In the realm of global climate regulation, forests have long been celebrated for their role in absorbing carbon dioxide and producing oxygen, acting as vital carbon sinks that mitigate the effects of greenhouse gases. This dynamic balance, maintained by a healthy ecosystem of plants and soils, underpins many climate models and sustainability goals. However, groundbreaking research emerging from the University of Notre Dame Environmental Research Center (UNDERC) reveals a more complex narrative, challenging conventional wisdom about how forest health impacts greenhouse gas fluxes, specifically methane emissions.
Traditionally, upland forests were regarded as robust consumers of methane—a potent greenhouse gas far more effective at trapping heat in the atmosphere than carbon dioxide. Methane consumption was primarily attributed to the microbial communities inhabiting the dry soils above forest floors, which absorb methane rather than release it. Yet, new findings suggest that the presence of heart rot disease, a pervasive fungal infection compromising the structural integrity of hardwood trees, alters this dynamic profoundly. Diseased trees, particularly those harboring heart rot, appear to emit significantly more methane than their healthy counterparts, potentially shifting these ecosystems from methane sinks into unexpected methane sources.
Heart rot is a slow-developing pathology wherein fungi degrade the interior wood of trees, most notably the heartwood—the central, supportive core of the trunk. This decay weakens trees from within, ultimately causing fractures in the bark that serve as “hot spots” for methane release. With disease progression, these fractures become more numerous, facilitating the venting of methane produced inside the tree to the atmosphere. This phenomenon indicates that the respiration and decomposition processes inside diseased trees are intricately linked to methane fluxes, a revelation that challenges earlier assumptions about the primary origin of methane uptake and emission in upland forest ecosystems.
To quantify this effect, researchers at UNDERC employed sonic tomography, a sophisticated non-invasive technique harnessing sound waves to generate detailed internal maps of tree health. Sound travels at variable speeds through different materials, allowing the team to precisely locate and measure the extent of wood rot within the trunk. This enabled a direct correlation to be established between rot severity and methane emission levels. Measurements demonstrated that while carbon dioxide outflows remained relatively consistent irrespective of disease status, methane emissions escalated markedly in trees with severe heart rot infection.
Further unraveling the spatial dynamics of gas emissions within trees, the investigative team perforated the trunks at multiple intervals, conducting in situ gas sampling along the vertical axis. Their results indicated a distinct stratification of gases: carbon dioxide emissions peaked in the sapwood area immediately beneath the bark, while methane dominated the heartwood, the infected core of the tree. This layered understanding of gas origin within trees debunks previous assumptions that methane emissions were exclusively soil-related phenomena, extending the scope of forest methane budgets to include internal tree processes.
Importantly, the research distinguished the roles of the fungal pathogens and other microbial players in this methane emission phenomenon. Although heart-rot fungi colonize and decompose the heartwood, laboratory tests confirmed that these fungi alone do not produce methane. Instead, methanogens—methane-producing archaea—thrive in the altered microenvironment created by fungal decay. Genomic sequencing verified the presence of methanogenic communities within diseased heartwood samples, illustrating a complex symbiotic process whereby fungi facilitate tissue decomposition, enabling methanogens to metabolize carbon compounds and generate methane.
This microbial cooperation underscores the intricacy of decomposition pathways in forest trees and highlights a previously underappreciated biological source of methane emissions. The microenvironment shaped by heart rot, characterized by reduced oxygen levels and increased substrate availability, optimizes conditions for methanogenesis, effectively transforming diseased trees into methane emission hotspots. The prevalence of these hotspots has profound implications for forest-level methane budgets, as an increasing incidence of heart rot disease could amplify methane fluxes from upland forests, potentially offsetting their net greenhouse gas absorption.
Soil gas flux measurements conducted alongside tree assessments provided further clarity by confirming that the surrounding soil remained a minor source of carbon dioxide and a slight sink for methane regardless of the tree’s health status. This evidence reinforced the conclusion that methane emissions detected in diseased trees originated internally rather than from soil-based microbial activity. Consequently, existing ecosystem models that have largely excluded tree-derived methane may need revision to incorporate these internal biological processes for more accurate greenhouse gas accounting.
The study’s timing coincides with a broader quest in forest ecology to elucidate the drivers of methane emissions, a greenhouse gas whose atmospheric concentrations have surged and whose sources remain partly enigmatic. By integrating advanced biophysical techniques, genomic analyses, and comprehensive ecological sampling, this work bridges critical knowledge gaps regarding the interplay between tree health, microbial communities, and forest carbon cycling. It sets a new precedent for comprehending the nuanced balance of greenhouse gas emissions at the intersection of plant pathology and ecosystem science.
Looking ahead, the scientific team aims to expand these findings to ecosystem-scale investigations within the forests surrounding UNDERC. Identifying thresholds at which disease prevalence transforms upland forests from net carbon sinks to net carbon sources stands as a pivotal research frontier. Such insights bear consequential weight for climate policy, carbon accounting frameworks, and forest management strategies aimed at mitigating climate change impacts. The revelations about heart rot’s influence on methane dynamics compel a reassessment of forest contributions to atmospheric greenhouse gases.
Supporting this research effort are funding bodies like the National Science Foundation and NASA’s Earth Science Technology Office, emphasizing the high priority placed on understanding biogenic methane sources. Eduardo Chathuranga Senevirathne, the study’s lead researcher and a graduate student at Notre Dame, alongside Adrian Rocha, associate professor and principal investigator, exemplify interdisciplinary collaboration between microbial ecology, plant physiology, and environmental science. Their work leverages the unique natural setting and technological infrastructure available at UNDERC to pioneer integrative studies of forest health and climate interactions.
The implications of this research are expansive, calling attention to the role of fungal diseases in altering forest greenhouse gas fluxes in ways previously unaccounted for in mitigation models. As heart rot and similar diseases continue to afflict hardwood forests worldwide, their cumulative effect on methane emissions could be substantial, potentially undermining the climate buffering capacity of upland ecosystems. Unraveling these biological feedbacks is essential to refining global carbon budgets and developing effective strategies to preserve the vital environmental functions of forests in an era of rapid environmental change.
In conclusion, the discovery that heart rot disease transforms upland forests from methane sinks into sources challenges established paradigms of forest-climate interactions. With methane’s significant heat-trapping potency and forests’ crucial role in carbon sequestration, understanding the internal microbial dynamics within diseased trees offers a transformative lens on how forest health intersects with greenhouse gas emissions. This emerging frontier stands to reshape ecological models and climate forecasts, underscoring the urgency of integrating disease ecology into broader environmental science narratives.
Subject of Research: Forest health, heart rot disease, and their impact on carbon-based greenhouse gas fluxes
Article Title: Forest health, heart rot disease, and their impact on the source of carbon-based greenhouse gas fluxes
News Publication Date: 25-Feb-2026
Web References:
– University of Notre Dame Environmental Research Center (UNDERC): https://underc.nd.edu/
– University of Notre Dame Department of Biological Sciences: https://biology.nd.edu/
– New Phytologist article DOI: http://dx.doi.org/10.1111/nph.71005
Image Credits: Photo by Angelic Rose Hubert/Notre Dame Research
Keywords
Methane emissions, Carbon capture, Carbon sinks, Carbon sequestration, Methane
