Search Results (442)

Topological indices provide numerical descriptions of graph structure and support graph analysis in cheminformatics, network design, and graph mining. This study presents a reproducible computational framework that combines controlled cyclic-graph generation, structure-preserving transformations, exact computation of six classical topological indices, and multi-output graph neural network regression. The framework evaluates the Wiener, Merrifield–Simmons, Hosoya, first Zagreb, second Zagreb, and Randi’c indices for unicyclic and bicyclic graphs. It represents each graph using sparse connectivity and node-level features that encode degree, cycle membership, pendant connectivity, leaf status, and normalized eccentricity. A graph isomorphism network (GIN) jointly predicts the six indices and is compared with graph convolutional networks (GCNs), graph attention networks (GATs), and descriptor-based regression baselines. The controlled benchmark shows that nonlinear descriptor-based models achieve the lowest aggregate errors because the supplied graph-level descriptors contain strong prior information about graph size, degree structure, branching, and cycle complexity. Although GIN does not achieve the highest overall accuracy, it provides the strongest graph-native performance by learning directly from sparse connectivity and node-level features without requiring a fixed handcrafted graph-level descriptor vector. The proposed surrogate does not replace exact evaluation for isolated small graphs, where exact computation remains more appropriate. Instead, its practical value emerges through repeated evaluations of larger, more complex graph instances. To examine this setting, a computational stress experiment evaluates sparse multicyclic graphs under increasing cyclomatic complexity and measures exact computation time, timeout frequency, prediction accuracy, and the amortized break-even point. The results indicate that surrogate prediction becomes beneficial when combinatorial index computation becomes sufficiently expensive, and the trained model is reused across many structurally related graph queries. An external experiment on circulant graphs also demonstrates that the framework can extend beyond the original graph generators by modifying only the graph-construction stage. Full article

Saxicolous lichens are crucial elements of alpine ecosystems and are involved in soil formation, rock weathering, nutrient cycling, and environmental monitoring. However, little is known about their distribution patterns and diversity on the eastern Pamir Plateau of China. This study looked at the variety and elevational distribution of saxicolous lichens in China’s eastern Pamir Plateau’s Taxkorgan Nature Reserve. Six transects spanning an elevational range of 3500–4500 m were used for field studies in July and August of 2025. Stratified sampling was used to gather lichen specimens, which were then identified by morphological, anatomical, chemical (thin-layer chromatography), and molecular investigations. Lichens communities’ similarity across altitudes was evaluated using Sørensen’s index, and diversity indices such as Simpson, Shannon–Wiener, and Pielou’s consistency were computed. A total of 69 saxicolous lichen species from 12 families and 27 genera were identified. With 95.6% of all species, crustose lichens predominated, whilst foliose and fruticose forms were uncommon. Acarosporaceae and Megasporaceae were the most species-rich families, accounting for over half of total recognized species. In the study region, Aspicilia and Acarospora dominated at the genus level. Saxicolous lichen species richness exhibited a unimodal elevational pattern, peaking at 4101–4300 m with pronounced community turnover across altitudes, as supported by Sørensen similarity values (0.253–0.561). Additionally, substrate type affected lichen distribution, with siliceous rocks hosting richer lichen communities than calcareous substrates. In general, the richness and distribution of saxicolous lichens in the alpine ecosystems of the eastern Pamir Plateau are mostly determined by elevation and rock type. This work provides essential baseline data for lichen biodiversity in the region and highlights the potential use of lichens as bio-indicators for monitoring environmental change in high-mountain ecosystems. Full article

