Residue impacts on runoff and soil erosion for different corn plant populations

The year to year carry-over effects of biomass additions under different plant populations on runoff and erosion are unclear. The objective of this study was to quantify the impact of different plant populations on residue cover to elucidate the effects of residue cover on runoff and erosion. The residue management system involved shredding of corn (maize) biomass after harvest, incorporating the residue in the spring, and leaving the land fallow until it was no-till planted the following spring. Runoff and soil losses were measured on 18 runoff plots with plots arranged in two areas with each having three randomized treatments (0%, 50%, and 100% plant population) with three replications. The two areas were managed as a fallow/no-till corn rotation in two cycles of alternating years. Surface residue cover was highly dynamic with significant changes between cycles and seasons in response to the management practices. The annual soil losses were reduced by 47% and 54% for the 50% and 100% plant populations, respectively compared to the control. However, the annual soil loss even for the 100% plant population was still nearly seven times the tolerable soil loss limit of 7 ton ha⁻¹. The normal erosion protection afforded by no-till practices was lost by the incorporation of residue the previous year.     

The influence of vegetation species and plant properties on runoff and soil erosion: results from a rainfall simulation study in south east Spain

Abstract. To study the influence of different vegetation species and plant properties on the generation of surface runoff and soil erosion in south east Spain, a series of rainfall simulation experiments was conducted on small ( c . 1.5 m²) plots. These were carried out in October 1993 and May 1994 on two sites close to Murcia. Six vegetation types were studied, with some at different stages of maturity, giving a total of nine vegetation treatments and two bare soil treatments. Four replicates of each treatment were exposed to a rainstorm of 120 mm/h for 15 minutes. The results of the experiments show that there are few significant differences in the ability of the vegetation types studied to control runoff or soil erosion. Of the plant properties considered, only plant canopy cover showed a significant relationship with soil loss and runoff with the greatest reduction in soil loss taking place at canopy covers greater than 30%. The implications of this research are that future efforts should be directed at developing ecological successions and revegetation methods which promote a substantial and sustainable canopy cover.     

Effects of intra-storm variations in rainfall intensity on interrill runoff and erosion

Five simulated rainstorms, each with a different rainfall intensity pattern but all delivering the same total kinetic energy to the soil surface, were applied to three different soils in a laboratory flume. The storm patterns were: constant rainfall intensity, increasing intensity, decreasing intensity, increasing then decreasing intensity and decreasing then increasing intensity. The three soils were: a clay loam, a sandy loam and a sandy soil. No differences in total runoff were observed that were consistent across the three soil types. However, consistent differences were observed in the amount and size distribution of the eroded sediment. In particular, the constant-intensity storm yielded an average soil loss of 75% of the varying-intensity storms, and the eroded sediment from the constant-intensity storms had a lower clay content than that from the varying-intensity storms. In contrast to the differences in amount and size distribution of eroded sediment, splashed sediment exhibited much smaller differences. Interrill erosion rates are widely assumed to vary with rainfall intensity to the power 2, but this relationship has been obtained from experiments over a range of rainfall intensities, but in which rainfall intensity has been constant in each experiment. The experiments reported here, undertaken using variable rainfall intensity within each experiment, indicates an exponent of 2.55. The experiments demonstrate that the assumption that a given rainfall intensity falling on a given soil for a given amount of time will result in a given amount of runoff and erosion is unsound. They point to the need for a greater understanding of the processes of interrill sediment detachment and transport in order to model successfully erosion under temporally varying rainfall.     

Effect of water erosion and cultivation on the soil carbon stock in a semiarid area of South-East Spain

An experiment to evaluate the impact of water erosion and cultivation on the soil carbon dynamic and carbon stock in a semiarid area of South-East Spain was carried out. The study was performed under three different land use scenarios: (1) forest; (2) abandoned agricultural field; and (3) non-irrigated olive grove. Experimental erosion plots (in olive grove and forest) and sediment traps (in the abandoned area) were used to determine the carbon pools associated with sediments and runoff after each event occurring between September 2005 and November 2006.

Change in land use from forest to cultivated enhanced the risk of erosion (total soil loss in olive cropland seven-fold higher than in the forest area) and reduced the soil carbon stock (in the top 5 cm) by about 50%. Mineral-associated organic carbon (MOC) represented the main C pool in the three study areas although its contribution to soil organic carbon (SOC) was significantly higher in the disturbed areas (78.91 ± 1.81% and 77.29 ± 1.21% for abandoned and olive area, respectively) than in the forest area (66.05 ± 3.11%). In both, the olive and abandoned soils, the reduction in particulate organic carbon (POC) was proportionally greater than the decline in MOC.

