Forest Health Research Articles

Ecological partnership: Restoring Pinyon woodlands on the Navajo Nation, USA

Pinyon woodlands in the semi-arid southwestern United States developed in response to environmental factors and historical human interactions, providing sustenance and traditional ecological benefits to Native Nations, such as the Navajo (Diné). Historically, Diné communities practiced land stewardship through seasonal movements and resource management, ensuring ecosystem resilience. However, the constraints imposed by European colonization led to transformative changes in their livelihoods and environments. Encompassing 71,000 km2, pinyon-juniper woodlands comprise 89 % of forested area on the Navajo Nation reservation, providing crucial ecosystem services and cultural resources. Since reservation establishment in 1868, increased tree density has diminished understory plant communities and elevated woodland susceptibility to wildfires, compromising overall forest health. Recognizing the imperative for ecological restoration, a collaborative effort between Diné College and Northern Arizona University (NAU) was established in 2018 to develop a pinyon woodland research site on the Diné College campus in Tsaile, Arizona, on the Navajo Nation reservation. We assessed the effectiveness of restoration thinning treatments in reinstating historical woodland structure, modifying fuels for fire mitigation, and engaging students in ecological practices. Thinning resulted in a 62 % reduction in tree density and a 25 % reduction in basal area, altering the woodland structure to reflect historical conditions more accurately. This alteration mitigated the risk of high-intensity wildfires while preserving the age structure of older trees (oldest dating back to 1435 C.E.). Forest floor fuels were low throughout the study, as thinned wood was removed, and activity fuels were immediately treated with chipping. The active participation of Diné College and NAU students, interns, and faculty throughout the study contributed to a cohesive approach in advancing our goals. The comprehensive training empowered students to contribute meaningfully to fieldwork and data collection, aligning with Diné College's mission to enhance post-secondary student learning and development for the benefit of the Diné. By integrating contemporary and culturally sensitive perspectives, our study sheds light on the effectiveness of restoration thinning treatments, emphasizing the delicate balance between ecological resilience and cultural preservation for the Navajo Nation.

Biodiversity and Soil Properties of Saranda Sal Forest: Implications for Conservation and Management

Aims: This study is significant as it elucidates the relationship between floristic composition and soil nutrient availability of India's Saranda Sal (Shorea robusta Gaertn.) forest. Study Design: Vegetation sampling was done following a grid of 5 km x 5 km, and soil sampling was done in each sampling plot using a Z-pattern. Place and Duration of Study: The study was conducted in Saranda Forest of West Singhbhum district, Jharkhand, Eastern India, during 2021-2022 Methodology: Sampling has been designed as grid methods (5 km X 5 km) following a forest survey of India, and vegetation sampling was done by quadrat method. The soil samples were collected from three depths (i.e., surface: 0–30 cm, sub-surface: 30–60 cm and inner: 60-90 cm from each selected site. ANOVAs were used to compare the chemical properties of soil samples from various forests. Pearson correlation analyses to examine the effects of climatic variables on chemical properties of the soil of selected Sal forest as well as their relation with plant diversity. Results: A comprehensive analysis of 5432 vascular plants from 65 species and 34 families was conducted across the 17 sites. Fabaceae is the most dominant family with 07 species. The study also examined soil chemical parameters and micronutrients in different sites and established their relations with vegetation dynamics. Notably, tree density showed a significant positive correlation with soil pH (r=0.59, p<0.05), but a significant negative correlation with Shannon diversity (H') (r=-0.53, p<0.05). Similarly, there was a significant positive correlation of Organic carbon with copper (r=0.59, p<0.05) and iron (r=0.61, p<0.00); however, there was a significant negative correlation with Available Phosphorus (r=-0.52, p<0.05). Conclusion: Research findings underscore the importance of soil nutrients in promoting forest health and growth. Importantly, they can guide the formulation of practical and effective soil-forest management strategies for S. robusta and its associated forests, directly benefiting the forestry and environmental science community.

