Imago Mundi

Abstract Purpose of the Review In this review, we synthesize knowledge generated over many decades on the main defence responses of Eucalyptus to fungal leaf pathogens with the aim of identifying targets for breeding disease tolerant trees. We highlight physiological and molecular traits associated with host defence in relation to pathogen life-style. Overall, the purpose of this review is to identify resistance mechanisms that offer improved resilience of Eucalyptus plantations in the face of increasing threats by foliar fungal pathogens. The broad aim is to promote sustainable forestry through appropriate selection of resistance traits in trees that are widely planted for commercial timber production. Recent findings Eucalyptus is among the most important tree genera planted for commercial timber production worldwide. Numerous foliar pathogens have been reported on these trees in the last 30 years with numbers of recent reports increasing exponentially. The majority of these diseases affect the leaves and shoots of the trees. Knowledge on resistance traits in Eucalyptus to fungal foliar pathogens is limited. This is in part due to the high intra- and inter-species variation in molecular and physiological responses of the host and variation in responses to different pathogens, especially those with different trophic modes. A well-founded understanding of such host responses will provide valuable knowledge required to maintain healthy, sustainable Eucalyptus plantations, especially in the face of changing environmental conditions, where new diseases are caused by fungi previously not considered relevant. Summary Foliar diseases are among the most important challenges for Eucalyptus plantations globally. The effects of climate change and new or more serious outbreaks present an important threat to the sustainability of Eucalyptus plantations worldwide. Due to restrictions on the use of chemicals, more feasible solutions for disease management lie in selecting planting material with resistance traits. To achieve that goal, it is essential to understand the most important physiological and molecular responses of Eucalyptus to infection by pathogens that infect their foliar tissues. In this review we summarise the available knowledge of the main physiological defence barriers and genetic traits that play key roles in the broad defence against foliar fungal pathogens. Furthermore, we consider defence pathways that are specifically related to the lifestyle and trophic mode of the pathogens. In order to ensure the future sustainability of Eucalyptus plantations, it will be necessary to understand how disease resistance is affected by climate change, as well as the adaptability of the hosts and pathogens to newly emerging environmental conditions.

This review synthesizes recent advancements and identifies knowledge gaps in the tree growth phenology of both belowground and aboveground organs in extra-tropical forest ecosystems. Phenology, the study of periodic plant life cycle events, is crucial for understanding tree fitness, competition for resources, and the impacts of climate change on ecosystems. By examining the phenological processes of various tree organs, the review aims to provide a comprehensive understanding of how these processes are interconnected and how they influence overall tree growth and ecosystem dynamics. The review aims to provide a comprehensive overview of current knowledge, highlight recent technological advancements, and identify critical areas where further research is needed. The review highlights significant progress in monitoring leaf and canopy phenology, thanks to advancements in remote sensing and automated observation systems. These technologies have enhanced our ability to track seasonal changes in leaf development and canopy dynamics more accurately and over larger areas. There has also been a substantial increase in research on wood formation in stems, expanding beyond northern hemisphere conifers to include a broader range of functional groups. However, despite these efforts, identifying the precise drivers of wood formation remains challenging, necessitating further integration of molecular and eco-physiological insights. A critical area of focus is root phenology, encompassing both primary and secondary growth. Despite the fundamental role of roots in tree physiology and ecosystem dynamics, our understanding of root phenology remains limited, primarily due to the inherent difficulties in monitoring root growth. The review emphasizes the need for more detailed studies on root growth processes and the development of new methodologies and technologies to improve root phenology assessments. The review highlights the importance of incorporating eco-physiological insights into phenological assessments. Leaf and canopy phenology would benefit from more studies focusing on autumnal events. Indeed, compared to the onset of the growing season, much less is known about its end, despite its critical importance for understanding processes such as carbon uptake and nutrient cycle. Advancing knowledge of wood growth phenology will require greater focus on angiosperms, as research on xylogenesis has historically been centered on gymnosperms. This will likely necessitate the development of new, tailored methodologies to address the characteristics of angiosperm wood formation. Similarly, further exploration of phloem phenology is essential to better understand the links between phenological processes across different organs. Finally, compared to other organs, root growth remains less well understood, underscoring the need for deepening the investigation on root phenology in the coming years.

