Jinliang Liu

Different mycorrhizal types in plants exhibit distinct strategies for resource acquisition and environmental adaptation. Elevation integrates multiple environmental factors and influences community structure and species diversity in mountain ecosystems. However, how tree species with different mycorrhizal types vary in diversity-elevation patterns remains poorly understood. A 3210 m continuous elevational transect (636–1928 m a.s.l.) was established in Baishanzu National Park, China, and we surveyed adult trees and saplings of three mycorrhizal types: arbuscular mycorrhizal (AM), ectomycorrhizal (EcM), and ericoid mycorrhizal (ErM). We calculated Hill indices (q = 0, 1, 2) to compare diversity-elevation patterns among mycorrhizal types and life stages. Bray-Curtis and Sørensen indices were used to quantify elevational changes in species composition dissimilarity between adults and saplings. Results showed that AM trees consistently exhibited higher species diversity than EcM and ErM trees. Elevation was the primary driver of diversity across all mycorrhizal types. AM diversity showed a hump-shaped relationship with elevation, whereas EcM and ErM declined monotonically with increasing elevation. Across all mycorrhizal types, adults showed a consistent hump-shaped elevation pattern, while saplings shifted from hump-shaped to monotonically decreasing patterns as q increased with abundant species weighted. Species composition dissimilarity between adults and saplings increased with elevation for AM trees, declined for EcM trees, and showed an inverse hump-shaped pattern for ErM trees. Overall, our findings reveal elevational diversity trajectories and regeneration dynamics among mycorrhizal types, highlighting the crucial role of mycorrhizal associations in shaping diversity-elevation relationships by mediating species abundance and regeneration across life stages in mountainous forests.

Montane shrubby grasslands, as one of the world’s important ecosystems, are highly sensitive to climate change and human activities, especially in the subtropical regions experiencing rapid economic development. However, little is known about how anthropogenic activities, such as firebreak construction, interact with elevation to influence plant diversity in these ecosystems. Shrub and herbaceous communities were surveyed in subtropical montane shrubby grassland within Baishanzu National Park, eastern China. Nine transects were established along firebreaks, each with two edge plots near firebreak and two interior plots away firebreak, and twelve additional control plots in adjacent undisturbed areas. Species diversity was assessed using the Hill index. Our results revealed distinct responses of shrubs and herbs to firebreak disturbance and elevation. Firebreaks reduced shrub diversity but enhanced herb diversity, and both groups exhibited contrasting elevational patterns. In control areas, shrub diversity decreased while herb diversity increased with elevation, whereas in firebreak zones, these relationships were altered, with edge plots showing a hump-shaped diversity pattern. Differences in shrub diversity but not herbs between interior and edge plots decreased with elevation. Species composition also differed significantly between firebreak and control areas, driven mainly by elevation in control areas and by soil properties near firebreaks. These findings demonstrate that firebreak construction reshapes the elevation–diversity relationships of both herbs and shrubs, highlighting the sensitivity of high-elevation montane shrubby grasslands to small-scale disturbances. Effective firebreak management should therefore account for both elevational context and disturbance intensity to maintain ecosystem biodiversity and stability.

Density dependence, both conspecific and heterospecific, is widely recognized as a crucial driver of plant species diversity. However, treating multiple heterospecific species as a homogeneous group obviously overlooks the variability in the impacts of different heterospecific neighbors on the survival or growth of focal species. In this study, we developed the Static-Dynamic Coupled Interspecific Association Classification Framework (SDIACF), which categorizes heterospecific neighbors based on their positive/negative interspecific associations and dynamic changes with focal species. We further used generalized linear mixed-effect models to analyze how conspecific and various heterospecific neighbors classified by the above framework influenced the survival and growth rates of the focal species. Our results revealed that heterospecific neighbors, deconstructed using SDIACF, exerted distinct effects on the focal species. Specifically, regardless of their initial interspecific association with the focal species, heterospecific neighbors with more negative associations showed a negative impact on the focal species, while those with more positive associations showed a positive effect. However, among heterospecific neighbors exhibiting identical dynamic interspecific associations, positively associated neighbors were slightly more conducive to the survival of the focal species than negatively associated ones, but slightly detrimental to its growth. In summary, our results demonstrate that heterospecific neighbors are not a homogeneous entity but play important and complex roles in species coexistence. The development of SDIACF not only constitutes a significant supplement to traditional density dependence research but also offers a novel perspective for further exploring species coexistence.

