International Soil and Water Conservation Research最新文献

Based on “user pays” and “provider gets” principles, the Payment for Environmental Services (PES) consists of providing economic incentives or compensation for land users who adopt activities that promote ecosystem services. These PES initiatives have grown rapidly in Brazil over the last few decades, however, studies that address the panorama of these programs in the country are still scarce, regional, or outdated. Here, we investigate the PES overview in Brazil through interviews and an extensive literature review. We found in total 80 PES programs implemented in Brazil, of which 14 were closed. The programs are poorly distributed across the country, mostly concentrated in the Atlantic Forest (56.25%) and Savanna (36.25%) biomes, in Southeastern Brazil. The majority of programs primarily prioritize improving water quality and quantity. Therefore, reforestation, protection of native vegetation, and soil and water conservation are their main proposed practices. The positive impacts of Brazil's PES experiences are evident; while the lack of transparency and monitoring, and poor spatial and financial distribution are still major limitations. We conclude that if correctly implemented, PES schemes offer a path to reconcile environmental conservation with agricultural production in Brazil.

Rill erosion is affected by the sand particle content in soil, especially in the wind and water erosion transition region of the Loess Plateau. The sediment transport capacity (STC) is a key parameter in rill erosion research, assessing the impact of aeolian sand intrusion on the STC of rill flow is of importance for a better understanding of rill erosion. This study aimed to assess the effect of aeolian sand intrusion on the STC on sandified loess slopes, with typical slopes and flow discharges, using a flume system which consisting of a sediment-feeding and a sediment-supply/settlement flume. The sediment feeding flume was jointed by 10° higher than that of the sediment measurement flume section. Three flow discharges (2, 4, and 8 L min⁻¹) and four slope gradients (5°, 10°, 15°, and 25°) were used to represent the natural hydrological conditions under three intrusion rates (SIR) of aeolian sands (10%, 20%, and 50%). The results show that STC increased with slope gradient and flow discharge, and the relationship between the STC and the SIR was significantly affected by the slope gradient; the STCs decreased with the SIR on a slope of 5° but increased with the SIR on steep slopes of 15°–25°, implying a significant impact of slope gradient on the relationship between SIR and STC. The SIR of 50% resulted in the highest sediment concentration nearly 1200 kg m⁻³ on slopes of 25°. On sandified loess slopes of 10%, 20%, and 50% SIR, the STC were about 30%, 46%, and 57% higher than on loess slopes, indicating an increased erosion rate by sand particle intrusion into loess soil. These results highlight the impact of sand intrusion on STC of rill flow and provide deeper insights into the soil loss process on the sandified loess slope.

An accurate prediction of peak discharge in watersheds is critical not only for water resource management, but also for understanding the complex relationships of hydrological processes. In this study, a modified peak discharge formula based on the Chemicals, Runoff, and Erosion from Agricultural Management Systems (CREAMS) model was developed by introducing rainfall intensity and soil moisture factors. The reliability of the proposed method was tested with data from 1464 storm events in 41 watersheds and was applied to 256 storm events in five remaining typical watersheds using the optimized parameters. The results indicate that the proposed method is highly accurate in terms of model efficiency, as determined by Nash–Sutcliffe efficiencies (NSEs) of 88.60%, 74.04%, and 90.12% during the calibration, validation, and application cases, respectively. Furthermore, it performed better than the original and modified CREAMS methods. Subsequently, using the parameters derived from the initial 41 watersheds and the runoff estimated using the modified Soil Conservation Service curve number (SCS–CN) method, the proposed method was used to predict the peak discharge from the last five typical watersheds. Large NSE (63.88–80.83%) and low root mean square error (RMSE) values (0.31–35.93 m³s^-1) were obtained for the five watersheds. Overall, the proposed peak discharge model, combined with the modified SCS-CN method, may accurately predict event-based peak discharge and runoff for general applications under various hydrological and geomorphic conditions in the Loess Plateau region.

