Interannual Variation in Poisonous Plant Assemblages on Central Kazakhstan Pastures Across Landscapes Under Contrasting Hydroclimatic Conditions

Abstract

Pasture ecosystems provide essential ecosystem services, yet poisonous plants create persistent veterinary and economic risks. We examined how hydroclimatic variability restructures the poisonous-plant assemblage across three Central Kazakhstan rangelands during an extremely dry year (2023) and an exceptionally wet year (2024). A total of 32 toxic vascular plant species were recorded. Xeromorphic pastures maintained a stable floristic core across years, whereas the wet year triggered recruitment of wet-associated poisonous taxa (hydrophytic/hygrophytic group) exclusively in the Nura River floodplain and increased species richness. Thus, interannual variability was controlled by hydrologically sensitive habitats rather than wholesale community turnover. The principal grazing hazard was associated with flood-related species (e.g., Cicuta virosa, Oenanthe aquatica) and persistent forage contaminants (Datura/Hyoscyamus, Lolium temulentum). These findings indicate that toxic-plant risk follows an asymmetric seasonal pattern: episodic post-flood hazard in floodplains combined with constant background risk in steppe pastures. Therefore, grazing management should integrate event-based monitoring of wet habitats with continuous forage-quality control.

1. Introduction

Pasture ecosystems (rangelands) play a central role in sustainable agriculture and global environmental stability: they cover roughly half of the Earth’s land surface, represent a major carbon reservoir, support biodiversity, and underpin rural livelihoods [1,2]. These ecosystems provide a wide range of services, including soil carbon sequestration, erosion control, regulation of water balance, and contributions to food security [3,4]. In many agricultural regions worldwide, rangelands shape both the landscape and the rural economy, linking food security with the conservation of natural capital [5].

Alongside these well-recognized benefits, however, there is a serious and ubiquitous challenge: the presence of poisonous plants on grazing lands that can cause disease and death in livestock. Plants produce a broad spectrum of defensive metabolites (alkaloids, glycosides, cyanogenic compounds, etc.), which, when ingested, can result in intoxication and substantial economic losses [6,7]. The economic impacts include both direct losses (mortality, abortions, reduced milk yield and product quality) and indirect costs (treatment, removal of toxic species, supplemental feeding, and pasture degradation) [8].

Reframing the role of secondary metabolites, it is important to recognize that species containing toxic compounds are a natural component of herbaceous communities, and that these metabolites serve multiple ecological functions rather than being limited to anti-herbivore defense. Accordingly, rangeland management should prioritize stocking-rate control and risk monitoring (integrated management), rather than defaulting to “total eradication” as a universal approach [9,10].

Global syntheses indicate considerable diversity of toxic plants across rangelands in different regions. For the United States and Canada, more than one hundred plant species associated with livestock poisoning have been described, and in Australia, a priority list includes approximately 119 grazing-relevant species [11,12]. In Europe, plant poisonings in domestic animals are a recurring phenomenon; species from the genera Senecio, Quercus, Taxus (T. baccata), Nerium (N. oleander), Pteridium (P. aquilinum), among others, are most frequently implicated [13].

Kazakhstan is part of Central Asia, which in contemporary geographic and political usage comprises five countries: Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan [14]. Across Central Asia, a substantial body of evidence has accumulated on biodiversity patterns and the risks posed by poisonous pasture plants. In Uzbekistan, research on the desert rangelands of the Kyzylkum has shown that the pasture flora includes at least 73 poisonous species (predominantly xerophytes), identified through long-term monitoring in 2012–2024 [15]. In Kyrgyzstan, the presence and distribution of poisonous species on mountain and foothill pastures are documented in specialized reviews and practical guides as well as in the scientific literature; a foundational regional reference remains a comprehensive monograph on weedy and poisonous plants of Kyrgyz pastures and control measures [16]. For Tajikistan, a synthesized checklist includes at least 269 poisonous species belonging to 44 genera and 21 families, underscoring the high regional diversity of toxic taxa in the country’s mountain–desert landscapes [17]. In Turkmenistan, poisonous rangeland plants have been treated in monographic detail, with an emphasis on their effects on livestock and on preventive measures against phytotoxicoses [18].

Kazakhstan ranks among global leaders in rangeland area: it has more than 186 million ha, representing 84.1% of the country’s agricultural land [19]. The effects of grazing and climatic variability on Kazakhstan’s dryland vegetation are well documented: approximately 45.7% of the country has exhibited degradation trends, with major contributions from land-use change (including grazing regimes), variability in snow cover, and broader climatic drivers [20]. Central Kazakhstan (Saryarka), including transitional zones toward semideserts, is characterized by a sharply continental climate (cold winters, hot and dry summers, and low precipitation totaling approximately 100–300 mm·year⁻¹) and encompasses a spectrum of ecosystems—from fescue–feathergrass steppes dominated by Stipa spp. and Festuca spp. to dry semidesert rangelands [21]. The floristic structure of Central Kazakhstan steppes—featuring a leading role of tussock-forming grasses and Artemisia spp.—is consistent with syntheses on the Palearctic steppe biome and Eurasian steppes [22,23].

Against the backdrop of increasing anthropogenic pressure and climate variability, monitoring and sustainable rangeland management have become priorities; this is supported by regional studies from Central/Northern Kazakhstan and targeted work within the Ulytau area [24,25]. Despite the scale of Kazakhstan’s rangeland resources, the diversity of poisonous pasture plants in Central Kazakhstan remains only fragmentarily studied; targeted studies addressing geographic drivers and the distribution of toxic species in Kazakhstan have begun to emerge only in recent years [26].

The aim of this study was to document the biodiversity of poisonous vascular plants (including their assignment to moisture groups) across three representative rangelands of Central Kazakhstan and to assess how species richness and group composition differed among sites, as well as between an extreme drought year (2023) and a year with extremely wet conditions (2024).

2. Materials and Methods

2.1. Study Rangelands

In this study, we surveyed three focal rangeland sites in Central Kazakhstan: the Karkaraly Mountains (KK), the Nura River floodplain (NF), and the Ulytau foothills (UF). These areas were selected as the region’s largest and most intensively used pasture systems, while also capturing the principal orographic and hydrological gradients of the steppe zone: granite hills of the forest–steppe belt, the alluvial floodplain of the main river in the Nura Basin, and dry-steppe foothills of the Ulytau Massif.

Field surveys were conducted during the main growing season in both study years (2023 and 2024), with one standardized survey campaign per month in June, July, and August at each of the three rangelands. This design was intended to capture the principal phenological phases relevant to pasture conditions and livestock exposure while ensuring comparability among sites and years. Accordingly, the study focuses on the poisonous plant assemblage recorded during the main grazing-relevant period rather than on complete seasonal floristic inventories.

Each rangeland was represented by a working polygon with a 10 km radius (≈310–320 km²), providing sufficient coverage of pastures of different ages, areas subject to varying anthropogenic pressure, and a microlandscape mosaic suitable for repeated route-based surveys within a single field season. This combination of spatial scale and ecological contrast enabled us to compare floristic stability and the structure of poisonous-plant assemblages across the most heavily utilized steppe rangelands (Figure 1).

At each pasture site, three linear radial transects were established, all originating from a single central reference point. The transects were arranged in a fan-shaped configuration with equal angular spacing (0°, 120°, and 240°) and extended 5 km from the center. This radial design was used to capture spatial heterogeneity and hydrological gradients within each site, particularly the transition from central low-lying zones to peripheral, better-drained areas (Figure 1).

Along each radial transect, permanent sampling points were placed at regular 250 m intervals, resulting in 20 points per transect and 60 points per site in total. Each sampling point was assigned a unique code (T1P01–T1P20, T2P01–T2P20, and T3P01–T3P20) and georeferenced using a handheld GPS receiver. At each point, vegetation surveys were conducted within a 4 m wide belt centered on the transect line, where all toxic plant species were recorded and their relative cover was estimated using the semi-quantitative abundance scale (Un, Sol, Sp, Cop1–Cop3) [27,28,29].

The rangeland was treated as the primary unit of ecological inference, while individual sampling points were considered detection replicates used to stabilize estimates of species occurrence and cover frequency within each pasture. Therefore, point-level variability was not interpreted as independent community samples but as subsamples of a single landscape-scale assemblage.

Karkaraly Mountains (KK). The center of the working polygon (10 km radius; area ≈ 314 km²) was shifted to the south–southwest of the town of Karkaraly and is located near 49°20′00″ N, 75°23′00″ E. Within the circle, the boundaries fall approximately within 49°14′36″–49°25′24″ N and 75°14′43″–75°31′17″ E. The polygon encompasses pasture communities of low hills and runoff depressions along the southern margin of the massif and, by shifting the center, minimizes inclusion of the urbanized area of the town, thereby ensuring that the sample is representative of natural rangeland habitats (Figure 2).