The higher degree of sediment production in the olive cropland had an important consequence in terms of the carbon losses induced by erosion compared to the abandoned and forest plots. Thus, the total OC lost by erosion in the sediments was around three times higher in the cultivated (5.12 g C m⁻²) than the forest plot (1.77 g C m⁻²). The abandoned area displayed similar OC losses as a result of erosion as the forest plot (in the measurement period: 2.07 g C m⁻², 0.63 g C m⁻² and 0.65 g C m⁻² for olive, forest and abandoned area, respectively). MOC represented the highest percentage of contribution to total sediment OC for all the events analysed and in all uses being, in general these values higher in Olive (74–90%) than in the other two areas (55–80%). The organic carbon lost was basically linked to the solid phase in the three land uses, although the contribution of DOC to total carbon loss by erosion varied widely with each event.

Data from this study show that the more labile OC fraction (POC) lost in soil in the cultivated area was mainly due to the effect of cultivation (low overall biomass production and residue return together with high C mineralization) rather than to water erosion, given that the major part of the OC lost in sediments was in the form of MOC.     

Impact of climate change on soil erosion, runoff, and wheat productivity in central Oklahoma

The potential for global climate changes to increase the risk of soil erosion is clear, but the actual damage is not. The objectives of this study were to evaluate the potential impacts of climate change on soil erosion, surface runoff, and wheat productivity in central Oklahoma. Monthly projections were used from the Hadley Centre's general circulation model, HadCM3, using scenarios A2a, B2a, and GGa1 for the periods of 1950–1999 and 2070–2099. Projected changes in monthly precipitation and temperature distributions between the two periods were incorporated into daily weather series by means of a stochastic weather generator (CLIGEN) with its input parameters adjusted to each scenario. The Water Erosion Prediction Project (WEPP) model was run for four climate scenarios including a recent historical climate and three tillage systems (conventional tillage, conservation tillage, and no-till). HadCM3-projected mean annual precipitation during 2070–2099 at El Reno, Oklahoma decreased by 13.6%, 7.2%, and 6.2% for A2a, B2a, and GGa1, respectively; and mean annual temperature increased by 5.7, 4.0, and 4.7 °C, respectively. Predicted average annual soil loss in the tillage systems other than no-till, compared with historical climate (1950–1999), increased by 18–30% for A2a, remained similar for B2a, and increased by 67–82% for GGa1. Predicted soil loss in no-till did not increase in the three scenarios. Predicted mean annual runoff in all three tillage systems increased by 16–25% for A2a, remained similar for B2a, and increased by 6–19% for GGa1. The greater increases in soil loss and runoff in GGa1 were attributed to greater variability in monthly precipitation as projected by HadCM3. The increased variability led to increased frequency of large storms. Small changes in wheat yield, which ranged from a 5% decrease in B2a to a 5% increase in GGa1, were because the adverse effects of the temperature increase on winter wheat growth were largely offset by CO₂ rise as well as the bulky decrease in precipitation occurred outside the growing season. The overall results indicate that no-till and conservation tillage systems will be effective in combating soil erosion under projected climates in central Oklahoma.     

Natural and anthropogenic controls on soil erosion in the Internal Betic Cordillera (southeast Spain)

Soil erosion in southeast Spain is a complex process due to strong interactions between biophysical and human components. Significant progress has been achieved in the understanding of soil hydrological behavior, despite the fact that most investigations were focused on the experimental plot scale. Although experimental plots allow exploring the effect of multiple biophysical and anthropogenic factors, they provide limited insights in the combined effect of all factors acting together at the landscape scale. In this study, area-specific sediment yields (SSY) have been estimated based on the volume of sediment trapped behind 36 check dams in the southeast of Spain. Low SSY-values were reported (mean = 1.40 t ha⁻¹ year⁻¹: median = 0.61 t ha⁻¹ year⁻¹). SSY variability could be explained for 67% by catchment characteristics such as drainage area, soil characteristics, land cover, average catchment slope, and annual rainfall. The low SSY values are probably caused by the agricultural abandonment that occurred over the past decades and allowed the recovery of natural vegetation. Furthermore, our results suggest that the soils have eroded in the past to such an extent that nowadays not much sediment is detached by overland flow due to residual enrichment of clay and stones. Also, sediment is to a large extent trapped locally in the catchment, as indicated by the negative relationship between SSY and catchment area.     

