Community phylogenetic structure and diversity analysis are useful complements to species-centric approaches in biodiversity studies by providing new insights into the processes that drive community assembly. In this study, we aimed to understand the differences in the relative importance of abiotic filtering, biotic interactions, and dispersal limitation on community assembly of trees at different vegetation growth stages. We also examined the influence of geographical distance, elevation, terrain, and soil. Thus, we examined the phylogenetic structures and β-diversities of saplings and adults along different abiotic gradients. The results of the net relatedness index (NRI) showed that, instead of being random, the phylogenetic structure of saplings tended to be convergent, whereas that of adults tended to be divergent. This result implies that the relative forces of abiotic filtering and biotic interactions change throughout vegetation growth. The results of generalized dissimilarity modelling (GDM) showed that dispersal limitation (geographical distance) and abiotic filtering influenced the community assembly of both adults and saplings. This result confirmed our hypothesis that both deterministic and stochastic processes were prevalent. The explanatory rates of geographic distance and environmental factor distance to phylogenetic β-diversity were quite different between adults and saplings, which meant that the relative force of dispersal limitation and abiotic filtering had also changed.

Tree peony (Paeonia ostii) is widely cultivated in China as a traditional medicine and a new high-quality woody oil crop. Enhancing seed yield has become a primary breeding objective in the industrial development of oil tree peonies. Pollination and successful fertilization are essential for optimal seed yield. However, the molecular mechanisms underlying pollination and fertilization in P. ostii remain unclear. In this study, comparative transcriptomic and genetic analyses were conducted to investigate the pistils under different pollination periods of P. ostii ‘Fengdanbai’. Compared with pre-pollination, differentially expressed genes (DEGs) were screened from pistils 48 h after pollination, when most of the pollen tubes had reached the bottom of the style. Functional annotation indicated that these DEGs were involved in hormone signaling and carbohydrate metabolism pathways. Transcription factors and receptor-like kinases play a key role in pollen development, pollen tube growth, and carpel development. Key DEGs (PoUNE10 and PoLIM1) influenced pollination and fertilization and were characterized. Phylogenetic, promoter, and co-expression analyses suggest that they may affect plant pollination, fertilization, and seed yield through pathways such as hormone signaling and photosynthesis in P. ostii ‘Fengdanbai’. Our findings illustrate the molecular changes after pollination and fertilization in P. ostii ‘Fengdanbai’ and provide the molecular characterization of two key genes. These results provide insights into the molecular mechanisms underlying pollination and fertilization in tree peony and suggest potential candidate genes for molecular breeding aimed at improving seed yield in the species.

The accumulation of microplastics and plant invasion are significant environmental challenges facing ecosystems. However, existing research has mainly examined the responses of individual plant species or several species to microplastic contamination. The outcome of competition between invasive and native species is a key determinant of invasion success, yet how different types of microplastics influence interspecific interactions between native and invasive plants remains unclear. In this study, we assessed the impacts of two common microplastics, polyethylene (PE) and polypropylene (PP), on the growth performance and interspecific relationships using three pairs native-invasive species pairs. We found that both PE and PP impaired the growth of all three native–invasive species pairs, with PP exerting a stronger inhibitory effect. In the absence of microplastic addition, invasive and native species showed no significant interspecific effects, and invasive species did not display a higher relative dominance index (RDI) than their native counterparts. However, under different microplastic treatments, the invasive species gains a competitive advantage over the native species, albeit through different mechanisms: under PP treatment, interspecific interactions inhibit the growth of the native species, whereas under PE treatment, interspecific interactions promote the growth of the invasive species. These findings demonstrate that microplastic pollution can promote plant invasion, but the underlying mechanisms differ depending on microplastic type, providing valuable insights for the management and prevention of biological invasions under increasing microplastic pollution.

Key message : Evergreen coniferous forests and deciduous broadleaf forests in the warm-temperate zone of northern China exhibit fundamentally distinct environmental and spatial correlates of understory herb-layer diversity across α- and β-diversity dimensions. Canopy cover correlates with α-diversity in coniferous forests, while soil organic matter correlates with richness in deciduous broadleaf forests. For β-diversity, compositional turnover correlates primarily with soil pH in coniferous forests but with available potassium in deciduous broadleaf forests, with geographic distance (dispersal limitation) contributing substantially in both. Context: Understory herb layers harbor over 80% of vascular plant diversity in temperate forests and serve as early indicators of ecosystem dynamics. While evergreen coniferous forests (ECF) and deciduous broadleaf forests (DBF) differ fundamentally in microenvironmental conditions (transmitted irradiance, litter dynamics, and soil properties), few studies have systematically compared how these contrasting systems shape herb-layer diversity within homogeneous climatic regions. Aims: This study aimed to quantify whether and how the environmental and spatial correlates of α- and β-diversity in understory herb-layer communities differ between warm-temperate ECF and DBF from China, and to identify forest-type-specific management implications for biodiversity conservation. Methods: Using vegetation surveys, soil sampling, and advanced modeling (GAMM and GDM) across 69 forest plots on Mount Lao, China (36°05′–36°19′ N, 120°24′–120°42′ E), we assessed how herbaceous community assembly differs between the two forest types across multiple diversity dimensions. Results: The two forest types harbored distinct compositions (15 species exclusive to ECF, 23 to DBF). In ECF, species richness showed a significant unimodal relationship with canopy cover (optimal at 0.6–0.7), whereas DBF richness declined with increasing soil organic matter. Overstory diversity was positively correlated with herbaceous richness in both systems. For β-diversity, soil pH was the strongest predictor of compositional turnover in ECF, while available potassium was the strongest predictor in DBF. Both forest types displayed strongest distance–decay relationships within 0–15 km, consistent with joint contributions of environmental filtering and dispersal limitation. Conclusion: Divergent canopy–soil interactions suggest that differentiated management approaches may be beneficial: in ECF, maintaining canopy cover within the observed optimal range (0.6–0.7) may support higher richness, whereas in DBF, management could emphasize nitrogen mitigation and soil carbon regulation through mixed-species plantations, which may help maintain species evenness. As these inferences derive from correlative analyses at a single local scale, they should be treated as hypotheses to be tested rather than general prescriptions.