Departamento de Cristalografía, Mineralogía y Química Agrícola. Facultad de Química. Universidad de Sevilla. C/profesor García González, 1 41010 - Sevilla Spain
Abstract: FUEGORED2009 is the second annual meeting of the “Red Temática Nacional Efectos de los Incendios Forestales sobre los Suelos”, an initiative of the National Plan I+D+I supported by the Spanish MInistry of Science and Innovation. This network is composed of many Spanish research groups that are dedicated to research to soils and environments affected by forest fires. Because of the worldwide relevance of this subject, there already exist considerable collaborations with many foreign research groups. Therefore, the goal of the present meeting is to offer a platform to exchange and discuss recent research efforts and ideas –both on a national and an international level– and to extract the research lines that needs to be followed in the future. A second goal of this meeting is to approach young scientists to become involved in and to contribute to this research area with their new ideas. With this in mind we sincerely welcome all the participants of the meeting, coming from all over Spain but also from abroad and are looking forward to dynamic and fruitful discussions with exchange of thoughts and ideas that move us forward. This meeting is organized under the auspices of the Consejo Superior de Investigaciones CientÃficas, the Universidad de Sevilla and the National Thematic Network FUEGORED, with the collaboration from the regional government (Junta de AndalucÃa) and and the Plenary of Cortegana.
Abstract: Water repellency (WR) from fire-affected soils can affect infiltration processes and increase runoff rates. We investigated the effects of fire-induced changes in soil WR and the related soil hydrological response after one of the largest wildfires in Spain in recent years. The vertical distribution of WR in soil profiles was studied under oak and pine forests and the wetting pattern was analyzed after rainfall simulations (85 mm h-1 during 60 minutes). After burning, the persistence of WR in soils under oaks increased in the upper 0-5 cm of soil in comparison with pre-fire WR, but no significant changes were observed under pines. After fire, WR was stronger and the thickness of the water repellent layer greatens in soils under pines in the upper 0-16 cm of soil. The hydrophobic layer was thinner under oaks, where no strong to extremely water repellent samples were observed below 12 cm (in burnt soils) and 8 cm (in unburnt soils). Uniform wetting was observed through soil depth in burnt and unburnt soils under oaks, as a consequence of the prevailing matrix flux infiltration. Water was mostly stored in the upper few centimetres and soil became rapidly saturated, favouring a continuous rise in the runoff rate during the experiments. Moisture profiles under pines showed a heterogeneous wetting pattern, with highly irregular wetting fronts, as a result of wettable and water repellent three-dimensional soil patches. In this case, runoff rates on burnt plots increased with relation to unburnt plots, but runoff generation reached a steady state after 25-30 minutes of simulated rainfall at intensity of 85 mm h-1. Rainfall water infiltrated over a small part of the ponded area, where the vertical pressure of the water column overcame the WR.
Abstract: Land use has significantly changed during the recent decades at global and local scale, while the importance of ecosystems as sources/sinks of C has been highlighted, emphasizing the global impact of land use changes. Land use changes can increase C loss rates which are extremely difficult to reverse, in the short term, opposite to organic carbon (OC) which accumulates in soil in the long-term. The aim of this research is to improve and test methodologies to assess land cover change (LCC) dynamics and temporal and spatial variability in C stored in vegetation at a wide scale. LCCs between 1956 and 2007 in Andalusia (Southern Spain) were selected for this pilot study, assessed by comparison of spatial data from 1956 and 2007 and were reclassified following land cover flows (LCFs) reported in major areas in Europe. Carbon vegetation densities were related to land cover, and C vegetation stocks for 1956 and 2007 were calculated by multiplying C density for each land cover class with land cover areas. The study area has supported important changes during the studied period with significant consequences for vegetation C stocks, mainly due to afforestation and intensification of agriculture, resulting in a total vegetation C stock of 156.08 Tg in 2007, with an increase of 17.24 Tg since 1956. This study demonstrates the importance of LCC for C sequestration in vegetation from Mediterranean areas, highlighting possible directions for management policies in order to mitigate climate change as well as promoting land conservation. The methodologies and information generated in this project will be a useful basis for designing land management strategies helpful for decision makers.
Abstract: Mediterranean soils under heathland are often shallow, with low capacity for water storage, and a high risk of erosion. In this context, recurrent wildfires can negatively affect their chemical and physical properties. Very little research has been carried out concerning the long-term variations on the ground surface after burning. The behaviour of plant communities and plant cover can regulate and control soil processes in the post-fire period, so that the evolution of vegetation communities must be taken into account when studying the evolution of soil processes after disturbance. In this study, the impact of fire on several physical and chemical soil properties have been investigated during 3 years after experimental burning in a Mediterranean heathland. On average, the soil organic matter content after the fire decreased strongly, and one year after the fire it did not vary substantially, although it increased slightly during the following two years until the end of experiments. Burning led to coarser texture immediately after fire, but clay content decreased strongly during the following 3 years due to post-fire erosion processes and selective detachment of fine particles. Soil pH and electrical conductivity increased ephemerally and returned to initial values just 1-year after the fire. Soil water repellency was partly destroyed by the scorching, but pre-fire proportion of water-repellent soil samples was observed just after 1-year. Water-repellent aggregates may have been removed by post-fire erosion, but water repellency also appears as a natural attribute of these soils. Reduction in organic matter content after the fire and changes in texture and water repellency contributed to a decreased stability of aggregates and an increased bulk density.
