1. Introduction
National parks are one of the most important types of protected area in China. China has been building a national park system since 2015 with the main aim of protecting the integrity and authenticity of the natural ecosystem. The first batch of parks, including 10 pilot national parks, was completed in 2020. Qianjiangyuan National Park, which focuses on the forest ecosystem, is one of the 10 existing pilots of the national park system in China and is in Zhejiang Province, one of China’s most economically developed provinces. With rapid urban and rural development, rates of habitat loss and fragmentation have increased [
1,
2]. In this context, connectivity between habitat patches is becoming even more important, as it may be the only way to provide adequate habitat for wildlife populations [
3].
Maintaining or restoring landscape connectivity is a widely recommended strategy for adapting to climate change, as species are changing their distributions to adapt to emerging conditions [
4]. Landscape connectivity refers to the degree to which the landscape facilitates or impedes movement among source patches [
5] and is one of the most critical components of animal dispersal, population persistence, and maintenance of ecological function [
6]. Landscape connectivity can be considered in terms of structural connectivity and functional connectivity, with the former referring to the apparent continuity that the landscape exhibits in space, which can be determined based on various types of maps, including satellite image maps, and the latter defining landscape continuity in terms of the characteristics of the ecological object or process under study [
7].
Based on existing species-based studies of landscape connectivity, it is generally accepted that landscape connectivity plays an important role in biodiversity [
8], which describes the role of the landscape in facilitating or hindering the dispersal of species between habitats [
9]. Species characterized by low dispersal distances are more sensitive to landscape connectivity, and the barrier effect of specific land cover is species-specific [
10]. Graph theory based approaches are widely used in different areas of landscape connectivity research, such as forests, protected areas, wildlife corridor design and ecological restoration [
11].
Landscape connectivity studies in national parks and protected areas have mainly focused on the connectivity of watersheds and marine protected areas in analyses of hydrological connectivity status [
12,
13,
14,
15]. Terrestrial protected area connectivity studies have assessed landscape structures, connectivity and corridors of specific species within limited areas [
16,
17]. However, most studies have focused on regional protected area networks or connectivity between adjacent protected areas [
18,
19,
20,
21,
22,
23]. China’s national parks are integrated from different types of protected areas and can be regarded as networks of protected areas on a smaller scale. Currently, the most commonly used methods for quantitative analysis of the connectivity of protected areas are the Least-cost model [
24], Circuit theory [
25], Graph theory [
26], the Resistant kernel model [
27], Reserve design [
28] and the Individual-based model [
29].
In this study, we identified core habitats and corridors based on the habitat and dispersal distances of particular species and assigned migration cost levels to the preferences of target species for different landscape types. We selected two species under national protection in China at the first level as habitat representatives of the species in the region, and the final core habitat and potential corridors were obtained by overlaying the two species. The aims of this study were to analyze the status of landscape connectivity in Qianjiangyuan National Park, to identify priority sites for ecological restoration and corridor construction to improve landscape connectivity in the study area, and to provide useful information for future national park planning and conservation management.
4. Discussion
Landscape fragmentation in Qianjiangyuan National Park occurs in the northern and southern edges where human disturbance is concentrated, and in the central part of the park. The disturbed landscapes in the southern and northern edges are dominated by tea plantations, while the central disturbed landscapes are dominated by drylands. Based on the distribution of key habitats, fragmentation and the distribution of corridors, the major roads in the central part of the national park are one of the main factors influencing the overall landscape connectivity in the region. Roads have also been highlighted in other relevant studies as major causes of landscape fragmentation and barriers to biological movement, resulting in reduced overall landscape connectivity for many native species [
32].
The strictly protected areas are appropriately zoned settings for habitat protection, whereas the recreational areas are almost all within non-key habitats, which is reasonable. However, approximately half of the traditional use areas are located in key habitats, especially near the lower outer edges of the park, and excessive human intervention during recreational activities should be avoided in these areas. The ecological conservation area is the most widely distributed area within Qianjiangyuan National Park, and most potential corridors are located in this area, which is highly protected by strict Chinese laws and regulations, which favor the restoration of potential corridor areas. There are a number of distinct potential corridors in the ecological conservation area that are important for improving the overall connectivity of the national park, and due to their location close to traditional use areas, i.e., human disturbances such as settlements and roads, it is also particularly important to consider enhancing conservation management in this area to elevate its conservation status [
46,
47]. Qianjiangyuan National Park has three separate strictly protected areas located in the northern and southern regions of the park, so connectivity between these strictly protected areas is dependent on successful protection of the conservation area, highlighting the importance of protecting potential corridors in the central part of the park.
