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Surface microrollers are promising microrobotic systems for controlled navigation in the circulatory system thanks to their fast speeds and decreased flow velocities at the vessel walls. While surface propulsion on the vessel walls helps minimize the effect of strong fluidic forces, three-dimensional (3D) surface microtopography, comparable to the size scale of a microrobot, due to cellular morphology and organization emerges as a major challenge. Here, we show that microroller shape anisotropy determines the surface locomotion capability of microrollers on vessel-like 3D surface microtopographies against physiological flow conditions. The isotropic (single, 8.5 μm diameter spherical particle) and anisotropic (doublet, two 4 μm diameter spherical particle chain) magnetic microrollers generated similar translational velocities on flat surfaces, whereas the isotropic microrollers failed to translate on most of the 3D-printed vessel-like microtopographies. The computational fluid dynamics analyses revealed larger flow fields generated around isotropic microrollers causing larger resistive forces near the microtopographies, in comparison to anisotropic microrollers, and impairing their translation. The superior surface-rolling capability of the anisotropic doublet microrollers on microtopographical surfaces against the fluid flow was further validated in a vessel-on-a-chip system mimicking microvasculature. The findings reported here establish the design principles of surface microrollers for robust locomotion on vessel walls against physiological flows.

Gravel-bed microtopographies are closely connected with many aspects of river dynamics, including incipient sediment motion, sediment transport, flow structure, and flow resistance. Grain arrangement and grain size are two important parameters for quantitatively characterizing gravel-bed microtopographies. However, how grain arrangement and grain size affect gravel-bed microtopographies is still unknown. For this research, fifteen groups of uniform gravel samples were obtained by screening natural river sediment. Then, these uniform gravel samples were separately used to artificially pave gravel beds with six typical types of grain arrangements in a laboratory, and the gravel-bed elevations were measured. On this basis, the effects of grain arrangement and grain size on gravel-bed microtopographies were analyzed using statistical parameters and variograms. The experimental results showed that the elevation frequency distributions for the stacked-layer type of gravel beds established negatively skewed, leptokurtic, and unimodal shapes, but those for the other bed types exhibited bimodal shapes; therein, the main peaks for the one-layer and imbricate bed types were close to a normal distribution. The stacked-layer and one-layer types of gravel beds are approximately isotropic, while the imbricate and striped types are anisotropic. The spherical variogram model can be used as a good theoretical model to quantify the elevation variabilities for the stacked-layer, one-layer, and imbricate types of gravel beds. The gravel nuggets of elevation variograms for these three types of gravel beds are insensitive to the grain arrangement and decrease when the grain size increases, but the sills and correlation lengths linearly increase with increasing grain size. •The effects of grain arrangement and grain size on the gravel-bed microtopographies are discussed using statistical parameters and variograms.•The elevation frequency distributions for the stacked-layer type of gravel beds exhibit negatively skewed, leptokurtic and unimodal shapes, but those for the one-layer, imbricate, striped, orthogonal-grid, and staggered-grid types of gravel beds exhibit bimodal shapes.•The stacked-layer and one-layer types of gravel beds are approximately isotropic, but the other types of gravel beds are anisotropic.•The spherical variogram model can be used to excellently quantify the elevation variabilities for the stacked-layer, one-layer, and imbricate types of gravel beds.

In degraded landscapes, recolonization by pioneer vegetation is often halted by the presence of persistent environmental stress. When natural expansion does occur, it is commonly due to the momentary alleviation of a key environmental variable previously limiting new growth. Thus, studying the circumstances in which expansion occurs can inspire new restoration techniques, wherein vegetation establishment is provoked by emulating natural events through artificial means. Using the salt-marsh pioneer zone on tidal flats as a biogeomorphic model system, we explore how locally raised sediment bed forms, which are the result of natural (bio)geomorphic processes, enhance seedling establishment in an observational study. We then conduct a manipulative experiment designed to emulate these facilitative conditions in order to enable establishment on an uncolonized tidal flat. Here, we attempt to generate raised growth-promoting sediment bed forms using porous artificial structures. Flume experiments demonstrate how these structures produce a sheltered hydrodynamic environment in which suspended sediment and seeds preferentially settle. The application of these structures in the field led to the formation of stable, raised sediment platforms and the spontaneous recruitment of salt-marsh pioneers in the following growing season. These recruits were composed primarily of the annual pioneering Salicornia genus, with densities of up to 140 individuals/m² within the structures, a 60-fold increase over ambient densities. Lower abundances of five other perennial species were found within structures that did not appear elsewhere in the pioneer zone. Furthermore, recruits grew to be on average three times greater in mass inside of the structures than in the neighboring ambient environment. The success of this restoration design may be attributed to the combination of three factors: (1) enhanced seed retention, (2) suppressed mortality, and (3) accelerated growth rates on the elevated surfaces generated by the artificial structures. We argue that restoration approaches similar to the one shown here, wherein the conditions for natural establishment are actively mimicked to promote vegetation development, may serve as promising tools in many biogeomorphic ecosystems, ranging from coastal to arid ecosystems.