Effects of zone-tillage in rotation with no-tillage on soil properties and crop yields in a semi-arid soil from central Spain

A limiting factor to the no-tillage system in arid and semi-arid regions is the possibility of soil densification from lack of tillage. This research examines the extent and duration of the effects of periodic (rotational) zone-tillage over 2 years, on selected soil physical and chemical properties and crop yields. In the first year four tillage treatments were applied: conventional tillage with mouldboard plow (CT), minimum tillage with chisel plow (MT), no-tillage (NT) and zone-tillage subsoiling with a paraplow (ZT). In the second year, the ZT plots were returned to NT to follow the residual effects of ZT. The soil was a loamy sand (Calcic Haploxeralf) from semi-arid Central Spain and the crop rotation was grey pea (Pisum sativum L.)–barley (Hordeum vulgare L.). Crop residues on the soil surface after sowing grey pea were 85% in NT plots, 55% in ZT plots and 15% in MT plots. When comparing NT and ZT, the immediate effects of subsoiling on soil physical properties were significant (P < 0.05). Soil strength as measured by cone index approached 3.0 MPa in NT and was reduced to <1.0 MPa by ZT over 300 mm sampling depth. Soil moisture content and bulk density were improved by ZT. No-till and ZT favoured surface accumulation of soil organic carbon (SOC), total N and available P and K. Stratification ratio of SOC was not different among tillage systems, but soil N stratification ratio followed the order NT > ZT > MT > CT. Grey pea yields were reduced by 3 Mg ha⁻¹ in the NT and MT compared with ZT. Crop residues on the soil surface after barley sowing were 80% in NT, 56% in ZT, and 12% in MT. At the end of the second year, soil strength, soil moisture and bulk density in ZT declined to NT levels at all soil depths. The positive effect of ZT in increasing SOC in the top layer had also disappeared. However, total N, and available P and K concentrations under NT and ZT were still significantly higher than in MT and CT. Stratification ratios of SOC under NT and ZT were >2 and more than two-fold those under MT and CT. Nitrogen stratification ratio under ZT increased and no significant differences between NT and ZT could be reported. Barley yield was 0.6 Mg ha⁻¹ higher in ZT compared with NT. Our results suggest that ZT improved the physical and chemical condition of the soil studied in months following subsoiling. These positive effects, however, diminished with time and only some residual effects on total N and available P and K content in the top-layer were still evident after 2 years.     

Climate change impacts on soil erosion in Midwest United States with changes in crop management

This study investigates potential changes in erosion rates in the Midwestern United States under climate change, including the adaptation of crop management to climate change. Previous studies of erosion under climate change have not taken into account farmer choices of crop rotations or planting dates, which will adjust to compensate for climate change. In this study, changes in management were assigned based on previous studies of crop yield, optimal planting date, and most profitable rotations under climate change in the Midwestern United States. Those studies predicted future shifts from maize and wheat to soybeans based on price and yield advantages to soybeans. In the results of our simulations, for 10 of 11 regions of the study area runoff increased from + 10% to + 310%, and soil loss increased from + 33% to + 274%, in 2040–2059 relative to 1990–1999. Soil loss changes were more variable compared to studies that did not take into account changes in management. Increased precipitation and decreasing cover from temperature-stressed maize were important factors in the results. The soil erosion model appeared to underestimate the impact of change in crop type, particularly to soybeans, meaning that erosion increases could be even higher than simulated. This research shows that future crop management changes due to climate and economics can affect the magnitude of erosional impacts beyond that which would be predicted from direct climate change alone. Prediction of future soil erosion can help in the management of valuable cropland and suggest the need for continually changing soil conservation strategies.     

