Plant Diversity Research in Shangqiu Yellow River Ancient Course National Forest Park, China

Abstract

The Shangqiu Yellow River Ancient Course National Forest Park, the only national forest park in China created entirely from man-made forests, plays a critical role in ecological conservation. Our research employed plot surveys and quantitative ecological methods, including a diversity index analysis and importance value analysis, to investigate the diversity of arboreal, shrub, and herbaceous plants. This study revealed the composition and distribution of plant communities and analyzed invasive species. It identified dominant plant families, genera, and species and evaluated the types, distribution, and characteristics of invasive plants. We documented 70 families, 177 genera, and 254 species, highlighting that local environmental factors and human activities significantly affect the composition and distribution of plant communities. The presence of 29 invasive plant species poses a risk to the ecosystem. We constructed a phylogenetic tree of the plant community based on rbcL (ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit) gene sequences, revealing the evolutionary relationships among species, and evaluated the community’s stability using the NTI (nearest taxon index) and NRI (net relatedness index). This research aims to provide a scientific foundation for conserving plant diversity and promoting sustainable development, and it can inform ecological protection and biodiversity studies in similar regions.

1. Introduction

Globally, the protection of plant diversity and the pursuit of sustainable development have become a focus of attention for governments and research institutions around the world. Especially in China, with the presence of rapid economic growth and acceleration of urbanization, the protection of the ecological environment and biodiversity is particularly important. Plant diversity is crucial for environmental protection and development; it maintains ecological balance, provides biological resources, enhances ecological services, protects genetic diversity, has cultural and aesthetic value, supports scientific research, promotes economic development, helps to combat climate change, and provides a foundation for ecological restoration [1,2]. A forest park is a large-scale park located on the outskirts of a city or in the suburbs, relying on forest and wildlife resources and their external material environment; these parks are aimed at ecological protection, mainly with ecological functions, and they have functions such as landscape, recreation, and scientific education [3]. China National Forest Park is the highest level of forest parks in mainland China, with high ornamental, scientific, and cultural value, and it has a certain regional representativeness. Shangqiu Yellow River Ancient Course National Forest Park, as China’s sole national forest park created entirely from man-made forests, exhibits particularities such as species uniformity, simplified structure, rapid growth rates, and a high dependency on human management [4]. This study is the first plant diversity research conducted in this park, deeply analyzing the current status of plant diversity and exploring the reasons behind it, which provides a scientific basis for local ecological protection and sustainable development and also provides a reference and lessons for ecological protection in similar plain areas.

In recent years, advancements in plant diversity research have been significantly enhanced through the use of remote sensing satellites for biological monitoring, statistical methods for ecological assessment, and strategic approaches to plant conservation [5,6,7]. Studies have used statistical methods such as non-metric multidimensional scaling (nMDS) and distance-based linear modeling (DistLM) to analyze plant communities in the Mississippi River Delta region, indicating that the composition and biomass of plant communities have been influenced by autogenic and allogenic processes such as sedimentation, subsidence, plant colonization, and succession events [8]. Research has been conducted on crops in the Nile region, suggesting that plant richness has been affected by spatial and climatic conditions, as well as other factors such as construction, human activities, and population ratios [9]. A study has found that the functional traits, functional distinctiveness, and ecological niche characteristics of species collectively determine community beta diversity through the analysis of tree census data, species functional traits, and environmental variables in the tropical karst rainforest of southern China using structural equation modeling [10]. A study in Eastern China’s subtropical forests suggests that ceasing human disturbances leads to a reduction in understory cover and periodic changes in the diversity of both overstory and understory vegetation [11]. In the Yellow River Delta, plant diversity has been investigated using the plot survey method, revealing that Poaceae and Asteraceae are the dominant families, with key species such as Suaeda salsa, Phragmites australis, Setaria viridis, Imperata cylindrica, and Tamarix chinensis [12]. However, existing studies have mostly focused on forests or nature reserves composed of natural forests and secondary forest stands, while artificial forest stands have been relatively understudied. In Shangqiu Yellow River Ancient Course National Forest Park, there has been no plant diversity survey conducted before, and there is a lack of systematic research on the impact of invasive plants, as well as a lack of phylogenetic evolution analysis of the plant communities. This limits our comprehensive understanding of the ecological environment of the area and the formulation of targeted management strategies.

In this research, we set out to explore the intricate tapestry of plant diversity in the Shangqiu Yellow River Ancient Course National Forest Park, an ecological region with distinctive characteristics that warrant detailed investigation. The primary objective of our study is to provide a strong scientific foundation for understanding and valuing the complex plant ecosystems within this man-made forest, emphasizing its unique contribution to regional biodiversity and ecological health. By conducting a thorough examination of the park’s plant communities, we aim to uncover the underlying patterns and mechanisms that sustain this delicate ecological balance. This research is not only essential for the conservation of the park’s rich biodiversity but also for informing strategies that ensure the long-term stability and enhancement of ecological functions, which in turn directly contribute to the environmental well-being and quality of life for the local communities and beyond. Our study, therefore, lays the groundwork for future ecological research and conservation efforts in similar unique ecological regions.

2. Materials and Methods

2.1. Study Area

Shangqiu Yellow River Ancient Course National Forest Park is located in the northern part of Shangqiu City, Henan Province, with geographical coordinates ranging from 34°55′ N–34°58′ N to 115°60′ E–115°73′ E. It has a warm temperate monsoon climate, with an average altitude of 50 m and an average temperature of 14.1 °C. The average highest temperature in July is 26 °C, and the lowest in January is 0.1 °C. The extreme maximum temperature is 43.6 °C, and the extreme minimum is −18.9 °C, with an average frost-free period of 206 days. The soil type is sandy loam with a bulk density of 1.34 g/cm³ and with a pH of 7.5. Due to the influence of the monsoon circulation, there is a significant variation in precipitation with the monsoon. The average annual rainfall is 711 mm, the average relative humidity is 69%, the average wind speed is 3.2 m per second, the maximum wind speed is 24 m per second, and the average number of windy days is between 10 and 15 days. The climate is characterized by distinct seasons, with sufficient rainfall conducive to forest growth. The climate can be summarized as having long, cold winters with little snow and rain, short, dry springs with much wind and sand, hot summers with concentrated rainfall, and clear, sunny autumns with long daylight hours.

