Effects Of Microtopography Research Articles

Microtopography and vegetation generate uneven predation pressure on forest insects

Predation plays an important role in the coexistence of multiple species within forest ecosystems. It is spatially heterogeneous and influenced by the surrounding environment at different spatial scales. Studies focusing on multiple environmental factors in systems with high spatial complexity are lacking, but elucidating the effects of local environmental factors within a forest could assist in understanding the effects of local differences in predation pressures on multispecies coexistence. Here, we examined the effects of microtopography and vegetation on predation pressure using the model caterpillar method. We hypothesized that differences in microtopography and vegetation types would result in different predation pressures on invertebrates within a forest. Insect attacks were dominant throughout the study period. The attack rates on the model caterpillars were also lower on hill tops and evergreen deciduous trees. Predation pressure within the forest was heterogeneous and independently influenced by topography and vegetation type. Our results suggest that environmental heterogeneity within forests may lead to highly variable predation pressures and affect multispecies coexistence. This study suggests that microtopography and vegetation types within forests should be considered for biological control.

Fabrication of gradient structure for enhancing wear resistance of GCr15 bearing steel friction shim

The wear resistance of metallic shims under heavy load is crucial for the friction behavior of friction damper in civil engineering. This study verifies the potential of the strengthening grinding process (SGP) to enhance the wear resistance of metallic materials under heavy load. A multidisciplinary effort is shown in this paper to investigate the wear mechanism of SGP-treated GCr15 bearing steel in terms of the application scenario of civil engineering. The SGP treatment uses a multiphase abrasive comprising steel balls, corundum powder, and strengthening liquid to impact the surface of the GCr15 bearing steel. Then, a dry friction sliding test was performed on the polished, sandblasted, and SGP-treated GCr15 bearing steel. The microtopography and microstructure of these three friction shims with different treatments before and after the wear test were compared and analysed. The test results indicated the feasibility of SGP in enhancing the wear resistance of GCr15 bearing steel friction shims under heavy loads in terms of the application scenario of civil engineering. The SGP-treated sample had a more stable friction coefficient (0.475) and slighter wear compared to the other two samples due to its enhanced layer with a gradient structure and a thickness of approximately 23 μm.

Effects of Micro-Topography and Vegetation on Soil Moisture on Fixed Sand Dunes in Tengger Desert, China.

Soil moisture is a key factor in arid ecosystems, with local variations influenced by topography and vegetation. Understanding this relationship is crucial for combating desertification. Employing ANOVA, Mean Decrease Accuracy (MDA) analysis from random forest modeling and Structural Equation Modeling (SEM), this study investigates the distribution of soil moisture and its associations with topographic and vegetative factors across four micro-geomorphic units in the Tengger Desert, China. Significant heterogeneity in soil moisture across various layers and locations, including windward and leeward slopes and the tops and bottoms of dunes, was observed. Soil moisture generally increases from the surface down to 300 cm, with diminishing fluctuations at greater depths. Soil moisture peaks in the surface and middle layers on windward slopes and in deep layers at the bottom of dunes, exhibiting an initial rise and then a decline on windward slopes. Topographic (including slope direction and elevation difference) and vegetation (including shrub and herb coverage) factors significantly influence soil moisture across three depth layers. Topographic factors negatively affect soil moisture directly, whereas vegetation positively influences it indirectly, with shrub and herb abundance enhancing moisture levels. These insights inform ecological management and the formulation of soil moisture-conservation strategies in arid deserts. The study underscores customizing sand-binding vegetation to various micro-geomorphic dune units.

