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1.
Few building codes contains provisions fault surface ruptures and accompanying soil deformations which constitutes a great risk to human lives, buildings and infrastructure. A numerical and experimental comparison show a fair agreement of result. Analysis of “real” scale show the how water increases the incompressibility of wet soil causing shear deformations to become larger and conjugate ruptures to appear for reverse faults. Field observations and numerical analysis indicates that horizontal compression of soil surrounding underground structures should be taken into account in design. 相似文献
2.
Relations between the spatial patterns of soil moisture, soil depth, and transpiration and their influence on the hillslope water balance are not well understood. When determining a water balance for a hillslope, small scale variations in soil depth are often ignored. In this study we found that these variations in soil depth can lead to distinct patterns in transpiration rates across a hillslope. We measured soil moisture content at 0.05 and 0.10 m depth intervals between the soil surface and the soil–bedrock boundary on 64 locations across the trenched hillslope in the Panola Mountain Research Watershed, Georgia, USA. We related these soil moisture data to transpiration rates measured in 14 trees across the hillslope using 28 constant heat sapflow sensors. Results showed a lack of spatial structure in soil moisture across the hillslope and with depth when the hillslope was in either the wet or the dry state. However, during the short transition period between the wet and dry state, soil moisture did become spatially organized with depth and across the hillslope. Variations in soil depth and thus total soil water stored in the soil profile at the end of the wet season caused differences in soil moisture content and transpiration rates between upslope and midslope sections at the end of the summer. In the upslope section, which has shallower soils, transpiration became limited by soil moisture while in the midslope section with deeper soils, transpiration was not limited by soil moisture. These spatial differences in soil depth, total water available at the end of the wet season and soil moisture content during the summer appear responsible for the observed spatial differences in basal area and species distribution between the upslope and midslope sections of the hillslope. 相似文献
3.
The fate and behavior of organochlorine pesticides (OCPs) in the Segara Anakan Estuarine ecosystem was studied in the Indonesian tropical climate, which is characterized by heavy rainfall in the rainy season and low rainfall in the dry season. Since OCPs have high affinity for soil, a field study on the dissipation and degradation pattern of soil‐applied 1,1,1‐trichloro‐2,2‐bis (4‐chlorophenyl) ethane (p,p′‐DDT) and 1,1‐dichloro‐2,2‐bis (4‐chlorophenyl) ethylene (p,p′‐DDE) as model OCPs was carried out. They occurred at a faster rate in the biphasic mode in wet conditions and at a slower rate in dry conditions. In wet conditions, the conversion from p,p′‐DDT to p,p′‐DDE and p,p′‐DDD (1,1‐dichloro‐2,2‐bis (4‐chlorophenyl) ethane) was governed by a parallel reaction. In dry conditions, only p,p′‐DDE was formed. The fate and behavior of OCPs in sediment estuary are similar to those in soil under wet conditions, except that their sorption‐desorption constants are influenced by estuarine surface water salinity. In the dry season, due to high salinity, the sediment acts as an OCP sink and a secondary source for the ecosystem, causes higher OCP concentration of local bio‐monitors, i. e., Geloina spp. and Mugil spp. In the rainy season, high water inflow washed the desorbed OCP pesticides out of the estuarine ecosystem, and caused lower concentrations of bio‐monitors. A risk evaluation for the uptake of OCP pesticides during the dry season suggests that adult fish meal consumers are safe, but risk management is required for pregnant woman. 相似文献
4.