The soil cover is dominated by dark chestnut loams with granitic eluvium; stony talus occurs on ridge tops. Spring-fed streams (Karasu) and tributaries of the Tasu River typically dry up by July. On hillslopes, pine–steppe communities prevail, dominated by Stipa lessingiana with scattered clumps of Scots pine (Pinus sylvestris), whereas in the more humid depressions, meadow communities dominated by Geranium pseudosibiricum and Caltha palustris are characteristic [30,31].

Nura River floodplain (NF). The central point of the working polygon (10 km radius; area ≈ 315–320 km²) is located at 49°41′51.4″ N, 73°05′02.7″ E; the circle boundaries fall within 49°36′27.6″–49°47′15.2″ N and 72°56′42.2″–73°13′23.2″ E. The polygon encompasses the floodplain and above-floodplain terraces of the Nura River along a reach adjacent to the settlements of Karamuryn, Dariinsky, and Prostornoye, covering alluvial meadows and the adjoining pasture communities (Figure 3).

The alluvial meadow and meadow–chernozem loams of the floodplain are periodically inundated during the spring freshet; on the Nura River, snowmelt-driven peak flows typically occur in April (based on the author’s field observations). The site’s flora is characterized by a high proportion of wet-habitat species (including hygrophilous and truly hydrophytic taxa): communities dominated by Glyceria fluitans, Carex diluta, and floating buttercups (Ranunculus spp.) are prevalent, whereas colonies of Oenanthe aquatica form denser “islands” in low-velocity reaches and in oxbow lakes [32,33].

Ulytau foothills (UF). The center of the 10 km-radius circle (area ≈ 315–320 km²) is located at 48°32′05.0″ N, 66°36′13.8″ E; the polygon spans 48°26′41.2″–48°37′28.8″ N and 66°28′04.9″–66°44′22.7″ E. The area includes the foothills and piedmont (apron) plains of the Ulytau Massif, including the vicinity of the Tokseit wintering site, providing coverage of slopes, runoff gullies, and the adjacent pasture communities (Figure 4).

2.2. Temperature–Precipitation Regime in 2023–2024

The summer of 2023 in Central Kazakhstan was exceptionally hot and dry: the mean June–August air temperature in Karaganda Region exceeded the long-term average by +2.6 °C, while total precipitation reached only 59% of the norm. A pronounced moisture deficit was reported by Kazhydromet (2023 bulletin). Spring flood rise was weak due to low snow reserves [34,35].

In April 2024, anomalously high snowpack combined with frozen soils triggered large-scale flooding; water levels on rivers in several regions markedly exceeded long-term values (according to ACAPS and ECHO). Summer conditions were less hot than in 2023 and locally wetter; in June, both precipitation deficits and localized surpluses were observed across the country, with episodes of intense rainfall in northern and central regions [36,37]. In the present study, the terms “extremely dry” (2023) and “exceptionally wet” (2024) are used as comparative descriptors of the hydroclimatic contrast between the two surveyed field seasons within the two-year study period (2023–2024), rather than as a long-term climatological classification. Accordingly, all comparisons and statistical analyses in this study were performed within this two-year field dataset (2023 vs. 2024), both overall and separately for each rangeland.

2.3. Classification of Moisture-Affinity Groups and Abundance Scale

For phytocenological and bioecological analyses of poisonous-plant assemblage, we followed the framework proposed by B.A. Bykov (1957) [38]. Although developed more than six decades ago, Bykov’s moisture-affinity groups remain a standard in studies of Kazakhstan’s steppe vegetation because they directly reflect drought tolerance—the key selective pressure in continental grasslands—and are readily comparable with the functional groupings (“dry/mesic/wet”) widely used in contemporary trait-based ecology. Thus, these categories are fully compatible with modern ecological analyses. Species were assigned to five moisture-affinity groups sensu Bykov (1957) [38]—historically termed “moisture groups” in the Russian-language literature (xerophytes, xeromesophytes, mesoxerophytes, mesophytes, and a pooled wet-associated group comprising hygrophilous and truly hydrophytic taxa). To avoid confusion with the genetic meaning sometimes associated with the term moisture group in modern English-language literature, we hereafter use the neutral designation “moisture-affinity group.”

Ecological indicator-value scales were not applied in the present study because the analysis focused on a targeted subset of poisonous species and a comparative assemblage-level assessment across years and landscapes; therefore, a unified categorical moisture-affinity grouping was used for consistency.

Within this framework, five moisture-affinity groups are distinguished:

•

Xerophytes are plants optimally adapted to prolonged drought; they typically possess deep, well-developed root systems, a waxy cuticle, strongly reduced or small leaves, and thickened succulent stems that function as water reservoirs.

•

Mesophytes are species inhabiting moderately moist conditions, without pronounced morphophysiological adaptations to either water excess or water deficit; they predominate in habitats with an “intermediate” water regime.

•

Xeromesophytes are plants capable of tolerating both moderately moist and dry phases due to a plastic water balance and switchable adaptive mechanisms.

•

Mesoxerophytes are species that develop normally under relatively moist conditions but can withstand short-term drought periods through moderately expressed xeromorphic traits. Xeromesophytes and mesoxerophytes were treated as intermediate moisture-affinity groups along the xerophyte–mesophyte gradient (Bykov-type ecological grouping framework used in regional geobotanical practice). In this study, xeromesophytes denote taxa intermediate between mesophytes and mesoxerophytes (i.e., closer to mesophytes), whereas mesoxerophytes denote taxa of insufficient-moisture habitats with stronger xeric affinity (i.e., intermediate toward xerophytes). Thus, assignment was based on the relative position of each species on the moisture gradient rather than on a binary moist/dry distinction.

•

Wet-associated taxa (operational wet-end group in the present analysis) include species associated with strongly water-influenced habitats (floodplain depressions, waterlogged soils, margins of channels and shallow-water zones), including hygrophilous taxa and truly hydrophytic species. This pooled category was used for comparative categorical analysis across sites and years in order to capture recruitment of hydrologically sensitive poisonous plants under wet-year conditions. Thus, in the present study, the category should be interpreted as a broad wet-habitat affiliation group rather than a strict hydrophyte-only classification [38,39].

Species abundance was assessed using a modified Drude scale widely used in domestic geobotanical practice: Un (<0.1% cover), Sol (<1%), Sp (~1–5%), and Cop1/Cop2/Cop3 (~5–25%, 25–50%, and 50–75%, respectively) [40]. Abundance was recorded at each of the 60 sampling points within a rangeland. Site-level abundance data for each species in each year were obtained by converting ordinal Drude classes to numeric scores (Un = 1, Sol = 2, Sp = 3, Cop1 = 4, Cop2 = 5, Cop3 = 6), averaging these values across points, and rounding the result to the nearest class. For frequency summaries, we counted the number of points at which each species was recorded in each non-zero class. Percent change between seasons was calculated as Δ% = ((N_{2024} − N_{2023})/N_{2023})·100; when the denominator equaled zero, we reported the fold increase [41].

2.4. Species Identification and Toxicity Verification

Species identification and habitat characterization were performed using Flora of Kazakhstan (Vols. I–IX), which provides diagnostic characters and distributional information. The toxicological relevance of taxa was assessed based on EFSA syntheses (lists of botanical sources of substances of potential concern; reviews on pyrrolizidine alkaloids) and veterinary reviews of toxic plants affecting cattle and horses in Europe [42,43,44,45].

2.5. Statistical Analysis

To test whether moisture-affinity group distributions differed among rangelands and whether year-to-year species turnover within each rangeland was directional, we applied two exact nonparametric procedures appropriate for small samples and categorical data. The unit of analysis was the rangeland (presence/absence and the point-aggregated mean cover/abundance class), whereas sampling points served to detect species and to compute mean abundance at the rangeland level.

Association between moisture-affinity group and rangeland. For each year, we constructed a 5 × 3 contingency table (five moisture-affinity groups × three rangelands) using the number of species in each moisture-affinity group recorded at each rangeland in that year. Independence was evaluated with the Fisher–Freeman–Halton exact test, an extension of Fisher’s exact test to r × c tables [46,47]. The test was computed using 100,000 Monte Carlo permutations in R 4.3.2 (function fisher. test, option simulate. p value = TRUE).

Directional changes within rangelands. For each rangeland, we compiled paired binary vectors (presence = 1, absence = 0) for all 32 poisonous species in 2023 vs. 2024. Gains (b) and losses (c) form the off-diagonal cells of the paired 2 × 2 table. The null hypothesis b = c was tested using the exact McNemar test [48,49,50] implemented via the mcnemar.exact function in the exact2x2 package v1.7. Statistical significance was set at α = 0.05 for two-sided alternatives.