Microtopography effects on pedogenesis in the mudstone-derived soils of the hilly mountainous regions

Topography is a critical factor that determines the characteristics of regional soil formation. Small-scale topographic changes are referred to microtopographies. In hilly mountainous regions, the redistribution of water and soil materials caused by microtopography is the main factor affecting the spatial heterogeneity of soil and the utilization of land resources. In this study, the influence of microtopography on pedogenesis was investigated using soil samples formed from mudstones with lacustrine facies deposition in the middle of the Sichuan Basin. Soil profiles were sampled along the slopes at the summit, shoulder, backslope, footslope, and toeslope positions. The morphological, physicochemical, and geochemical attributes of profiles were analyzed. The results showed that from the summit to the toeslope, soil thickness increased significantly and profile configuration changed from A–C to A–B–C. The total contents of Ca and Na decreased at the summit, backslope, and footslope, while the total contents of Al, Fe and Mg showed an opposite trend. On the summit and shoulder of the hillslope, weathered materials were transported away by gravity and surface erosion, exposing new rocks. As a result, soil development in these areas was relatively weak. In flat areas such as the footslope and toeslope with sufficient water conditions, the addition of weathered components and the prolonged contact between water, soil, and sediment led to further chemical weathering, resulting in highly developed characteristics. Microtopography may influence physicochemical properties, chemical weathering, and redistribution of water and materials, causing variations in pedogenic characteristics at different slope positions.

Engineering crystal plane of NiCo2O4 to regulate oxygen vacancies and acid sites for alkali-free oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

The catalytic oxidation of HMF involves a cascading reaction with multiple intermediate products, making it crucial to enhance the oriented adsorption capacity of specific functional groups for accelerating the entire process. To achieve the efficient selective oxidation of HMF to FDCA, a series of NiCo2O4 catalysts with different morphologies, such as flaky, echinoids, pompon and corolla, were prepared and characterized by XRD, SEM, TEM, BET, XPS, and FTIR. Among the four catalysts, flaky NiCo2O4 exhibited the most excellent catalytic activity and stability, with a FDCA yield of 60.1% within 12 h at 80 °C without alkali participation. The excellent performance of flaky NiCo2O4 catalyst is attributed to the oxygen vacancies and acid sites generated by the exposed (400) facets. The oxygen vacancies and acid sites on the catalyst surface can precisely adsorb –CHO and –CH2-OH of HMF, respectively, and this synergistic effect promotes the efficient production of FDCA. This work is of great significance for fundamentally study the effect of micro-topography or crystal–plane reaction properties on surfaces.

Effects of Microtopography on Soil Microbial Community Structure and Abundance in Permafrost Peatlands.

Soil microorganisms play crucial roles in the stability of the global carbon pool, particularly in permafrost peatlands that are highly sensitive to climate change. Microtopography is a unique characteristic of peatland ecosystems, but how microtopography affects the microbial community structures and their functions in the soil is only partially known. We characterized the bacterial and fungal community compositions by amplicon sequencing and their abundances via quantitative PCR at different soil depths in three microtopographical positions (hummocks, flats, and hollows) in permafrost peatland of the Greater Xing'an Mountains in China. The results showed that the soil of hummocks displayed a higher microbial diversity compared to hollows. Microtopography exerted a strong influence on bacterial community structure, while both microtopography and soil depth greatly impacted the fungal community structure with variable effects on fungal functional guilds. Soil water content, dissolved organic carbon, total phosphorus, and total nitrogen levels of the soil mostly affected the bacterial and fungal communities. Microtopography generated variations in the soil water content, which was the main driver of the spatial distribution of microbial abundances. This information stressed that the hummock-flat-hollow microtopography of permafrost peatlands creates heterogeneity in soil physicochemical properties and hydrological conditions, thereby influencing soil microbial communities at a microhabitat scale. Our results imply that changes to the water table induced by climate warming inducing permafrost degradation will impact the composition of soil microbes in peatlands and their related biogeochemical functions, eventually providing feedback loops into the global climate system.

