The freeze-thaw cycle of near-surface soils significantly affects energy and water exchanges between the atmosphere and land surface. Passive microwave remote sensing is commonly used to observe the freeze-thaw state. However, existing algorithms face challenges in accurately monitoring near-surface soil freeze/thaw in alpine zones. This article proposes a framework for enhancing freeze/thaw detection capability in alpine zones, focusing on band combination selection and parameterization. The proposed framework was tested in the three river source region (TRSR) of the Qinghai-Tibetan Plateau. Results indicate that the framework effectively monitors the freeze/thaw state, identifying horizontal polarization brightness temperature at 18.7 GHz (TB18.7H) and 23.8 GHz (TB23.8H) as the optimal band combinations for freeze/thaw discrimination in the TRSR. The framework enhances the accuracy of the freeze/thaw discrimination for both 0 and 5-cm soil depths. In particular, the monitoring accuracy for 0-cm soil shows a more significant improvement, with an overall discrimination accuracy of 90.02%, and discrimination accuracies of 93.52% for frozen soil and 84.68% for thawed soil, respectively. Furthermore, the framework outperformed traditional methods in monitoring the freeze-thaw cycle, reducing root mean square errors for the number of freezing days, initial freezing date, and thawing date by 16.75, 6.35, and 12.56 days, respectively. The estimated frozen days correlate well with both the permafrost distribution map and the annual mean ground temperature distribution map. This study offers a practical solution for monitoring the freeze/thaw cycle in alpine zones, providing crucial technical support for studies on regional climate change and land surface processes.

Soil supports life by serving as a living, breathing fabric that connects the atmosphere to the Earth's crust. The study of soil science and pedology, or the study of soil in the natural environment, spans scales, disciplines, and societies worldwide. Soil science continues to grow and evolve as a field given advancements in analytical tools, capabilities, and a growing emphasis on integrating research across disciplines. A pressing need exists to more strongly incorporate the study of soil, and soil scientists, into research networks, initiatives, and collaborations. This review presents three research areas focused on questions of central interest to scientists, students, and government agencies alike: 1) How do the properties of soil influence the selection of habitat and survival by organisms, especially threatened and endangered species struggling in the face of climate change and habitat loss during the Anthropocene? 2) How do we disentangle the heterogeneity of abiotic and biotic processes that transform minerals and release life-supporting nutrients to soil, especially at the nano-to microscale where mineral-water-microbe interactions occur? and 3) How can soil science advance the search for life and habitable environments on Mars and beyond-from distinguishing biosignatures to better utilizing terrestrial analogs on Earth for planetary exploration? This review also highlights the tools, resources, and expertise that soil scientists bring to interdisciplinary teams focused on questions centered belowground, whether the research areas involve conservation organizations, industry, the classroom, or government agencies working to resolve global chal-lenges and sustain a future for all.

The impact of water droplets on soils has recently been found to drive emissions of airborne soil organic particles (ASOP). The chemical composition of ASOP include macromolecules such as polysaccharides, tannins, and lignin (derived from degradation of plants and biological organisms), which determine light absorbing (brown carbon) particle properties. Optical properties of ASOP were inferred from the quantitative analysis of the electron energy-loss spectra acquired over individual particles using transmission electron microscopy. The optical constants of ASOP are compared with those measured for laboratory generated particles composed of Suwanee River Fulvic Acid (SRFA) reference material, which is used as a laboratory surrogate of ASOP. The chemical composition of the particles was analyzed using energy dispersive X-ray spectroscopy, electron energy-loss spectroscopy, and synchrotron-based scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy. ASOP and SRFA exhibit similar carbon composition, with minor differences in other elements present. When ASOP are heated to 350 degrees C their absorption increases as a result of pyrolysis and partial volatilization of semivolatile organic constituents. The retrieved refractive index (RI) at 532 nm of SRFA particles, ASOP, and heated ASOP were 1.22-0.07i, 1.29-0.07i, and 1.90-0.38i, respectively. Retrieved imaginary part of the refractive index of SRFA particles derived from EELS measurements was higher and the real part was lower compared to data from more common optical methods. Therefore, corrections to the EELS data are needed for incorporation into models. These measurements of ASOP optical constants confirm that they have properties characteristic of atmospheric brown carbon and therefore their potential effects on the radiative forcing of climate need to be assessed in atmospheric models.