arXiv subjects

Alexis Maineult

Publications and source records attributed to Alexis Maineult.

7 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↗

arXiv2026

On the evolution of the concept of probability as a mirror of the evolution of reason

Over the centuries, probability theory has grown from the calculus of games of chance into a central framework for reasoning under uncertainty. This article interprets that evolution not merely as a mathematical history, but as a transformation of rationality itself. From Pascal and Fermat's combinatorial symmetry to the inductive logic of Bayes and Laplace, from Poisson's statistics of events to Kolmogorov's axiomatic formalization, probability progressively incorporated uncertainty, time, and coherence into scientific judgment. This trajectory reaches a mature epistemological form in modern Bayesian inference, especially in Tarantola's view of probability as a logic of information, where prior knowledge and data are combined coherently. Yet this framework also exposes a limit: probability quantifies uncertainty about well-defined propositions, but does not by itself formalize the vagueness of the concepts used to describe them. The article therefore examines how rationality extends beyond probability. Fuzzy logic is presented as a rigorous language for graded meaning and qualitative judgment, while deep learning is analyzed as a distinct, powerful mode of prediction based on geometric interpolation and optimization rather than explicit inference. By situating probability, fuzzy logic, and deep learning in a common historical and epistemological perspective, the article clarifies their roles and limits. It argues that contemporary scientific rationality cannot be reduced to data-driven performance alone, but requires the explicit articulation of uncertainty, vagueness, and inference.

cs.AI↗

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↗

arXiv2024

On the effect of the luni-solar gravitational attraction on trees

In this paper, we revisit old electrical measurements conducted on a poplar tree in 2003 (Gibert et al. 2006), which showed the presence of a diurnal electrical signal, attributed to an electrokinetic phenomenon correlated with sap flow, even in winter. We reanalyze these data using the singular spectrum analysis method and demonstrate that the electrical signal measured at various locations (roots, trunk, and branches) on the poplar tree can be decomposed to over 80\% into a sum of 7 pseudo-periods, all linked to luni-solar tides. The precision of the extracted periods exceeds that of models. To validate these old measurements, we have reproduced the 2003 protocol since 2018 at the Jardin des Plantes in Paris, on 3 oak trees and 3 hornbeams. The electrical signals today exhibit the same characteristics as those of 2003. Tidal forces could be a driving force of sap flow in trees.

physics.geo-ph↗

arXiv2023

A living forest of Tibetan Juniper trees as a new kind of astronomical and geophysical observatory

The trajectory of Earth about the Sun is perturbed by torques exerted by the Moon and Sun, and also the four giant planets. These provoke variations of insolation at Earth surface, known as kyr-long Milanković cycles. The concept has been extended to the shorter time scales of years to centuries, that are relevant to tree growth. This paper focuses on iSSA of results of the dendro-chronological study of a forest of long-lived Tibetan junipers. From this, we determine a median curve of tree growth rates, that is analyzed by iSSA. We obtain a rich set of (pseudo-) periods, from 3.3 yr up to more than 1000 years, that compare with the specific spectral signature found in the sunspot and length-of-day time series. We discuss in detail the record from a single tree that spans almost completely the 357-2000 AD interval. The 90 yr Gleissberg, 22 yr and 30 yr components are quite prominent. The Oort, Wolf, Spörer, Maunder and Dalton climate extrema all correspond quite precisely to extrema of the Gleissberg cycle. The well-known Medieval Climate Optimum, Little Ice Age and Modern Climate Optimum all seem to be mainly forced by variations in the envelope of the Gleissberg cycle. The Gleissberg cycle is strongly modulated with a period of 500-600 years. The node near a small gap in the data is very close to the Medieval Climate Optimum. Observations in different parts of Earth are in favor of a global extension of the MCO. In the same way that the Milankovic mathematical theory of climate allows one to relate climate change and length of day, through changes in inclination of Earth's rotation axis and solar insolation, it is reasonable to propose that the set of pseudo-periods that are evidenced in the Tibetan tree ring growth rates simply corresponds to short period Milanković cycles. The Dulan forest could be considered as a good candidate for a continuous, global geophysical observatory.

physics.geo-ph↗

arXiv2020

Modeling Streaming Potential in Porous and Fractured Media, Description and Benefits of the Effective Excess Charge Density Approach

Self-potential signals can be generated by different sources and can be decomposed in various contributions. Streming potential is the contribution due to the water flux in the subsurface and is of particular interest in hydrogeophysics and reservoir characterization. Being able to estimate water fluxes in porous and fractured media using streaming potential data relies on our understanding of the electrokinetic coupling at the mineral-solution interface and our capacity to understand, model, and upscale this phenomenon. Two main approaches have been proposed to predict streaming potential generation in geological media. One of these approaches is based on determining the excess charge which is effectively dragged in the medium by water flow. In this chapter, we describe how to model the streaming potential by considering this effective excess charge density, how it can be defined, calculated and upscaled. We provide a short overview of the theoretical basis of this approach and we describe different applications to both water saturated and partially saturated soils and fractured media.

physics.geo-ph↗

arXiv2017

Variations of petrophysical properties and spectral induced polarization in response to drainage and imbibition: a study on a correlated random tube network

We implement a procedure to simulate the drainage and imbibition in random, two-dimensional, square networks. We compute the resistivity index, the relative permeability, and the characteristic lengths of a correlated network at various saturation states, under the assumption that the surface conductivity can be neglected. These parameters exhibit a hysteretic behaviour. Then, we calculate the Spectral Induced Polarization (SIP) response of the medium, under the assumption that the electrical impedance of each tube follows a local Warburg conductivity model, with identical DC conductivity and chargeability for all the tubes. We evidence that the shape of the SIP spectra depends on the saturation state. The analysis of the evolution of the macroscopic Cole-Cole parameters of the spectra in function of the saturation also behaves hysteretically, except for the Cole-Cole exponent. We also observe a power-law relationship between the macroscopic DC conductivity and time constant and the relative permeability. We also show that the frequency peak of the phase spectra is directly related to the characteristic length and to the relative permeability, underlining the potential interest of SIP measurements for the estimation of the permeability of unsaturated media.

physics.geo-ph↗