Effects of microtopography on patterns and dynamics of groundwater–surface water interactions

Groundwater–surface water interaction is greatly affected by surface topography and agricultural activities in managed agricultural regions. Such an interaction increases the complexity of hierarchical groundwater flow systems. However, the combined effects of microtopography and agricultural activities on groundwater flow patterns remain unclear. In this study, an integrated groundwater–surface water model was used to quantify the impact of microtopographic variations on groundwater flow patterns in an agricultural region in northwest China. Numerical experiments were conducted under different scenarios representing various degrees of microtopography. The results indicated that microtopography plays a pivotal role in the transfer of signals from spatiotemporally varying surface processes to the groundwater flow. Without consideration of the microtopography, the stationary fractional Gaussian noise–type infiltration processes in the vadose zone–saturated zone interface may be incorrectly simulated as non-stationary fractional Brownian motion. Furthermore, fractal analysis reveals that the scaling exponents of the pressure head are highly sensitive within the vadose zone and local flow subsystems. Microtopography plays an important role in shaping the groundwater response time (GRT) pattern, which results in a smaller average GRT but a larger core range. Contrarily, neglecting microtopography may lead to overestimation of the water table ratio (WTR), resulting in erroneous identification of groundwater patterns as topography-controlled types. This study highlights the importance of microtopography in the formation and evolution of nested groundwater flow systems and provides guidance for groundwater–surface water interaction simulations in managed regions.

Soil thickness influences the control effect of micro-topography on subsurface runoff generation in the karst hillslope critical zone

Topography plays a crucial role in predicting rainfall-runoff processes under climate change, as it affects the spatial distribution of water flow pathways. However, understanding the potential impact of high micro-topography heterogeneity on runoff generation remains challenging. We conducted high-resolution monitoring of soil moisture, instantaneous water table, and subsurface runoff in two 3D plots with different soil thicknesses (66 cm vs. 35 cm) in the karst region of southwest China. The topographic features were characterized by the soil thickness, relative elevation, and topographic wetness index obtained from a 1 × 1 m grid. The topography of the shallow-soil plot (SSP) exhibited a higher level of complexity, with a greater variability (approximately 80.0 %) in soil thickness compared to that of the deep-soil plot (DSP; approximately 61.5 %). Additionally, the SSP was prone to forming a micro-topography characterized by a combination of exposed bedrock and soil cover. In DSP, the variation in soil moisture was strongly controlled by surface topography, with elevation contributing to 52 % and 81 % of the explanation for the soil moisture at 30 cm and soil–bedrock interface, respectively. In SSP, the contribution of topography to the variation in soil moisture did not exceed 31 %. The controlling effect of topography on runoff is highlighted in SSP, with the contribution rates of surface and bedrock relative elevation reaching 79% and 97%, respectively.The weaker water storage capacity of the SSP resulted in a higher volume of subsurface runoff (161 t vs. 116 t) and frequency of runoff events (2248 vs. 1994) compared to the DSP. Accordingly, this study emphasizes that the soil–bedrock spatial heterogeneity will control the relationship between soil moisture, subsurface runoff, and terrain, which will contribute to providing a basis for flood prediction and model simulation in regions with complex topography.

Effects of microtopography on soil microbial communities in alpine meadows on the Qinghai-Tibetan Plateau

Heterogeneous habitats generated by diverse microtopography are critical in shaping soil microbial communities and their ecological functions. In this study, a combination of high-throughput sequencing technology and functional prediction was used to assess the effects of three microtopographic types (the shady slope, ravine, and sunny slope) on community structure, diversity, functional guilds, and the co-occurrence networks of soil microbes in alpine meadows. The results showed that the microbial α-diversity varied significantly across the three microtopographies, and fungal community structure was more responsive to microtopography than that of bacteria. In contrast, the co-occurrence network pattern of bacteria was more sensitive to environmental changes induced by microtopography. Mantel tests revealed that bacterial community structure was mainly impacted by plant diversity, belowground biomass, soil total phosphorus content and soil pH, and variations in fungal community structure were correlated with plant diversity, soil pH, and soil NH4+–N content. Meanwhile, regression analyses indicated that nitrogen fixers, ectomycorrhizal fungi, and endophytes relative abundances were positively linked to plant diversity, and soil pH negatively affected nitrogen fixers, ectomycorrhizal fungi, and methane oxidizers. Furthermore, different functional guilds with similar functions (e.g., ectomycorrhizal fungi vs. arbuscular mycorrhizal fungi) responded inconsistently to the microtopography, suggesting ecological niche differentiation of microorganisms in microtopographies. These findings highlight the importance of microtopography for driving bacterial and fungal diversity, community structure, functional profiles and co-occurrence networks in alpine ecosystems.