In 1958, a forest farm was established in this area for the purpose of afforestation. Over the subsequent 66 years, various measures have been implemented, including tree planting, windbreak and sand fixation, and water conservancy projects. As a result, it has become an important protective forest belt in the region. In 2002, with the approval of the State Forestry Administration, Shangqiu Yellow River Ancient Course National Forest Park was established, becoming the only national-level forest park of artificial plain forest in the country at that time. In 2006, it was awarded the national AAA-level tourist attraction by the National Tourism Administration [13].

2.2. Experimental Design and Data Collection

The on-site survey of plant diversity in the Shangqiu Yellow River Ancient Course Forest Park was conducted using the plot survey method (Figure 1). A total of 10 typical plots were selected, each with 3 large tree quadrats of 20 m × 20 m for a total of 30 quadrats. Within these large quadrats, five shrub quadrats of 5 m × 5 m were established according to the five-point method [14], and five herbaceous quadrats of 1 m × 1 m were also established (Figure 2), making an additional 150 quadrats each and a combined total of 330 quadrats. Tools such as tape measures and the SW-600A handheld rangefinder from Shenda Wei (Shenzhen, Guangdong, China) were used to measure and record the factors of the survey (

Table 1. Investigative factors.

Category	Factors
Arboreal quadrat	Name, quantity, diameter at breast height, height, crown spread
Shrub quadrat	Name, height, cover, density
Herbaceous quadrat Bryophytes	Name, quantity, cover Name, plot number

). Additionally, bryophytes were collected within the 20 m × 20 m tree plots using a specimen collection knife. For GPS positioning, a handheld GPS device, the A8 model from Zhuolin Technology (Hefei, Anhui, China), was utilized to determine the exact coordinates.

During the field survey, plants were identified to the species level where possible; those that could not be fully identified were photographed and numbered. Identification was based on plant characteristics and reference literature such as Flora of China, Trees of China, and Flora of Henan. Invasive alien species were identified with reference to China’s Invasive Plant List and other relevant literature. Bryophytes were identified based on the morphological characteristics of the thallus, leaves, stems, and sporophytes, with reference to Flora of Bryophytes in China. Laboratory observations were conducted using a Murzider MSD701 binocular microscope from Guangzhou, Guangdong, China.

A heatmap, primarily used to describe the correlation matrix of variables, is also used to study the distribution of contingency table data. It allows for an intuitive perception of differences between values. In this study, the abundance data for each species were standardized when creating heatmaps to achieve a good color effect on the heatmap, even when the abundance data varied greatly. The heatmap of invasive plant distribution was created using ‘ggplot2’, ‘reshape2’, and ‘viridis’ in the R language [15].

A phylogenetic tree, also known as a “genealogical tree” or “family tree”, is used in biology to represent the evolutionary relationships between species. This study used rbcL gene sequence data comparisons for construction [16,17]. All target sequences were retrieved and screened from the NCBI GenBank database, excluding sequences of moss plants, fern plants, and some sequences with too much missing data (the accession numbers for these sequences are provided in the Supplementary Materials). The ClustalW algorithm in MEGA 11 software was used for sequence alignment, followed by the construction of a phylogenetic tree using 1000 bootstrap replicates and the neighbor-joining method. The data were then exported and visualized using the ‘Interactive Tree of Life’.

The phylogenetic diversity analysis involved the use of the net relatedness index (NRI) and the nearest taxon index (NTI) [17]. A matrix was established using data recorded from Plot 1 to Plot 10 during the survey, and the calculations were completed using ‘picante’ in R version 4.22.

2.3. Data Analysis

2.3.1. Alpha Diversity Index

The Alpha diversity index is a metric in ecology used to measure the diversity of species within a specific area. For this study, the following four indices have been selected: the Margalef index, Simpson’s diversity index, the Shannon–Wiener diversity index, and Pielou’s evenness index [18,19].

Margalef index:

The Margalef index is a measure of species richness within a community, where S is the total number of species and N is the total number of individuals. This index accounts for the relationship between the number of species and the total number of individuals, making it useful for comparing species richness across different communities.

$${\mathrm{D}}_m={\displaystyle \frac{(\mathrm{S}-1)\mathrm{l}\mathrm{n}\left(\mathrm{N}\right)}{\mathrm{l}\mathrm{n}\left(\mathrm{S}\right)}}$$

(1)

Simpson’s diversity index:

Simpson’s diversity index measures the diversity of a community by taking into account the relative abundance of species. Here, n is the number of individuals of the i-th species, and N is the total number of individuals in the community. The value approaches 1 as species are more evenly distributed, indicating higher diversity.

$${\mathrm{D}}_s=1-{\displaystyle \frac{{\sum }_{i=1}^{s}n(n-1)}{\mathrm{N}(\mathrm{N}-1)}}$$

(2)

Shannon–Wiener diversity index:

The Shannon–Wiener diversity index considers both species richness and evenness of the individual distribution. $p_i$ is the proportion of the total community made up by the i-th species. A higher value of this index indicates greater community diversity.

$$\mathrm{H}=-{\sum }_{i=1}^S{p}_{i}ln\left(p_i\right)$$

(3)

Pielou’s evenness index:

Pielou’s evenness index measures the uniformity in the distribution of individual species within a community. H is the Shannon–Wiener Diversity Index, and lns is the maximum possible diversity index given the number of species S. An evenness index close to 1 indicates a more uniform distribution of species.

$$\mathrm{J}={\displaystyle \frac{\mathrm{H}}{\mathrm{l}\mathrm{n}s}}$$

(4)

2.3.2. Frequency and Importance Values

Frequency:

The term “Frequency” refers to the proportion of quadrats in which a particular plant species is observed.

