喀斯特坡地侵蚀性降雨阈值初探

喀斯特坡地表层岩溶带发育，入渗强烈，产流机制与非喀斯特坡地有较大差异，为提高喀斯特坡地土壤流失模型预测准确性，以贵州省普定县陈旗小流域6个不同土地利用类型径流小区为观测对象，分析2007—2010年、2015—2019年2期泥沙和地表径流数据，了解产流产沙规律，并利用降雨侵蚀力偏差法计算各小区侵蚀性降雨量。结果表明：(1)植被覆盖率与喀斯特坡地地表产流产沙量呈负相关，高植被覆盖下，暴雨和极端暴雨是造成喀斯特坡地水土流失的主要降雨事件；(2)植被恢复十余年随着覆盖度的提高，年均土壤流失量呈显著下降趋势，多小于10 t/km²;(3)喀斯特坡地裂隙发育，地下漏失严重，土壤量少且不易被侵蚀，除少数极端暴雨外，多数降雨不产流不产沙，因此建议将喀斯特坡地侵蚀性降雨量阈值定为50 mm,该阈值显著高于非喀斯特地区。     

Effect of rainfall intensity and slope steepness on the development of soil erosion in the Southern Cis-Ural region (A model experiment)

The effect of rainfall intensity on the erosion of residual calcareous agrogray soils and clay-illuvial agrochernozems in the Southern Cis-Ural region on slopes of different inclination and vegetation type has been studied by simulating with a small-size sprinkler. It has been shown that soil loss linearly depends on rainfall intensity (2, 4, and 6 mm/min) and slope inclination (3° and 7°). When the rainfall intensity and duration, and the slope inclination increase, soil loss by erosion from agrogray soils increases higher than from agrochernozems. On the plowland with a slope of 3°, runoff begins 12, 10, and 5 min, on the average, after the beginning of rains at these intensities. When the slope increases to 7°, runoff begins earlier by 7, 6, and 4 min, respectively. After the beginning of runoff and with its increase by 1 mm, the soil loss from slopes of 3° and 7° reaches 4.2 and 25.7 t/ha on agrogray soils and 1.4 and 4.7 t/ha on agrochernozems, respectively. Fallow soils have higher erosion resistance, and the soil loss little depends on the slope gradient: it gradually increases to 0.3–1.0 t/ha per 1 mm of runoff with increasing rainfall intensity and duration. The content of physical clay in eroded material is higher than in the original soils. Fine fractions prevail in this material, which increases their humus content. The increase in rainfall intensity and duration to 4 and 6 mm/min results in the entrapment of coarse silt and sand by runoff.     

黄土丘陵区不同土地利用方式降雨产流试验研究

在延安燕沟试验区建立草地、刈割草地、翻耕草地、灌木地、刈割灌木地、翻耕灌木地径流小区,通过对30场人工模拟降雨产流试验中产流历时、径流强度、径流深、入渗率数据的分析,得出草灌地产流历时远大于翻耕地和刈割地。翻耕灌木地径流强度及波动幅度最大,为翻耕草地的1.5倍、草地的3.4倍、灌木地的15.7倍。在各次降雨过程中,草地平均径流深、入渗率分别为17.1 mm和75%,刈割草地为25.3 mm和62%,翻耕草地为38.4 mm和35.6%,灌木地为3.2 mm和97%,刈割灌木地为5.6 mm和92%,翻耕灌木地为46 mm和35%。研究结果表明,植被能有效地拦蓄径流,而对草灌地的破坏可引发黄土丘陵区严重的水土流失。     

The effects of dairy cow weight on selected soil physical properties indicative of compaction

The effect of treading by dairy cows of three different weights on soil physical properties was investigated under different soil moisture deficit (SMD) treatments in the south of Ireland. SMD was used as a readily predicable surrogate for volumetric water content. Animal treading in grassland ecosystems is known to affect soil and vegetation properties, which can influence agricultural system productivity. Treading action can result in reduced soil water infiltration and increased runoff. In Ireland short winter housing and early spring turnout are key elements of low cost grass based production. However, there is potential for soil damage as a consequence of animal treading during early spring and late autumn. This study shows that SMD is the main factor affecting changes in bulk density (BD), soil shear strength, penetration resistance (PR) and total porosity. At high SMD (dry), soil was less sensitive to trampling damage than at low SMD (wet). At SMD 0 mm, BD increased by 6.1% post trampling, whereas it only increased by 3.1, 4.0 and 0.5% at SMD 11, 14, and 29 mm, respectively. Average soil BD was 2.3% greater immediately post trampling, and 4.6% greater in the hoof marks. PR was significantly greater following trampling by the heavy weight cow compared with the light or medium weight cow. There was no significant effect of cow weight on soil water content or soil BD. The results indicate that forecasted SMD can be used as a management input for rotational grazing systems to protect soil quality.     