Extreme Wind Speed Estimation for Wind-Resistance Design of a Transmission Line Situated in a Typhoon-Prone and Hilly Area

The southeastern coast of China is annually threatened by typhoons originating from the northwestern Pacific Ocean, posing a risk of severe damage to coastal transmission lines. This study employs the random forest-based typhoon full-track simulation method and YM wind field to assess the wind-resistance reliability of transmission lines. The obtained extreme wind speeds of a transmission line site in Wenzhou are 33.7m/s and 35.8m/s under the 50-year and 100-year return periods, respectively. The effects of micro-topography on the extreme typhoon wind speed are further analyzed, and the extreme wind speed distribution maps of Wenzhou City and Yueqing City are plotted, respectively. The results indicate a decreasing trend in typhoon wind speed within inland regions, while micro-topography displays a substantial effect on enhancing the typhoon wind speed.

Effects of microtopography on within-field spatial variation of inherent soil properties in Andosols of Tokachi district, Hokkaido

ABSTRACT In large-scale upland cropping systems, understanding the magnitude of soil property variations and mapping the distribution are essential to improve soil nutrient management. The Tokachi district of Hokkaido has large-scale upland fields, and the soils are dominated by Andosols that inherently have characteristic clay minerals and high soil organic carbon content. In the region, microtopography is known to exist that can affect soil formation and within-field variation of the inherent soil properties. However, limited information exists about the relationship between microtopography and the spatial variation of inherent soil properties that are important for nutrient dynamics. Therefore, this study aimed to assess the effect of microtopography on the within-field variation of inherent soil properties in Andosols of Tokachi district, Hokkaido. Within a 6.6-ha field with an elevation difference of 3.2 m, four soil profiles were surveyed at different topographical positions, and 530 surface soil samples were collected at 12-m intervals. Samples were analyzed for total carbon (TC), acid-oxalate extractable Al, Fe, and Si (Alo, Feo, and Sio), pyrophosphate extractable Al and Fe (Alp and Fep), cation exchange capacity (CEC), and phosphate absorption coefficient (PAC). Geostatistical analysis was applied to understand the spatial structure of the surface soil properties. All soil profiles were dominated by volcanic parent materials, and they were classified into different types of Andosols. An exceptional variation of inherent soil properties was found in the surface soil, with TC content ranging from 35.2 to 124 g kg−1 and CEC from 20.3 to 55.7 cmolc kg−1. Geostatistical analysis showed that TC content varied over a large distance (range: 226 m) while allophane content varied at a shorter distance (range: 118 m). Our findings revealed that microtopography affected the soil water dynamics and erosion of the surface soil particles which caused the variation of TC, CEC, and allophane. Further studies must be conducted to understand the effects of the variation of these inherent soil properties on soil nutrient availability and crop productivity.

N2-fixing bacteria are more sensitive to microtopography than nitrogen addition in degraded grassland.

Soil bacteria play a crucial role in the terrestrial nitrogen (N) cycle by fixing atmospheric N2, and this process is influenced by both biotic and abiotic factors. The diversity of N2-fixing bacteria (NFB) directly reflects the efficiency of soil N fixation, and the diversity of NFB in degraded alpine meadow soil may change with different N fertilizing levels and varied slopes. However, how N addition affects the diversity of NFB in degraded alpine meadows, and whether this influence varies with slope, remain poorly understood. We conducted an N addition field experiment at three levels (2, 5, and 10 g N·m-2·a-1) to study the effects of N addition on soil NFB diversity on two different slopes in a degraded meadow on the Tibetan Plateau. There were significant differences in the dominant bacterial species between the two slopes. The Chao1 index, species richness, and beta diversity of NFB did not differ significantly between slopes, but the Shannon index did. Interestingly, N addition had no effect on the diversity of NFB or the abundance of dominant bacteria. However, we did observe a significant change in some low-abundance NFB. The community composition and diversity of NFB were significantly positively correlated with slope and soil physicochemical properties (e.g., total potassium, pH, and total nitrogen). Our study highlights the variation in NFB communities among different slopes in degraded alpine meadows and their resilience to exogenous N addition. Our results also underscore the importance of considering the effects of micro-topography on soil microbial communities in future studies of alpine ecosystems.