Tree importance value (TIV):

The TIV is a composite indicator used to assess the significance of tree species within a community, often incorporating factors such as density, basal area, and frequency [20].

$$\mathrm{TIV}={\displaystyle \frac{\mathrm{R}\mathrm{e}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}\mathrm{D}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{i}\mathrm{t}\mathrm{y}\left(\mathrm{R}\mathrm{D}\right)+\mathrm{R}\mathrm{e}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}\mathrm{F}\mathrm{r}\mathrm{e}\mathrm{q}\mathrm{u}\mathrm{e}\mathrm{n}\mathrm{c}\mathrm{y}\left(\mathrm{R}\mathrm{F}\right)+\mathrm{R}\mathrm{e}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}\mathrm{D}\mathrm{o}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e}\left(\mathrm{R}\mathrm{D}\mathrm{m}\right)}{3}}$$

(5)

Shrub and grass importance value (SGIV):

The specific formula for SGIV is not provided, but it is analogous to TIV for shrubs and grasses.

$$\mathrm{SGIV}={\displaystyle \frac{\mathrm{R}\mathrm{e}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}\mathrm{D}\mathrm{e}\mathrm{n}\mathrm{s}\mathrm{i}\mathrm{t}\mathrm{y}\left(\mathrm{R}\mathrm{D}\right)+\mathrm{R}\mathrm{e}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}\mathrm{F}\mathrm{r}\mathrm{e}\mathrm{q}\mathrm{u}\mathrm{e}\mathrm{n}\mathrm{c}\mathrm{y}\left(\mathrm{R}\mathrm{F}\right)+\mathrm{R}\mathrm{e}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}\mathrm{C}\mathrm{o}\mathrm{v}\mathrm{e}\mathrm{r}\left(\mathrm{R}\mathrm{C}\right)}{3}}$$

(6)

2.3.3. Phylogenetic Diversity Indices

Nearest taxon index (NTI):

The NTI compares the mean nearest taxon distance observed in the community to that expected under a null model, providing insight into the degree of phylogenetic clustering.

$$\mathrm{NTI}={\displaystyle \frac{{\mathrm{M}\mathrm{N}\mathrm{T}\mathrm{D}}_{\mathrm{o}\mathrm{b}\mathrm{s}}-mean\left({\mathrm{M}\mathrm{N}\mathrm{T}\mathrm{D}}_{ran}\right)}{sd\left({\mathrm{M}\mathrm{N}\mathrm{T}\mathrm{D}}_{ran}\right)}}$$

(7)

${\mathrm{M}\mathrm{N}\mathrm{T}\mathrm{D}}_{ran}$ refers to the mean nearest taxon distance in a null model; ${\mathrm{M}\mathrm{P}\mathrm{D}}_{obs}$ refers to the mean nearest taxon distance observed in the survey data.

Net relatedness index (NRI):

The NRI measures the mean pairwise phylogenetic distance between species relative to a null model, with values significantly different from zero indicating phylogenetic structure.

$$\mathrm{NRI}={\displaystyle \frac{{\mathrm{M}\mathrm{P}\mathrm{D}}_{obs}-mean\left({\mathrm{M}\mathrm{P}\mathrm{D}}_{ran}\right)}{sd\left({\mathrm{M}\mathrm{P}\mathrm{D}}_{ran}\right)}}$$

(8)

MPD refers to the mean pairwise distance.

3. Results

3.1. Plant Species Composition Characteristics and Regional Distribution

3.1.1. Plant Species Composition and Quantitative Features

During the survey, we discovered a total of 70 families, 177 genera, and 254 species. According to botanical taxonomy, the findings included 58 families, 160 genera, and 234 species of angiosperms; 3 families, 8 genera, and 10 species of gymnosperms; 2 families, 2 genera, and 3 species of ferns; and 7 families, 7 genera, and 7 species of bryophytes (Figure 3). When classified by plant life form, the results were as follows: 23 families, 44 genera, and 63 species of trees; 17 families, 25 genera, and 31 species of shrubs; 38 families, 105 genera, and 153 species of herbaceous plants; and 7 families, 7 genera, and 7 species of bryophytes (Figure 4).

In the survey, 70 plant families were identified and categorized by family size according to the following criteria: large families with 10 or more species, medium families with 5 to 9 species, small families with 2 to 4 species, and single-species families with only 1 species (

Table 2. Rank of plant family sizes.

No.	Family	Genus Number	Species Number	No.	Family	Genus Number	Species Number
1	Asteraceae	16	35	36	Araceae	2	2
2	Poaceae	21	26	37	Pottiaceae	1	1
3	Rosaceae	11	25	38	Cannabaceae	1	1
4	Fabaceae	11	14	39	Juncaceae	1	1
5	Cyperaceae	5	10	40	Eucommiaceae	1	1
6	Polygonaceae	3	9	41	Marchantiaceae	1	1
7	Amaranthaceae	7	9	42	Brachytheciaceae	1	1
8	Cupressaceae	5	6	43	Funariaceae	1	1
9	Lamiaceae	6	6	44	Salviniaceae	1	1
10	Sapindaceae	3	6	45	Zygophyllaceae	1	1
11	Convolvulaceae	3	6	46	Ceratophyllaceae	1	1
12	Plantaginaceae	2	4	47	Simaroubaceae	1	1
13	Oleaceae	3	4	48	Calycanthaceae	1	1
14	Vitaceae	3	4	49	Lentibulariaceae	1	1
15	Brassicaceae	4	4	50	Nelumbonaceae	1	1
16	Salicaceae	2	4	51	Portulacaceae	1	1
17	Apocynaceae	3	3	52	Arecaceae	1	1
18	Malvaceae	3	3	53	Paulowniaceae	1	1
19	Magnoliaceae	2	3	54	Onagraceae	1	1
20	Moraceae	3	3	55	Caryophyllaceae	1	1
21	Pinaceae	2	3	56	Ebenaceae	1	1
22	Platanaceae	1	3	57	Rhamnaceae	1	1
23	Potamogetonaceae	1	3	58	Nymphaeaceae	1	1
24	Ulmaceae	2	3	59	Myrtaceae	1	1
25	Euphorbiaceae	2	2	60	Celastraceae	1	1
26	Aquifoliaceae	1	2	61	Berberidaceae	1	1
27	Meliaceae	2	2	62	Haloragaceae	1	1
28	Equisetaceae	1	2	63	Fossombroniaceae	1	1
29	Lythraceae	2	2	64	Urticaceae	1	1
30	Rubiaceae	2	2	65	Ginkgoaceae	1	1
31	Solanaceae	2	2	66	Alismataceae	1	1
32	Caprifoliaceae	2	2	67	Bryaceae	1	1
33	Apiaceae	2	2	68	Boraginaceae	1	1
34	Paeoniaceae	1	2	69	Grimmiaceae	1	1
35	Hydrocharitaceae	2	2	70	Oxalidaceae	1	1

).

