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1.
Both disturbance history and previous land use influence present-day vegetation and soils. These influences can have important implications for conservation of plant communities if former disturbance and land use change species abundances, increase colonization of nonnative plant species or if they alter soil characteristics in ways that make them less suitable for species of conservation interest. We compared the plant species composition, the proportion of native and nonnative plant species, and soil biogeochemical characteristics across seven dominant land use and vegetation cover types on the outwash sandplain of Martha’s Vineyard that differed in previous soil tillage, dominant overstory vegetation and history of recent prescribed fire. The outwash sandplain supports many native plant species adapted to dry, low nutrient conditions and maintenance of native species is a management concern. There was broad overlap in the plant species composition among pine (Pinus resinosa, P. strobus) plantations on untilled soils, pine plantations on formerly tilled soils, scrub oak (Quercus ilicifolia) shrublands, tree oak (Q. velutina, Q. alba) woodlands, burned tree oak woodlands, and sandplain grasslands. All of these land cover categories contained few nonnative species. In contrast, agricultural grasslands had high richness and cover of nonnative plants. Soil characteristics were also similar among all of the woodland, shrubland and grassland land cover categories, but soils in agricultural grasslands had higher pH, extractable Ca2+ and Mg2+ in mineral soils and higher rates of net nitrification. The similarity of soils and significant overlap in vegetation across pine plantations, scrub oak shrublands, oak woodlands and sandplain grasslands suggests that the history of land use, current vegetation and soil characteristics do not pose a major barrier to management strategies that would involve conversion among any of these vegetation types. The current presence of high cover of nonnative species and nutrient-enriched soils in agricultural grasslands, however, may pose a barrier to expansion of sandplain grasslands or shrublands on these former agricultural lands if native species are not able to outcompete nonnative species in these anthropogenically-enriched sites.  相似文献   

2.
Extensive afforestation using Pinus and Eucalyptus has taken place in Calabria since the early 1960's to control expansion of calanchi and biancane. In 1978 three small catchments were established near Crotone to monitor the effect of afforestation on hydrological response and sediment yield. In 1992, rainfall simulation experiments were carried out on plots in these catchments to determine more precisely the effect of tree and ground vegetation on surface runoff and erosional response. Most experiments were carried out in a logged catchment with slopes ranging from 20 to 30° and aspects from SW to NE. Results showed complex runoff generation and sediment production, reflecting the effect of microclimate and subtle variations in vegetation on infiltration characteristics. On south-facing slopes with little ground vegetation runoff generation was rapid with runoff coefficients from 27 to 37% and peak sediment concentrations reaching 83.7 g · 1−1. On north-facing slopes with good tree cover, little grass, but continuous leaf litter, runoff coefficients reached 21%, but peak sediment concentration was only 3.6 g · 1−1, while on recently logged north-facing slopes with dense grass cover the highest runoff coefficient was only 5.5% runoff coefficient, and there was virtually no sediment production. Implications of results for forest management and soil conservation are discussed.  相似文献   