Because vegetation abundance was recorded as ordinal cover classes rather than true quantitative abundance, abundance-based diversity indices (e.g., Shannon or Simpson) were not calculated to avoid introducing artificial proportional values. Instead, exact non-parametric tests suitable for categorical ecological data were applied to evaluate redistribution among functional groups and directional species turnover at the rangeland scale.

3. Results

3.1. Poisonous Plant Species on Central Kazakhstan Rangelands: Diversity, Families, and Principal Toxic Effects

The survey identified 32 poisonous plant species belonging to 17 families. In terms of species richness, Apiaceae and Ranunculaceae predominated (wetland and riparian habitats): polyacetylenes/furanocoumarins and protoanemonin form the “wet” toxic core of floodplain sites. The “intermediate block” comprised Solanaceae, Asteraceae, Fabaceae, and Brassicaceae—predominantly ruderal and synanthropic mesophytes characterized by tropane alkaloids, sesquiterpene lactones, pyrrolizidine/indolizidine alkaloids, and glucosinolates. Less frequently encountered families (Poaceae, Euphorbiaceae, Plantaginaceae, among others) were represented by more specialized taxa that generate peak risks under specific scenarios: alkaloids in Lolium temulentum (ergotism/”darnel poisoning”), phorbol esters and ingenols in Euphorbia spp., cyanogenic glycosides in Triglochin maritima, and sympathomimetic compounds in Ephedra distachya (Table 1).

Table 1. Poisonous plant species recorded on the studied rangelands of Central Kazakhstan, major toxins, and brief toxic effects.

Family	Species	Life Span (Major Category)	Major Toxic Compounds	Brief Toxic Effects
Apiaceae	Cicuta virosa	Per	Cicutoxin and other polyacetylenes [51]	Blockade of GABAergic neurotransmission, convulsive syndrome, neurotoxic paralysis, and respiratory failure [52,53].
Apiaceae	Chaerophyllum temulum	Ann/Bienn	Polyacetylene (Z)-falcarinol (dominant component of root essential oil); sesquiterpenes in aerial parts [54]	Falcarinol-type polyacetylenes are skin irritants and sensitizers: contact dermatitis may occur upon exposure to plant sap (as is typical for Apiaceae polyacetylenes) [55,56]
Apiaceae	Conium maculatum	Ann/Bienn	Piperidine alkaloids (coniine, γ-coniceine) [57]	Blockade of nicotinic ACh receptors → paralysis and respiratory failure; no specific antidote [58,59,60]
Apiaceae	Oenanthe aquatica (syn. O. phellandrium)	Ann/Bienn	Furanocoumarins (incl. xanthotoxin/8-methoxypsoralen) [61]	Cutaneous photosensitization; phototoxic reactions under UVA exposure (typical of linear furanocoumarins such as xanthotoxin) [62]
Ranunculaceae	Pulsatilla patens	Per	Ranunculin → protoanemonin; saponins/triterpenes [63]	Marked irritation of the GI tract and mucosae, colic, dermatitis [64,65,66]
Ranunculaceae	Caltha palustris	Per	Protoanemonin, saponins, flavonoids [67]	GI irritation/toxicity (effects as described for the plant’s compounds) [67]
Ranunculaceae	Ranunculus sceleratus	Ann/Bienn	Ranunculin → protoanemonin (formed when fresh plant tissue is damaged); accompanying terpene/phenolic constituents [68,69]	Fresh plant parts are strong skin–mucosal irritants/vesicants (phytocontact dermatitis; bullous lesions with topical application of plant material). In livestock: GI irritation, colic/diarrhea; toxicity decreases upon drying [70,71,72,73]
Ranunculaceae	Delphinium consolida (syn. Consolida ajacis)	Ann/Bienn	Diterpenoid alkaloids (delphinine, delcosine, methyllycaconitine) [74]	Antagonism of nicotinic ACh receptors (nAChRs)—primarily the muscle subtype (NMJ) and neuronal α7; neuromuscular blockade → profound weakness, ataxia/collapse, respiratory failure, and potentially rapid death [75]
Brassicaceae	Erysimum cheiranthoides	Ann/Bienn	Glucosinolates (e.g., sinigrin derivatives); cardenolides (cardiac glycosides) also reported in the genus as co-defense [76]	Irritation of airways/mucosae, cough/burning upon inhalation of isothiocyanates [77,78]
Brassicaceae	Sinapis arvensis (syn. Brassica arvensis)	Ann/Bienn	Glucosinolates (sinigrin, gluconapin, glucobrassicin) [79,80]	GI irritation, hemolytic anemia, thyroid dysfunction, reproductive disorders; an acute case has been documented in sheep [79]
Fabaceae	Thermopsis lanceolata	Per	Alkaloids cytisine, thermopsine; (molecular mechanism of thermopsine) [81,82,83]	Neuro- and respiratory toxicity in livestock: vomiting, diarrhea, risk of respiratory failure [84]
Fabaceae	Lathyrus palustris	Per	Nitrilopropionamide and β-ODAP (lathyrogen) in the genus Lathyrus; closely related chemistry confirmed for L. palustris (family-level hazard for livestock) [85,86]	Neurotoxicity (lathyrism) with chronic high-dose intake; possible weakness, tremor/paresis. In livestock, respiratory and cardiovascular disturbances may occur with poisoning via feed contaminated with Lathyrus [85,87]
Fabaceae	Astragalus penduliflorus (syn. A. danicus)	Per	Swainsonine (indolizidine alkaloid) linked to the systemic seed-transmitted endophyte Alternaria sect. Undifilum (formerly Undifilum/Embellisia); swainsonine documented in many Astragalus/Oxytropis species [88,89]	“Locoism”: inhibition of lysosomal α-mannosidase → impaired glycoprotein degradation, accumulation of mannosides, cellular dysfunction; in ruminants—depression/lethargy, tremor and ataxia, weight loss, abortions, chronic neurologic and visceral lesions [90,91]
Solanaceae	Hyoscyamus niger	Ann/Bienn	Tropane alkaloids (hyoscyamine, scopolamine, atropine) [92,93]	Severe anticholinergic syndrome: dryness, mydriasis, tachycardia, agitation/delirium, hallucinations [94]
Solanaceae	Datura stramonium	Ann/Bienn	Tropane alkaloids (atropine, scopolamine, hyoscyamine) [95]	Pronounced anticholinergic toxidrome; poisonings are often linked to contamination of feed/food products [96,97]
Solanaceae	Solanum nigrum	Ann/Bienn	Steroidal glycoalkaloids (solanine, solanidine) [98]	GI disturbances, neuromuscular paralysis, seizures, respiratory failure; oxidative tissue damage [99,100,101,102]
Asteraceae	Tanacetum vulgare	Per	Major toxic constituents: thujone (monoterpene); sesquiterpene lactones (incl. parthenolide) [103]	Antagonism of GABA(_A) receptors → excitation/seizures at high doses; hepatotoxicity and neurologic signs are possible in livestock [104,105]
Asteraceae	Lactuca virosa	Ann/Bienn	Lactucin, lactucopicrin [106,107]	Sedative–analgesic effects; in livestock—depression, ataxia, tachycardia, possible seizures/respiratory depression (case report) [106,107]
Asteraceae	Senecio jacobaea (syn. Jacobaea vulgaris)	Per	1,2-unsaturated PAs (senecionine, jacobine, retrorsine and N-oxides) [108,109,110,111]	Chronic hepatotoxicity: megalocytosis, fibrosis/cirrhosis, hepatic encephalopathy, photosensitization in cattle/horses [109,110,111,112]
Plantaginaceae	Gratiola officinalis	Per	Iridoid glycosides (gratiooside/gratiolin) and other phytochemicals [113,114]	In livestock—GI irritation (diarrhea, vomiting, colic); potential systemic toxicity with ingestion of large amounts (summaries on toxic plants in livestock) [115,116]
Plantaginaceae	Digitalis purpurea	Ann/Bienn	Cardiac glycosides (digitoxin, digoxin; aglycones digitoxigenin/digoxigenin) [117]	Inhibition of membrane Na(^+)/K(^+)-ATPase by cardenolides (digitoxin/digoxin) → increased myocardial excitability, arrhythmias, GI symptoms; cardiotoxic cases described in livestock [118,119]
Euphorbiaceae	Euphorbia peplus	Ann/Bienn	Ingenane diterpenoids (incl. ingenol mebutate/ingenol 3-angelate) and other ingenol/ingol derivatives in plant latex [120,121]	Latex causes irritant contact dermatitis (erythema, vesicles/bullae, pain) upon skin contact; severe local skin reactions reported with topical ingenol mebutate; ocular exposure causes acute keratoconjunctivitis/keratitis [121,122,123]
Euphorbiaceae	Euphorbia esula (syn. E. virgata)	Per	Diterpenoids (ingenol and its esters), phorbol esters [124]	Skin reactions (blistering/ulceration) upon sap contact; in livestock—marked GI irritation, reduced palatability/productivity; sheep/goats are relatively more tolerant [125]
Poaceae	Lolium temulentum	Ann/Bienn	Loline-type alkaloids (loline, norloline) detected in L. temulentum seeds [126]; potentially other endophyte-associated alkaloids (as a general feature of grass–endophyte symbioses) [127]. Ergot alkaloids (ergotamine, ergonovine, etc.) produced by Claviceps spp. on grasses (incl. Lolium) [128,129]	When ergot alkaloids are present, ergotism predominates: pronounced vasoconstriction, hyperthermia/stress responses, ischemic lesions of limbs (necrosis in severe cases), reduced productivity [128,129]. “Darnel poisoning” is mainly CNS-type: lethargy/somnolence, dizziness, tremor, ataxia and impaired coordination, weakness; symptom severity may increase with fungal contamination of feed and mixed alkaloid profiles [130,131]
Boraginaceae	Nonea pulla (syn. N. incarnata)	Per	Pyrrolizidine alkaloids (lycopsamine, intermedine) [132,133]	Cumulative hepatotoxicity: wasting, photosensitization, hepatic veno-occlusive disease; suspected mass poisonings in cattle [133]
Caryophyllaceae	Saponaria officinalis	Per	Saponins (saponariosides; sapogenin derivatives; diosgenin-like structures) [134]	Excess intake may cause GI irritation (diarrhea, vomiting, abdominal pain) in livestock [135]
Convolvulaceae	Convolvulus arvensis	Per	Calystegines (nortropane alkaloid glycosidase inhibitors) are characteristic [136,137]	Data on calystegine toxicity in humans/livestock are limited; potential effects are linked to glycosidase inhibition and disruption of carbohydrate metabolism at high exposure [136,137]
Ephedraceae	Ephedra distachya	Per	Ephedrine-type alkaloids (ephedrine, etc.) [138]	Sympathomimetic syndrome: tachycardia, hypertension, agitation/hyperactivity; in severe cases—cardiovascular complications, seizures [139]
Geraniaceae	Geranium pseudosibiricum	Per	Tannins (ellagitannin geraniin), flavonoids, phenolic compounds [140]	At high doses, polyphenols may cause GI irritation; evidence for severe systemic toxicity is limited [141]
Juncaginaceae	Triglochin maritima	Per	Cyanogenic glycosides (e.g., triglochinin) [142]	Inhibition of cytochrome-c oxidase and tissue hypoxia due to HCN release; acute/chronic neurologic and cardiorespiratory effects are possible [143]
Lamiaceae	Galeopsis tetrahit	Ann/Bienn	Essential oils of aerial parts; predominance of sesquiterpene hydrocarbons (e.g., germacrene D, β-/γ-elemene) [144]	As with many essential oils, components may irritate skin and mucosae and can cause allergic contact dermatitis upon contact; with inhalation/ingestion of concentrated essential oils, toxic effects are possible (nausea/vomiting, CNS depression, etc.)—general effects typical of terpene-rich oils [145,146]
Papaveraceae	Chelidonium Per majus		Alkaloids (chelidonine, chelerythrine, sanguinarine, etc.) [147,148]	GI disturbances, dermatotoxicity; herb-induced hepatotoxicity has been reported with ingestion of extracts [149]

