International Soil and Water Conservation Research最新文献

Saltwater intrusion along rivers is a complex process controlled by multiple factors and thus fluctuates with a highly nonlinear nature and time-varying characteristics. It is challenging to monitor saltwater intrusion. The objective of this study was to clarify the spatial-temporal variation of saltwater intrusion and its potential impact on agriculture in the Po River Delta (Italy). 2006 was the most severe year of saltwater intrusion in the period we considered. 2022 was even worse, but the data are still under processing. In this study, the Hilbert-Huang transform (HHT) and rescaled range (R/S) were used to identify the multi-time scales and change trends of the salinity and discharge in 2006. After that, the time-dependent intrinsic correlation (TDIC) was used to depict intrinsic relationships between salinity and discharge at different time scales. The results showed that discharge and salinity exhibited behaviours of positive long-range correlation during different periods. The temporal series of salinity and discharge was decomposed into six intrinsic mode functions (IMF) and residuals based on the ensemble empirical mode decomposition (EEMD). The sum of variance contribution rates of IMF1 (4 days), IMF2 (10 days), and IMF3 (12.1 days) of salinity was more than 75%. All measured TDICs have highlighted strong correlations between salinity and discharge. Furthermore, we used spatial interpolation techniques to map salinity data along rivers. This allowed the investigation of dynamic changes in saltwater intrusion patterns during periods of severe drought. Outcomes show a significant negative correlation between salinity and normalized difference vegetation index (NDVI), indicating that the study area's agricultural greening was affected by saltwater intrusion.

Much work has been done to understand and improve soil and water conservation where agriculture has driven land use intensification. Less is known about soil- and water-related impacts from intensification driven by solar farming, especially at watershed-scales. Here we employed Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS) to model Pond Creek, a rural watershed in Texas, USA. Land use is primarily crop cultivation and secondarily pasture for cattle grazing. Presently, several industrial-scale projects are planned to convert ≈15–30% of Pond Creek from agriculture to solar farms. The model was parameterized using public data sources and information from local stakeholders, then calibrated to several historical precipitation events. Experiments were conducted by varying precipitation depth, duration, and land uses: native vegetation pre-cultivation (control), cultivation (current), current conditions with 15% solar farm conversion (solar), and current conditions with 30% solar farm conversion (solar x2). Shifting to solar farming led to significant increases in cumulative sediment load (+12%–30%), with no significant differences in peak discharge rate changes (+0.38%–4%). Comparison to soil loss tolerance values showed current and solar treatment erosion rates exceeded tolerance values between 0.17 and 2.29 tons per hectare and all treatments were significantly different than the native treatment. We discuss high leverage strategies applicable to solar farm development sites as well as watersheds where they reside. Accelerating demand for land for renewable energy such as solar farming warrants greater attention from the soil and water conservation community to anticipate and mitigate impacts across landscapes.

The changes in the mechanical properties of collapsing walls under the influence of natural factors in the hilly area of southern China need to be determined. We systematically studied the influence of the interaction of dry density ρ (1.0, 1.1, 1.2, 1.3, 1.4 g/cm³) and moisture content ω (0.05, 0.1, 0.15, 0.2, 0.25 g/g) on the stability of four soil layers in a collapsing wall. The soil cohesion decreased with increasing soil depth. The cohesion force initially increased and then decreased with increasing ω and increased with increasing ρ; the internal friction angle was mainly affected by ω and decreased with increasing ω. The cohesion could be used to effectively characterize the stability of the collapsing wall. The shear strength index was modeled based on interaction between the dry density and moisture content (R² > 0.95). The optimal combination of moisture content and dry density was obtained, and the collapsing wall was in the most stable state at a moisture content of 0.12–0.19 g/g and a dry density of 1.40 g/cm³. Based on the analysis of the critical height and safety factor (FS), the FS values of the sandy layer (C) was 0.53 and 0.57 for ω values of 0.25 g/g and 0.05 g/g, respectively. In the alternating process of soil wetting and drying, the basic properties of the soil changed; caused traceback erosion, and thereby affected the stability of the collapsing wall. Our study provides a theoretical basis for the investigation of the factors influencing the stability of collapsing walls.

Soils are key natural resources for the Earth’s system; however, human impacts, especially, soil erosion are considered serious threats. Therefore, identifying and assessing effective factors to understand erosion hot spots at different scales is critical to developing effective land management plans and ensuring the sustainability of the territory. This study was conducted to determine and prepare an erosion risk map, but to prioritize the survey at different scales, such as sub-basin and watershed ones. To achieve this goal, geographic information system (GIS) and remote sensing data (RS) were used combining the analysis network process method (ANP) and ICONA model (Institute for the Conservation of Nature). As study case, we selected the degraded areas of the Gorganrood watershed located in the north of Iran. The study area was obtained for very low, low, medium, high, and very high-risk classifications of 14.0, 21.4, 17.9, 31.3, and 15.4%, respectively. Results from the ICONA model also indicated that 12.8, 28.8, 22.1, 27.9, 8.5, and 0.03% belong to very low, low, medium, high, very high, and without risk of erosion, respectively. According to the validation results, it was found that the accuracy of ANP and ICONA models are 0.83 and 0.80, respectively, which indicates the suitability of the models for preparing the erosion map of the region is appropriate and useful for designing land management plans. We conclude that both models can be used to develop the erosion map potential and to prioritize sub-basins if a complete database of geomorphological characteriscs and human activities are accurate previously defined.

