Slope Position Research Articles

Identification, Prioritization and Mapping of Major Constraints and Potentials in the Medo Watershed the Case of West Arsi District in Central Rift Valley Area of Ethiopia

The concentration to characterize the biophysical and socio-economic features in the integrated watersheds is to identify and prioritize production constraints for designing appropriate research and development interventions. The objective of this study was to assess the current biophysical of characteristics of Medo watershed, West Arsi Zone of Oromia, Ethiopia. To do so relevant data and tools were used; ArcGIS, Microsoft Excel sheet and fundamental formulae were applied for the analysis are some. The results of the study indicated that the major land use types in the watershed are agricultural land covering 50%, vegetation (shrubs, forests and, plantations) covering 24% and settlement covering 16% out of the total land use. Slope gradient of Medo watershed ranges from zero to more than 20 and the slope gradient of 2-5 and 5-10 cover the greatest in area coverage representing 201 ha and 170 ha respectively. We can also observe that about 8% out of the total area is subjected to severe erosion. Sandy clay loam was the dominant soil textural classes in the surface soils and Phaeozems, Retinols and Andosols are the dominant soil types, which cover 57%, 36% and 7% of the sub-watershed area for lower, middle, and upper slope positions, respectively. Mean annual rainfall of the area ranges from 960.09 mm at lower part of the watershed to the 1304.93 mm at upper part of the watershed. Accordingly, Medo sub-watershed is laid in majority of at sub humid agro ecological zone. An assessment of the trees within the landscape of watershed showed some remnant natural forests and a wide variety of shrubby vegetation is encountered at all landscapes. About 40 percent of the watershed, is under high to extremely severe soil loss values (>45 ton per hectare per year). The baseline study also identified that those natural resources degradation such as land, and or/ soil fertility, reduction, and recent changes in the areas’ weather condition in line of climate change prevailing in current years are few of the many factors that are contributing to the land and crop productivity reductions in the area. Therefore, prioritizing the identified problem and preparing intervention of different technologies and development plans to solve the problems by taking into consideration the existing opportunities of the watershed.

Effects of topography and stand spatial structure on the diameter at breast height growth of major pioneer tree species of natural broad-leaved mixed forests in Zhejiang Province, China.

Based on the continuous inventory data of forest resources in Zhejiang Province in 2019 and 2021, we used statistical methods such as polynomial regression to analyze the impacts of topography and forest spatial structure on average annual diameter at breast height (DBH) growth of main pioneer tree species in natural broad-leaved mixed forests. The results showed that DBH of Schima superba, Quercus glauca, Quercus fabri, Lithocarpus glaber, Castanopsis eyrei, and Castanopsis sclerophylla were between 5-50.8, 5-41.5, 5-50.8, 5-43.9, 5-55.5, and 5-46.1 cm, respectively. We classified all the trees into three classes based on DBH: small (6-12 cm), medium (12-14 cm), and large (>26 cm). The average annual DBH growth of S. superba and Q. glauca was the highest on semi-shady slope and shady slope, with increases of 2.9%-15.7% and 1.1%-41.2%, respectively. The average annual DBH growth of large-diameter S. superba, L. glaber, C. eyrei and C. sclerophylla decreased with the increase of slope, with a maximum decrease of 27.0% for S. superba, with no significant difference among small- and medium-diameter trees as a whole. The slope position did not affect the annual DBH growth of small-diameter trees, while that of medium- and large-diameter S. superba, Q. glauca, and large-diameter Q. fabri, L. glaber decreased with the change of slope position from downhill, mesoslope, uphill to ridge, with a maximum decrease of 28.1% for L. glabe, and the major-diameter C. eyrei was on the contrary. Appropriate increase in the mingling was beneficial to the average annual DBH growth of medium- and large-diameter trees. Moderate mixing was suitable for S. superba, while low degree mixing and moderate mixing was suitable for Q. glauca, Q. fabri and L. glaber, and intensive mixing was suitable for C. eyrei and C. sclerophylla. No significant difference was observed for minor-diameter trees under the mingling. The neighborhood comparison only had a significant effect on the average annual DBH growth of large-diameter Q. glauca, Q. fabri, and L. glaber, which was significantly higher under subdominance-moderation than moderation-inferiority. The average annual DBH growth in the study area was mainly affected by aspect and mixing degree.