Note: Per—Perennial; Ann/Bienn—Annual/Biennial. Life span is given as the major category used for comparative summarization (Annual/Biennial vs. Perennial); taxa with variable life history in different floristic sources were assigned to the predominant category for the purposes of this study.

Table 1. Poisonous plant species recorded on the studied rangelands of Central Kazakhstan, major toxins, and brief toxic effects.

Family	Species	Life Span (Major Category)	Major Toxic Compounds	Brief Toxic Effects
Apiaceae	Cicuta virosa	Per	Cicutoxin and other polyacetylenes [51]	Blockade of GABAergic neurotransmission, convulsive syndrome, neurotoxic paralysis, and respiratory failure [52,53].
Apiaceae	Chaerophyllum temulum	Ann/Bienn	Polyacetylene (Z)-falcarinol (dominant component of root essential oil); sesquiterpenes in aerial parts [54]	Falcarinol-type polyacetylenes are skin irritants and sensitizers: contact dermatitis may occur upon exposure to plant sap (as is typical for Apiaceae polyacetylenes) [55,56]
Apiaceae	Conium maculatum	Ann/Bienn	Piperidine alkaloids (coniine, γ-coniceine) [57]	Blockade of nicotinic ACh receptors → paralysis and respiratory failure; no specific antidote [58,59,60]
Apiaceae	Oenanthe aquatica (syn. O. phellandrium)	Ann/Bienn	Furanocoumarins (incl. xanthotoxin/8-methoxypsoralen) [61]	Cutaneous photosensitization; phototoxic reactions under UVA exposure (typical of linear furanocoumarins such as xanthotoxin) [62]
Ranunculaceae	Pulsatilla patens	Per	Ranunculin → protoanemonin; saponins/triterpenes [63]	Marked irritation of the GI tract and mucosae, colic, dermatitis [64,65,66]
Ranunculaceae	Caltha palustris	Per	Protoanemonin, saponins, flavonoids [67]	GI irritation/toxicity (effects as described for the plant’s compounds) [67]
Ranunculaceae	Ranunculus sceleratus	Ann/Bienn	Ranunculin → protoanemonin (formed when fresh plant tissue is damaged); accompanying terpene/phenolic constituents [68,69]	Fresh plant parts are strong skin–mucosal irritants/vesicants (phytocontact dermatitis; bullous lesions with topical application of plant material). In livestock: GI irritation, colic/diarrhea; toxicity decreases upon drying [70,71,72,73]
Ranunculaceae	Delphinium consolida (syn. Consolida ajacis)	Ann/Bienn	Diterpenoid alkaloids (delphinine, delcosine, methyllycaconitine) [74]	Antagonism of nicotinic ACh receptors (nAChRs)—primarily the muscle subtype (NMJ) and neuronal α7; neuromuscular blockade → profound weakness, ataxia/collapse, respiratory failure, and potentially rapid death [75]
Brassicaceae	Erysimum cheiranthoides	Ann/Bienn	Glucosinolates (e.g., sinigrin derivatives); cardenolides (cardiac glycosides) also reported in the genus as co-defense [76]	Irritation of airways/mucosae, cough/burning upon inhalation of isothiocyanates [77,78]
Brassicaceae	Sinapis arvensis (syn. Brassica arvensis)	Ann/Bienn	Glucosinolates (sinigrin, gluconapin, glucobrassicin) [79,80]	GI irritation, hemolytic anemia, thyroid dysfunction, reproductive disorders; an acute case has been documented in sheep [79]
Fabaceae	Thermopsis lanceolata	Per	Alkaloids cytisine, thermopsine; (molecular mechanism of thermopsine) [81,82,83]	Neuro- and respiratory toxicity in livestock: vomiting, diarrhea, risk of respiratory failure [84]
Fabaceae	Lathyrus palustris	Per	Nitrilopropionamide and β-ODAP (lathyrogen) in the genus Lathyrus; closely related chemistry confirmed for L. palustris (family-level hazard for livestock) [85,86]	Neurotoxicity (lathyrism) with chronic high-dose intake; possible weakness, tremor/paresis. In livestock, respiratory and cardiovascular disturbances may occur with poisoning via feed contaminated with Lathyrus [85,87]
Fabaceae	Astragalus penduliflorus (syn. A. danicus)	Per	Swainsonine (indolizidine alkaloid) linked to the systemic seed-transmitted endophyte Alternaria sect. Undifilum (formerly Undifilum/Embellisia); swainsonine documented in many Astragalus/Oxytropis species [88,89]	“Locoism”: inhibition of lysosomal α-mannosidase → impaired glycoprotein degradation, accumulation of mannosides, cellular dysfunction; in ruminants—depression/lethargy, tremor and ataxia, weight loss, abortions, chronic neurologic and visceral lesions [90,91]
Solanaceae	Hyoscyamus niger	Ann/Bienn	Tropane alkaloids (hyoscyamine, scopolamine, atropine) [92,93]	Severe anticholinergic syndrome: dryness, mydriasis, tachycardia, agitation/delirium, hallucinations [94]
Solanaceae	Datura stramonium	Ann/Bienn	Tropane alkaloids (atropine, scopolamine, hyoscyamine) [95]	Pronounced anticholinergic toxidrome; poisonings are often linked to contamination of feed/food products [96,97]
Solanaceae	Solanum nigrum	Ann/Bienn	Steroidal glycoalkaloids (solanine, solanidine) [98]	GI disturbances, neuromuscular paralysis, seizures, respiratory failure; oxidative tissue damage [99,100,101,102]
Asteraceae	Tanacetum vulgare	Per	Major toxic constituents: thujone (monoterpene); sesquiterpene lactones (incl. parthenolide) [103]	Antagonism of GABA(_A) receptors → excitation/seizures at high doses; hepatotoxicity and neurologic signs are possible in livestock [104,105]
Asteraceae	Lactuca virosa	Ann/Bienn	Lactucin, lactucopicrin [106,107]	Sedative–analgesic effects; in livestock—depression, ataxia, tachycardia, possible seizures/respiratory depression (case report) [106,107]
Asteraceae	Senecio jacobaea (syn. Jacobaea vulgaris)	Per	1,2-unsaturated PAs (senecionine, jacobine, retrorsine and N-oxides) [108,109,110,111]	Chronic hepatotoxicity: megalocytosis, fibrosis/cirrhosis, hepatic encephalopathy, photosensitization in cattle/horses [109,110,111,112]
Plantaginaceae	Gratiola officinalis	Per	Iridoid glycosides (gratiooside/gratiolin) and other phytochemicals [113,114]	In livestock—GI irritation (diarrhea, vomiting, colic); potential systemic toxicity with ingestion of large amounts (summaries on toxic plants in livestock) [115,116]
Plantaginaceae	Digitalis purpurea	Ann/Bienn	Cardiac glycosides (digitoxin, digoxin; aglycones digitoxigenin/digoxigenin) [117]	Inhibition of membrane Na(^+)/K(^+)-ATPase by cardenolides (digitoxin/digoxin) → increased myocardial excitability, arrhythmias, GI symptoms; cardiotoxic cases described in livestock [118,119]