The role of soil surface conditions in regulating runoff and erosion processes on a metamorphic hillslope (Southern Spain): Soil surface conditions,runoff and erosion in Southern Spain

This study presents the results of an analysis into the role of soil surface conditions in the regulation of soil hydrology and erosive processes at one hillslope under dry Mediterranean climatic conditions. The methodology was based on the analysis of hillslope surface components and their hydrological and erosive function on a patch to scale by means of rainfall simulation and experimental plots. The results showed the existence of a complex eco-geomorphological system composed of a multitude of vegetation patches distributed at random on the hillslope, and where the presence of different surface conditions on the soil can have a sizeable influence on hydrological and erosive behavior. From the hydrological point of view, the runoff generation mechanisms follow a seasonal pattern depending on the moisture of the soil with a different spatial condition, with frequent hydrological disconnections between parts of the hillslope, as in other Mediterranean mountainous regions. Soil surface rock fragments, the layout of tussocks intra-hillslope and previous soil moisture as dynamic control factors in the hydrological and erosive processes are all important.     

Effects of mulching on soil physical properties and runoff under semi-arid conditions in southern Spain

Application of crop residues to soil and reduced or no tillage are current management practices in order to achieve better water management, increase soil fertility, crop production and soil erosion control. This study was carried out to quantify the effect of wheat straw mulching in a no tilled Fluvisol under semi-arid conditions in SW Spain and to determine the optimum rate in terms of cost and soil protection. After a 3-years experiment, mulching application significantly improved physical and chemical properties of the studied soil with respect to control, and the intensity of changes was related to mulching rate. The organic matter content was generally increased, although no benefit was found beyond 10 Mg ha⁻¹ year⁻¹. Bulk density, porosity and aggregate stability were also improved with increasing mulching rates, which confirmed the interactions of these properties. Low mulching rates did not have a significant effect on water properties with respect to control, although the available water capacity increased greatly under high mulching rates. After simulated rainfall experiments (65 mm h⁻¹ intensity), it was found that the mulch layer contributed to increase the roughness and the interception of raindrops, delaying runoff generation and enhancing the infiltration of rain water during storms. Mulching contributed to a reduction in runoff generation and soil losses compared to bare soil, and negligible runoff flow or sediment yield were determined under just 5 Mg ha⁻¹ year⁻¹ mulching rate. It was observed that during simulations, the erosive response quickly decreases with time after prolonged storms (30 min) due to the exhaustion of available erodible particles. These results suggest that the erosive consequences of intermediate intensity 5-years-recurrent storms in the studied area could be strongly diminished by using just 5 Mg ha⁻¹ year⁻¹ mulching rates.     

Extent of soil erosion and surface runoff associated with large-scale infrastructure development in Fujian Province, China

We examined runoff and sediment transport associated with large-scale construction projects in Fujian Province, China. Six experimental plots, comprised of four plot types, were designed to mimic typical conditions immediately following disturbance. It was found that natural vegetative cover reduces both runoff and erosion by approximately 36 and 7457 times over bare ground, and 16 and 1801 times over typically planted grasses, respectively. The increase in erosion associated with the replacement of native vegetation with bare ground or grasses due to large-scale infrastructure projects in Fujian from 1999 to 2004, amounted to an estimated loss of 1.76 × 10⁷ tonnes of top soil and 3.04 × 10⁸ m³ of surface runoff from the province during the bare soil construction phase, and an additional 4.25 × 10⁶ tonnes of top soil and 1.35 × 10⁸ m³ of surface runoff from the province associated with the first year of operation for each project. This has implications for frequency and occurrence of landslides and other geographic hazards, the transport of chemicals into waterways, the transport of goods through shipping passages, and the fertility of land in Fujian.     

Soil quality attributes of conservation management regimes in a semi-arid region of south western Spain

Soil quality is essential for plant growth and terrestrial ecosystem maintenance. Although soil properties can be influenced by the agricultural production system, this influence has seldom been studied under semi-arid Mediterranean conditions. We analyzed the effect of the management system on soil physical and chemical parameters and soil microbial communities over three consecutive years under different conventional and conservation management regimes: conventional tillage (CT), direct seeding (DS), direct seeding with a winter crop cover (DSC), and long-term conservation management after nine consecutive years of direct seeding with winter cover (DSC^LT). The study was conducted on a maize (Zea mays L.) crop under irrigation in south western Spain. An improvement of the physical, chemical and biological parameters of the DS and DSC soils with respect to the CT soil was observed after two years management. Soil water content increased around 30% during the three years in the DS and DSC soils; organic C, nitrogen, and aggregate stability increased after the second year; total culturable microorganisms were twice as numerous in DSC^LT as in the CT soil; and soil penetration resistance was 50% less in all soils under any of the conservation management regimes. Hence, there was a major improvement in soil quality related to a potential increase of crop yields, and a reduced environmental impact, after short-term as well as after long-term conservation management.     