A Proposed Methodology for Determining the Economically Optimal Number of Sample Points for Carbon Stock Estimation in the Canadian Prairies

Soil organic carbon (SOC) sequestration assessment requires accurate and effective tools for measuring baseline SOC stocks. An emerging technique for estimating baseline SOC stocks is predictive soil mapping (PSM). A key challenge for PSM is determining sampling density requirements, specifically, determining the economically optimal number of samples for predictive soil mapping for SOC stocks. In an attempt to answer this question, data were used from 3861 soil organic carbon samples collected as part of routine agronomic soil testing from a 4702 ha farming operation in Saskatchewan, Canada. A predictive soil map was built using all the soil data to calculate the total carbon stock for the entire study area. The dataset was then subset using conditioned Latin hypercube sampling (cLHS), both conventional and stratified by slope position, to determine the total carbon stocks with the following sampling densities (points per ha): 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8. A nonlinear error function was then fit to the data, and the optimal number of samples was determined based on the number of samples that minimized soil data costs and the value of the soil carbon stock prediction error. The stratified cLHS required fewer samples to achieve the same level of accuracy compared to conventional cLHS, and the optimal number of samples was more sensitive to carbon price than sampling costs. Overall, the optimal sampling density ranged from 0.025 to 0.075 samples per hectare.

Standards for shallow landslide identification in Brazil: Spatial trends and inventory mapping

Mapping shallow landslide inventories represents the initial stage in conducting susceptibility, vulnerability, and risk analyses. The identification of areas with a history of landslides, both past and current events, enables the detection of spatio-temporal patterns and facilitates the evaluation of morphological and geological factors. Shallow landslides are frequent in Brazil, especially along the Brazilian south and southeastern coast. Despite their high frequency, the recognition and mapping of these landslides are inadequately developed due to the absence of established mapping guidelines. This resulted of limited investments by Brazilian authorities in initiatives aimed at preventing and mitigating mass movements. Thus, the aim of this study is to establish criteria for the recognition and mapping of shallow landslides in Brazil and to evaluate their applicability in susceptibility analysis. The study area is located in Itaóca and Apiaímunicipalities, São Paulo state, southeastern Brazil. Criteria for shallow landslide recognition were created based on the absence of vegetation, shape and size, drainage network distance, slope position, planar rupture surface, and altimetric variation. An extensive landslide interpretation was carried out using a set of free access Google Earth Pro images. Susceptibility maps were developed through a bivariate statistical approach, specifically the Informative Value method. The outcomes demonstrated that incorporating the deposition area in susceptibility studies for shallow landslides led to modifications in the final mapping, a slight reduction in validation rates, and, notably, an impact on the influence of the thematic variable curvature. Therefore, it is clear that the criteria used for landslide inventory maps have a significant effect on the accuracy of susceptibility maps and should be a critical consideration in studies related to this subject.

Evaluate the effectiveness of soil and water conservation interventions in the upper Awash Basin, Ethiopia

AbstractThe central highland of Ethiopia is facing significant challenges due to land degradation, which resulted in changes to the soil's physicochemical properties. This study aims to assess the effectiveness of different conservation methods in enhancing soil physicochemical properties, reducing soil loss and erosion, and maximizing land productivity in Ankober District of Kenseta watershed. For this study, two land uses (conserved and non‐conserved land), three slope positions, and three replication with the soil depth of 0–30 cm were used for undisturbed and disturbed soil samples data collection and analysis. The survey data were collected and evaluated from 106 randomly selecting respondents' households. The results showed significant variation in the mean value of soil physical properties (bulk density, soil moisture content, soil texture) within and between conserved and non‐conserved land. The chemical properties, including pH, EC, exK, CEC, OC, OM, and available P, also changed significant across land management types and along slope position (p < 0.05). Soil managed with stone face soil bund demonstrated significant improvement in soil physicochemical properties. The results were statistically significant difference at (p < 0.05) level of significance. Majority of the respondents' households explained the soil loss and rate of soil erosion were declined and land productivity status increased after the adoption of soil and water conservation practices in the study area. Therefore, proper conservation practices are vital in minimizing the rate of soil loss, ameliorating physical and chemical properties of the soils, and enhancing land productivity.