Abstract: Fire can affect soil properties depending on a number of factors including fire severity and soil type. Aggregate stability (AS) refers to soil structure resilience in response to external mechanical forces. Many authors consider soil aggregation to be a parameter reflecting soil health, as it depends on chemical, physical and biological factors. The response of AS to forest fires is complex, since it depends on how fire has affected other related properties such as organic matter content, soil microbiology, water repellency and soil mineralogy. Opinions differ concerning the effect of fire on AS. Some authors have observed a decrease in AS in soils affected by intense wildfire or severe laboratory heating. However, others have reported increases. We provide an up to date review of the research on this topic and an analysis of the causes for the different effects observed. The implications for soil system functioning and for the hydrology of the affected areas are also discussed. Generally, low severity fires do not produce notable changes in AS, although in some cases an increase has been observed and attributed to increased water repellency. In contrast, high severity fires can induce important changes in this property, but with different effects depending on the type of soil affected. The patterns observed can vary from a disaggregation as a consequence of the organic matter destruction, to a strong aggregation if a recrystallization of some minerals such as Fe and Al oxyhydroxides occurs when they are present in sufficient quantities in the soil, after exposure to high temperatures. Because of the complexity of the different possible effects and reasons for the potential changes in the fire-affected soil aggregates, the inclusion of other parameters in the studies is necessary to understand the results. The suggested parameters to include in the examination of AS are: soil organic matter, microbial biomass, water repellency, texture, aggregate size distribution, together with accurate ways of estimating fire severity. More research is needed on what implications have for soil system functioning the changes suffered by aggregates after fire. Studies including measurements at very different scales: from AS measurements in the laboratory to erosion rates measured at pedon, slope and catchment scales are also neccesary.
Abstract: Soil water repellency has been conventionally considered as a fire-induced effect, but an increasing number of works have suggested that natural background repellency occurs in many soil types, and many of them have suggested that water repellency can re-establish a time after being destroyed. An experimental fire was conducted to study changes of the soil surface during the first 18 months following intense burning. The main objectives of this paper are: [1] to investigate in situ water repellency changes at three soil depths (0, 2 and 4 cm) immediately after burning, [2] to evaluate the medium-term evolution of water repellency under field conditions, and [3] to outline the main hydrological consequences of these changes. Also, different water repellency tests (water drop penetration time, ethanol percentage test and contact angle between water drops and soil surface) were carried out with comparative purposes. Field experiments showed that soil water repellency soil water repellency was partly destroyed after intense burning. Changes were relatively strong at the soil surface, but diminished progressively with depth. Levels of water repellency were practically re-established 18 months after burning. This suggests that water repellency in the studied area is not necessarily a consequence of fire, but can instead be a natural attribute. Finally, although limited in time, destruction of soil water repellency has important consequences for runoff flow generation and soil loss rates, and, indirectly, for water quality.
Abstract: Rock fragments are a key factor for erosional rates especially in arid and semiarid environments, where vegetation cover is low. However, the effect of rock fragments in natural forest soils still is not well understood. Currently, there is a need for quantitative information on the effects of rock fragments on hydrological soil processes, in order to improve models aiming to predict soil erosion more accurately. Thus, the objective of this paper is to study the influence of rock fragment cover on runoff and interrill soil erosion under simulated rainfall in Mediterranean bare soils in Southwestern Spain has been studied in this work. Thirty six rainfall simulation experiments have been carried out at an intensity of 26.8 mm h-1 during 60 minutes and three different classes of rock fragment coverage ( 60;50 %, 50-60 % and 62;60 %). Ponding and runoff flow were delayed in soils with high rock fragment cover values. In addition, sediment yield and soil erosion were found to be higher in soils with a low rock fragment cover. The relationship between soil loss rate and rock fragment cover was approached by an exponential function. After this first set of experiments, rock fragments were removed at sites with the highest cover ( 62;60 %) and rainfall simulations were repeated. Steady-state runoff rate and soil loss increased significantly, showing that runoff and soil erosion were controlled by rock fragments on the soil surface. These results have implications for erosion modelling and soil conservation practices under the same climate and soil characteristics, but further research and standard soil loss estimations are still needed.
Abstract: Application of crop residues to soil and reduced or no tillage are current management practices in order to achieve better water management, increase soil fertility, crop production and soil erosion control. This study was carried out to quantify the effect of wheat straw mulching in a no tilled Fluvisol under semi-arid conditions in SW Spain and to determine the optimum rate in terms of cost and soil protection. After a 3-years experiment, mulching application significantly improved physical and chemical properties of the studied soil with respect to control, and the intensity of changes was related to mulching rate. The organic matter content was generally increased, although no benefit was found beyond 10 Mg ha-1 year-1. Bulk density, porosity and aggregate stability were also improved with increasing mulching rates, which confirmed the interactions of these properties. Low mulching rates did not have a significant effect on water properties with respect to control, although the available water capacity increased greatly under high mulching rates. After simulated rainfall experiments (65 mm h-1 intensity), it was found that the mulch layer contributed to increase the roughness and the interception of raindrops, delaying runoff generation and enhancing the infiltration of rain water during storms. Mulching contributed to a reduction in runoff generation and soil losses compared to bare soil, and negligible runoff flow or sediment yield were determined under just 5 Mg ha-1 year-1 mulching rate. It was observed that during simulations, the erosive response quickly decreases with time after prolonged storms (30 minutes) due to the exhaustion of available erodible particles. These results suggest that the erosive consequences of intermediate intensity 5-years-recurrent storms in the studied area could be strongly diminished by using just 5 Mg ha-1 year-1 mulching rates.
Abstract: Soil water repellency is usually modified after wildfires by combustion of soil organic matter and plant residues, and has is considered as the cause of important changes in the hydrological response of burned soils. The influence of burning on water repellency depends on many factors, resulting on different patterns depending, among other factors, on the soil type and pre-existing degree of water repellency. Wildfires also affect aggregate stability because of combustion of soil organic matter, although contradictory results have been reported. Also, soil water repellency is known to affect soil aggregate stability by retarding the wetting process. In this research, the interactions between burning temperature, soil water content, water repellency and stability of aggregates has been studied. Samples collected from soils under eucalyptus forest in Spain, Mexico, and Australia were treated at 100-150, 200-250, and 400-450 oC under dry and moist conditions in the laboratory, and temperature profiles and changes in water repellency were analyzed. In order to study the effects of burning temperature on aggregate stability, homogeneous top soil samples (0-5 cm depth) were collected at five soil plots at Sierra de Aracena Natural Park (SW Spain) and treated at different temperatures (ranging between 50 and 400 oC). Results showed that soil water repellency did not change significantly respect to unheated control samples after temperatures between 100-150 oC, but it decreased considerably at 250-300 oC and practically disappeared after heating at 400-450 oC. Soil moist induced a decrease of water repellency in samples treated at 100-150 oC and 250-300 oC, but its effect was negligible at higher temperatures. Laboratory heat treatments reduced soil aggregate stability, especially after exposure to temperatures above 200 oC. Different approaches to water repellency were used for comparative purposes.
