Ex-post evaluation of erosion control measures in southern Mali   总被引：3，自引：0，他引：3  

Ferko Bodnr  Wim Spaan  Jasper Hulshof 《Soil & Tillage Research》2007,95(1-2):27-37

As part of an impact study of a soil and water conservation (SWC) project in southern Mali, the effect of erosion control measures on soil erosion was evaluated. In one village, a baseline situation from 1988 was compared with the situation in 2003, after farmers had installed stone rows, live fences and grass strips, and had started cultivating across to the slope. This comparison showed a spectacular decrease in gully volume in cultivated fields of 87%, from 58 to 8 m³ ha⁻¹. Estimated annual soil loss decreased with 77% from 42 to 10 t ha⁻¹ year⁻¹. However, baseline data on erosion gullies were not available for other villages. In the absence of baseline data, a simple ‘with–without’ comparison does not allow a correct evaluation because farmers install erosion control measures especially in fields with more erosion. Two alternative methods were used: a reconstructed baseline and a virtual time series. Using the reconstructed baseline, looking not only at active gullies but also at (partly) reclaimed gullies, we concluded that line interventions, gully interventions, and a combination of both, reduced the proportion of active gullies by 48%, 47% and 70%, respectively. Using a virtual time series, comparing erosion in fields with erosion control measures installed in different years, we concluded that erosion gradually decreased by 50% during the 3 years after installation of erosion control measures. In a separate study, we found a positive effect of gully interventions and sowing across to the slope in reducing sheet erosion. A reduction of the slope of the sowing direction by 1% reduced the cover of runoff deposit of coarse sand with 8%. Although a documented baseline is preferred, both a reconstructed baseline and a virtual time series are useful tools and make ex-post evaluations more relevant than a simple with–without comparison.  相似文献   

Geomorphic response to historical agriculture at Monument Hill in the Blue Ridge Foothills of Central Virginia     

Rebecca K.R. Ambers  Daniel L. Druckenbrod  Clifford P. Ambers 《CATENA》2006

Historical forest clearance and agriculture have had profound effects on the landscape of the southeastern United States. This study examines a site called Monument Hill located in the eastern foothills of the Blue Ridge Mountains in central Virginia in order to better understand the long-term effects of historical agriculture on soil and streams. This site, deeply gullied and drained by an incised first-order stream, was first settled in the mid-eighteenth century and became part of a large nineteenth-century plantation. A thick sediment fan at the base of the hill buried and preserved a historical soil surface, archaeological artifacts, and woody debris datable by dendrochronology. The geomorphology of the site, along with limited historical data and tree ages from the mature second-growth forest cover, has enabled reconstruction of the sequence of land-use changes and measurement of geomorphic response over two and a half centuries.  相似文献   

Prescribed burning effects on the hydrologic behavior of gullies in the South Carolina Piedmont     

Marco A. Galang  Lawrence A. Morris  Daniel Markewitz  C. Rhett Jackson  Emily A. Carter 《Forest Ecology and Management》2010

Gullies found in the Piedmont of South Carolina are legacies of past land use and erosion. Although the majority of these gullies are now under forest vegetation and perceived as geomorphologically stable, the question of gully contribution to nonpoint source pollution remains undetermined, especially when these gullies are subjected to prescribed burning or other forest disturbance. Six prescribed burned and two reference gullies draining mature pine stands grown on former cotton fields were instrumented at the Long Cane Ranger District, Sumter National Forest, South Carolina to characterize the hydrologic behavior of these gullies and to investigate response to prescribed burning. Flow in the gullies was observed for one year of pre-burn and one year of post-burn conditions. Hydrologic behavior of these eight gullies varied greatly in the pre-treatment period. During the study, 48 rainfall events exceeding 12.7 mm were recorded, but one reference gully never produced flow and three treatment gullies flowed during three events or less and only in the pre-burn period. Although significant storm events occurred throughout the year, all gully flow events occurred between December and March. Double-mass and graphical analysis of relative stormflow production of the reference and treatment gullies in the pre- and post-treatment periods did not indicate an effect of the controlled burn on flow behavior, but the post-burn year was characterized by drought. The observed inter-annual variation in gully behavior was large. Observations of local groundwater conditions with piezometers and electrical resistivity surveys indicated that gully flows were controlled by the presence of a flow-restricting layer below the gully bed.  相似文献   

Topographical thresholds for ephemeral gully initiation in intensively cultivated areas of the Mediterranean   总被引：2，自引：0，他引：2  

L. Vandekerckhove  J. Poesen  D. Oostwoud Wijdenes  T. de Figueiredo 《CATENA》1998,33(3-4)

Ephemeral gullying is an important erosion process in Mediterranean areas suffering from land degradation because of increased drought and human impact. An ephemeral gully is formed when a hydraulic threshold for incision into a resistant soil surface is exceeded. The flow intensity at the soil surface of any landscape position is controlled by topographical parameters, such as local slope (S) and drainage-basin area (A). The objective of this study was to investigate to what extent one could use field measurements of S and A to predict the location of ephemeral gully initiation in intensively cultivated Mediterranean environments. Two relatively homogeneous study areas in Southeast Spain and Northeast Portugal with widespread ephemeral gullying were selected. S and A were measured by standard methods at the initiation point of 50 ephemeral gullies in each study area. The relationship between S and A was statistically investigated. On a double logarithmic scale, the S and A data showed considerable scatter. Orthogonal regression resulted in the threshold relationship S=aA^−b with b=0.133 for Spain, and b=0.226 for Portugal. The analysis also showed that S and A were weakly correlated for the Spanish dataset, and more strongly correlated for the Portuguese dataset. The correlation was considerably strengthened by including additional information on planform curvature and on tillage direction relative to the gully direction. Greater soil stoniness and the presence of a less permeable horizon generally increased the threshold level in both study areas. The threshold relationships resulting from this study were compared with literature data. The indices A_cS and ln(A_c/S) were applied to our study sites but neither relationship individually described the general trend between the data of S and A. Therefore, an alternative index, A_c^bS, with 0.133≤b≤0.226, according to the empirical trend between drainage basin area and local slope, was proposed to describe the topographical threshold conditions for ephemeral gully initiation in similar Mediterranean areas.  相似文献   

