Yuchen An

Geomorphic setting and seasonal variation shape benthic macroinvertebrate communities, but their effects on community patterns and assembly processes remain unclear. We surveyed 49 sites across seven Sichuan rivers during spring and autumn 2025. Reaches were classified as Mountain, Hilly, or Plain. Principal coordinate analysis (PCoA), random forest models, a neutral community model (NCM), and the modified stochasticity ratio (MST) examined community patterns, predictors, and assembly processes. Diptera had high relative abundances in Mountain and Hilly reaches in spring, whereas the proportion of Ephemeroptera increased across reach types in autumn. Taxa richness and Shannon and Margalef indices were higher in Hilly and Plain reaches. Community composition differed significantly among reach types, with reach type explaining 10.3% and 11.4% of variation in spring and autumn, respectively. For Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness, random forest models ranked dissolved oxygen, channel width, elevation, and ammonia nitrogen highly in spring, and the permanganate index, dissolved oxygen, and flow velocity highly in autumn. NCM fit and Nm were higher in spring and Plain reaches. Mean MST values below 0.5 suggested deterministic dominance, with the highest estimated deterministic contribution in Mountain reaches (80.97%). These findings highlight seasonal differences in benthic responses to environmental gradients and potential stressors and may inform river bioassessment that accounts for geomorphic and seasonal context.

Under the efficient market hypothesis (EMH), part of the literature ignores the characteristics of carbon markets. Based on the fractal market hypothesis (FMH), using the MF-DCCA method, this empirical study complements related research. We studied the non-linear multifractal correlation between carbon price fluctuations and China’s economic policy uncertainty (CNEPU) in Shenzhen, Beijing, Tianjin, and the national carbon market. The results show the following: (1) There is no linear correlation between price volatility and CNEPU in all carbon markets. (2) In the national carbon market, the correlation linkage between price fluctuation and CNEPU has not yet formed. (3) In the three regional carbon markets of Shenzhen, Beijing, and Tianjin, the long-range correlations exist with anti-persistence multifractal characteristics, which means that an increase in CNEPU will reduce price fluctuations. (4) After dividing the time scale into long-term and short-term, we found that it does not change the multifractal characteristics but it does change the fractal intensity. Finally, some suggestions are given to policymakers and carbon finance investors.