Spatial Distribution Characteristics of Soil Carbon and Nitrogen in Citrus Orchards on the Slope of Purple Soil Hilly Area

Since the 1990s, a large area of sloping farmland in a purple soil hilly region of southwest China was converted into an orchard to prevent soil erosion, increase soil fertility, and elevate economic benefits for farmers. In order to explore the spatial distribution of soil carbon (C) and nitrogen (N) fractions on the slope of returning arable lands to citrus orchards in purple soil hilly areas, a soil sampling event was carried out in a citrus orchard at the Yanting Agro-ecological Experimental Station of Purple Soil, Chinese Academy of Sciences, to examine the differences in soil C and N fractions and their influencing factors. The results showed that the slope position had significant effects on the contents of soil total nitrogen (TN), nitrate nitrogen (NO3--N), and dissolved organic carbon (DOC) (P < 0.05), but the effects were not obvious regarding the total organic carbon (SOC) and ammonia nitrogen (NH4+-N) of the soil (P > 0.05). For topsoil (0-30 cm), the variation trend of soil NO3--N content along the slope was upper slope < middle slope < lower slope, whereas the TN and DOC contents along the slope exhibited the trend of upper slope > middle slope > lower slope. The contents of soil C and N in each slope position generally showed a downward trend with increasing soil depth (0-30 cm). The contents of soil TN, SOC, NO3--N, and DOC were significantly affected by soil depth (P < 0.05). The TN storage (0-30 cm) significantly decreased from the top to the bottom within the soil slope, with a value of 2.37, 1.89, and 1.62 t·hm-2 (reported as N) for the upper slope, middle slope, and lower slope, respectively. There was no significant difference in SOC reserves along the slope, with a range from 56.12 to 58.48 t·hm-2 (reported as C). Our results provide scientific basis for understanding the spatial distribution of soil nutrients of the restored farmland in purple soil hilly areas. Our research suggests that the spatial distribution of soil carbon and nitrogen storage should not be ignored when predicting the response of soil nutrients to land use change.

Tree canopy area-dependent changes in soil properties: a comparative study in the southern limit of boreal forest distribution

The forest distribution in relation to mountain slope position and the relationships between forest canopy area and soil physical and chemical properties in Mongolia attract the attention of scientists. In this study, we aimed to determine (1) how the slope aspect affects the forest soil physical and chemical properties, (2) how the soil variables correlate with projected canopy area. For comparative study, we established a total of 18 (20 × 25 m2 sized) sample plots in upper forest edge (UFE), upper slope of the forest (USF), lower slope of the forest (LSF), lower forest edge (LFE), sparse forest (SF), and degraded forest area (DFA) stand types with three replications. We measured the tree height, diameter and crown projection area of each growing tree in the sample plots, and collected soil samples for further soil physical and chemical analyses in the laboratory. Our results showed a high variation in growing stock (p < 0.0001), stand density and projected canopy area (p < 0.0001) in relation to mountain slope position and land-use management. We found that the slight changes in stand canopy area projection cause a high variation in soil physical and chemical properties. Among studied stand types higher means of soil temperature and bulk density and lower moisture content were observed on SF and DFA stand types. Contrary, relatively higher content of soil moisture and nutrient elements were recorded in USF, LSF, LFE. We conclude that tree canopy area becomes key determinant factor that positively influences forest soil moisture and fertility by increasing organic matter content in Mongolia.

