seasonal changes in the hydrological and erosional response of a hillslope under dry mediterranean climatic conditions montes de malaga south of spain the mediterranean eco geomorphological system was analysed at one representative hillslope of the geological unit of montes de malaga province of malaga spain under dry mediterranean climatic conditions the research was divided into two stages first the eco geomorphological pattern of the slope and some physical properties of the soil were analysed second the hydrological and erosional response of the eco geomorphological system was analysed by applying simulated rainfall to the main elements of the system and using closed plots with different lengths this hydrodynamic analysis was carried out during two periods crucial for the mediterranean environment in hydrological terms the end of the dry season or the beginning of the active hydrodynamic season and the middle of the wet season the results show that i the hydrophobic behaviour of soil is the predominant runoff generation mechanism that accounts for sediment movement ii once soil was moistened in the wet season it lost its hydrophobicity and the saturation of soil became a predominant runoff generation mechanism and iii there was high variability in hillslope runoff with evident hydrological disconnections which made the hydrodynamic response of the eco geomorphological system complex due to the absence of a clear predominance of abiotic or biotic factors

estimating sea ice area flux across the canadian arctic archipelago using enhanced amsr e 1 enhanced resolution advanced microwave scanning radiometer amsr e imagery is used to estimate daily sea ice area fluxes between the canadian arctic archipelago and the arctic ocean and baffin bay for the period september 2002 to june 2007 over the period amundsen gulf and m clure strait exported 54 103 km2 of sea ice area or roughly 77 km3 of sea ice volume each year into the arctic ocean export import into the arctic ocean through the queen elizabeth islands is small and uncertain since no estimates for july and august could be made due to atmospheric attenuation of the microwave signal lancaster sound exported 68 103 km2 of sea ice area or roughly 102 km3 of ice volume into baffin bay this produced a net loss of sea ice area of about 122 103 km2 or roughly 174 km3 a 1 which is presumed to be generated from within the archipelago itself mainly through the stationary and transient polynyas and leads that form each winter daily ice area fluxes for amundsen gulf ag and lancaster sound ls were as high as 2500 km2 d 1 and were event driven depending on synoptic scale atmospheric circulation and the mobility of the sea ice mean sea level pressure difference across each gate is moderately correlated with daily sea ice area fluxes despite the fact that free ice drift conditions are not always met in the region cross gradient and daily sea ice area flux for lancaster sound show a large number of counter gradient ice flux occurrences suggesting that local mesoscale winds nongeostrophic and perhaps ocean currents play a role in transporting sea ice through this gate monthly ice fluxes for the ag and ms gate were positively correlated with the ao index indicating that a strong beaufort sea high pressure and gyre correspond to more export into the beaufort sea monthly fluxes for the ls gate were positively correlated with the nao index indicating that strong southerly atmospheric circulation over baffin bay increases ice export into baffin bay from lancaster sound

magnitude frequency analysis of water redistribution along a climate gradient in spain abstract banded patterns in soils and vegetation form part of important discontinuities on semi arid slopes in spain at fine scales

the effects of fire and water repellency on infiltration and runoff under mediterranean type forest abstract an investigation is being made into the relationship between forest fire and hillslope hydrology in the selva region of catalonia over a three year period at sites with a known fire history the major sites are on granite granodiorite or on sediments derived from these rocks at locations between santa christina d aro and santa coloma de farnes it appears that there is a general relationship between the type of organic profile found in a forest and the impact of fire in terms of loss of organic matter soil erosion hillslope hydrology and on the regeneration of the forest this paper summarises the results of about 150 rainfall simulation experiments and presents an overview of work carried out so far a major conclusion is that runoff processes are discontinuous and spatially structured due mainly to the effects of water repellency as a result of surface properties macropores hydrophobic behaviour and swelling four types of infiltration curve can be recognised at many locations infiltration increases with time during the early part of an experiment reaches a maximum value after about 30 minutes therupon subsequently decreasing this type of relationship can not be modelled with standard infiltration equations illustrations are given of sections through both burnt and unburnt soils to show how the hydrophobic effect influences water penetration it can be seen that infiltration patterns are similar for both burnt and unburnt soils and that micropores filled with organic matter are very important in conducting water through a water repellent surface layer the hydrophobic layer traps water in the bc horizon and prevents evaporation and loss by upwards capillary movement although the hydrophobic effects mean that small areas sometimes have a high runoff coefficient on larger areas there are many macropores and shrubs beneath which the soil is permeable and these trap runoff generated on the water repellent areas the main effect of fire is to illiminate the storage of water in the organic horizons several cm at first infiltration rates remain high but later these decrease as there is a reduction in porosity the sites having a moder type profile have better water retention properties more organic matter that survives the fire and a faster rate of vegetation recovery sites with a mor type profile can be degraded and erode if they are subject to disturbance the study provides another example of how on seemingly uniform slopes hydrological processes are structured by interactions with vegetation the patterns produced by these interactions survive the effects of fire

