The short- and medium-term effects of agricultural soil compaction are well documented, but its long-term impacts and the role of biopores in subsoil recovery remain poorly understood. This study evaluated legacy effects of subsoil compaction on soil hydrophysical properties and root density and assessed the contribution of earthworm biopores to soil recovery. The compaction experiment was established in 1995 on a silt loam Haplic Luvisol by applying six passes of a wheel loader with a maximum wheel load of 5 Mg. Soil measurements were conducted immediately after compaction (1995) and repeated in 2019 and 2023. Measurements in 1995 included soil penetration resistance (PR), bulk density (BD), air-filled porosity (ɛₐ), and relative gas diffusivity (Ds/D0). Winter wheat root density was assessed in 2019. In 2023, PR, BD, ɛₐ, Ds/D0, saturated hydraulic conductivity (Ks), earthworm abundance, and subsoil structural quality (Ssq) were measured. Intact soil cores (30–35 cm) collected in 2023 were grouped according to the presence or absence of visible earthworm biopores. Compaction effects persisted after 28 years. Compared with the control, compacted soil had higher BD (+7.4%), PR (+78% at 20–40 cm), Ssq (+133%), and lower ɛₐ (−31.7%) and Ds/D0 (−33.1%). Root density, Ks, and earthworm abundance were statistically identical between treatments. These hydrophysical differences persisted strongly in samples without biopores, but largely disappeared in biopore-containing samples. Comparison with 1995 data indicated partial recovery of aeration and gas transport, especially in biopore-rich samples. These results show that subsoil compaction can persist for decades, but recovery of pore connectivity is strongly mediated by earthworm biopores.
Context. Hot subdwarf B (sdB) and O (sdO) type stars are evolved helium-burning objects that lost their hydrogen envelope before the helium flash when their progenitors were close to the tip of the red giant branch (RGB). They populate the extreme horizontal branch (EHB) in the Hertzsprung-Russell diagram (HRD). The mass distribution of canonical hot subdwarfs is expected to peak at the core mass required for helium ignition under degenerate conditions in the 0.45-0.5 M⊙ range. However, non-degenerate helium ignition from intermediate-mass progenitors and non-canonical pathways, such as the merger of helium white dwarfs and delayed helium flashes, are also expected to contribute to the hot subdwarf population. Aims. Using high-quality, homogeneous spectra of 335 hot subluminous star candidates from the Arizona-Montréal Spectroscopic Survey, we aim to improve our understanding of the atmospheric and stellar properties of hot subdwarf stars. Our focus is on the mass distribution of the different types of hot subdwarfs and their connections to the various formation scenarios. Methods. We used large grids of model atmospheres to fit the observed spectra and derived their atmospheric parameters: effective temperature (Teff), surface gravity, and helium abundance. The model grids were further utilized to fit the spectral energy distribution of each star and the Gaia parallax was used to compute the stellar parameters radius, luminosity, and mass. Results. Our spectroscopic sample mostly consists of H-rich sdBs and sdOs, but also contains 41 He-rich sdOs. Additionally, the sample includes 11 intermediate-helium stars and 19 horizontal branch objects with Teff > 14 kK. We detected the presence of helium stratification in six sdB stars with Teff around 30 kK, making them good candidates for also showing 3He enrichment in their atmospheres. Our sdB distribution along the EHB shows a gap near 33 kK, visible in both the Kiel (logg-Teff) diagram and HRD, corroborating previous observations and predictions. The mass distributions of H-rich sdBs and sdOs are similar and centered around 0.47 M⊙, consistent with the canonical formation scenario of helium ignition under degenerate conditions. Among the H-rich hot subdwarfs, we found no difference between the mass distributions of close binaries and apparently single stars. The He-sdOs have a significantly wider mass distribution than their H-rich counterparts, with an average mass of about 0.78 M⊙. In the HRD, the He-sdOs lie on the theoretical helium main sequence for masses between 0.6 and 1 M⊙. This strongly favors a merger origin for these He-rich objects. We identified a small number of candidate low-mass (<0.45 M⊙) sdBs located below the EHB that might have originated from more massive progenitors. These low-mass sdBs preferentially show low helium abundances. Finally, we identified more than 80 pulsating stars in our sample and found that they fall into well-defined p- and g-mode instability regions.
Soil ecological research in China has accelerated rapidly over the past two decades, with the historically understudied field of soil animal ecology making particularly notable progress. Through a comprehensive bibliometric analysis and literature review, we synthesize these advancements. We document a remarkable increase from 725 to 1094 in global annual publications, driven by national monitoring networks and a shift from taxonomic inventories to functional ecology. Notably, China’s share of global publications in soil fauna research surged from less than 5
K–Ar dating of fine-grained fractions from metasedimentary rocks is a powerful tool for reconstructing the tectono-thermal evolution across the brittle–ductile transition. In particular, it enables the identification of white mica growth episodes, which, in deformed rocks, can be linked with tectono-metamorphic events. In southern Patagonia, poly-deformed Carboniferous slates are unconformably overlain by Upper Jurassic volcanic rocks, revealing a hiatus of 180–160 My in the geologic record. Therefore, constraining the timescales of pre-Jurassic orogenic construction in southern Patagonia is crucial for establishing correlations with neighboring regions (e.g., northern Patagonia, the Deseado Massif, and the Antarctic Peninsula), although geochronological data remain scarce. To address this issue, we conducted a study combining K–Ar dating in metasedimentary rocks with illite crystallographic characterization obtained through X-ray diffraction analysis. The results presented here allow us to identify two main stages of fold–thrust belt activity: a first stage during the Permian (290–260 Ma), followed by a second one during the Late Triassic (230–215 Ma). These deformation stages are interpreted in the framework of a two-stage, polyphase deformation, corresponding to the late Paleozoic Gondwanide and early Mesozoic Chonide orogenies, respectively, both of which are part of the broader geodynamic framework of the Terra Australis Orogen.
