Canopy reflectance (CR) models describe the transfer and interaction of radiation from the soil background to the canopy layer and play a vital role in the retrieval of biophysical variables. However, few efforts have focused on estimating soil background scattering operators, resulting in uncertainties in CR modelling, especially over sloping terrain. This study developed a canopy reflectance model for simulating CR over sloping terrain, which combines the general spectral vector (GSV) model, the PROSPECT model, and 4SAIL model coupled with topography (GSV-PROSAILT). The canopy reflectance simulated by GSV-PROSAILT was validated against two datasets: discrete anisotropic radiative transfer (DART) simulations and remote sensing observations. A comparison with DART simulations under various conditions revealed that the GSV-PROSAILT model captures terrain-induced CR distortion with high accuracy (red band: coefficient of determination $\lpar {\rm R 2} \rpar = 0.731$(R2)=0.731, root-mean-square error (RMSE) = 0.007; near infrared (NIR) band: $\rm R2 = 0.8319$R2=0.8319, RMSE = 0.0098). The results of remote sensing observation verification revealed that the GSV-PROSAILT model can be successfully used in CR modelling. These validations confirmed the performance of GSV-PROSAILT in soil and canopy reflectance modelling over sloping terrain, indicating that it can provide a potential tool for biophysical variable retrieval over mountainous areas.

We evaluated the morphology, geomorphic settings, and micrometeorological controls of sorted polygons, stripes, lobate patterns, and turf-banked terraces in two summit areas of Daisetsu Mountain, Japan, using orthophoto images and digital surface models generated from unmanned aerial vehicle observations and structure-from-motion techniques and in situ records of air temperature, wind speed/direction and ground temperatures. The sorted polygons on flat terrain are equiform and large (3.5 m in mean length), but on gentle slopes, they are elliptical and small (2.9 m). Sorted stripes and lobate patterns occur on slope steeper than 3.5 degrees-4.5 degrees. The form transition of sorted patterned grounds is considered due to activities of frost heave and thaw settlement, gelifluction, and frost creep, as well as the spatial pattern of soil wetness. In the windward slopes steeper than 3.5 degrees-4.5 degrees, the ground materials move downslope, forming lobate patterns and sorted stripes. On the flat surfaces and leeward slopes, snow accumulation prevents soils from cooling in winter, provides snowmelts to the soils, and thus thickens the seasonal thawing during summer, allowing sorting at greater depths and enlarging the diameters of the frost patterned forms. Snow redistribution and snowmelt infiltration produce locally moist soils, creating favorable environments for plant growth on leeward, that is, eastward sides of microtopography. Soil movements along slopes are dammed on the slope covered with dense vegetation cover where risers of turf-banked terrace are formed. This is the explanation why the turf-banked terraces are typically facing slightly eastward from principal slope direction.

The variable-configuration wheel-track unmanned ground vehicle (VCWT-UGV) has both fast-moving speed on structured roads and strong passing ability on even roads. Steering dynamics analysis is the theoretical basis to ensure that the UGV can still maintain high maneuverability in complex environments. Based on the elastic-plastic deformation characteristics of the soil on the soft road, considering the dynamic changes in resistance and resistance torque caused by soil accumulation on the wheel side during the center-steering process of UGV. Firstly, MBD-EDM co-simulation is conducted to qualitatively analyze the characteristics of soil accumulation on the wheel side during the steering process. Then, based on the terramechanics characteristics of the locomotion mechanism, the kinematic characteristics of the UGV during center-steering are analyzed, and the mathematical model of soil accumulation on the wheel side is established. Furthermore, the dynamic model of the vehicle center-steering with lateral resistance changes is established, and the accuracy of the model is validated through tests. Based on a validated theoretical model, the changes in resistance, resistance torque, and power during the steering process are analyzed. Based on the analysis results, by adjusting the wheel deflection angle, the driving configuration and the motion modes of VCWT-UGV, the steering power efficiency of VCWT-UGV can reach 71.67%. The research results provide a valuable reference for the lateral dynamic modeling of general UGVs on unstructured roads.