Abstract: The objectives of this research are the following: [1] to study the persistence and intensity of water repellency in soil samples (0-5 cm deep) collected under different plant species, [2] to analyze the relationships between soil water repellency and environmental factors including soil organic matter content, soil acidity, and texture, and [3] to study the variations of soil water repellency measured on soil samples collected in winter (2007) and summer (2008) in the studied area. Soil water repellency has been studied in Mediterranean coniferous and eucalyptus forests, particularly after burning, but the number of studies concerning other Mediterranean forest systems is still very low. In this paper, soil water repellency was measured by using the water drop penetration time test and the ethanol percentage test on samples collected during the winter of 2007 and the summer of 2008 under different land uses (pines, cork oaks, eucalyptus, heathland and olive trees) in a Mediterranean subhumid forested area (Los Alcornocales Natural Park, Cádiz and Málaga, Spain). Most of soil samples collected under heathland showed extreme water repellency, whereas soils under olive trees showed low or inexistent water repellency. The organic matter content and acidity were highly correlated with water repellency in soils under pines, cork oaks and eucalyptus, while soils under heathland or olive trees showed poorer correlations. The average soil moisture content of samples collected during winter (2007) was 20.7 177;7.9 %, and it decreased in samples collected during summer (2008) to 1.1 177;0.6 %. The persistence and intensity of water repellency varied slightly between samples collected in winter and summer in soils under all species except under heathland. Water repellency persisted in most cases during the wet and dry season, and many soils showed strong water repellency even during winter. The patchy patterns of persistence and intensity of soil water repellency is conditioned by the spatial distribution of the studied land uses, which dictate the intensity and persistence of soil water repellency, and modulated by other environmental factors. The vegetation effects on soil hydrology should be considered for afforestation work and flooding control.
Abstract: This paper describes the changes in soil water repellency and soil hydrological and erosional responses to rainfall at small-plot scale, arising from a prescribed fire immediately following burning and one year later in a Mediterranean heathland in the area of the Strait of Gibraltar (southern Spain). Very little research has been carried out about the modifications on the ground surface after fire immediately after burning. A prescribed fire was conducted to study short-term changes of the ground surface immediately and one year following burning. After a prescribed fire, a homogeneous charred litter layer and ash-bed covered the mineral soil surface. This cover stayed stable on the soil surface during a period of seven days, until strong winds redistributed litter and ashes. The hydrophobicity of the exposed surface (litter and ashes) decreased considerably in relation with the litter layer properties before the fire. Ponding, runoff coefficients and soil loss were determined using simulated rainfall over the litter layer, the ash-bed and the bare soil. Significant differences were not detected between pre- and post-fire soil loss rates while a charred litter and thick ash layer were present on the ground surface. Runoff and erosion rates increased and time to ponding and runoff decreased when the charred litter and ash layers were artificially removed and the bare soil was exposed. Although wildfires will increase soil erodibility, the trends observed in this study suggest that this increased susceptibility to erosion from rainsplash processes may be limited to some degree while an intact ash and charred litter layer is still present.
Abstract: The distribution and variation with soil depth of water repellency has been studied in fire-affected sand dunes under three different vegetation types (pine forest, shrubland and sparse herbaceous vegetation) in SW Spain. The persistence and intensity of water repellency at the exposed surface of soil was measured using the water drop penetration time test and the contact angle method, respectively, in surface samples (0- 3 cm) collected at burned and unburned areas. The variation of water repellency with depth in burned areas was studied in soil profiles every 5 cm between 0 and 40 cm depth. None or slight soil water repellency was observed at unburned soil sites, whereas burned soil sites showed a high degree of repellency, especially under pines and shrubland. The spatial pattern of fire-induced soil water repellency was found to be associated to vegetation types, although it was modulated by soil acidity and the soil organic carbon content. Soil water repellency was generally higher at the soil surface, and decreased with depth. Dense pine forests and shrublands showed strong and/or severe water repellency in depth, but it was rare and limited to the first five centimeters under sparse herbaceous vegetation. The heterogeneity of moisture patterns under dense pine forests or shrublands showed the existence of wetting and water repellent three-dimensional soil patches.
Abstract: Little is known on the hydrological behavior of the volcanic ash soils, which are characterized by extremely high porosities and hydraulic conductivities. In this study the occurrence and hydrological effects of water repellency were investigated at a plot scale for different types of land use and volcanic soils in Mexican volcanic highlands from Michoacan, Mexico: [1] fir, pine and oak mixed forest soils developed from lavas, [2] soils developed from volcanic ashes and pyroclastic sediments under sparse fir, pine and oak forest and shrubland, [3] pine and oak forested soils developed from lavas and pyroclastic sediments, and [4] bare soils on recent ash sediments in plain surfaces. Soil water repellency was assessed using the water drop penetration time test and rainfall simulations were performed on circular plots (50 cm in diameter) during 30 min and at an intensity of 90 mm h-1 in order to study the hydrological response of each area. The return period for storms with a similar intensity in the area is 10 years. The shape and depth of the wetting front after simulated rainfall was also analyzed. Soil water repellency showed a high variability among the different studied zones. Organic matter content, soil texture and acidity were the most important factors for developing hydrophobicity. A wide range of soil water repellency classes (hydrophilic to severely water-repellent soils) has been found in soils under dense fir, pine and oak mixed forests or shrubland, while inexistent or slight water repellency has been observed in soils under sparse forest or at bare ash-covered areas. At a plot scale, marked differences in the hydrological behavior of the studied land use and soil zones were observed after the rainfall simulations. Soil water repellency contributes to fast ponding and runoff generation during the first stages of rainstorms. Runoff was enhanced in water-repellent forested soils (average runoff coefficients between 15.7 and 19.9 %), in contrast to hydrophilic or slightly water-repellent soils, where runoff rates were lower (between 1.0 and 11.7 %). Shallow and irregular wetting fronts were observed at water-repellent zones, reducing the soil water storage capacity. The implications of soil water repellency in soil hydrology and erosion risk in the area shed light on the soil hydrology of the studied ecosystems, and can contribute to develop better management policies.