3.
Semiarid karst landscapes represent an important ecosystem surrounding the Mediterranean Basin for which little is known on runoff generation. Knowledge of the sources and patterns of variation in infiltration–runoff processes and their controls is important for understanding and modelling the hydrological functions of such ecosystems. The objectives of this paper are to determine the infiltration rates and their controls in a representative mountain karst area (Sierra de Gádor, SE Spain) at micro-plots and to investigate the integrated response of rainfall on a typical hillslope. Rainfall simulations in micro-plots and natural rainfall-runoff monitoring on a hillslope were carried out complementarily. We investigated the role of soil surface components (vegetation, rock outcrop, fracture, and soil crust), topographic position, antecedent soil moisture, and rainfall characteristics in regulating infiltration–runoff processes. Results of rainfall simulation revealed the importance of vegetation cover and the presence of rock fractures in promoting the infiltration in the limestone karst landscape, while bare patches and rock outcrops acted as sources for runoff. All plots with > 50% vegetation cover had no runoff with up to 55 mm h− 1 of simulated rain. In contrast, nearly all bare plots had runoff under the same simulated rain, with runoff coefficients ranging from 3.1 to 20.6% on dry soil surface conditions, and from 2.0 to 65.4% on wet soil surfaces. Runoff coefficients amounted to 59.0–79.5% for rock outcrops without cracks, but were drastically reduced by the presence of cracks. The surfaces with rock fragments resting on the soil (generally located in the middle of the slopes) prevented more effectively the runoff generation than those surfaces where rock fragments were embedded in the top soil. Antecedent soil moisture had significant impact on runoff generation, with wet soil having doubled runoff coefficient, shortened time to runoff, and increased runoff rate compared to the same but dry soil. Linear regressions indicated that the main controls for constant infiltration rate were the cover percentages of vegetation and litter, plus rainfall intensity; while the major controls for runoff coefficient were the bare soil and vegetation coverage, plus rainfall intensity. High infiltration rates measured at the micro-plots agreed with low intra-event runoff coefficients (mostly below 1%) observed under natural rainfalls at the hillslope. Runoff depth and coefficient at the hillslope was significantly correlated with rainfall depth, maximum hourly rainfall intensity and antecedent precipitation over 20 days (AP20). During the 1.5-year monitoring period from Sep-2003 to Mar-2005, the overall infiltration was 41% of the total rainfall amount and the maximum infiltration rate was almost 94% of the largest single rainfall event. The results from this study contribute to improved understanding of the magnitude and controls of the surface runoff in semiarid karst mountain areas.  相似文献   

4.
Restoring the native vegetation is one of the most effective ways to control soil degradation in Mediterranean areas, especially in very degraded areas. In the initial months after afforestation, vegetation cover establishment and soil quality could be better sustained if the soil was amended with an external extra source of organic matter. The goal of this study was to test the effect of various organic amendments on select soil properties [soil organic carbon (SOC), pH, and electrical conductivity (EC)] over a 24‐month period. Four amendments were applied in an experimental set of plots: straw mulching (SM), mulch with chipped branches of Aleppo Pine (Pinus halepensis L.; PM), sheep manure compost (SH), and sewage sludge (RU). Plots were afforested following the same spatial pattern, and amendments were mixed with the soil at the rate 10 Mg ha−1. Organic amendments helped maintain SOC over the initial 6 months after the afforestation. However, only the SM and PM treatments had increased SOC values after 24 months. Decreases in EC were found after the addition of SM, PM, and SH amendments. However, RU increased EC values 24 months after the afforestation. Variations in pH values were not sufficient to establish differences among the various treatments. Furthermore, the results show that forest soils with or without organic amendments responded similarly to the seasonal changes in Mediterranean conditions. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

5.
The relationship between biodiversity and ecosystem functioning is of major scientific concern today. Few studies though have measured the interactions between soil microorganisms and plant diversity, the purpose of this study was to examine the link between plant diversity and microbial communities in fertilized versus unfertilized grasslands. Experiments were carried out on a permanent grassland in north-eastern France where agricultural practices had remained unchanged for the last 13 years. The experimental design included two plots of 300 m2 (fertilized at 120 kg N ha−1 or non-fertilized). Plots were replicated into three equal sub-plots (100 m2). From each sub-plot, six samples of soil and vegetation were taken at three dates during floristic development. At sampling, ground cover of each species was estimated, and total amount of C and N was determined in aboveground and root biomass. Soil samples were analyzed in order to measure the metabolic fingerprints of microorganisms using Biolog® GN2 microplates. Floristic composition and carbon substrate utilization patterns of rhizobacterial communities were more diversified in unfertilized than fertilized plots. In unfertilized plots, the development of Convolvulus arvensis and two legumes (Trifolium pratense and Trifolium repens) may help maintain observed floristic diversity. Moreover, an inversion of C and N distribution between aboveground and root biomass during the vegetation cycle probably induced a variation of rhizodeposition. This phenomenon could explain the differences of rhizobacterial metabolic fingerprints observed between experimental plots.  相似文献   