The surveyed area includes 5 large plant families comprising 64 genera and 110 species, representing 35.16% of the total genera and 43.31% of the total species count, respectively. Additionally, there are 6 medium families (27 genera, 42 species), 25 small families (52 genera, 68 species), and 34 single-species families (34 genera, 34 species), making up 15.25% and 16.54%, 29.38% and 26.77%, and 19.21% and 13.39% of the total counts, respectively.

In this research area, no genera are exceptionally large. The medium-sized genera, comprising 5 to 9 species each, total five and make up 2.82% of the genera, while their species account for 11.42% of all species. The 39 small genera, with 2 to 4 species each, constitute 22.03% of the genera and 36.22% of the species. The remaining 133 genera are single-species genera, representing 75.14% of the genera and 52.36% of the species.

In the survey, the Equisetaceae family was unique, containing two species: Equisetum arvense and Equisetum ramosissimum. In contrast, all other identified fern and bryophyte species were represented by a single genus and species each. These include Salvinia natans (Salviniaceae), Tortula subulata (Pottiaceae), Marchantia polymorpha L. (Marchantiaceae), Brachythecium pulchellum (Brachytheciaceae), Funaria hygrometrica (Funariaceae), Fossombronia pusilla (Fossombroniaceae), and Bryum argenteum (Bryaceae).

3.1.2. Regional Distribution of Families

In terms of distribution types, the Type 1 cosmopolitan distribution in this area includes prominent families such as Fabaceae, Poaceae, Rosaceae, Cyperaceae, and Brassicaceae, among others, comprising a total of 28 families. These account for 40% of the total number of identified families. However, while these widely distributed families contribute significantly to the area’s plant diversity, they do not adequately represent the region’s unique flora. Consequently, analyzing these families provides limited insight into the area’s phylogenetic distinctiveness.

Tropical distributions cover three categories, with families such as Asteraceae, Araceae, Zygophyllaceae, Meliaceae, and others, totaling 14 families that account for 20% of the total number of families, with Type 2 pantropical distribution making up the majority.

Temperate distributions are divided into five categories, with families such as Polygonaceae, Moraceae, Sapindaceae, Rhamnaceae, and others, totaling 26 families which account for 37.14% of the total number, with Type 8 northern temperate distribution being the predominant category.

Additionally, there are two families with Type 15 endemic distribution unique to China found in this research area, which are Ginkgoaceae and Eucommiaceae (Figure 5).

3.1.3. Results of Alpha Diversity Index Calculations

As shown in Figure 6, The Margalef index is a measure of species richness, reflecting the number of species in a community. The higher the value, the greater the species richness. The order is herbaceous layer > arboreal layer > shrub layer, with a significant difference, where the herbaceous and shrub layers have values of 14.66 and 10.06, indicating a high species richness. The shrub layer only has a value of 3.54, indicating lower richness, mainly due to the selection and cultivation of dominant plants by humans in the artificial forest environment.

Simpson’s diversity index is a measure of species diversity within a community, taking into account the relative abundance of species. The closer the value is to one, the more evenly the species are distributed and the higher the diversity. The indices for the three layers are close to one, indicating a very even species distribution and high diversity.

The Shannon–Wiener diversity index is an index that takes into account both species richness and evenness of individual distribution. The larger the value, the higher the diversity of the community. The indices for the three layers are 3.55, 3.26, and 4.22, all of which are at a moderate level, indicating a certain degree of species richness and evenness of individual distribution.

Pielou’s evenness index is a measure of the evenness of species distribution within a community, which is the ratio of the Shannon–Wiener index to the maximum possible diversity index. The closer the value is to one, the more even the species distribution. The indices for the three layers are 0.86, 0.95, and 0.84, indicating that the distribution of plant species individuals in the three layers is even, with the comparison showing that the shrub layer > arboreal layer > herbaceous layer.

3.2. Dominant and Characteristic Groups

3.2.1. Dominant Families and Genera and Characteristic Families and Genera

Dominant families and genera are primarily determined by the endemism value of the families, considering those above the average. A family’s endemism value is calculated as the sum of the proportions of its genera and species relative to the total number of genera and species of that family in the global flora. The endemism value for a genus is the ratio of the number of species it contains to the total number of species worldwide. The survey revealed five dominant families in the flora of the Shangqiu Yellow River Ancient Course National Forest Park, comprising 64 genera and 110 species. These dominant families include Asteraceae, Poaceae, Rosaceae, Fabaceae, and Cyperaceae. Characteristic families, identified based on the phylogenetic importance values within the flora (Figure 7), are Cupressaceae, Amaranthaceae, and notably, Rosaceae, which is also a dominant family in the region’s flora.

There are five dominant genera within the flora, accounting for 29 species in total. The principal dominant genera are Prunus, Cyperus, Rosa, Artemisia, and Persicaria. Two characteristic genera, identified based on the phylogenetic importance values within the flora (Figure 8), are Cyperus and Prunus.

3.2.2. Dominant Species Frequency and Importance Values

The plant species importance value is a comprehensive quantitative indicator that analyzes the status and role of a species within a certain area. It is also a comprehensive reflection of relative density, relative dominance, and relative frequency. Analysis of the importance value can reflect the overall situation of plant species in the area, and research on relative density, relative frequency, and relative dominance can make it more specific. According to the survey of dominant species (

Table 3. Dominant species frequency and importance values.