Abstract: It is established that soil hydrophobicity reduces soil infiltration rates, and enhances runoff flow and soil erosion. Water repellency has been studied with special interest in coniferous and eucalyptus forests, particularly after burning, but the number of studies concerning Mediterranean heathlands is still very low. In this paper, we study the occurrence and persistence of water repellency in soil samples collected under different plant species susceptible to induce soil hydrophobicity (Erica arborea, Erica australis, Calluna vulgaris, Quercus lusitanica and Rhododendron ponticum) in a natural protected area in southern Spain. Great attention has been paid to the relationships between soil water repellency and environmental factors as organic matter content and soil acidity. The largest hydrophobicity was measured in soil samples collected under E. australis, E. arborea and C. vulgaris. For these species, the organic matter content and pH showed positive and negative correlations with the persistence of water repellency, respectively. The hydrophobicity originated by humic substances in the soil seems to be the only explanation for slight soil water repellency under Q. lusitanica or R. ponticum. The patchy patterns of occurrence and persistence of soil water repellency is governed by the spatial distribution of the studied species and modulated by other factors. Soil surface water repellent layers reduce the infiltration rates and limit the water storage capacity. However, the macropore flow can be enhanced on non-repellent layers, cracks or roots such us the wetting front showed. The vegetation effects on soil hydrology should be considered for afforestation works and flooding control.
Abstract: Surface runoff and sediment production on unpaved forest roads in a humid Mediterranean mountainous area has been studied using a simple portable rainfall simulator at an intensity of 90 mm h-1. Thirty six rainfall simulations were carried out on road plots: on the roadbank (12), on the sidecast fill (12), and on the roadbed (12). On the roadbanks, the steady-state runoff coefficient was 85.9% and runoff flow appeared after 63 s on average. On the sidecast fills, the steady-state runoff coefficient was 58.6% and mean time to runoff was 48 s. Finally, on the roadbeds, the steady-state runoff coefficient was 21.5% and mean time to runoff was 41 s. The highest soil loss rate was found on the roadbanks (486.7 g m-2), mainly due to low plant cover, soil texture and rock fragments. The total soil erosion on the roadbanks was 3 and 18 times higher than those from the roadbeds and the sidecast fills, respectively. As a consequence, roadbanks can be considered the main source of sediments on the studied sites, but the function of unpaved forest roads as source points for runoff generation is more important.
Abstract: Runoff and soil loss from forest road backslopes is a serious problem in Mediterranean areas. Surface runoff and sediment production on backslopes of forest roads in Los Alcornocales Natural Park (southern Spain) has been studied in this paper using a simple portable rainfall simulator at an intensity of 90 mm h-1. One hundred rainfall simulations were performed on bare and vegetated road backslopes during summer and winter in order to study seasonal differences. Runoff coefficients and soil loss rates were lower on the vegetated plots than on the bare ones. Runoff coefficients increased 1.7 (bare backslopes) and 3.1 times (vegetated backslopes) from summer to winter. Preserving the vegetation cover over 20% is recommended for keeping soil loss rates under low levels, especially during winter.
Abstract: It is known that rock fragments on the surface of soils can enhance infiltration and protect the soil against rainfall erosion. However, the effect of rock fragments in natural forest soils is less well understood. In this article, we studied the influence of rock fragment cover on run-off, infiltration and interrill soil erosion under simulated rainfall on natural bare soils in a Spanish dehesa (managed holm oak woodland). We studied 60 plots with different rock fragment cover ranging from 3% to 85% under three simulated rainfall intensities (50, 100 and 150 mm/h). Surface run-off appeared later and sediment yield values were smaller in soils with greater rock fragment cover. Rock fragment cover also increased infiltration rates. The final infiltration rates were 54–98% at a rainfall intensity of 50 mm/h, 31–88% at 100 mm/h and 20–80% at 150 mm/h. The interrill soil loss rates were decreased by rock fragment cover and increased with rainfall intensity. The soil loss rate was always small (0.02–1 Mg ha/h) when rock fragment cover was 75% or more. Rock fragment cover was related to soil loss rate by an exponential function.
Abstract: We have studied the surface runoff and sediment production on unpaved forest roads in Los Alcornocales Natural Park (southern Spain) using a simple portable rainfall simulator at an intensity of 72 mm h−1. Thirty rainfall simulations were carried out on 10 road plots: on the roadbank (10), on the sidecast fill (10), and on the roadbed (10). On the roadbanks, the runoff coefficient was 58% and runoff flow appeared after 60–90 s. On the sidecast fills, the runoff coefficient was 27% and time to runoff was 5–108 s. Finally, on the roadbeds, the runoff coefficient was 51% and time to runoff was 25–89 s. The highest soil loss rate was found on the roadbanks (106 g m−2), due to slopes, the existence of loose colluviums, and a low plant cover. The total soil loss from the roadbank was 5 and 6 times higher than those from the roadbed and the sidecast fill, respectively. The sediment concentration increased during the first 6–8 min from the beginning of the simulations and then decreased steadily due to the loss of fine soil surface particles and porosity changes. Statistical analysis shows that plant cover on roadbanks, sidecast fills, and roadbeds has a significant effect on runoff. Rock fragment cover and slopes on the roadbank and the sidecast also influence runoff significantly. The behavior of roadbanks was similar to that of other cultivated soils and abandoned sloping fields. Sidecast fills had the same response as abandoned terraces or non-vegetated road embankments. Reducing the roadbank angle by approximately 40% and increasing the plant cover to 35–40% are necessary for keeping erosion below 18 g m−2, as it was on the sidecast fills.