Synergistic effects of succession and microtopography of moraine on the fungal spatial diversity in a glacier forefield.

Primary succession and microtopography result in environmental changes and are important processes influencing the community assembly of soil fungi in the Arctic region. In glacier forefields that contain a series of moraine ridges, both processes contribute synchronously to fungal spatial diversity. To reveal the synergistic effects of succession and microtopography, we investigated the fungal community structure and environmental variables in the moraines of the Arklio Glacier, Ellesmere Island. The study sites were established at four locations from the top to the bottom of the ridge slope within each of the three moraine ridges of different post-glacial ages. The location-dependent community composition was equally diverse in both the initial and later stages of succession, suggesting that successional time could alter the effects of microtopography on the fungal community. Moreover, our results suggest that fungal communities at different locations follow different successional trajectories, even if they have passed through the same time lapse. Such a synergistic effect of succession and microtopography of moraines does not allow for parallel changes in fungal communities among moraines or among locations, suggesting that the moraine series contributes substantially to fungal spatial diversity in the glacier forefield.

Size-Dependent Locomotion Ability of Surface Microrollers on Physiologically Relevant Microtopographical Surfaces.

Controlled microrobotic navigation inside the body possesses significant potential for various biomedical engineering applications. Successful application requires considering imaging, control, and biocompatibility. Interaction with biological environments is also a crucial factor in ensuring safe application, but can also pose counterintuitive hydrodynamic barriers, limiting the use of microrobots. Surface rolling microrobots or surface microrollers is a robust microrobotic platform with significant potential for various applications; however, conventional spherical microrollers have limited locomotion ability over biological surfaces due to microtopography effects resulting from cell microtopography in the size range of 2-5µm. Here, the impact of the microtopography effect on spherical microrollers of different sizes (5, 10, 25, and 50µm) is investigated using computational fluid dynamics simulations and experiments. Simulations revealed that the microtopography effect becomes insignificant for increasing microroller sizes, such as 50µm. Moreover, it is demonstrated that 50µm microrollers exhibited smooth locomotion ability on in vitro cell layers and inside blood vessels of a chicken embryo model. These findings offer rational design principles for surface microrollers for their potential practical biomedical applications.

Assessing the resprouting vigour of an Italian coppice stand after alternative felling methods

Coppice management is attracting renewed interest because it ideally fulfils many of the demands placed on modern forestry, including wood production, soil protection, biodiversity and cultural heritage. Furthermore, coppice with standards represents a two-in-one approach that, similar to agroforestry, aims to run two silvicultural systems (coppice and high forest) on one and the same place. For the regeneration, coppice largely relies on the spontaneous resprouting of the remaining stumps. This sophisticated system aims to derive maximum use of synergetic natural forces. For that reason, it is efficient but work intensive at the same time, especially at the time of harvesting the multi-stem coppice layer with small dimensioned trees. Hence, to make the system more profitable, mechanization is required. This study endeavoured to clarify if fully mechanized procedures might replace the traditional motor manual variant. Two alternatives were tested: an excavator mounted disc saw and an excavator mounted hydraulic shear. The target parameter was the resprouting vigour of the stumps after cutting, observed over seven years in a typical central Italian coppice with standards. The test coppice was composed by oak, maple and ash. The study found no differences between the treatment alternatives, especially when accounting for the effects of microtopography and tree species. Although under the threshold for significance, the disc saw entailed a higher mortality rate, which was compensated by enhanced shoot dimensions.