Wetland vegetation is the material basis for the formation and development of alpine peatlands. Investigating the relationship between species diversity of plant communities and soil organic carbon (SOC) helps understanding carbon pool source-sink dynamics in alpine peatlands. This study conducted in Zoige Plateau alpine peatlands employed the community survey method to explore changes in species diversity of plant communities and SOC across different habitats and their relationship. Results indicated that from the peatland center to the edge, alpine peatland community types underwent succession as follows: Carex atrofusca community, Carex muliensis  +  Equisetum fluviatile community, Blysmus sinocompressus  +  Carex muliensis community, Kobresia kansuensis  +  Blysmus sinocompressus community, and Kobresia tibetica  +  Deschampsia cespitosa community. The SOC, water level, soil water content, and biomass of Cyperaceae plants decreased, while community coverage, density, and soil available nitrogen increased. The Shannon–Wiener index and Pielou index increased, while Simpson index decreased. The water level, soil water content, and soil available nitrogen were the main factors influencing the spatial distribution patterns of plant communities. The community density, coverage, biomass of Cyperaceae plants, and water level were the main factors influencing species diversity of plant communities. SOC was highly significantly positively correlated with Simpson index, and negatively correlated with Shannon–Wiener index and Pielou index ( p  ≤ 0.01). As water level dropped and waterlogged extent diminished, grass hummock microtopography transitioned from spotted to ridged and then to massed. Habitat filtering and environmental stress caused dominant species succession and species diversity of plant communities to change, resulting in SOC content and the quality of carbon pool to decrease in alpine peatlands.

Mosses in northern ecosystems are ubiquitous components of plant communities, and strongly influence nutrient, carbon and water cycling. We use literature review, synthesis and model simulations to explore the role of mosses in ecological stability and resilience. Moss community responses to disturbance showed all possible responses (increases, decreases, no change) within most disturbance categories. Simulations from two process-based models suggest that northern ecosystems would need to experience extreme perturbation before mosses were eliminated. But simulations with two other models suggest that loss of moss will reduce soil carbon accumulation primarily by influencing decomposition rates and soil nitrogen availability. It seems clear that mosses need to be incorporated into models as one or more plant functional types, but more empirical work is needed to determine how to best aggregate species. We highlight several issues that have not been adequately explored in moss communities, such as functional redundancy and singularity, relationships between response and effect traits, and parameter vs conceptual uncertainty in models. Mosses play an important role in several ecosystem processes that play out over centuries – permafrost formation and thaw, peat accumulation, development of microtopography – and there is a need for studies that increase our understanding of slow, long-term dynamical processes.

Summary Dead fungal mycelium (necromass) represents a critical component of soil carbon (C) and nutrient cycles. Assessing how the microbial communities associated with decomposing fungal necromass change as global temperatures rise will help in determining how these belowground organic matter inputs contribute to ecosystem responses. In this study, we characterized the structure of bacterial and fungal communities associated with multiple types of decaying mycorrhizal fungal necromass incubated within mesh bags across a 9°C whole ecosystem temperature enhancement in a boreal peatland. We found major taxonomic and functional shifts in the microbial communities present on decaying mycorrhizal fungal necromass in response to warming. These changes were most pronounced in hollow microsites, which showed convergence towards the necromass‐associated microbial communities present in unwarmed hummocks. We also observed a high colonization of ericoid mycorrhizal fungal necromass by fungi from the same genera as the necromass. These results indicate that microbial communities associated with mycorrhizal fungal necromass decomposition are likely to change significantly with future climate warming, which may have strong impacts on soil biogeochemical cycles in peatlands. Additionally, the high enrichment of congeneric fungal decomposers on ericoid mycorrhizal necromass may help to explain the increase in ericoid shrub dominance in warming peatlands.

