Study on Diversity of Poisonous Weeds in Grassland of the Ili Region in Xinjiang

Abstract

The frequent occurrence of poisonous grassland weed disasters has weakened the stability of the grassland ecosystem in the Ili region of Xinjiang, and its spread has seriously affected the development of grassland animal husbandry. However, there is no relevant literature to report the species and distribution of poisonous grassland weeds in the Ili region. In this study, investigation was carried out using methods such as personal inspection and sampling methods, and importance-value and diversity analyses were conducted. The results showed that there were 126 species of poisonous weeds in the Ili region, belonging to 91 genera and 28 families. The poisonous weeds of Compositae and Leguminosae accounted for 33.3%. The Shannon–Wiener diversity index of the poisonous weed population was 3.99, the richness of the poisonous weed population was high, and the distribution range was uniform. The Simpson diversity index of poisonous weeds population was 0.97, and the highest importance value of poisonous weeds was Urtica cannabina L., with an importance value of 11.50. The evenness index of the poisonous weed population was 0.83; the spatial distribution pattern of the poisonous weed population tended to aggregate distribution. This study lays a foundation for the control of poisonous weeds and the sustainable development of grasslands in the Ili region of Xinjiang.

1. Introduction

The poisonous weeds can be divided into toxic and harmful varieties. Poisonous weeds are weed types that when ingested or touched by humans or animals, introduce poisonous substances into the body, causing symptoms such as vomiting, fainting, death, or damage to bodily functions. Harmful weeds are mostly plants that have sharp, thorn-like structures on the plants themselves or their seeds, causing physical damage when touched by humans or animals. Poisonous weeds also include invasive foreign weeds that proliferate extensively in grasslands, leading to the widespread extinction of native plants and causing serious damage to the biodiversity of the grassland.

The occurrence of poisonous weeds can be traced back to the early 19th century. After a prolonged period of development and evolution, poisonous weeds ran rampant on grasslands in various countries. Overseas, poisonous weeds were primarily distributed in countries such as the United States, Russia, Morocco, Canada, Egypt, Spain, Iceland, Mexico, and others. In 1873, the United States first reported incidents of livestock poisoning due to the ingestion of poisonous weeds, and similar incidents were later discovered in the state of Colorado [1]. In 1883, the state of Kansas in the United States witnessed the most significant incident of livestock poisoning caused by poisonous weed ingestion in history, with approximately 2500 head of cattle poisoned and 1600 head of cattle dead. Subsequently, from 1920 to 1950, the United States reported several severe poisoning incidents that significantly impacted the development of the livestock industry [1,2]. The variety of poisonous weed species was abundant globally, with over 800 species in American grasslands, over 750 species in Russian grasslands, over 430 species in Australian grasslands, and over 130 species in Brazilian grasslands [1]. There were many varieties of poisonous weeds, and they were highly abundant in grasslands across various countries. Extensive research indicates that there were over 800 species of poisonous weed in American prairies [3]. The grasslands of Russia hosted over 750 species of poisonous weeds [4]. The grasslands of Australia are home to over 430 species of poisonous weeds. The grasslands of Brazil harbor over 130 species of poisonous weeds [5,6].

Every year, countries lose hundreds of millions of dollars in economic losses due to poisonous weeds, and the number of losses is rising. In EU countries, there are about more than a dozen species of poisonous weeds that poison livestock with high frequency, and the propagation and spread of poisonous weeds have caused huge economic losses for animal husbandry around the world [7]. According to statistics, the direct economic loss for animal husbandry caused by poisonous weeds in South Africa is 24 million US dollars per year [8], and the direct economic loss to animal husbandry caused by poisonous weeds in the United States is 503 million US dollars per year [9]. In addition to the direct losses of livestock death, abortion, chronic disease, and weight loss, poisonous plants also cause a range of indirect losses, including increased input for fencing and supplementary feed, increased spending on herbicides and livestock treatments, and reduced production and use of grassland forage [3,10,11].