The relative role of soil type and tree cover on water storage and transmission in northern headwater catchments 
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下载免费PDF全文 Soil water storage and stable isotopes dynamics were investigated in dominant soil–vegetation assemblages of a wet northern headwater catchment (3.2 km2) with limited seasonality in precipitation. We determined the relative influence of soil and vegetation cover on storage and transmission processes. Forested and non‐forested sites were compared, on poorly drained histosols in riparian zones and freely draining podzols on steeper hillslopes. Results showed that soil properties exert a much stronger influence than vegetation on water storage dynamics and fluxes, both at the plot and catchment scale. This is mainly linked to the overall energy‐limited climate, restricting evaporation, in conjunction with high soil water storage capacities. Threshold behaviour in runoff responses at the catchment scale was associated with differences in soil water storage and transmission dynamics of different hydropedological units. Linear input–output relationships occurred when runoff was generated predominantly from the permanently wet riparian histosols, which show only small dynamic storage changes. In contrast, nonlinear runoff generation was related to transient periods of high soil wetness on the hillslopes. During drier conditions, more marked differences in soil water dynamics related to vegetation properties emerged, in terms of evaporation and impacts on temporarily increasing dynamic storage potential. Overall, our results suggest that soil type and their influence on runoff generation are dominant over vegetation effects in wet, northern headwater catchments with low seasonality in precipitation. Potential increase of subsurface storage by tree cover (e.g. for flood management) will therefore be spatially distributed throughout the landscape and limited to rare and extreme dry conditions. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
Differences in preferential flow with antecedent moisture conditions and soil texture: Implications for subsurface P transport 总被引：2，自引：0，他引：2
Preferential flowpaths transport phosphorus (P) to agricultural tile drains. However, if and to what extent this may vary with soil texture, moisture conditions, and P placement is poorly understood. This study investigated (a) interactions between soil texture, antecedent moisture conditions, and the relative contributions of matrix and preferential flow and (b) associated P distributions through the soil profile when fertilizers were applied to the surface or subsurface. Brilliant blue dye was used to stain subsurface flowpaths in clay and silt loam plots during simulated rainfall events under wet and dry conditions. Fertilizer P was applied to the surface or via subsurface placement to plots of different soil texture and moisture condition. Photographs of dye stains were analysed to classify the flow patterns as matrix dominated or macropore dominated, and soils within plots were analysed for their water‐extractable P (WEP) content. Preferential flow occurred under all soil texture and moisture conditions. Dye penetrated deeper into clay soils via macropores and had lower interaction with the soil matrix, compared with silt loam soil. Moisture conditions influenced preferential flowpaths in clay, with dry clay having deeper infiltration (92 ± 7.6 cm) and less dye–matrix interaction than wet clay (77 ± 4.7 cm). Depth of staining did not differ between wet (56 ± 7.2 cm) and dry (50 ± 6.6 cm) silt loam, nor did dominant flowpaths. WEP distribution in the top 10 cm of the soil profile differed with fertilizer placement, but no differences in soil WEP were observed at depth. These results demonstrate that large rainfall events following drought conditions in clay soil may be prone to rapid P transport to tile drains due to increased preferential flow, whereas flow in silt loams is less affected by antecedent moisture. Subsurface placement of fertilizer may minimize the risk of subsurface P transport, particularily in clay. 相似文献
6.
Wildfires are a cause of soil water repellency (hydrophobicity), which reduces infiltration whilst increasing erosion and flooding from post-fire rainfall. Post-fire soil water repellency degrades over time, often in response to repeated wetting and drying of the soil. However, in mountainous fire-prone forests such as those in the Western USA, the fire season often terminates in a cold and wet winter, during which soils not only wet and dry, but also freeze and thaw. Little is known about the effect of repeated freezing and thawing of soil on the breakdown of post-fire hydrophobicity. This study characterized the changes in hydrophobicity of Sierra Nevada mountain soils exposed to different combinations of wet–dry and freeze–thaw cycling. Following each cycle, hydrophobicity was measured using the Molarity of Ethanol test. Hydrophobicity declined similarly across all experiments that included a wetting cycle. Repeated freezing and thawing of dry soil did not degrade soil water repellency, but freeze–thaw cycles decreased hydrophobicity in wet soils. Total soil organic matter content was not different between soils of contrasting hydrophobicity. Macroscopic changes such as fissures and cracks were observed to form as soil hydrophobicity decayed. Microscopic changes revealed by scanning electron microscope imagery suggest different levels of soil aggregation occurred in samples with distinct hydrophobicities, although the size of aggregates was not clearly correlated to the change in water repellency due to wet–dry and freeze–thaw cycling. A 9-year climate and soil moisture record from Providence Critical Zone Observatory was combined with the laboratory results to estimate that hydrophobicity would persist an average of 144 days post-fire at this well-characterized, typical mid-elevation Sierra Nevada site. Most of the breakdown in soil water repellency (79%) under these climate conditions would be attributable to freeze–thaw cycling, underscoring the importance of this process in soil recovery from fire in the Sierra Nevada. 相似文献
7.