Рост и состояние дуба черешчатого в смешанных древостоях полезащитных лесных полос

An analysis of the creation and operation of protective forest plantations at agricultural enterprises of the Central Chernozem Region allows us to assert that positive ameliorative functions are performed by those forest plantations that have good growth, high stability and longevity. Russian forestry scientists have recognized that the main species in the steppe conditions for all types of protective forest plantations is the English oak. The aim of the research has been to assess the current state of the stands in forest shelterbelts planted via different methods with the English oak as the main species. Taxation works and forest pathology research were carried out in 1997–2021 in the forest shelterbelt no. 9, established in the spring of 1989 by 2-year-old seedlings in the land-use territory of the Federal State Unitary Enterprise Experimental Production Farm “Znamya Oktyabrya” of the Talovskiy District of the Voronezh Region. It has been established that the influence of combinations of tree species in forest belts on the growth of the English oak at the age of 32 years is quite significant. As a result of competitive relations for environmental resources by fast-growing and associate species, the number of live oak trees in a continuous row planting option is 35.6...52.1 % less than in intermittent forest belt options, of their number during planting. The remaining sharply oppressed oak trees in the plantation sown in the continuous row planting way are far behind in height and stem diameter (by 0.8...7.6 m and 4.1...12.7 cm, respectively) compared to the oaks growing in the intermittent forest belts sown in a block planting way. The absence of improvement felling in the experimental plantations during their growth and formation has led to a significant number of dead oak wood and non-viable trees of this species. Moreover, the proportion of dead oak wood and non-viable trees in the forest belt sown via continuous row planting exceeds the indicator in the intermittent forest belts by 36.6...40.6 %. The number of viable oak trees in the intermittent belt options is 17.7...27.3 % higher than in the continuous row planting option, and the number of limitedly viable trees is 11.5...18.9 % higher.

Spatiotemporal forest health assessment for ecosystem management of Sariska National Park (India) under regional climatic inconstancies

Spatiotemporal forest health assessment for ecosystem management of Sariska National Park (India) under regional climatic inconstancies

There is a need to better take into account forest soils in the planned soil monitoring law of the European Union

Key messageA Soil Monitoring Law to improve soil health across all land uses has been proposed by the European Commission. As forests soils have different chemical and physical properties as well as biogeochemical dynamics compared to agricultural land, they also face different challenges in maintaining and restoring soil health. Examples are soil acidification, eutrophication by atmospheric deposition, responses to climate change, and loss of biodiversity. Therefore, we propose forest soil specific health descriptors and thresholds based on experience and knowledge from existing long-term monitoring programs.

Treegraph: tree architecture from terrestrial laser scanning point clouds

AbstractAccurate quantification of tree architecture is critical to interpreting the growth, health and functioning of trees and forests. Terrestrial laser scanning (TLS) offers millimetre‐level point cloud data, but current approaches to 3D tree reconstruction from TLS point clouds primarily focus on retrieving total volume at tree scale for aboveground biomass (AGB) estimation. Few methods have been designed specifically to provide tree architectural properties, including branch‐level morphology and topology, rather than AGB; derived topological traits have tended to be a compromise, and of secondary importance to volume. We present Treegraph, a new approach explicitly designed to retrieve the architectural traits of trees at multiple scales, from the whole tree scale down to individual branches and internodes, using TLS data with limited assumptions about tree form. It provides morphological traits such as branch length and diameter, alongside topological traits including parent–daughter connections of branches and internodes, furcation (branching) number and branch order. We compare Treegraph‐derived morphological and topological traits with manual measurements of branches from eight destructively harvested trees, yielding RMSE values of 0.60 m (5.96%) for branch length, 2.99 cm (33.45%) for branch diameter, 0.46 (19.38%) for furcation number and 0.08 m (33.16%) for internode length, respectively. In a broader application to 603 trees from tropical, temperate and urban forests, we demonstrate that the derived morphological and topological traits support testing of structure‐related metabolic scaling theories. Testing branches over 10 cm in diameter across 18 657 branching nodes shows that Treegraph‐derived branch‐level scaling exponents deviate from WBE predictions, exhibiting area‐preserving behaviour while displaying asymmetry in length and diameter of daughter branches. Available as open‐source Python software, Treegraph provides fine‐level branching network information, promoting improved insights into tree structure and function. This data‐driven approach reduces the need for empirical heuristic parameters, which has the potential for advancing large‐scale ecological studies on tree architecture.

