Landscape Ecological Integrity Assessment to Improve Protected Area Management of Forest Ecosystem

Abstract

Understanding the ecological integrity of a protected area is a central topic for the management and conservation of these key areas. An ecological integrity framework based on a series of landscape ecology indices was developed to monitor and evaluate the status and conditions of ecological integrity among different functional zones in the Xiangjiangyuan Provincial Nature Reserve. The results showed that this nature reserve has high ecological quality and low anthropogenic influence, with the ecosystem generally well-maintained. The important landscape types of this nature reserve include evergreen broad-leaved forests, mixed evergreen deciduous broad-leaved forests, deciduous broad-leaved forests, etc., which have high authenticity and high conservation values. As the results for the degree of landscape fragmentation and human interference in the three functional zones showed the core zone < the buffer zone < the experimental zone, which was good to fit the conservation and management requirements of the nature reserve. The landscape fragmentation analysis for the important landscape types in all functional zones showed that the experimental zone and the buffer zone were relatively more severe than the core zone; the core area was lighter with minimal anthropogenic impacts and the most complete protection of the nature reserve. Regarding the sustainability and management goals, we suggest some effective policies to continuously improve the ecosystem integrity.

1. Introduction

Protected areas are considered as the core basis for biodiversity conservation and are classified as the primary status in maintaining regional ecological security [1,2]. Nature reserves act as key members of the natural protected area system, and the most effective measures of biodiversity conservation in China [3]. Mountains are unusually biodiverse, play an array of roles for regional biodiversity, and act as species pools to adjacent lowlands [4]. Mountains cover 78% of areas of particular importance for biodiversity or 83% of areas of importance for biodiversity in China [5,6]. Therefore, evaluating the ecological integrity of a nature reserve in mountain regions can help to understand the regional ecological quality, clarify the zonal management strategy, and maximize the benefits of regional ecological security.

Ecological integrity refers to the state of ecosystems and is explicitly or implicitly measured according to resilience, robustness, stability, and sustainability, which is a major concern for humanity [7,8]. Hence, integrity means that an ecosystem possesses all of the indigenous biodiversity and ecological processes that should be contained in the natural habitat of a region and maintains its structure and function without damage [9,10]. Maintaining the nature reserves’ ecological integrity and originality plays an important role in protecting regional biodiversity and stabilizing ecosystem functions [11,12]. In the meantime, the state of the ecological integrity of nature reserves is the background and best state of the regional ecosystem, so this type of evaluation for nature reserves is extremely urgent and important.

Currently, an evaluation of ecological integrity includes various indicators from the ecosystem structure, function, and process such as species diversity, habitat fragmentation, ecosystem services, etc. [13]. For a montane nature reserve, where the constant mainstay is the forest ecosystem, so the ecological integrity could be judged through the landscape pattern index, as indicators have been a major trend in recent years [12,13,14]. Landscape ecology provides an effective method to analyze the integrity and originality of forest ecosystems by quantitatively analyzing the spatial distribution characteristics and revealing the links between the spatial patterns and ecological processes of landscape components [7,13,15]. Parrish et al. (2003) further described the ecological integrity in landscapes as the ability of an ecosystem to support and maintain a biotic community with a species composition comparable to those of natural habitats, diversity, and functional organization [16]. Hence, regional ecological integrity is an ecosystem with natural evolutionary and ecological processes that are minimally or unaffected by human activities [17]. The landscape pattern framework has significant spatial and temporal characteristics, which is conducive to the dynamic evaluation and monitoring of ecosystem integrity, construction, and optimization of ecological networks and ecological protection spaces [7].