In China, there are over 1300 species of poisonous weeds in grasslands, with a concentration of poisonous varieties in the legume, weeds, Euphorbiaceae, Rhododendron, Solanaceae, and Liliaceae families. The poisonous weeds are mainly distributed in the grasslands of Xinjiang, Tibet, Gansu, Sichuan, Qinghai, Ningxia, Yunnan, and other provinces and regions in China, posing a threat to an area of approximately 33 million hectares. Among them, the poisonous weeds known as Oxytropis DC and Stellera L. have the greatest impact, accounting for over 90% of the total area affected by poisonous weeds [12,13,14,15]. In Xinjiang, the diversity of poisonous weed species is high, and the damage caused by them is severe. There are a total of 257 species from 167 genera and 45 families of poisonous weeds in Xinjiang grasslands. Among these, 81 species from 54 genera and 24 families are commonly encountered and pose significant harm, the main dominant poisonous weeds in Xinjiang include the following species: Achnatherum inebrians (Hance) Keng ex Tzvelev, Aconitum soongaricum (Regel) Stapf, Astragalus variabilis Bunge ex Maxim., Oxytropis glabra (Lam.) DC., Anabasis aphylla L., Pedicularis sylvatica L., and Stellera chamaejasme L.. The spread of poisonous weeds has caused significant economic losses for Xinjiang’s livestock industry [16,17,18]. In 1980, it was reported that approximately 3000 livestock animals died in Bayingolin Mongol Autonomous Prefecture due to ingestion of poisonous weeds [19]. Between 2000 and 2011, 35,000 livestock in Xinjiang died due to the ingestion of poisonous weeds [20]. In 2008, 1291 cattle in the Altay region of Xinjiang died from poisoning after ingestion of poisonous weeds. In 2014, the Altay region experienced a severe drought that caused significant damage to the livestock industry. This led to the serious spread of poisonous weeds in the vicinity of Xiayu Ranch in Fuyun County, with the affected area reaching 800 hectares. Over a hundred livestock, driven by hunger, died from ingesting poisonous weeds, resulting in a cumulative loss of 170,000 US dollars. In the same year, the locust control department in the Tacheng region surveyed livestock deaths caused by grazing on poisonous weeds. It was found that a total of 194 livestock died across the entire region, resulting in direct economic losses of nearly 280,000 US dollars.

Frequent outbreaks of poisonous weed disasters in grasslands have weakened the stability of the grassland ecosystem, impacting the development of grassland animal husbandry, reducing the income of farmers and herders, and posing a serious threat to the social development and stability of Xinjiang’s grassland areas. If the spread of poisonous weeds is not effectively controlled, the grasslands may gradually degrade into desertified areas, significantly weakening the carrying capacity of the grassland. Xinjiang’s grassland ecosystem, already fragile due to arid conditions, is in urgent need of protection for sustainable development. Controlling and preventing the spread of poisonous weeds in the grasslands must be prioritized. Otherwise, deaths from plant poisoning can be a heavy financial burden to livestock farmers Therefore, a comprehensive survey of poisonous weeds in the grasslands is imminent [21,22,23,24,25]. This study employed field surveys, plot investigations, and other methods to investigate and analyze the importance value, and diversity of poisonous weeds. It identified the types, distribution, and degree of harm caused by poisonous weeds in the Ili region. A systematic assessment of the occurrence and current status of poisonous weeds was conducted, providing a scientific theoretical basis for the prevention and control of poisonous weeds and the sustainable development of grasslands.

2. Materials and Methods

2.1. Research Methods

2.1.1. Field Survey

Before conducting field surveys from March 2022 to April 2022, we reviewed historical archives from the local department responsible for the prevention and control of harmful organisms on the grasslands. We purposefully visited or consulted with local farmers, herders, and grassland workers to understand the types, distribution, cycles of occurrence, and situations of poisonous weeds in the local grasslands. This preparation was undertaken to design effective routes for field surveys.

During the field surveys from April 2022 to October 2023, guided by the harm caused by poisonous weeds in grasslands, we traced harmful organisms by identifying the associated damages. Through the line investigation, we observed the occurrence and overall distribution of poisonous weeds in the grasslands. By establishing sample plots, we further determined the types, frequency, population density, plant coverage, and distribution of poisonous weeds.

Route Planning

Taking each county in Ili Prefecture as a unit, the survey route was planned according to the distribution of local grassland resources, topography, and grassland type. Special emphasis was given to areas heavily impacted by human activities, experiencing severe grassland degradation, or facing adverse ecological conditions. Priority was given to regions historically prone to the occurrence of poisonous weeds in grasslands. The survey routes were designed to be representative, avoiding duplication, and encompassing all counties, cities, and grassland types in the local area.