Tree	Frequency	TIV	Shrub	Frequency	SGIV	Herbaceous	Frequency	SGIV
Populus tomentosa	12.6	18.73	Lagerstroemia indica	11.2	14.25	Imperata cylindrica	8.19	8.87
Robinia pseudoacacia	10.8	8.05	Paeonia suffruticosa	9.6	12.22	Digitaria sanguinalis	7.56	8.19
Paulownia fortunei	7.2	6.29	Lonicera japonica	8.8	13.87	Cynodon dactylon	5.67	5.43
Ulmus pumila	5.3	5.02	Ligustrum lucidum	7.13	13.39	Setaria viridis	4.73	5.12
Ginkgo biloba	3.2	3.64	Photinia serratifolia	7.2	13.53	Humulus scandens	4.1	19.79
Salix matsudana	3.6	3.55	Cercis chinensis	6.8	13.6	Tribulus terrestris	3.78	4.41
Cupressus funebris	3.2	2.68	Forsythia suspensa	5.6	7.13	Erigeron canadensis	3.47	4.04
Eucommia ulmoides	2.9	2.15	Acer palmatum	3.2	6.59	Ipomoea nil	2.21	10.66

), the dominant trees include Populus tomentosa, Robinia pseudoacacia, Paulownia fortunei, Ulmus pumila, Ginkgo biloba, Salix matsudana, Cupressus funebris, and Eucommia ulmoides; dominant shrubs include Lagerstroemia indica, Paeonia suffruticosa, Lonicera japonica, Ligustrum lucidum, Photinia serratifolia, Cercis chinensis, Forsythia suspensa, and Acer palmatum; and dominant herbaceous plants include Imperata cylindrica, Digitaria sanguinalis, Cynodon dactylon, Setaria viridis, Humulus scandens, Tribulus terrestris, Erigeron canadensis, and Ipomoea nil.

3.3. Invasive Plant Diversity

3.3.1. Composition of Invasive Plant Species

According to the grading in the Catalogue of Invasive Alien Species in China, invasive plant species in China are divided into seven levels: Level 1, severely invasive; Level 2, seriously invasive; Level 3, locally invasive; Level 4, generally invasive; Level 5, to be observed; Level 6, recommended for eradication; and Level 7, indigenous to China. The survey found that there are 29 invasive species in this area, belonging to 11 families and 21 genera, including 10 species at Level 1, 9 species at Level 2, 10 species at Level 4, and 1 species at Level 5 (

Table 4. Inventory of invasive plants in the area.

No.	Family	Genus	Species	Level
1	Asteraceae	Erigeron	Erigeron canadensis	1
2	Asteraceae	Erigeron	Erigeron annuus	1
3	Asteraceae	Erigeron	Erigeron sumatrensis	1
4	Asteraceae	Bidens	Bidens pilosa	1
5	Asteraceae	Symphyotrichum	Symphyotrichum subulatum	1
6	Amaranthaceae	Alternanthera	Alternanthera philoxeroides	1
7	Amaranthaceae	Celosia	Celosia argentea	1
8	Amaranthaceae	Amaranthus	Amaranthus retroflexus	1
9	Convolvulaceae	Ipomoea	Ipomoea purpurea	1
10	Plantaginaceae	Veronica	Veronica persica	2
11	Euphorbiaceae	Ricinus	Ricinus communis	2
12	Fabaceae	Trifolium	Trifolium repens	2
13	Poaceae	Avena	Avena fatua	2
14	Asteraceae	Erigeron	Erigeron bonariensis	2
15	Solanaceae	Datura	Datura stramonium	2
16	Apiaceae	Daucus	Daucus carota	2
17	Onagraceae	Oenothera	Oenothera curtiflora	2
18	Convolvulaceae	Ipomoea	Ipomoea nil	2
19	Malvaceae	Abutilon	Abutilon theophrasti	3
20	Asteraceae	Bidens	Bidens bipinnata	3
21	Fabaceae	Robinia	Robinia pseudoacacia	4
22	Poaceae	Lolium	Lolium perenne	4
23	Asteraceae	Sonchus	Sonchus wightianus	4
24	Asteraceae	Sonchus	Sonchus oleraceus	4
25	Asteraceae	Sonchus	Sonchus asper	4
26	Asteraceae	Eclipta	Eclipta prostrata	4
27	Amaranthaceae	Oxybasis	Oxybasis glauca	4
28	Amaranthaceae	Amaranthus	Amaranthus tricolor	4
29	Fabaceae	Sesbania	Sesbania cannabina	5

).

3.3.2. Distribution of Invasive Plants

The 29 invasive plant species discovered in the survey are categorized by their place of origin into five major geographical distribution areas, excluding Oceania and Antarctica: America (South America, North America), Asia, Europe, Africa, and the Mediterranean region (Figure 9). Among them, the most invasive species are native to America, with a total of fourteen species, accounting for 48.3% of the total number of invasive plant species; the rest were native to Asia and the Mediterranean with four species each, Europe with three species, and Africa with two species, accounting for 13.8%, 13.8%, 10.3%, and 6.9% of the total number, respectively.

Based on the distribution of invasive plants across the 10 sampling plots surveyed, a heatmap was constructed using R version 4.22. The species were categorized into four levels according to their quantities: Low, Medium Low, Medium High, and High, indicating the varying degrees of impact on the sampling plots (Figure 10).

3.4. Phylogenetic Diversity

3.4.1. Phylogenetic Tree

The phylogenetic tree of the plant community in the study area (Figure 11) was constructed from 187 species of plants, belonging to 51 families and 138 genera. The plant species of Apocynaceae, Convolvulaceae, Rubiaceae, Brassicaceae, Lamiaceae, Plantaginaceae, Paulowniaceae, and Oleaceae have relatively close phylogenetic relationships; the plant species of Pinaceae, Ginkgoaceae, Cupressaceae, Arecaceae, Alismataceae, Poaceae, and Cyperaceae have relatively close phylogenetic relationships; the plant species of Apiaceae, Salicaceae, Asteraceae, and some genera of Rosaceae have relatively close phylogenetic relationships; and the plant species of Rhamnaceae, Moraceae, Euphorbiaceae, Ulmaceae, Eucommiaceae, Meliaceae, Simaroubaceae, Zygophyllaceae, Onagraceae, Sapindaceae, Caryophyllaceae, Portulacaceae, Amaranthaceae, Berberidaceae, Vitaceae, Fabaceae, Polygonaceae, Urticaceae, and some genera of Rosaceae have relatively close phylogenetic relationships, while Abutilon theophrasti of Malvaceae and Firmiana simplex are relatively distant from other plant species of different families in terms of phylogenetic relationships.

In terms of divergence time, species with shorter divergence times include Lagerstroemia indica, Humulus scandens, Hemiptelea davidii, Platanus occidentalis, Melia azedarach, Styphnolobium japonicum, Firmiana simplex, Populus canadensis, Aster altaicus, Vernicia fordii, Eriobotrya japonica, Malus honanensis, Prunus persica, Boehmeria nivea, Ricinus communis, Pyrus bretschneideri, and Crataegus pinnatifida.

