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1.
The rates of decomposition of barley roots labelled with 14C were investigated in soil planted with maize or perennial ryegrass and in fallow controls. Evolution of 14CO2 was significantly less from the planted soils than from fallow controls. Roots of maize and ryegrass appeared to compete substantially with soil microbes for 14C-labelled materials. Simple competitive effects were, however, insufficient to explain all of the observed effects of root growth on soil organic matter decomposition. There was no indication that the detrimental effects of maize roots on aggregate stability could be associated with increased degradation of native soil organic materials; the broader significance of the results is also discussed.  相似文献   

2.
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.  相似文献   

3.
Land preparation for mechanisation in vineyards of the Anoia–Alt Penedès region, NE Spain, has required major soil movements, which has enormous environmental implications not only due to changes in the landscape morphology but also due to soil degradation. The resulting cultivated soils are very poor in organic matter and highly susceptible to erosion, which reduces the possibilities of water intake as most of the rain is lost as runoff. In order to improve soil conditions, the application of organic wastes has been generalised in the area, not only before plantation but also every 3–4 years at rates of 30–50 Mg ha− 1 mixed in the upper 30 cm.These organic materials are important sources of nutrients (N and P) and other elements, which could reduce further fertilisation cost. However, due to the high susceptibility to sealing of these soils, erosion rates are relatively high, so a higher nutrient concentration on the soil surface increases non-point pollution sources due to runoff.The aim of this study is to analyse the influence of applied composted cattle manure on infiltration, runoff and soil losses and on nutrients transported by runoff in vineyards of the Alt Penedès–Anoia region, NE Spain. In the two plots selected for the analysis, composted cattle manure had been applied in alternate rows 1 year previous to the study. In each plot soil surface samples (0–25 cm) were taken and compared to those of plots without manure application. The study was carried out at laboratory scale using simulated rainfall. Infiltration rates were calculated from the difference between rainfall intensity and runoff rates, and the sediment and total nitrogen and phosphorus were measured for each simulation. In addition, the influence of compost was investigated in the field under natural rainfall conditions by analysing the nutrient concentration in runoff samples collected in the field (in the same plots) after seven rainfall events, which amount different total precipitation and had different erosive character.Compost application increases infiltration rates by up to 26% and also increases the time when runoff starts. Sediment concentration in runoff was lower in treated (13.4 on average mg L− 1) than in untreated soils (ranging from 16.8 to 23.4 mg L− 1). However, the higher nutrient concentration in soils produces a higher mobilisation of N (7–17 mg L− 1 in untreated soils and 20–26 mg L− 1 in treated soils) and P (6–7 mg L− 1 in untreated soils and 13–19 mg L− 1 in treated soils). A major part of the P mobilised was attached to soil particles (about 90% on average) and only 10% was dissolved. Under natural conditions, higher nutrient concentrations were always recorded in treated vs. untreated soils in both plots, and the total amount of N and P mobilised by runoff was higher in treated soils, although without significant differences. Nutrient concentrations in runoff depend on rainfall erosivity but the average value in treated soils was twice that in untreated soils for both plots.  相似文献   

4.
Two consecutive years of investigation on soil surface features, surface runoff and soil detachment within 1-m2 microplots on 40% slope highlighted the effects of land-use change, vegetation cover and biological activity on the water pathways in Northern Vietnam. Three replicate plots were set up on each of five land-uses: cassava (CAS), grass fodder of Bracharia ruziziensis (BRA), a 3-year old fallow (FAL), tree stands of Acacia mangium and Venicia montana (FOR), and a fallow with regrowth of Eucalyptus regularly cut (EUC). The second year, two of the microplots under FAL and EUC were treated with herbicide (FALh, EUCh), one of them was burnt (FALh+b, EUCh+b). The highest yearly surface runoff coefficient of 16%, and soil detachment rate of 700 g m− 2 yr− 1 in average with a maximum of 1305 g m− 2 yr− 1 have been recorded under CAS. On FALh and FALh+b, runoff ratios were 8.7 and 13.5%, respectively and detachment rates were 86 and 389 g m− 2. On FAL and BRA the yearly runoff ratio varied from 5.9 to 9.8% but the detachment rate was limited at 24 to 35 g m− 2. FOR and EUC annual runoff was ≤ 3.1% and annual soil detachment ≤ 71 g m− 2. These values were very low compared to the values reported on steep slopes in Laos within similar climate and vegetation cover.The runoff and detachment rates underlined the importance of rainfall intensities, soil physical properties, soil surface features, soil vegetation cover and biological activity. The annual surface runoff was highly correlated to the soil surface crusting. CAS and BRA plots were prone to crusting especially after weeding at the onset of the rainy season, when the soil surface was still uncovered. Soil bioturbation (earthworm casting activity) was the second factor that explains local variation of surface runoff and soil detachment. The continuous production of earthworms casts on soil surface, especially on FOR and EUC microplots, induced a marked surface roughness and reduced the surface runoff. The production of casts was very limited in FAL and completely absent in CAS microplots. So it is evident that our results confirm the deleterious effects of cassava on soil and water conservation.  相似文献   