Under normal circumstances, when the local grassland area was less than 200,000 hectares, the surveyed area for the route should be no less than 3% of the local grassland area. For grassland areas ranging from 200,000 to 500,000 hectares, the surveyed area should be no less than 2.5% of the local grassland area. If the grassland area exceeds 500,000 hectares, the surveyed area should be no less than 2% of the local grassland area.

Refer to the Implementation Plan of Pest Census in Guiyang Grassland and the Regulation of Poisonous Weeds in Grassland DB 63/T241-2021 [26,27].

2.1.2. Plot Survey

During the field survey, when encountering harmful effects caused by poisonous weeds, known areas where poisonous weeds occur, or the discovery of invasive or locally first-found types of poisonous weeds, standard plots were established for detailed investigation.

Requirements for Plot Establishment

All grasslands that met the conditions for the plot establishment were required to have plots set up. For each grassland type, at least one plot was to be established, and the area for each plot was to be 0.5 hectares.

Under normal circumstances, when the grassland area was less than 65,000 hectares, the cumulative area of the sample plots was required to be no less than 0.3% of the local grassland area. For grassland areas ranging from 65,000 to 200,000 hectares, the cumulative area of the sample plots was required to be no less than 0.25% of the local grassland area. If the grassland area exceeded 200,000 hectares, the cumulative area of the sample plots was required to be no less than 0.2% of the local grassland area.

Further information can be found in the Implementation Plan of Pest Census in Guiyang Grassland and the Regulation of Poisonous Grass in Grassland DB 63/T241-2021.

Sample Plot Survey Methods

Using the plot method for the survey, each herbaceous plot had an area of 1 m², and each shrub plot covered 25 m². The survey within each plot included recording the types of poisonous weeds, density (plants/m²), coverage (%), latitude and longitude, and grassland types, and collecting image photos. The average density, average coverage, and average plant height for each type within each standard plot were calculated and recorded.

2.2. Survey Subjects and Content

The survey focused on poisonous weeds with documented records of causing harm to grassland ecology or livestock; those that caused harm locally but were not yet documented; and invasive poisonous weed species. The main aspects of the investigation included the types of poisonous weeds, density (plants/m²), coverage (%), methods of harm, grassland types, and distribution range.

2.3. Data Statistical Analysis

2.3.1. Species of Poisonous Weeds

On a county-by-county basis, the types of poisonous weeds in different regions were identified through the observation of plant morphological characteristics. I scientific classification, genera, and species of the poisonous weed populations in the Ili region were summarized.

More information can be found in ‘Main Types and Distribution of Poisonous Weeds in Western China’s Natural Grasslands’, ‘Techniques for the Prevention and Control of Livestock Poisoning by Natural Grassland Poisonous Weeds’ [28,29].

2.3.2. Analysis of the Composition Characteristics and Importance Values of Poisonous Weeds

Importance value (IV) is a comprehensive quantitative indicator used to represent the status and role of a species in a community. It provides an objective and comprehensive reflection of the position of the plant species in the community and its impact on the entire community [30,31,32].

• Importance Value (IV) = [Relative Abundance (Dr) + Relative Coverage (Pr) + Relative Frequency (Fr)]/3;
• Relative Abundance (Dr) = Number of individuals of a particular species/Total number of individuals of all species × 100%;
• Relative Coverage (Pr) = Coverage of a particular species/Sum of coverages of all species × 100%;
• Relative Frequency (Fr) = Frequency of a particular species/Total frequency of all species × 100%.

2.3.3. Species Diversity of Poisonous Weeds Populations

Diversity indices, also known as heterogeneity indices, are comprehensive indicators reflecting richness and evenness. In this paper, commonly used indices, including the species richness index, Pielou’s evenness index, and a diversity index, are selected for calculation [33,34,35].