Functional zoning is a commonly accepted approach to national park planning and management. Previously, functional zoning schemes for national parks and protected areas have been based on the current status of natural resource characteristics and species distribution or developed by considering the compatibility of land use and landscape features or planning, or established by adjusting functional zones from the perspective of multiple stakeholders [
48,
49,
50,
51,
52,
53]. Habitat connectivity is severely affected by types of human activities and infrastructure that are rarely considered. Few habitat corridor studies have been conducted to support the zoning design of national parks. However, relevant studies have shown that interconnected habitat areas are critical for biodiversity conservation, especially in the face of climate change [
54]. Therefore, it is important to consider habitat corridors in zoning design and as parts of functional zones. Noss and Harris proposed a conceptual model of core areas connected by corridors as a means of long-term conservation of protected area species, and their model can also be applied to zoning within protected areas [
55]. Compared with the current functional zoning method of national parks which only considers the distribution of natural resources, this study provides support for the zoning design of national parks based on landscape connectivity and corridor design, which can improve the conservation efficiency of national parks.
5. Conclusions
This study analyzed landscape fragmentation in Qianjiangyuan National Park and identified key habitats and important corridors. We found that:
- (1)
Roads, settlements, and cultivated land have a significant impact on the landscape connectivity of Qianjiangyuan National Park, with roads being one of the main reasons for the fragmentation of the overall landscape. We recommend that several potential corridors in the center of the park that connect key habitats on both sides of the road be protected to help link habitat patches, mitigate the impact of the road, and appropriate vegetation restoration and reforestation of tea plantations and drylands in the study area will increase the landscape connectivity of Qianjiangyuan National Park.
- (2)
The area of each patch of key habitat is not proportional to its contribution to the landscape connectivity of Qianjiangyuan National Park, but the size of key habitats is important for maintaining landscape connectivity. At the landscape scale, large habitat patches of high importance should be prioritized for protection to promote habitat connectivity and species conservation in the study area. At the same time, groups of small patches with a high potential for species migration should also be protected as a whole to avoid further fragmentation or even area loss.
- (3)
The locations and boundaries of strict protected areas and recreational areas of Qianjiangyuan National Park are relatively reasonable, and the scope of ecological conservation areas and traditional use areas could be adjusted to better match the distribution of key habitats. Special attention must be focused on protecting and managing ecological conservation areas because of the pressure of human disturbance around the area. However, at the same time, there are several important corridors in the area, and the connectivity between strictly protected areas depends on successful protection of ecological conservation areas.
Using high-resolution remote sensing image data, the landscape connectivity of different types of connected protected landscapes was analyzed as an integrated mosaic at the scale of an individual national park. In comparison with the more commonly used method of functional zoning of national parks, in which only the distribution of natural resources is considered, this study used detailed habitat characteristics to grade resistance and analyze landscape connectivity and corridors to support the zoning design of national parks. This method can improve the conservation effectiveness of national parks by ensuring that ecological connections are maintained and strengthened where they exist and restored where they are lost.
While this study used two detailed habitat selections in the habitat corridor analysis and graded the resistance produced by different species based on landscape categories, it did not consider the region’s plant migration characteristics, the connectivity of aquatic organisms in the forest ecosystem, or the migration characteristics of the region’s less studied and less data-accessible species, such as insects, amphibians, reptiles, etc. In addition, this study only analyzed and optimized connectivity recommendations within the study area, and further ecosystem integrity and connectivity analyses can be conducted in conjunction with surrounding potential habitat patches to make useful recommendations for range optimization in Qianjiangyuan National Park. The current study assumes that highways, railroads, and national roads have a segmentation effect on habitats for connectivity analysis, but the form of road construction varies in different regions of China, especially in mountainous areas, where bridges and tunnels are more common, and the extent of impact on habitats is not clear, so the calculations in this study may underestimate the connectivity in some areas. It would be useful to analyze the impacts of different road types on the park ecosystem in future research.