Euphorbiaceae	Euphorbia peplus	Ann/Bienn	Ingenane diterpenoids (incl. ingenol mebutate/ingenol 3-angelate) and other ingenol/ingol derivatives in plant latex [120,121]	Latex causes irritant contact dermatitis (erythema, vesicles/bullae, pain) upon skin contact; severe local skin reactions reported with topical ingenol mebutate; ocular exposure causes acute keratoconjunctivitis/keratitis [121,122,123]
Euphorbiaceae	Euphorbia esula (syn. E. virgata)	Per	Diterpenoids (ingenol and its esters), phorbol esters [124]	Skin reactions (blistering/ulceration) upon sap contact; in livestock—marked GI irritation, reduced palatability/productivity; sheep/goats are relatively more tolerant [125]
Poaceae	Lolium temulentum	Ann/Bienn	Loline-type alkaloids (loline, norloline) detected in L. temulentum seeds [126]; potentially other endophyte-associated alkaloids (as a general feature of grass–endophyte symbioses) [127]. Ergot alkaloids (ergotamine, ergonovine, etc.) produced by Claviceps spp. on grasses (incl. Lolium) [128,129]	When ergot alkaloids are present, ergotism predominates: pronounced vasoconstriction, hyperthermia/stress responses, ischemic lesions of limbs (necrosis in severe cases), reduced productivity [128,129]. “Darnel poisoning” is mainly CNS-type: lethargy/somnolence, dizziness, tremor, ataxia and impaired coordination, weakness; symptom severity may increase with fungal contamination of feed and mixed alkaloid profiles [130,131]
Boraginaceae	Nonea pulla (syn. N. incarnata)	Per	Pyrrolizidine alkaloids (lycopsamine, intermedine) [132,133]	Cumulative hepatotoxicity: wasting, photosensitization, hepatic veno-occlusive disease; suspected mass poisonings in cattle [133]
Caryophyllaceae	Saponaria officinalis	Per	Saponins (saponariosides; sapogenin derivatives; diosgenin-like structures) [134]	Excess intake may cause GI irritation (diarrhea, vomiting, abdominal pain) in livestock [135]
Convolvulaceae	Convolvulus arvensis	Per	Calystegines (nortropane alkaloid glycosidase inhibitors) are characteristic [136,137]	Data on calystegine toxicity in humans/livestock are limited; potential effects are linked to glycosidase inhibition and disruption of carbohydrate metabolism at high exposure [136,137]
Ephedraceae	Ephedra distachya	Per	Ephedrine-type alkaloids (ephedrine, etc.) [138]	Sympathomimetic syndrome: tachycardia, hypertension, agitation/hyperactivity; in severe cases—cardiovascular complications, seizures [139]
Geraniaceae	Geranium pseudosibiricum	Per	Tannins (ellagitannin geraniin), flavonoids, phenolic compounds [140]	At high doses, polyphenols may cause GI irritation; evidence for severe systemic toxicity is limited [141]
Juncaginaceae	Triglochin maritima	Per	Cyanogenic glycosides (e.g., triglochinin) [142]	Inhibition of cytochrome-c oxidase and tissue hypoxia due to HCN release; acute/chronic neurologic and cardiorespiratory effects are possible [143]
Lamiaceae	Galeopsis tetrahit	Ann/Bienn	Essential oils of aerial parts; predominance of sesquiterpene hydrocarbons (e.g., germacrene D, β-/γ-elemene) [144]	As with many essential oils, components may irritate skin and mucosae and can cause allergic contact dermatitis upon contact; with inhalation/ingestion of concentrated essential oils, toxic effects are possible (nausea/vomiting, CNS depression, etc.)—general effects typical of terpene-rich oils [145,146]
Papaveraceae	Chelidonium Per majus		Alkaloids (chelidonine, chelerythrine, sanguinarine, etc.) [147,148]	GI disturbances, dermatotoxicity; herb-induced hepatotoxicity has been reported with ingestion of extracts [149]

Note: Per—Perennial; Ann/Bienn—Annual/Biennial. Life span is given as the major category used for comparative summarization (Annual/Biennial vs. Perennial); taxa with variable life history in different floristic sources were assigned to the predominant category for the purposes of this study.

Life-span summarization (annual/biennial vs. perennial taxa) provided an additional ecological descriptor of the recorded poisonous-species set (Table 1). Overall, the regional list was evenly represented by the two major categories (16 annual/biennial and 16 perennial species). At the same time, the wet-year recruitment in the Nura floodplain (NF) included a substantial contribution of perennial wet-associated taxa (e.g., Cicuta virosa, Triglochin maritima, Gratiola officinalis, and Lathyrus palustris), indicating that the 2024 increase was not limited to short-lived ruderal species.

Functionally, four major risk syndromes predominated: anticholinergic (tropane alkaloids in Solanaceae), cumulative hepatotoxic (1,2-unsaturated pyrrolizidine alkaloids in Senecio and Boraginaceae), convulsant neurotoxic (GABA antagonism/neuroexcitatotoxicity in Apiaceae; effects on sodium channels in Delphinium; thujone in Tanacetum), and hypoxic (HCN release in Triglochin maritima).

Quantitatively, the assemblage shows clear clustering by mechanism: at least five species can produce an anticholinergic toxidrome (tropanes), at least three are associated with cumulative hepatotoxicity (PAs/echimidine), and four to five can elicit convulsant neurotoxic manifestations (GABA antagonists/sodium-channel effects). Hypoxic and cardiotoxic syndromes are each represented by single-species but high-risk cases (Triglochin and Digitalis, respectively). The dominant exposure pathways are feedborne, driven by contamination of forage: seeds/hay in Datura/Hyoscyamus, dried Senecio biomass in hay, and ergot sclerotia associated with Lolium. These pathways account for the largest share of clinically significant outcomes.

3.2. Spatial Patterns and Interannual Changes in Poisonous-Plant Diversity and Moisture-Affinity Group Composition

Across two consecutive growing seasons (2023–2024), we recorded 32 poisonous vascular plant species from 17 families. In the drought year (2023), 25 unique species were documented, whereas the exceptionally wet year (2024) added seven taxa, increasing the regional pool to 32 unique species (53 and 60 “species × rangeland” records, respectively). All “new” taxa appeared exclusively in the Nura River floodplain (NF), likely in response to the record flood: the wet-associated taxa Cicuta virosa, Oenanthe aquatica, Ranunculus sceleratus, Triglochin maritima, Gratiola officinalis, and Lathyrus palustris, as well as the mesophyte Senecio jacobaea. No species recorded in 2023 disappeared in 2024, underscoring the persistence even of rare xerophytic elements (Table 2).

Table 2. Species list and Drude abundance classes for poisonous plants across three rangelands of Central Kazakhstan.