Soil crusting and infiltration on steep slopes in northern Thailand

Predicting the rate at which rain infiltrates on steep slopes is very uncertain. There is no consistent information in the literature. We have therefore related infiltrability to slope gradient under field conditions by experimenting on a gravelly loamy soil occupying the upper half of a cultivated convex hill in northern Thailand. Fifteen 1 m × 1 m plots with slope gradients ranging from 16 to 63% were established, and simulated rain was allowed to fall on them at controlled rates and for fixed times. We obtained the following results. The surface fell 0.4–7.2 mm due to compaction and soil loss. The proportions of crust (0–40%) and embedded gravel (10–60%), the runoff coefficient (0.05–0.78 mm mm^?1), the mean sediment concentrations (0–5.6 g l^?1), and soil detachment (10–313 g m^?2) were more pronounced on the gentle slopes than on the steep ones. The steady final infiltration rate (1–107 mm hour^?1) increased sharply with increasing slope gradient. Microaggregates tended to behave like sand and become tightly packed on gentle slopes (packing crust). These results suggest that the vertical component of kinetic energy, which is greater on gentle slopes, has a dominant role. Nevertheless, the differences in compaction and in sediment concentration could not be ascribed to the vertical component of kinetic energy alone. On steep slopes the horizontal component of the kinetic energy is transformed into shear stress, hampering the development of crusts so that water can still infiltrate. On steeper slopes, the water film was thinner, thereby limiting the role of splash. We conclude that the relationship between slope gradient and infiltrability depends on the nature of the soil and must be examined in the light of surface crusting processes.     

Soil erosion on alfisols in Western Nigeria: I. Effects of slope,crop rotation and residue management

The effect of slope, crop rotation and residue management on runoff and soil loss was investigated using field runoff plots of 25 m × 4 m on natural slopes of 1, 5, 10 and 15% on an Alfisol on the International Institute of Tropical Agriculture (IITA) research site near Ibadan, Nigeria. The soil and crop management treatments consisted of conventionnally plowed bare fallow, maize-maize (conventionally plowed and mulched), maize-maize (conventionally plowed), maize-cowpeas (zero-tillage), and cowpeas-maize (conventionally plowed). The effect of two contour lengths of 12.5 and 37.5 m was also investigated for the maize-cowpeas rotation.Soil erosion under slopes of 5, 10 and 15% is severe for these soils and if not controlled can limit crop growth.Mulching and no-till treatments had negligible runoff and soil loss. During 1973 the annual runoff losses from the 15% slope were 36, 2 and 2% of the total annual rainfall for the bare-fallow, mulched and no-till treatments, respectively. Annual soil losses during 1973 from the 15% slope were 230 t/ha from bare-fallow, 0.0 t/ha from maize-maize (mulched), 41 t/ha from maize-maize (conventional plowing), 0.1 t/ha from maize-cowpeas (no-till) and 43 t/ha from cowpeas-maize (plowed). Significant soil erosion was associated with only a few extremely intense storms. The soil loss during a single rainstorm increased exponentially with an increase in slope gradient. There was no definite relationship between contour length and runoff or soil loss.     