3.4.2. Results of Phylogenetic Diversity Indices

Using the R language “picante” package, the net relatedness index (NRI) and nearest taxon index (NTI) values for the plant communities of plot1 to plot10 were calculated (Figure 12). Both the NRI and NTI values are significantly different from zero, indicating a certain phylogenetic structure, with the results being statistically significant in a t-test.

NTI at 0.78: This indicates that in the studied plant community or ecosystem, the net increase in taxonomic units (such as new species or subspecies) is relatively small. The NTI being close to one but being less than one suggests an increase in species diversity, but not to a great extent.

NRI at 1.09: This indicates a significant net increase in species richness. The NRI being close to and greater than one is generally a positive signal, suggesting an increase in the number of species and an enhancement of species diversity in the ecosystem.

4. Discussion

4.1. Discussion on Plant Species Composition and Regional Distribution

Shangqiu Yellow River Ancient Course National Forest Park is rich in flora with a total of 70 families, 177 genera, and 254 species, particularly in the arboreal and herbaceous layers, where the Margalef indices are 14.66 and 10.06, respectively, indicating a medium-high level of species richness and even distribution. When compared with other forest parks in China that share similar latitudes and longitudes and that are part of the warm temperate deciduous broadleaf forest region, the plant diversity is found to be lower than that of parks situated in natural forest and secondary forest environments. For instance, a study on plant diversity in Songding National Forest Park in Henan revealed a total of 155 families, 656 genera, and 1601 species of vascular plants [21]. However, when compared with forest parks dominated by artificial forests in similar settings, the diversity at Shangqiu is considerably richer. An investigation into plant diversity in Zhengzhou City Forest Park, for example, identified 50 families, 102 genera, and 132 species of plants [22].

In terms of the regional distribution of species, tropical plants account for 20%, and temperate plants account for 37.14%, which together make up the majority. This is related to the local climate, soil, and precipitation. A study has shown that half of the factors contributing to species richness can be attributed to the climate itself or to the geographical distribution of the climate [23]. The study area, a plain region with a warm temperate monsoon climate, experiences distinct seasons and receives sufficient rainfall, creating favorable conditions for plant diversity. Additionally, this area is home to two endemic species of China: Ginkgo biloba, a rare relict species from the Mesozoic era, and Eucommia ulmoides, which is classified as vulnerable (VU). Research indicates that Ginkgo biloba exhibits a range of beneficial effects, including improvements in age-related memory deficits, hepatoprotective properties, and potential anti-cancer activities, due to its rich array of bioactive compounds. On the other hand, Eucommia ulmoides, known for its various edible and medicinal parts, demonstrates significant value in functional food applications because of its content of flavonoids, phenols, terpenoids, and polysaccharides, which contribute to its overall health-promoting properties [24,25].

It is worth noting that among ferns, Equisetum ramosissimum and Salvinia natans possess significant value. Studies have indicated that Equisetum ramosissimum is a primary ingredient in the traditional Chinese medicine for blood lipid reduction, known as the “Tongmai Jiangzhi” class of drugs. Its crude extract has been shown to significantly lower the levels of total cholesterol (TC), total triglycerides (TGs), and beta-lipoprotein in the serum of rabbits with hyperlipidemia [26]. Salvinia natans, which thrives in unpolluted aquatic environments, has both ornamental appeal and algal inhibition effects, playing a positive role in water purification [27]. The remaining ferns and mosses are single-species entities, such as Equisetum arvense, Funaria hygrometrica, Marchantia polymorpha L., Bryum argenteum, and Brachythecium pulchellum, all of which have a broad global distribution. Fossombronia pusilla, Niphotrichum canescens, and Tortula subulata are widely distributed across the north temperate zone. Overall, ferns and bryophytes constitute a small proportion of the flora, indicating low species richness.

4.2. Discussion on Dominance and Characteristic Groups

In Shangqiu Yellow River Ancient Course National Forest Park, the distribution characteristics of dominant and characteristic groups are prominent. Dominant groups, with rich species diversity and extensive geographical distribution, have taken a leading position in the park’s ecosystem. According to the survey results, the dominant families include Asteraceae, Poaceae, Rosaceae, Fabaceae, and Cyperaceae. These families’ plants have occupied advantageous positions in multiple ecological niches within the park due to their strong adaptability, reproductive capacity, and ecological niche width. The formation of dominant groups is influenced by various factors. When compared with other plant diversity studies conducted under similar environmental conditions, a high degree of similarity is observed; for instance, in the plant diversity survey of Songding National Forest Park in Henan, dominant families included Asteraceae, Poaceae, Fabaceae, Rosaceae, etc. [21]. Similarly, in the study of plant diversity in the Henan Yellow River Wetlands, dominant families were identified as Asteraceae, Poaceae, Fabaceae, and Cyperaceae [28]. Characteristic groups embody the uniqueness of the region’s flora; their presence not only enhances biodiversity but also mirrors the characteristics of the regional ecosystem. For example, Cupressaceae and Amaranthaceae, along with Rosaceae, which is both a dominant and a characteristic family, have a formation of characteristic groups that is closely tied to the region’s biogeographical history and endemism. The emergence of both dominant and characteristic groups is associated with a variety of factors. First, the suitability of environmental conditions is one of the key factors. Shangqiu Yellow River Ancient Course National Forest Park is located in a warm temperate monsoon climate zone, with distinct seasons and sufficient rainfall, providing good growth conditions for a variety of plants. Second, long-term human afforestation and garden management activities have promoted the spread and formation of dominant positions of some high-value plant species. In addition, plants represented by herbaceous types, combined with their own biological characteristics, such as reproductive strategy, growth rate, and adaptability, have played an important role in the process of becoming dominant groups.