• Species richness (S) = The number of species present in the sample plots;
• Shannon–Wiener Diversity Index H′ = −${\sum }_{(i=1)}^{\mathrm{S}}Pi lnPi$;
• Simpson Diversity Index D = 1 − ${\sum }_{(i=1)}^{\mathrm{S}}{Pi}^2$;
• Pielou’s Evenness Index Jsw = H′/lnS

In the equation: Pi = Ni/N, where Ni is the abundance of species i, N is the total abundance of all species in the plot; numerically equal to Dr.

2.3.4. Spatial Distribution Pattern of Poisonous Weeds Populations

The method of variance-to-mean ratio, based on the assumption of a Poisson distribution, relies on the property that for a Poisson distribution, the variance (V) is equal to the mean (m), i.e., V/m = 1. If V/m > 1, the population deviates from a Poisson distribution and exhibits an aggregated distribution. Conversely, if V/m < 1, it indicates a uniform distribution. The calculation methods for V and m are as follows:

$$\mathrm{V}={\sum }_{i=1}^{\mathrm{N}}{ (\mathrm{X}\mathrm{i}-\mathrm{m})}^2/(\mathrm{N}-1)$$

$$\mathrm{V}=1/\mathrm{N}{\sum }_{i=1}^{\mathrm{N}}\mathrm{X}\mathrm{i}$$

where N is the number of sample plots and Xi is the number of individuals in each sample plot. To test whether the observed samples accept the expected hypothesis, a t-test is conducted using [2 − (N − 1)] ^1/2 as the standard deviation. Subsequently, a significant test is carried out by examining the t-distribution wit– N − 1 degrees of freedom and a 95% confidence level [36,37,38].

t = (−/M − 1) [2 − (N − 1)]^1/2

(1)

2.3.5. Vigor of Dominant Poisonous Weeds

We selected the poisonous weed populations with high importance values, calculating the average density, average coverage, and average plant height for different poisonous weed populations to express the growth status of poisonous weeds.

3. Results

3.1. Composition of Poisonous Weeds

A total of 156 lines covering an area of 28,979 hm² were created in the Ili region, a total of 1099 inspection points were created, 3659 poisonous weeds were investigated, 791 standard sites were created, and the occurrence times of poisonous weeds were investigated 767 times.

Table 1. The poisonous weed species in the grassland of the Ili region in Xinjiang.

Family Name	Genus Number	Species Number	Family Name	Genus Number	Species Number
Asteraceae	19	24	Apiaceae	2	2
Fabaceae	9	18	Zygophyllaceae	2	2
Labiatae	7	7	Thymelaeaceae	2	2
Ranunculaceae	6	10	Urticaceae	1	3
Chenopodiaceae	6	9	Caryophyllaceae	1	2
Brassicaceae	5	5	Euphorbiaceae	1	2
Rosaceae	4	5	Ephedraceae	1	2
Orobanchaceae	3	5	Valerianaceae	1	1
Poaceae	3	5	Campanulaceae	1	1
Liliaceae	3	3	Berberidaceae	1	1
Papaveraceae	3	3	Onagraceae	1	1
Polygonaceae	2	5	Boraginaceae	1	1
Gentianaceae	2	3	Moraceae Gaudich	1	1
Solanaceae	2	2	Convolvulaceae	1	1

shows that the Ili Region has a total of 126 species of poisonous weeds, belonging to 28 families and 91 genera. Among them, the Asteraceae family has the highest number with 24 species of poisonous weeds, followed by the Fabaceae family with 18 species, the Ranunculaceae family with 10 species, the Chenopodiaceae family with 9 species, the Lamiaceae family with 7 species, and the Chenopodiaceae, Rosaceae, Scrophulariaceae, Brassicaceae, and Poaceae families each having 5 species of poisonous weeds. The remaining 18 families have only 1–3 species of poisonous weeds each.

