Hao Zhang

Previous studies often overlooked the dynamic effects of karst vegetation restoration on soil multi‐trophic biodiversity and the underlying community‐assembly mechanisms. To fill this gap, we performed a seasonal comparative analysis of soil biodiversity, co‐occurrence network architecture, and assembly processes across three representative karst restoration patterns (grass, forest‐grass, and forest). During the wet season, the grass pattern exhibited significantly lower biodiversity than both the forest‐grass and forest patterns by 17%–49%. In the dry season, the forest pattern achieved the highest biodiversity indices and displayed minimal seasonal fluctuation. Vegetation type and season jointly shaped soil biotic co‐occurrence networks: the forest–grass pattern generated the greatest network complexity and connectivity, whereas the dry season fostered tighter network structures. The bacterial community was predominantly driven by heterogeneous selection with a relatively high contribution in the wet season, whereas it was dominated by dispersal limitation in the dry season. In contrast, the fungal community was largely influenced by dispersal limitation across seasons. As for the protist and nematode communities, undominated accounted for a relatively high contribution in the wet season, while dispersal limitation became the dominant driver in the dry season. Moreover, soil moisture, nutrient status, biodiversity, and network properties emerged as the principal drivers of assembly, with their pathways varying by taxon and season. Collectively, our reveal integrated regulation of soil biotic communities by restoration pattern and seasonal dynamics in karst ecosystems, offering a robust theoretical basis for soil‐biota recovery.

Current research has confirmed that forest productivity in non‐karst regions is closely related to biodiversity. However, the relationship between forest productivity and multi‐trophic biodiversity remains unclear in karst habitats, characterized by thin soil layers and limited soil nutrients. To better understand the productivity of natural and planted forests in karst regions and main impact factors on the forest productivity, we selected restored karst forests in the southwest of China. By using methods such as high‐throughput sequencing, the Mantel test, random forest model, and structural equation model, we analyzed the differences in productivity, habitat factors, and multi‐trophic biodiversity between natural forests and planted forests and explored the key influencing factors for productivity of karst forests. The findings indicated that the aboveground, belowground, and total productivity of planted forests were significantly higher than those of natural forests. Conversely, the soil nutrient stocks, multi‐trophic biodiversity, and plant diversity of natural forests were significantly higher than those of planted forests. Moreover, the complexity of the multi‐trophic co‐occurrence network in planted forests was higher than that in natural forests. The Mantel test revealed significant positive correlations between soil nutrient stocks, soil moisture content, altitude, slope position, soil layer thickness, multi‐trophic biodiversity, and forest aboveground productivity, belowground productivity, and total productivity. The random forest model identified soil nutrient stocks as the most significant factor influencing the karst forest productivity. The structural equation model showed that stand characteristics, soil nutrient stocks, and multi‐trophic biodiversity collectively explained 69% of the total productivity variation. Forest type could not only directly impact the total productivity but also affect the total productivity along with the changes in soil nutrient stocks. This study is conducive to a deeper understanding of the formation mechanism of productivity in Southwest karst forests.

As geologically unique landforms characterized by extreme micro‐topographic heterogeneity (peak‐depression coupling) and intense human‐land contradictions, karst peak‐cluster depressions represent globally significant yet ecologically fragile landscapes fundamentally distinct from non‐karst ecosystems in their water‐soil‐nutrient coupling processes. Understanding ecosystem service (ES) relationships in these geomorphologically complex regions is critical for optimizing ecological restoration. This study analyzed spatiotemporal dynamics and drivers of five ES (water yield, sediment retention, nitrogen export, carbon sequestration, and habitat quality) in a representative karst peak‐cluster depression from 2005 to 2020. Results revealed pronounced temporal fluctuations in water yield and soil retention compared to stable carbon sequestration and habitat quality, alongside marked spatial heterogeneity governed by topography and land use. Significant trade‐offs dominated between habitat quality and nitrogen export (56.14% pixel ratio)/sediment retention (54.02%), water yield and sediment retention (53.94%), and carbon sequestration and nitrogen export (53.09%), primarily in southern high‐altitude and northern lowland regions. Conversely, synergies prevailed between sediment retention and nitrogen export (61.29%) and habitat quality and carbon sequestration (55.93%). Geodetector analysis identified annual precipitation, evaporation, and slope as primary drivers, with two‐factor interactions (particularly precipitation‐evaporation) exhibiting substantially stronger explanatory power (q‐values up to 0.857) than individual factors. These findings highlight that ES relationships in karst depressions are shaped by coupled climatic‐topographic controls rather than single determinants. We advocate spatially differentiated zoning strategies—including hydrogeological nitrogen interception, slope‐threshold land‐use planning, and climate‐adaptive vegetation configuration—to balance inherent trade‐offs between water yield and soil/carbon retention, thereby supporting sustainable development in vulnerable karst regions.