5.
In this study, a soil filled Hydraulic Tilting Flume (HTF) was used as a test plot under simulated rainfall conditions. This flume was filled with mollisols soils (sandy loam in texture) collected from tarai region of Himalayas. The effects of root and shoot characteristics of Napier grass in terms of leaf area index (LAI), shoot length (SL), number of leaves (NL), number of tillers (NT), shoot biomass (SB), root density (RD), root length (RL), root biomass (RB), and total biomass (TB) were investigated on runoff and sediment outflow at 90, 120 and 150 days after planting (DAP). Four simulated rainfall intensities namely 4.0, 6.5, 8.3 and 9.4 cm/h over three land slopes of 1, 2 and 3% were selected. Runoff samples collected from whole plant plot and only root plot were analyzed for runoff and sediment outflow. Findings revealed that Napier grasses were very effective to reduce runoff and sediment outflow and its efficacy increased with the extended growth stages. The reduction in runoff and sediment outflow at 90, 120 and 150 DAP was obtained as 56% and 85%, 68% and 90%, and 74% and 96%, respectively, as compared to bare plot conditions. It was observed that the comparative contribution of shoots in runoff rate reduction was higher than the roots. On the contrary, the root part of the plant showed more contribution in sediment rate reduction as compared to the shoot part. Step wise regression was attempted for the selection of effective input parameters to establish authentic runoff and sediment outflow models. Power form of multiple non-linear regression (MNLR) showed very satisfactory results for predicting runoff and sediment outflow with coefficient of determination (R2) as 97.4% and 99.0%, respectively, root mean square error (RMSE) as 38.8 cc/m2/min and 0.126 g/m2/min, respectively, and coefficient of efficiency (CE) as 93.9% and 96.7%, respectively, during testing period.  相似文献   

6.
On-site and off-site environmental impacts of runoff and erosion are usually stressed in order to bring to the public's attention the importance and implications of soil erosion. However, few studies are aimed at calculating the economic implications of erosion, this being the message that farmers and/or policy makers understand best. In this current work we estimated the cost of erosion in vineyards in the Penedès–Anoia region (NE Spain), in which high intensity rain storms (> 80–100 mm h− 1) are frequent. Modern plantations in the region consist of trained vines, usually planted perpendicular to the maximum slope direction. Broadbase terraces are interspersed between vine rows to intercept surface runoff and convey it out of the field. Part of the sediment generated above these terraces is deposited in them and other parts are either deposited beyond the boundaries of the fields or are exported to the main drainage network. High intensity rainfall produces heavy soil losses (up to 207 Mg ha− 1 computed in an extreme event in June 2000, which had a maximum intensity in 30-min periods of up to 170 mm h− 1). To estimate the cost of erosion in vineyard fields of this region, two important aspects were considered. These were a) the cost incurred by the maintenance of the broadbase terraces, drainage channels and filling of ephemeral gullies and b) the cost incurred by the loss of fertilisers (mainly N and P) caused by erosion. According to farmers' records, the former was estimated at 7.5 tractor-hour ha− 1 year− 1 (as average), which comprises 5.4% of the income from grape sales. Regarding N and P losses, nutrients exported by runoff were 14.9 kg ha− 1 N and 11.5 kg ha− 1 of P, which, if compared to the annual intakes, represent 6% and 26.1% of the N and P respectively. In economic terms, the replacement value of the N and P lost represents 2.4% for N or 1.2% for P of the annual income from the sale of the grapes.  相似文献   