The Xiangjiangyuan Provincial Nature Reserve is a protected area approved by the Jiangxi Provincial Government in 2017, which is located at the intersection of the Wuyi Mountains and Nanling Range as the key node of the nature reserve network in the mountains in eastern China [18]. The protected targets of this nature reserve contain evergreen broad-leaved forests and wildlife such as Neofelis nebulosa, Syrmaticus ellioti, etc. Based on the seventh national forest inventory datasets, we explored the landscape structure of each functional zone and analyzed the ecological integrity of the nature reserve. The aims of the study were to (1) investigate the landscape composition and diversity in every functional zone; (2) identify the dominant landscape types in each functional zone; and (3) analyze the ecological integrity of this nature reserve based on the landscape characteristics. Our hypothesis posits that there are discernible differences in ecological integrity among the functional zones. We anticipate that the naturalness and landscape pattern are pivotal factors that influence the ecosystem integrity. The study will provide valuable scientific insights for nature reserve management for the protected area network in the Wuyi Mountains and Nanling Range.

2. Materials and Methods

2.1. Study Area

The Xiangjiangyuan Provincial Nature Reserve (XPNR) is located in Huichang County, Ganzhou City, Jiangxi Province (115°48′22″–116°02′00″ E, and the latitude of 25°29′00″–25°36′03″ N) (Figure 1). It is 23 km long from east to west and 13 km wide from north to south, with a total area of 10,341.39 hm². The protected area has a humid climate in the central subtropical monsoon, with a mild climate, sufficient heat, long sunshine hours, abundant light energy, high precipitation, no droughts or floods, and a large difference in the four distinct seasons. The lowest temperature in the reserve is in January, with an average temperature of 8.8 °C; the highest temperature is in July, with an average temperature of 28.7 °C; and the perennial temperature fluctuates around 19.4 °C. There are 215 families, 831 genera, and 2276 species of vascular plants in the nature reserve. Zoological geography belongs to the East Hilly Plain subregion of the Sino-Japanese realms [19,20], with 383 species in 35 orders belonging to 104 families. The forest ecosystem in the reserve is relatively intact, with more than 90% forest coverage, and the development of broad-leaved evergreen forests with the characteristics of the southern part of the middle subtropics.

2.2. Data Collection

The functional zone shapefile of the nature reserve was provided by the Huichang County Xiangjiangyuan Provincial Natural Reserve Administration Committee, and the vector data were approved by the Jiangxi Provincial Government in 2017. The second level forest resource datasets of the seventh national forest survey from 2017 to 2019 were collected to assess the landscape ecological integrity.

2.3. Landscape Ecological Integrity Calculation and Evaluation

The landscape type of patch was identified through dominant plants included in the database. A total of 12 landscapes types were distinguished (Figure 2): evergreen broad-leaved forests, mixed evergreen deciduous broad-leaved forests, deciduous broad-leaved forests, natural coniferous forests, mixed coniferous broad-leaved forests, bamboo forests, planted coniferous forests, shrublands, grasslands, navel orange plantations, oil-seed camellia plantations, and tea plantations.

Landscape patches were grouped according to Põldveer et al. (2023), with the grouping methodology falling into the naturalness classes in

Table 1. The simple classification with three categories of landscape naturalness.

Naturalness Level	Description
Natural patch	Not disturbed by humans or their animals.
Recovering patch	The vegetation may have been established by human activities or naturally regenerated and have signs of past management.
Managed patch	Artificial systems such as planted land; the vegetation has been deliberately determined by humans, with loss of the previous habitat.

[21]. A total of 492 patches were grouped under study.

Several landscape pattern indices were used to evaluate the ecological integrity of the nature reserve and the three functional zones. The patch density (PD) and mean patch size (MPS) were used to measure the landscape fragmentation of the nature reserve according to Equations (1) and (2). In landscape ecology, the PD indicates the stability of the landscape pattern, while the MPS indicates the heterogeneity of the landscape [22].

$$\mathrm{P}\mathrm{D}={\displaystyle \frac{\mathrm{N}}{\mathrm{A}}}$$

(1)

$$\mathrm{M}\mathrm{P}\mathrm{S}={\displaystyle \frac{\mathrm{A}}{\mathrm{N}}}\times 10^{-6}$$

(2)

where N is the number of patches, and A is the total area of landscape types.