Effect of Micro-Topography and Edaphic Factors on the Asafoetida Volatile Oil Components

Asafoetida volatile oil components (AVOCs) are directly affected by microenvironmental changes. Here, this research aimed to investigate the AVOCs through gradients of micro-topography and edaphic factors in an arid area in central Iran (northern hemisphere) during two consecutive years. Soil and topography data were sampled simultaneously with oleo-gum-resin sampling using 20 plots placed in the area. Data were submitted to a PCA analysis. The AVOCs were significantly affected by both micro-topography and soil properties (P < 0.01). The components of carbonothioic dihydrazide and 1,3,6-0ctatriene, 3,7-dimethyl showed the most negative and positive relationship with the micro-elevation from 0 to 60 cm (R2 = 0.39, 0.44, respectively). Some components showed severe changes depending on the geographical direction, where the highest (42.2%) and lowest (25.1%) values of carbonothioic dihydrazide were obtained under the geographical direction of south and north, respectively. Also, nitrogen, phosphorus, organic matter and silt with R2 = 0.72, 0.52, 0.84 and 0.63, respectively, were positively correlated with some AVOCs, i.e., thiopropionamide and naphthalene, 1,2,3,5,6,8a-hexahy….

Effects of microtopography on soil development of the conserved area in the Isahaya Bay polder

ABSTRACT After reclamation of the Isahaya Bay polder, a conserved area is covered with naturally developed vegetation under high groundwater level conditions. This study investigated how alluvial deposits transform into soil without utilizing artificial water drainage systems for agricultural land uses. Soils were surveyed under four vegetation compositions, including those dominated by goldenrods (GR), occupied by high-grown reeds (HRD), covered with low-grown reeds (LRD), or a mixture of goldenrods and reeds (MIX). The microtopography of the polder differentiated the research site with a higher elevation at the GR location, followed by a MIX, HRD, and a lower elevation at the LRD location. The soils were characterized by their physicochemical properties and ionic composition of the soil water. Electrical conductivity (EC), which can be an indicator of residual seawater, was lowest in the GR, followed by the MIX, HRD, and LRD. The soil moisture regimes affected by microtopography led to different frequencies of wet-dry cycles in the soil, resulting in a developing sequence of soil structure from LRD to GR with decreasing EC. The ionic composition of soil water varied with elevation and soil depth. The residual seawater still influenced the ionic composition of deeper soil horizons at lower elevations, while specifically high rates of Ca2+ and SO4 2− were observed in GR. The oxidation of pyrite is stimulated by soil aeration with lowering water level, resulting in soil acidification and the simultaneous dissolution of calcium carbonate from seashells. The sequential changes in soil properties with elevation indicated the effects of microtopography on soil moisture dynamics, which led to variations in soil formation and vegetation in the conserved area.

Effects of microtopographic patterns on plant growth and soil improvement in coastal wetlands of the Yellow River Delta.

To clarify the effects of microtopography on plant growth and soil water, salt and nutrient characteristics of saline soils in mudflats within muddy coastal zones and explore suitable microtopographic modifications. Six microtopographic modification patterns, namely, S-shaped, stripe-shaped, pin-shaped, stepshaped, dense stripe-shaped and crescent-shaped patterns, were established in the coastal mudflats of the Yellow River Delta. The soil water, salt, ion, total carbon, total nitrogen, and total phosphorus contents and their ecological stoichiometric characteristics were measured and analyzed after theimplementation of different microtopographic modification patterns, with bare mudflats as the control. The results showed that microtopographic modification significantly changed the soil water and salt contents and the soil total carbon, total nitrogen and total phosphorus contents. Compared with the bare ground, microtopographic transformation significantly promoted the growth of the pioneer plant Suaeda salsa, significantly increased the soil water and nutrient contents, and significantly decreased the soil salinity. The soil salinity was mainly reduced by Na+ and Cl- ions. The soil salinity and nutrient contents gradually decreased with increasing soil depth, indicating the occurrence of surface aggregation. Compared to that of the bare ground, the soil C/N was significantly lower and the N/P was significantly higher in the microtopographic treatments, and the overall performance suggested soil N limitation. The ions contained in the saline soil were dominated by Na+ and Cl-, followed by Mg2+ and SO4 2-, with lower contents of K+, Ca2+ and HCO3 -. Among the six microtopography modification patterns, the crescent-shaped pattern best promoted vegetation restoration. This pattern was the most effective in reducing soil salinity, with a 98.53% reduction in soil salinity compared with that of bare ground, followed by the pin-shaped pattern. Compared with that in the bare ground samples, the nutrient content in the samples from the step-shaped modification increased by 23.27%; finally, the S-shaped, step-shaped and dense stripe-shaped patterns performed poorly in terms of plant restoration and soil improvement. It is suggested that a crescent-shaped pattern should be considered first when carrying out microtopographic transformation on the beaches of the Yellow River Delta, followed by stripe-shaped and pin-shaped patterns. The dense strip-shaped should not be adopted.