7.
In this study, we evaluated (1) the plant uptake of polycyclic aromatic hydrocarbons (PAHs) from soil and water and (2) the applicability of the partition-limited model on the prediction of plant concentrations with respect to PAH contents in soils and other associated parameters. To accomplish these goals, the plant uptake of PAHs from culture solution and soils were extensively experimented. A steady state was shown for ryegrass kinetic uptake of phenanthrene and pyrene from water after about 48 h. As to the ryegrass uptake from soils, root and shoot concentrations of PAHs generally increased, while root concentration factors (RCFs) and shoot concentration factors (SCFs) tended to decrease with the increasing PAH concentrations in soils after 45 days. One note of interest is that root concentrations and RCFs of phenanthrene and pyrene for ryegrass uptake were larger than shoot concentrations and SCFs, irrespective of soil–plant and water–plant systems. However, root and shoot concentrations, or RCFs and SCFs, for ryegrass uptake from culture solution were always much higher than those for ryegrass uptake from soils at the same PAH concentrations in water or soil interstitial water, indicating that PAHs in culture solution would be more available and susceptible than those in soil interstitial water for uptake by plants. In addition, the partition-limited model showed a high level of model performance on prediction of plant uptake of phenanthrene and pyrene from soils, with the overall differences of the modeled and experimented concentrations in ryegrass roots or shoots less than 187%. This suggests that the partition-limited model might be a potentially useful instrument for vegetation-contamination assessment.  相似文献   

8.
S. Assouline  M. Ben-Hur 《CATENA》2006,66(3):211-220
Soil erosion during rainfall is strongly affected by runoff and slope steepness. Runoff production is drastically increased when a seal is formed at the soil surface during rainfall. Therefore, a complex interaction exists between soil erosion and surface sealing. In this study, the dynamics of interrill erosion during seal formation is studied under different simulated rainfall and slope conditions. A sandy soil was exposed to 70 mm of rainfall at two intensities, 24 mm h− 1 and 60 mm h− 1, and five slope gradients, from 5% to 25%. Infiltration, runoff and soil loss rates were monitored during rainfall. Final infiltration rates increased with slope gradient at both rainfall intensities, this effect being stronger for the higher intensity. Cumulative runoff at the end of the rainfall event was lower as slopes were steeper, while an opposite trend was obtained for soil loss. For the 5% and the 9% slopes, the sediment concentration in runoff reached quickly a stable value during the whole rainfall event, while it reached a peak value before declining for the higher slopes. The peak value and its timing were rainfall intensity dependent. Soil erodibility during seal formation was evaluated using two empirical multiplication-of-factors type models. It seems that slope and rainfall erosivity are accounted for only partly in these models. For mild slope gradients below 9%, the value of Ki estimated by means of the two expressions becomes practically constant shortly after runoff apparition. Consequently, the estimates resulting from this type of expressions remain valuable from the practical point of view.  相似文献   

9.
Cover crops are a very effective erosion control and environmental conservation technique. When cover crops freeze at the beginning of the winter period, the above-ground biomass becomes less effective in protecting the soil from water erosion, but roots can still play an important role in improving soil strength. However, information on root properties of common cover crops growing in temperate climates (e.g. Sinapis alba (white mustard), Phacelia tanacetifoli (phacelia), Lolium perenne (ryegrass), Avena sativa (oats), Secale cereale (rye), Raphanus sativus subsp. oleiferus (fodder radish)) is very scarce. Therefore, root density distribution with soil depth and the erosion-reducing effect of these cover crops during concentrated flow erosion were assessed by conducting root auger measurements and controlled concentrated flow experiments with 0.1 m topsoil samples. The results indicate that root density of the studied cover crops ranges between 1.02 for phacelia and 2.95 kg m− 3 for ryegrass. Cover crops with thick roots (e.g. white mustard and fodder radish) are less effective than cover crops with fine-branched roots (e.g. ryegrass and rye) in preventing soil losses by concentrated flow erosion. Moreover, after frost, the erosion-reducing potential of phacelia and oats roots decreased. Amoeba diagrams, taking into account both below-ground and above-ground plant characteristics, identified ryegrass, rye, oats and white mustard as the most suitable species for controlling concentrated flow erosion.  相似文献   

