The response of ecological security to land use change in east and west subtropical China.

Regional land use change and ecological security have received considerable attention in recent years. The rapid economic development of Kunming and Fuzhou has resulted in environmental damage such as water pollution and urban heat island effect. It is thus important to conduct a comparative analysis of the ecological security response to land use/land cover change (LUCC) in different natural zones. Using the Google Earth Engine (GEE) platform, random forest and support vector machine methods were used to classify land cover types in the study area, after which the ArcGIS platform was used to analyze LUCC. The driving force-pressure-state-impact-response (DPSIR) model and entropy weight method were used to construct an ecological security evaluation system, and gray correlation was used to compare the ecological security responses to LUCC in Kunming and Fuzhou. The findings revealed that: (1) The average dynamic degrees of comprehensive land use in Kunming and Fuzhou from 1995 to 2020 were 1.05% and 0.55%, respectively; (2) From 1995 to 2020, the ecological security index values for Kunming and Fuzhou increased from 0.42 to 0.52 and from 0.36 to 0.68, respectively, indicating that Fuzhou's index is rising more rapidly; and (3)There is a strong correlation between LUCC and ecological security, the correlation between the woodland and the ecological security index is very strong in both places. The expansion of construction land may be an important reason for the reduced ecological security level in Fuzhou City, while water resources have a significant impact on the ecological security level of Kunming City.

Ecological security assessment at different spatial scales in central Yunnan Province, China.

Healthy ecosystems are the basis of social and economic development. It is of great significance to conduct ecological security assessments in rapidly urbanization areas. Based on the driving forces, pressure, state, impact, and response (DPSIR) model, five years (1995, 2000, 2005, 2010 and 2015) of remote sensing images, social and economic statistics, and field survey data were used to establish an ecological security assessment index system. The ecological security assessment of central Yunnan Province (CYP) urban agglomeration was conducted at the 1 km × 1 km pixel scale and at the county scale based on the multilevel weighted comprehensive index method. The results showed that: (1) With 2005 as the turning point, the ecological security situation in CYP first decreased and then increased. (2) The ecological security at the county scale was mainly categorized as unsafe. At the pixel scale, ecologically unsafe and relatively unsafe areas were mainly distributed in central, northern, and western CYP. (3) The ecological security deterioration and strengthened spatial distribution differences were caused by habitat fragmentation, different physical geographical conditions, and population agglomeration. These results can provide a basis for the coordination and sustainability of economic development and environmental protection in urban agglomerations with rapid urbanization.

Spatial Distribution of Soil Heavy Metals and Associated Environmental Risks near Major Roads in Southern Tibet, China.

Soil heavy metal pollution is becoming an increasingly serious environmental problem. This study was performed to investigate the contents of surface soil heavy metals (Cu, Zn, Pb, Cd) near six roads in the southern part of the Tibetan Plateau. Multivariate statistics, geoaccumulation index, potential ecological risk, and a human health assessment model were used to study the spatial pollution pattern and identify the main pollutants and regions of concern. The mean Igeo was ranked in the order Cd > Cu > Zn > Pb, with the average concentrations of Cd, Zn, and Cu exceeding their corresponding background levels 4.36-, 1.00-, and 1.8-fold, respectively. Soil Cd level was classified as posing a considerable potential risk near national highways and a high potential risk near non-national highways, whereas soil Cu, Zn, and Pb were associated with a low potential ecological risk for each class of roads. Furthermore, the non-carcinogenic risk due to soil heavy metals for each class of roads was within the acceptable risk level for three exposure pathways for both adults and children, but the carcinogenic risk attributable to soil Pb exceeded the threshold for children near highways G318, G562, and G219 and for adults near highway G318. Our work not only underscores the importance of assessing potential threats to ecological and human health due to soil heavy metal pollution on road surfaces but also provides quantitative guidance for remediation actions.

[Influence of landscape pattern on elevation effect of δ18O in surface water in Hani Terrace]. / å“ˆå°¼æ¢¯ç”°æ™¯è§‚æ ¼å±€å¯¹åœ°è¡¨æ°´Î´18O海拔效应的影响.

With the Quanfuzhuang River basin located at Hani Rice Terrace core region as study area, we analyzed the isotopic composition and the effects of 12 surface water sampling sites for the forest landscape type and terrace landscape type from May 2015 to April 2016. The results showed that: 1) For the variation of isotope composition, both the average value and the variation range of δ18O in surface water under forest patches were smaller than that under terrace patches. 2) The overall elevation effect of the hydrogen and oxygen stable isotopes in surface water was obvious, except that in August and March, which could be expressed as the linear regression equation δ18O=-0.012H+13.84 (r=-0.83, n=12). 3) The altitude gradient of δ18O in surface water was -1.2‰·(100 m)-1, which was not the true altitude gradient affected by precipitation but by landscape gradient of δ18O in surface water between forest patches and terrace patches. 4) Under the "Forest-Terrace" landscape pattern, the δ18O differences in surface water between forest patches and terrace patches enhanced the elevation effect. Therefore, when landscape heterogeneity was strong, isotopic effect was strengthened, even with opposite isotope effect.

Impacts of moisture sources on the isotopic inverse altitude effect and amount of precipitation in the Hani Rice Terraces region of the Ailao Mountains.

Generally, the isotopic composition of precipitation on the windward side of gigantic mountains has a negative altitude gradient. However, an inverse isotopic altitude effect occurs when there are diverse vapor sources. This paper takes the Quanfuzhuang River Basin (QRB), which lies in the Hani Rice Terraces region of the southern Ailao Mountains in southwest China, as the study area. The study analyzes the isotopic data of 42 precipitation samples collected between an elevation range from 1500 m to 2024 m a.s.l. during the rainy season (from May to October) of 2015. The results indicate that there is an inverse isotopic altitude effect of precipitation with a positive isotope altitude gradient of 0.47‰/100 m and 1.10‰/100 m for δ18O and δ2H, respectively, at the mountaintop, while the precipitation amount increases at related elevations. A mixture of over peak airflow and recycled vapor is responsible for the inverse altitude effect as well as increasing rainfall amount. The positive precipitation isotopic altitude gradient is primarily caused by the local water cycle, and the increased precipitation amount is mainly caused by over peak airflow. The inverse isotopic altitude effect is also found in the Colorado Rocky Mountains, the Central Hindu Kush Mountains and the Tianshan Mountains, and findings from those mountains support these findings on the influence of mixed moisture sources on isotopic inverse altitude effects.

[Spatial neighboring characteristics among patch types in oasis and its ecological security].

In this paper, the spatial neighboring length and number between oasis types and desert or salina-marsh in the Jinta Oasis located in the arid Heihe River Basin of Northwest China were calculated by using ArcView3.0a and buffer zone analysis methods, and the threatening degree of oasis ecological security was discussed. The results indicated that it was different in neighboring length and number between oasis types and desert or salina-marsh, and the influencing area by desert and salina-marsh patches was also different. Grassland and farmland had more neighboring length and numbers with desert or salina-marsh patches, and impacted by desertification seriously. Forest and farmland had more length and numbers adjacent to salina-marsh, and influenced by salinization severely. The assessment of ecological security based on spatial analysis could reveal the threatening degree of oasis by desertification and salinization.