• Dead fungal mycelium (necromass) represents a critical component of soil carbon (C) and nutrient cycles. Assessing how the microbial communities associated with decomposing fungal necromass change as global temperatures rise will help in determining how these belowground organic matter inputs contribute to ecosystem responses. • In this study, we characterized the structure of bacterial and fungal communities associated with multiple types of decaying mycorrhizal fungal necromass incubated within mesh bags across a 9°C whole ecosystem temperature enhancement in a boreal peatland. • We found major taxonomic and functional shifts in the microbial communities present on decaying mycorrhizal fungal necromass in response to warming. These changes were most pronounced in hollow microsites, which showed convergence towards the necromass-associated microbial communities present in unwarmed hummocks. We also observed a high colonization of ericoid mycorrhizal fungal necromass by fungi from the same genera as the necromass. • These results indicate that microbial communities associated with mycorrhizal fungal necromass decomposition are likely to change significantly with future climate warming, which may have strong impacts on soil biogeochemical cycles in peatlands. Additionally, the high enrichment of congeneric fungal decomposers on ericoid mycorrhizal necromass may help to explain the increase in ericoid shrub dominance in warming peatlands.

The construction of soil surface microtopography not only effectively mitigates soil erosion, improves soil structure, and enhances soil ecological functions, but also significantly optimizes the seedbed environment for seedling emergence and crop growth. In this study, targeting the specific characteristics of red-yellow soils in Southern China, a quadrangular frustum-shaped soil surface microtopography processing device was designed and fabricated based on the 2BYG-230 rapeseed seeder. The motion trajectory and force distribution of the device were analyzed using the Discrete Element Method (DEM) software, EDEM, followed by three-factor and three-level orthogonal tests. The results indicated that the order of significance for factors affecting the microtopography formation effect was working load > working speed > microstructure height. Using the formation qualification rate as the evaluation index, the soil disturbance patterns were analyzed to determine the optimal combination of operating parameters: a working load of 260 N, a working speed of 0.34 m/s, and a microstructure height of 42 mm. Under these optimized conditions, the microtopography formation qualification rate reached 93.6%. Furthermore, the seedling emergence rate following the operation of the optimized device was 74.33%, representing a 4.96% increase compared to pre-optimization levels. The optimized processing device designed in this study markedly outperformed its predecessor, creating a soil surface microtopography more conducive to rapeseed growth while demonstrating substantial potential for water and soil conservation and ecological improvement. This research provides theoretical support for enhancing the ecological functions of Southern red-yellow soils and for the structural design of surface microtopography processing equipment.

Warming is expected to increase the net release of carbon from peatland soils, contributing to future warming. This positive feedback may be moderated by the response of peatland vegetation to rising atmospheric [CO2] or to increased soil nutrient availability. We asked whether a gradient of whole-ecosystem warming (from + 0 °C to + 9 °C) would increase plant-available nitrogen and phosphorus in an ombrotrophic bog in northern Minnesota, USA, and whether elevated [CO2] would modify the nutrient response. We tracked changes in plant-available nutrients across space and through time and in comparison with other nutrient pools, and assessed whether nutrient warming responses were captured by a point version of the land-surface model, ELM-SPRUCE. We found that warming exponentially increased plant-available ammonium and phosphate, but that nutrient dynamics were unaffected by elevated [CO2]. The warming response increased by an order of magnitude between the first and fourth year of the experimental manipulation, perhaps because of dramatic mortality of Sphagnum mosses in the surface peat of the warmest treatments. However, neither the magnitude nor the temporal dynamics of the responses were captured by ELM-SPRUCE. Relative increases in plant-available ammonium and phosphate with warming were similar, but the response varied across raised hummocks and depressed hollows and with peat depth. Plant-available nutrient dynamics were only loosely correlated with inorganic and organic porewater nutrients, likely representing different processes. Future predictions of peatland nutrient availability under climate change scenarios must account for dynamic changes in nutrient acquisition by plants and microbes, as well as microtopography and peat depth.

【Objective】 Crust is a thin soil layer formed on soil surface when water on the soil surface recedes; continuing soil drying after that could result in cracks to develop. Crusts and cracks could significantly affect water infiltration and soil water evaporation, and the purpose of this paper is to experimentally study how crusts form and cracks subsequently develop following a rainfall on a slope. 【Method】 The experiment was conducted on a slope watered by artificial rainfall. After the rainfall stopped, we measured physical properties of the crusts, imaged the initiation and development of cracks in them at different locations on the slop. These images were processed using MATLAB to quantify their morphological characteristics as well as their relationship with soil water content. 【Result】 Based on where the crusts were formed, they can be classified into structural crusts, depositional crusts and transitional crusts, with different physical properties. The depositional crusts have the highest volumetric weight and clay content. In contrast, the structural crusts have the greatest sand particle content. The morphology of cracks developed in the crusts at different locations in the gully differed from each other significantly. For crusts where the cracks developed, their impacts on crack area ratio (RC), length density of the cracks (LC), and the average width of the crack (Wi) were ranked in the order of depositional crusts

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