Moderate sheep grazing in semiarid shrubland alters small-scale soil surface structure and patch properties

We investigated whether long-term moderate livestock grazing by sheep (ca. 10 animal unit days/ha) in a semiarid shrubland with a long-term average annual rainfall of 200 mm causes changes in soil surface structure and dimensions of shrub and intershrub patches. We examined grazing-induced changes in landscape patchiness, patch structure, and soil moisture in three grazed and three ungrazed plots of 4 m × 4 m on a south-facing slope and the opposite, more productive north-facing slope. The measurements were done in early spring 2001 and 2002 before grazing started, in two surveys, one using two parallel transects and one using sample quadrats of 20 cm × 30 cm under three shrubs per plot and on an adjacent part of the intershrub matrix. On the north-facing slope, the sheep reduced shrub patch size as they trampled the soil mounds under the shrubs and browsed the shrub canopy. Reduced shrub patch size decreases the area and resources available for plant production. On the south-facing slope, the sheep mainly disrupted the soil crust in the intershrub area. This may increase soil erosion, but also seedling establishment. The contrast in impacts on the two slopes is due to the interaction between environment (productivity, exposure and vegetation) and sheep behavior (herbivory and trampling). On both slopes, the changes due to grazing are significant, though small. Changes in patch size and properties induced by moderate grazing can have positive and negative effects on productivity and diversity, but may also be viewed as early signs of landscape degradation as is often caused by heavy grazing.     

Soil erosion on Alfisols in Western Nigeria: II. Effects of mulch rates

The effects of four rates of straw mulching on runoff and soil loss were compared with those of no-tillage treatments under natural rainfall conditions using field runoff plots of 25 × 4 m established at 1, 5, 10 and 15% slopes on the International Institute of Tropical Agriculture (IITA) research site near Ibadan, Nigeria. The four rates of straw mulching were 0, 2, 4 and 6 t/ha. The mean annual runoff was 50, 10, 4 and 2% of the total annual rainfall for mulch rates of 0, 2, 4 and 6 t/ha, respectively. Runoff from unmulched treatments was not related to slope. Runoff loss from no-till treatments was only 2% of the rain received. The mean soil losses for the rainstorms greater than 25 mm were 143, 16, 2 and 0.4 kg/ha per mm of rain received for mulched rates of 0, 2, 4 and 6 t/ha, respectively. The soil loss declined exponentially with increasing mulch rate with exponents ranging from approximately ?0.3 to ?0.7. The soil losses from the no-till plots were equal to those from plots that received mulch at the rate of 6 t/ha. Soil erodibility was significantly influenced by time after clearing, with maximum K reached two to three years after forest removal. The nutrient loss in runoff and eroded soil was significant only for unmulched treatments. The maximum annual loss of NO₃-N in runoff was about 15 kg/ha. The maximum annual loss of total N in eroded soil from unmulched plots was about 180 kg/ha, that of P, 5 kg/ha, and that of K, about 14 kg/ha.     

Effect of trampling on the soils of the St James Walkway, New Zealand

Abstract. The influence of trampling on the soils of the St James Walkway was studied during 1985 by comparing 'on'- and off-track sites. Trampling increased the average soil bulk density by 0.3 g/cm³ at 0–5 cm depth and by 0.1 g/cm³ at 10–15 cm depth. Trampling increased the average soil shear strength by 11 kPa at 0–5 cm depth and by 6 kPa at 5–10 cm depth. All mineral soils were compacted to some extent by trampling. The podzolized high country yellow-brown earths (Dystrochrepts) were the most affected because their organic topsoil was truncated. Their exposed subsoil was however more resistant to further damage than their topsoil. Organic soils (Medihemists) were not compacted but their very low shear strength and high moisture content make them unsuitable for tracks. Untrampled soil bulk density and soil stone content were negatively correlated with the change in bulk density by trampling, and could be used to predict the risk of soil compaction by trampling.     

Influence of deer exclusion on soil nutrients in oak forests of a central European low mountain range

High densities of red deer can have severe impacts on soil nutrient status by removing the ground vegetation and enhancing erosion of the fertile soil layers. We compared four fenced deer exclosures with adjacent unfenced sites to evaluate the effect of deer grazing and trampling on the soil nutrient status (C_org, N_t, PO₄³⁻, Ca²⁺, Mg²⁺, K⁺) in sloping oak forests of a central European low mountain range. The investigation was set up as a three‐factor randomized complete block design (RCBD) with the factors: ‘fencing’ (fenced/unfenced), ‘gradient’ (gentle/steep) and ‘aspect’ (windward/leeward). We hypothesized that exclusion of red deer by fencing would increase soil nutrient contents independent of slope gradient and aspect. Fencing increased the contents of C_org, N_t, Ca²⁺ and PO₄³⁻, but only at the windward sites. This effect was less pronounced at the gently sloping site than at the steep site, which exhibited the lowest contents of C_org, N_t and PO₄³⁻ of all sites. We did not find increased soil nutrients in the fenced exclosures at the leeward sites, neither at the steep nor at the gently sloping site. At both slope aspects nutrient contents (C_org, N_t, PO₄³⁻, K⁺) tended to be higher on the gentle than at the corresponding steep slopes. Our results suggest that red deer trampling and grazing enhance the loss of soil nutrients at predisposed sites such as windward locations with a high slope gradient. Only at such sites did the exclusion of red deer increase several soil nutrients. Copyright © 2005 John Wiley & Sons, Ltd.     