Effects of catchment land use on temperate mangrove forests

Human land use changes are threatening the integrity and health of coastal ecosystems worldwide. Intensified land use for anthropogenic purposes increases sedimentation rates, pollutants, and nutrient concentrations into adjacent coastal areas, often with detrimental effects on marine life and ecosystem functioning. However, how these factors interact to influence ecosystem health in mangrove forests is poorly understood. This study investigates the effects of catchment human land use on mangrove forest architecture and sedimentary attributes at a landscape-scale. Thirty sites were selected along a gradient of human land use within a narrow latitudinal range, to minimise the effects of varying climatic conditions. Land use was quantified using spatial analysis tools with existing land use databases (LCDB5). Twenty-six forest architectural and sedimentary variables were collected from each site. The results revealed a significant effect of human land use on ten out of 26 environmental variables.Eutrophication, characterised by changes in redox potential, pH, and sediment nutrient concentrations, was strongly associated with increasing human land use. The δ15N values of sediments and leaves also indicated increased anthropogenic nitrogen input. Furthermore, the study identified a positive correlation between human land use and tree density, indicating that increased nutrient delivery from catchments contributes to enhanced mangrove growth. Propagule and seedling densities were also positively correlated with human land use, suggesting potential recruitment success mechanisms. This research underpins the complex interactions between human land use and mangrove ecosystems, revealing changes in carbon dynamics, potential alterations in ecosystem services, and a need for holistic management approaches that consider the interconnectedness of species and their environment. These findings provide essential insights for regional ecosystem models, coastal management, and restoration strategies to address the impacts of human pressures on temperate mangrove forests, even in estuaries that may be relatively healthy.

Iterative smoothing for change-point regression function estimation

Understanding wildfire spread in Canada is critical to promoting forest health and protecting human life and infrastructure. Quantifying fire spread from noisy images, where change-point boundaries separate regions of fire, is critical to accurately estimating fire spread rates. The challenge lies in denoising the fire images and accurately identifying highly non-linear fire lines without smoothing over boundaries. In this paper, we develop an iterative smoothing algorithm for change-point data that utilizes oversmoothed estimates of the underlying data generating process to inform re-smoothing. We demonstrate its effectiveness on simulated one- and two-dimensional change-point data, and robustness to response outliers. Then, we apply the methodology to fire spread images from laboratory micro-fire experiments and show that the regions fuel, burning and burnt-out are smoothed while boundaries are preserved.

Air pollution in Białowieża forest: Analysis of short-term trends from 2014 to 2021

Air pollution caused by sulphur dioxide (SO2) and nitrogen oxides (NOx) has negative impacts on forest health and can initiate forest dieback. Long-term monitoring and analysis of these pollution are carried out in Białowieża Forest in NE Poland due to the threats from abiotic, biotic and anthropogenic factors. The main objective of our study was to monitor the levels and trends of air pollutant deposition in Białowieża Forest. During a short-term monitoring period over six years (2014–2021), the concentration of SO2 in the air decreased significantly (from 2.03 μg m−3 in December 2015 to 0.20 μg m−3 in July 2016), while the concentration of NO2 in the air showed a non-significant decrease (from 8.24 μg m−3 in December 2015 to 1.61 μg m−3 May 2016). There was no significant linear trend in the wet deposition of S–SO4 anions. Mean monthly S–SO4 deposition varies between 4.54 and 94.14 mg m−2month−1. Wet nitrogen deposition, including oxidized nitrogen (N–NO3) and reduced nitrogen (N–NH4), showed a non-significant increase. Mean monthly precipitation of N–NO3 and N–N H4 ranged from 1.91 to 451.73 mg m−2month−1. Neither did total sulphur deposition nor total nitrogen deposition exceed the mean deposition values for forests in Europe (below 6 ha−1yr−1 and 3–15 ha−1yr−1, respectively). Our results indicate that air pollutants originate from local sources (households), especially from the village of Białowieża, as demonstrated by the level and spatial distribution of air pollutant deposition. This indicates that air pollutants from the village of Białowieża could spread to other parts of Białowieża Forest in the future and may have a negative impact on forest health and can initiate forest dieback. It is therefore important to continue monitoring air pollution to assess the threats to this valuable forest ecosystem.