Species/Pasture	Moisture Group	2023 KK	2023 NF	2023 UF	2024 KK	2024 NF	2024 UF
Astragalus penduliflorus (syn. A. danicus)	Xerophyte	—	—	Sol	—	—	Sol
Ephedra distachya	Xerophyte	—	—	Sol	—	—	Sol
Nonea pulla (syn. N. incarnata)	Xerophyte	Sol	—	Sp	Sol	—	Sp
Pulsatilla patens (syn. Anemone patens, Pulsatilla multifida)	Mesoxerophyte	Cop1	—	Sp	Cop1	—	Sp
Convolvulus arvensis	Xeromesophyte	Cop1	Cop1	Cop1	Cop1	Cop1	Cop2
Delphinium consolida (syn. Consolida ajacis = D. ajacis)	Xeromesophyte	Sp	—	Un	Sp	—	Un
Euphorbia esula (syn. E. virgata)	Xeromesophyte	Cop1	—	Cop1	Cop1	—	Cop1
Lactuca virosa (syn. L. scariola var. virosa)	Xeromesophyte	Sol	Sol	Sp	Sol	Sol	Sp
Thermopsis lanceolata (syn. T. montana subsp. lanceolata)	Xeromesophyte	Cop1	—	Sp	Cop2	—	Sp
Chaerophyllum temulum	Mesophyte	Un	—	—	Un	—	—
Chelidonium majus	Mesophyte	Sol	—	—	Sol	—	—
Conium maculatum	Mesophyte	Sol	Sp	Un	Sol	Sp	Un
Datura stramonium	Mesophyte	Sol	Sol	Sp	Sol	Sol	Sp
Digitalis purpurea	Mesophyte	Un	—	—	Un	—	—
Erysimum cheiranthoides	Mesophyte	Sol	Sol	Sp	Sol	Sol	Sp
Euphorbia peplus (syn. Chamaesyce peplus)	Mesophyte	Sol	Un	—	Sol	Un	—
Galeopsis tetrahit	Mesophyte	Un	—	—	Un	—	—
Geranium pseudosibiricum	Mesophyte	Cop1	—	—	Cop1	—	—
Hyoscyamus niger	Mesophyte	Sol	Sol	Sp	Sol	Sol	Sp
Lolium temulentum	Mesophyte	Sp	Sol	Sp	Sp	Sol	Sp
Senecio jacobaea (syn. Jacobaea vulgaris)	Mesophyte	—	—	—	—	Un	—
Sinapis arvensis (syn. Brassica arvensis)	Mesophyte	Cop1	Cop1	Sp	Cop2	Cop2	Sp
Solanum nigrum (syn. S. vulgare)	Mesophyte	Sol	Sol	Sp	Sol	Sol	Sp
Saponaria officinalis	Mesophyte	Un	Un	—	Un	Un	—
Tanacetum vulgare (syn. Chrysanthemum vulgare)	Mesophyte (slightly xerophilous)	Cop2	Cop1	Sp	Cop2	Cop1	Sp
Caltha palustris	Wet-associated	Sol	Sol	—	Sol	Sol	—
Cicuta virosa	Wet-associated	—	—	—	—	Un	—
Gratiola officinalis	Wet-associated	—	—	—	—	Un	—
Lathyrus palustris (syn. Lathyrostylis palustris)	Wet-associated	—	—	—	—	Un	—
Oenanthe aquatica (syn. O. phellandrium)	Wet-associated	—	—	—	—	Sp	—
Ranunculus sceleratus	Wet-associated	—	—	—	—	Un	—
Triglochin maritima	Wet-associated	—	—	—	—	Un	—

Note: KK—Karkaraly Hills; NF—Nura Floodplain; UF—Ulytau Foothills. Species abundance is shown using the modified Drude scale.

Table 2. Species list and Drude abundance classes for poisonous plants across three rangelands of Central Kazakhstan.

Species/Pasture	Moisture Group	2023 KK	2023 NF	2023 UF	2024 KK	2024 NF	2024 UF
Astragalus penduliflorus (syn. A. danicus)	Xerophyte	—	—	Sol	—	—	Sol
Ephedra distachya	Xerophyte	—	—	Sol	—	—	Sol
Nonea pulla (syn. N. incarnata)	Xerophyte	Sol	—	Sp	Sol	—	Sp
Pulsatilla patens (syn. Anemone patens, Pulsatilla multifida)	Mesoxerophyte	Cop1	—	Sp	Cop1	—	Sp
Convolvulus arvensis	Xeromesophyte	Cop1	Cop1	Cop1	Cop1	Cop1	Cop2
Delphinium consolida (syn. Consolida ajacis = D. ajacis)	Xeromesophyte	Sp	—	Un	Sp	—	Un
Euphorbia esula (syn. E. virgata)	Xeromesophyte	Cop1	—	Cop1	Cop1	—	Cop1
Lactuca virosa (syn. L. scariola var. virosa)	Xeromesophyte	Sol	Sol	Sp	Sol	Sol	Sp
Thermopsis lanceolata (syn. T. montana subsp. lanceolata)	Xeromesophyte	Cop1	—	Sp	Cop2	—	Sp
Chaerophyllum temulum	Mesophyte	Un	—	—	Un	—	—
Chelidonium majus	Mesophyte	Sol	—	—	Sol	—	—
Conium maculatum	Mesophyte	Sol	Sp	Un	Sol	Sp	Un
Datura stramonium	Mesophyte	Sol	Sol	Sp	Sol	Sol	Sp
Digitalis purpurea	Mesophyte	Un	—	—	Un	—	—
Erysimum cheiranthoides	Mesophyte	Sol	Sol	Sp	Sol	Sol	Sp
Euphorbia peplus (syn. Chamaesyce peplus)	Mesophyte	Sol	Un	—	Sol	Un	—
Galeopsis tetrahit	Mesophyte	Un	—	—	Un	—	—
Geranium pseudosibiricum	Mesophyte	Cop1	—	—	Cop1	—	—
Hyoscyamus niger	Mesophyte	Sol	Sol	Sp	Sol	Sol	Sp
Lolium temulentum	Mesophyte	Sp	Sol	Sp	Sp	Sol	Sp
Senecio jacobaea (syn. Jacobaea vulgaris)	Mesophyte	—	—	—	—	Un	—
Sinapis arvensis (syn. Brassica arvensis)	Mesophyte	Cop1	Cop1	Sp	Cop2	Cop2	Sp
Solanum nigrum (syn. S. vulgare)	Mesophyte	Sol	Sol	Sp	Sol	Sol	Sp
Saponaria officinalis	Mesophyte	Un	Un	—	Un	Un	—
Tanacetum vulgare (syn. Chrysanthemum vulgare)	Mesophyte (slightly xerophilous)	Cop2	Cop1	Sp	Cop2	Cop1	Sp
Caltha palustris	Wet-associated	Sol	Sol	—	Sol	Sol	—
Cicuta virosa	Wet-associated	—	—	—	—	Un	—
Gratiola officinalis	Wet-associated	—	—	—	—	Un	—
Lathyrus palustris (syn. Lathyrostylis palustris)	Wet-associated	—	—	—	—	Un	—
Oenanthe aquatica (syn. O. phellandrium)	Wet-associated	—	—	—	—	Sp	—
Ranunculus sceleratus	Wet-associated	—	—	—	—	Un	—
Triglochin maritima	Wet-associated	—	—	—	—	Un	—

Note: KK—Karkaraly Hills; NF—Nura Floodplain; UF—Ulytau Foothills. Species abundance is shown using the modified Drude scale.

The total number of unique species across all sites was 25 in 2023 and 32 in 2024; the total number of “species × site” combinations with recorded presence (non-zero cover at least at one point) was 53 and 60, respectively.

Comparison of occurrence patterns across the three rangelands indicates asymmetric responses to the climatic contrast. Karkaraly Hills (KK) maintained the broadest poisonous-plant assemblage in both the dry and wet seasons, with 23 species recorded in each year. The Nura Floodplain (NF) was the most dynamic site: following an exceptionally wet spring, its poisonous-plant list increased from 13 to 20 species (an addition of 7 taxa, ≈54%), primarily due to the appearance of new wet-associated taxa (hydrophytic/hygrophytic group) (Cicuta virosa, Oenanthe aquatica, Ranunculus sceleratus, Triglochin maritima, Gratiola officinalis, Lathyrus palustris) and one additional mesophyte (Senecio jacobaea). In contrast, the Ulytau foothills (UF) showed the greatest stability: 17 species were recorded in both 2023 and 2024, consistent with their harsh xeric habitat conditions, which remain relatively resistant to colonization even in wetter years (Table 2).

In terms of the distribution of species richness across abundance categories, this manifested as a shift from moderately rich communities toward a more polarized structure: the number of records in the Cop2 (“very abundant”) category increased from 1 to 5, while Un records increased from 8 to 14; at the same time, Cop1 decreased (11 → 7), whereas Sol and Sp remained nearly unchanged (19 and 15 → 19 and 16, respectively) (

Table 3. Distribution of records (“species × site”) across cover-abundance classes (Drude scale), pooled across the three rangelands.