Quantifying the store and flux of carbon across space and time from trees to forest stands, and ultimately at a global scale, has become paramount for a broad range of applications, including individual tree based allometry, landscape scale forest carbon accounting as well as derivation of globally required climate change related variables. Despite this significant information need, the measurement of forest carbon using field methods remains laborious, expensive and logistically complex. Laser scanning technologies mounted on terrestrial, unmanned aerial vehicles or drones, aircraft or satellites have revolutionised the estimation of forest carbon at a variety of spatial and temporal scales with each providing detailed and often unique information about the distribution of biomass and carbon within a stand. In this review, we examined the use of laser scanning technologies for this purpose.  To do so we focus on the recently published (within 10 years) peer reviewed literature and consider studies across four information needs, individual tree, stand, regional / national, and global scales. We consider the type of laser scanning data that is typically acquired, data processing pipelines and the products that are produced. After reviewing these studies, we conclude with a discussion of remaining issues associated with the mapping of forest carbon using laser scanning technologies. We also highlight a number of future research directions to further expand the use of this technology for forest carbon mapping globally.  

Abstract Purpose of the Review This literature review focused on studies on alternative powertrains and fuels of non-road mobile machinery (NRMM) during the last 15 years and investigated their future potential and expectations. The goal was to evaluate different alternative powertrains based on previous research and highlight the possibilities and challenges of each technology. Additionally, the aim was to conduct a comprehensive overview about the technology development phase of alternative powertrains. Recent Findings This review covered a total of 115 studies consisting of hybrid, full-electric, biofuels, biogas, and hydrogen solutions. The results highlighted that hybrid and full-electric technologies have the greatest potential to replace conventional diesel engines in the future. The main challenges identified were battery reliability and high technology costs. Regarding biofuel, biogas, and hydrogen, the benefits were mainly lower emissions while the challenges were high costs and low production. Full-electric and hydrogen powertrains were found to reach zero local emissions during operations, while compared to diesel, repair and maintenance caused less emissions of 36–46% during the life cycle with full-electric and hydrogen solutions. With hybrid, biofuels, and biogas powertrains, the emission reduction potential ranged from 37 to 81% during operations and 36–66% during the entire life cycle. The highest Technology Readiness Levels (TRLs) were identified for hybrid and full-electric technologies in industrial machinery (6.9–7.4). The lowest measurable TRL (2.5) was with biogas powered construction machinery. The TRLs of biogas and hydrogen of forest machinery were excluded from this review due to the lack of research. Summary Alternative powertrains can eventually replace diesel engines, if the challenges with implementation, production, and reliability are solved. Furthermore, the benefits of electric and renewable technologies/fuels are unambiguous from the emission reduction and energy efficiency perspectives. Consequently, we recommend that future research focus especially on the implementation of alternative technologies as well as the improvement of the manufacturing infrastructure.

This review aims to address the specific challenges of forest decline in Mediterranean Fagaceae ecosystems driven by the alien invasive Phytophthora cinnamomi and global changes. In a scenario of climate change and anthropic pressure, this review seeks to offer a comprehensive overview of the current state of P.cinnamomi invasion, focusing on its biology, ecology and epidemiology in different Mediterranean forest ecosystems, and providing an update on diagnosis, impact and current management measures. Recent studies have significantly advanced our understanding of the decline of Mediterranean Fagaceae forests driven by Phytophthora spp. The introduction of the plant holobiont concept and microbial invasion biology and ecology has reshaped the study of plant–microbe interactions. This perspective, which considers the tree as an ecosystem composed of the tree itself together with its associated microbiome has been pivotal in developing holistic management strategies to mitigate pathogen impacts. The network of interactions between components of the microbial community of healthy and diseased trees, has been the object of several recent studies that highlighted the complex dynamics of host–pathogen interaction and offered the option for biotechnological applications including the use of helper microorganisms and antagonists. The collaboration among research institutions from Italy, Spain and Portugal has resulted in a detailed review that emphasizes the importance of tailored management protocols for different ecosystems. Engaging stakeholders and citizens in integrated pest management (IPM) strategies has proven crucial for effective forest management. The findings underscore the need for continuous monitoring, innovative treatment methods, and public awareness to mitigate the impacts of Alien Invasive Forest Phytophthoras (AIFPs) and ensure the sustainability of Mediterranean Fagaceae forests.