formation processes of framboidal pyrite abstract pyrite framboid formation may be the result of four consecutive processes 1 nucleation and growth of initial iron monosulfide microcrystals 2 reaction of the microcrystals to greigite fe 3 s 4 3 aggregation of uniformly sized greigite microcrystals i e framboid growth and 4 replacement of greigite framboids by pyrite the uniform morphology uniform size range and ordering of the microcrystals in individual framboids as well as the range of observed framboid structures from irregular aggregates to densely packed spherical aggregates and polyframboids are consequences of these processes using dlvo theory derjaguin landau verwey and overbeek we have evaluated the stability of colloidal iron monosulfide suspensions with ionic strengths typical of marine and lacustrine waters in addition to van der waals attractive and double layer repulsive forces a term is included to account for the ferrimagnetic properties of greigite numerical models predict that magnetically saturated greigite particles 0 1 m in diameter will rapidly aggregate in either marine or fresh water the aggregation model is in agreement with the sequence of greigite formation followed by pyrite framboid formation established in a previous experimental study sweeney and kaplan 1973 and is consistent with the occurrence of framboids composed of other magnetic minerals e g greigite magnetite and magnesioferrite based on the temperature dependent magnetic properties of greigite and aging experiments in hydrothermal solutions this mechanism for framboid formation via precursor greigite could operate to temperatures of 200 c consistent with the occasional occurrence of pyrite framboids in the paragenesis of metalliferous ore deposits

effects of soil surface components on soil hydrological behaviour in a dry mediterranean environment southern spain abstract various researchers have studied the spatial pattern of soil surface components such as vegetation rock fragments bare soil litter and surface crusts as a key factor of hydrological behaviour in mediterranean settings with heterogeneous patches of vegetation cover and strong human impact the studies indicate that there is a mosaic of patches that generate run off or infiltrate overland flow distributed in various ways along hillslopes few of these studies however have looked at areas underlain by metamorphic rocks such as phyllites or schists this study analysed the temporal and spatial variability of the effects of soil surface components on hydrological processes in a small dry mediterranean catchment underlain by metamorphic rocks a systematic sampling of multiple sites throughout a hydrological year was carried out we related the hydrological behaviour of soil surface components to 1 their position along the hillslope 2 the distance of existing vegetation tussocks from the line of run off 3 rainfall intensity and 4 the main physical chemical soil properties affecting infiltration processes statistical analysis was used to check the validity of the relationships the results show that soil surface components have highly variable effects in both space and time on soil hydrological behaviour these effects particularly depend on the location along the line of maximum slope and the intensity of preceding rainfall whose interaction defines soil hydrological status these results are similar to those for other mediterranean settings with different lithology in that the succession of contributing patches are hydrologically interconnected along a hillslope the variables used and the grouping of explanatory variables through principal component analyses were found to be suitable for discussing the spatial distribution of soil surface components in the hydrologically dynamic environment of the study area