黄土高塬沟壑区植物对土质路蓄水减沙及水力参数的影响     

欧阳潮波  王文龙  黄鹏飞  朱宝才  李建明  李艳富  王浩 《草地学报》2014,22(5):971-979

采用野外放水冲刷试验,分析黄土高塬沟壑区种植冰草对道路蓄水减沙及水动力参数的影响。研究结果将为黄土高塬沟壑区沟坡防治与区域生态环境治理提供科学依据与途径。结果表明：当坡度为3°,6°和9°时,植物路平均蓄水量较土质路分别增加13.01%,22.45%和24.60%,而输沙量分别减少45.52%,68.34%和74.22%,道路的入渗率随放水历时呈双曲线型变化;输沙模数与放水流量呈显著线性相关,与流速呈二次函数关系;植物路通过降低流速、提高阻力系数达到减沙目的。  相似文献   

宁南黄土丘陵区不同生态恢复与重建中的土壤水分变化研究   总被引：7，自引：0，他引：7  

王月玲  张源润  蔡进军  李生宝  蒋齐 《中国农学通报》2005,21(7):367-367

针对宁南黄土丘陵区存在的生态脆弱、环境恶化的突出问题,对黄土丘陵区不同生态恢复过程中的土壤水分变化进行了研究。研究结果表明：在退化山地的植被恢复过程中, 0~60cm土层,土壤水分含量随恢复年限的增长而增加,在60cm土层以下,土壤含水量随着退耕年限的不断增长不断减小;对于不同恢复方式的土壤水分含量,88542水平沟>人工草地>鱼鳞坑>天然草地;对于不同植被类型的土壤水分含量,草地>灌木地>林地;对于不同地形的土壤水分含量,阴坡>半阴坡>阳坡,坡下部>坡中部>坡上部,并且随着坡度的不断增加,土壤水分含量不断减小。  相似文献   

基于耗散结构理论的黄土丘陵区耕地利用变化分析     

郝仕龙  曹连海  李春静 《中国生态农业学报》2010,18(1):170-174

耕地利用和保护是关系我国国民经济和社会可持续发展的全局性战略问题。针对黄土高原耕地利用和保护面临的问题,根据耗散结构理论,以黄土丘陵区耕地资源为研究对象,通过分析黄土丘陵区耕地资源利用的特点,构建了耕地系统的熵流模型,耕地利用效益、光合转化效益及生态效益是影响该区域耕地系统有序性的关键。以上黄试区为例,分析了该试区不同时期耕地系统熵流变化的规律。结果表明,从"六五"时期至"十五"时期,通过对该试区耕地系统进行综合治理,耕地系统的熵值逐步减少,其不同时期的熵变值分别为-0.6524、-0.1988、-0.3421、-0.2664和-0.2900,表明耕地系统的有序性、稳定性逐步提高。  相似文献   

黄土丘陵区不同干扰方式对退耕弃荒地植被恢复的影响     

张红蕾  丛日春 《安徽农业科学》2012,40(20):10557-10559

以黄土丘陵区安塞县为研究对象,选择了3种不同干扰方式退耕弃荒地,研究了不同干扰样地植物群落组成、群落结构、物种多样性和地上生物量特征,分析了不同干扰方式对退耕弃荒地植被恢复的影响。结果表明,随干扰强度增大,一年生草本植物所占比例增加,草本和灌木种类均减少;封育措施增加了物种多样性,灌木层已经形成天然灌草地的雏形;3种干扰方式样地地上部分生物量表现为封育样地>撂荒地>放牧样地,封育样地具有向天然地带性群落演替的迹象。  相似文献   

金沙江支流冲沟侵蚀区四种土地利用方式下土壤入渗特性研究   总被引：11，自引：0，他引：11  

周维  张建辉 《土壤》2006,38(3):333-337

在保持原有植被条件下,采用野外双环入渗法对金沙江支流安宁河谷冲沟侵蚀发生区4种土地利用条件下(荒草地活动沟、荒草地稳定沟、裸地活动沟、耕地)土壤入渗性进行研究。试验表明,前21．5 min土壤平均渗透率和累计入渗量均以荒草地稳定沟为最大,以裸地活动沟为最小,其余二者居中。4种土地利用条件下的入渗过程相似,并且可以用考斯恰可夫(костяковАН)公式f(t)=at-b得到很好的表达。植被能够有效增加土壤有机质的含量,而后者对改善土壤结构起着显著作用。土壤中>0．25 mm水稳性团聚体,尤其是其中的大粒径团聚体(>3 mm)含量较高,有利于提高土壤入渗性能。根量是能反映入渗性能强弱的重要生物学指标之一。具有良好入渗性的土壤,其地表径流减少,冲沟侵蚀得到有效遏制。  相似文献   

雾生绿蔓 流水听音——白云山蒲谷沟谷雨林改造构思     

李定涓 《广东园林》2007,29(B09):68-69

通过模拟雨林典型的生态现象，增加有雨林特色的植物，改造区域内的原有建筑等手法去改造蒲谷，以期达到沟谷雨林的效果。  相似文献