Surface runoff and soil erosion in a natural regeneration area of the Brazilian Cerrado

The Brazilian Cerrado has been converted to farmland, and there is little evidence that this expansion will decrease, mainly because agriculture is the country’s main economic sector. However, the impacts of intense modification of land use and land cover on surface runoff and soil erosion are still poorly understood in this region. Here, we assessed surface runoff and soil loss in a woodland Cerrado area under a former pasture area, which was abandoned and has undergone a natural regeneration process for 7 years (RC). Its results were compared with that found in an undisturbed area of woodland Cerrado (CE), 40-month-old eucalyptus (3.0 × 1.8 m) (EU), and pasture under rotational grazing (PA). The study was conducted on Red Acrisol located in the Brazilian Cerrado. We performed rainfall simulations on a plot of 0.7 m² and using three constant rainfall intensities of 60, 90, and 120 mm h⁻¹ for 1 h. For each rainfall intensity, we carried out four repetitions using different plots in each treatment, i.e. 12 plots per treatment studied and 48 plots in total. We noted that the soil physical properties were improved in RC and, consequently, water infiltration and soil erosion control; RC presented surface runoff and soil loss different from EU and PA (α = 0.05). The macroporosity and soil bulk density affected surface runoff in RC and PA because the RC was used as pasture and is currently regenerating back to the cerrado vegetation. As the rainfall intensity increased, EU became more similar to PA, which showed the highest surface runoff and soil loss. Our findings indicate that natural regeneration processes (pasture to the cerrado vegetation) tend to improve the soil ecosystem services, improving infiltration and reducing surface runoff and soil erosion.     

Water erosion risk assessment and impact on productivity of a Venezuelan soil

Soil losses affect the physical, chemical and biological soil properties and as a consequence reduce soil productivity. Erosion reduces or eliminates root-explorable soil depth and crop available water, selectively decreases the nutrient and organic matter content, and exposes soil layers with unsuitable characteristics for crop growth. Yield is hence assumed to be a function of root growth, which in turn is a function of the soil environment. In order to evaluate the water erosion impact on soil properties and productivity, a study was carried out on a Typic Haplustalfs soil, with sorghum (Sorghum bicolor (L) Moench), located in Chaguaramas in the Central Plains of Venezuela. Four different study locations with the same soil type, with slopes ranging from 3% to 6% and with different levels of erosion were selected: Chaguaramas I (slightly eroded), Chaguaramas II, (moderately eroded), Chaguaramas III (moderately eroded), and Chaguaramas IV (severely eroded). A sorghum–livestock farming system was introduced 30 years ago. Secondary tillage with a disc harrow (without mulch on the topsoil) was applied for seedbed preparation. Fertilizers and pesticides were applied uniformly over the entire fields. Soil samples from each horizon were analysed for particle size distribution, water retention, bulk density, pH and organic matter content. The relative production potential was estimated using the Productivity Index developed by Pierce et al. [Pierce, F.C., W.E. Larson, R.H. Dowdy and W.A. Graham. 1983. Productivity of soils: assessing long-term changes due to erosion. Journal of Soil and Water Conservation. 38 39–44.], and adapted to the methodology proposed by Delgado [Delgado F. 2003. Soil physical properties on Venezuelan steeplands: applications to conservation planning. The Abdus Salam International Centre for Theoretical Physics. College on Soil Physics. 11 pp.] for Venezuelan soil conditions. The Productivity Index (PI) could estimate the tolerable rate of soil productivity loss. A soil erosion risk was assessed by the Erosion Risk Index (ERI) taking into account the soil hydrological characteristics (infiltration–runoff ratio), rainfall aggressiveness and topography (slope). The Productivity Index (PI) and the Erosion Risk Index (ERI) were used to classify the lands for soil conservation priorities, for conservation requirements and for alternative land uses. The results showed that: (a) the Productivity Index (PI) decreased with increasing level of erosion, (b) the Productivity Index (PI) was mainly affected by changes in available water storage capacity, bulk density and pH, (c) the erosion risk (ERI) was strongly affected by slope gradient and rainfall aggressiveness, (d) the areas were classified as critical lands and super-critical lands, with high to very high soil conservation requirements, depending on the level of soil erosion.     