Managing invasive species requires identifying the factors that determine alien species invasion success. This study investigates how anthropogenic and biogeographical factors influence alien plant invasion in the Sanyang Wetlands, a human-dominated island system in Wenzhou City, China. Specifically, we analyzed whether human activities (e.g., habitat heterogeneity, proportion of road area, and cultivation) and island characteristics (e.g., island area, isolation) affect the diversity of native and invasive plant species similarly. We also assessed the applicability of the equilibrium theory of island biogeography to invasive plant species diversity and examined how these factors affect invasive plant species with different dispersal syndromes (anemochore, zoochore, and autochore). We found that both invasive and native species richness positively correlate with island area, habitat heterogeneity, and proportion of road area. However, although native species richness was negatively correlated with isolation, invasive species richness was not. The diversity and composition of invasive species with different dispersal syndromes were determined by different variables; for example, the composition and diversity of zoochores was increased by habitat heterogeneity, while anemochore species richness was increased by the proportion of road area, whereas anemochore species composition was influenced by distance to the nearest island. We conclude that habitat fragmentation differentially affects invasive and native plant diversity, aligning with the predictions of the equilibrium theory of island biogeography only for native species but not for invasive species. Our findings indicate that tailoring habitat attributes and regulating human activities could be effective strategies for mitigating the spread of invasive species in fragmented landscapes.

Habitat fragmentation is associated with decreased species diversity. However, the effects of fragmentation on the processes that maintain diversity, such as enemy‐mediated negative conspecific density dependence (CDD), are largely unknown. We examined how negative CDD in seedling survival is influenced by habitat fragmentation. We measured the effect of conspecific density on seedling survival of 30 species for 10 years on 25 islands in an artificially fragmented habitat and took parallel measurements of the potential drivers: soil physical and chemical properties, and insect herbivore communities. Increasing densities of conspecific trees and seedlings reduced seedling survival more on larger and more isolated islands. These processes were linked to increases in insect herbivore richness on larger islands, and less fertile soils on more isolated islands. Synthesis. Our results indicate that shifts in the abiotic and biotic conditions of fragmented habitats can modify the mechanisms thought to maintain species coexistence, perhaps contributing to the long‐term decay of fragmented ecosystems, and suggesting approaches for restoration. The relationships between island configuration, and insect herbivore communities and soil properties may vary among ecosystems, which could help explain variation among studies in the effects of fragmentation on biodiversity.

Climate change is compelling species to seek refuge at higher elevations and latitudes. While researchers commonly study these migrations using discontinuous elevational transects, this methodology may introduce significant biases into our understanding of species movement. These potential biases could lead to flawed biodiversity conservation policies if left unexamined. To address this concern, we utilized species distribution data from a novel continuous elevational transect to evaluate the accuracy of discontinuous transect methods. Our analysis focused on how quadrat spacing and survey time intervals affect bias in estimating species range shifts. The results were striking: the widely used settings for discontinuous transects failed to detect 7.2% of species, inaccurately estimated shift distances for 78% of species, and produced an overall error rate of 86%. Wider quadrat spacing increased these error rates, while longer survey intervals generally reduced them. Moreover, discontinuous transects consistently underestimated species shift distances, with this underestimation becoming more pronounced over longer survey periods. Our pioneering assessment of bias in discontinuous elevational transects demonstrates that a 50 m quadrat spacing combined with a 60-year survey interval optimizes monitoring species range shifts for conservation planning. This baseline protocol could be further strengthened through supplementary, frequent surveys targeting high-elevation species—a strategic approach that maximizes accuracy while maintaining cost-effectiveness.

Aims: The relationship between habitat area and species evenness quantifies species relative abundance distribution changes across habitat fragments, providing more information than considering only the species richness to predict biodiversity distribution patterns in fragmented landscapes. However, unlike the species‐area relationships (SARs), the Species Evenness‐Area Relationship (SEARs) has yet to be explored across taxa at a large spatial scale. Here, we resolved how the relationship between species evenness and fragment area varies among taxonomic groups and environmental factors.Location: Global.Taxa: Insecta, Aves, Amphibians and Squamata, Plantae, Arachnida, Mammalia, Mollusca.Methods: We compiled 67 datasets from the FragSAD database, including information on fragments area, species richness, and species abundance of six taxa worldwide. We calculated the species evenness index for each fragment, which is independent of species richness, and tested the relationship between species evenness and fragment area across taxonomic groups. We also used the power model to fit SEAR for each dataset and identified landscape variables with a detectable impact on the occurrence of significant SEARs.Results: In contrast to the positive relationship between species richness and fragment area, species evenness was negatively affected by fragment area when controlling for other environmental factors and the relationships varied significantly among taxonomic groups. Specifically, there were significant negative associations between species evenness and fragment area for insects, birds, spiders, and mammals but not for plants and amphibians. Meanwhile, the occurrence of significant SEARs depends on the number of fragments and total fragment area.Main Conclusions: The contrasting patterns of SEARs and SARs among taxonomic groups highlight the complexity of the mechanisms regulating biodiversity patterns. Although the number of species increases with the increase of fragment area, the decreased evenness implies community instability on larger fragments. Therefore, understanding the prevalence and underlying mechanisms in determining SEARs has critical implications for biodiversity conservation.