Objective Subtropical Phyllostachys edulis forests play a critical role in carbon sequestration and hydrological processes. However, the environmental controls and nonlinear response mechanisms of energy flux partitioning in P. edulis forest ecosystems remain poorly quantified, particularly in the humid regions of southwestern China. This study aims to clarify the dynamic characteristics of energy fluxes and their driving mechanisms in this typical P. edulis forest ecosystem.

Methods Using eddy covariance observations and synchronous meteorological data collected in 2023 at the Jinyun Mountain forest ecosystem research station in Chongqing, China, this study analyzed the temporal dynamics of energy fluxes, including net radiation (R_n), sensible heat flux (H), latent heat flux (L_E), and soil heat flux (G). Linear regression, boosted regression trees (BRT), and nonlinear curve fitting were applied to quantify the relative contributions and interaction effects of environmental and biological factors.

Results 1) The P. edulis forest ecosystem in 2023 had an annual mean Bowen ratio of 0.89, with lower values during the growing season and higher values during the non-growing season. 2) Energy fluxes generally exhibited unimodal diurnal patterns, with peak intensities following the order: summer > spring > autumn > winter. G exhibited a morning phase lag behind R_n, with its peak occurring later than that of R_n. However, in the afternoon, the phase of G advanced relative to R_n. During daytime, H exceeded LE, while LE maintained relatively higher contributions at night. 3) Climatic factors predominated over vegetation-related parameters in regulating surface energy fluxes. Multivariate analysis identified R_n as the predominant driver for both 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.

Conclusions The P. edulis forest at Jinyun Mountain shows clear seasonal and diurnal variations in energy fluxes, with L_E dominating during the growing season and H dominating during the non-growing season. R_n is the main driver of energy flux changes, and T_a exhibits nonlinear regulatory effects. Compared with vegetation physiological factors, climatic factors have a stronger influence on energy fluxes.