Abstract: his paper reports results from the analysis of the soil hydrological response to simulated rainfall in a cork oak forest in Los Alcornocales Natural Park (SW Spain). Four different soil/vegetation units were selected for the field experiments: [1] cork oak woodland, [2] heathland, [3] grassland, and [4] cork oak/olive tree mixed forest. Rainfall simulations tests were performed on circular plots of 1256.6 cm2 at an intensity of 56.5 mm h−1 for 30 min. Marked differences in the hydrological behavior of the studied vegetation types were observed after the rainfall simulations. The soils under woodland showed low runoff rates and coefficients. The highest runoff rates were measured on the heath and grass-covered parts of the hillslope. Water repellency of the soil, measured from water drop penetration tests, reduced infiltration (especially under the heathland), and seems to be the cause of fast ponding and runoff generation during the first stages of rainstorms. The mosaic of different patterns of hydrological response to rainfall, such as runoff generation or infiltration, is governed by the spatial distribution of vegetation and its influence on the soil surface.
Abstract: Land evaluation parametric models are quantitative, specific and easy methods based on soilproperties. Generally they have reduced subjective aspects, to consider interactions among factors, and use field data instead of use limitations (Aguialr, 1992). Software Evaluator (Del Toro, 1996) makes land evaluation based on selected chemical properties of soils and generate an evaluation index according to additive parametric model which stablish the relationships between five Mediterranean vegetation types (holm-oak wood, cor-oak wood, pinewood, gall-oak wood, and pasture). This system has been tested in other natural areas in Andalusia (Spain).
Abstract: A morphological analysis of the physical way of the Natural Park Los Alcornocales has been carried out in this paper. With this goal, a digital elevation model has been used as the main source of basic information, so that different topographic characteristics have been studied, as the slope, the local relief and the curvature of the surface. The integrated analysis of these parameters by GIS has allowed the morphologic automatic classification of the area.
Abstract: Potential soil erosion risk in the high basin of Hozgarganta River is analyzed in this paper. We have used the methodology proposed by PAP/RAC (1997), as modified Jordán and MartÃnez-Zavala (Jordán, 2000; MartÃnez-Zavala, 2001; MartÃnez-Zavala et al., 2002). Using this method, the study area has been divided in terrain units with different level of susceptibility to rainfall-induced erosion risk (erosive status). An assesment of actual and potential erosion risk is carried out, suposing three posible situations, acording to different percentages of canopy. As a conclusion, the actual soil erosion risk is low for the Hozgarganta Basin. However, the equilibrium of the system is unstable, so that little changes in the vegetation cover may originate great changes in the intensity of the erosive processes
Abstract: The evolution of a system of gullies located near Tarifa, in the southern limit of Los Alcornocales Natural Park, has been studied in this work for the period 1956-1995. The morphology and growing rate of each gully were analyzed, and the relationships beetwen them and the climatic and physical environment were studied. The gullies were identified using teledetection techniques, by interpretation of georreferenced aerial photographs, processed using the software ARC/INFO. Erosion by gullies in the studied area looks relatively stabilized, although stable and active phases have been observed in different times of the studied period. A critical point in the growth of the studied gullies has been detected, related to the watershed area for the headcut.
Abstract: Agricultural soil suitability and forestry suitability of Campo de Gibraltar are studied in this paper. Two models included in the MicroLEIS system for agro-ecological land evaluation (De la Rosa et al., 1996). The ALMAGRA model has been used for farmlands, while SIERRA model has been applied to protected areas of Los Alcornocales Natural Park, included in the Campo de Gibraltar area. The geomorphoedaphic units database by Paneque et al. (1998) has been used as input data. The results were integrated in a geographical information system, using the software ARC VIEW GIS (ESRI, 1992-1996).
Abstract: In this paper we explain the methodology followed for Mapping GeoMorphoPedologic Units in Los Alcornocales Natural Park and its environment (9 maps, S 1:50.000; Paneque et al., 1998), carried out by an agreement of collaboration signed between the Regional Ministry for the Environment of Andalusia and the Department of Agricultural Chemistry of the University of Seville. By photointerpretation of aerial photographs and satellite images, we defined map units, which were described geomorphologically and pedologically. Finally, we obtained 521 different geomorphopedological units (GMPU) and 61 types of soil-associations. A computer database was made, where each GMPU is characterized by 10 different variables, including lithology, slope, soil, active geomorphic processes and others.
Abstract: Mulching is a form of conservation tillage consisting of leaving a layer of crop residues (CR) or other materials on the soil surface. Mulch helps to preserve high and sustainable yields by increasing the soil organic matter (SOM) content and therefore improving soil physical quality. Mulch tilling is also a form of minimum tillage and a cost-efficient alternative for high-yield conservation agricultural practice. Leaving CR or other substances on the soil surface is a traditional practice for protecting soil from erosion and enhancing fertility (Lal and Stewart, 1995). It has been reported that conventional agricultural practices, based on intensive fertilization and chemical amendments, often lead to degradation processes, such as erosion (see "Tillage erosion"), acidification, and the emission of greenhouse gases (see "Greenhouse gases sink in soil"). Current global problems such as population growth, greenhouse effect, malnutrition, water quality, reduction of agricultural land and soil degradation (see "Desertification, indicators and thresholds") require the implementation of conservation tillage practices to address the problem of sustainability, food security and environmental quality.
Abstract: The main objective of this paper is a detailed analysis of the physical environment of the Tepalcatepec River basin (through the states of Jalisco and Michoacan, Mexico) as a previous stage to an erosion risk map. We have used an classification system modified from Dikau et al. (1991). The results obtained let us to divide the basin of the Tepalcatepec River in five classes of main geoforms. Each class has been divided in several subclasses, so that 17 land units have been distinguished. The results show that the used method allows to identify accurately the existing land forms, and with much greater detail, an elevated number of subclasses.
