**1. Introduction**

Landscape patterns are the spatial characteristics and structural composition of landscape elements that determine the environment, distribution, and composition of resources [1]. Landscape patterns play a vital role in understanding the ecological processes of a region and in evaluating and optimizing ecological security [2,3]. For decades, a direct influence has been observed between the landscape pattern's evolution and the ecosystem [4], bringing significant changes to the quality of the landscape ecosystem and land use patterns of natural and anthropogenic activities [5,6]. Landscape ecological security is a subsystem of land resource security [7], which is crucial to national and regional development and construction. Landscape ecological safety has been a new issue facing human society's long-term development since 2001. The Southwest Karst Region, in the central part of the Guizhou Plateau, is the largest and most populous continuous karst ecologically vulnerable area in the world [8]. This region is a hotspot and a key area for global climate change research. It also serves as a scientific research paradigm in the world and enhances an understanding of the comprehensive governance of degraded ecosystems [9,10]. However, the non-agricultural population is increasingly being concentrated in the region owing to recent large-scale urbanization, the expansion of industrial and commercial space, rapid changes in urban land use, and the consequent evolution of landscape patterns. Thus, a change in the landscape pattern can improve the urban green landscape layout [11], since the landscape structure is gradually showing strong rapid urbanization [12,13]. Moreover, the anthropogenic pressure and the transformation of regional ecosystems are increasing. Unreasonable human activities are also causing serious ecological and environmental problems [14,15], making ecological security face great challenges [16,17]. Thus, adopting a

Academic Editor: Rui Alexandre Castanho

Received: 26 October 2022 Accepted: 4 December 2022 Published: 7 December 2022

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scientific and reasonable research method is critical in conducting an in-depth analysis of the ecological safety of the karst landscape.

Presently, ecological safety has become a research hot spot globally [18–24]. Studies have evaluated domestic and international landscape ecological safety, the ecological risk of the hotspot regional landscape, and the safety of urban clusters [25], coastal zones [26], and plateau mountains [27]. Ghosh et al. used the DEMATHE-ANP model to evaluate the ecological safety of the Kolkata Metropolitan Area in India [28]. Jiang et al. developed landscape classification on remote sensing (RS) images of the core region of Lijiang City and calculated the landscape pattern index as a driving factor [29]. From the perspectives of landscape patterns at the domestic and international levels, previous studies have established a solid conceptual base and methodological reference for exploring the evolutionary characteristics of regional landscape patterns and changes in ecological security patterns. Moreover, studies have explored landscape patterns and ecological security at a large scale, focusing on lakes [30], cultivated lands [31], and wetlands [32] in karst areas. Ren et al. used geographic information systems (GIS) and RS technology to analyze the spatial granularity effect of landscape patterns and identify the suitable spatial granularity of karst mountainous urban landscapes. However, these authors only explored a single landscape pattern index, which could not detect the regional ecological security status [33]. Liu et al. used the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) model to explore the spatial and temporal variation characteristics of habitat quality in the Chishui River Basin and its coupling relationship with the landscape pattern [34]. Wang et al. constructed a landscape security index using the ArcGIS software and a landscape pattern index to study the evolution of landscape patterns in trough valley areas. These authors also used this software to explore the spatial and temporal divergence patterns in ecological security [35]. Peng et al. used the landscape ecological security theory to develop an evaluation model and understand the ecological security of cultivated landscapes in the karst mountains. These authors also used this theory to understand the direction of ecological security transfer and driving factors of cultivated lands in the karst mountains [36]. However, most of these studies only based their investigation on short-term time series data, with a lag in data updating. Studies that used long time-series data to evaluate ecological safety are scanty. Furthermore, non-karst places have been the primary focus of research on patterns of landscape ecological safety at large-scale levels, such as regions, watersheds, and municipal territories. As a significant ecologically sensitive territory in China, Guizhou is also one of the most extensive karst landscapes in China, and overcoming its ecological and environmental problems is the key to solving earth system science, which can assist in the promotion of the construction of ecological civilization in China and even worldwide. The Nanming River basin is a tributary of the Wu River in the Yangtze River system, and more than 90% of the basin's total area is comprised of karst landscapes; it is a crucial ecological barrier in the upper reaches of the Yangtze River and an essential cornerstone of ecological civilization development. However, due to the relative fragility of the watershed ecosystem, it is vulnerable to the effects of urbanization. With the expansion of urbanization, high-density human activities, land development, water quality degradation, and other issues are altering the land use type, landscape pattern, and ecological mechanism of the watershed, posing a significant threat to the ecological security of the watershed landscape, and coordinating the relationship between ecological preservation and utilization in the study area is a significant issue at now. Therefore, to effectively sustain a well-functioning ecosystem in the study region in the future, a scientific evaluation of the evolution of the land use landscape pattern and its ecological safety is essential.

Based on 2000, 2010, and 2020 RS image data, this study used the theory of spatial autocorrelation, GIS spatial analysis, and landscape pattern index to elucidate the characteristics of spatial and temporal changes in land use in the watershed. The study also reveals the evolution in landscape pattern in the watershed since 2001, analyzes the spatial and temporal changes of ecological security, and makes a scientific evaluation and diagnosis of ecological security. It aims to realize quantitative analysis and visualization of the dynamic

evaluation of landscape patterns and ecological security in the study area from the spatial and temporal scales, disclose the evolution characteristics of the landscape pattern and the logic of ecological security pattern in the karst watershed under the human–land relationship, and provide scientific basis and advice for the sustainable development, proper development planning, scientific ecological planning and construction of the karst watershed. It also provides data references for maintaining ecological balance and optimizing land resource allocation and control in other karst areas of the same resource type in China as well as scientific and practical references for expanding international research on karst landscapes and ecological security.

#### **2. Materials and Methods**

#### *2.1. Study Area*

The Nanming River Basin is a tributary of the Wu River in the Yangtze River system. This Nanming River Basin is an important part of the Yangtze River Economic Belt, which is located at the social, economic, and cultural center of Guizhou Province of 26◦15 –26◦54 N and 106◦26 –107◦15 E. The watershed covers approximately 2158 km2, and it is characterized by a subtropical monsoonal humid climate with an annual mean precipitation of 1200 mm. Meanwhile, its topographic is high in the southwest and low in the northeast, with an average slope drop of approximately 3.44. The karst landscape in the watershed is extremely developed; its soil is dominated by rice soil, limestone soil, and loam. The karst landscape comprises 93.17% of the study area (Figure 1).

**Figure 1.** The basic information of the study area. Note: (**a**) shows location of Guizhou in China. (**b**) shows location of the study area in Guizhou. (**c**) shows the elevation of the study area. (**d**) shows the lithologic background.

#### *2.2. Methods and Data Sources*

2.2.1. Landscape Pattern Index Selection

The study combined previous studies that explored landscape characteristics of the basin [37–39], Patch Density (PD), and Patch Cohesion Index (COHESION) from the patch type level to reflect the degree of patch fragmentation in different landscape types. We also selected the Largest Patch Index (LPI) and Percentage of Landscape (PLAND) to identify dominant landscapes. The Patch Density (PD) and Contagion (CONTAG) were selected from the landscape level to reflect the degree of landscape fragmentation in the study area. Then, the Shannon Evenness Index (SHEI) and Shannon Diversity Index (SHDI) were selected to reflect the degree of landscape type diversification. The calculation formula and ecological significance of each index are detailed in the literature [40,41].