effects of soil and vegetation on runoff along a catena in semi arid spain runoff and infiltration were investigated on abandoned fields of patchy vegetation in semi arid spain during 15 months of natural rainfall and by rainfall simulations the aim was to ascertain sources and sinks of runoff and the effects of soils and plant cover soils of the catena developed from mica schists of the upper hillslopes fan deposits of the lower hillslopes and an alluvial terrace at the bottom runoff from natural events were from three sets of three pairs each of 10 2 m runoff plots the pairs of each set had different densities of plant cover the sets were vegetated with tussock grass stipa tenacissima a shrub anthyllis cytisoides and a bush retama sphaerocarpa nineteen natural rainfall events of intensities up to 18 mm h produced 400 mm of rain during the study period because the rainfall threshold for runoff production was about 20 mm only eight events produced runoff the rainfall simulations used a sprinkler that produced 50 mm h of rain for 30 minutes runoff was recorded each minute in 0 24 m2 bounded plots the depth and structure of the soil mantle provide the main controls on runoff rates which are lowest on the lower fan deposits and highest on the thin upslope soils the river bank terrace with a surface covered by crusts and mosses also yields relatively high runoff in general vegetation density varies inversely with runoff nevertheless shrub and bush litter favor runoff as does a particular spatial distribution of individual plants on the hillslope settling of the upper few centimeters of soils of the alluvial fan following cessation of cultivation 15 to 40 years ago has produced a near surface compacted layer favoring shallow subsurface runoff apparently contradictory results between runoff plots and rainfall simulations are the result of differing processes

early diagenetic pyrite morphology in a mudstone dominated succession the lower jurassic cleveland ironstone formation eastern england abstract diagenetic pyrite in the mudstones and ironstones of the lower jurassic cleveland ironstone formation of eastern england exhibits two distinct morphologies framboidal pyrite commonly associated with organic matter and euhedral pyrite associated with detrital clay pellets these two morphologies are mutually exclusive in occurrence framboidal pyrite is present in clay rich mudstones ooidal ironstones apatite rich units and some silt rich mudstones euhedral pyrite is present in silt rich and sand rich mudstones 34s isotopic analysis of six samples of pyrite suggests that both types of pyrite morphology precipitated during early diagenesis from porewaters with open access to overlying sea water although both probably acted as sites for continued pyrite precipitation during burial it is proposed that framboidal pyrite precipitated from iron dominated porewaters at sites of sulfide supply i e in the region of organic matter as a result of bacterial sulfate reduction where locally sulfide production rates were high enough for porewaters to reach supersaturation with respect to fes euhedral pyrite also precipitated from iron dominated porewaters but sulfide production rates from organic matter was such that fes saturation was not reached at the sites of sulfide production instead euhedral pyrite was precipitated directly from porewater when fes2 saturation was reached the control over pyrite morphology was probably the amount and reactivity of the organic matter within the deposited sediments the sand rich mudstones contained less reactive organic matter due to clastic dilution and deposition in shallower environments with o2 rich bottom waters the ironstones and apatite rich units were deposited under very low sedimentation rates and as a result organic matter contents were very low and iron reduction dominated early diagenesis which inhibited sulfate reduction the presence of minor framboidal pyrite within these units however suggests that sulfide reduction took place in micro environments during early diagenesis

