Energy fluxes of Phyllostachys edulis forest in Jinyun Mountain and its environmental driving mechanism

Background Subtropical Phyllostachys edulis forest ecosystems constitute a vital part of the regional carbon sink and hydrological cycle. Accurate quantification of their sensible heat flux (H) and latent heat flux (L_E) in response to environmental factors provides crucial data support for optimizing bamboo forest parameters within regional surface process models. Methods Utilizing eddy covariance (EC) and synchronous environmental data collected throughout 2023, this paper investigated the energy flux dynamics of the Phyllostachys edulis forest in Jinyun Mountain, Chongqing, and quantified the responses of H and L_E to multiple drivers using linear regression, Boosted Regression Trees (BRT) and nonlinear curve fitting. Results (1)The Phyllostachys edulis forest ecosystem in 2023 had an annual mean Bowen ratio of 0.89, showing characteristically lower values during the growing season and higher values in the non-growing season. (2)Energy fluxes generally exhibited unimodal diurnal patterns. The peak intensities followed the order of summer > spring > autumn > winter. The morning transition of soil heat flux (G) from negative to positive and its peak lagged behind those of net radiation (R_n), while its afternoon phase shift was earlier. (3) Climatic factors predominated over vegetation parameters in regulating the surface energy fluxes. Multivariate analysis identified Rn as the predominant driver for H and L_E. Relative humidity (R_H) significantly suppressed H, while vapor pressure deficit (V_PD) exerted a strong positive effect on L_E. (4)Air temperature (T_a) showed a weak direct relationship with H but demonstrated nonlinear positive correlations with wind speed (W_S), L_E, and V_PD. Conclusion The Phyllostachys edulis forest at Jinyun Mountain is characterized by high-intensity fluxes, diurnal asynchronous allocation, and anomalous phase shifts in G. While L_E dominates the annual energy budget, a special "daytime H, nighttime L_E" pattern emerges: H intensity normally exceeds L_E during daylight hours (8:00-17:00), whereas L_E dominance is maintained through persistent contributions during nocturnal and transitional periods. Mechanistically, climatic factors were the primary drivers of these energy fluxes. H was primarily driven by the strong positive forcing of R_n and suppressed by R_H, while T_a exerted a nonlinear influence through its interaction with W_S. L_E was co-dominated by R_n and V_PD; Ta enhanced L_E both directly through a nonlinear relationship and indirectly by increasing V_PD. In contrast, physiological regulation by vegetation is relatively limited in this humid subtropical environment.