Evaluation of soil properties variability along a toposequence in Wasinmi, Southwest Nigeria

Abstract Topography significantly influences soil development and characteristics within an uneven agricultural field. Therefore, a comprehensive understanding of soil attributes and processes through detailed pedological knowledge is crucial for effective soil management. This research was carried out in Wasinmi, southwestern Nigeria, to delineate and categorise the soils across different slopes for agricultural insights. Three soil profiles were excavated across the topographical sequence, specifically designated as upper, middle, and lower slope positions. The prevailing soil texture was sandy loam with a discernible trend of lighter soil colour as the slope descended and soil depth increased. The pH of the soil ranged from moderately acidic to slightly acidic. The saturated hydraulic conductivity and soil organic matter content were lowest on the lower slope. Available phosphorus distribution varied inconsistently with higher concentrations of heavy minerals observed at the upper slope. The study underscored the influential role of topography in soil property variations and the need for tailored management practices. The classification of the soils revealed Typic Plintustults in the upper and middle slope positions, while the soils in the lower slope were identified as Typic Kandiaquults. This study demonstrated that topography significantly influenced soil properties, thereby emphasising the need for informed practices to better support the long-term sustainability of land use and agricultural outputs in topographically diverse landscapes.

Assessing the Impacts of Soil Water Conservation Activities and Slope Position on the Soil Properties of the Gelda Watershed, Northwest Ethiopia

Assessing the Impacts of Soil Water Conservation Activities and Slope Position on the Soil Properties of the Gelda Watershed, Northwest Ethiopia

Spatial distribution of northern shrimp Pandalus eous in the Sea of Japan in relation to the seafloor environment

Abstract To explore relationships between spatial distributions of northern shrimp Pandalus eous and environmental factors along the coastline of Honshu Island in the Sea of Japan, we built delta-type two-step generalized additive models (delta-GAM) based on bottom trawl surveys conducted in 2013–2022. The models provide the first quantitative analysis of the species’ habitat, showing that its distribution is associated with bottom sediment type, depth, slope and topographic position index (TPI) alongside the effects of year and region. From the delta-GAM response plots, species habitat preferences in the Sea of Japan were estimated as follows: seafloor deeper than 283 m; muddy rather than sandy bottoms; gently sloped to flat bottoms (&lt;0.8° in slope); and valleys rather than ridges (TPI &lt; 0.9). These results were reviewed in detail along with previously reported distribution records of northern shrimp. Standardized density (s-density) per fishing grid cell (10′ square latitude–longitude mesh) estimated from the delta-GAM results indicated that this species is widely distributed on the continental slope along the coast of Honshu Island. To test plausibility of the s-density analysis, we compared s-density per fishing grid cell with nominal CPUE (kg per haul) per fishing grid cell based on official logbook data from large offshore trawl fisheries. The two were generally positively correlated by year, and the delta-GAM results were assumed to be fairly robust. Finally, potential fishing grounds were explored based on the delta-GAM results.

Pedological characteristics and classification of soils along landscape at highlands of Tsegede, Western Zone of Tigray, Ethiopia

Dynamics and distribution of soil characteristics as influenced by landscape /topographic features in acidic soils of Tsegede area in Northern Ethiopia has limited information. This study was conducted to characterize soil properties and classify major soil types. Four representative profiles along top sequence from varying slope positions crest at (Chegarkudo), upper slope and middle slope at (Endassilassie) and lower slope at (Intabela) were opened and described in-situ for morphological properties of soils and sampled horizon-wise for physico-chemical soil properties’ analysis. The results showed that soils at crest and upper-slope position were characterized by shallow depth, whereas those at middle and lower-slope positions exhibited relatively deep. The soil consistence ranges from slightly hard to hard (dry), friable to very friable (moist), yellowish red to dark red brown (dry) in color, moderate medium sub-angular to strong thick angular blocky in structure. The pH of surface soil ranged from 5.14 to 5.74 which was strongly acidic to slightly acidic and varied from clay loam to clay in texture, organic carbon, exchangeable bases and cation exchange capacity varied with profile depth. Based on the world reference base legend, the soils were classified as Skeletic Leptosols about 3756 ha, Cambic Leptosols about 1926 ha, Dystric Cambisols about 1883 ha and Leptic Cambisols about 1966 ha.

