###### Abstract  
Successful conservation through monitoring of ecosystems and species, which entails the quantification of disturbances at the ecosystem, species, and population levels, presents significant challenges. Given the pivotal role of this information in formulating effective strategies for tree conservation, we establish an integrated methodological framework that characterizes the overall health state of trees in urban, agricultural, and forest ecosystems, at species and individual levels, by connecting various non-invasive techniques and field metrics. To accomplish this, we collected thermal and phenotypic information from 543 trees representing five prevalent tree species, distributed across urban, agricultural, and forest settings, within a typical Mediterranean environment, and we developed trunk thermal indicators to describe species' responses to various disturbances. We (a) examined thermal pattern variations within and among the tree species, (b) explored the relationships between phenotypic traits and trunk thermal indices, (c) quantified the influence of these indices on leaf area index, and (d) classified trees that exhibit defects and fungal pathogens based on these indices. Results showed clear differentiation of thermal and LAI patterns both among tree species and based on the presence or absence of defects. The trunk thermal indices played a significant role in characterizing tree health and predicting LAI, exhibiting strong relationships with phenotypic traits, thereby demonstrating their potential as universal indicators of tree health. Additionally, the inclusion of cavities and fungal presence in the assessment of tree health provided valuable insights into the impact of structural abnormalities on the overall tree condition. Combining trees' phenotypic traits, vitality indices, and trunk thermal indices allowed the successful classification of defects, cavities, and fungal infestation in 91.4%, 88%, and 88% of trees, respectively. By considering the inter-relationships among thermal indices and phenotypic traits, we can confidently identify and quantify tree health, contributing to the conservation of tree species in diverse ecosystems. infrared thermography; thermal indices; tree disturbances; fungal infestation; urban trees; active 2023  
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[PERSON]. [PERSON], [PERSON]; [PERSON], [PERSON], [PERSON]; [PERSON], [PERSON]. E-mail: ztroumbis@env. a multitude of fundamental attributes as it encompasses (a) the notions of vitality, resilience, and resistance [7], (b) the absence of disease across varying scales [8], and (c) the system's capability to provide ecosystem services [9]. These defining characteristics of ecosystem health determine the system's ability to remain unchanged in the face of external pressures, recover from disturbances, and effectively cope with stressful events [10; 11; 12]. In urban, agricultural, and forest ecosystems, anthropogenic pressures tend to contribute to their degradation, which is further exacerbated by disturbances arising from both biotic and abiotic factors, thereby negatively impacting both the ecosystems and the species within them [13]. Among the affected entities, tree species play a crucial role as essential and integral components of these ecosystems [14; 15]; however, they face a multitude of pressures that threaten their health and long-term survival. In urban ecosystems, a multitude of anthropogenic pressures exert significant influence on woody vegetation, particularly urban trees. These pressures encompass various sources of environmental stressors, including gaseous pollutants and particulate matter [16], increased road traffic density [17], and the presence of pollutants commonly associated with urban areas [18].