3.2. The Composition Characteristics and Importance Values of Poisonous Weeds

Different grassland types have distinct climates and environmental conditions, leading to variations in the types and importance of poisonous weeds. Table S1 shows that in the Ili region, there are a total of 126 species of poisonous weeds. In the temperate desert steppe, there are 19 species of poisonous weeds, with Carduus nutans L. being the dominant species with an importance value of 16.01. Other dominant species include Peganum harmala L., Alhagi camelorum Fisch., and Urtica cannabina, with importance values of 15.09, 14.95, and 13.12, respectively; In the temperate meadow steppe, there are 91 species of poisonous weeds, with Aconitum leucostomum Vorosch. being the dominant species with an importance value of 12.38. Other dominant species include Urtica cannabina, Achnatherum inebrians, Sophora alopecuroides L., Cannabis sativa L., and Carduus nutans, with importance values of 11.59, 8.16, 7.87, 6.82, and 5.92, respectively; In the alpine typical steppe, there are 77 species of poisonous weeds, with Urtica cannabina being the dominant species with an importance value of 10.62, followed by Carduus nutans with an importance value of 5.21; In the alpine meadow steppe, there are 95 species of poisonous weeds, with Aconitum leucostomum being the dominant species with an importance value of 14.10, followed by Urtica cannabina with an importance value of 10.82.

3.3. The Species Richness and Diversity of Poisonous Weeds Populations

3.3.1. Analysis of Species Richness in the Population of Poisonous Weeds

Figure 1 shows that in the Ili region, there are a total of 126 species of poisonous weeds. Among them, the alpine meadow steppe has the highest number of poisonous weed species, reaching 95. Following that, the temperate meadow steppe has 91 species of poisonous weeds, while the Temperate Desert Steppe has the least variety with 19 species.

3.3.2. The Analysis of Shannon–Wiener Diversity Index (H′) in the Population of Poisonous Weeds

The Shannon–Wiener diversity index (H′) is an index used to assess the richness and evenness of a community, with higher values indicating higher species richness and more even distribution. Figure 2 shows that in the Ili region, the diversity index of poisonous weeds is 3.99. Among the different grassland types, the alpine meadow steppe has the highest diversity index of 3.90, followed by the alpine typical steppe with a diversity index of 3.6. The temperate desert steppe has the diversity index of poisonous grasses the lowest at 2.6.

3.3.3. The Analysis of Simpson Diversity Index (D) in the Population of Poisonous Weeds

The Simpson diversity index (D) is an index used to evaluate a community’s diversity, with lower values indicating higher dominance of a particularly poisonous weed species and importance values being higher. Figure 3 shows that in the Ili region, the diversity index of poisonous weeds is 0.97. Among different grassland types, the alpine meadow steppe has the highest diversity index of 0.97, followed by the alpine typical steppe with a diversity index of 0.96. The temperate desert steppe has the lowest diversity index, measured at 0.91. The dominance index of Urtica cannabina is the highest at 11.50, while the dominaIce indices of Aconitum leucostomum and Achnatherum inebrians are similar, indicating relatively low dominance for the most dominant species.

3.3.4. The Analysis of Pielou’s Evenness Index (Jsw) in the Population of Poisonous Weeds

Pielou’s evenness index (Jsw) is an index used to evaluate the evenness of a community, with higher values indicating higher evenness. Figure 4 shows that in the Ili region, Pielou’s evenness index (Jsw) for poisonous weeds is 0.83. Among different grassland types, the temperate desert steppe has the highest evenness index for poisonous weeds at 0.88, followed by the high–cold meadow grassland with an evenness index of 0.86. The evenness index for poisonous weeds is lowest in the temperate meadow steppe, measured at 0.75.

3.4. The Spatial Distribution Pattern of the Poisonous Weeds Population

Table 2. The spatial distribution pattern of poisonous weeds in the grassland of the Ili region in Xinjiang.

Grassland Types	Variance	Mean Value	Variance/Mean Value	ResuI
The Ili region	9.12	3.11	2.93	aggregated distribution
Temperate desert steppe	5.33	2.42	2.20	aggregated distribution
Temperate typical steppe	7.62	3.06	2.49	aggregated distribution
Temperate meadow steppe	9.83	3.21	3.06	aggregated distribution
Alpine typical steppe	20.53	3.71	5.53	aggregated distribution
Alpine meadow steppe	5.60	2.93	1.91	aggregated distribution

shows that in the survey, the overall spatial distribution pattern of poisonous weed populations in the Ili region tends to be clustered.

3.5. The Growth Status and Distribution Range of Dominant Poisonous Weeds

Table 3. The growth state of dominant poisonous weeds in grassland of the Ili region in Xinjiang.