Effects of Soil Particle Size on Relationship Between Mound‐Puddle Type Microtopography Roughness and Soil Erosion Rate on a Hillslope Basin: Hairsine–Rose Model Analysis

AbstractThe effects of microtopography on erosion remain uncertain, and contradictory findings have been reported in past decades, hindering full understanding and accurate prediction of the quantity and quality of soil erosion caused by rainfall‐runoff. In this study, we applied a dynamic wave and Hairsine‐Rose model simulator on hillslopes composed of various sizes of mounds and puddles. For the tested soil particles whose settling velocity is and rainfall intensity of , we found that soil erosion quantity is significantly affected by microtopographic roughness, even under the same rainfall‐runoff conditions. In addition, we found that soil particle size can potentially determine whether there is a direct or inverse proportionality relationship between microtopographic roughness and soil erosion rate on hillslopes. That is, when the land surface layer is composed of relatively small soil particles, rough microtopographies accelerate soil erosion rates compared to smooth microtopographies. In contrast, when it is composed of large soil particles, soil erosion increases more on smooth microtopographies than on rough microtopographies, at least under the tested conditions. Finally, it was revealed that the progress of the microtopographic scale armoring process is closely related to the microtopographic roughness as well as the grain size. Thus, to appropriately consider the role of microtopography in soil erosion problems, the processes of pickup, advection, and deposition related to armoring must be physically considered. Without sufficient information on these features, low prediction accuracy is expected, not only of the quantity but also in the quality of soil erosion.

Carbon sequestration and nitrogen and phosphorus accumulation in a freshwater, estuarine marsh: Effects of microtopography and nutrient loads

Wetlands are widely recognized as nutrient sinks for their ability to remove nutrients in runoff and retain them in soils. This is a valuable service, especially in agricultural watersheds, making nutrient removal one of the main goals in many wetland creation and restoration projects. However, incorporating nutrient management considerations requires site-level assessments, the scale at which wetland creation and restoration occur. Here we studied how carbon (C) sequestration, and nitrogen (N) and phosphorus (P) accumulation vary at different microtopographic levels and locations within a freshwater, estuarine marsh on the coast of Lake Erie. We further explored links between C sequestration, and N and P accumulation in recent years, and orthophosphate (PO43−), ammonium (NH4+), and nitrate (NO3−) concentrations and loads. The rates of C sequestration and N accumulation were relatively lower at spots of intermediate depth and locations closer to the wetland’s main channel. P accumulation was highest at deep spots but did not differ among locations based on distance from the channel. Empirical models showed that nitrate load is the most important variable explaining the variability in C, N, and P sequestration/accumulation (r2 = 0.57, 0.61, and 0.32, respectively) and that the relationship between inorganic nutrient loads and accumulation was negative. Our findings suggest that including microtopographic relief features in wetland creation and design, especially deeper spots, is critical to enhancing wetland ecosystems’ C, N, and P sinking capacity. Also, that upstream nitrate management should be a priority to increase benefits from C sequestration and long-term N and P accumulation.