Abstract:

Habitat quality is a crucial indicator of biodiversity and ecosystem services within a region. Exploring spatiotemporal characteristics of habitat quality in the context of high-quality ecological conservation and restoration is important for developing targeted ecological protection policies. With the widespread adoption of 3S technologies, habitat quality research is increasingly shifting towards more refined and quantitative analyses, particularly in the study of the spatiotemporal characteristics of habitat quality. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model has become the preferred tool in the field of habitat quality assessment, owing to its ease of data acquisition and cost-effectiveness. Current research primarily focuses on administrative units, such as provinces, cities, and urban clusters, with less attention given to natural units, such as watersheds and protected areas. Comprehensive studies that consider both administrative and natural units are rare. Integrating studies of administrative and natural units not only provides a more comprehensive perspective for researchers and policymakers but also helps in understanding environmental issues more deeply and formulating more targeted and effective management strategies. Chongqing’s One Belt and Three Barriers encompass both administrative and natural attributes and cover the ecological planning areas of the Daba, Wuling, Dalou, and Upper Yangtze River ecological conservation belts. By conducting a study on the spatiotemporal characteristics of habitat quality in Chongqing’s One Belt and Three Barriers compared to traditional studies focused on singular administrative or natural divisions, this study further revealed the relationships and differences between Chongqing's administrative divisions and the natural units of the One Belt and Three Barriers. This approach provides more targeted data and a decision-making basis for ecological conservation and restoration in Chongqing. This study utilized land use data from 2000 to 2020, employing mode-filtering methods to improve the stability and consistency of the data, and assessed the habitat quality of the study area using the habitat quality module of the InVEST model. Additionally, ENVI software was used to conduct spatial autocorrelation analysis at the pixel scale, including the global Moran's I index and Getis-Ord Gi* hotspot analysis, to explore the spatial distribution characteristics of habitat quality. This study provides a comprehensive perspective on the dynamics of regional habitat quality in both the administrative and natural units. The results showed that 1) the primary land uses in Chongqing City are forest and cultivated land, accounting for over 90% of the total area, whereas shrubland, grassland, water bodies, impervious surfaces, and unused land constitute less than 10%. Between 2000 and 2020, cultivated land significantly decreased, with 6.25×10³ km² converted into forest. 2) Significant differences existed in land use types among the different areas. The Upper Yangtze River ecological conservation zone is predominantly characterized by cultivated land, whereas the ecological barriers of the Daba and Wuling Mountains are primarily forested. The Dalou Mountains ecological barrier has an equal proportion of cultivated land and forest. Apart from the Dalou Mountains barrier, other areas saw a decrease in cultivated land and increase in forested land. The most significant increases in impervious surfaces and water bodies were both in the Upper Yangtze River conservation zone, with a notable increase in impervious surfaces in the Dalou mountain barrier. 3) The average habitat quality index for the study area over the years was 0.473, with significant differences in spatial distribution. The northeastern and southeastern parts of the region, which are characterized by mountainous terrain and extensive forest cover with minimal human disturbance, have a relatively high habitat quality. In contrast, the western region, owing to agricultural activities and urban expansion, exhibited lower habitat quality. Overall, from 2000 to 2020, low-grade habitat quality increased with the acceleration of urbanization, mid-grade quality increased annually with ecological restoration projects, and high-grade quality remained relatively unchanged, indicating a general improvement in habitat quality. 4) For each ecological planning area within the One Belt and Three Barriers, significant spatiotemporal differences in habitat quality were observed. The Daba Mountains ecological barrier maintained the highest habitat quality owing to its favorable natural conditions and effective protection measures, followed by the Wuling Mountains ecological barrier, which, despite its sound ecological foundation, was affected by recreational tourism. The habitat quality in the Dalou Mountains ecological barrier and the Upper Yangtze River ecological conservation zone was relatively low, mainly influenced by agricultural activities and urbanization. In the Upper Yangtze River ecological conservation zone, despite improvements, habitat quality has remained relatively low under the pressures of rapid economic development and urban expansion. 5) From 2000 to 2020, Moran’s I index indicated that the global spatial autocorrelation of habitat quality gradually increased from 0.893 to 0.899, suggesting a strengthening spatial clustering effect where regions of high or low habitat quality tend to aggregate. 6) The spatial distribution of habitat quality hotspots showed that they were primarily located in areas with favorable ecological conditions and minimal human disturbance, such as the Daba and Wuling Mountain ecological barriers. The sustained hotspot status of these areas reflects the effectiveness of the local ecological protection policies. Conversely, habitat quality coldspots were mainly found in areas with intense human activity and higher urbanization levels, such as the northern part of the Dalou Mountains ecological barrier and the Upper Yangtze River ecological conservation zone. 7) Hotspot analysis of habitat quality changes showed that the significance area of hotspots and coldspots increased over time, while the area of non-significant hotspots gradually decreased. This change reflects the polarization and clustering trends between ecological protection and environmental degradation, where environmental measures, such as the Grain for Green policy, have significantly improved habitat quality in some areas, whereas urbanization and infrastructure development have pressured others. This study provides important scientific data support and a decision-making basis for ecological conservation and restoration efforts in Chongqing City and offers a reference for habitat quality assessment in similar regions. In future policymaking, it is essential to consider the differentiated characteristics of various ecological regions and adopt targeted protection and restoration measures for hotspots and coldspots. For instance, in the Daba and Wuling Mountains ecological barriers, forest protection measures should be strengthened to prevent excessive disturbances from tourism development, whereas in the Upper Yangtze River ecological conservation zone and Dalou Mountains ecological barrier, habitat quality could be improved by limiting intensive agricultural practices and the expansion of impervious surfaces. In addition, enhancing the accuracy of land use data and adjusting the parameters of the InVEST model will improve the reliability and applicability of habitat quality assessments.

Key words: One Belt and Three Barriers, habitat quality, Chongqing City, InVEST model, ecological barrier, ecological conservation zone

摘要：

生境质量是反映区域生物多样性和生态系统服务水平的重要指标。在加强生态保护和修复的高质量发展背景下，探究区域生境质量的时空演变特征对于制定针对性的生态保护政策具有重要意义。以重庆市“一带三屏”为研究区，使用众数滤波处理土地利用数据以提高其可靠性，基于InVEST模型计算生境质量并在像元尺度上进行空间自相关分析，从行政和自然单元视角探究了2000－2020年研究区的生境质量时空演变特征。结果表明，1）重庆市土地利用以林地和耕地为主，期间耕地大幅减少，大部分转换为林地。2）多年平均生境质量指数为0.473，在空间分布上呈东北和东南高、西部低的格局，近20年总体呈上升趋势。3）大巴山区生态屏障多年平均生境质量指数最高（0.635）;武陵山区（0.557）和大娄山区生态屏障（0.477）次之，其趋势有所下降;长江上游生态保护带最低（0.406），但总体趋势向好。4）生境质量热点区主要集中在大巴山区和武陵山区生态屏障，冷点区位于长江上游生态保护带和大娄山区生态屏障北部;生境质量变化量的显著性热点和冷点面积均呈增加趋势，反映了生态保护与环境破坏的两极分化。研究结果可为研究区的生态保护和修复工作提供数据支持和决策依据。

关键词: 一带三屏, 生境质量, 重庆市, InVEST模型, 生态屏障, 生态保护带