6.
Annual soil losses in southern Italy can exceed 100–150 t ha− 1 year− 1. Where erosion on agricultural land is particularly severe, land use change and afforestation are frequently seen as the most appropriate means of reducing erosion risk. However, the overall effectiveness of afforestation in reducing soil erosion remains uncertain, due to the poor development of the forest cover in some areas, leading to significant areas with sparse tree cover, and the erosional impact of forest harvesting, which commonly involves clearcutting. The study reported here addresses this uncertainty and focuses on two small catchments (W2 and W3) located in Calabria, southern Italy, for which measurements of suspended sediment yield are available. Both the catchments originally supported a rangeland vegetation cover and they were planted with eucalyptus trees in 1968. Currently, only catchment W3 supports a continuous forest cover. In catchment W2 the forest cover is discontinuous and there is a significant area of the catchment (ca. 20%) where the tree cover is sparse and the vegetation cover is dominated by natural grasses. Two additional erosion plots were established within catchment W2 in 1991, in order to explore the effect of the density of the tree cover on soil erosion. Information on the sediment yields from the two catchments and the plots for 10 storm events that occurred during the period December 2005–December 2006 and associated information on the 137Cs and excess 210Pb of the sediment, have been used to investigate the effectiveness of afforestation in reducing sediment mobilisation and net soil loss from the catchments involved. The results demonstrate that the areas of greatest soil loss are associated with the slopes where the tree cover is discontinuous, and that forest harvesting by clearcutting causes significant short-term increases in sediment mobilisation and sediment yield. These findings, which are consistent with previous work undertaken within the same area, emphasize the importance of vegetation cover density in influencing rates of soil loss in the study catchments. The study also provided a useful demonstration of the potential for using measurements of the 137Cs and 210Pbex content of sediment, in combination with more traditional sediment monitoring, to investigate sediment sources and to compare the sediment dynamics of catchments subjected to different land management practices.  相似文献   

7.
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.  相似文献   

8.
In slopes of Mediterranean mid-mountain areas, land use and land cover changes linked to the abandonment of cropland activity affect soil quality and degradation and soil redistribution; however, limited attention has been paid to this issue at catchment scale. This paper evaluates the effects of cropland abandonment and post-land abandonment management (through natural revegetation and afforestation) on soil redistribution rates using fallout 137Cs measurements in the Araguás catchment (0.45 km2, Central Spanish Pyrenees). A total of 52 soil core samples, distributed in a regular grid, from the first 30–40 cm and 9 sectioned reference samples were collected across the catchment and soil properties were analysed. Fallout 137Cs was measured in a 5 cm sectioned references samples and in bulk grid samples. 137Cs inventories were used to estimate soil erosion and deposition rates across the catchment. Results show that the highest erosion rates were recorded under sparsely vegetated sites in the badland area, while the lowest rates were found in the afforested area, but no significant differences were observed between the different uses and covers in soil redistribution rates likely due to a long history of human intervention through cultivation in steep slopes and afforestation practices. However, the recovery of the soil organic matter in afforested areas suggest that afforestation can reduce soil degradation at long-term scale. The information gained achieve a better understanding of soil redistribution dynamics and provide knowledge for effective land management after cropland abandonment of agroecosystems in Mediterranean mountain areas.  相似文献   