framboidal and idiomorphic pyrite in the upper maastrichtian sedimentary rocks at gabal oweina nile valley egypt formation processes oxidation products and genetic implications to the origin of framboidal pyrite abstract the upper maastrichtian organic rich sediments studied at gabal oweina egypt are moderately enriched in syngenetic and diagenetic pyrite pyrite occurs mostly as layers or bands group of lamina lenses diagenetic intercalated pockets burrow fills and disseminated individual pyrite framboids and crystals within the host sediments the pyritic thin bands and lamina consist mostly of unconsolidated to compact oriented pyrite oriented along the bedding planes in gypsiferous clayey matrix and less common as poorly oriented pyrite crystallites in several cases pyrite crystals of the latter type depict zoning fracturing and micro concretions pyritic burrow fills are composed mainly of pyrite phosphatic ooids microfossils glauconitic grains poorly graphitized carbon and native sulfur pyrite replaces minerals other than gypsum sulfur or carbon it also replaces microfossils thus turning some of the phosphatic ooids and microfossils to pyritized pseudomorphs none of the studied phosphate ooids or framboids contains any mackinawite pyrrhotite or greigite based on the microscopic and sem observations of the micro textures of disseminated pyrite found at gabal oweina section four morphological forms of primary pyrite could be identified 1 grouped multiple framboids 2 individual framboids 3 pyrite idiomorphic crystal overgrowths on framboids and 4 single and aggregates of euhedral pyrite crystals the multiple framboid formation may have emerged from three successive processes nucleation and growth of individual aggregates of the microcrystals to form combined micro framboids the growth of framboids and followed by grouping of the several pyrite framboids direct pyrite nucleation shell formation crystallization and aggregation processes might complete a single framboid the disseminated single and aggregated euhedral pyrite crystals bear evidence indicating that their formation was via nucleation and growth of pyrite crystallites and their aggregation to individual framboids infilling in the interstices by additional pyritic material compaction and homogenization of all these materials furthermore we encounter for the first time in nature idiomorphic pyrite crystals that integrated numerous framboids using them as their nucleation and growth sites without erasing or modifying their pristine morphology elemental sulfur contains minor concentration of sb ni cd and cu strongly suggesting their presence as submicron sulfide crystallite inclusions sem and microprobe investigations revealed that goethite is present as a weathering product in all morphological types of pyrite however only an iron sulfate presumably melanterite was encountered as oxidation product of the multi framboids and the euhedral aggregate crystals the upper maastrichtian sediments not only contain a menagerie of pyrite morphologies but probably a complete record of the formation process and the geochemical conditions of the growth of framboids single pyrite crystals pyrite burrows pyritized mn fe oxide framboids and finally their weathered products the various pyrite forms strongly suggest a multistage process that led to their formation without any evidence for mackinawite pyrrhotite or greigite precursors there is also no evidence in the oweina sediments for post pyrite formation of mackinawite pyrrhotite or greigite the presence of elemental sulfur containing minor concentrations of sb ni cd and cu with pyrite framboids indicates that the pore solutions were geochemically supersaturated in sulfur thus inhibiting the crystallization of any iron sulfide other than pyrite this cast considerable doubt on the assumed mackinawite or greigite precursors as prerequisite for formation of pyrite framboids

a sediment fingerprinting approach to understand the geomorphic coupling in an eastern mediterranean mountainous river catchment article i nfo article history to understand the response of a river to anthropogenic disturbance knowledge of the links between erosion sed iment deposition and sediment export iscrucial therefore starting from field observations and connectivity prox ies a sediment fingerprinting approach using geochemical tracers was used to elucidate the subrecent sediment dynamics in the 264 km 2 bugduz river catchment in sw turkey a topography based connectivity index was used as a proxy for hillslope channel coupling and stream power estimations as a proxy for the within channel connectivity quantitative provenance information providesa link between potential sediment sources and the de rived sediment currently stored within the fluvial system provenance signals from both contemporary river bed sediments n 144 and subrecent floodplain deposits n 2 8 provide more insight into the coupling of the hillslopes to the river channel and the coupling within the river channel itself furthermore comparing the prov enance signal with the areal extent of potential sediment sources upstream in the form of enrichment ratios sheds light upon the variation of the erodibility of the sources andthe connectivity within the catchment results indicate that the valleygradient exerts an important control on the spatial variability of geomorphic coupling in the bugduz catchment furthermore different sediment sources lithologies show distinct sediment production rates in ad dition to the observed spatial variability coupling relations are characterized by an important seasonal variation indicated by variable contributions of local and more distant sediment sources

the influence of geomorphological position and vegetation cover on the erosional and hydrological processes on a mediterranean hillslope soil erosion and runoff rates are assumed to be highly dependent on slope position however little knowledge exists about the hydrogeomorphological processes at the pedon scale that support this idea in order to assess the hydrological and erosional behaviour of soils at different slope positions simulated rainfall experiments 55 mm was applied during one hour were carried out on a south facing slope with underlying limestone in south east spain in the mean terms the erosion rates 9 g m2 hr 1 and the runoff coefficients 12 were very low at the scale of measurement 0 25 m2 the slope position does not affect erosion rates when the measurements are carried out under extreme dry conditions during summer the low runoff rates found in summer under thunderstorms of high intensity 5 year return period and the runon into surfaces with higher infiltration rates resulted in no detectable direct surface runoff hortonian at the slope scale this implies that erosion as a consequence of surface overland flow will only take place during events of high magnitude 55 mm hr 1 and low frequency 5 years vegetation is the most important factor determining the soil erosion and runoff rates within the slope 1998 john wiley sons ltd