Soil aggregate stability is an important index that reflects soil quality and anti-erosion ability and strongly affects soil processes and functions. Bedrock strata dips (dip and anti-dip slopes) and land use types primarily influence soil aggregate stability, whereas the detailed mechanisms are unclear in karst trough valley. Therefore, to explore the effects of bedrock strata dip and land use type on soil aggregate stability in karst trough valleys, soils were collected from five major land use types (abandoned land, grassland, pepper fields, corn fields and forest) on dip and anti-dip slopes. The soil was fractionated into macroaggregates and microaggrates using dry and wet sieving analysis. The soil particle size distributions in the macroaggregates and microaggregates were measured in conventional laboratories. The results showed significant differences in soil aggregate stability among different bedrock strata dips, slope positions, and land use types (P < 0.05). The variation ranges of macroaggregates and microaggregates in the pepper fields of the dip slope were higher than those on the anti-dip slope. Comparing all land use types, the forest of the anti-dip slope had >0.25 mm water-stable aggregates (85.31%) and mean weight diameter (2.67 mm) on the upper slope compared to that in the other slope positions of the dip slope. In addition, the dip slope had a higher percentage of aggregate destruction (35.57%) than the anti-dip slope (29.81%), and the soil erodibility factor value of the natural forest of the dip/anti-dip slope was significantly lower than that of the other land use types (P < 0.05). When the content of large macroaggregates was larger, the soil macroaggregate weight was greater. When the failure rate of the soil aggregates was lower, the stability of the soil structure was better. Overall, these results suggest that natural forests can significantly improve the stability of soil aggregates, thereby improving soil erosion resistance. Therefore, natural recovery measures should be implemented on dip/anti-dip slopes of karst trough valleys.

Geomorphic change detection (GCD) using high resolution topographic data can provide important insights into geomorphological systems. However, considerations must first be given to the mechanisms and dynamics producing landscape change when considering an appropriate experimental design. Khan et al. (2023) investigate gully erosion rates and processes in different untreated and rehabilitated gullies using multi-temporal aerial lidar survey (ALS) data. However, an inappropriate time interval between sampling, a lack of uncertainty measures and lack of baseline monitoring survey data lead them to arrive at incorrect conclusions. Additional data is presented from the same field sites, which demonstrate gully sediment losses have been underestimated by at least 330% and potentially over an order of magnitude. A number of critical shortcomiongs of the paper are outlined. Insufficient time intervals between data collection have led to a lack of detection of some sediment transport processes. Earthworks associated with gully rehabilitation have been conflated with geomorphic change, as no post-construction baseline data was collected. A lack of post-construction baseline data for this analysis means ongoing erosion and deposition cannot be resolved in the rehabilitated gully landscape. Given these errors in approach, discussions of gully geomorphic processes, erosion mechanisms and evaluations of rehabilitation efforts are unsupported, overstated and inaccurate. This has important implications for land management efforts and planning as well ongoing research on alluvial gully erosion, which is largely overlooked by Khan et al. (2023).

Rainfall variability coupled with poor land and water management is contributing to food insecurity in many sub-Saharan African countries such as Ethiopia. To address such challenges, various efforts have been implemented in Ethiopia. The objective of this study was to evaluate the long-term impacts of different soil and water conservation and water harvesting interventions on groundwater and drought resilience of the Gule watershed, northern Ethiopia. The study involved: (i) documentation of the approaches followed and the technologies implemented in Gule since the 1990s, (ii) monitoring the hydrological effects of the interventions for ten years, and (iii) evaluation of the effects of the interventions on groundwater (level and quality), spring discharge and suspended sediment concentration (SSC) in runoff. Results showed that interventions were implemented at different stages and scales. As a result of the interventions, the watershed was transformed into a landscape resilient to rainfall variability: (a) dry shallow groundwater wells have become productive and the level of water in wells has raised, (b) the groundwater quality has improved, (c) SSC in high floods has reduced by up to 65%, (d) discharge of existing springs has increased by up to 73% and new springs have started to emerge. Due to improved water availability, irrigated land has increased from less than 3.5 ha before 2002 to 166 ha in 2019. Communities have remained water-secure during an extreme drought in 2015/2016. Implementation of watershed management practices has transformed the landscape to be resilient to rainfall variability in a semi-arid environment: a lesson for adaptation to climate variability and change in similar environments.