Poisonous Weed Species	Average Density (Plants/m2)	Average Coverage (%)	Average Height (cm)
Cannabis sativa	6.19 ± 3.16	46.27 ± 29.20	37.32 ± 24.72
Salvia deserta Schangin	4.98 ± 2.75	35.54 ± 21.34	55.37 ± 21.26
Sophora alopecuroides	4.37 ± 2.88	43.93 ± 28.03	53.38 ± 33.23
Achnatherum inebrians	3.68 ± 2.31	39.17 ± 24.96	65.88 ± 32.21
Urtica cannabina	3.66 ± 2.23	63.35 ± 27.46	93.58 ± 39.36
Phlomoides umbrosa (Turcz.) Kamelin & Makhm	3.55 ± 1.52	33.51 ± 23.81	52.33 ± 19.29
Carduus nutans	1.89 ± 0.64	35.31 ± 4.63	61.14 ± 37.51
Rumex acetosa	1.58 ± 0.58	35.68 ± 26.95	99.97 ± 39.91
Onopordum acanthium L.	1.52 ± 0.59	38.73 ± 23.95	89.22 ± 38.80
Aconitum leucostomum	1.51 ± 0.74	42.51 ± 26.07	60.39 ± 32.81

Note: $\overline{x}$ ± s symbol the mean value ± the standard error of mean.

shows that in a unit area of 1 m², the average density of dominantly poisonous weeds in the Ili region is highest for Cannabis sativa at 6.19 plants/m², followed by Artemisia sieversiana at 4.98 plants/m². The average cover of Urtica cannabina is highest at 63.35%, followed by Cannabis sativa at 46.27%. The average height of Rumex acetosella L. is highest at 99.97 cm, with Urtica cannabina ranking second at 93.58 cm.

According to the survey, Onopordum acanthium is mainly distributed in the grasslands of Yining County, Gongliu County, and Zhaosu County; Cannabis sativa is mainly distributed in the grasslands of Huocheng County and Nileke County; Salvia deserta is mainly distributed in the grasslands of Zhaosu County and Tekes County; Aconitum leucostomum is mainly distributed in the grasslands of Huocheng County, Xinyuan County, and Tekes County; Phlomoides umbrosa (Turcz.) Kamelin & Makhm. is mainly distributed in the grasslands of Zhaosu County and Tekes County; Sophora alopecuroides is mainly distributed in the grasslands of Huocheng County; Rumex acetosella is mainly distributed in the grasslands of Zhaosu County and Nileke County; Achnatherum inebrians is mainly disIributed in the grasslands of Huocheng County, Xinyuan County, and Zhaosu County; Carduus nutans is mainly distributed in the grasslands of Huocheng County; Urtica cannabina is mainly distributed in the grasslands of Huocheng County, Yining County, Zhaosu County, and Nilekounty.

4. Discussion

The Ili region benefits from a superior natural environment, a humid climate, ample water supply, relatively low soil desertification, and a large grassland area. Consequently, it harbors a diverse range of poisonous weed species with relatively high diversity indices and favorable community richness and evenness. In the high-altitude meadow grassland, the conducive growth environment leads to a higher variety of poisonous weed species, resulting in a relatively high diversity index. In temperate typical steppes, the ecological environment is mainly influenced by water resources, and the abundance of water in the Ili region contributes to a relatively rich variety of poisonous weed species, with dominance values lower and diversity indices higher. In temperate desert steppes, where land resources are generally poor, only a few drought-resistant poisonous weeds can thrive, resulting in a lower diversity index. While the poisonous weed distribution is relatively even in temperate desert steppes and high-altitude meadow grasslands, the overall distribution uniformity is lower when considering all five types of grasslands. This non-uniform distribution is attributed to uneven water and land resource distribution, leading to an aggregated distribution pattern of poisonous weed populations. In temperate meadow steppes and high-altitude meadow grasslands, overgrazing and the long interval between rotational grazing on summer and winter pastures exacerbate that grassland degradation, ultimately causing an uneven distribution trend of poisonous weed populations, leaning towards aggregaIion.

