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[Objective] On the basis of considering the differences of soil property, terrace form and rainfall type, we aimed to establish the estimation method and framework of water storage and retention efficiency of terrace. [Methods] By using soil reservoir calculation model and infiltration model, we explored the prediction methods of soil water distribution in saturation-excess runoff and infiltration-excess runoff. Moreover, based on the Richards equation, we analyzed the two-dimensional infiltration of soil profiles at different field and ridge boundaries. On this basis, we constructed the scenario of soil water movement under single runoff generation mode or two runoff generation modes under four types of rainfall patterns, including pre-peak rainfall, uniform rainfall, post-peak rainfall, and stepped rainfall patterns. [Results] We proposed the distributed estimation method of soil water storage efficiency of terrace field, and the maximum water storage capacity (WM) of soil in a single terraced field was calculated. For different types of terraces, the anti-lateral seepage effect of stone walled bench terrace was the best, and the anti-lateral seepage effect of earth banked terrace was the worst, and the new soil ridge terrace with large pores, small density and short construction time lost more water than the soil ridge terrace with long construction time. The critical time (t) of full flow production under different rain patterns was obtained. [Conclusion] This estimation method could greatly reduce the dependence on field facilities and equipment, and reduce the input cost. With the help of field investigation and sampling, the efficiency of terraced water storage could be estimated based on model simulation. In addition, the method could be used to estimate the water storage efficiency of terrace on a regional scale according to the distributed calculation data of the water storage efficiency of a single terrace field, and provided a reference for the estimation of the water storage efficiency of different regional terraces.

[Objective] Northeast China, with its unique resources advantages, provides one-third of China’s commodity grain, making it a crucial part of national food security. Analyzing the spatial distribution, spatiotemporal evolution, and driving forces of grain crop cover types and cropping patterns in Northeast China is crucial for preserving the region’s “black soil granary”. [Methods] Based on Google Earth Engine (GEE), this study integrated existing crop cover type product from 2017 to 2019 with remote sensing extraction results of major grain crops from 2019 to 2021, analyzed the spatiotemporal change characteristics of grain crop planting types and cropping patterns, then revealed the driving forces by using geodetector. [Results] (1) Using phenological information, a multi-feature random forest classification method was employed to effectively extract three major grain crops: maize, soybean, and rice. In 2019, a high Kappa coefficient of 0.908 was achieved, indicating high classification accuracy and consistency in terms of area. (2) In the past five years, the shifting of grain crops from soybeans to maize has been the dominant trend in Northeast China. The shift types include soybean to maize to maize, soybean to soybean to maize, and maize to maize to soybean, accounting for 29.4%, 24.9%, and 19.1% of the total transition area, respectively. The cropping patterns of grain crops in Northeast China exhibit high spatial heterogeneity, with the maize continuous cropping pattern, rice continuous cropping pattern, and soybean-maize continuous-preference rotation pattern accounted for 46.2 %, 23.5 %, and 13.2 % of the total cropping patterns area, respectively. (3) The spatiotemporal dynamics of cropping patterns was significantly driven by natural and anthropogenic factors. Elevation, topographic wetness index, slope, rice price fluctuation, and soybean price fluctuation were important single factors that explain the spatiotemporal changes of cropping patterns. The interactive explanatory power of elevation, active accumulated temperature slope, and economic policy factors was high, and in descending order from elevation∩soybean subsidy variation, elevation∩active accumulated temperature slope, elevation∩fertilization cost variation, elevation∩rice subsidy variation, to elevation∩maize price variation. [Conclusion] During the period from 2017 to 2021, there was a notable shift in the major grain crop cover types in Northeast China, characterized by a transition from soybean to maize, while rice cultivation remained consistent. The spatial distribution of different cropping patterns was influenced by a combination of factors including topography, economy, and policy.