The largest patch index (LPI) refers to a simple measure of dominance, as follows [23]:

$$\mathrm{L}\mathrm{P}\mathrm{I}={\displaystyle \frac{\max \left({\mathrm{a}}_{\mathrm{i}\mathrm{j}}\right)}{\mathrm{A}}}\times 100\%$$

(3)

where a_ij is the area of patch j in landscape type i.

The mean shape index (MSI) and area-weighted mean patch fractal dimension (AWMFD) describe the shape complexity of the landscape. These two metrics reflect the extent to which human activities affect natural landscapes [24].

$$\mathrm{M}\mathrm{S}\mathrm{I}={\displaystyle \frac{\sum _{\mathrm{i}=1}^{\mathrm{m}}\sum _{\mathrm{j}=1}^{\mathrm{n}}\frac{{\mathrm{p}}_{\mathrm{i}\mathrm{j}}}{\min {\mathrm{p}}_{\mathrm{i}\mathrm{j}}}}{\mathrm{N}}}$$

(4)

$$\mathrm{A}\mathrm{W}\mathrm{M}\mathrm{P}\mathrm{F}\mathrm{D}=\sum _{\mathrm{i}=1}^{\mathrm{m}}\sum _{\mathrm{j}=1}^{\mathrm{n}}\left[{\displaystyle \frac{2\ln \left(0.25{\mathrm{p}}_{\mathrm{i}\mathrm{j}}\right)}{{\ln \mathrm{a}}_{\mathrm{i}\mathrm{j}}}}\left({\displaystyle \frac{{\mathrm{a}}_{\mathrm{i}\mathrm{j}}}{\mathrm{A}}}\right)\right]$$

(5)

where m is the number of landscape patch types, n is the number of all patches in the landscape, and p_ij is the perimeter of patch j in landscape type i.

The contagion index (CONTAG) is an aggregation metric that describes the connectivity of landscape types and granularity of the landscape texture by measuring the extent to which landscape types are clumped together [25].

$$\mathrm{C}\mathrm{O}\mathrm{N}\mathrm{T}\mathrm{A}\mathrm{G}=\left[1+\sum _{\mathrm{i}=1}^{\mathrm{m}}\sum _{\mathrm{j}=1}^{\mathrm{n}}{\displaystyle \frac{{\mathrm{p}}_{\mathrm{i}\mathrm{j}}{\ln \mathrm{p}}_{\mathrm{i}\mathrm{j}}}{2\ln \mathrm{m}}}\right]\times 100\mathrm{\%}$$

(6)

Landscape metrics analysis used raster data as the data source. Therefore, the obtained landscape vector data were converted to raster data and then calculated with Fragstats v4 software [26].

3. Results

3.1. Landscape Composition Analysis

As shown in

Table 2. Area of landscape types in the Xiangjiangyuan Provincial Natural Reserve.

Landscape Types	Experimental Zone (ha)	Buffer Zone (ha)	Core Zone (ha)	Total Area (ha)
Evergreen broad-leaved forest	719.57	238.86	287.13	1245.56
Mixed evergreen deciduous broad-leaved forest	483.36	382.02	995.51	1860.89
Deciduous broad-leaved forest	1006.73	585.14	689.42	2281.28
Mixed coniferous broad-leaved forest	603.05	343.23	676.61	1622.89
Natural coniferous forest	1491.62	675.27	368.36	2535.25
Bamboo forest	162.14	76.50	36.29	274.93
Planted coniferous forest	146.83	54.41	84.21	285.45
Grasslands	99.26	20.12	6.86	126.25
Shrublands	2.85	3.35	2.15	8.35
Navel orange plantations	32.13	6.06	1.06	39.24
Oil-seed camellia plantations	36.66	11.40	11.16	59.21
Tea plantations	0.00	2.07	0.00	2.07
Total area (ha)	4784.19	2398.44	3158.76	10,341.39