The Ili region possesses unique geographical, environmental, and climatic characteristics, and its distinctive natural resources determine the specificity of grassland ecological conservation and livestock economic development. While striving for economic growth in pastoral livestock, it is crucial to concurrently focus on the protection of the grassland’s ecological system [26,39]. By optimizing the physical, chemical, and biological control methods for grassland poisonous weeds, addressing the balance of livestock-carrying capacity and agricultural–pastoral equilibrium, implementing grassland restoration through returning cultivated land to pasture, improving the quality of the grassland ecological compensation mechanism, and continuously enhancing the natural recovery capabilities of grasslands while employing artificial restoration methods, it is possible to address the ongoing degradation of the grassland ecological environment. This approach aims at achieving sustainable development for the grasslands [26,40,41,42].

Zhao Baoyu et al. introduced the situation, species, distribution, comprehensive control, and rational utilization of the poisonous weeds in the grasslands of western China in recent decades [15]. This article clarified the dominant poisonous weed species and their approximate range in the Ili region, providing valuable data support for the control of harmful organisms in the grasslands of the Ili region. A proper understanding of the ecological role of poisonous plants is crucial. From a grassland ecology perspective, poisonous plants are vital components of natural grassland ecosystems, holding significant and distinctive importance in preventing further degradation of grasslands under harsh climatic conditions. Poisonous plants are not dispensable within plant communities; they occupy specific ecological niches, influencing other plant populations in the community and being influenced by them. Together, they collectively maintain the stability of the community. In comparison with other plant species, poisonous plants possess characteristics such as drought resistance, cold resistance, pest resistance, wind and sand tolerance, and robust vitality. They play a critical ecological role in preventing wind erosion, stabilizing dunes, mitigating soil erosion, and safeguarding grassland vegetation. In addition, it is crucial to shift our perspective and scientifically assess the relationship between the benefits and harm of poisonous weeds, fostering the concept of “turning harm into benefit”. Some poisonous weeds are nutritionally rich and can be directly fed to stock after control, detoxification, or ensiling. Some, being of beautiful appearance, can be developed for ornamental purposes, contributing to the development of grassland tourism. Others have medicinal properties and can be explored for their pharmaceutical value, such as Urtica fissa E. Pritz., Peganum harmala, Sophora alopecuroides, and Cirsium spicatum Matsum. However, it is essential to clarify the medicinal value and usage methods of each poisonous weed, providing an alternative for herders to increase income and realize the comprehensive utilization of poisonous weeds.

5. Conclusions

This study identified the poisonous weed species and their importance values, diversity, and spatial distribution patterns, and ascertained the dominant poisonous weed species and the growth range of dominant poisonous weeds in the Ili region.

• In the Ili region, there are a total of 126 species of poisonous plants, belonging to 28 families and 91 genera. Among them, the Asteraceae family has the highest number of poisonous plants, with 24 species; the Fabaceae family has 18 species; the Ranunculaceae family has 10 species; the Amaranthaceae family has 9 species; and the Lamiaceae family has 7 species. These five families account for 61% of the total.
• The Shannon–Wiener index (H′) is highest in the alpine meadow steppe, reaching 3.90, while the other four types of grasslands have Shannon–Wiener indices (H′) ranging from 2.60 to 3.60. Overall, the community richness and evenness in the Ili region is relatively good.
• The Simpson index (D) is highest in the alpine meadow steppe, reaching 0.97, while the Simpson indices (D) for the other four types of grasslands range from 0.91 to 0.96. The environment of suitable growing in the alpine meadow steppe contributes to a greater variety of poisonous weed species, resulting in a relatively high Simpson diversity index (D) for poisonous weeds.
• The evenness index (Jsw) is highest in the temperate desert steppe, reaching 0.88, while the evenness indices (Jsw) for the other four types of grasslands range from 0.75 to 0.86. Although the poisonous grassland area is relatively large in the Ili region, with a relatively uniform distribution in the temperate desert steppe and alpine meadow steppe, when considering all five grassland types together, the evenness of poisonous weeds distribution in the Ili region is relatively low.
• The overall spatial distribution pattern of poisonous weeds populations in the Ili region tends to be aggregated.
• In the Ili region, Huocheng County, Zhosu County, Xinyuan County, Tekesi County, and Nileke County are particularly affected by the harmful presence of poisonous weeds. In these five areas, poisonous weeds occupy a significant amount of growing resources, severely restricting the growth of forage and the grazing of livestock, leading to a continuous decline in the annual income of the pastoralists.