Centella asiatica (L.) Urb., a perennial herb of the Apiaceae family, is an important medicinal plant with diverse therapeutic applications. In this study, we integrated phenotypic evaluation, SSR markers, and HPLC fingerprinting to assess the diversity of 24 C. asiatica accessions collected from Yunnan Province, China. Considerable phenotypic, genetic, and biochemical diversity was observed. The Shannon–Wiener index ranged from 2.20 to 3.14 for qualitative traits. Principal component analysis identified five components accounting for 82.54% of the total phenotypic variance, with leaf morphology as the primary determinant. Q-type cluster analysis grouped the accessions into five phenotypic clusters. Transcriptome analysis revealed 16,799 SSR loci, with dinucleotide repeats as the most frequent motif (44.31%). UPGMA clustering based on SSR markers delineated five genetic groups that correlated with geographic origin, with accessions from the two northernmost sites forming a distinct cluster. HPLC fingerprints identified 16 common peaks, among which five major bioactive constituents—madecassoside, asiaticoside, kaempferol, madecassic acid, and asiatic acid—were quantified. The total content of these five compounds varied markedly among accessions (4.09–20.18 mg·g⁻¹), with the highest found in Zhaoyang (S5). Most accessions exhibited high chemical similarity (>0.9), except for Yiliang (S12), which displayed a distinct profile. The partial correlation between SSR-based classifications and geographic origin, together with the inconsistency between phenotypic and chemical groupings, indicates that morphological variation is shaped by both environmental factors and complex genetic regulatory mechanisms. These findings provide a scientific basis for germplasm conservation, selective breeding, and the sustainable utilization of C. asiatica. Full article

Let R be a commutative ring. The comaximal graph $\Gamma \left(R\right)$ is defined as an undirected simple graph whose vertices correspond to the elements of R, where two distinct vertices x and y are adjacent if and only if $Rx+Ry=R$, with $Rx$ denoting the ideal generated by x. For the case $R={\mathbb{Z}}_n$, the ring of integers modulo n, the comaximal graph is represented as a generalized composition of appropriately chosen graphs. Building on this concept, we demonstrate that the comaximal graph $\Gamma \left(R\right)$ of any commutative Artinian ring with unity can be expressed as an H-join of the complete and null graphs. Utilizing this structural representation, we derive an explicit formula for the Wiener index of the comaximal graph associated with a commutative Artinian ring. Finally, we determine the spectrum of the comaximal graph for such rings. Full article

Soil meso- and micro-fauna are key components of forest soil ecosystems, but the effects of converting natural forests to monoculture or mixed plantations on their communities remain unclear. This study compared soil meso- and micro-fauna communities in monoculture (broad-leaved and coniferous) and mixed plantations converted from secondary forests in Northeast China. Results showed that monocultures significantly altered faunal community composition and reduced diversity, whereas mixed plantations maintained similar abundance and diversity to secondary forests. For instance, broadleaf monocultures exhibited a 15–23% lower Shannon–Wiener diversity index, while coniferous monocultures displayed a 28–35% reduction in soil faunal abundance. Notably, different taxonomic groups responded inconsistently to stand type conversion: Oribatida (58.8–72.5% of total individuals) varied significantly among stands (p < 0.001), whereas Collembola (18.8–31.4%) was more affected by season. The community composition was significantly correlated with understory plant diversity/coverage and soil C/N ratio, while α-diversity was mainly driven by total nitrogen. Our findings reveal that mixed plantations, instead of monocultures, are more effective for soil biodiversity conservation, which offers sustainable strategies for forest management. Full article

Grazing disturbance strongly affects grassland ecosystem structure and function, but its impacts on soil protist communities across vertical soil profiles remain unclear in alpine grasslands. We investigated soil protist community composition, alpha diversity, and their relationships with environmental factors under four grazing intensities (no grazing, light, moderate, heavy grazing) at three depths (0–10, 10–20, 20–30 cm) on the eastern Qinghai–Tibet Plateau. Our results showed that grazing significantly altered the relative abundance of dominant protist orders, including Pyrenomonadales, Kinetoplastida, and Amoebida. The Shannon–Wiener and Pielou indices of protists decreased significantly with increasing soil depth, while grazing mainly reduced the Margalef index. Soil total nitrogen, bulk density, and pH were the dominant factors shaping soil protist community structure. Overall, soil protists were more sensitive to soil depth than grazing intensity. These findings improve our understanding of vertical protist distribution under grazing disturbance and provide a scientific basis for sustainable grassland management. Full article