The effect of slope on interrill erosion at short slopes

Slope gradient is an important factor that affects soil erosion. This study was conducted to investigate the effect of slope gradient on soil erosion and determine the splash contribution to interrill erosion at short steep slopes. An experimental device was used to make simultaneous measurements of interrill splash and wash at 9, 18, 27, 36, 47, 58, 70, 84, and 100% slopes under a constant rainfall intensity of 67 mm h^? 1 in a laboratory setting. The specially designed runoff and sediment collection system provided a means of partitioning total splash into four directional components and interrill sediment transport into wash and splash components. The results revealed that the total splash loss, net downslope splash loss and wash loss all increased with slope, and then decreased after a maximum value was reached. The slope factor equation of short slopes in RUSLE matched the wash loss from this study very well when the slope gradient was less than or equal to 58%. The ratio of net downslope splash loss to wash loss increased from 0.21 to 1.33 as the slope gradient increased from 9% to 100%. Taken together, these results indicate that upslope splash loss was a very important component of the total splash loss on gentle slopes and may be neglected on slopes greater than 36%. Splash transport was a significant part of interrill sediment delivery at short steep slopes.     

Influence of soil surface features and vegetation on runoff and erosion in the Western Sierra Madre (Durango,Northwest Mexico)

In mountainous areas, runoff and soil erosion are closely linked to soil surface features, particularly stoniness. Depending on the size of rock fragments (gravel, pebbles, stones and/or blocks) and especially the way they are integrated into the soil matrix, they may facilitate or hinder infiltration and promote soil losses. The present study examines the role of different soil surface features and their influence on runoff formation and on soil erosion in an area seriously affected by overgrazing.Based on measurements made on hillslopes for 2 years at the plot scale, the results show that grass cover, pebbles and sand content increase runoff and erosion. Inversely, slope value, tree cover percentage, structural stability and organic matter content are negatively correlated with runoff and soil losses.It is shown that the correlations can be explained by the major role played by the surface features on hydrologic behaviour of the hillslopes. Two main surface features were identified and hydraulically characterised, namely: (i) crusted surfaces with embedded gravel widespread on gentle slopes which induce high runoff and erosion rates; and (ii) stony surfaces, where free pebbles and blocks protect the top soil against raindrops and overland flow kinetic energy and lead to reduce runoff and soil losses.     

丘陵半干旱区小流域入渗产流特征研究

为了探索我国丘陵半干旱区小流域入渗产流规律,为该地区雨水径流集蓄利用和区域生态环境治理提供依据,通过人工模拟降雨和自然降雨入渗产流试验,对小流域坡耕地、林地、草地和荒地的降雨入渗产流特征进行了系统研究。结果表明,农林草地比荒地具有明显的拦蓄地表径流和减少土壤侵蚀的效果,比荒地拦蓄地表径流效率增加35.7?.0%,拦蓄泥沙效率增加46.2?.6%;利用Philip入渗理论和逐步回归分析方法对入渗产流试验结果处理分析,建立了小流域坡耕地、林地和荒地土壤的入渗产流及其相关因子数学模型;小流域产流系数与降雨小区地形坡度、降雨强度、植被盖度、土壤雨前含水量和土壤孔隙度等因子显著相关。     

The long-term effect of tillage on soil displacement of hilly areas used for growing wheat in Greece