differential responses of hillslope and channel elements to rainfall events in a semi arid area the degree of hydrological connectivity of hillslope elements in a semi arid climate was studied at the season and event timescales field data were obtained in rambla honda a medalus project field site situated in se spain on micaschist bedrock and with 300 mm annual rainfall the season timescale was assessed using correlation analysis between soil moisture and topographic indices the event timescale was studied by a quasi continuous monitoring of rainfall soil moisture runoff and piezometric levels results show that widespread transfers of water along the hillslope are unusual because potential conditions for producing overland flow or throughflow are spatially discontinuous and extremely short lived during extreme events runoff coefficients may be locally high ca 40 on slope lengths of 10 m but decrease dramatically at the hillslope scale 10 on slope lengths of 50 m two mechanisms of overland flow generation have been identified infiltration excess and local subsurface saturation from upper layers the former occurs during the initial stages of the event while the latter which is quantitatively more important takes place later and requires a certain time structure of rainfall intensities that allow saturation of the topsoil and the subsequent production of runoff hillslopes and alluvial fans function as runoff sources and sinks respectively permanent aquifers are lacking in rambla honda variable proportions of hillslope areas may contribute to flash floods in the main channel but their contribution to the formation of saturated layers within the sediment fill is very limited

hydrological influences on the resilience of quercus spp dominated geoecosystems in central spain differences in vegetation cover within a landscape having a similar land use history can be used to identify differences in recovery following disturbance according to landscape position the objective of this study was to determine the resilience of oak dominated communities at different landscape positions in a research area in central spain as indicated by the relative recovery of quercus ilex and q coccifera and to relate this to the most important hydrological processes and properties at the slope sections scale the results indicate that the geoecosystems on slope sections on north facing slopes are more resilient than those on south facing slopes on the more degraded shrubland sites the higher values of vegetation cover on the lower slope sections indicate the systems on these slope sections to be more resilient than those on the slope sections located higher up the slope the hydrological factors that could possibly explain differences in vegetation type and cover were found to be distance to water resources at greater depths and incoming radiation controlling evapotranspiration a conceptual model is presented that links the resilience of these systems to the hydrological conditions on the basis of the presented model it is postulated that recovery of the system is determined partly by access to deep water resources it is suggested that differences in or degree of access to such water resources may cause these comparably looking systems to react differently to degradation and recovery

eco geomorphological system response variability to the 2004 06 drought along a climatic gradient of the littoral betic range southern spain abstract one of the main characteristics of the mediterranean climate is the high frequency of droughts which last for a year or more and the appearance of dry spells within the wet season the littoral betic range in the south of the iberian peninsula shows a significant climatic gradient from the straits of gibraltar 1600 mm year 1 to the cabo de gata 150 mm year 1 these differences in climatic conditions result in variations in the elements of the eco geomorphological system at the hillslope scale this study aimed to analyse the immediate consequences of a two year drought period 2004 06 on several elements of the mediterranean eco geomorphological system on three hillslopes under different climatic conditions sub humid dry mediterranean and semi arid the soil water content the pattern of vegetation and some soil properties organic matter content aggregate stability and permeability were analysed before nov 2003 and during nov 2005 the drought period the most important findings were i a reduction in the soil water content which reached values below the wilting point in the wet seasons affecting negatively the water available for vegetation especially in the wettest sites ii a reduction in vegetation cover and the number of plants especially on semi arid field sites iii changes in the organic matter content which aggravate the loss of stability of soil aggregates a process seen more clearly under more arid conditions and iv a reduction of soil permeability in all situations in the climate gradient studied which supposes a priori an increase in erosive processes due to surface runoff these results indicate increased vulnerability of the eco geomorphological system because of the rainfall drought situation