The Grain for Green Program and soil and water conservation engineering initiatives are crucial for controlling erosion in steep-slope agriculture. However, it is still unclear how these two management methods should be carried out in respect to the situation in mountainous areas. Therefore, taking a typical mountainous area in southwest China as an example, we simulated six scenarios in order to compare the food provisioning service (FPS) and soil conservation service of the Grain for Green Program (converting to grassland) and Construction Measures (converting to sloping terrace) under different slopes. Results showed that when farmland with a >25° slope was converted into grassland, the amount of soil erosion (M) decreased by 21.0%, while FPS decreased by only 0.7%. However, when farmland with a >25° slope was converted into sloping terrace, M decreased by 31.3% while FPS increased by 18.7%. With the increases of farmland slope ranges in the Construction Measures scenario, M gradually decreased and FPS gradually increased. Particularly when farmland >15° was converted into sloping terrace, M decreased by 63.9% and FPS increased by 52.7%. Furthermore, the trade-offs of Construction Measures are lower than that of Grain for Green on different slope ranges. Therefore, we conclude that Construction Measures are a more suitable method in mountainous areas than the Grain for Green, and we suggest that further research be conducted to consider the ecological risks of construction engineering measures.

Socioeconomic and environmental losses caused by water erosion have highlighted the importance of quantifying and understanding the dynamics of soil redistribution in the landscape to develop effective soil management practices. Several methods are applied to estimate erosion/deposition rates and identify sources of sediments, among them, the one that uses rare earth elements (REE) as a tracer stands out. However, an alternative not yet explored that can benefit the accuracy of the estimates provided by the method is using a tracer containing a chemical signature composed of more than one REE. The present study aimed to evaluate the performance of a new water erosion tracer based on montmorillonite labeled with rare earth elements (La40-MMT). The innovative aspects of this La40-MMT tracer include its highly stable multi-chemical signature (Nd³⁺, La³⁺, and Pr³⁺), which enhances tracer detection in the environment, and its low production cost due to the use of an industrial residue in the synthesis process. The tracer was evaluated for a typical soil of the Cerrado biome, using a natural rainfall field-scale plot - NRFP (5 m × 20 m) and a physical predictive erosion model (WEPP). The results showed that the La40-MMT tracer could be used to estimate erosion/deposition rates, with agreement between the values observed with the tracer and the WEPP model. Thus, this study confirmed the great potential of La40-MMT as a tool to identify patterns of soil redistribution at the field scale and aid in the validation of erosion models.

Rainfall simulators (RS) have been used, above all, to evaluate hydrological processes related to soil water infiltration, surface runoff and soil erosion. They allow repeatability of rain application with different precipitation intensities in field and/or laboratory conditions and should produce events with physical characteristics similar to natural rain. In this manuscript, we carried out a bibliometric and scientometric analysis of studies with simulated rainfall in Brazil to assess the temporal evolution of publications, the main topics addressed and the degree of technological development of the equipment. We searched for the terms “rainfall simulator” OR “simulated rainfall” AND “Brazil” in the Scopus, Web of Science, SciELO and Google Scholar databases. We found 143 articles published in the last 37 years (1985–2022). Our findings indicate that the main research areas covered in papers are soil erosion (57.34%), soil water infiltration (24.47%), nutrient losses (9.8%) and RS development and calibration/assessment (8.39%). In recent years, the number of published papers in international high-impact factor journals has increased. Most of the papers (49.65%) refer to studies carried out by institutions located in the south and southeast regions of Brazil. Moreover, there is a large gap of studies on simulated rainfall in other regions of Brazil, where important biomes such as the Cerrado, Amazon, Caatinga, and their transitions are located. This study informs research priorities on soil erosion under simulated rainfall and provides a bibliographic database that can assist in more detailed future analyses.