Abstract: We studied the relationships between different estimates of the woody canopy density; different estimates of litter release and accumulation, and different soil properties (mainly soil reaction and macronutrient level) which have been recognised as potentially relevant for plant establishment and development in mixed Quercus forest from Natural Park “do Sudoeste Alentejano e Costa Vicentina”, Portugal (with Q. suber, Q. faginea as dominant tree species) and Natural Park “Los Alcornocales”, Spain (with Q. suber and Q. canariensis). We have found 1) A highly significant, quantitative, relationship between litter accumulation and overall canopy density. These relationships can be established either by using objective (but time-consuming) measures (by sampling or using ad hoc measuring devices) or by calibrated by-eye estimates of three simultaneous observers; 2) A significant relationship between some soil properties (N, P, ammonium) and both canopy density and litter accumulation. We conclude that these relationships are interesting in two ways: 1) They may allow to establish ‘ecotransfer functions’ for these forests (i.e. estimates o predictions about surface litter accumulation or surface values for soil properties, as organic carbon, N or P contents, by using quick field estimates of canopy density or even remote sensing estimates of canopy density), after suitable calibrations. 2) Since some soil chemical properties with known ecological relevance (e.g. C, N, P contents, soil reaction) in forest regeneration may change in a close relationship with other more studied, better known, ecological factors (light, moisture, temperature), attention should be paid to separate direct (e.g. light limitation) versus indirect (soil or litter mediated) effects of woody canopy when evaluating ecological responses at the understorey, while studying forest regeneration processes.
Abstract: A classification of antropized soils in Southern Spain is proposed in this paper. Some of these soils show antropic characteristics in their genesis. The surface layer has been removed down to horizons C or R and the surface has been leveled. Different lithological materials have been added. The remotion of the original surface layer and the addition of aric materials constitutes an anthropic process deep enough to include the studied soils in the group of Anthrosols. Nevertheless, in this case the rised surface is not the result of the continued culturing, but of the recently added material. In spite of everything, the diversity of the anthropic soils makes its definition difficult, except in the general terms used by the WRB. It defines the Anthrosols as soils that have been so transformed by anthropedogenic processes that the original soil is not already recognizable or survives only as a buried soil. The principal characteristic of the studied soils is the presence of a common anthropic horizon, whose description is not given clearly by the WRB. This horizon is constituted by materials transported and arranged in ridges on the former substrate, without showing in situ alteration. These circumstances might be described by a common adjective regarding the principal use of these soils in the province of Huelva that we propose like “citricola”.
Abstract: Soil organic carbon stock in Los Alcornocales Natural Park (Spain) has been studied to a depth of 200 cm, using data from 83 soil profiles. The average soil organic carbon pool in the studied area is 67 t ha-1 for the first 30 cm de suelo, 124 t ha-1 for 100 cm and 156 t ha-1 for 0-200 cm. The total stock of organic carbon in the park is 16 Mt, 29 Mt and 37 Mt for 0-30, 0-100 and 0-200 cm deep. More than 7 Mt of organic carbon are confined between 1 and 2 m deep, and could be a sink for atmospheric CO2. Soil use, microclimatic variations, relief and physic-chemical characteristics of the soil (as clay content or acidity) might be factors influencing the ability of soil as a carbon storage.
Abstract: Geographical information system (GIS) technologies allows researchers to easily study biotic and abiotic elements of the landscape, in order to build and try models. Landscape classification and assessment of natural resources are useful tools for land use planning. Many methods have been developed to evaluate natural resources. In this work, we use a method for mapping homogeneous land units at a reconnaisance scale in a large territory, as a previous step for more detailed studies. The main goal was to describe the physical environment of the W portion of the county of Huelva (SW Spain). The interpretation of satellite images and the use of digital terrain models, integrated in a GIS, makes possible the study of soil-landscape relationships in order to evaluate, map and build models of environmental factors. Land units have been defined from a series of significant and strongly interrelated environmental variables, as lithology, geomophology, land use and soil. These factors were evaluated using high resolution remote sensing data and field work. So, the studied territory has been divided in 17 macro-units or natural land systems, valid at a broad scale.
Abstract: Mapping of rainfall-induced erosion risks of the area included in the sheet n 186; 937 of the Topographical Map of Andalusia (1:50.000) is carried out in this work. The methodology is based on the guidelines proposed by PAP/RAC (1997) for the mapping of the erosion risks, using a Geographical Information System (GIS). Some new considerations were included in order to collect the local variability and regional land uses not considered in the guidelines by PAP/RAC. Also, a study of soils was carried out, so that erodibility classes were defined more exactly. This, can allow us to apply predictive mapping at a semi-detailed scale. Different sources of information were used, aerial photographs, false color satellite images (Landsat-TM), and a Digital Terrain Model (DTM). We also used field and analytic data about soils, topography, lithology, physiography, land use and canopy of the diferent vegetation strata. Most of the area studied comprises very eroded metamorphic Paleozoic materials (slates and phyllites). Soils are shallow, limited by hard rock nearby the surface. Although 70% of the surface of the area shows a low erosion risk, because of its resistance to the mechanical action of the rain and the smooth slopes of the terrain, there are apparent signs of generalized soil loss. This is probably due to other factors not taken into account by the model, such as grazing animals, frequency of fires, and/or precipitation intensity.