Potential of pine forest in controlling soil erosion in Himalayan region - Investigation using fallout radionuclide (137Cs) measurements

The Himalayas possess a distinctive topography owe to the dynamic interplay of tectonic activity, geological erosion and sedimentation, glacial processes, and climatic influences over the millions of years. The rugged, steep terrain and poor land management make it more prone to water erosion, negatively impacts the soil, affecting the goods and services supported by the soil ecosystems. Traditional methods used in soil erosion assessment face limitations when dealing with topographically complex hillslopes. The use of Fallout Radionuclide (FRN) -137Cs provides a feasible alternative for measurement of soil erosion in the region with such topography. However, there is lack of 137Cs-based soil erosion studies in the north-west Himalayas. Pine (Pinus roxburghii) is the predominant forest type in the Himalayas, offering numerous benefits to both natural ecosystems and human beings. In this study, we selected a typical steep hillslope covered with pine forest in the Himalayas for soil erosion assessment. The study measured 137Cs reference inventory of 1409 Bq m−2 in the landscape. Importantly, the concentration of 137Cs along the hillslope positions showed a significant variation attributed to topographic variability. Topographic factors, such as the slope shape and gradient, were identified as the major governing parameters of soil erosion in the hilly and mountainous region. The net soil erosion rate over hillslope positions revealed highest at upper hillslope followed by ridge, middle and valley hillslope positions. The net soil erosion rate under the pine forest ranged from 8.0 to 14.6 t ha−1 yr−1, with an average rate of 9.9 t ha−1 yr−1. Erosion rate over the hillslope positions were found in accordance to the soil loss tolerance limit (SLTL) except for the upper hillslope, indicating it as critical slope position requires to adopt suitable conservation measures. The study signifies the role of the forest in mitigating soil erosion and, in turn, conserving soil resources. The findings provide crucial insights and guidance to land managers and decision-makers, emphasizing the necessity of conserving and restoring forests in the Himalayas.

Multi-Scale Periodic Variations in Soil Moisture in the Desert Steppe Environment of Inner Mongolia, China

Uncovering the complex periodic variations in soil moisture can provide a significant reference for climate prediction and hydrological process simulation. We used wavelet analysis to quantify and identify the multi-scale periodic variations of soil moisture in the desert steppe of Inner Mongolia from 2009 to 2019 and analyzed the differences between the multi-scale periodic changes in soil moisture at the bottom (BS) and upper slope (US). The results show that the interannual variability in soil moisture at the BS and US has a significant upward trend. Moreover, the amount and volatility decrease with the increase in soil depth in the range of 0–30 cm, and the soil moisture at the BS is 26.4% higher than the US. The soil moisture has periodic changes of 0.5a, 1a, 2a, 3a and 3.5a in the desert steppe environment of Inner Mongolia. The periodic structure and intensity of different slope positions are greatly different. Soil moisture at the US has more complex multi-scale periodic changes, and the periodic oscillations of 3.5a, 3a, and 1a are dominant. The periodic oscillations of 0.5a and 1a are dominant at the BS. At the BS, the intensity of periodic oscillation of 1a after January 2015 has weakened. The weakening of soil moisture by temperature, rainfall and soil temperature caused the change in the multiple time-scale periodic oscillation of soil moisture.

Varying particle size selectivity of soil erosion along a cultivated catena

Abstract Sheet erosion is a complex multi-factor-dependent process with high spatial heterogeneity on hillslopes. Although the individual factors have been well studied, their aggregated effect on size-selective erosional processes is highly uncertain. Therefore, this study concentrates on the aggregate size distribution and effective particle size distribution (PSD) of the aggregates in the soil loss, collected from different simulated hillslope positions and surface conditions. These simulated hillslope positions combine moisture content from the extremely dry to the saturated with related slope positions of 2, 5, and 12% steepness and different surface roughness (tilled and crusted surfaces) modelled in a laboratory rainfall simulator. Using hierarchical cluster analysis, the PSD of the aggregates was separated into three groups based on the differences in the 59–116 µm range of the PSD histograms, namely, macro-aggregates, 50–250 µm sized micro-aggregates, and &lt;50 µm sized fractions were classified into distinct groups, although some micro-aggregate samples were classified into the macro-aggregate group. PSDs from the 50–250 µm aggregate size fraction were clustered into a group of macro-aggregates if the PSD changed with time (during the rainfall event), notably on rough surfaces. The role of the specified size range in the classification is believed to be due to the parallel presence of aggregates and single particles in this range. As aggregates have a lower density than mineral particles, they tend to be enriched in soil loss under low-energy runoff conditions. Moreover, all samples in the &lt;50 µm fraction clustered into the macro-aggregate group were eroded from the smooth/crusted surface, probably due to the presence of larger particles. The results indicate that the combined effect of erosional factors is not apparent, and the impact of the crust and extreme moisture content on the selectivity and size distribution of the sediment requires further investigation.