Vegetation plays a key role in trapping sediments and further controlling pollutants. However, few studies were conducted to clarify the erosion and deposition laws of sediments and the influence factors caused by vegetation patch properties, which is not conducive to the revelation of riverbank protection and erosion prevention. Therefore, this study investigated the change in scouring and deposition characteristics around submerged vegetation patches of nine kinds of typical configurations and their influencing factors. Vegetation patches were assembled from three vegetation densities (G/d = 0.83, 1.3, and 1.77, representing dense, medium, and sparse, respectively), and three vegetation patch thicknesses (dn = 170, 400, and 630, representing narrow, usual, and wide, respectively), to measure vegetation patch property influences. Flow velocity, scouring, and deposition characteristics under nine patches were determined by a hydraulic flume experiment, three-dimensional acoustic Doppler velocimetry (ADV), and three-dimensional laser scanner, and then ten geometry and morphology indices were measured and calculated based on the results of laser scanning. Results showed that both vegetation patch density and thickness were positively related to the turbulence kinetic energy (TKE) above the vegetation canopy, and only vegetation patch density was negatively related to the flow velocity above the vegetation canopy. The relation between the product of density and vegetation patch thickness and erosion area in planform (EA) showed a power function (R2 = 0.644). Both density and vegetation patch thickness determined the scouring degree, but deposition location and amount did not rely on each one simply. On average, medium density showed the smallest maximum erosion length (MEL), EA, deposition area in planform (DA), and average deposition length (ADL) and a minimum of the above parameters also occurred at narrow vegetation patch thickness. The shape factor of the erosion volume (SFEV), the shape factor of the deposition volume (SFDV), ADL, and MEL of medium density and narrow thickness vegetation patch (G/d = 1.3, dn = 170) were significantly smaller than that of other types of patches. DA and equivalent prismatic erosion depth on the erosion area (EPED) were significantly linearly related (R2 = 0.766). Consequently, most sediment was deposited close to the vegetation patch edge. It is suggested that vegetation patch thickness and density should be given to control sediment transport. In particular, natural vegetation growth changes vegetation patch density and then alters vegetation patch thickness. Management and repair need to be first considered. The results of this study shed light on riparian zone recovery and vegetation filter strip mechanism. [ABSTRACT FROM AUTHOR]

Soil erosion has become a serious ecological problem hindering the agricultural and economic development in Northeast China. Soil aggregates are basic units that regulate soil fertility and microbial activity. However, there have been few reports on the role of soil erosion in regulating the microbial diversity, multiple ecosystem services, and functions (multifunctionality) of soil aggregates. In this study, we investigated the effects of soil erosion on microbial diversity and the activities of various extracellular enzymes associated with soil aggregates by using Mollisol soil in Northeastern China at different positions of a slope, and how soil erosion affects soil multifunctionality indexes obtained by normalized calculation of soil enzyme activities. The results showed that soil erosion could reduce the physicochemical properties, soil enzyme activity, and microbial diversity of the aggregates, resulting in accumulation of aggregate nutrients and increase in microbial diversity and enzyme activity in the sedimentation area. Compared with smaller soil aggregates, larger soil aggregates had higher nutrient content, enzyme activity, and microbial diversity. However, with the intensification of soil erosion, the differences in microbial diversity and soil enzyme activities among different sizes of aggregates were reduced. Soil erosion also significantly reduced soil multifunctionality (p < 0.001). The multifunctionality of 2000–250 μm, 250–53 μm, and <53 μm aggregates respectively declined from 0.52, 0.20, and 0.08 (no erosion sites) to −0.17, −0.66, and −0.77 (heavy erosion sites). Additionally, microbial diversity was found to have a linear positive correlation with soil multifunctionality (R2 = 0.23, p < 0.01). Structural equation modeling and random forest analysis revealed that soil organic carbon and aggregate water stability are main predictors of soil multifunctionality. Furthermore, soil physicochemical properties had a greater influence on soil multifunctionality than microbial diversity. Collectively, our results demonstrate that soil erosion negatively affects the structure, resource effectiveness, and microbial activity of soil aggregates, thereby reducing to differential soil multifunctionality. [ABSTRACT FROM AUTHOR]

Gully erosion damages land resources and endangers human productivity and life, making it a key issue in global research on soil erosion nowadays. Gully headcut retreat (GHR) is the main form of gully erosion. Tiny concave features can be found in many retreating gully heads worldwide, and they are referred to as "niche terrain" in this study. To investigate the association between niche terrain and GHR, relevant research was reviewed on niches and stability analysis of gully heads with niches was modelled and analysed. Studies have shown that not all niches worldwide are identical due to regional differences in internal material–external environmental conditions. Special soil properties, joints, and cracks are the internal material conditions that lead to the formation of niche. External conditions include climate conditions, vegetation conditions, and topography. Water is the driving force for the formation of niche, while vegetation and topography are key factors. Niches can be regarded as the initial stage of GHR in areas where gully erosion is intense. In general, GHR is a composite cyclical process dominated by hydraulic erosion in the early stage and gravitational erosion in the late stage, including niche formation, inward concave formation, free face formation, overhanging soil collapse, and niche reformation. In this study, a model of gully head stability is applied, and it is found that the stability‐based factor of safety decreases exponentially with increasing niche height and crack depth, increases exponentially with increasing niche angle, and decreases quadratically with increasing catchment slope. Summarizing the common characteristics of niche terrains worldwide can facilitate the study of the evolution of gully erosion globally. [ABSTRACT FROM AUTHOR]