, the landscape types were dominated by five major types: evergreen broad-leaved forests, mixed evergreen deciduous broad-leaved forests, deciduous broad-leaved forests, mixed coniferous broad-leaved forests, and natural coniferous forests. The areas of natural coniferous forest and deciduous broad-leaved forest were 2535.25 ha, 2281.28 ha, about 24.52% and 22.06% of the nature reserve, respectively. These two types of landscape were mainly distributed in the experimental zone, about 58.84% and 4.13% of the total area for the landscape types, respectively. The area of mixed evergreen deciduous broad-leaved forest was 1860.89 ha, and the mixed coniferous broad-leaved forest was 1622.89 ha; these two landscapes were mainly distributed in the core zone. In addition, although the evergreen broad-leaved forest had the largest area in the experimental zone (57.77%), it also had a larger area in the core zone. The remaining landscape types were mainly distributed in the experimental zone.

3.2. Naturalness Assessment

The naturalness assessment for the three functional zones is given in

Table 3. The naturalness class in each functional zone of the Xiangjiangyuan Provincial Natural Reserve.

Naturalness Class	Natural Patches (ha)	Recovering Patches (ha)	Managed Patches (ha)	Total Area (ha)
Experimental zone	2209.66	2358.92	215.62	4784.19
Buffer zone	1206.02	1118.48	73.94	2398.44
Core zone	1972.05	1090.28	96.43	3158.76
Total area (ha)	5387.73	4567.68	385.98	10,341.39

and Figure 3. According to the results, the natural patches were the largest naturalness class in the reserve, which occupied 52.10% of whole reserve and accounted for 46.19%, 50.28%, and 62.43% in the experimental zone, buffer zone, and core zone, respectively. The area of recovering patches was 4567.68 ha, accounting for 44.17% of the nature reverse. The managed patches area was 385.98 ha, accounting for 3.73% of the nature reverse, which was mainly distributed in the experimental zone. Hence, the non-managed patches (including natural patches and recovering patches) area accounted for 96.27% of the nature reverse.

3.3. Landscape Pattern Analysis

The landscape indices for the nature reserve and three functional zones are shown in

Table 4. Landscape pattern indices of each functional zone in the Xiangjiangyuan Provincial Natural Reserve.

Landscape Pattern Indices	PD	MPS	LPI	MSI	AWMPFD	CONTAG
Experimental zone	7.40	13.51	11.59	15.14	9.43	279.87
Buffer zone	6.59	15.18	7.52	15.85	0.64	111.00
Core zone	3.86	25.89	16.93	19.84	1.76	101.46
The nature reserve	4.76	21.02	7.17	19.15	2.30	444.64

. According to the results, the experimental zone had the largest PD value. In contrast, the core zone had the smallest value of PD. A decrease in PD and increase in MPS from the experimental zone to core zone indicated that landscape fragmentation along the functional zone had been reduced. Both the experimental zone and the core area had a high LPI index, while the buffer zone had a low LPI, indicating that both the experimental area and the core area had strong landscape dominance, but not in the buffer zone. The dominant landscape of the experimental zone was deciduous broad-leaved forest, and the dominant one in the core zone was mixed evergreen deciduous broad-leaved forest. A low variation of MSI among the three functional zones indicated a low landscape shaped heterogeneity in the nature reserve. The high AWMPFD and CONTAG in the experimental zone indicated the high anthropogenic impact compared with other functional zones.

For the entire nature reserve, the PD and LPI were low, but the MPS was high, indicating that the degree of landscape fragmentation was low and the distribution of the different patch types was relatively uniform. Moreover, the MSI was high, but the AWMPFD was low, indicating that the landscape heterogeneity was high and the anthropogenic activity was low for the nature reserve. In addition, the highest CONTAG for the entire reserve indicated the strong connection between different landscape types.