Pedogenic effect and the impact of erosion factors on topsoil magnetic susceptibility enhancement

The main aims of this study were to i) investigate the impact of erosion factors including land use, slope position, and lithology on magnetic susceptibility (MS) of soil, and ii) detecting the pedogenic effect on MS enhancement using simple methods, including median absolute deviation (MAD), topsoil-subsoil difference methods, MS magnitude and Dearing’s model. Soil cores were sampled along five slope positions in two transects selected in forested and cultivated lands in a watershed located in north of Morocco. The results showed higher values of MS in the upperslopes in forested land due to soil stability, and lower ones in middleslopes and lowerslopes due to soil erosion. However, MS is higher in cultivated land in middleslopes due to soil deposition and it is lower in the upperslopes due to erosion. The results confirmed the pedogenic effect on MS. This is confirmed by i) enhanced Forster factor and low values of magnetic susceptibility background, ii) dominance of ultrafine super-paramagnetic/stable single-domain ferrimagnetic grains in almost all studied soils, and iii) absence of anomaly in MAD data set and pertinence of the results of MAD and topsoil-subsoil difference methods.

Influence of Topography on UAV LiDAR-Based LAI Estimation in Subtropical Mountainous Secondary Broadleaf Forests

The leaf area index (LAI) serves as a crucial metric in quantifying the structure and density of vegetation canopies, playing an instrumental role in determining vegetation productivity, nutrient and water utilization, and carbon balance dynamics. In subtropical montane forests, the pronounced spatial heterogeneity combined with undulating terrain introduces significant challenges for the optical remote sensing inversion accuracy of LAI, thereby complicating the process of ground validation data collection. The emergence of UAV LiDAR offers an innovative monitoring methodology for canopy LAI inversion in these terrains. This study assesses the implications of altitudinal variations on the attributes of UAV LiDAR point clouds, such as point density, beam footprint, and off-nadir scan angle, and their subsequent ramifications for LAI estimation accuracy. Our findings underscore that with increased altitude, both the average off-nadir scan angle and point density exhibit an ascending trend, while the beam footprint showcases a distinct negative correlation, with a correlation coefficient (R) reaching 0.7. In contrast to parallel flight paths, LAI estimates derived from intersecting flight paths demonstrate superior precision, denoted by R2 = 0.70, RMSE = 0.75, and bias = 0.42. Notably, LAI estimation discrepancies intensify from upper slope positions to middle positions and further to lower ones, amplifying with the steepness of the gradient. Alterations in point cloud attributes induced by the terrain, particularly the off-nadir scan angle and beam footprint, emerge as critical influencers on the precision of LAI estimations. Strategies encompassing refined flight path intervals or multi-directional point cloud data acquisition are proposed to bolster the accuracy of canopy structural parameter estimations in montane landscapes.

Numerical classification of termite-mediated soils along toposequences and rangeland use influenced soil properties in southeast Ethiopia

Despite termite-induced soil mixing, summarizing termite-affected soil horizons is difficult, while the lack of accurate information on the pedogenic processes featured by termite bioturbation, topography, and land use limits an effort to address land degradation. A study was therefore carried out to quantitatively classify the soils and describe them based on rangeland uses. Based on cluster analysis, five representative soil profiles were studied at different topographical positions. Soil samples were collected from mounds and adjacent soils under enclosure, cultivated, and open-grazing land at the summit and foot slope positions. Agglomerative clustering showed low Ca2+, CEC, pH, and Mg2+ that described cambic horizons formed Cambisols at the summit and back slope. Eluviation-illuviation processes formed Luvisols on the toe slope and foot slope, whereas clay and high CEC described argic horizons. High Ca2+, CEC, pH, and Mg2+ described calcic horizons that formed Calcisols on the bottom slope. Divisive clustering showed that soil properties varied slightly between Cambisols and Luvisols at different topographies. However, the Luvisols on the toe slope were differentiated from the soil on the foot slope by predominant pedogenetic clay formation and a distinctly increased CEC. Calcisols are placed in other clusters due to their distinct properties. Agglomerative clustering reflected pedogenic processes and differentiated diagnostic horizons, while divisive clustering matched WRB classification. The results of this study also showed that termite-mediated soil properties were dictated by rangeland use, and pedogenesis was more noticeable on open-grazing land than on enclosure or cultivated land.