Seasonal variability of runoff and soil loss on forest road backslopes under simulated rainfall

Runoff and soil loss from forest road backslopes is a serious problem in Mediterranean areas. Surface runoff and sediment production on backslopes of forest roads in Los Alcornocales Natural Park (southern Spain) has been studied in this paper using a simple portable rainfall simulator at an intensity of 90 mm h^− 1. One hundred rainfall simulations were performed on bare and vegetated road backslopes during summer and winter in order to study seasonal differences. Runoff coefficients and soil loss rates were lower on the vegetated plots than on the bare ones. Runoff coefficients increased 1.7 (bare backslopes) and 3.1 times (vegetated backslopes) from summer to winter. Preserving the vegetation cover over 20% is recommended for keeping soil loss rates under low levels, especially during winter.     

神府煤田土壤颗粒分形及降雨对径流产沙的影响

神府煤田在开发建设过程中造成的扰动地面、弃土体、弃渣体产生了严重的人为水土流失。采用野外人工模拟降雨试验方法,研究了土壤分形维数及降雨强度对未扰动地面、扰动地面、弃土体及弃渣体径流产沙的影响。结果表明,(1)弃土体、弃渣体随产流历时呈现突增—下降—稳定的过程,扰动地面和未扰动地面则经历上升—稳定的产流过程,各下垫面径流率均随着雨强的增大而增大。(2)各下垫面土壤颗粒分形维数的大小为D1(弃渣体)D2(弃土体)D3(扰动地面)D4(未扰动地面),次降雨径流量与降雨强度、分形维数分别呈显著的线性、幂函数关系,且D1~D2及D3~D4之间存在用以区分下垫面类型的临界分形维数值。(3)弃渣体侵蚀过程线呈先波动后稳定趋势,弃土体则呈多峰多谷特点,扰动地面和未扰动地面在1.0~2.5 mm min-1雨强下侵蚀速率均先增大后逐渐稳定,3.0 mm min-1时二者侵蚀速率则波动剧烈。四种下垫面平均侵蚀速率均随着雨强的增大而增大。(4)次降雨产沙量与降雨强度、分形维数均呈显著的幂函数关系。(5)径流量、产沙量与雨强和分形维数分别呈显著的线性、指数函数关系。分形维数对矿区土壤侵蚀模型的建立有重要的科学意义。     

The impact of vegetative cover type on runoff and soil erosion under different land uses

The effects of different vegetation types on runoff generation and soil erosion were investigated. The study was conducted at the Southern part of West Bank, about 10 Km north-west of Hebron city, during 2005, 2006 and 2007. Five treatments were implemented; forests planted with P. halepensis (F), natural vegetation dominated by S. spinosum (W.S), natural vegetation where S. spinosum was removed (W/o.S), cultivated land (C), and deforestation (Df). Three types of data were estimated in each plot: runoff after each rainfall event, sedimentation at the end of the rainy season, and chemical and physical soil properties. The obtained results indicate that there are significant and important differences in runoff generation and sediment production with respect to the different types of vegetative cover. Forest and natural vegetation dominated by S. spinosum treatments exhibited the lowest amounts of runoff, with averages of 2.02 and 1.08 mm, respectively, in comparison to other treatments. The removal of S. spinosum significantly increased the total amount of runoff and sedimentation compared to the forest and S. spinosum treatments. In addition, runoff significantly increased (4.03 mm) for the Df treatment compared to that of the forest site. The greatest amount of sedimentation was observed in cultivated land and with deforestation.     

Effects of vegetation restoration on soil organic carbon sequestration at multiple scales in semi-arid Loess Plateau,China