3.4. Landscape Index of Important Type

The landscape index of the important types in different functional zones is shown in

Table 5. Landscape indices of important types in each functional zone of the nature reserve.

Functional Zone	Landscape Types	PD	MPS	LPI	MSI	AWMPFD
The nature reserve	Evergreen broad-leaved forest	6.83	14.65	18.61	16.94	1.78
	Mixed evergreen deciduous broad-leaved forest	1.13	88.60	39.86	10.51	2.36
	Deciduous broad-leaved forest	2.63	38.01	27.34	14.50	1.78
	Mixed coniferous broad-leaved forest	2.22	45.07	33.37	24.66	2.62
	Natural coniferous forest	2.33	42.95	11.47	33.90	3.66
Experimental zone	Evergreen broad-leaved forest	9.03	11.07	32.05	15.81	2.77
	Mixed evergreen deciduous broad-leaved forest	2.48	40.28	48.19	6.83	0.36
	Deciduous broad-leaved forest	3.58	27.96	55.06	13.16	2.26
	Mixed coniferous broad-leaved forest	4.31	23.19	21.77	17.05	0.35
	Natural coniferous forest	3.35	29.83	19.49	26.80	3.85
Buffer zone	Evergreen broad-leaved forest	11.31	8.84	37.03	13.39	5.10
	Mixed evergreen deciduous broad-leaved forest	4.45	22.45	47.24	6.72	2.38
	Deciduous broad-leaved forest	3.76	26.58	26.51	11.55	1.60
	Mixed coniferous broad-leaved forest	4.96	20.17	37.97	16.32	4.19
	Natural coniferous forest	3.56	28.11	21.78	26.24	5.50
Core zone	Evergreen broad-leaved forest	3.83	26.10	15.28	3.89	0.37
	Mixed evergreen deciduous broad-leaved forest	1.51	66.37	53.72	7.21	4.09
	Deciduous broad-leaved forest	4.06	24.62	40.09	10.22	1.90
	Mixed coniferous broad-leaved forest	2.07	48.33	41.39	5.18	1.70
	Natural coniferous forest	4.07	24.56	22.02	10.26	3.08

. According to the results, the entire nature reserve includes the experiment zone and buffer zone, the PD for the evergreen broad-leaved forest was large and small for other important landscape types but the MPS had inverse changes among the important landscape types. The MPS of mixed evergreen deciduous broad-leaved forests and the MSI of natural coniferous forests were the largest in all functional zones and the entire nature reserve. There was a relatively equally large LPI for all important landscape types in all zones and the entire reserve.

4. Discussion

4.1. The Ecological Integrity of the Nature Reserve

The evaluation of the ecological integrity of a nature reserve is an important field of ecological quality and conservation effectiveness in protected areas [17]. In this research, we used a set of ecological integrity methods in landscape ecology to quantitative assess the integrity and originality of the Xiangjiangyuan Provincial Natural Reserve. The results showed that the natural ecosystem of the nature reserve generally maintained good integrity and originality. Compared with the different functional zones in terms of the degree of fragmentation and anthropogenic activities, this ranked from largest to smallest as follows: experimental zone > buffer zone > core zone. This ranking shows that the functional regionalization was consistent with the protection and utilization objectives of the nature reserve.

In general, the core zone is an area that has been preserved in a natural state [27], or an area where there is hope for gradual restoration into a natural ecosystem that is strictly managed [1,16]. In the Xiangjiangyuan Provincial Natural Reserve, the core zone was located in the eastern part of the reserve, accounting for about 30.5% of the whole nature reserve. The dominant landscapes of the core zone were mixed evergreen deciduous broad-leaved forests, deciduous broad-leaved forests, and mixed coniferous broad-leaved forests. All of these dominant landscape types are in the process of succession, and their succession climax is evergreen broad-leaved forests [28]. The core zone had the smallest value of PD and the largest value of MPS through the nature reserve, it also had the smallest degree of fragmentation and the most complete zone. With enforced conservation management, this zone will evolve into the highest naturalness and ecosystem services [21,29].

