Integrating Thermal Indices and Phenotypic Traits for Assessing Tree Health: A Comprehensive Framework for Conservation and Monitoring of Urban, Agricultural, and Forest Ecosystems

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.

Linking Thermal Indices, Productivity, Phenotypic Traits, and Stressors for Assessing the Health of Centennial Traditional Olive Trees

“…Regarding the core of our methodological procedure, the utilization of IRT emerges as a pivotal choice, as it has consistently demonstrated its potential as a diagnostic tool for illustrating trees' thermal patterns [83,89,123,124], enabling the assessment of their health state [77,82,83,125]. Furthermore, the indices derived from the IRT analysis have demonstrated significant relevance across various tree species, encompassing urban, rural, and forest environments [83]. This alignment with the fundamental concept of a healthy tree, as originally proposed by Catena and Catena (2008) [82], underscores their broader applicability and importance.…”

“…Our decision to calculate not only the interquartile ranges but also the outer percentile ranges stemmed from the need to closely examine specific trunk traits, such as cavities, that are closely tied to tree health. This scrutiny of extreme temperature values was imperative, as they are associated with both external and internal irregularities present on the trunk [46,83]. This methodological approach was based on the premise that a healthy tree exhibits a uniformly distributed trunk temperature, indicating an efficiently functioning thermoregulatory system.…”

“…Among these non-invasive techniques, infrared thermography (IRT), a subset of remote sensing techniques [77][78][79], plays a pivotal role in evaluating tree physiology, facilitating early detection of stress factors [80,81] and precise interventions to ensure tree health [82,83] and productivity [46]. IRT captures temperature variations across different structures of the tree, including the canopy and trunk, providing valuable insights for identifying early signs of physiological stress stemming from factors like water deficiency [84][85][86][87] or diseases [88].…”

Deterioro de ecosistemas y paisajes: Lo último al 2023

“…Se observó también que cuando se combinan los rasgos fenotípicos, índices de vitalidad e índices térmicos del tronco de los árboles hay una producción de caries e infestación fúngica en los árboles, traduciéndose en un impacto de las anomalías estructurales en la condición general del árbol (Zevgolis et al, 2023).…”