Soil organic carbon (SOC) sequestration by vegetation restoration is the theme of much current research. Since 1999, the program of “Grain for Green”has been implemented in the semi-arid Loess Plateau, China. Its scope represents the largest vegetation restoration activity in China. However, it is still unclear for the SOC sequestration effects of vegetation cover change or natural succession promoted by the revegetation efforts at different scales under the semi-arid conditions. In this study, the changes in SOC stocks due to the vegetation restoration in the middle of Loess Plateau were estimated at patch, hill slope transect and small watershed scale from 1998 to 2006. Soil samples were taken from field for the determination of cesium-137 (¹³⁷Cs) and SOC contents. Vegetation cover change from 1998 to 2006 at the small watershed scale was assessed using Geographic Information System. The results showed that cropland transforming to grassland or shrubland significantly increased SOC at patch scale. Immature woodland, however, has no significant effect. When vegetation cover has no transformation for mature woodland (25 years old), SOC has no significant increase implying that SOC has come to a stable level. At hill slope scale, three typical vegetation cover patterns showed different SOC sequestration effects of 8.6%, 24.6%, and 21.4% from 1998 to 2006, and these SOC increases mainly resulted from revegetation. At the small watershed scale, SOC stocks increased by 19% in the surface soil layer at 0–20 cm soil depth from 1998 to 2006, which was equivalent to an average SOC sequestration rate of 19.92 t C y^− 1 km^− 2. Meanwhile, SOC contents showed a significant positive correlation (P < 0.001) with the ¹³⁷Cs inventory at every soil depth interval. This implied significant negative impacts of soil erosion on SOC sequestration. The results have demonstrated general positive effects of vegetation restoration on SOC sequestration at multiple scales. However, soil erosion under rugged topography modified the spatial distribution of the SOC sequestration effects. Therefore, vegetation restoration was proved to be a significant carbon sink, whereas, erosion could be a carbon source in high erosion sensitive regions. This research can contribute to the performance assessment of ecological rehabilitation projects such as “Grain to Green” and the scientific understanding of the impacts of vegetation restoration and soil erosion on soil carbon dynamics in semi-arid environments.     

Assessment of soil erosion on arable land using Cs measurements: a case study from Jaslovske Bohunice, Slovakia

This study was carried out to obtain a representative set of data on long-term erosion rates from a pilot area located close to the Jaslovske Bohunice village, in western Slovakia using the ¹³⁷Cs-method. The study area chosen was representative of the hilly loess cultivated areas of Slovakia. The sampling strategy was based on a multiple transect approach. Analyses of the samples for ¹³⁷Cs activity were made at the Nuclear Power Plant Research Institute, Jaslovske Bohunice. The ¹³⁷Cs-method was used to obtain long-term estimates of soil erosion in the Jaslovske Bohunice site, a representative hilly loess cultivated area of Slovakia. The estimated reference ¹³⁷Cs inventory was 2910 Bq m⁻², with a coefficient of variation of 4.3%.Examination of the ¹³⁷Cs redistribution in relation to the topography of the study area revealed that, within individual transects the ¹³⁷Cs inventories were closely related to major landforms. The ¹³⁷Cs inventories were considerably lower on the slopes than on the plateau and they were highest in the valley. However, when plotted against a selection of individual quantitative slope parameters, i.e. the S and the LS factors of the USLE or slope inclination, the correlations obtained were weak.Three conversion models, i.e. the proportional model (PM), the simplified mass balance model (MBM1) and the standard mass balance model (MBM2), from the set of models developed at Exeter University, Great Britain were selected to interpret the resulting ¹³⁷Cs measurements into soil erosion/deposition rates. The mean erosion rates estimated with the PM were 22.4, 35.6 with MBM1 and 17.3 t ha⁻¹ per year with MBM2. There was a good agreement between the average of these mean erosion rates (25.1 t ha⁻¹ per year) for the Jaslovske Bohunice site and the estimated mean soil erosion rate obtained for small erosion plots (15 t ha⁻¹ per year) for conditions similar to the study site. Nevertheless, further research on the application of the ¹³⁷Cs-method, in particular the independent validation of the results obtained, is needed. Several issues requiring further study have been highlighted.     

Climate change and soil erosion on agricultural land in england and wales

To assess the effects of climate change on soil erosion we need to model changes in rate, frequency and extent of erosion. Present day rates of soil erosion for agricultural land in England and Wales are known from a national monitoring scheme and also from a local one. The latter, for the South Downs, covers a seven-year period and includes climatic data. This shows a strong correlation between total erosion and a Rainfall Index. The availability of these databases allows us to use existing models such as EPIC and an Expert System to predict erosion rates for postulated warmer and wetter (winter) conditions. EPIC is particularly suitable for specific sites where detailed data exists and crop yield implications can also be modelled. A rule-based Expert System approach allows us to examine erosion rates at a different scale across the landscape. We postulate that water erosion rates on arable land in the lowlands will increase markedly in severity, frequency and extent especially if land use changes. In the uplands predicted climatic warming suggests a longer growing season and fewer frosts: these may lead to a decrease in erosion of overgrazed eroding slopes. Increases in erosion rates are not inevitable if policy decisions are taken and implemented in good time.