This study investigates the relationship between tree species diversity and soil quality in natural Pinus massoniana Lamb. forests, providing a scientific basis for the sustainable management of natural stands and the establishment of plantations. Located in Ganzhou City, Jiangxi Province, China, a subtropical region, the study focuses on natural P. massoniana forests. The Patrick richness index and Shannon–Wiener diversity index were each classified into three levels—low, medium, and high—to analyze how soil physicochemical indicators vary across these diversity levels. A minimum data set of key soil indicators was established to evaluate soil quality. Linear and nonlinear scoring functions were used to compare the relationships between the total data set and minimum data set-derived soil quality indices, and the most suitable scoring function for this study was selected. An obstacle factor diagnosis model was applied to identify the factors limiting soil quality improvement under different diversity levels. The results showed that (1) in the 20–40 cm soil layer, soil water content, maximum water-holding capacity, and total porosity significantly increased with rising Patrick richness and Shannon–Wiener diversity levels. (2) With increasing Patrick richness and Shannon–Wiener diversity levels, organic matter and total nitrogen in the 0–20 cm soil layer, as well as total potassium, available nitrogen, and pH in both the 0–20 cm and 20–40 cm soil layers, showed significant upward trends. In contrast, total phosphorus in both layers significantly decreased. Furthermore, available phosphorus in both layers significantly declined as Patrick richness increased. (3) The minimum data set based on the nonlinear scoring function can effectively substitute for the total data set (r = 0.791, R² = 0.63), showing better applicability for assessing soil quality changes in natural P. massoniana forests. Additionally, the soil quality index in the 0–40 cm soil layer significantly increased with rising Patrick richness levels. (4) At different Patrick richness levels, bulk density had the greatest impact on soil quality in the 0–40 cm soil layer, while organic matter had the least. A comprehensive analysis shows that there is a positive correlation between tree species diversity and soil quality in natural P. massoniana forests. In P. massoniana plantation practices, a near-natural management approach should be adopted to create relatively species-rich and complex coniferous and broad-leaved mixed stands, which is conducive to improving soil quality. Full article

Background: The Gansu Heihe Provincial Nature Reserve harbors rich plant and animal resources, yet its coleopteran fauna has remained taxonomically and ecologically uncharacterized. To address this gap, we conducted the first systematic survey of beetle diversity across four representative transects—Youcaigou (I), Zhugou (II), Loufangya (III), and Sigou (IV)—and assessed variation in community structure using the Shannon–Wiener diversity index, Margalef richness index, Berger–Parker dominance index, Pielou evenness index, and Jaccard similarity coefficient. Results: A total of 131 species belonging to 108 genera and 22 families were identified, establishing a comprehensive baseline of beetle diversity for the reserve. Cerambycidae was the most species-rich family (27 species), while Lampyridae, Staphylinidae, and Anobiidae were each represented by only a single species, reflecting marked unevenness in family-level composition. Diversity and community structure differed substantially among transects: Transect II showed the highest Shannon–Wiener diversity index and Pielou evenness, Transect III the lowest diversity, and Transect IV the greatest dominance by a few species, while species richness declined in the order I > II > III > IV. Zoogeographic analysis revealed that widely distributed (Cosmopolitan) species predominated (83 species; 63.36%), with Palaearctic (21 species; 16.03%) and Oriental (27 species; 20.61%) elements also well represented, underscoring the reserve’s position at a key biogeographic transition zone. Within China, North China faunal elements were most prevalent (75.94%), with the North China–Northeast China distribution group alone accounting for 54.20% of species, whereas nationally widespread species comprised only 9.16%. Conclusions: This study provides the first systematic record of coleopteran diversity in the Gansu Heihe Provincial Nature Reserve, enriching the region’s biodiversity inventory and offering reference data for future insect monitoring and forest conservation. Further multi-seasonal, method-diversified surveys are needed to achieve a complete faunal inventory. Full article