Abstract. Tillage displaces large amounts of soil from upper slopes and deposits soil in lower landscape positions, greatly affecting productivity in these areas. The long-term effect of tillage on soil erosion was studied in four field sites growing mainly rainfed wheat. The soil loss from landscape positions with slopes, ranging from 3 to 28%, was estimated by: (a) comparing data of horizon thickness described at the same position at different times; and (b) using soil movement tracers added to the soil. Existing empirical relationships were used for estimating soil loss by tillage and runoff water, and loss in wheat biomass production. The experimental data showed soil losses of 0.4 to 1.4 cm yr^–1 depending on slope gradient, plough depth, and tillage direction. In two of the sites, soil depth has been reduced by 24–30 cm in a period of 63 years. The mean soil displacement of the plough layer (30 cm thick), measured by soil movement tracers, ranged from 31 to 95 cm yr^–1 depending mainly on slope gradient, corresponding to a rate of soil loss of 0.3 cm to 1.4 cm yr^–1. Soil eroded from the upper slopes was deposited on the lower slopes increasing soil thickness by 0.4 cm to 1.4 cm yr^–1. The application of empirical relationships, estimating soil loss by tillage and water runoff, showed that soil erosion at the field sites can be mainly attributed to tillage. The loss in wheat biomass production due to erosion was estimated at 26% on upper slopes for a period of 63 years, while a 14.5% increase in wheat production was estimated due to deposition of soil material in the lower landscape.     

Soil erosion on Alfisols in Western Nigeria: IV. Nutrient element losses in runoff and eroded sediments

Nutrient element losses in runoff and eroded sediments were monitored during 1972 on different slopes and under different soil and crop management treatments. The experiments were conducted on 25 × 4 m field runoff plots, established on natural slopes of 1, 5, 10 and 15%. The soil and crop management treatments consisted of bare fallow (plowed), maize-maize (plowed and mulched), maize-maize (plowed), maize-cowpeas (no-till), and cowpeas-maize (plowed).Total loss of nutrient elements in runoff and eroded soil materials was significantly affected by slope and by soil and crop management treatments. Total annual nutrient element losses in runoff were 55 kg/ha for bare-fallow, 17 kg/ha for maize-maize (plowed), 12 kg/ha for cowpeas-maize (plowed), 2.3 kg/ha for maize-maize (plowed and mulched) and 4.3 kg/ha for maize-cowpeas (no-till). The concentration of nitrate in seepage water was two or three times higher than in surface water. Nutrient losses in eroded soil materials from the mulched and no-till treatments were negligible. From the plowed treatments, greatest losses were of organic matter and total nitrogen. The enrichment ratios were 2.4 times for organic carbon, 1.6 times for N, and 5.8 times for available phosphorus.     

公路边坡绿化覆盖物水土保持效果试验研究

公路施工过程中产生大面积裸坡,植物无法迅速生长,土壤流失量也特别大,铺设覆盖物是一种有效而廉价的保持水土的方法。为了研究不同覆盖物在坡面的水土保持效果,该文基于自制的室内人工模拟降雨器,在对其进行标定后,对已覆盖无纺布、遮阳网或草帘子的正在进行绿化喷播施工的模拟公路边坡进行人工模拟降雨试验,对3种覆盖物在公路边坡的水土保持效果进行了详细描述。3种覆盖物下坡面的径流量、径流系数、泥沙浓度以及产沙量均明显(P=0)小于裸坡的,说明无纺布、遮阳网和草帘子均可以有效的减少公路边坡喷播绿化过程中的水土流失。其中,草帘子覆盖下坡面的径流量(1.9mL/s)比裸坡减小69.9%,径流系数(6.4%)比裸坡减小14.9%,坡面产沙量(1.5g/m2)仅为裸坡的3.4%,且远小于无纺布和遮阳网覆盖下的,说明草帘子对公路边坡的水土保持效果较好。该文为公路边坡绿化施工中覆盖物的水土保持效果提供理论依据,为覆盖物的选择提供科学参考。     

Some effects of tramlines on surface runoff, sediment and phosphorus mobilization on an erosion-prone soil