Abstract: Forest fires are recurrent phenomena in the Mediterranean area and = are one of the main causes of changes in Mediterranean ecosystems, = increasing the risk of soil erosion and desertification. Fire is an = important agent which can induce important changes in the chemical and = physical characteristics of soils. Burning severity can modulate the = recovery of plant communities and the quantity and intensity of changes = in fire-affected soil system. Mediterranean soils under heathland often = shallow with low capacity for water storage, and high erosion risks. In = this context, recurrent wildfires can negatively affect their chemical = and physical properties. Very little research has been carried out = concerning the long-term variations on the ground surface after burning. = In this study, the impact of burning on several physical and chemical = soil properties have been investigated during 3 years after experimental = burning in a Mediterranean heathland. On average, the soil organic = matter content after fire decreased strongly, and one year after fire it = did not vary substantially, although it increased slightly during the = following two years until the end of experiments. Burning led to coarser = texture immediately after fire, but clay content decreased strongly = during the following 3 years due to post-fire erosion processes and = selective detachment of fine particles. Therefore, textural changes = cannot be totally attributed to burning. Most likely post-fire soil = erosion processes contributed to selective removal of clay, leading to = exhaustion of fine detachable mineral particles. Combustion of soil = organic matter strongly affected chemical properties of soil, increasing = pH and electrical conductivity by release of cations. These early = changes were ephemeral and pre-fire values were re-established after = just 1-year period. Soil water repellency was partly destroyed = immediately after intense burning, but pre-fire proportion of = waterrepellent soil samples was observed just 1-year after. = Water-repellent aggregates may have been removed by postfire erosion, = but this result is in agreement with previous research by the authors = and confirms that water repellency is a natural attribute of these = soils. In addition, after removal of vegetation, post-fire soil erosion = processes led to exposition of subsurface hydrophobic soil material not = affected by burning temperatures. High fire severity led to a reduction = in organic matter content and, subsequently, to decreased stability of = aggregates and increased bulk density. These findings are in agreement = with results from other authors, who have related high organic matter = contents in Mediterranean soils with high aggregate stability. Probably = a lower aggregate stability, immediately after experimental burning = could be explained in part as a result of partly destroyed water = repellency.
Abstract: Soils are the most substantial reservoirs of terrestrial carbon. = Land use and land use change affects soil carbon pools and play an = important role in determining whether soil is acting as a source or sink = of atmospheric carbon depending on its management. The objective of this = research is to assess the effects of land use changes between 1956 and = 2007 on soil carbon stocks in southern Spain and quantify soil carbon = stocks for each land use type. Land use changes between 1956 and 2007 = were detected by comparison of data layers and soil information was = gathered from available databases from previous works. Land cover = classes in 1956 and 2007 and land cover flows were assigned to soil = profiles using spatial analysis techniques. The results show that = intense land use/cover changes in southern Spain are a new source of = carbon to the atmosphere.
Abstract: Land use has significantly changed during the recent decades at = global and local scale, while the importance of ecosystems as = sources/sinks of C has been highlighted, emphasizing the global impact = of land use changes. Organic C accumulates in soil in the long-term, but = land use changes can increase C loss rates which are extremely difficult = to reverse in the short term. The aim of this research is to improve and = test methodologies to assess land cover change (LCC) dynamics and = temporal and spatial variability in C stored in vegetation at a wide = scale. LCC between 1956 and 2007 in Andalusia (southern Spain) were = selected for this pilot study, assessed by comparison of data layers and = reclassified following land cover flows (LCFs) reported in Europe. = Carbon vegetation densities were related to land cover, and C vegetation = stocks for 1956 and 2007 were calculated by multiplying C density for = each land cover class with land cover areas. The study area has = supported important changes during the studied period with significant = consequences for vegetation C stocks, mainly due to afforestation and = intensification of agriculture, resulting in a total vegetation C stock = of 156.08+-106 Mg in 2007, with an increase of 17.24+-106 Mg since 1956. = This study demonstrates the importance of LCC for C sequestration in = vegetation from Mediterranean areas, highlighting possible directions = for management policies in order to mitigate climate change as well as = promoting land conservation. The methodologies and information generated = in this project will be a useful basis for designing land management = strategies helpful for decision makers.
Abstract: This research focuses on the efficiency of N forms, one of the = most limiting factors in agriculture. Two organic N-fertilizers = (Agrimartin and Abonatur) and four different doses were applied (0, 50, = 100, and 150 kg ha-1) during a 5 month-period (June-October) in an = experimental farm in SW Spain, and total nitrogen, ammonium and nitrate = soil contents were monthly determined. Small differences were observed = between treatments, probably due to high previous contents in soils, but = dynamics demonstrated that Abonatur showed a more efficient = mineralization rate, and optimal doses were established (50 kg ha-1 N).
Abstract: The effects of fire on the soils depend on the temperature = reached, duration of burning and post-fire rainfall. The combustion of = organic matter, deposition of ashes and alterations in nutrient = availability are the main processes of chemical change associated with = fire. High intensity and fast moving crown fires can consume a part of = litter during the process of combustion because only a small amount of = the energy released is transferred to the litter surface. In such cases, = litter is charred but not consumed, and a thick ash-bed can be set down = on the soil. The effect of charred litter and ashes on the mineral soil = surface will persist until external agents (strong rainfall, wind, = vehicles or animals) remove or redistribute them. Its presence on the = soil surface can be critical during the immediate post-fire period in = Mediterranean areas and specifically in the area of the Strait of = Gibraltar, where intense rainfall events are not unusual during summer. = The changes induced by charred litter and ashes on the soil hydrological = and erosional response after a prescribed fire in a Mediterranean = heathland in the area of the Strait of Gibraltar (southern Spain)have = been studied in this research. Very little research has been carried out = about the modifications on the ground surface after fire immediately = after burning. A prescribed fire was conducted to study short-term = changes of the ground surface immediately and 1 year following burning. = After burning, the soil surface was covered by charred plant skeletons, = charred litter, and a thick ash-bed. After burning, water repellency was = significantly reduced at the exposed surface of ash-covered soil plots; = in addition, the bare soil plots generated significantly more erosion = than did ash and/or chatter litter covered surfaces. Consequently, = post-fire changes may decrease the hydrological response while charred = organic residues and ashes stay on the soil surface. When this = protective cover is removed, the mineral soil surface is exposed; in = this case, the water repellency of the mineral soil can accelerate the = erosive response. Therefore, the ash and charred litter layers offered = some protection against soil loss that would have occurred in their = absence even with significant reductions in water repellency. Results = from rainfall simulations at the small scale in this study suggest that = interrill soil erosion risk by rainfall in dense heathland can remain = stable during the immediate post-fire period when a fire results in a = thick deposition of ashes. In contrast, when the bare soil surface is = exposed, the erodibility may increase. Although wildfires use to = increase soil erodibility, the trends observed in this study suggest = that, at the scale of work this increased susceptibility to erosion is = limited to some degree while an intact ash and charred litter layer is = still present. When burning results in a substantial deposition of = ashes, the ash-bed can prevent soil from fast runoff generation and = reduce the erosion risk while it is present. After the ash-bed is = removed by natural agents (as strong rainfall or wind), runoff = coefficients and soil loss can increase considerably at plot scale. The = recovery of natural vegetation one year after the prescribed fire = practically re-established the initial conditions before fire. Water = repellency, hydrological response and erosional response after 1-year = period were comparable to pre-fire conditions at a plot scale.