In the highly heterogeneous and fragile karst forest ecosystem, existing research on single trophic levels fails to explain the maintenance of ecosystem multifunctionality (EMF). Moreover, integrated studies adopting multitrophic perspectives remain scarce. Therefore, this study focuses on investigating the driving mechanisms of multitrophic biodiversity on EMF. Our study explores the link between multitrophic diversity and EMF in karst forests, assessed the diversity of six trophic groups: plants, bacteria, fungi, protists, nematodes, and arthropods. We established both belowground and aboveground–belowground multitrophic co‐occurrence networks, concurrently assessing eight key ecosystem functions associated with material cycling and biomass production. Biodiversity (particularly that of plants, soil bacteria, and nematodes) showed significant positive correlations with EMF, and the multitrophic diversity index exhibited stronger predictive power than any single‐trophic‐level index. The topological properties of multitrophic co‐occurrence networks (such as negative edge count, edge density, centralization, and relative modularity) are significantly closely linked to EMF. Notably, the predictive and explanatory power of network complexity integrating aboveground and belowground organisms for EMF is significantly stronger than that of networks containing only soil organisms. Structural equation modeling revealed that plant diversity and multitrophic network complexity had a direct positive effect on EMF, while multitrophic diversity primarily enhanced EMF indirectly by promoting network complexity. Environmental factors, in turn, indirectly influenced EMF by modulating these biological components. Multitrophic network complexity exhibited the largest standardized total effect among all factors, highlighting its central role in maintaining EMF. We conclude that maintaining EMF in karst forests should prioritize conserving the overall complexity of cross trophic biotic interaction networks rather than focusing solely on species richness.

Introduction: The revelation of the assembly mechanism of plant communities in karst region has crucial implications for the restoration of degraded vegetation. Niche theory and neutral theory are the two main theories to elucidate community assembly of karst plant community. However, the relative significance of habitat filtration and biological action in community assembly remains a topic of debate. Methods: By using measurement of plant functional traits, detection of phylogenetic signal (K value), and average shared variance, our investigation aimed to ascertain whether species coexistence in community assembly of primary forest is driven by habitat filtering or biotic constraints. Results: In all 10 plant functional traits, leaf carbon (LC) had the lowest variation coefficient, whereas leaf area (LA) exhibited the highest. Significant phylogenetic signals ( P < 0.05) were identified for plant LC, LA, wood density (WD), leaf nitrogen (LN) and leaf phosphorus (LP). Phylogenetic signal strength (K < 1) of all traits indicated that the phylogenetic conservation of functional traits is relatively weak and may be influenced by environmental screening or convergent evolution. Both the phylogenetic net relatedness index (NRI) and nearest taxon index (NTI) were negative, indicating a divergent phylogenetic structure. Additionally, with the exception of LA and leaf length-width ratio (L/D), the mean pairwise trait distance indices (SES.PW) were greater than 0, suggesting a tendency towards aggregation in the functional trait structure. Furthermore, average shared variance demonstrated that variation in plant functional trait was predominantly influenced by soil fertility and topography of the sample Discussion: Our finding indicated that the community assembly of primary forest plant was dominated by habitat filtering, which could significantly promote a more profound comprehension of natural restoration in karst degradation region.