10.
Estimate of sediment yield in a basin without sediment data   总被引：4，自引：0，他引：4  
Vlassios Hrissanthou   《CATENA》2005,64(2-3):333
In this study, three mathematical models for the estimate of sediment yield, due to soil and stream erosion, at the outlet of a basin are presented. Each model consists of three submodels: a rainfall-runoff submodel, a soil erosion submodel and a sediment transport submodel for streams. The rainfall-runoff and the stream sediment transport submodels are identical in the three mathematical models. The rainfall-runoff submodel that is used for the computation of the runoff in a sub-basin is a simplified water balance model for the soil root zone. For the estimate of soil erosion in a sub-basin, three different submodels are used alternatively, owing to the fact that erosion or sediment yield data are not available. The soil erosion submodels are (a) a modified form of the classical Universal Soil Loss Equation (USLE, [Foster, G.R., Meyer, L.D., Onstad, C.A., 1977. A runoff erosivity factor and variable slope length exponents for soil loss estimates. Transactions of the ASAE, 20 (4), 683–687]) taking into account both the rainfall erosion and the runoff erosion, (b) the relationships of Poesen [Poesen, J., 1985. An improved splash transport model. Zeitschrift für Geomorphologie, 29, 193–211] quantifying the splash detachment, as well as the upslope and downslope splash transport, (c) the relationships of Schmidt [Schmidt, J., 1992. Predicting the sediment yield from agricultural land using a new soil erosion model. Proceedings of the 5th International Symposium on River Sedimentation. Karlsruhe, Germany, pp. 1045–1051] including the momentum flux exerted by the droplets and the momentum flux exerted by the runoff. The sediment transport submodel for streams aims to estimate the sediment yield at the outlet of a sub-basin. This quantity results by comparing the available sediment amount in the main stream of a sub-basin with the sediment transport capacity by stream flow, which is computed by the relationships of Yang and Stall [Yang, C.T., Stall, J.B., 1976. Applicability of unit stream power equation. Journal of the Hydraulics Division, ASCE, 102, 559–568]. The mathematical models were applied to the basin of Kompsatos River, in northeastern Greece, with an area of about 565 km2. The whole basin was divided into 18 natural sub-basins for more precise calculations. Monthly rainfall data were available for 27 years (1966–1992); therefore, the calculations were performed on a monthly basis. The deviation between the three mean annual values of sediment yield at the basin outlet, for 27 years, resulting from the three mathematical models is relatively small.  相似文献   

11.
为探究喀斯特地区林木根系分布方式对坡面土壤侵蚀的影响,采用人工模拟降雨方法,研究林木根系3类分布方式：根系横坡方向局部裸露（横向）、根系顺坡方向局部裸露（顺向）、根系垂直坡面（垂直）的土壤侵蚀特征。降雨强度为75 mm/h,降雨历时为90 min,坡度为25°。结果表明：（1）降雨过程中,横向和垂直生长根系影响土壤入渗,壤中流和地下径流产流时间表现为顺向>横向>垂直;顺向坡面地表径流初始产流时间比横向和垂直坡面略有提前,但差异不显著（p>0.05）;（2）横向、顺向及垂直坡面地表径流总量大小表现为顺向>垂直>横向,壤中流与地下径流产流速率在降雨过程中缓慢增加,降雨停止后急剧减小;（3）林木根系3类分布方式坡面间的地表减沙效益表现为横向>垂直>顺向。综上所述,顺向坡面的汇流作用促使地表产流产沙增加,垂直坡面增加土壤降雨入渗并减少侵蚀,横向坡面对坡面径流泥沙的拦蓄作用最为明显。研究结果对认识喀斯特石漠化坡地土壤侵蚀机理和水土流失防治措施提供了参考。  相似文献   