9.
Soil erosion such as sheet erosion is frequently encountered in subalpine grassland in the Urseren Valley (Swiss Central Alps). Erosion damages have increased enormously in this region during the last 50 y, most likely due to changes in land‐use practices and due to the impact of climatic changes. In order to estimate the effect of vegetation characteristics on surface runoff and sediment loss, we irrigated 22 pasture plots of 1 m2 during 1 h at an intense rain rate of 50 mm h–1 in two field campaigns using a portable rain simulator. The rain‐simulation plots differed in plant composition (herb versus grass dominance) and land‐use intensity but not in plant cover (>90%) nor in soil conditions. Prior to the second rain‐simulation campaign, aboveground vegetation was clipped in order to simulate intense grazing. The generated surface runoffs, sediment loss, relative water retention in the aboveground vegetation, and changes in soil moisture were quantified. Runoff coefficient varied between 0.1% and 25%, and sediment loss ranged between 0 and 0.053 g m–2. Thus, high infiltration rates and full vegetation cover resulted in very low erosion rates even under such extreme rain events. Surface runoff did not differ significantly between herb‐ and grass‐dominated plots. However, clipping had a notable effect on surface runoff in the test plots under different land‐use intensity. In plots without or with intensive use, surface runoff decreased after clipping whereas in extensively used plots, surface runoff increased after the clipping. This opposite effect was mainly explained by higher necromass and litter presence at the extensively used plots after the clipping treatment. The results obtained here contribute to a better understanding of the importance of vegetation characteristics on surface‐runoff formation, thus, on soil‐erosion control. Overall, we delineate vegetation parameters to be crucial in soil‐erosion control which are directly modified by the land‐use management.  相似文献   

10.
Severe soil and water loss has lead to widespread land degradation in China's loess plateau. During the past decades, a great deal of effort was made on vegetation restoration to reduce soil and water loss in the loess plateau. However, due to water shortage the efficiency of vegetation restoration was not as satisfactory as expected. As part of a vegetation restoration project, we conducted research aiming to understand the relationship between vegetation pattern and soil water dynamics. The goal was to find vegetation types appropriate for the loess plateau with scarce water resources. In 1986, fifteen plots of land were planted with five vegetation types: pine woodland, shrubland, sloping cropland, alfalfa and semi-natural grassland. Soil water content, runoff, soil erosion were measured for each plot. Environmental variables, such as rainfall, evaporation and temperature, were recorded simultaneously by an automated meteorological station. The relationship between land cover pattern and soil water dynamic was evaluated by using statistical models. We found that: (1) soil water loss occurred during the growing season, and it reached the maximum in the second half of July; (2) soil water was not fully replenished from rainfall during the rainy season; (3) pine woodland induced the largest water loss to surface runoff, followed by sloping cropland, alfalfa, semi-natural grassland and shrubland; the poor capability of pine woodland for water conservation may be attributed to soil compaction and poor ground coverage under the tree; (4) in most cases, soil water of the five vegetation types was low except for shrubland and semi-natural grassland where it was moderate-high during a few periods. These conditions inhibit sustainable vegetation growth in the semi-arid loess hilly area of the loess plateau, China.  相似文献   

11.
Large areas of traditional slope cropland were recently converted to other land‐use types in the semiarid Loess Plateau of China. In this study, we selected four representative conversion options of slope croplands, i.e., pastureland rotated with cropland (cultivated with Medicago sativa L. and rotated with Triticum aestivum L.), shrubland and woodland (afforested with Hippophae rhamnoides L. and Pinus tabulaeformis), and grassland (native herbage Stipa breviflora) to study the effect of land‐use conversion by comparing with traditional cropland. Compared with slope cropland, the relative effects of different conversion options on surface runoff and soil erosion were assessed over a 14‐year measurement period. Observations showed that distinct features and consequences of vegetation succession were found among the conversion options. Plots of shrubland had the highest vegetation coverage with dense undergrowth; natural herbaceous and subshrub species gradually spread into plots of grassland resulting in higher vegetation cover. Neither bushes nor herbs colonized the plots of Pinus tabulaeformis, which resulted in a higher percentage of bare soil. Significant differences in runoff generation, sediment yield and conservation efficiencies among the selected conversion options were detected through an analyses of variance (ANOVA). Compared with cropland, total runoff and sediment decreased by 65 per cent and 95 per cent in shrubland, 41 per cent and 92·5 per cent in grassland, 18 per cent and 77 per cent in woodland, and 12 per cent and 58 per cent in pastureland, respectively. The ranking of soil and water conservation efficiencies was shrubland > grassland > woodland > pastureland > cropland. Based on the effectiveness of soil and water conservation, shrubland and grassland are highly recommended as promising options for cropland conversion projects. However, pastureland and woodland are not suggested as potential options for slope‐cropland conversion because of low soil and water conservation in the long term. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