Class	2023 (n = 53 Records)	2024 (n = 60 Records)	Δ
Cop2	1	5	×5
Cop1	11	7	−36%
Sol	19	19	0
Sp	15	16	+7%
Un	8	14	+75%

Note: n is the number of “species × site” records (each unique species–site combination in a given year is treated as a separate record). In 2023, 25 unique species corresponded to 53 records; in 2024, 32 unique species corresponded to 60 records. Classes: Un (unicum)—single occurrences (<0.1% cover); Sol (solitaria)—rare, as individual plants (<1%); Sp (sparsae)—scattered, frequent but with low cover (≈1–5%); Cop1/Cop2/Cop3 (copiosae)—abundant (≈5–25%, 25–50%, and 50–75%, respectively).

).

In other words, the 2024 season produced a more uneven distribution of species abundances. On the one hand, we observed mass outbreaks of Tanacetum vulgare and Thermopsis lanceolata, accompanied by two localized patches of Sinapis arvensis and a patch of Convolvulus arvensis (all classified as Cop2 by the cover scale). On the other hand, a broad base of rare occurrences emerged (Caltha palustris, Ranunculus sceleratus, Triglochin maritima, Gratiola officinalis, among others), likely germinating from the seed bank following flood-driven moisture inputs.

Following these shifts in the abundance spectrum, the composition of moisture-affinity groups also changed. In the Nura River floodplain in 2024, the pooled wet-associated group (hygrophilous/hydrophytic taxa) increased markedly (from one to seven species), whereas moisture-group profiles in the Karkaraly Hills and Ulytau foothills remained essentially unchanged; across all sites, mesophytes predominated. This pattern is consistent with a flood-driven recruitment scenario in which wetland and riparian taxa are activated from the diaspores (seed) bank in the floodplain without displacing the stable xeromorphic background of the other rangelands (Figure 5).

This descriptive pattern motivates a testable hypothesis: the between-site heterogeneity observed in 2024 was driven by a localized surge of wet-associated taxa (hydrophytic/hygrophytic group) in the Nura floodplain, while the other two sites remained stable. To formally evaluate these differences, we applied exact nonparametric tests. For each year, we assessed the association between “moisture-affinity group × rangeland” (5 × 3 contingency tables). In 2023, the Fisher–Freeman–Halton test indicated no heterogeneity (p = 0.510 (Monte Carlo approximation, 100,000 replicates), i.e., the drought year produced broadly similar group profiles across all sites. In 2024, the same test detected significant heterogeneity (p = 0.016 (Monte Carlo approximation, 100,000 replicates), driven primarily by an increase in the pooled wet-associated group at NF (

Table 4. Fisher–Freeman–Halton test for the association between moisture-affinity group and rangeland.

Year	p (Monte Carlo, 100,000 Replicates)	Interpretation
2023	0.510	No differences among rangelands were detected
2024	0.016	Moisture-affinity group profiles differ, driven by the pooled wet-associated group at NF

).

Thus, the Fisher–Freeman–Halton analysis confirms that only the wet year resulted in between-site differentiation in the composition of poisonous plants. These results align with our descriptive inference that extreme precipitation selectively restructures the floodplain community, whereas the mountain and foothill sites remain essentially unchanged (Table 4).

To test whether gains and losses of poisonous species within each rangeland were directionally biased between years, we applied the exact McNemar test to paired presence–absence data. In summary, Karkaraly Hills and the Ulytau foothills showed perfect symmetry (b = 0, c = 0; p = 1.000), indicating no net change. In contrast, the Nura floodplain exhibited seven gains and no losses (b = 7, c = 0; p = 0.016) (

Table 5. McNemar test for net gains and losses of poisonous plant species (2023–2024).

Rangeland	Gains (b)	Losses (c)	p (exact)	Interpretation
Karkaraly Hills (KK)	0	0	1.000	No directional change
Nura Floodplain (NF)	7	0	0.016	Significant net gain
Ulytau Foothills (UF)	0	0	1.000	No directional change

).

Taken together, the two exact tests indicate that xerophyte-dominated mountain and foothill rangelands are floristically stable, whereas the flood-driven recruitment of the pooled wet-associated group (hygrophilous/hydrophytic poisonous taxa) can rapidly and substantially increase both the diversity and potential toxicity of pastures in low-lying alluvial landscapes.

4. Discussion

Poisonings of livestock by poisonous pasture plants are widely conceptualized as an “ecologically mediated” risk that is shaped by two interacting sets of factors: the spatial confinement of toxic taxa to particular microhabitats and moisture regimes, and animal exposure pathways, in which the decisive role is often played not by direct grazing but by toxin transfer through conserved feeds (hay, silage, and grain/fodder) and the contamination of raw materials by weedy components. This two-component perspective is consistent with contemporary syntheses emphasizing that the clinical relevance of “toxic flora” is determined not only by species presence, but also by the likelihood of contact (feed chains), seasonal availability, and the detectability of toxicoses, including delayed presentations [150].

The regional pool documented in our study (32 poisonous vascular plant species from 17 families across two hydrologically contrasting seasons) fits the broader pattern of high taxonomic mosaicism in rangeland toxic complexes. Large-scale reviews highlight that hazardous assemblages are typically drawn from a limited set of “chemically active” families, whereas their actual epizootiological significance is governed by localized dominance foci and episodes of mass exposure. Importantly, interannual dynamics of the overall pool in our dataset were directional: the drought year 2023 comprised 25 species, and the exceptionally wet year 2024 added seven taxa, bringing the cumulative list to 32. This gain was spatially asymmetric: all seven “new” taxa appeared exclusively in the Nura floodplain (NF), whereas the Karkaraly hills (KK) and Ulytau foothills (UF) retained stable lists of poisonous species. Within this framework, it is particularly notable that the “core” of floodplain and near-water habitats in our system is represented by wet-associated taxa (including hygrophilous and truly hydrophytic species), while the “intermediate block” is dominated by ruderal–synanthropic mesophytes and xeromesophytes. Such habitat-based partitioning is typical of systems in which seasonal hydrology creates sharply different windows for recruitment and plant availability: studies of floodplain and riparian zones show that shifts in moisture and inundation can rapidly mobilize the hidden seed bank and alter the active flora without necessarily displacing background elements [151].

Accordingly, the notion of “landscape complementarity of toxic niches” is not merely conceptual. Research on floodplain dynamics repeatedly demonstrates that taxa associated with alluvial depressions, waterlogged margins, and intermittently inundated surfaces can appear or sharply increase in occurrence following prolonged wetting, while species of drier and more anthropogenically transformed habitats persist interannually and form a stable background [152]. In our system, this distinction matters because the 2024 pulse of wet-associated poisonous taxa in the Nura floodplain was not only a floristic addition (seven “new” taxa), but also a functional expansion of toxic mechanisms and potential exposure scenarios. Quantitatively, this was expressed as an increase in local species richness in NF from 13 to 20, whereas KK remained at 23 species in both years and UF remained at 17 species in both years. The linkage “hydrological impulse → recruitment → functional complexification” is explicitly discussed in studies on the effects of seasonal flooding on seed banks and post-flood succession, which emphasize the role of inundation in switching dominance among ecological groups (aquatic/amphibious/terrestrial) [153].

The two-layer organization of poisonous-plant assemblage (locally constrained “floodplain” risks plus background ruderal risks) is also pathophysiologically consequential because it implies different routes of toxicant entry. For floodplain taxa, the critical factor is a short seasonal window of high availability of green biomass after wetting and/or flooding, when the riparian–wetland cohort of seedlings is rapidly activated and a temporarily enriched forage matrix develops near watering points and on alluvial meadows. This mechanism aligns with evidence that flooding can sharply increase seedling emergence from the seed bank and alter the composition of available vegetation over a short period [154]. In our data, this is supported by the shift in moisture-affinity groups specifically in NF: the pooled wet-associated group (hygrophilous/hydrophytic taxa) increased from 1 to 7 species, producing the statistically detectable between-site heterogeneity in 2024 (in contrast to 2023). By contrast, for ruderals and weeds, the dominant risk contour is “forage harvesting → contamination → consumption of conserved feeds,” because many toxic plants are poorly grazed when alternatives are available but become hazardous once incorporated into bales/rolls (higher palatability due to drying, fragmentation, and within-group competition). This scenario is emphasized in specialized reviews on feed contamination by poisonous plants in horses and farm animals [155].

Our interpretation that feed contamination is the dominant exposure route is supported not only by general toxicological reasoning but also by direct clinical observations. A classic example is equine poisoning outbreaks that ceased after withdrawal of hay contaminated with Datura spp., demonstrating that “invisible” weed admixtures in dried forage can trigger clinically significant events [156]. Likewise, the association of Datura stramonium with colic in horses and the importance of weed contamination were also confirmed in a short report in Veterinary Record [157].