Critical slowing down of the Amazon forest after increased drought occurrence

Dynamic ecosystems, such as the Amazon forest, are expected to show critical slowing down behavior, or slower recovery from recurrent small perturbations, as they approach an ecological threshold to a different ecosystem state. Drought occurrences are becoming more prevalent across the Amazon, with known negative effects on forest health and functioning, but their actual role in the critical slowing down patterns still remains elusive. In this study, we evaluate the effect of trends in extreme drought occurrences on temporal autocorrelation (TAC) patterns of satellite-derived indices of vegetation activity, an indicator of slowing down, between 2001 and 2019. Differentiating between extreme drought frequency, intensity, and duration, we investigate their respective effects on the slowing down response. Our results indicate that the intensity of extreme droughts is a more important driver of slowing down than their duration, although their impacts vary across the different Amazon regions. In addition, areas with more variable precipitation are already less ecologically stable and need fewer droughts to induce slowing down. We present findings indicating that most of the Amazon region does not show an increasing trend in TAC. However, the predicted increase in extreme drought intensity and frequency could potentially transition significant portions of this ecosystem into a state with altered functionality.

Alien invasive pathogens and pests in the changing environment: Focus on North Europe

On 12–13 September 2023, a panel of forest pathologists and entomologists gathered in Visby, Gotland Island, Baltic Sea, Sweden. The participants, a total of 20, represented all five Nordic Countries, three Baltic States, and Ukraine, and also joined by the local stakeholders representing the Swedish Forestry Agency and Gotland Administration. The purpose was to conduct a scientific workshop focusing on invasive tree pests and diseases emerging in each respective country, as well as to participate in an excursion to damaged woodland sites of Gotland. The Nordic Forest Research (SNS) financially supported the event (https://nordicforestresearch.org/n2023-01/). Keywords: Corinectria / Neonectria cankers; Hymenoscyphus fraxineus; Emerald Ash Borer; Diplodia sapinea; Acute Oak Decline; Polygraphus proximus; emerging birch pests; Bronze Birch Borer; Thekopsora areolata; seedborn conifer fungi

Old Pinus massoniana forests benefit more from recent rapid warming in humid subtropical areas of central-southern China

Trees progress through various growth stages, each marked by specific responses and adaptation strategies to environmental conditions. Despite the importance of age-related growth responses on overall forest health and management policies, limited knowledge exists regarding age-related effects on dendroclimatic relationships in key subtropical tree species. In this study, we employed a dendrochronological method to examine the impact of rapid warming on growth dynamics and climatic sensitivity of young (40–60 years) and old (100–180 years) Pinus massoniana forests across six sites in central-southern China. The normalized log basal area increment of trees in both age groups increased significantly following rapid warming in 1984. Trees in young forests further showed a distinct growth decline during a prolonged severe drought (2004–2013), whereas those in old forests maintained growth increases. Tree growth was more strongly influenced by temperature than by moisture, particularly in old forests. Spring temperatures strongly and positively impacted the growth of old trees but had a weaker effect on young ones. Old forests had a significantly lower resistance to extreme drought but faster recovery compared to young forests. The “divergence problem” was more pronounced in younger forests due to their heightened sensitivity to warming-induced drought and heat stress. With ongoing warming, young forests also may initially experience a growth decline due to their heightened sensitivity to winter drought. Our findings underscore the importance of considering age-dependent changes in forest/tree growth response to warming in subtropical forest management, particularly in the context of achieving “Carbon Peak & Carbon Neutrality” goals in China.

