arXiv subjects

Jean de Bremond d'Ars

Publications and source records attributed to Jean de Bremond d'Ars.

6 recordsLinked to original sources

arXiv2026

On seasonal trunk thermal buffering and its electrical signature in mature trees

Tree trunks contain living tissues whose functioning depends on their thermal environment, yet the processes governing trunk temperature under field conditions remain poorly understood. In particular, it is unclear whether hydraulic transport contributes to buffering trunk temperature against atmospheric variability. We investigated this question by continuously monitoring sapwood temperature, local air temperature, soil temperature at 1~m depth, and spontaneous electrical potential (SP) in six mature trees, comprising three oaks and three hornbeams, over multiple years in a temperate urban forest garden. trunk temperature exhibited a smoother seasonal cycle than air temperature and remained consistently closer to deep-soil temperature, indicating substantial thermal buffering. Seasonal components extracted from the time series revealed a coherent delayed relationship between SP and the trunk-soil temperature difference. Phase-space analysis showed reproducible hysteresis across individuals, and instantaneous phase estimates indicated a lag of approximately 100~days in five of the six trees. A minimal energy-balance model further showed that trunk heat storage alone was insufficient to reproduce the observed seasonal dynamics. Positive effective soil-coupling coefficients were obtained for most individuals, although their magnitude varied markedly among trees. These results are consistent with a contribution of vertically mediated, hydraulically linked heat transfer to seasonal trunk thermal regulation. They further suggest that spontaneous electrical potentials may provide a non-invasive, integrative indicator of slow hydraulic and thermal processes within trees. Such thermo-hydraulic coupling may influence the thermal environment of the cambium and phloem and could therefore contribute to tree responses to seasonal heat and climatic variability.

physics.bio-ph↗

arXiv2025

On a planetary forcing of global seismicity

We have explored the temporal variability of the seismicity at global scale over the last 124 years, as well as its potential drivers. To achieve this, we constructed and analyzed an averaged global seismicity curve for earthquakes of magnitude equal or greater than 6 since 1900. Using Singular Spectrum Analysis, we decomposed this curve and compared the extracted pseudo-cycles with two global geophysical parameters associated with Earth's tides: length-of-day variations and sea-level changes. Our results reveal that these three geophysical phenomena can be be explained with 90% accuracy, as the sum of up to seven periodic components, largely aligned with planetary ephemerides: 1 year, 3.4 years (Quasi-Biennial Oscillation, QBO), $\sim$11 years, $\sim$14 years, $\sim$18.6 years (lunar nodal cycle), $\sim$33 years, and $\sim$60 years. We discuss these results in the framework of Laplace's theory, with a particular focus on the phase relationships between seismicity, length-of-day variations, and sea-level changes to further elucidate the underlying physical mechanisms. Finally,integrating observations from seismogenic regions, we propose a trigger mechanism based on solid Earth-hydrosphere interactions, emphasizing the key role of water-rock interactions in modulating earthquake occurrence.

physics.geo-ph↗

arXiv2024

On the mechanism of thermal self-regulation of trees: a kind of homeothermic observation

What is certain is that surface temperatures around the globe vary considerably, regardless of the time scales or underlying causes. Since 1850, we have observed an average increase in global surface temperature anomalies of 1.2$^{\circ}$ and a median increase of 0.7$^{\circ}$: this overall difference masks significant regional differences. Nearly 60\% of the world's population now lives in urban areas, where vegetation cover has been significantly reduced, despite the paradoxical fact that vegetation plays an important role in regulating the thermal environment (\textit{eg} through the shading provided by tree canopies). Continuous electrical and thermal measurements of trees in a Parisian grove (France) show and quantify that canopies are not the only protectors against heat waves; we must also consider the role of tree trunks. It is clear that these trunks probably regulate themselves, possibly by modulating the uptake of groundwater, whose geothermal stability is well established at a depth of just one meter. This quantitative observation should not be overlooked in the urban planning of our cities.

physics.bio-ph↗

arXiv2016

DIAPHANE: Muon tomography applied to volcanoes, civil engineering, archaelogy

Muography techniques applied to geological structures greatly improved in the past ten years. Recent applications demonstrate the interest of the method not only to perform structural imaging but also to monitor the dynamics of inner movements like magma ascent inside volcanoes or density variations in hydrothermal systems. Muography time-resolution has been studied thanks to dedicated experiments, e.g. in a water tower tank. This paper presents the activities of the DIAPHANE collaboration between particle- and geo-physicists and the most recent results obtained in the field of volcanology, with a focus on the main target, the Soufrière of Guadeloupe active volcano. Special emphasis is given on the monitoring of the dome's inner volumes opacity variations, that could be inferred to the hydrothermal system dynamics (vaporization of inner liquid water in coincidence with the appearance of new fumaroles at the summit). I also breifly present results obtained in the fields of civil engineering (study of urban underground tunnels) and archaelogy (greek tumulus scanning).

physics.geo-ph↗

arXiv2016

Muon dynamic radiography of density changes induced by hydrothermal activity at the La Soufrière of Guadeloupe volcano

Imaging geological structures through cosmic muon radiography is a newly developed technique particularly interesting in volcanology. Here we show that muon radiography may be efficient to detect and characterize mass movements in shallow hydrothermal systems of low-energy active volcanoes like the La Soufrière lava dome. We present an experiment conducted on this volcano during the Summer $2014$ and bring evidence that huge density changes occurred in three domains of the lava dome. Depending on their position and on the medium porosity the volumes of these domains vary from $1 \times 10^6 \; \mathrm{m}^3$ to $7 \times 10^6 \; \mathrm{m}^3$. However, the mass changes remain quite constant, two of them being negative ($Δm \approx -0.6 \times 10^9 \; \mathrm{kg}$) and a third one being positive ($Δm \approx +2 \times 10^9 \; \mathrm{kg}$). We attribute the negative mass changes to the formation of steam in shallow hydrothermal reservoir previously partly filled with liquid water. This coincides with the apparition of new fumaroles on top of the volcano. The positive mass change is synchronized with the negative mass changes indicating that liquid water probably flowed from the two reservoirs invaded by steam toward the third reservoir.

physics.geo-ph↗

arXiv2016

Monitoring temporal opacity fluctuations of large structures with muon tomography : a calibration experiment using a water tower tank

Usage of secondary cosmic muons to image the geological structures density distribution significantly developed during the past ten years. Recent applications demonstrate the method interest to monitor magma ascent and volcanic gas movements inside volcanoes. Muon radiography could be used to monitor density variations in aquifers and the critical zone in the near surface. However, the time resolution achievable by muon radiography monitoring remains poorly studied. It is biased by fluctuation sources exterior to the target, and statistically affected by the limited number of particles detected during the experiment. The present study documents these two issues within a simple and well constrained experimental context: a water tower. We use the data to discuss the influence of atmospheric variability that perturbs the signal, and propose correction formulas to extract the muon flux variations related to the water level changes. Statistical developments establish the feasibility domain of muon radiography monitoring as a function of target thickness (i.e. opacity). Objects with a thickness comprised between $\simeq$ 50 $\pm$ 30m water equivalent correspond to the best time resolution. Thinner objects have a degraded time resolution that strongly depends on the zenith angle, whereas thicker objects (like volcanoes) time resolution does not.

physics.ins-det↗