soil erosion and hydrology of the western mediterranean badlands throughout rainfall simulation experiments a review abstract rainfall simulation experiments are widely used in geomorphological research in badland areas this technique contributed significantly to our understanding of badland geomorphology in the mediterranean belt due to the different types of simulated rainfall applied and the variable size of the plots a review of the state of the art is necessary this study confirmed that rainfall simulations are well suited to i analyse runoff infiltration processes and sediment detachment within badlands and ii to establish the factors determining the hydrological and erosion response at interrill scale in badland areas the hydrological response of badlands is characterized by rapid responses low to moderate infiltration rates ranging from close to 0 to 55 mm h 1 and high runoff coefficients i e 60 positive relationships are observed between antecedent soil moisture content and rainfall intensity on the one hand and runoff coefficients on the other sediment concentration and soil detachment rates are among the highest measured on the mediterranean region i e up to 84 8 g l 1 and 4722 4 g m 2 h 1 results show that rainfall intensity runoff coefficient and slope angle have a positive influence on sediment concentration and sediment detachment in the case of rock fragment cover its influence is variable according to the soil cover percentage rainfall simulations increase our understanding of the temporal and spatial variability of the soil erosion processes however rainfall simulation provides mostly qualitative rather than quantitative information because of the small plot size and the simulated rainfall characteristics due to facility for repeating experiments and recording a high quantity of data in short time however this method allows the comparison amongst different environments and soil conditions as the rainfall properties can be reproduced

petrography of the neogene lignite from the sofia basin bulgaria abstract the lignite seam from the sofia neogene basin has been sampled and the petrographical composition was determined the coals contain high contents of macerals from the huminite group the prevailing macerals from that group were textinite ulminite and attrinite phlobaphinite densinite and gelinite were observed rarely dominant macerals from the liptinite group were mainly suberinite resinite sporinite and cutinite the amounts of the alginate liptodetrinite and fluorinate were insignificant the coal was very poor of macerals from the inertinite group fusinite semifusinite macrinite sclerotinite and inertodetrinite were represented them the main minerals were illite kaolinite halloyzite pyrite quartz calcite and dolomite anorthite amphibole augite chalcopyrite marcasite siderite witherite gypsum melanterite and jarosite were also determined the huminite maceral amount was highest in low part of the seam and lower in the middle part the higher amount of the liptinite macerals was located in the middle and upper parts of the seam inertinite macerals were distributed uniformly on the seam profile and their amount was very low in the middle part of the seam the middle part of the seam was contained highest amount of all minerals illite was prevailing clay mineral in the middle part and kaolinite predominates in the low and upper parts of the seam the type of the mire was determined as mesotrophic bog forest by calder et al bull soc geol fr 162 1991 283 according to the ground water index gwi and vegetation index vi calculated on the base of the maceral content according to the petrography content the gelification index gi and the tissue preservation index tpi the peat bog probably originated as a fresh water raised forest swamp

differences in hillslope runoff and sediment transport rates within two semi arid catchments in southeast spain this paper focuses on hillslope runoff and sediment transport within two catchments in southeast spain five monitoring sites were established on hillslope concavities throughout the two catchments the techniques used were mini crest stage recorders spray painted lines sediment traps and tipping bucket rain gauges established during previous research results show that a storm event in the rambla nogalte on 30 june 2002 of 83 0 mm was responsible for a maximum runoff depth of 12 cm and a maximum hillslope sediment transport of 1886 cm3 m 1 the same storm in the rambla de torrealvilla produced 53 4 mm of rainfall on the 1 july 2002 had a maximum runoff depth of 26 cm and resulted in 2311 cm3 m 1 of sediment transport there is evidence to suggest that measured sediment transport is related to runoff and a qualitative estimate of morphological runoff zones mrz sediment transport and depth of runoff varied dramatically with lithology marl sites produced most runoff and sediment transport followed by the sites of mixed red and blue schist then blue schist these results are important for understanding the behaviour of slopes and show that for short lived storms with high but not rare rainfall intensities and total rainfall amounts runoff can cause significant hillslope sediment transport in semi arid areas