Spatiotemporal heterogeneity of soil available nitrogen during freeze–thaw cycles in a watershed: A 3‐year investigation

AbstractThe spatial pattern of soil available nitrogen (AN) is the key reference for farmland fertilization however, it is still unclear how freeze–thaw cycles (FTC) altered the spatiotemporal heterogeneity of AN at the watershed scale. In this study, the geostatistical, traditional analysis and structural equation models were used to detect how topography, land management, and soil properties influence the spatiotemporal heterogeneity of AN in both before‐ and after FTCs of Mollisols of a watershed in Northeast China for three consecutive years. The results showed that AN decreased in &gt;88% of areas of the watershed after FTCs, and the mean value significantly decreased by &gt;7.6% (&gt;10.4 mg kg−1) in 0–20 cm soil depth during 2016–2017 years and 2017–2018 years. The AN distribution, especially in the surface soil layer, tended to be aggregated after FTCs. The AN decreased in the areas near the areas of top slope position, while it tended to increase in areas of downslope position covered by forest although the total N decreased here after FTCs. The AN‐change (ANbefore FTCs minus ANafter FTCs) influenced by land use types was greater than slope steepness. The slope aspect as the key factor combined with slope steepness, slope position, and previous crops influenced the spatiotemporal heterogeneity of AN‐change after FTCs. The higher content of AN before FTCs accelerated more N loss during FTCs, and this process was mainly influenced by soil pH, nitrogen (N), and phosphorus. The N loss (5.7%) did not significantly alter the AN‐change after FTCs in the watershed. Generally, the spatial heterogeneity of AN‐change was mainly influenced by topography, land management, and soil properties (before FTCs) during FTCs in the watershed. In order to sustain a high level of AN, the mediation of N transformation and both vertical‐ and horizontal migration, caused by the dynamics of soil water potential and snowmelt erosion should be considered during FTCs.

LEVANTAMENTO E ANÁLISE TEMPORAL E EVOLUTIVA DAS EROSÕES HÍDRICAS LINEARES EM UMA ENCOSTA AMOSTRAL DO CÓRREGO DO LEOPOLDO

The article presents a temporal and evolutionary analysis of linear water erosion, as from a survey of a sample hillslope of the Leopoldo river, located in the municipality of Agudos (SP). The survey was elaborated from satellite images made available by Google Earth, which allowed to identify the main characteristics of erosive features. The analyzed characteristics are: slope position, length, width, line of inclination, shape, evolutionary stage, incision system, possible origin, curvature longitudinal and transversal. So, the article made it possible to study the erosions’ behavior and the relationship with local morphology.

Clarifying the Main Root Distribution of Trees in Varied Slope Environments Using Non-Destructive Root Detection

Tree stability relies on the characteristics of both root and crown structures. However, studying root systems is challenging due to their underground location, often requiring destructive methods for assessment. Non-destructive approaches offer potential solutions, such as the root detector tool. However, research in this area remains limited and requires further development. This study aims to evaluate the root detector tool by inspecting the radial root distribution in trees with different tree crown shapes, both excurrent (Agathis loranthifolia) and decurrent (Samanea saman), which grow in various soil slopes and soil slope positions. In addition, we establish correlations between tree morphometry, the physical properties of soil, root attributes, sound wave velocity, and their relationship. Based on the results, it was found that the root detector tool is effective in evaluating root distribution, including identifying the main root. The slope position of the tree in a slope class influences the radial distribution of the main roots. This is related to the crown growth as indicated by the direction of its crown. Principal Component Analysis (PCA) findings suggest that parameter morphometric and soil and root properties data clustering align with slope position rather than slope class.