In arid and semi-arid desert steppe areas, grazing exclusion with fencing is widely regarded as an effective strategy for restoring degraded vegetation and enhancing the quality of degraded soil. In this study, we hypothesized that grazing exclusion caused by fencing enhances both vegetation and soil properties, and that the longer an area is fenced, the more considerable the improvement. We conducted an observational study wherein random sampling was utilized to select 9 plots fenced for ten or more years, 25 plots fenced for four to nine years, 25 plots fenced for one to three years and 29 free-grazing plots within an area of approximately 63,000 km² of Inner Mongolia desert steppe. A one-way ANOVA revealed no significant differences in the characteristics of grassland vegetation or soil properties between grasslands fenced for one to three years and free-grazing grassland. After 4 years of fencing, noticeable increases in above-ground biomass, litter content, Simpson index, soil organic carbon, and available nitrogen were observed. Significant positive differences in vegetation coverage, height, species richness, soil available phosphorus, and available potassium were associated with plots with a minimum of 10 years of fencing. The soil layer with the greatest difference in the fenced-in areas for soil organic carbon was at 0–25 cm. For available nitrogen and available phosphorus, fencing produced the most significant differences in the 0–20 cm soil layer, while for available potassium, fencing produced the most significant differences in the 0–30 cm soil layer. However, the fencing did not indicate any statistically significant differences in terms of clay, silt, and sand content in any soil layer. The data support our hypothesis that grazing exclusion improves both vegetation and soil properties, and that longer periods of grazing exclusion result in greater degrees of improvement. This research offers technical guidance for the reasonable choice of fencing time across a vast area of the Inner Mongolian desert steppe.

Playas are common in many arid regions and recognized as a major source of hypersaline particles. A better understanding of wind erosion on crusted playas has significant implications for land management and pollution control practices. We hypothesized that wind erosion rates of crusted playas were complicated and controlled by the interactions between playa crust and wind-induced saltation conditions. However, comparisons regarding the effects of different playa crusts on wind erosion under no saltation (NS) and with saltation (WS) conditions were lacking. In this study, laboratory wind tunnel experiments were carried out to simulate both NS and WS conditions, to investigate the erosion rates of different crust types (Salt, Takyr, and Puffic crust) at different wind speeds. Results showed that: 1) Salt crust had greater crust strengths than did Takyr crust and Puffic crust; 2) wind erosion rates under the WS condition were up to 60 times greater than those under the NS condition, suggesting that sand bombardment was the dominant mechanism responsible for removal of fine material from crusted playa surfaces; 3) both sand bombardment rate and wind erosion rate of the playa crusts increased with increasing wind speed under the WS conditions; 4) Puffic crust exhibited a greater rate of wind erosion compared to both the Takyr and Salt crusts under the NS condition, yet tended to have a lower rate of wind erosion compared to both the Takyr and Salt crusts under the WS condition. This difference can be attributed to the fact that soft Puffic crusts are pliable and can dissipate the force of impacting grains under the WS conditions. Our results indicated that wind erosion processes on crusted playas are complicated and are affected by wind-induced saltation and crust type, specifically crust strength and elasticity of the surface.

Soil health depletion due to intensive tillage operations is a global issue in the agricultural sector. Conservation tillage (CT) which involves non-inversion tillage and leaving ∼30% of the soil surface covered with crop residues, is a strategy designed to enhance soil health. However, no comprehensive study to investigate the long-term effect of CT on soil biological activity and the soil nutrient supply has yet been widely carried out. Biological and chemical soil properties were assessed at depths 0–5, 10–15, and 20–25 cm depths after 18 years of CT and conventional tillage practice (PT). Various stages in the vegetative growth of maize were investigated in 2021 in Hungary. The findings indicated that tillage intensity, soil depth, and growth stages all significantly influenced soil enzyme activities and the concentration of soil nutrients. Less soil disturbance resulted in a significantly larger concentration of soil carbon parameters (total organic carbon and labile carbon) in CT plots, where the activity of β-glucosidase and dehydrogenase (DHA) in the upper soil layer increased significantly (0.7–2.6 and 2.6–4.7 times, respectively) compared to PT. The high amount of organic matter and the greater resistance to erosion observed in CT also contributed to the higher concentration of available nutrients (NH₄, NO₃, Ca, K) and total P in the surface soil layer. Phosphatase activity was highest in the mid-stage of vegetative growth and was positively correlated to the total P concentration. The alterations in soil water content were clearly negatively correlated with the change in DHA and phosphatase activity. Overall, due to the more balanced environmental conditions, the decomposition of organic substances was more balanced and slower in CT than in PT. This implied that the mobilization of nutrients in the soil was more balanced as well, and that the nutrients were released gradually. The enhancement of the soil nutrient-supplying capacity achieved by means of long-term conservation tillage provides a promising strategy for sustainable nutrient management.