12.
The effects of different Mediterranean vegetation cover on the biological and biochemical quality of soil is not well understood. The aim of this work is to evaluate the effects that different types of vegetation (forestry plots, mainly dominated by Spanish black pine (Pinus nigra Arn. ssp salzmannii) and herbaceous plots, where overstorey density is lower and natural herbaceous percentage is higher than in forestry plots) have in the biological properties of soil in Mediterranean humid climate. The impact of these plant communities on the biological soil quality was determined by several sensitive parameters related to the microbial activity of the soil such as soil respiration and some enzyme activities (urease, phosphatase and dehydrogenase). Development of vegetation (herbaceous and pines) was also determined and correlated with microbiological and biochemical indicators. Organic matter content in herbaceous sites was significantly higher than in forestry sites, ranging from 5.27 to 6.70 g 100 g?1 in herbaceous sites to 1.64–2.81 g 100 g?1 in forested areas. Herbaceous sites showed higher values of basal respiration and dehydrogenase activity than pine areas. However, the decrease of organic carbon content in pine areas led microbial activity enrichment per unit of carbon. These results conclude that vegetation cover significantly impacts soil microbial processes in Mediterranean humid climates, herbaceous vegetation having a more positive influence than forest vegetation on the biochemical and microbial activity of the soil, principally due to the higher accumulation of organic matter from plant remains.  相似文献   

13.
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.  相似文献   

14.
The effect of a pine plantation on a native subpáramo system in the Andes of Colombia (3100 m above sea level) was studied. The vegetation of an 8 year-old plantation with Pinus patula was compared to that of the surrounding native subpáramo. 59 plots made in the subpáramo vegetation contained 121 vascular plant species. These plots were classified into three subpáramo communities and one Andean scrub community. Sixty-four plots made in the pine plantation contained 76 vascular plant species and were subdivided into four classes of pine cover. With increasing pine cover, pine plantation plots tended to become less similar to the subpáramo communities. Habitat-specific subpáramo species tended to disappear with increasing pine cover. After controlling for the effects of environmental variables in a partial canonical correspondence analysis, pine cover had a significant impact on plant species patterns. It is concluded that afforestation with Pinus patula resulted in strong negative effects on diversity and composition of the subpáramo vegetation at the study site.  相似文献   

15.
Understanding of the relationships between vegetation and soil and topography would be very important for ecosystem restoration and management efforts in the dry valleys of Himalayan region but how to clarify the complicated relationships and figure out key factors for practical purpose is a challenge. The main objective of this research was to propose a four-staged procedure by combining several multivariate statistical techniques to detect the relationships between vegetation and soil and topography, and thereby identify the key factors for the degraded ecosystem restoration and management. Forty-three plots (5 m × 5 m) were selected for the field survey of the vegetation, soil and topography variables in the dry warm river valley of the upper Minjiang River, Sichuan Province, China. Cluster analysis (CA) demonstrated that high plant diversity, cover and height were associated with good soil quality and favorable topographic positions with lower solar incident radiation, runoff and soil erosion potential. Correlation analysis (simple correlation analysis and canonical correlation analysis) and multiple linear stepwise regression analysis affirmed that plant diversity was mainly correlated with soil water content, and soil water content was mainly determined by soil texture (clay content). Soil clay content alone could explain about 70% of the total variance. Identifying the favorable topographic position and the distribution pattern of soil texture and its controlling mechanisms is thus very important for restoration practices. In the process of ecosystem restoration, we should promote the co-evolution of vegetation and soil, and follow the natural succession sequence. Some relevant conservation polices are also needed to reduce human disturbance on ecosystem.  相似文献   