The dynamics of hydrological processes and the storage mechanisms of karst water resources are the most important issues in karst hydrology. The impact of environmental changes on water quantity, and the evaluation and quantification of eco-hydrological processes remain poorly addressed. In this study, high-frequency continuous monitoring in multi-scale karst watersheds in Southwest China combined the approaches of water isotopes and the hybrid single-particle lagrangian integrated trajectory (HYSPLIT) model to identify the recharge mechanisms between atmospheric vapor, rainfall, surface water, and groundwater, and to reveal the interaction of eco-hydrological processes. The dominant moisture sources in Puding (PD) County were the Indian Ocean (43–69%) and local moisture (24–33%). The δ¹⁸O and deuterium excess (d-excess) values showed a positive correlation indicating that secondary or sub-cloud evaporation was prominent in the wet seasons. Karst water line-conditioned excess (lc-excess) indicated that karst water interacted with recent precipitation, groundwater, and evaporation across seasons. Owing to its specific hydrogeological structure, surface water and rainwater have a higher contribution rate to groundwater replenishment. The Chenqi stream replenished the Houzhai River mainly in the form of groundwater, with percentages ranging from 38.1 to 93.5% in the wet season, and 47.8–80.1% in the dry season. In the Houzhai outlet, surface water and groundwater interconverted frequently with a percentage of 45.6–49.1%. We believe this is the first systematic study to quantify the supply relationship between water vapor transport, rainfall, surface water and groundwater in the Chinese karst zone, making a significant move forward in the field of karst hydrological processes and improving the efficiency of water resource evaluation and management.

Accurately quantifying rates of soil erosion requires capturing both the volumetric nature of the visible, convergent fluvial pathways (also known as rills) and the subtle nature of the less-visible, diffuse pathways (interrill areas). The aim of this study was to use Rare Earth Oxide (REO) tracers and Structure-from-Motion (SfM) photogrammetry to elucidate retrospective information about soil erosion rates and sediment sources during different soil erosion conditions, within a controlled laboratory environment. The experimental conditions created erosion events consistent with diffuse and convergent erosion processes. REO tracers allowed the sediment transport distances of over 2 m to be described, and helped resolved the relative contribution of diffuse and convergent soil erosion; interrill areas were also identified as a significant sediment sources soil loss under convergent erosion conditions. While the potential for SfM photogrammetry to resolve sub-millimetre elevations changes was demonstrated, under some conditions non-erosional changes in surface elevation, such as compaction, exceeded volumes of soil loss via diffuse erosion. The discrepancies between SfM Photogrammetry calculations and REO tagged sediment export were beneficial, identifying that during soil erosion events sediment in both aggregate and particle form is deposited within the convergent features, even when the rill extended the full length of the soil surface. The combination of SfM photogrammetry and REO tracers has provided a novel platform for building a spatial understanding of patterns of soil loss and source apportionment between rill and interrill erosion.

Regional soil erosion surveys are the first step of soil conservation planning. Grid and sampling approaches are commonly used for soil erosion surveys at the regional scale. With the grid approach, the region is divided into grids (e.g., 1 km × 1 km), and the soil erosion rate of each grid was calculated. With the sampling approach, a small portion of the area (typically 4% or less) was taken and then the soil erosion rate was calculated. Based on the above calculation, both approaches evaluated the soil erosion area (which is the area where the soil erosion rate is greater than the soil loss tolerance (t)) and its distribution in the whole region. The purpose of this paper is to compare the assessment results of the two approaches and analyse their practicality using Yunyang County, Chongqing, China (area is 3636 km²). The soil erosion rate, percentage of soil erosion area (PSEA, which is the ratio of the area where the soil erosion rate is greater than the soil loss tolerance (t) to the area of the total study region) and its spatial distribution were compared between the two approaches. The results showed that the grid approach overestimated the average soil erosion rate and PSEA overall for all 33 sample units and the whole region in comparison to the sampling approach. The sampling approach can yield a reasonable spatial distribution of the soil erosion rate in the whole region. In addition, the soil erosion regions were more clustered than those using the grid approach, which can be more suitable for soil conservation planning. Therefore, the sampling approach is an efficient and practical approach in regional soil erosion surveys. The results can provide insights into regional soil erosion surveys.