Climate change could negate U.S. forest ecosystem service benefits gained through reductions in nitrogen and sulfur deposition

Climate change and atmospheric deposition of nitrogen (N) and sulfur (S) impact the health and productivity of forests. Here, we explored the potential impacts of these environmental stressors on ecosystem services provided by future forests in the contiguous U.S. We found that all stand-level services benefitted (+ 2.6 to 8.1%) from reductions in N+S deposition, largely attributable to positive responses to reduced S that offset the net negative effects of lower N levels. Sawtimber responded positively (+ 0.5 to 0.6%) to some climate change, but negatively (− 2.4 to − 3.8%) to the most extreme scenarios. Aboveground carbon (C) sequestration and forest diversity were negatively impacted by all modelled changes in climate. Notably, the most extreme climate scenario eliminated gains in all three services achieved through reduced deposition. As individual tree species responded differently to climate change and atmospheric deposition, associated services unique to each species increased or decreased under future scenarios. Our results suggest that climate change should be considered when evaluating the benefits of N and S air pollution policies on the services provided by U.S. forests.

Integration of Airborne Laser Scanning data into forest ecosystem management in Canada: Current status and future directions

Airborne Laser Scanning (ALS) has been the subject of decades of applied research and development in forest management. ALS data are spatially explicit, capable of accurately characterizing vegetation structure and underlying terrain, and can be used to produce value-added products for terrestrial carbon assessments, hydrology, and biodiversity among others. Scientific support for ALS is robust, however its adoption within environmental decision-making frameworks remains inconsistent. Cost continues to be a principal barrier limiting adoption, especially in remote, forested regions, however added challenges such as the need for technical expertise, unfamiliarity of data capabilities and limitations, data management requirements, and processing logistics also contribute. This review examines the current status of the integration of ALS data into forest ecosystem management in a Canadian context. We advocate for continued inter-agency acquisitions leading to integration of ALS into existing natural resource management decision pathways. We gauge the level of uptake thus far, discuss the barriers to operational implementation at provincial scales, and highlight how we believe ALS can support multiple objectives of forest and environmental management in Canada. We speak to potential benefits for supporting inter-agency terrain generation, ecosystem mapping, biodiversity assessments, silvicultural planning, carbon and forest health evaluations, and riparian characterizations. We conclude by providing key considerations for developing capacity using ALS and discuss the technologies future in the context of Canadian forest and environmental management objectives.

Health analysis of mangrove forest based on vitality indicators (case study in Purworejo mangrove forest, Pasir Sakti District, East Lampung Regency)

Vitality indicators are characterized by tree damage and canopy condition. This condition has an impact on the health of mangrove forests, including the Purworejo mangrove forest. The aim of this research is to obtain the value and health status of the Purworejo mangrove forest in Pasir Sakti District, East Lampung Regency, based on vitality indicators. In terms of collecting and analyzing vitality indicator data, the Forest Health Monitoring (FHM) method is used based on tree damage parameters and canopy cover conditions. Sample plot clusters were made into four clusters, or 16 plots, at four points with an area of 0.4 ha per cluster. The research results showed that the tree damage value at the cluster plot level (CLI) was 1.08–1.23. The cluster plot level canopy condition value (VCR) was 2.82–3.32. Thus, the average health value of the Purworejo mangrove forest is 1.88, with a medium status category (1.63-2.31). Mangrove forest management must be improved, especially in maintenance activities, to overcome pest problems that cause damage to mangrove trees.