Michael Rinderer Andrea Kollegger Benjamin M. C. Fischer Manfred Stähli Jan Seibert 《水文研究》2012,26(26):4112-4120
While soil moisture patterns can be interesting traits to investigate spatio‐temporal heterogeneity of catchments relevant for various physical processes of soil–atmosphere interaction and soil water redistribution, many of the existing methods to capture spatial patterns are time consuming, expensive or need site‐specific calibration. In this study we present a quick and inexpensive supplementary field method for classifying soil wetness in wet environments. The seven wetness classes are based on qualitative indicators, which one can touch, hear or see on the soil surface. To counter critics that such qualitative methods are considerably affected by subjectivity, we performed systematic testing of the method by taking qualitative measurements in the field with 20 non‐expert raters. We then analyzed these in terms of degree of agreement and assessed the results against gravimetric sampling and time domain reflectometry measurements. In 70% of all classifications raters agreed on the wetness class assigned to the marked sampling locations and in 95% they were not off by more than one wetness class. The seven quantitative wetness classes agreed with gravimetric and time domain reflectometry measurements, although intermediate to wet classes showed an overlap of their range whereas the driest classes showed considerable spread. Despite some potential to optimize the method, it has been shown to be a reliable supplement to existing quantitative techniques for assessing soil moisture patterns in wet environments. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
8.
The effects of wellbore‐wall compression from rough excavation on monitored groundwater levels and qualities under natural hydraulic gradient conditions were investigated in a shallow clayey Andisol aquifer. Nine wellbores reaching the underlying aquitard at about 2.6‐m depth were constructed by dynamic cone penetrometry to mimic rough wellbore construction. Five of these were constructed under wet aquifer soil conditions and the remaining four under dry conditions. A 15‐month period monitoring showed that the groundwater levels in the wellbores constructed under wet conditions responded significantly in retard of, and in narrower ranges than, those constructed under dry conditions. The wellbore‐wall hydraulic conductivities at the former wellbores were calculated to be more than one to two orders of magnitude lower than those at the latter ones. Furthermore, remarkable nitrate removal attributable to the occurrence of a heterotrophic denitrification was observed in one of the former wellbores. In contrast, the groundwater levels and qualities in the latter wellbores appeared to be generally similar to those monitored in the conventional soil coring and augering‐derived wellbores. Our results suggest that the wellbore‐wall compression induced by rough excavation under wet and soft aquifer soil conditions leads to a substantial decrease in the wellbore‐wall hydraulic conductivity, which in turn can lead to unreliable groundwater levels and qualities. This problem can occur in clayey Andisols whenever the aquifer soil is wet; however, the problem can be largely avoided by constructing the wellbore under dry and hard aquifer soil conditions. 相似文献
9.