In contrast, the buffer zone was comprised of more densely managed patches than the core zone and has a road through it. The MSI was lower in the buffer zone than the core zone, indicating that the originality and integrity were worse than the core zone. The MSI was high in the nature reserve, which is due to the fact that the site has adopted some effective protection measures [30,31]. Similarly, the forest landscape was also very neatly organized into a piece, so the ecological quality of the buffer zone has also been maintained at a relatively good level [13]. The ecological quality of the buffer zone was also maintained at a relatively good level [2,30], which could satisfy the requirements for the survival of rare and endangered plants and animals in the area such as Machilus thunbergii, Bretschneidera sinensis, Neofelis nebulosa, Manis pentadactyla, etc.

The experimental zone accounted for 46.3% of the nature reserve, with the distribution of a large number of deciduous broad-leaved and natural coniferous forests. Its PD was the smallest compared with the other functional zones and the largest MPS [32], which indicated that the experimental zone had the most serious patch fragmentation in the whole nature reserve [16,33]. Among all landscape types in the experimental zone, the LPI of both the deciduous broad-leaved forest and mixed evergreen deciduous broad-leaved forest were high, indicating that these two landscape types were the dominant vegetation types in experimental zone. The MSI was the smallest compared with the other functional zones, indicating that the degree of perceived disturbance was high and the integrity was not as good as that of other areas [23]. Because natural coniferous forests and broadleaf forests have relatively strong environmental adaptability and expansion ability among various landscape types [34], they constantly expand into other vegetation types, making the patch boundary irregular and complex. The highest AWMPFD value was found in the experimental zone [24].

4.2. Implication for the Protected Area Management

The protection goals of the nature reserve include whole-ecosystem protection, natural resource conservation, ecosystem balance maintaining, etc. As the evaluation of the ecological integrity of this nature reserve was based on the landscape ecological principle, the ecosystem integrity of the nature reserve was good, which was not far from the protection target requirements of the nature reserve. The naturalness class of the reserve showed a recovering level with less anthropogenic interference, and the natural forest vegetation was in the middle or late stage of succession. Although a few human-modified and weak human activities existed in the experimental zone [35], the ecological integrity was good because of the low degree of landscape fragmentation and excellent landscape connectivity [36]. Compared with the experimental zone, the buffer zone and core zone were the zones with a relatively high conservation strength, so the ecological integrity was relatively high.

As the naturalness of the Xiangjiangyuan Provincial Natural Reserve was in recovery, the ecological quality of the nature reserve was in the middle or late stage of succession. In order to ensure the further positive development of the ecological quality of the nature reserve, the reserve needs to take the following measures to effectively maintain and improve the integrity of the ecosystem: (1) overall protection by geographical unit [37]; (2) optimization of the distribution of key habitats based on their functional zoning [38]; (3) improvement in the habitat connectivity with an emphasis on mobile-connected species; and (4) assessment of the persistence of ecosystem integrity and original authenticity.

5. Conclusions

We developed a framework of landscape ecological integrity assessment and used it to evaluate a mountain nature reserve in a mid-subtropical region. As seen from the results of the evaluation, the nature reserve maintained good integrity in general, and the naturalness class of the nature reserve was in the recovering level. The degree of landscape fragmentation in each functional zone was as follows: core zone < buffer zone < experimental zone, and the degree of human interference was as follows: core zone < buffer zone < experimental zone. Based on the current status of the ecological integrity of the nature reserve, we suggest some more effective management measures that could be performed for the goal of improving ecosystem integrity. Our findings highlight that continuous maintenance of the high landscape ecological quality of a mountain nature reserve is a long-term and difficult task.