12.
Soil tillage may increase vulnerability to water erosion, whereas no tillage and other conservation cultivation techniques are viewed as strategies to control soil erosion. The objective of this research was to quantify runoff and soil losses by water erosion under different soil tillage systems at the Santa Catarina Highlands, southern Brazil. A field study was carried out using a rotating-boom rainfall simulator with 64 mm h−1 rainfall intensity on a Typic Hapludox, between April 2003 and May 2004. Five rainfall tests were applied along successive cropstages. Surface cover was none (fallow) or soybean (Glycine max, L.). Five treatments were investigated, replicated twice. These treatments were conventional tillage on bare soil (BS) as a control treatment and the following treatments under soybean: conventional tillage (CT), no tillage over burnt crop residues on never before cultivated land (NT-B), no tillage over desiccated crop residues, also on never before cultivated land (NT-D) and traditional no tillage over desiccated crop residues on a soil tilled 4 years before this experiment (NT-PT). Water losses by surface runoff seemed to be more influenced by vegetative crop stadium than by tillage system and consequently a wide range of variation in surface runoff was found, following successive cropstages. The most efficient tillage system in reducing surface runoff and soil losses was no tillage, particularly the NT-PT treatment. Sediment losses were more influenced by tillage system than water losses. In the NT-B, NT-D and NT-PT treatments the rate of sediment losses along the crop vegetative cycle showed a tendency to increase from the first to the second cropstages and later to decrease from the third cropstage onwards. In the conventionally tilled treatment (CT) soil losses were greater than in any of the no tillage treatments (NT-D, NT-B and NT-PT) during the initial growth periods, but at the end of the vegetative period differences in sediment rates between tilled and non-tilled treatments tended to be smaller. In the BS control treatment, soil losses progressively increased following the vegetative growth season of soybean.  相似文献   

13.
Abstract

This study was conducted on a sloping field at the Japan International Research Center for Agricultural Sciences, Okinawa Subtropical Station, Ishigaki Island, Okinawa Prefecture, Japan, to evaluate the effects of zero tillage farming combined with mucuna fallow as a cover crop on soil erosion and water dynamics. Two fallow systems (natural and mucuna) in combination with two soil tillage treatments (zero tillage and conventional tillage) were imposed on three sloping fields (2.0°, 3.5° and 5.0°). A sorghum crop (Sorghum bicolor (L) moench) was planted after the soil tillage treatment. Soil loss for zero tillage farming combined with mucuna fallow was equivalent to only 3% of that for the conventional tillage farming with natural fallow. Runoff water was also reduced by between 74% and 77% when compared with the conventional tillage system with natural fallow. These results indicate that zero tillage with mucuna fallow is a very effective measure for the control of soil erosion and water runoff. Moreover, this farming system improved water infiltration during both the fallow and the sorghum cropping periods. For the zero tillage plot, water loss as deep percolation increased 1.6-fold compared with that for the conventional farming under heavy rainfall conditions. It is expected that under less rainfall areas or seasons, the effects of zero tillage farming combined with the mucuna cover crop may be more pronounced on water runoff control and, therefore, may greatly improve soil water conditions.  相似文献   

14.
 We investigated whether, under a temperate climate and in a maize crop, earthworm casts could contribute to soil erosion and further favour the exportation of phosphorus by runoff waters. Recording of casts was made in compacted (wheel-tracks) and non-compacted inter-rows, for a 2-month period in spring. To assess the rainfall impact on cast evolution, half of the observation sites were protected against rain splash by a nylon mesh placed above the soil surface. The water runoff was collected and analysed for sediment contents and phosphorus concentration. The mean annual production of surface casts was calculated to be 34 kg (dry weight) year–1 kg–1 earthworm (fresh weight). Synchronization between cast erosion and rainfall events was shown under natural conditions (unprotected sites). The erosion rate was 4 times greater over rainy periods than dry ones, reaching 80% of cast numbers. It appeared that not the runoff effect but the splash effect, due to the kinetics of the drops, disrupted casts. Newly formed casts disappeared first, with the erosion rate decreasing twofold for casts more than 10 days old. Cast erosion and runoff, as well as worm casting activity, were greater under compacted sites than under non-compacted sites, indicating an influence of earthworms on soil erosion from compacted soils. The total phosphorus content was similar in casts and uningested soil (0.80 mg phosphorus g–1). Potential phosphorus losses from cast erosion was calculated to reach 25–49 mg phosphorus m–2 per rainfall event depending on soil compaction. The amounts of particulate phosphorus recovered in water runoff after each rainfall event varied from 1 mg to 11 mg phosphorus. These results are compared and discussed. Received: 20 October 1998  相似文献   