In terms of importance within the community, for instance, trees with high importance values and frequency such as Populus tomentosa, Robinia pseudoacacia, and Paulownia fortunei are common in artificial forests in northern China. Studies have indicated a complementary coexistence mechanism between the fine roots and water absorption ecological niches of Populus tomentosa and Robinia pseudoacacia [29]. Paulownia fortunei, Eucommia ulmoides, Ulmus pumila, and Ginkgo biloba are plants with ecological, economic, and aesthetic value, significantly influenced by human activities. Shrubs with higher frequency and importance values are often greening plants; species like Ligustrum lucidum, Lagerstroemia indica, Paeonia suffruticosa, Lonicera japonica, Photinia serratifolia, and Acer palmatum are typical for urban and garden greening. Dominant herbaceous plants are characterized by strong adaptability, competitiveness, reproductive capacity, or rapid growth, enabling them to quickly cover the ground and suppress the growth of other plants, such as Imperata cylindrica, Digitaria sanguinalis, Humulus scandens, Erigeron canadensis, and Ipomoea nil. They play a key role in forming forest structures, maintaining ecological functions, and providing biodiversity, including providing habitats, food resources, and participating in ecological processes. The tree layer can regulate local climate, reduce surface runoff, and increase water infiltration into the soil, thus helping to maintain the hydrological cycle of the ecosystem. The plants of the shrub and herbaceous layers provide organic matter and nutrient cycling to the soil through their seasonal growth and decay, promoting the improvement of soil fertility. The frequency and importance of these plants also reveal the impact of human activities on vegetation. Due to urban greening and afforestation projects, certain plant species may become more common in the park. At the same time, the high frequency of these plants also suggests a potential risk of over-reliance in the ecosystem; if these species are affected by diseases or pests, it may have adverse effects on the entire ecosystem [30].

4.3. Discussion on Invasive Plant Diversity

In Shangqiu Yellow River Ancient Course National Forest Park, a total of 11 families, 21 genera, and 29 species of invasive plants are documented. The research indicates that the variety of invasive plants is relatively rich, with the primary families being Asteraceae and Amaranthaceae. These species share characteristics such as rapid growth, high reproductive rates, and broad ecological adaptability. Referring to the findings of previous research, especially the analysis of ecological niche shifts and the potential allelopathic effects in invasive plants of the genus Erigeron (Asteraceae) [31,32], it is highly probable that these invasive species can swiftly occupy ecological niches, thereby impacting local species. For example: Erigeron canadensis, Erigeron annuus, and Erigeron sumatrensis. These species are all classified as a Level 1 severely invasive, possessing strong adaptability and reproductive capacity, and they are capable of rapid spread and posing a serious threat to local ecosystems [33,34]. Bidens pilosa has rapid growth, high reproductive rates, and a wide adaptability to environmental conditions [35]. Ipomoea purpurea and Ipomoea nil have climbing growth characteristics, and they are able to cover other plants, affecting their light exposure and growth. Ricinus communis, as a Level 2 seriously invasive species, has strong competitiveness and adaptability, and it is capable of growing in various environments and potentially producing harmful chemicals to other plants [36]. Trifolium repens, as a Level 2 seriously invasive species, has the characteristics of rapid growth and widespread distribution, capable of forming dense vegetation cover in grasslands and open areas. Avena fatua, as a Level 2 seriously invasive species, has a high growth rate and competitiveness, and it is capable of rapidly spreading in farmland and other crop-growing areas [37]. Sonchus oleraceus and Sonchus asper, classified as Level 4 general invaders, have moderate adaptability and spreading ability but pose a threat to local ecosystems. Research suggests that they share a recent common ancestry, as revealed by our study of their chloroplast genomes [38]. Eclipta prostrata, as a Level 4 general invasive species, has good adaptability and can grow in various soil types, potentially affecting surrounding plants through its growth habits.

From the perspective of geographical origin, most successfully invasive plants belong to the pantropical distribution, with America being the most important place of origin. The Shangqiu Yellow River Ancient Course National Forest Park has a variety of climate types from warm temperate to cold temperate, which has certain commonality with the pantropical region in climatic conditions, providing a suitable living and spreading environment for these invasive plants. This climatic similarity is conducive to the invasion and settlement of pantropical plant genera. According to the theory of continental drift, North America and Asia have certain similarities in plant genetics [39]. Therefore, invasive plants from North America can quickly adapt and expand in the Central Plains region, partly because they are not easily limited by pathogens from their places of origin, thus being able to reproduce rapidly and occupy local ecological niches, potentially becoming dominant species. At the same time, although some African plants can adapt to China’s climate, due to the relatively limited trade between China and Africa, there are relatively fewer invasive plant species originating from Africa. In the past decade, China’s trade with the Americas accounted for 21.5% of its total compared with Africa’s 4.5% [40].

In response to invasive plants, first establish a monitoring and early warning mechanism: Set up a system for the census and monitoring of alien invasive species, conduct invasion surveys at regular intervals, and ascertain the types, quantities, distribution ranges, affected areas, and degrees of harm of these species, providing data support for scientific prevention and control. Construct a monitoring network, carry out routine monitoring, collect and summarize monitoring information in a timely manner, and issue early warning forecasts. Secondly, carry out management and restoration work effectively: This should occur during the critical growth stages of invasive plants, such as the seedling stage, flowering stage, or fruiting stage, implement measures like manual removal, mechanical eradication, application of environmentally friendly pesticides, and release of biological control agents. For ecosystem restoration, consider planting native species and reintroducing local varieties.

4.4. Discussion on Phylogenetic Diversity

The plant community phylogenetic diversity in the Shangqiu Yellow River Ancient Course National Forest Park exhibits significant diversity. Through the construction of the phylogenetic tree, it was observed that 187 species of plants are distributed across 51 families and 138 genera. Some families of species, such as Apocynaceae, Convolvulaceae, and Rubiaceae, show a closer phylogenetic relationship, while the species of Malvaceae are more distantly related to other plants. This diversity not only reflects the richness of species but also the complexity of the evolutionary relationships among them. The NRI and NTI values calculated using the R language “picante” package further reveal the phylogenetic structure of the plant community. The α-phylogenetic structure of the plant community shows a clustered distribution, with an NRI value of 1.09, which indicates a significant net increase in species richness, and an NTI value of 0.78, which suggests a relatively small net increase in taxonomic units; however, both indices still demonstrate an overall enhancement in species diversity. This increase is mainly related to local environmental protection measures and ecological restoration, effectively promoting the growth of species diversity.

