for regional poverty alleviation.

Urbanization and global climate change are two important global environmental phenomena in the 21st century. Human activities and climate changes usually increase the uncertainties of the ecosystem functions and structures and can greatly affect regional landscape patterns and the carbon cycle. Consequently, it is critical to understand how various climate and land-use changes influence the carbon dynamics at a regional scale. In this study, we quantitatively analyzed the spatial and temporal changes of net primary productivity (NPP) and the effects of climate factors and human disturbance factors (i.e., land-use changes) on the “Chang–Zhu–Tan” (CZT) urban agglomeration region from 2000 to 2015. The Carnegie–Ames–Stanford Approach (CASA) model was combined with spatially explicit land-use maps, monthly climate data, and MODIS NDVI images to simulate the carbon dynamics in the CZT area. Based on our six different scenarios, we also analyzed the relative roles of climate change and land-use change in total production. Our results indicated that the annual NPP of the study area maintained an upward trend by 7.31 gC•m⁻²•yr⁻¹ between 2000 and 2015. At the same time, the average annual NPP was 628.99 gC•m⁻² in the CZT area. We also found that the NPP was lower in the middle of the north region than in others. In addition, land-use changes could contribute to a positive effect on the total production in the study area by 3.42 T gC. Meanwhile, the effect of climate changes on the total production amounted to −1.44 T gC in the same region and period. Temperature and precipitation had negative effects on carbon sequestration from 2000 to 2015. As forest land constituted over 62.60% of the total land use from 2000 to 2015, the negative effect of carbon sequestration caused by urbanization could be ignored in the CZT area. Although climate and land-use changes had simultaneously positive and negative effects during the period 2000–2015, prioritizing the protection of existing forest land could contribute to increasing carbon sequestration and storage at the regional scale. Our study assists in understanding the impact of climate changes and land-use changes on carbon sequestration while providing a scientific basis for the rational and effective protection of the ecological environment in mid-east Hunan Province, China.

With the rapid development of the social economy, human dependence on and interference with cultivated land ecosystems have increased. Improving the understanding of changes in ecosystem services is conducive to avoiding and reducing the risk of ecosystem service degradation. This study evaluated seven key ecosystem services of cultivated land in the Dongting Lake Plain from 2000 to 2020, analysed their spatiotemporal evolution characteristics and correlations between ecosystem service pairs, and identified the key factors driving their changes. Finally, the PLUS model was used to predict land use changes and ecosystem service responses under the baseline scenario, farmland protection scenario, and ecological protection scenario in 2040. The results revealed that (1) from 2000 to 2020, in addition to the degradation of carbon storage services and habitat quality services, the food production, environmental purification, water conservation, soil conservation and landscape aesthetic services of the Dongting Lake Plain all showed increasing trends. The high- and low-value areas of each ecosystem service vary, but the overall spatial pattern is relatively stable. (2) In 2000, 2010 and 2020, the proportions of trade-off relationships among the 21 ecosystem service pairs in the Dongting Lake Plain were 52.38%, 51.74% and 28.57%, respectively. During the study period, the dominant correlation between ecosystem services shifted from trade-offs to synergies. (3) Ecosystem services are influenced by both natural background conditions and human activities. Natural factors have a greater impact than do socioeconomic factors. Precipitation, temperature and altitude are the key factors driving changes in ecosystem services. (4) The simulation results of multiple scenarios reveal that by 2040, the cultivated land in the Dongting Lake Plain will suffer the greatest loss under the baseline scenario, with the percentage decreasing from 54.07% to 51.64%. In addition to the improvement of environmental purification services, the total amount of various services will also increase. The reduction is the most significant in this scenario, followed by the ecological protection scenario. In the farmland protection scenario, ecosystem services are protected to a certain extent.