16.
Runoff production conditions in a small gully catchment are studied at four different scales: the point scale (0.001 m2), the local scale (1 m2), the field scale (of the order of 100 m2) and the catchment scale (0.2 km2). At the point scale, infiltration measurements were conducted using a tension infiltrometer. At the local and the field scale, runoff plots were setup on typical soil surface conditions of the catchment (plateau bare soil, hillslope bare soil and fallow grassland). At the catchment scale, stream discharges were measured at two gauging stations.The overland flow yield is significantly nonuniform in space, due to the high spatial variability of infiltration capacities and the depressional storage of the soil surface. The runoff and the infiltration data collected confirmed the major role played by soil crusting on runoff generation in that part of Sahel. At the point scale, hydraulic conductivity measurements have shown that infiltration and runoff were driven by the hydraulic properties of the crust. At the field scale, microtopography and heterogeneity in the soil surface crusting decreased discharge volumes. The influence of vegetation growth on runoff yield was evident in the case of the fallow sites. Analysis of discharge data at the catchment scale highlights that infiltration through the bottom of the gully between two gauging stations leads to considerable runoff water transmission losses.  相似文献   

17.
集水技术与林木生长的土壤水环境研究   总被引：8，自引：1，他引：8       下载免费PDF全文
该文依据多种集水技术条件下的降雨径流观测资料和林地不同空间位置上定期土壤水分观测资料，分析了在半干旱黄土地区集水造林技术与土壤水环境的关系，林木对水分的利用状况及林地水量平衡。结果表明：集水技术不仅改善了土壤水环境，而且提高了林木对降水的利用率。  相似文献   

18.
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.  相似文献   

19.
金沙江干热河谷典型区段水土流失特征   总被引：3，自引：1，他引：3  
以金沙江干热河谷典型区段不同处理坡面和林地、农地集水区为研究对象,采用坡面径流小区和集水区卡口站三角形薄壁堰实测法,在坡面径流小区和集水区土地利用现状调查基础上,通过降雨、径流及泥沙观测,分析金沙江干热河谷典型区段水土流失特征。结果表明:(1)不同处理坡面径流小区产流量、产沙量大小依次为坡耕地>自然坡面>水平阶整地>反坡台整地,表明反坡台和水平阶造林整地以及植被良好的自然坡面对地表径流的拦蓄和对泥沙的削减都起到较好效果;(2)大暴雨对集水区尺度产流产沙贡献值大,产流降雨量在4.8～27.6mm区间,农地集水区径流深小于林地集水区,大于27.6mm时,农地集水区径流深反超林地集水区,而产沙量不受降雨量影响,为林地集水区低于农地集水区;(3)径流小区尺度与集水区尺度雨季水土流失起止时间一致,集水区径流系数小于径流小区,集水区产沙量大于径流小区。  相似文献   

20.
Vegetation cover plays a major role in the restoration and stabilization of disturbed systems. The analysis of relationships between restored vegetation and soil hydrology has special relevance for the evaluation and operation of mining reclamation, particularly in Mediterranean-Continental environments, where climatic conditions restrict the development of continuous vegetation cover. The effect of herbaceous vegetation cover on soil hydrology was analysed by means of rainfall simulation (63 mm h− 1; 0.24 m2) in reclaimed soils derived from opencast coal mining (a non-saline and clay-loam textured spoil) in central-eastern Spain. A total of 75 simulation experiments were conducted at three different times throughout the year (late winter, summer and autumn) to control the influence of seasonal climatic fluctuations. Sediment concentrations in runoff and the runoff coefficient decreased exponentially with vegetation cover, while increases in steady infiltration rates were obtained with vegetation cover. Additional delays in runoff responses (longer time to runoff start and stabilization) and increases in the wetting front depth were observed with vegetation cover. Seasonal variations in soil surface state and moisture strongly influenced hydrological responses; although the influence of season on the analysed hydrological responses was attenuated by vegetation cover, especially in the case of infiltration rates. We also determined a practical ground cover threshold for site restoration and evaluation of over 50% vegetation cover, which could help achieve an optimum biological control of hydrological soil responses in the studied environment.  相似文献   

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