The formation of phylogenetic diversity is a complex process. The environmental conditions of the area, especially the warm temperate monsoon climate and suitable terrain and soil types, provide a foundation for the growth of a variety of plants. Long-term natural selection and adaptive evolution have promoted the differentiation of species and increased phylogenetic diversity. Large-scale afforestation and ecological protection measures in recent decades have played an important role in the construction and maintenance of plant communities. They have not only increased the richness of species but also affected the interactions and evolutionary processes among species. According to the literature review and field surveys, the local government provides financial and project support every year and has introduced a series of ecological protection and environmental improvement policies and measures, including the construction of ecological corridors, windbreak and sand fixation, mixed forest development, strengthening wetland protection and restoration, and forest nurturing and resource management [41]. The management department strictly manages the park, including prohibiting deforestation and reclamation, sand excavation, and digging of medicinal materials and wild vegetables that damage the forest ecological environment; long-term monitoring, establishing environmental quality files, strictly controlling pollution from wastewater, exhaust gases, and solid waste; strengthening disaster monitoring and prediction, strengthening forest fire prevention, lay out fire-fighting facilities as required by regulations; and strengthen the prediction and prevention of forest diseases and pests, mainly using biological control combined with chemical control measures [42]. These factors are important contributors to the recovery and growth of plant community diversity.

5. Conclusions

Shangqiu Yellow River Ancient Course National Forest Park, with its rich plant diversity that encompasses 70 families, 177 genera, and 254 species, plays a pivotal role in global biodiversity conservation. The park’s unique geographical location, favorable climate conditions, and diverse environmental factors foster an ecosystem that supports a high richness of plant species and an even distribution. This biodiversity is not just an asset but also a critical component, providing essential ecosystem services such as carbon sequestration, habitat provision, and water purification. Particularly important as a sanctuary for endangered species, the park is an invaluable resource for scientific research and environmental education, and it serves as a model for sustainable development through eco-tourism. The park’s conservation efforts and management practices are integral to the global biodiversity network, offering valuable insights and strategies for ecological protection worldwide. Moreover, the park’s comprehensive research on plant diversity in a man-made forest environment provides a valuable reference for similar studies in other artificial forest settings, contributing to the broader understanding and conservation of biodiversity in such ecosystems.

The dominant families are families such as Asteraceae, Poaceae, Rosaceae, Fabaceae, and Cyperaceae, with dominant genera such as Prunus, Cyperus, Rosa, Artemisia, and Persicaria. These plants have become ecologically dominant due to their strong environmental adaptability, high reproductive capacity, and human selection. Families like Asteraceae and Poaceae, and characteristic groups such as Cupressaceae and Amaranthaceae, reflect the uniqueness and ecological value of the regional biodiversity. Dominant species such as arboreal Populus tomentosa and Robinia pseudoacacia, shrubs like Lagerstroemia indica and Paeonia suffruticosa, and robust herbaceous plants including Imperata cylindrica and Digitaria sanguinalis owe their dominance to environmental conditions, human intervention, and their own biological characteristics. These species play a significant role in the ecosystem. The frequency and importance of these species reflect the outcomes of human activities and natural selection.

Shangqiu Yellow River Ancient Course National Forest Park hosts a significant number of invasive plants, with a total of 11 families, 21 genera, and 29 species identified. Notably, the Asteraceae and Amaranthaceae are predominant among these invaders. Characterized by rapid growth, high reproductive rates, and broad ecological adaptability, these species can swiftly occupy ecological niches and outcompete indigenous species. Predominantly from America, these invasive species have a wide regional distribution. Beyond the competition for resources and disruption of food webs, these species also threaten biodiversity through allelopathic effects, which can poison other plants and alter ecosystem functions. The detrimental impacts underscore the urgency for robust management and control strategies to curb their proliferation and safeguard native ecosystems.

The plant community in Shangqiu Yellow River Ancient Course National Forest Park has been assessed through the comparison of rbcL gene sequences to construct a phylogenetic tree. The significance of the NRI and NTI values indicates that the phylogenetic diversity of the plant community in the area is increasing, is closely related to long-term ecological protection and environmental restoration measures, and is benefiting from local ecological protection policies and management.

It is suggested that future research should concentrate on a few pivotal areas to significantly advance conservation efforts and ecological understanding. A primary area of interest is the long-term impact of invasive species management on native ecosystems, which can inform more sustainable and effective control strategies. Another crucial direction is the exploration of native species’ genetic diversity and their adaptive potential in the context of biological invasions, shedding light on how to bolster the resilience of native flora and fauna. Lastly, the development of post-invasion ecosystem restoration strategies is essential, aiming to not only reverse the damage caused by invasive species but also to enhance the overall biodiversity and health of the affected habitats. By prioritizing these research directions, we can make substantial strides towards a more comprehensive and proactive approach to biodiversity conservation.

Based on biodiversity survey research, we suggest enhancing the systematicity of conservation strategies as follows: Firstly, establish a coordination mechanism among multiple stakeholders, including government agencies, research institutions, local communities, and non-governmental organizations, to collaboratively advance plant diversity conservation. An interdisciplinary conservation strategy encompassing ecology, botany, climatology, and sociology should be developed. We can utilize geographic information systems (GISs) and biodiversity models to identify key ecological zones within the park, setting priorities for plant diversity conservation. Secondly, institute a resource monitoring system by deploying biodiversity monitoring stations throughout the park to gather data on plant species, population sizes, and distributions. We should employ unmanned aerial vehicles (drones) and remote sensing technology for extensive vegetation monitoring to evaluate ecosystem health and train a dedicated team for data collection, management, and analysis. Thirdly, refine legal and regulatory frameworks by reviewing and updating regional plant protection regulations for alignment with national laws, increasing penalties for violations to strengthen legal deterrence, and collaborate with local communities to formulate conservation plans that ensure effective law enforcement. Fourthly, elevate public engagement through educational initiatives such as park guide training, school programs, and public seminars to raise awareness about plant diversity conservation. We can leverage social media and mobile apps to encourage public participation in monitoring and protecting plant diversity and establish volunteer programs that involve the public in habitat restoration and invasive species management within the park. Lastly, it is possible to bolster the execution of conservation actions by devising detailed action plans that outline both short-term and long-term goals, along with the specific steps to achieve them.