Biological invasions and environmental gradients are major drivers of biodiversity change in wetland ecosystems, but their associations on native plant diversity in Central Asian riverine wetlands remain poorly understood. We surveyed 158 wetland plant communities across 54 transects in the Ertix River Basin to examine how environmental gradients (elevation, mean annual temperature [MAT], and mean annual precipitation [MAP]) and non-native plant establishment jointly related to native plant importance values and alpha diversity indices. Non-native plants were classified according to invasion stage—non-naturalized, naturalized, and invasive—to elucidate how the associations between alien plants and native communities shift dynamically along the invasion continuum. Elevation emerged as the dominant predictor, explaining 82% (individual R² = 0.15) of the variance in native species richness and 63.37% (individual R² = 0.1) of the variance in the Shannon–Wiener diversity index, while MAT and MAP were not retained as significant predictors in the optimal models. Native plant importance values, richness, and diversity all increased with elevation. Unexpectedly, naturalized plant richness and abundance were positively associated with native diversity metrics, contrasting with the negative associations of all non-native categories (non-naturalized, naturalized, and invasive) on native importance values, partly reflecting the compositional nature of this metric. Our results reveal positive co-occurrence patterns between early-stage naturalized species and native species, but native dominance may eventually decline as invasion intensity increases. These findings highlight the importance of considering invasion stage when predicting wetland biodiversity responses to biological invasions under environmental heterogeneity. Full article

As an artificial–natural composite ecosystem, polders face increasingly prominent internal and surrounding water environment problems under sustained strong human activities. To systematically assess the water ecological health status of polders around Dongting Lake, this study took four typical polders around Dongting Lake as research subjects, and two seasonal surveys of benthic macroinvertebrates were carried out in July and December 2024. Through analyses of community structure characteristics and correlations with key environmental factors, the Trophic Level Index (TLI), Water Quality index (WQI), Shannon–Wiener index of benthic macroinvertebrates, and Benthic Macroinvertebrates Index of biotic integrity (B-IBI) were selected to establish an entropy-weighted Bayesian model for comprehensive evaluation of the current ecological health of Dongting Lake polders. In 2024, a total of 47 benthic macroinvertebrate species were found in Dongting Lake polders, including 25 species in the summer and 36 species in the winter. The main groups were Gastropoda, Insecta, and Bivalvia, and the community composition did not show significant seasonal or spatial differences. The benthic macroinvertebrate community structure in the summer was mainly influenced by TN/TP, NO₃⁻-N, WD, Tur, and Chl.a, suggesting eutrophication as a critical concern, while in the winter it was mainly regulated by WSW, WT, Tur, and DO, highlighting hydrological conditions as pivotal. The entropy-weighted Bayesian assessment indicated an overall aquatic ecological health status of “moderate” in 2024, with summer conditions superior to those in the winter and notable spatial heterogeneity observed in winter sampling sites within ditches, among which Polder Chengxi exhibited the best condition, while Polder Junshan and Polder Xiangbin Nanhu showed degraded states. Notably, Polder Junshan (JS2 and JS3) displayed clear signs of ecological degradation during the winter, warranting immediate initiation of targeted restoration measures. This study provides a systematic diagnosis and scientifically grounded evaluation of aquatic ecological health in Dongting Lake polders, offering a robust theoretical framework and empirical data for future water environmental protection strategies and ecological restoration practices. Full article

Revealing scale effects and the mechanisms underlying the relationships between plant species and functional diversity is crucial for understanding the stability of desert ecosystems and formulating multiscale conservation strategies. In this study, the spatial patterns of plant species and functional diversity in the Gurbantunggut Desert were analysed via multiscale grid sampling. The results indicated that (1) both species diversity and functional diversity indices exhibited high spatial heterogeneity. At the small scale (10 m × 10 m), the values of the Shannon–Wiener and Pielou indices for fixed dunes were higher in the south than in the north. At the medium and large scales (20 m × 20 m and 50 m × 50 m, respectively), the index values were highest in the southwest, with generally greater values in the south than in the north. For semifixed and mobile dunes, the Shannon–Wiener and Pielou index values exhibited an east-high–west-low pattern at the 10 m × 10 m scale. This differentiation decreased with increasing scale, with the highest values observed in the northeast and southwest at the 50 m × 50 m scale. The spatial differentiation in functional diversity indices (Rao’s second-order entropy index and functional evenness index) exhibited distinct characteristics across the different dune types. (2) The spatial variation in all the diversity indices monotonically decreased with increasing scale, with the variance in the species diversity indices indicating the following order: Shannon–Wiener index > Pielou index > Simpson index. (3) The relationships between species richness and diversity indices exhibited significant scale dependence. At the small and medium scales, species richness was significantly positively correlated with the Shannon–Wiener index, Simpson index, and Rao’s quadratic entropy index and significantly negatively correlated with the Pielou evenness index and functional evenness index. However, at the large scale, none of these correlations were significant. (4) The species diversity indices and Rao’s quadratic entropy index were significantly positively correlated at the small and medium scales (p < 0.01), whereas a significant positive correlation with the functional evenness index was observed only at the 10 m × 10 m scale (p < 0.01). At the larger scale, these correlations became insignificant. In fixed dunes, areas of high Simpson index values exhibited a spatially complementary distribution with areas of high Shannon–Wiener index and Pielou index values, providing evidence for the combined effect of local processes such as competitive exclusion and dispersal limitation. Through comprehensive multiscale analysis, this study revealed the mechanisms underlying the scale-dependent relationships between plant species and functional diversity, thereby providing a theoretical basis for protecting and restoring desert biodiversity. Full article