Abstract Purpose of Review The behaviour of wildland fires, namely their free spreading nature, destructive energy fluxes and hazardous environment, make it a phenomenon difficult to study. Field experimental studies and occasional wildfire observations underpin our understanding of fire behaviour. We aim to present a global synthesis of field-based studies in forest and shrublands fuel types published since 2003 with a focus on the most commonly measured fire behaviour attributes, namely rate of fire spread, ignition and spread sustainability, flame characteristics, fuel consumption and spotting behaviour. Recent Findings We present a synthesis of measured fire behaviour data collected in field experiments and wildfire environments encompassing the last two decades. We discuss the effect of a lack of standardised experimental methodologies in field studies, which has inhibited our quantitative understanding of the physical drivers of fire behaviour. The application of new fire environment and behaviour measuring sensors and methods offer opportunities for more comprehensive descriptions of fire spread characteristics, particularly when applied to wildfire events, to better capture scale dependent phenomena that do not occur at smaller experimental scales. Summary Fire behaviour data collected in field experiments and wildfires form the foundation of our quantitative understanding of fire dynamics. These data are used in the development and evaluation of predictive models with operational and scientific applications. We provide a broad synthesis of existing field-based studies in forest and shrubland ecosystems and discuss their limitations and needs for future research.

This review covers electrical phenomena originating from the physical properties of wood, relevant to tree biology and timber industry applications. Membrane-associated cellular phenomena like action potentials are excluded. Trees exhibit diverse bioelectric processes of physical origin. The electrical properties of wood hold promise for advancing timber processing, and developing smart materials, while enhancing our understanding of tree-environment interactions. Streaming and piezoelectric potentials have long histories but are now reinterpreted based on our better understanding of plants. Streaming potentials from sap flow, discounted in the 2000s, have been reinstated through recent publications addressing past inconsistencies with current data on xylem structure. Electro-osmotic flow is gaining new applications in timber drying. Wood, previously considered weakly piezoelectric, shows much stronger activity after fungal degradation, spurring interest in practical applications and the underlying mechanism – now better understood through new findings on the structure, deposition and deformation of wood cellulose. Internal variation in the electric (conductive and dielectric) properties of green logs facilitates innovative timber quality mapping methods. Emerging research on perturbation of the atmospheric and soil electric fields by trees offers insights into inter-organism interactions. This review encompasses electrical measurement methods; electrokinetic phenomena, including streaming potentials and electro-osmotic timber drying; electric heating; mapping and technologies based on dielectric properties; wood-based electronics; electromechanical phenomena, including the piezoelectric effect and triboelectrification; atmospheric electricity around trees; and electrotaxis. Future research should explore electro-osmosis in wood and its applications. Electric potentials in green wood and living trees, generated through ion-transport mechanisms, need further exploration to elucidate charge separation processes.

Abstract Purpose of Review The perception of forests has evolved from mere timber sources to multifunctional ecosystems that support biodiversity and provide essential ecosystem services. Nevertheless, insecticides remain crucial in many forestry systems facing intensifying insect outbreaks and invasions. This review examines recent literature on insecticide use in forestry worldwide, aiming to identify major use patterns, environmental impacts, and emerging alternatives to foster sustainable pest management. Recent Findings The need for alternatives to chemical control is globally recognized, driven by environmental impacts and increasingly strict regulatory frameworks. Recent studies using next-generation sequencing suggest that insecticides can have complex, indirect effects on animal community structures, underscoring the importance of in situ community-wide assessments. Bioinsecticides have been extensively tested, but their effectiveness is strongly dependent on environmental conditions. Advances in functional genomics, nanomaterials, and application technologies suggest that direct control tactics compatible with conservation goals may become achievable. Summary Four major use patterns were identified: (1) aerial applications against defoliators; (2) tree-level prophylactic applications against endophagous insects; (3) toxic baits against eusocial pests; and (4) seedling protection in nurseries and reforestation sites. Although insecticide use is influenced by management intensity, integrated pest management (IPM) is widely implemented across forestry systems. Insecticides are generally used sparingly but still play a critical role as last-resort suppression tactics against severe outbreaks. This complicates the search for alternatives, as reduced-risk compounds often lack the efficacy needed for this niche. The scope of ecological impact assessments vary, focusing on natural enemies in intensive systems, and increasingly including wider communities in multifunctional forests. There is a pressing need for protocols that assess both economic and ecological trade-offs at the community level to integrate future technologies, such as molecular control and nanoinsecticides, into IPM strategies.

