Spatiotemporal response of photosynthetic characteristics in Epimedium pubescens to understory environmental factors across three agroforestry systems

Introduction The sustainable utilization of traditional Chinese medicine resources highlights the dual ecological and economic value of cultivating Epimedium pubescens in forest understories. Nevertheless, the spatiotemporal dynamics of its photosynthetic physiology and the primary regulatory factors under varying tree canopy conditions remain insufficiently characterized. Methods This study examined the physiological responses of E. pubescens story by monitoring its photosynthetic traits and key environmental factors across three artificial forest types ( Phellodendron amurense, Phoebe zhennan, and Camptotheca acuminata ) during the growing season (April–December), with plants assessed at different planting positions (inter-row vs. under-canopy). analyze. Results The results showed that spatiotemporal differences in the understory microenvironment were regulated by canopy characteristics and stand density, with solar radiation being the key factor driving spatial variation. Diurnal dynamics of net photosynthetic rate ( P n ) and stomatal conductance ( g s ) showed significant spatial differences across the three forest stands. At the monthly scale, photosynthetic characteristics varied by tree species: in P. zhennan forests, P n of inter-row plants was significantly higher than that of under-canopy plants throughout the growing season; in P. amurense and C. acuminata forests, significant positional differences in g s occurred in autumn and summer. Variance decomposition and structural equation modeling further revealed that P n was primarily driven by solar radiation at both diurnal (R² = 0.524) and seasonal scales (independent explanatory rate 34.3%), while g s was mainly regulated by vapor pressure deficit at the diurnal scale and by air humidity at the seasonal scale (β = 0.49. Discussion This study provides a physiological and ecological basis for canopy light transmittance regulation and precision cultivation of E. pubescens and similar crops under artificial forests.