This study presents a systematic terahertz time-domain spectroscopy (THz-TDS) investigation of hardened cement paste, framed as a complex-optical measurement in which the real and imaginary parts of the response probe distinct microstructural attributes. Transmission-mode measurements were made on pastes with water-to-cement (w/c) ratios of 0.3, 0.4, and 0.5 at curing ages of 7, 14, 28, and 56 days. The effective refractive index, obtained from the time-domain pulse delay (7, 28, and 56 days, paired with mercury intrusion porosimetry), correlates strongly and linearly with porosity over nine porosity-paired conditions spanning 15.1–30.4% (pooled R² = 0.94, p < 0.001). In a quasi-static effective-medium framework—where the pores a re far smaller than the THz wavelength—this reflects the dependence of the effective permittivity on the solid volume fraction: the Bruggeman model outperforms the Maxwell–Garnett model, and all data fall within the Wiener bounds, lying close to the upper bound, indicating a continuously connected solid matrix with isolated pores. Cross-validated porosity estimation is reliable to within about ±2 percentage points (refractive-index uncertainty ±0.02–0.04). The absorption follows a power law (β ≈ 1.0–1.3) characteristic of disorder-activated vibrational absorption, in which the loss of long-range order in the amorphous C–S–H relaxes the crystalline selection rules and couples the THz field to the full vibrational density of states. The refractive index (structure-sensitive, governed by volume fraction) and the absorption (material-sensitive, governed by solid disorder; estimated loss tangent of order 0.1) thus form two complementary channels. Combining the THz-derived porosity with the Powers hydration model gives a degree of hydration consistent with literature ranges—an indirect comparison rather than direct validation. These results establish THz-TDS as a non-contact, non-ionizing technique for rapid porosity estimation and hydration assessment of cementitious materials. Full article

Alpine shrub meadows on the Qinghai–Tibet Plateau are key warm-season pastures that support pastoral production and ecosystem stability in fragile high-elevation regions. Due to low temperatures, short growing seasons, and slow vegetation recovery, these pastures are highly sensitive to inappropriate grazing management. However, the effects of different grazing–rest time configurations on plant community composition and leaf functional traits in alpine shrub meadows remain insufficiently understood. In this study, we evaluated five grazing treatments in an alpine shrub meadow in Sunan County, central–eastern Qilian Mountains: 10 days grazing–20 days rest (T1), 15 days grazing–15 days rest (T2), 20 days grazing–10 days rest (T3), continuous grazing (CG), and grazing exclusion (CK). In the third year of treatment implementation, we measured the community diversity, species importance values, and leaf functional traits of four dominant species: Elymus nutans, Carex tibetikobresia, Oxytropis kansuensis, and Bistorta vivipara. T1 and T2 significantly increased species richness, Shannon–Wiener diversity, and Simpson diversity compared with CG and CK. NMDS and PERMANOVA further showed significant differences in overall community composition among grazing treatments. Grazing generally reduced the leaf length, leaf width, and leaf area, whereas T2 showed relatively stronger leaf recovery among grazing treatments. Specific leaf area, specific leaf weight, and leaf length–width ratio showed higher variability and calculated plasticity than leaf thickness and leaf dry matter content, suggesting that resource-acquisition and morphological traits were more responsive to grazing than conservative structural traits. The coefficient of variation of leaf traits was positively associated with the plasticity index, although this association should be interpreted cautiously because both indices were calculated from the same underlying trait dataset. Overall, under the conditions of this three-year, single-site experiment and a target moderate grazing intensity, the 15-day grazing–15-day rest regime performed best among the tested treatments. This regime may provide a practical reference for rotational grazing management in similar warm-season alpine shrub meadows, but its broader applicability requires further validation across different grassland types, grazing intensities, climatic conditions, and longer monitoring periods. Full article