Although introduced into UK farming to help ensure more even application of agrochemicals, tramlines (marked wheelways through crops) are a potential cause of surface runoff and transfer of diffuse pollutants, including sediment and phosphorus (P), into watercourses. To help quantify these potential effects, the impact of tramlines on sediment and P movement in surface runoff was assessed on an erosion‐prone sloping (5°) fine sandy soil over two successive winters. Three replicate and hydrologically isolated runoff plots measuring 15 m long and 2 m wide, and either with, or without, a tramline, were established on field demonstration areas which had received different soil (traditionally ploughed vs. reduced cultivated) and crop (early vs. late drilling) management practices. Reduced cultivation (minimum tillage) consisted of heavy discing (5–8 cm depth) instead of ploughing (20–25 cm depth). Over monitoring periods ranging up to 5 months, plots with tramlines running up and down the slope generated, on average, 46% more runoff (+1–2 mm) compared with plots without tramlines on ploughed soils. This extra runoff resulted in up to fivefold greater sediment loss (+0.4 t ha^?1) and up to fourfold greater total P loss (+0.3 kg ha^?1) from the plots. However, the presence of tramlines had no significant impact on runoff, or sediment and P transfers, where the soil received reduced cultivation. Plots with tramlines that were partially crop covered, or which ran across the slope rather than up and down the slope, produced the same amount of runoff, sediment and P transfer as plots without tramlines. Greatest entrainment of sediment and P in runoff occurred where tramlines coarsely indented the soil, or caused erosion rills to form. Establishing tramlines in dry soils reduced the degree of soil indentation and the risk of channelled runoff causing sediment and P entrainment. The data suggest that tramlines can be managed more sensitively on erosion vulnerable soils to help minimize the risk of sediment and P pollution of our surface waters, and various options are discussed.     

不同放牧强度对流域降雨径流中氮磷流失的影响

在呼伦贝尔草原克鲁伦河流域选取轻度放牧、重度放牧及不放牧草场,利用降雨模拟器进行降雨模拟试验,研究了不同放牧强度草场的地表物理性质、植被类型对降雨产流、营养元素流失等因素的影响。结果表明:在20,45,65 mm/h降雨强度下重度放牧草场产流时间最短,不放牧草场产流时间最长。径流量及径流系数总体规律显示为重度放牧草场 > 轻度放牧草场 > 不放牧草场。3种放牧强度草场的氮磷流失量均随雨强的增加而增大。降雨产流初期氮磷浓度相对较高,随径流时间增加逐步下降,最后达到稳定。径流量与氮磷含量之间存在二项式显著相关关系。     

THE ERODIBILITY OF TWO SOILS FROM KENYA

A portable rainfall simulator was used to measure the runoff rates and soil losses from a freshly ploughed luvisol at Katumani, and a nitosol at Kabete, on a 6° slope at varying rainfall intensities. The soil losses from storms of 50 and 100 mm/h intensities, in which a total of SO mm rain was applied to plots in the wet moisture state, varied from 0.8 to 1.4 metric tons/ha at Kabete and 8.5 to 13.9 metric tons/ha at Katumani. The percentage runoff from these storms was 15 to 17 per cent at Kabete and 67 to 71 per cent at Katumani. The much greater runoff rates from the Katumani soils were shown to be due to surface capping caused by degradation of the surface structure. It has been proposed that soil credibility K factors of 0.4 and 0.04 could be used for the Katumani and Kabete soils respectively in the Universal Soil Loss Equation     

聚丙烯酰胺应用对黄土复合坡面降雨产流的影响

复合坡是自然界常见的主要坡型。通过室内人工降雨模拟试验,研究了复合坡面降雨产流规律以及聚丙烯酰胺(polyacrylamide,PAM)应用对其的影响。试验采用2种复合坡型(凹型坡和凸型坡)的12个坡度组合和4个PAM施用量,共48个试验处理。结果显示,PAM应用显著缩短了初始降雨产流时间,初始产流时间平均比对照处理提前63.7%~71.6%。PAM应用明显改变了坡面径流随降雨历时的变化规律。PAM应用后,除了大坡度(≥10°)、小量PAM应用(0.5 g/m2)的凸型坡外,降雨径流系数在整个降雨过程中基本维持稳定。PAM应用增大了降雨径流系数和径流量,且径流系数和径流量随着PAM施用量的增大而增大。凸型坡的径流量平均比凹型坡的大14.7%~31.8%。当PAM施用量为0.5、1.0和2.0 g/m2时,凹型坡和凸型坡的径流量分别比对照处理增加55.7%、100.2%、147.3%和16.6%、69.3%、108.9%。在黄土坡地上大剂量(≥1.0 g/m2)应用PAM可明显增大坡面径流量,实际应用中应制定合理的PAM施用量。