The statement regarding “mechanism-based clustering” is likewise grounded in current practice for describing poisonous-plant assemblages and poisoning outbreaks. Major reviews of toxic plants commonly systematize risks either by toxic compounds or by affected organ systems/syndromes, emphasizing that prevention and rangeland management require mapping species → toxicant → target organ/system → exposure pathway, rather than limiting the analysis to species lists alone [7]. Particularly illustrative in this context is the cumulative hepatotoxic block of pyrrolizidine alkaloids (PAs), for which delayed clinical presentation and “after-the-fact” diagnosis are typical, often after contaminated feed has already been consumed. Risk assessments highlight the capacity of pyrrolizidine alkaloids (PAs) to cause chronic liver injury under cumulative exposure and the difficulty of early recognition due to non-specific initial signs [158]. The practical dimension of feedborne diagnosis and the role of contamination are further illustrated by an LC/TOF-MS study detecting ragwort (Senecio) pyrrolizidine alkaloids in toxic hay, demonstrating that conserved feed can conceal clinically relevant hazards and that confirmation may require targeted laboratory testing [159]. Accordingly, our emphasis on contamination by dried Senecio biomass and by seeds/fragments of Solanaceae and other weeds reflects a widely documented primary exposure pathway across multiple regions rather than an idiosyncratic interpretation.

The key “dynamic” component of our results—the asymmetric interannual change in the Nura floodplain with stability in the Karkaraly Hills and Ulytau foothills—can be parsimoniously interpreted through a flood-driven recruitment-from-diaspore-bank model. This model accords well with evidence from seasonally inundated landscapes showing that prolonged wetting/flooding increases both the proportion and diversity of aquatic/amphibious species emerging from the seed bank and can add to the active flora taxa that are scarcely detectable in the aboveground cover in “typical” years [160]. In our material, this pattern emerged in a maximally “clean” form: all seven taxa added in 2024 appeared exclusively in the Nura floodplain (NF), and the McNemar test documented a directional net gain without losses, whereas no directional turnover was detected in the Karkaraly Hills (KK) or the Ulytau foothills (UF). This type of response is characteristic of systems under strong hydrological control, where new occurrences in a given year are more often attributable to activation of locally stored diaspores than to “external migration,” as shifts in germination and seedling-survival conditions move diaspores from a dormant state to active establishment.

Importantly, the 2024 “wet impulse” in our study was associated not with the replacement of the xeromorphic background at the mountain/foothill sites but with a localized enrichment of the floodplain moisture-affinity structure, reflected in an increase in the pooled wet-associated group (hygrophilous/hydrophytic taxa) from 1 to 7 species specifically in NF (against an overall dominance of mesophytes), as well as with a rise in the total number of “species × site” presence records from 53 (2023) to 60 (2024). Formal testing corroborated this pattern: in 2023, there was no association between moisture-affinity group and rangeland (Fisher–Freeman–Halton exact test: p = 0.510), whereas in 2024, significant heterogeneity was detected (p = 0.016), driven by an increased share of aquatic/riparian elements in NF. This outcome is consistent with broader conclusions from research on precipitation variability and dry/semi-arid ecosystem responses: interannual moisture fluctuations more often shift abundance, productivity, and the relative contributions of functional groups within an existing species pool than produce “mass colonization” by novel taxa in edaphically constrained habitats, where environmental filters (soils, exposure, microrelief) maintain a stable floristic core [161,162]. Moreover, precipitation variability has been shown to increase interannual heterogeneity of ecosystem properties and to redistribute the contributions of specific groups to overall community structure [163]. In our case, the floodplain functioned as a “switchable” landscape module, whereas the two drier sites exhibited floristic inertia—consistent with the principle that hydrologically dynamic landscape elements (floodplains, swales, depressions) account for most interannual fluctuations in available vegetation, while “hard” habitats retain a stable core [164].

This contrast can also be interpreted in terms of landscape type. The Karkaraly Hills (KK) and Ulytau foothills (UF) represent automorphic xeromorphic systems, where poisonous-plant assemblages are structured by relatively stable dry-site filters and therefore show low interannual turnover. In contrast, the Nura floodplain (NF) is a hydromorphic landscape element, and its poisonous-plant assemblage is more responsive to flood-driven changes in soil moisture and temporary habitat activation. Thus, the observed differences reflect not only year effects, but also fundamentally different ecological response patterns in automorphic versus hydromorphic landscapes.

The life-span summary provides additional ecological context for the floodplain response. Although the overall poisonous-species set was evenly represented by annual/biennial and perennial taxa, the 2024 recruitment in NF was characterized by a substantial contribution of perennial wet-associated species. This pattern supports the interpretation that floodplain changes reflected hydrologically driven habitat activation and detectability of moisture-dependent poisonous plants, rather than only short-term emergence of annual weeds.

Finally, the increased “unevenness” of cover distributions observed in 2024 aligns with a typical pulse–resource dynamic: mass outbreaks of a small number of rapidly responding species coincide with a higher probability of detecting rare taxa during a short window of successful germination and establishment. In our data, this manifested as an increase in Cop2 records from 1 to 5 and an increase in single-occurrence records (Un) from 8 to 14, while background classes remained broadly stable—logically consistent with evidence that flooding/wetting regulates both the intensity of emergence from the seed bank and subsequent filtering during early seedling stages [165,166].

Taken together, our results indicate that interannual hydroclimatic contrasts in steppe rangelands do not necessarily lead to the wholesale “reassembly” of the regional poisonous-plant assemblage. More often, they activate a mechanism of localized—yet statistically detectable—differentiation within hydrologically sensitive landscape elements (floodplains), whereas xeromorphic mountain and foothill rangelands retain a stable floristic core. This interpretation is consistent both with theory and syntheses on precipitation legacies and functional ecosystem responses, and with empirical evidence on the role of inundation in mobilizing seed banks and temporarily expanding the active flora of riparian–wetland taxa [155,162]. The present analysis focuses on functional restructuring of the poisonous-plant assemblage rather than within-plot diversity metrics. Therefore, the conclusions relate to landscape-scale compositional stability and directional recruitment processes rather than α-diversity comparisons among sampling points.

From a prevention standpoint, this implies that the “risk calendar” in such years should be asymmetric: after floods, intensified field inspection of floodplains and tighter control of grazing and watering points become critical, while throughout the entire season, strict oversight of forage harvesting and exclusion of weedy admixtures remain essential, because the feedborne route accounts for the largest share of clinically significant outcomes in global practice.

Particular attention should be paid to several indicator toxic species that determined the practical risk patterns. The floodplain response in the wet year was driven primarily by wet-associated poisonous taxa (including hygrophilous and truly hydrophytic species: Cicuta virosa, Oenanthe aquatica, Ranunculus sceleratus, Triglochin maritima, Gratiola officinalis, and Lathyrus palustris) and by the mesophyte Senecio jacobaea, whose appearance reflects temporary waterlogging and creates short-term grazing hazard after flooding. In contrast, xeromorphic pastures retained a stable toxic core dominated by feed-contaminating and pasture-persistent taxa (Datura/Hyoscyamus, Lolium temulentum, Ephedra distachya, Tanacetum, Delphinium). Thus, livestock risk is governed not by overall species richness but by the presence of specific ecologically diagnostic species linked to hydrological conditions.

The present study does not apply a formal hazard-ranking scheme across species, because comparative toxic hazard depends not only on intrinsic toxicity but also on plant part, phenological stage, route of exposure, forage contamination, and livestock susceptibility. Instead, we distinguish between short-term flood-related hazards caused by wet-associated poisonous taxa and persistent background risks associated with forage-contaminating species.

5. Conclusions

Poisonous plants constitute a persistent and functionally structured component of Central Kazakhstan rangelands, but their composition and risk profile are not uniformly expressed across landscapes and years. Our findings indicate that hydroclimatic extremes primarily translate into variation in the poisonous-plant assemblage through hydrologically sensitive landscape elements, with floodplain pastures acting as the most responsive module under wet, flood-associated conditions, while xeromorphic mountain and foothill pastures tend to retain a stable floristic core.

Such wet-year pulses promote the short-term recruitment of riparian and wetland taxa and increase the unevenness of abundance patterns, combining localized outbreaks of a few rapidly responding species with a broader set of rare, transient occurrences likely linked to post-flood germination from the diaspores bank. The observed poisonous-plant assemblage is best interpreted through a limited set of clinically relevant syndromes, reinforcing the value of mechanism-based risk profiling rather than species lists alone. From a prevention standpoint, the most consequential exposure route is frequently feedborne via the contamination of conserved forage, which implies an asymmetric risk calendar that pairs intensified post-flood inspection of floodplains and watering areas with continuous quality control during forage harvesting and strict exclusion of weedy admixtures.