Loess landforms in the Loess Plateau are typical landforms in arid and semiarid areas and have a significant impact on the environment and soil erosion. Quantitative analyses on loess landform have been employed from various perspectives. Peak intervisibility can provide the potential topographic information implied in the visual connectivity of peaks, however, its application in loess landform analysis remains unexplored. In this study, the interwoven sightlines among peaks, representing peak intervisibility, were extracted from the digital elevation model and simulated into a peak intervisibility network (PIN). Nine indices were proposed to quantify the PIN. Through a case study in Northern Shaanxi, China, three tasks were conducted, including, landform interpretation, spatial pattern mining, and landform classification. The main findings are as follows: (1) PIN responds to terrain morphology and is beneficial for loess landform interpretation. (2) The spatial patterns of PIN indices are heterogeneous and strongly coupled with the terrain morphologies, showing anisotropy and autocorrelation in spatial variations. (3) Using the light gradient boost machine classifier, the PIN index-based classification reaches a mean accuracy of 86.09%, an overall accuracy of 86% and a kappa coefficient of 0.84. These findings shed light on the applicability of PIN in loess landform analysis. Peak intervisibility not only enriches the theories and methodologies of relation-based digital terrain analysis, but also enhances our comprehension of loess landform genesis, morphology, distribution, and evolution.

High-resolution digital elevation models (DEMs) of permanently shadowed regions (PSRs) at the lunar South Pole are crucial for upcoming exploration missions. Recent advances, such as high-resolution images acquired from ShadowCam, utilize indirect lighting to image PSRs. This provides data for the Shape from Shading (SFS) technique, which can extract subtle topographic details from single-image to reconstruct high-resolution terrain. However, traditional SFS methods are not suitable for complex secondary scattering scenes in PSRs with multiple secondary light sources. To address this issue, a novel secondary scattering SFS (SS-SFS) method is developed for pixel-wise 3D reconstruction of PSR surfaces, which utilizes indirect illuminated imagery and the corresponding low-resolution DEM to generate DEM with high resolution matches the input image. The proposed method effectively extracts and simplifies multiple incident facets associated with each shadowed facet through clustering, while constructing and optimizing the SS-SFS loss function. Experiments were conducted using ShadowCam images of two areas including both PSRs and temporary shadowed areas, to demonstrate the performance of the proposed method. The SS-SFS DEMs effectively capture intricate topographic details, and comparisons with adjusted Lunar Orbiter Laser Altimeter laser points indicate that the SS-SFS DEMs exhibit high overall accuracy. The high-resolution slope map of PSRs was calculated based on the SS-SFS DEMs, and overcome the limitation that surface slope is relatively underestimated from LOLA DEMs. Additionally, the SS-SFS DEMs were comprehensively compared with the traditional SFS DEMs generated using Narrow Angle Camera imagery in a small temporarily shadowed area, revealing strong consistency and further validating the effectiveness of detailed reconstruction. Overall, the proposed SS-SFS method is essential for generating high-resolution DEMs of PSRs, supporting future lunar South Pole exploration missions.

Since hydraulic conductivity significantly influences the compression and deformation characteristics of granular terrains, this study examines the variations in permeability (k20) of granular soils under one-dimensional compression. Two uniformly graded calcareous soil samples were tested: one with grain sizes of 9.50-12.70 mm, and another of 4.75-9.50 mm. Both samples were subjected to one-dimensional compression and constanthead permeability tests. Key soil properties affecting permeability (k20), including absorption (n), specific surface area (Ss), relative density (Dr), void ratio (e), uniformity coefficient (Cu), effective grain size (d10), and mean grain size (d50), were analyzed. The virgin compression line (VCL) of the soil samples was identified within an oedometric stress (sigma VCL) range of 4.00-14.00 MPa, where the rate of change in soil properties affecting permeability was most pronounced. As oedometric stress increased, the instantaneous absorption (ni) of the soil samples increased linearly, with a slope (alpha n) of 0.055-0.061. Similarly, the instantaneous specific surface area (Ss,i) of the soil samples increased linearly, with a slope (alpha s) of 1.229-1.388. In addition, practical equations were developed to predict the instantaneous relative density (Dr,i), instantaneous grain size distribution curve, and instantaneous permeability (k20,i) of granular soils under one-dimensional compression.