Assessment of Tree Damage with the Forest Health Monitoring (FHM) Method and the Convolutional Neural Network (CNN) Method

So far, the assessment or measurement of tree damage has only been done using the Forest Health Monitoring (FHM) method. This study aims to determine the types of tree damage using Forest Health Monitoring (FHM) and Convolutional Neural Network (CNN) methods. The research was conducted at the TAHURA WAR Utilization Block and the Computer Science Laboratory at FMIPA Lampung University. Measuring the type of tree damage using the FHM method is carried out on trees that are in the FHM cluster. Identification of tree damage types with the CNN algorithm using the MobileNet architecture. The results showed that there were 13 types of tree damage found, with five types of tree damage that were commonly found (> 60 cases): open wounds (218 cases), cancer (94 cases), Broken / Cracks and stems (87 cases), broken or dead branches (73 cases), and loss of dominant shoots (69 cases). As for the identification results with the CNN method, there were nine out of 13 types of damage that obtained precision, recall, and F1 scores of 100%. Thus, five types of dominant tree damage were found, one of which was open wounds (218 cases), and nine types of tree damage obtained high accuracy values.

Mapping the tree damage index: A case study on the green lane in the urban area of Banda Aceh City

Climate change mitigation efforts implemented by the Government of Banda Aceh by building green lanes with trees. The level of the tree’s ability to absorb carbon is highly correlated with the vitality of the tree itself. The health status of a tree can be known by the tree’s damage level. The aim of the research is to provide information on how much damage to trees and the degree of severity. The research was carried out on green lanes on urban streets in Banda Aceh City as many as 8 lines. The object of research is vegetation with the tree growth phase category, and tree damage index assessment using the forest health monitoring method with indicators of tree damage conditions with parameters of damage location code, damage type code, and damage level code. Based on the results, most of the trees suffered light damage. Of the total number of trees observed, there were 1797 individuals, 252 trees were in good health, 1494 were lightly damaged, 40 trees were medium damaged and 11 trees were heavily damaged. The type of damage experienced was dominated by 46% open wound, 32% cancer, 11% brum (excessive branching) and 11% the rest with other kinds of damage.

To conserve African tropical forests, invest in the protection of its most endangered group of monkeys, red colobus

AbstractForest loss and overhunting are eroding African tropical biodiversity and threatening local human food security, livelihoods, and health. Emblematic of this ecological crisis is Africa's most endangered group of monkeys, the red colobus (genus Piliocolobus). All 17 species, found in forests from Senegal in the west to the Zanzibar archipelago in the east, are threatened with extinction. Red colobus are among the most vulnerable mammals to gun hunting, typically disappearing from heavily hunted forests before most other large‐bodied animals. Despite their conservation status, they are rarely a focus of conservation attention and continue to be understudied. However, red colobus can act as critical barometers of forest health and serve as flagships for catalyzing broader African tropical forest conservation efforts. We offer a plan for conservation of red colobus and their habitats and discuss conservation and policy implications.

Litter Decomposition in Retreating Coastal Forests

AbstractRising sea levels lead to the migration of salt marshes into coastal forests, thereby shifting both ecosystem composition and function. In this study, we investigate leaf litter decomposition, a critical component of forest carbon cycling, across the marsh-forest boundary with a focus on the potential influence of environmental gradients (i.e., temperature, light, moisture, salinity, and oxygen) on decomposition rates. To examine litter decomposition across these potentially competing co-occurring environmental gradients, we deployed litterbags within distinct forest health communities along the marsh-forest continuum and monitored decomposition rates over 6 months. Our results revealed that while the burial depth of litter enhanced decomposition within any individual forest zone by approximately 60% (decay rate = 0.272 ± 0.029 yr−1 (surface), 0.450 ± 0.039 yr−1 (buried)), we observed limited changes in decomposition rates across the marsh-forest boundary with only slightly enhanced decomposition in mid-forest soils that are being newly impacted by saltwater intrusion and shrub encroachment. The absence of linear changes in decomposition rates indicates non-linear interactions between the observed environmental gradients that maintain a consistent net rate of decomposition across the marsh-forest boundary. However, despite similar decomposition rates across the boundary, the accumulated soil litter layer disappears because leaf litter influx decreases from the absence of mature trees. Our finding that environmental gradients counteract expected decomposition trends could inform carbon-climate model projections and may be indicative of decomposition dynamics present in other transitioning ecosystem boundaries.

