Forest dieback has emerged as a critical indicator of ecological imbalance and declining resilience of forest ecosystems, particularly under the influence of multifactorial stressors. This study focuses on the widespread degradation of secondary spruce (Picea abies (L.) H. Karst.) stands in the Carpathian region of Ukraine, where the combination of climatic, biotic, anthropogenic, and hydrological factors creates a complex mosaic of stress responses. The research highlights the necessity of a systemic approach to un derstanding forest vulnerability, integrating physiological, morphological, pathological, and anatomical diagnostics at both tree and ecosystem levels. Field and laboratory analyses revealed that root rot caused by Armillaria mellea and Heterobasidion annosum is among the leading phytopathological threats to spruce stands. A marked decline in the photosyn thetic capacity, shifts in pigment composition, and structural changes in needles—including reduced biomass, altered density, and diminished resin canal development—reflect a systemic physiologica destabilization. These alterations correlate with a disruption in water balance and the accumulation of stressinduced metabolites, which collectively compromise tree function. Quantitative relationships were established between needle morphological traits (length, density), water content, and total needle biomass. These parameters exhibited strong sensitivity to external stressors, suggesting their applicability as early bioindicators of forest health. The results underscore the diagnostic value of morphometric and biochemical characteristics of conifer needles in detecting presymptomatic phases of forest decline and in supporting adaptive monitoring frameworks. More over, the study contextualizes forest dieback within broader ecological processes, including carbon cycle disruption, biodiversity loss, and decreased ecosystem productivity. Integration of bioindicatorbased diagnostics with spatially explicit monitoring tools (e.g., GIS, remote sensing, fieldbased assays) is proposed as a promising direction for forest management under climate change scenarios. The findings support the development of adaptive management strategies that account for local ecological conditions, species specific vulnerability, and landscapelevel feedbacks. This work contributes to the scientific basis for enhancing resilience in forest landscapes through improved monitoring, early diagnosis of ecological instability, and targeted interventions to mitigate forest decline in mountain ecosystems
Mudrak et al. (Fri,) studied this question.