The devastating impacts of the widespread flooding and landsliding in Puerto Rico following the September 2017 landfall of Hurricane Maria highlight the increasingly extreme atmospheric disturbances and enhanced hazard potential in mountainous humid-tropical climate zones. Long-standing conceptual models for hydrologically driven hazards in Puerto Rico posit that hillslope soils remain wet throughout the year, and therefore, that antecedent soil wetness imposes a negligible effect on hazard potential. Our post-Maria in situ hillslope hydrologic observations, however, indicate that while some slopes remain wet throughout the year, others exhibit appreciable seasonal and intra-storm subsurface drainage. Therefore, we evaluated the performance of hydro-meteorological (soil wetness and rainfall) versus intensity-duration (rainfall only) hillslope hydrologic response thresholds that identify the onset of positive pore-water pressure, a predisposing factor for widespread slope instability in this region. Our analyses also consider the role of soil-water storage and infiltration rates on runoff generation, which are relevant factors for flooding hazards. We found that the hydro-meteorological thresholds outperformed intensity-duration thresholds for a seasonally wet, coarse-grained soil, although they did not outperform intensity-duration thresholds for a perennially wet, fine-grained soil. These end-member soils types may also produce radically different stormflow responses, with subsurface flow being more common for the coarse-grained soils underlain by intrusive rocks versus infiltration excess and/or saturation excess for the fine-grained soils underlain by volcaniclastic rocks. We conclude that variability in soil-hydraulic properties, as opposed to climate zone, is the dominant factor that controls runoff generation mechanisms and modulates the relative importance of antecedent soil wetness for our hillslope hydrologic response thresholds. 相似文献
10.
The partially decomposed organic layer (duff: F and H layers) of the forest floor is an important boundary between the soil and atmospheric processes. Here we use both empirical data and a three‐dimensional coupled heat and water budget model to explain the duff hydrological hillslope shift between very brief wet periods when lateral flow in the duff and infiltration into the mineral soil occur and dry periods when evaporative flow dominates and both lateral and mineral soil flow are not important. The duff moisture transitions from wet to dry periods were the result of low lateral flow which moves liquid and water vapour only centimetres to metres, very rapidly and mostly in the H layer immediately after precipitation. During wet periods, the net lateral fluxes were negative on divergent areas and positive on convergent areas of the hillslope, leading to a net moisture loss in divergent areas and a net gain in convergent areas. The response to lateral flow in the H layer was more rapid than in the F layer. The transition from the lateral downwards flow to mineral soil to evaporative control was within approximately 48 h of precipitation. Canopy species and aspect were important with lodgepole pine, southwest aspect and 4‐cm deep duff controlled by evaporative processes while Engelmann spruce, northeast aspect and 30‐cm duff were more controlled by hillslope redistribution processes. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
11.
Soil moisture states,lateral flow,and streamflow generation in a semi‐arid,snowmelt‐driven catchment
Hydraulic connectivity on hillslopes and the existence of preferred soil moisture states in a catchment have important controls on runoff generation. In this study we investigate the relationships between soil moisture patterns, lateral hillslope flow, and streamflow generation in a semi‐arid, snowmelt‐driven catchment. We identify five soil moisture conditions that occur during a year and present a conceptual model based on field studies and computer simulations of how streamflow is generated with respect to the soil moisture conditions. The five soil moisture conditions are (1) a summer dry period, (2) a transitional fall wetting period, (3) a winter wet, low‐flux period, (4) a spring wet, high‐flux period, and (5) a transitional late‐spring drying period. Transitions between the periods are driven by changes in the water balance between rain, snow, snowmelt and evapotranspiration. Low rates of water input to the soil during the winter allow dry soil regions to persist at the soil–bedrock interface, which act as barriers to lateral flow. Once the dry‐soil flow barriers are wetted, whole‐slope hydraulic connectivity is established, lateral flow can occur, and upland soils are in direct connection with the near‐stream soil moisture. This whole‐slope connectivity can alter near‐stream hydraulics and modify the delivery of water, pressure, and solutes to the stream. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
12.