Abstract Purpose of Review This paper provides an overview of integrating artificial intelligence (AI), particularly deep learning (DL), with ground-based LiDAR point clouds for forest monitoring. It identifies trends, highlights advancements, and discusses future directions for AI-supported forest monitoring. Recent Findings Recent studies indicate that DL models significantly outperform traditional machine learning methods in forest inventory tasks using terrestrial LiDAR data. Key advancements have been made in areas such as semantic segmentation, which involves labeling points corresponding to different vegetation structures (e.g., leaves, branches, stems), individual tree segmentation, and species classification. Main challenges include a lack of standardized evaluation metrics, limited code and data sharing, and reproducibility issues. A critical issue is the need for extensive reference data, which hinders the development and evaluation of robust AI models. Solutions such as the creation of large-scale benchmark datasets and the use of synthetic data generation are proposed to address these challenges. Promising AI paradigms like Graph Neural Networks, semi-supervised learning, self-supervised learning, and generative modeling have shown potential but are not yet fully explored in forestry applications. Summary The review underscores the transformative role of AI, particularly DL, in enhancing the accuracy and efficiency of forest monitoring using ground-based 3D point clouds. To advance the field, there is a critical need for comprehensive benchmark datasets, open-access policies for data and code, and the exploration of novel DL architectures and learning paradigms. These steps are essential for improving research reproducibility, facilitating comparative studies, and unlocking new insights into forest management and conservation.

Abstract Purpose of the Review The escalating impacts of human activities and climate change, particularly increased nutrient leaching and deposition, could significantly alter the productivity, structure, and function of tropical vegetation. To better understand how nutrient deposition affects regeneration in tropical ecosystems, we synthesised studies that added N, P, NP, or NPK to the seedlings of tropical tree and shrub species. Recent Findings In the tropics, nutrient limitation leads to multiple resource constraints. Our systematic review and hierarchical meta-analyses aimed to: (1) test the effect of nutrient addition on the growth rate and biomass allocation of seedlings of tropical species; (2) examine seedling responses across climate-defined groups; (3) quantify the effects of experimental methods and wood density on species’ responses to experimental fertilisation. Summary Overall, nutrient addition increased seedling shoot biomass by 26% and growth rates by 14%. Pot and transplantation experiments demonstrated stronger positive effects than in-situ observational studies. Nutrient combinations yielded the highest growth rates (NPK: 27%, and NP: 18%), and N was critical for shoot biomass (N: 38%, and NP: 48%). The responses of shoot biomass indicated co-limitation of N and P, but also high variability in seedling responses to individual nutrients. Temperature and precipitation had indirect regulating effects, while seasonality showed the strongest impact in seasonally dry sites (38% growth rate and 70% shoot biomass). Species showed individual responses to nutrients, influenced by biotic and abiotic interactions. Finally, we suggest tracking additional parameters, like forest successional status, that may intensify nutrient deposition effects on tropical soils due to climate change.

Abstract Purpose of review We are amid a historical momentum encouraging forest restoration, yet the translation of ambitious targets into reality is hindered by poor documentation and understanding of the success and failure of past restoration efforts. This review aims to evaluate the ecological, social, political and economic characteristics of forest restoration across Europe, their development over time and key lessons learned to guide future restoration initiatives. The analysis is based on the synthesis of expert assessments from 18 European countries. Recent findings Early restoration initiatives in central and southern Europe were largely reactive to natural disasters or timber shortages, and while effective in erosion control and timber production, their ecological benefits were often limited due to monoculture plantations and short-rotation systems. Geopolitical crises intensified timber production, with nationalized and centrally managed forests in several countries, but often at the cost of biodiversity. Since the 1990s, a shift toward multifunctionality has emerged driven by the convergence of environmental, social, political and economic events. Summary Forest restoration in Europe has transitioned from disaster reduction and production-driven efforts to a more multifunctional approach that promotes biodiversity. Changes have been driven by a combination of environmental (e.g., catastrophic consequences following natural disasters), political (e.g., wars, forest nationalization and management centralization), legal (e.g., strict and ambitious national and international policies), social (e.g., rural abandonment and changes in societal values) and economic (e.g., new funding mechanisms or market fluctuations) events. Despite the development, conflicting goals, insufficient funding, climate change and short-term thinking persist as key barriers.

