Understanding beech (Fagus sylvatica L.) photosynthetic responses to microhabitat water deficit: a site-specific investigation

This study explores the nuanced influence of microclimatic conditions on beech stand acclimatization throughout the vegetational season. Three closely situated localities on a north-oriented slope within the National Park Fruška Gora (Serbia) were selected, each exhibiting minimal elevation differences but distinct microhabitat characteristics shaped by orographic and hydrological properties. The hypothesis posits that subtle habitat differentiations imprint distinctive physiological acclimatization patterns in beech stands. Using statistical tools like Multiple Factor Analyses (MFA), Standardized Major Axis (SMA), and Random Forest Analyses (RFA), the study identifies significant relationships among monitored parameters. The vegetational season, extracted from 15 years of NDVI data, reveals prolonged activity with earlier greening and delayed defoliation. MFA analyses highlight the high dependence of beech acclimatization on spatio-temporal properties, showcasing distinctive transitions between months within subpopulations. Reduced July precipitation significantly impacts photosynthetic intensity, transpiration, stomatal conductance, and water use efficiency. Higher localities, closer to the mountain ridge, exhibit heightened vulnerability to water deficit, evident in intense disturbance of photochemical efficiency. In contrast, the lower locality demonstrates tolerance to reduced rainfall, benefitting from additional soil water supply. The severity of drought stress, along with the intricate interplay of microhabitat environmental factors and plant physiological responses, appears to define the acclimatization strategy of beech plants and influence their recovery potential. These findings underscore the spatial microhabitat impact, particularly orographic properties, on beech acclimation to water deficit, with distinct temporal responses at each locality. Implications extend to modified forest management strategies within the National Park, especially in the context of climate change.