Infiltration into frozen soil plays an important role in soil freeze–thaw and snowmelt-driven hydrological processes. To better understand the complex thermal energy and water transport mechanisms involved, the influence of antecedent moisture content and macroporosity on infiltration into frozen soil was investigated. Ponded infiltration experiments on frozen macroporous and non-macroporous soil columns revealed that dry macroporous soil produced infiltration rates reaching 103 to 104 mm day−1, two to three orders of magnitude larger than dry non-macroporous soil. Results suggest that rapid infiltration and drainage were a result of preferential flow through initially air-filled macropores. Using recorded flow rates and measured macropore characteristics, calculations indicated that a combination of both saturated flow and unsaturated film flow likely occurred within macropores. Under wet conditions, regardless of the presence of macropores, infiltration was restricted by the slow thawing rate of pore ice, producing infiltration rates of 2.8 to 5.0 mm day−1. Reduced preferential flow under wet conditions was attributed to a combination of soil swelling, due to smectite-rich clay (that reduced macropore volume), and pore ice blockage within macropores. In comparison, dry soil column experiments demonstrated that macropores provided conduits for water and thermal energy to bypass the frozen matrix during infiltration, reducing thaw rates compared with non-macroporous soils. Overall, results showed the dominant control of antecedent moisture content on the initiation, timing, and magnitude of infiltration and flow in frozen macroporous soils, as well as the important role of macropore connectivity. The study provides an important data set that can aid the development of hydrological models that consider the interacting effects of soil freeze–thaw and preferential flow on snowmelt partitioning in cold regions. 相似文献
13.
This study examines the effect of water repellency on controlling temporal variability of runoff generation mechanisms and soil detachment on metamorphic derived soils under dry‐Mediterranean climate. The research is carried out in an unburnt Mediterranean hillslope in souther Spain characterized by a patchy vegetation pattern and shallow soils. The Water Drop Penetration Time test (WDPT) is applied to measure water repellency at the end of summer (Sep‐2008), mid autumn (Nov‐2008) and mid winter (Feb‐2009). Rainfall simulations were used to obtain runoff generation and soil detachment in the same periods of time. The main shrub specie is Cistus monspeliensis which leaves a load of litter during the summer due to the lack of water. This great amount of organic material is accumulated under the shrubs triggering an extreme water repellence (WDPT > 6,000 s) that limits infiltration processes. This process is enforced due to the low soil water content at the end of dry season. Certain water repellency (WDPT > 1,500 s) is also observed on bare soil as consequence of their sandier texture and the accumulation of annual plants which die at the end of the wet season. Soil moisture increases during the autumn and water repellency disappears in both shrub and bare soil at the middle of the wet season (WDPT < 5 s). The main consequence is that the temporal trend of water repellency controls the mechanism and frequency of runoff generation and, hence, soil detachment. At the end of the summer, Hortonian mechanisms predominates when water repellency is extreme, even in soils under Cistus monspeliensis where runoff generation can reach higher peaks of overland flow and sediment concentration. Conversely, only the saturation of soil could generate runoff during the wet season being this quite less frequent in bare soil and absent in shrub. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
14.
基于鄱阳湖南矶山湿地土壤及藜蒿Cd、As污染风险评价,利用盆栽实验研究水分条件对区域土壤理化性质、砷镉形态及其上生长的藜蒿(Artemisia selengensis)重金属富集能力的影响.结果表明:土壤Cd含量超标,存在生态风险,藜蒿茎中As含量达食品污染限量标准,存在食用风险;藜蒿对Cd、As的富集能力受土壤水分环境影响,水分增加会造成土壤pH与有机质含量上升,抑制藜蒿富集Cd的同时促进富集As.线性回归计算显示土壤有效态As含量与藜蒿As富集量呈显著正相关,可以用来评价藜蒿As富集情况,而土壤有效态Cd含量与藜蒿Cd富集量间无显著相关性.结合区域土壤Cd、As污染情况,适宜控制水分为缺水或旱湿交替条件,可以降低藜蒿等湿地植物中Cd的富集量;适宜控制水分为淹水条件,可以减少土壤Cd、As有效态含量. 相似文献
15.