Abstract Purpose of Review This review offers a thorough examination of the pine pathogen Diplodia sapinea, tracing its historical significance from its initial impact on South African non-native Pinus plantations to its recent emergence as a major threat to forests, particularly in Europe. It also highlights recent findings regarding its taxonomic position, genetic studies, and shifts from being perceived as a wound-infecting pathogen to an endophyte in healthy Pinus species that causes disease after stress. Recent Findings Recent years have witnessed a dramatic increase in the damage caused by D. sapinea in natural and planted forests. This escalation is apparently strongly linked to climate change. The pathogen’s previously confused taxonomic position has been clearly resolved in the Botryosphaeriaceae, alongside several sibling species. Diplodia sapinea is now well-understood as an endophyte in healthy trees, which has significant implications for studies aimed at understanding its biology. Importantly, robust techniques including those utilizing genome sequences, are now available for rapid identification and population genetic studies of the pathogen and the factors that drive disease outbreaks. Summary Over the past century, D. sapinea has transitioned from a localized problem in South African non-native plantations to a global threat to both natural and planted forests, particularly in Europe. This review underscores the importance of historical context in understanding the evolution of the pathogen’s impact. It also lays the foundation for future research endeavours, leveraging modern technologies to address key questions surrounding its biology and ecology.

To synthesize new information regarding the environmental sensitivity and impact of climate change on leaf-, wood-, phloem- and root phenology of deciduous forests of the temperate (and boreal) zone, comprising overstory and understory, and both woody and herbaceous species. The environmental sensitivity and impact of climate change on spring leaf phenology are relatively well understood, with ongoing efforts focusing on the spatial and temporal variability in both overstory and understory. Autumn leaf phenology and cambial phenology have received increasing attention in recent years. The drivers of senescence progression are well understood (current temperature), while the drivers of the onset of senescence are still uncertain but likely relate to spring temperature, water availability and light conditions. Studies on cambial phenology of angiosperm trees have focused on the variability across populations and years, while studies on phloem remain scarce and synthesis studies are unavailable. For fine root phenology, asynchronicity with leaf phenology and high variability among species have been demonstrated, but large uncertainty remains regarding the drivers of the onset and cessation of their growth. Studies on woody and herbaceous understory highlight the importance of microclimate differences within the stand. Future phenology research should focus on (i) onset of leaf senescence, (ii) fine roots, (iii) the relationships between overstory and understory species not only regarding leaves, but also wood and fine roots, (iv) variability across multiples scales (e.g. individuals, stands), and (v) interannual legacy effects and connections among phenophases of different organs and forest compartments.

A rapidly changing climate is weakening the resilience of forest ecosystems through vitality loss of major native tree species, which reduces the ability of forests to deliver ecosystem services. Established invasive tree species (EITS) may take over the vacant space potentially preventing the regeneration of the preferred native tree species. This paper aims to investigate how expansion of these invasive non-native tree species can be addressed in a context of climate-smart forest management, considering alternatives to costly and often ineffective EITS control measures. We found that forest ecologists increasingly recognize that climate-smart forest management, in particular tree species diversification and close-to-nature forest management, can strengthen the resilience of forests against negative impacts by EITS. In the resulting resilient forest ecosystems, a more closed canopy may deprive EITS of their invasive nature, and EITS may contribute to climate change adaptation. This review proposes new pathways for forest management transcending the apparent incompatibility between the dominance of EITS and the adaptation capacity of forests and forest management to climate change. Adaptive measures to increase the resilience of forests to climate change may prevent the dominance of EITS. Under such conditions, useful functional traits of these tree species may even contribute to maintenance or enhancement of biodiversity, provisioning of ecosystem services and adaptation to climate change.

The invasion of North America by the Asian beetle Agrilus planipennis has caused severe economic and ecological damage to ash (Fraxinus) tree populations. Agrilus planipennis has recently entered eastern Europe and is spreading there. Many other Agrilus species can potentially become invasive pests due to the cryptic nature of their immature stages that can be inconspicuously transported within infested plant material. We review the ecology, economic impacts, and management strategies of Agrilus worldwide and highlight research gaps. Much has been learned in recent decades about the basic biology and control tactics for a few Agrilus species, especially A. planipennis. The genus Agrilus has over 3,341 described species, making it the largest genus in the Animal Kingdom. Most Agrilus are univoltine and have a narrow host range. Chemical, tactile, and visual cues of host plants are used by adult Agrilus to select suitable hosts for consumption by adults and larvae. Most Agrilus larvae develop within the cambial region, constructing galleries that effectively girdle the host plant. Mechanisms of host plant resistance are being explored. Diverse groups of natural enemies attack all life stages of Agrilus species, with some coevolved specialist parasitoids being introduced successfully to suppress A. planipennis in North America. Climate change, leading to warmer and drier conditions, will influence the distribution and population dynamics of many Agrilus species. Many research gaps still exist in the areas of biocontrol, host plant resistance, and sustainable management strategies for this important group of plant pests.