15.
Little is known on the hydrological behavior of the volcanic ash soils, which are characterized by extremely high porosities and hydraulic conductivities. In this study the occurrence and hydrological effects of water repellency were investigated at a plot scale for different types of land use and volcanic soils in Mexican volcanic highlands from Michoacan, Mexico: [1] fir, pine and oak mixed forest soils developed from lavas, [2] soils developed from volcanic ashes and pyroclastic sediments under sparse fir, pine and oak forest and shrubland, [3] pine and oak forested soils developed from lavas and pyroclastic sediments, and [4] bare soils on recent ash sediments in plain surfaces. Soil water repellency was assessed using the water drop penetration time test and rainfall simulations were performed on circular plots (50 cm in diameter) during 30 min and at an intensity of 90 mm h− 1 in order to study the hydrological response of each area. The return period for storms with a similar intensity in the area is 10 years. The shape and depth of the wetting front after simulated rainfall was also analyzed. Soil water repellency showed a high variability among the different studied zones. Organic matter content, soil texture and acidity were the most important factors for developing hydrophobicity. A wide range of soil water repellency classes (hydrophilic to severely water-repellent soils) has been found in soils under dense fir, pine and oak mixed forests or shrubland, while inexistent or slight water repellency has been observed in soils under sparse forest or at bare ash-covered areas. At a plot scale, marked differences in the hydrological behavior of the studied land use and soil zones were observed after the rainfall simulations. Soil water repellency contributes to fast ponding and runoff generation during the first stages of rainstorms. Runoff was enhanced in water-repellent forested soils (average runoff coefficients between 15.7 and 19.9%), in contrast to hydrophilic or slightly water-repellent soils, where runoff rates were lower (between 1.0 and 11.7%). Shallow and irregular wetting fronts were observed at water-repellent zones, reducing the soil water storage capacity. The implications of soil water repellency in soil hydrology and erosion risk in the area shed light on the soil hydrology of the studied ecosystems, and can contribute to develop better management policies.  相似文献   

16.
This paper reports results from the analysis of the soil hydrological response to simulated rainfall in a cork oak forest in Los Alcornocales Natural Park (SW Spain). Four different soil/vegetation units were selected for the field experiments: [1] cork oak woodland, [2] heathland, [3] grassland, and [4] cork oak/olive tree mixed forest. Rainfall simulations tests were performed on circular plots of 1256.6 cm2 at an intensity of 56.5 mm h− 1 for 30 min.Marked differences in the hydrological behavior of the studied vegetation types were observed after the rainfall simulations. The soils under woodland showed low runoff rates and coefficients. The highest runoff rates were measured on the heath and grass-covered parts of the hillslope. Water repellency of the soil, measured from water drop penetration tests, reduced infiltration (especially under the heathland), and seems to be the cause of fast ponding and runoff generation during the first stages of rainstorms.The mosaic of different patterns of hydrological response to rainfall, such as runoff generation or infiltration, is governed by the spatial distribution of vegetation and its influence on the soil surface.  相似文献   