Abstract Wetting front instability (fingered flow) accelerates solute transport through the unsaturated zone to the groundwater table. Whether fingers widen or dissipate close to the groundwater is unclear. Water flow in a two-dimensional artificial capillary fringe below a dry layer exhibiting fingered flow was investigated. The flow diverged strongly in the wet soil, suggesting that fingers dissipate. Expressions for the finger radius in dry and wet soil were combined and adapted to a soil hydraulic property parameterization popular in numerical modelling. The modified equation provided finger radii for soils in humid and arid climates. The fingers in the arid soil were excessively wide. The finger radii were used to model solute transport, assuming fingers dissipated in the subsoil. Modelling was cumbersome for the arid climate. One shower may often be insufficient to trigger fingering in arid regions with short, heavy showers. In soils with shallow groundwater, the diverging subsoil flow determines solute leaching. 相似文献
16.
The effect of conservation practices in sloped croplands on soil hydraulic properties and root‐zone moisture dynamics 下载免费PDF全文
下载免费PDF全文 Rain‐induced erosion and short‐term drought are the two factors that limit the productivity of croplands in the red soil region of subtropical China. The objective of this study was to estimate the effects of conservation practices on hydraulic properties and root‐zone water dynamics of the soil. A 3‐year experiment was performed on a slope at Xianning. Four treatments were evaluated for their ability to reduce soil erosion and improve soil water conditions. Compared with no practices (CK) and living grass strips (GS), the application of polyacrylamide (PAM) significantly reduced soil crust formation during intense rainfall, whereas rice straw mulching (SM) completely abolished soil crust formation. The SM and PAM treatments improved soil water‐stable aggregates, with a redistribution of micro‐aggregates into macro‐aggregates. PAM and SM significantly increased the soil water‐holding capacity. These practices mitigated the degradation of the soil saturated hydraulic conductivity (Ks) during intense rainfalls. These methods increased soil water storage but with limited effects during heavy rainfalls in the wet period. In contrast, during the dry period, SM had the highest soil water storage, followed by PAM and CK. Grass strips had the lowest soil water storage because of the water uptake during the vigorous grass growth. A slight decline in the soil moisture resulted in a significant decrease in the unsaturated hydraulic conductivity (Ku) of the topsoil. Therefore, the hydraulic conductivity in the field is governed by soil moisture, and the remaining soil moisture is more important than improving soil properties to resist short‐term droughts. As a result, SM is the most effective management practice when compared with PAM and GS, although they all protect the soil hydraulic properties during wet periods. These results suggest that mulching is the best strategy for water management in erosion‐threatened and drought‐threatened red soils. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
17.
In semiarid ecosystems, the transfer of water, sediments, and nutrients from bare to vegetated areas is known to be crucial to ecosystem functioning. Rainfall simulation experiments were performed on bare‐soil and vegetated surfaces, on both wet and dry soils, in semiarid shrub‐steppe landscapes of SE Spain to investigate the spatial and temporal factors and interactions that control the fine‐scale variation in water infiltration, runoff and soil loss, and hence the water and sediment flows in these areas. Three types of shrub‐steppe landscapes varying in plant community and physiography, and four types of plant patches (oak shrub, subshrub, tussock grass, and short grass mixed with chamaephytes) were studied. Higher infiltration and lower runoff and soil loss were measured on vegetation patches than on bare soils, for both dry and wet conditions. The oak‐shrub patches produced no runoff, while the subshrub patches showed the highest runoff and soil loss. Despite these differences among patch types, the influence of vegetation patch type on the variables analysed was not significant. The response of bare soil surfaces clearly varied between landscape types, yet the differences were only relevant under dry soil conditions. Stone cover, particularly the cover of embedded stones, and crust cover, were the key explanatory variables for the hydrological behaviour of bare soils. The study documents quantitatively how bare soils and vegetation patches function as runoff sources and runoff sinks, respectively, for a wide range of soil moisture conditions, and illustrates that landscape‐type effects on bare‐soil runoff sources may also exert an important control on the site hydrology, while the role of the vegetation patch type is less important. The effects of the control factors are modulated by antecedent soil moisture, with dry soils showing the most contrasting soil water infiltration between landscapes and surface types. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
18.