Under the background of the large‐scale Grain for Green Project (GGP) in southwest China, studies have primarily examined the impacts of vegetation restoration on individual soil functions. However, there is a pressing need to intensify research on soil multifunctionality (SMF). By using random forest and structural equation model, this research examined the variation of SMF across three land cover (LC) types, using karst converted crop to forest and grassland, and explored the relationship between SMF and factors such as LC, soil properties, diversity, and the complexity of the co‐occurrence network of microbiology. The nutrient supply, labile organic matter (LOM) decomposition, SMF in grassland soil, and LOM decomposition in plantation soil were significantly higher than those in crop, by 21.66%, 88.35%, and 41.92%, respectively. Conversely, the nutrient supply and SMF in plantation soil were significantly smaller than those in crop. Fungal richness, phylogenetic diversity, and complexity of the microbial co‐occurrence network in grassland and plantation soil were significantly higher than those in crop. Random plantation model analysis indicated that LC, soil moisture (SM), soil pH, and bacterial network complexity (BNC) were the main influencing factors of SMF. The structural equation model demonstrated that SM and soil pH significantly affected BNC, thereby influencing SMF. These findings suggested that SMF was determined by LC and soil‐microbiological properties in the karst region. Furthermore, soil BNC influenced SMF by regulating microbial interspecies relationships (symbiotic). These insights may contribute to understanding the impact mechanism of reforestation and grassland on SMF in karst areas from a soil microorganism perspective.

As the climax community of karst in southwest China without human disturbance, the mechanisms through which biodiversity maintains ecosystem multifunctionality (EMF) in evergreen and deciduous broad‐leaved mixed forest are still unclear. This study employed structural equation modeling to analyze the correlations between EMF and three key variables: plant diversity, soil microbial diversity, and rock exposure ratio within this karst forest. Plant and soil microbial diversity were the main biotic drivers of EMF. Within these biotic factors, soil microbial diversity provided a preferable explanation for EMF compared to plant diversity, with fungal diversity and the co‐occurrence network complexity playing dominant roles. Functional, species, and phylogenetic diversity indices of plant explain the changes in EMF better than the community‐weighted mean of traits, indicating that the niche complementarity hypothesis holds greater relevance in explaining the biodiversity‐maintenance mechanism of EMF. Moreover, the rock exposure ratio directly affects EMF as well as indirectly through plant diversity. Collectively, soil microbial diversity, plant diversity, and rock exposure ratio account for 87% of the variability in EMF. Specifically, plant diversity, fungal diversity, and its co‐occurrence network complexity exerted a positive and direct impact on EMF, while bacterial diversity mainly affected EMF by positively contributing to fungal co‐occurrence network complexity. These findings emphasized the significance of comprehensive protection of aboveground and underground biodiversity and have strengthened our comprehension of the biodiversity‐maintenance mechanisms of EMF in karst forests.

Introduction: The Grain for Green Project (GGP) by the Chinese government was an important vegetation restoration project in ecologically fragile and severely degraded karst regions. Soil fungi play a facilitating role in the cycling of nutrients both above and below the ground, which is crucial for maintaining ecosystem function and stability. In karst regions, their role is particularly critical due to the unique geological and soil characteristics, as they mitigate soil erosion, enhance soil fertility, and promote vegetation growth. However, little is known about how the implementation of this project shifts the co-occurrence network topological features and assembly processes of karst soil fungi, which limits our further understanding of karst vegetation restoration.Methods: By using MiSeq high-throughput sequencing combined with null model analysis technology, we detected community diversity, composition, co-occurrence networks, and assembly mechanisms of soil fungi under three GGP patterns (crop, grassland, and plantation) in the southwestern karst region.Results: Ascomycota and Basidiomycota were the main fungal phyla in all the karst soils. Returning crop to plantation and grassland had no significant effect on α diversity of soil fungi (P > 0.05), but did significantly affect the β diversity (P = 0.001). Soil moisture and total nitrogen (TN) were the main factors affecting the community structure of soil fungi. Compared with crop, soil fungi networks in grassland and plantation exhibited a higher nodes, edges, degree, and relatively larger network size, indicating that vegetation restoration enhanced fungal interactions. The soil fungi networks in grassland and plantation were more connected than those in crop, implying that the interaction between species was further strengthened after returning the crop to plantation and grassland. In addition, null-model analysis showed that the assembly process of soil fungal communities from crop to grassland and plantation shifted from an undominant process to dispersal limitation.Discussion: These data indicated that GGP in karst region changed the composition and assembly mechanisms of the soil fungal community and enhanced the interaction between fungal species, which can contribute to a better understanding of the fungal mechanisms involved in the restoration of degraded karst soils through vegetation recovery.