Due to the increasing frequency of extreme weather events, drought damage to trees threatens forestry production and forest ecosystems worldwide. Assessing the site conditions under which trees are vulnerable to drought damage provides key information for the establishment of countermeasures to prevent such damage. This study aimed to clarify the differences in drought vulnerability of young planted forests between regions and species by using forest insurance claims from all over Japan as a damage indicator. We targeted the two most damaged species in two of the most drought-affected regions from 2016 to 2021. Although landform and soil type were found to be influential factors in the Kamikawa Subprefecture of Hokkaido, these factors did not affect the drought damage in Yamaguchi Prefecture. In Kamikawa, the drought damage risk was high for Larix kaempferi on river terraces and for Abies sachalinensis on mountain areas with compacted brown forest soil. Clayey soil, which can prevent plants from absorbing water, has been known to distribute on the terraces and the mountains with compacted soil in Kamikawa. Therefore, our analysis identified clayey soil as a cause of drought vulnerability in Kamikawa. In addition, L. kaempferi was suggested to be especially vulnerable on flat terraces with less permeable clayey soil due to root damage associated with excessive soil moisture before drought. This study demonstrated that forest insurance can be used not only for damage compensation, but also as a source of information for identifying region- and species-specific risk factors for meteorological damage in forests.

The seismic response characteristics of the Yellow River terrace are crucial, as it is one of the key human activity areas. Seismic response characteristics of Yellow River terrace stations in Ningxia were analyzed using strong-motion earthquake records from seismic observations in the Loess Plateau and corresponding station data, employing the Horizontal-to-Vertical Velocity Response Spectrum Ratio method. The seismic vulnerability coefficient (Kg) was computed, and the bedrock depth was estimated. The results indicate that the spectral ratio curves of the Yellow River terrace can be classified into three types: single-peak, multi-peak, and ambiguous-peak types. The predominant period of the terraces ranges from 0.12 to 1.22 s, and the amplification factor ranges from 2.87 to 10.29. The calculated Kg values range from 2.09 to 63.24, and the bedrock depth ranges from 10.68 to 168.11 m. The site's predominant period, amplification factor, high Kg values, and deep bedrock depths can significantly impact seismic design, potentially leading to greater damage during earthquakes. Based on the predominant period, Kg values, and bedrock depth, the seismic vulnerability of Yinchuan is assessed to be high.

Electric power transmission lines both cause and are impacted by wildfires and fuel breaks are crucial to mitigate wildfire hazard along and in conjunction with these infrastructures. Information about fuel dynamics is crucial for planning and maintaining fuel treatments, namely, to define their frequency. We sampled mechanically treated power line corridors representative of wide variation in climate, soil, and plant communities in Portugal and at different times since treatment. Non-destructive methods were used to assess ground cover and height per fuel stratum and the corresponding phytovolumes and fine fuel loads were calculated. Variability in fuel metrics was described by fitting logistic generalized linear models or linearized power functions based on time since disturbance and categorical variables for the effect of regeneration strategy, soil-richness structure, and climate. Time since treatment dominated fuel abundance and recovery was faster in communities of obligate resprouters in comparison with obligate or facultative seeders and in light- versus heavy-textured soils. No apparent effect of local climate was found given the short-lived impact of fuel treatments under the productive regional Mediterranean climate. The results provide a decision-making basis to refine the current treatment periodicity. Mechanical-treatment intervals of 3-5 years or 6-10 years are advised, respectively, for wildfire control and to minimize infrastructure damage.

Context Invasive plants are one of the most significant threats to woodlands globally. Methods of invasive plant control include manual removal and herbicide application. While the impacts of control methods on invasive and off-target native plant species are often explored, the impacts on below-ground organisms, such as fungi, are less well understood.Aims We conducted a glasshouse trial to investigate the responses of soil fungal communities to herbicides and manual removal that are used to control common invasive plant species in Banksia woodland in south-western Australia.Methods Broad spectrum (glyphosate and pelargonic acid) and grass-specific (fluazifop-p-butyl) herbicides were separately applied to pots containing either Ehrharta calycina, a key invasive grass species or Eucalyptus todtiana, a native woodland tree at the recommended woodland rate. After six weeks, samples of treated soils were subjected to high throughput sequencing to determine fungal community diversity, richness, relative abundance, composition and putative ecosystem function.Key results Pelargonic acid induced the widest range of changes including decreased fungal richness and Shannon diversity but all herbicides affected community composition. Within functional groups, fluazifop-p-butyl led to a significant decrease of symbiotrophs in the mycorrhizal species.Conclusions We show that invasive species management, in the manner applied, can lead to immediate changes in fungal community composition.Implications Observed patterns require further exploration, particularly repeat testing under different environmental conditions, to better determine the impact and mode of action of herbicides on below-ground organisms. The functional changes in the soil fungal community could further disturb the soil fungal community and complicate subsequent management considerations.