Extended severe dry and wet periods are frequently observed in the northern continental climate of the Canadian Prairies. Prairie streamflow is mainly driven by spring snowmelt of the winter snowpack, whilst summer rainfall is an important control on evapotranspiration and thus seasonality affects the hydrological response to drought and wet periods in complex ways. A field‐tested physically based model was used to investigate the influences of climatic variability on hydrological processes in this region. The model was set up to resolve agricultural fields and to include key cold regions processes. It was parameterized from local and regional measurements without calibration and run for the South Tobacco Creek basin in southern Manitoba, Canada. The model was tested against snow depth and streamflow observations at multiple scales and performed well enough to explore the impacts of wet and dry periods on hydrological processes governing the basin scale hydrological response. Four hydro‐climatic patterns with distinctive climatic seasonality and runoff responses were identified from differing combinations of wet/dry winter and summer seasons. Water balance analyses of these patterns identified substantive multiyear subsurface soil moisture storage depletion during drought (2001–2005) and recharge during a subsequent wet period (2009–2011). The fractional percentage of heavy rainfall days was a useful metric to explain the contrasting runoff volumes between dry and wet summers. Finally, a comparison of modeling approaches highlights the importance of antecedent fall soil moisture, ice lens formation during the snowmelt period, and peak snow water equivalent in simulating snowmelt runoff. 相似文献
19.
Effects of the roots of Cynodon dactylon and Schefflera heptaphylla on water infiltration rate and soil hydraulic conductivity 总被引：2，自引：0，他引：2 下载免费PDF全文
下载免费PDF全文 Water infiltration rate and hydraulic conductivity in vegetated soil are two vital hydrological parameters for agriculturists to determine availability of soil moisture for assessing crop growths and yields, and also for engineers to carry out stability calculations of vegetated slopes. However, any effects of roots on these two parameters are not well‐understood. This study aims to quantify the effects of a grass species, Cynodon dactylon, and a tree species, Schefflera heptaphylla, on infiltration rate and hydraulic conductivity in relation to their root characteristics and suction responses. The two selected species are commonly used for ecological restoration and rehabilitation in many parts of the world and South China, respectively. A series of in‐situ double‐ring infiltration tests was conducted during a wet summer, while the responses of soil suction were monitored by tensiometers. When compared to bare soil, the vegetated soil has lower infiltration rate and hydraulic conductivity. This results in at least 50% higher suction retained in the vegetated soil. It is revealed that the effects of root‐water uptake by the selected species on suction were insignificant because of the small evapotranspiration (<0.2 mm) when the tests were conducted under the wet climate. There appears to have no significant difference (less than 10%) of infiltration rates, hydraulic conductivity and suction retained between the grass‐covered and the tree‐covered soil. However, the grass and tree species having deeper root depth and greater Root Area Index (RAI) retained higher suction. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
20.
Boyd A. HUTCHISON 《水文科学杂志》2013,58(1):34-42
ABSTRACT During the spring of 1961, evaporation from snow and soil surfaces was measured in the central Rocky Mountains near Fraser, Colorado. Measurements were made in natural forest openings at 9,000 feet elevation. Evaporation from wet soil surfaces greatly exceeded evaporation from nearby snow. There was little evidence of transfer of vapor from soil to nearby patches of snow, but as areas of bare, wet soil increased and evaporation amounts from such surfaces increased, evaporation from snow decreased. It was concluded that, as greater amounts of water evaporated from soils, the vapor pressure of the air was raised sufficiently to reduce evaporation from snow. Since transfer of vapor from soil to snow appeared small at best, evaporation losses from snow and soil surfaces essentially constituted a total moisture loss from the area. 相似文献