Vegetation restoration is an effective measure to improve soil carbon storage in rocky desertification areas. However, the underlying mechanisms driving differences in soil carbon storage among different vegetation types remain unclear. In this study, we selected four typical vegetation types (monospecific broadleaf plantation, mixed conifer–broadleaf plantation, monospecific coniferous plantation, and natural shrubland) from the comprehensive control zone for moderately rocky desertification of Xuyong County in the Chishui River Basin. We investigated the effects of vegetation patterns on soil carbon storage through tree layer functional traits, tree diversity, shrub layer functional traits, shrub diversity, and soil fungal/bacterial diversity. The results showed that soil carbon storage was highest in monospecific broadleaf plantations, followed by mixed conifer–broadleaf plantations, then natural shrubland, and it was lowest in monospecific coniferous plantations. Significant differences were mainly observed in the 0–10 cm and 10–20 cm soil layers, while no significant difference was found in the 20–30 cm layer. Tree layer community-weighted mean of leaf nitrogen content, soil fungal Shannon–Wiener index, and shrub layer community-weighted mean of specific leaf area were the core positive drivers of soil carbon differentiation. Among these, tree layer community-weighted mean of leaf nitrogen content was the most important factor, whereas the regulatory effect of shrub layer community-weighted mean of specific leaf area intensified with increasing soil depth. Furthermore, tree layer community-weighted mean of leaf nitrogen content and shrub layer community-weighted mean of specific leaf area not only directly promoted soil carbon accumulation but also indirectly promoted it by enhancing soil fungal diversity. In contrast, the effects of tree and shrub layer diversity and soil bacterial diversity were negligible. This study demonstrates that increasing soil carbon storage in rocky desertification ecosystems depends on the direct effect of soil fungal diversity, as well as the direct effects of tree and shrub layer functional traits and their indirect effects via regulating soil fungal diversity. We recommend that in moderately rocky desertified areas, priority should be given to tree species with high leaf nitrogen content; on sites unsuitable for afforestation, promoting natural shrublands with high specific leaf area can effectively enhance carbon sequestration capacity. Full article

Sugarcane is a high-value crop in Egypt, yet weed communities in the understudied Upper Egypt region have not been systematically characterized. This study provides a comprehensive analysis of weed floristic composition, phytogeographical affinities, and the edaphic and canopy light factors governing vegetation structure across contrasting Nile Valley clay and reclaimed desert lands in Qena Governorate. Fourteen stands were surveyed during the 2024/2025 sugarcane growing season, recording 110 species from 33 families (68 annuals and 42 perennials), which were dominated by Poaceae, Asteraceae, Fabaceae, Euphorbiaceae, and Amaranthaceae (54.6% of the flora recorded). Therophytes were the most abundant life form (60.9%), and 51.8% of species belonged to Neotropical, Palaeotropical, Cosmopolitan, and Pantropical chorotypes. Diversity indices showed high and balanced species diversity, with no dominance by any single species. Seasonal variation showed that species richness peaked in spring, decreased through summer and autumn, and correlated with light intensity under the canopy. TWINSPAN identified four vegetation groups, which were merged into three primary vegetation groups (A, B, and C) via DCA and CCA ordinations and linked to microhabitats shaped by elevation and soil physicochemical properties. CCA revealed that Group C (stands in the Nile Riverbank lands) had the highest diversity, which was associated with organic matter, clay, and field capacity. In contrast, Group A (stands of reclaimed desert land) had low richness linked to high levels of Total Dissolved Solids (TDS), Electrical Conductivity (EC), Na, K, Mg, CaCO₃, and sandy soils. Group B (stands of Nile clay lands) was an intermediate transitional community between groups A and C. These findings establish edaphic factors as the primary determinant of weed community structure, with salinity as the critical constraint in reclaimed lands and seasonal light variation as a secondary diversity filter. Full article