fire and aspect induced differences on the erodibility and hydrology of soils at la costera valencia southeast spain this paper presents measurements of soil aggregation parameters and rainfall simulation experiments from areas of mediterranean scrubland vegetation in la costera district in the southern part of valencia province spain data were obtained using a portable rainfall simulator and from laboratory studies of aggregate stability using the water drop test and ultrasonic dispersion methods three locations were chosen to enable the influences of aspect and the post fire recovery time of the vegetation on soil erosion and hydrology to be investigated the slopes studied were a a north facing slope burnt ten years before the experiment b a south facing slope burnt at the same time and c a north facing slope burnt two years before the experiment similar to slope a in terms of its basic characteristics the experiments demonstrate the importance of both wildfires and aspect on hydrological and erosional soil surface processes the north facing slope at la costera slope a has a higher aggregate stability than the corresponding south facing slope slope b the recently burnt north facing slope c is intermediate in terms of aggregation but has the most erodible soils because of the lower infiltration rates and the low vegetation and litter cover nevertheless for the slopes burnt ten years previously the south facing slope is more erodible than the north facing one the results suggest that the forest fire ten years ago did not produce a persistent degradation of the ecosystem only higher soil and water losses during the first years following the fire a southern aspect where vegetation recovery rates are slower and the hydraulic stress is higher favours the development of soils with a relatively low aggregate stability

runoff generation sediment movement and soil water behaviour on calcareous limestone slopes of some mediterranean environments in southeast spain abstract an interpretation of soil hydrology and erosion data obtained from limestone areas in southeast spain is presented in the framework of recent hypotheses on runoff generation mechanisms in mediterranean environments the main objective is to synthesise and harmonise the data in theoretical concepts or behavioural models of hydrological functioning of mediterranean limestone slopes for this purpose data were collected in a typical limestone area with climatic characteristics ranging from subhumid to semiarid several sites were chosen with comparable slopes vegetation and soils along a transect of 20 km to carry out several research projects the data discussed in this paper consist of information on water redistribution within the soil profiles obtained from long duration up to 5 h rainfall simulation experiments with continuous monitoring of soil moisture at different depths runoff and sediment concentration data were obtained i from rainfall simulation experiments with different antecedent soil moisture conditions and ii as natural results from open gerlach plots on runoff and sediment movement over 4 years three conceptual models of water redistribution during the infiltration process could be observed two of them imply nonuniform water redistribution within the soil profile due mainly to macropore flow caused by specific soil surface characteristics at the plot scale runoff generated in bare patches is mainly hortonian in plots with previously wetted soils or soils with high infiltration capacities the generated runoff implies the saturation of the upper soil both types of runoff are discontinuous through time and space the runoff generation mechanisms at the slope scale have been synthesised into two conceptual models a hortonian discontinuous runoff model that takes place in the most degraded slopes or during high intensity rain events and a mixed runoff generation model in less degraded slopes or in previously wet soils where infiltration excess runoff as well as saturation excess runoff can happen on the same slope in both cases slopes behave as a patchwork of runoff and runon areas the size of the runoff or runon patches is dependent on the climatological conditions these control the hydrological disconnection between different parts of the slopes hortonian and saturation runoff can both be generated and infiltrated downslope

occurrence mechanism and prediction of rocky land degradation in karst mountainous basins with the aid of gis technology a study case in houzhai river basin in southwestern china rocky desertification is a severe ecological issue threatening and constraining regional sustainable development in karst mountainous areas like houzhai river basin in southwestern china the results indicate that slope gradient and altitude are closely associated with occurrence of rocky desertification in the study region and there are some significant correlations between rock outcrop and slope gradient r 0 363 p 0 001 and between rock outcrop and altitude r 0 0 336 p 0 001 slope gradient and altitude are key factors contributing to rocky desertification in the studied basin therefore special attention should be paid to sloping lands that have greater slope gradients or altitudes to prevent and control the rocky desertification in a karst mountainous basin as the houzhai river basin furthermore it might be possible to predict the occurrence of rocky desertification using neural networks on the basis of geographical characteristics and human disturbance the correlation coefficients between observed values and predicted values ranged from 0 728 to 0 905 with a mean value of 0 851 ten times repeats the present study also indicates that human disturbance has little effect on rocky desertification however further studies should be conducted to interpret the effects of agricultural activities on the occurrence of rocky desertification