17.
蚓粪对黑麦草吸收污染土壤重金属铜的影响   总被引：19，自引：0，他引：19  
林淑芬  李辉信  胡锋 《土壤学报》2006,43(6):911-918
在长江冲积物形成的高沙土中加入CuSO4.5H2O模拟土壤污染,使Cu污染浓度分别为200、400、600 mg kg-1,并设置加蚓粪(15%)和加原土(15%)处理,二处理各设种植黑麦草(Lolium multiflorum)和不种黑麦草培养试验,研究蚓粪对黑麦草生长及对Cu吸收的影响,以揭示蚓粪在Cu污染土壤植物修复中的作用。结果表明:蚓粪显著增加了黑麦草的地上部和地下部的生物量(p<0.001**)以及根系的长度、表面积、体积和根尖数(p<0.05*),在Cu浓度为200 mg kg-1时促进作用最大;蚓粪还显著提高了黑麦草地上部Cu的浓度及累积量,但显著降低了地下部的Cu浓度(p<0.05*),而对地下部的铜累积量没有影响,显示蚓粪能促进Cu从根系向地上部的运移及在地上部的富集。通过对土壤的pH和Cu的形态特征分析,发现种植黑麦草处理降低了土壤的pH并增加了可交换态铜的含量,而且这种作用在加入蚓粪后更加明显。推测蚓粪主要通过促进黑麦草根系的生长和活性而影响根系周围环境,提高重金属铜的生物有效性进而增加植物对铜的吸收。  相似文献   

18.
在自然降水条件下,定量研究黔西北喀斯特石漠化区典型乡土植物刺梨在坡耕地产流产沙的变化规律,分析该植物篱控制侵蚀产沙的水动力学机理。结果表明,刺梨植物篱截流、分流作用延缓径流产生及汇流时间,增加喀斯特坡面径流入渗量,减小坡面侵蚀动力。在不同降雨强度条件下,喀斯特坡面入渗率与径流量和产沙量呈负线性相关。植物根系缠绕串连黏结根土,改变土壤的入渗特性,增强土壤抗冲性与抗蚀能力。根系密度随土层深度增加而减少,减沙效应亦变小。土壤抗侵蚀能力与d<1mm的须根密度呈极显著正相关关系,与d≤2mm须根的根量、根长与土壤抗冲指数存在线性回归关系。当I30雨强为2.41mm时,植物篱小区几乎无流水侵蚀,而对照样地侵蚀产生较多泥沙;当I30为4.72,8.35mm时,研究小区皆已侵蚀产沙,并在对照样地侵蚀产生细沟,显示雨强加大,坡面产流动力加强,冲沙携沙能力加大。说明植物篱起到保水固土减沙和对土壤侵蚀水动力过程的调控。喀斯特坡面流侵蚀产沙水动力主要受降雨强度和雨滴动能影响,雨滴侵蚀力的大小取决于雨量、雨强、雨滴大小。侵蚀产沙量与雨强、降雨历时呈显著的幂函数关系。揭示了植物根系固土减沙和提高土壤抗侵蚀水动力的调控机理。  相似文献   

19.
Ultisols, widely distributed in tropical and subtropical areas of south China, are suffering from serious water erosion, however, slope hydrological process for Ultisols under different erosional degradation levels in field condition has been scarcely investigated. Field rainfall simulation at two rainfall intensities (120 and 60 mm/h) were performed on pre-wetted Ultisols with four erosion degrees (non, moderate, severe and very-severe), and the hydrological processes of these soils were determined. The variation of soil infiltration was contributed by the interaction of erosion degree and rainfall intensity (p < 0.05). In most cases, time to incipient runoff, the decay coefficient, steady state infiltration rate, and their variability were larger at the high rainfall intensity, accelerating by the increasing erosion severity. Despite rainfall intensity, the infiltration process of Ultisols was also significantly influenced by mean weight diameter of aggregates at the field moisture content, soil organic carbon and particle size distribution (R2 > 30%, p < 0.05). The temporal erodibility of surface soil and soil detachment rate were significantly and negatively correlated with infiltration rate (r < -0.32, p < 0.05), but less significant correlation was observed between sediment concentration and infiltration rate for most soils, especially at the high rainfall intensity. The variation of surface texture and soil compactness generated by erosion degradation was the intrinsic predominant factors for the change of infiltration process of Ultisols. The obtained results will facilitate the understanding of hydrological process for degraded lands, and provide useful knowledge in managing crop irrigation and soil erosion.  相似文献   

20.
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.  相似文献   

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