First report of Cryptostroma corticale causing sooty bark disease in California and first worldwide report of silver maple as a host.

In November 2022 and February 2023, CAL FIRE tree health experts examined four maples (Acer spp.) planted decades earlier in a residential setting in Elk Grove, Sacramento Co., California (USA). Three of the trees were silver maples (Acer saccharinum ) and one was a Norway maple (A. platanoides); both species are exotic to California. The trees were in an irreversible state of decline, with the canopy substantially thinned and browning. Extensive bark cankers elongating longitudinally along the stem were visible on all trees (Fig. S1). Cankers were filled by fungal stromata protruding through the bark and producing masses of elliptical dark brown conidia (Fig. S2), approximately 5.5 x 3.7 um in size, giving the cankers a sooty appearance. The cankered bark could be peeled off easily, revealing dark and discrete lesions in the phloem and xylem. Samples from the three trees were shipped to the U.C. Berkeley Forest Pathology and Mycology Laboratory and to the CDFA PPDC in Sacramento, CA. In the laboratories, small wood chips were taken from the margins of the lesions, surface sterilized by dipping them for 30 seconds in 70% Ethanol, rinsed for 30 seconds in sterile water and plated onto 2.5% Malt Extract Agar amended with 0.3g/L Streptomycin or onto one-half strength acidified potato dextrose agar (APDA). Two morphologically identical cultures were obtained, one (T2) from a silver maple and one (T6) from the Norway maple. Cultures were then grown in liquid 2.5% malt extract broth and, after one week, DNA was extracted using the Qiagen Plant DNeasy DNA extraction kit. The ITS sequences are diagnostic for this fungus (Li et al. 2021) and those of the two cultures (GB OR064033 and OR933565) were 100% homologous to GenBank sequences of Cryptostroma corticale ( e.g. GB OP474010-11). The RPB2 sequence of T2 ( GB OR992132) was 100% homologous to that of C. corticale (GB HG934116.1). The isolate obtained from silver maple was inoculated in four potted silver maples by removing a bark disk 50 mm in diameter with a cork borer in three spots staggered at different heights and sides on the stem, placing a colonized agar plug of C. corticale in contact with the phloem, replacing the bark disk and wrapping with parafilm. Two control trees were mock inoculated using sterile agar plugs. Trees were in 57 L pots, had an average stem caliper of 2.7 cm, an average height of 3.5 m and were kept in a lath house at average high temperatures of 18-24 degrees C. After ten weeks, average lesion length was 15.4 cm (SE= 4.6) and 4.3 cm (SE=2.3) in the fungus-inoculated and control trees, respectively. An ANOVA test, nesting lesions sizes within tree, determined lesions lengths were different between inoculated and mock trees (P= 0.04). The fungus was reisolated from all points in all inoculated trees but never from control trees. C. corticale was first described in the UK from sycamore maple (Acer pseudoplatanus) (Gregory et al. 1949) and is an emerging problem in Europe (Muller et al. 2023). In North America, it has been reported from A. negundo, A. campestre, A. macrophyllum and Cornus nuttallii (Worral 2020), and it appears to be present in the Pacific Northwest (Brooks et al. 2023, Goree 1969). Norway maple is included in the European Plant Protection Organization list of hosts for C. corticale (EPPO 2023), however our finding of C. corticale on silver maple is a first report of this host worldwide and of this pathogen in California. This report is noteworthy, given that C. corticale is also a human pathogen infecting the respiratory system (Braun et al. 2021).