Abstract: Increased water repellency (WR) in fire-affected areas has been reported by many authors. The degree of fire-induced WR depends for the most part on temperatures reached during burning. WR changes little at soil temperatures below 175 ºC, increases considerably between 175 and 200 ºC, and is destroyed when temperatures above 280 ºC are reached. These thresholds can vary depending on time of residence of temperatures and soil properties. Soil WR has been traditionally associated to coarsely textured soils. However, some authors have found a certain contribution of finer fractions to soil WR, similar or more intense than coarser fractions. As the entrance of water in aggregates is retarded by repellency, and hydrophobic coatings act as cementing agents, aggregate stability is generally enhanced. It is known that soil WR plays a key role in the hydrology and the re-establishment of vegetation in fire-affected areas, and in consequence it is important to study in different soil types and environments. The objectives of this research are to study the effects of burning severity on the occurrence and degree of WR and aggregate stability in burned volcanic soils under pine and fir forests in central Mexico. The effects of different intensity burning on soil WR, aggregate stability, and the distribution of soil WR in aggregate sieve fractions were studied.
Abstract: Many authors have reported increased water repellency in fire-affected areas. Research on post-fire soil erosion show a range of results. Many authors have found increased soil erosion and runoff rates after fire, due to factors as loss of vegetation canopy, low structural stability of soils and enhanced runoff flow on soil surfaces affected by fire-induced hydrophobicity. Fingered wetting fronts in water repellent soils have been reported by different authors while a uniform and broadly horizontal wetting front developed in wettable soils. However, the heterogeneity of results, the influence of vegetation, and the diversity of responses after burning makes necessary the study and characterization of these processes with special interest in recurrently burned Mediterranean areas. The objectives of this research are to study the effect of burning in WR in Mediterranean soils under oaks and pines, to study the relationship of fire-induced WR and other soil parameters, and to study the effect of fire-induced WR in hydrological and erosional responses of soils under oaks and pines in the study area.
Abstract: This contribution summarizes the more significant results achieved during recent years by Med_Soil Research Group dealing with fire-induced soil water repellency (SWR) and its effects on soil hydrological and erosive processes. It is accepted that SWR reduces soil infiltration rates, and enhances runoff and soil erosion rates. Water repellency has been studied with special interest in relationship with Mediterranean soils under vegetation types as coniferous and oak forests, heathlands and grassland. The persistence and intensity of water repellency, its relationships with environmental factors including (soil organic matter content, soil acidity, and texture) and seasonal variability has been approached in soils under different plant species in Mediterranean subhumid forested areas. In this case, most of soil samples collected under heathland showed extreme SWR, whereas soils under olive trees showed low or inexistent SWR. The organic matter content and acidity were highly correlated with water repellency in soils under pines, cork oaks and eucalyptus, while soils under heathland or olive trees showed poorer correlations. Persistence and intensity of SWR varied slightly between samples collected in winter and summer in soils under all species except under heathland. Water repellency persisted in most cases during the wet and dry season, and many soils showed strong water repellency even during winter. The hydrological response and erosional response of soils has been achieved by rainfall simulation studies under cork oak woodland, heathland, grassland, and cork oak/olive tree mixed forests in Southern Andalusia. Significant differences in the hydrological behavior of the studied vegetation types were observed after the rainfall simulations. Soils under woodland showed low runoff rates and coefficients, whereas the highest runoff rates were measured on the heathland and grass-covered parts of the hillslope. SWR clearly contributed to reduce infiltration rates (especially under the heathland), and seems to be the cause of fast ponding and runoff generation during the first stages of rainstorms. The patchy patterns of persistence and intensity of soil water repellency is conditioned by the spatial distribution of the studied land uses, which dictate the intensity and persistence of soil water repellency, and modulated by other environmental factors. The vegetation effects on soil hydrology should be considered for afforestation work and flooding control. Changes in SWR and soil hydrological and erosional responses to rainfall at small-plot scale immediately following burning and one year later in a Mediterranean heathland in the area of the Strait of Gibraltar (southern Spain) have been studied. After an intense experimental fire, a homogeneous charred litter layer and ash-bed usually covers the mineral soil surface. This cover can stay stable on the soil surface during a short period until redistribution of charred litter and ashes by environmental agents. Water repellency at the exposed surface (litter and ashes) decreased considerably in relation with the litter layer properties before the fire. Significant differences were not detected between pre- and post-fire soil loss rates while a charred litter and thick ash layer were present on the ground surface. Runoff and erosion rates increase and time to ponding and runoff decrease when the charred litter and ash layers were artificially removed and the bare soil was exposed. Although wildfires increase soil erodibility, the trends observed in our studies suggest that this increased susceptibility to erosion from rainsplash processes may be limited to some degree while an intact ash and charred litter layer is still present.
Abstract: It is established that soil hydrophobicity reduces soil infiltration rates, and enhances runoff flow and soil erosion. Water repellency has been studied with special interest in coniferous and eucalyptus forests, particularly after burning, but the number of studies concerning other Mediterranean land uses is still very low. In this work, we study the effects of fire-induced water repellency in four different soil/vegetation units: cork oak forest, heathland, grassland, and cork oak / olive tree mixed forest. Runoff generation, infiltration rates and soil loss have been studied using simulated rainfall. Marked differences in the hydrological behavior of the studied soil/vegetation units were observed after the rainfall simulations. The soils under woodland showed low runoff rates and coefficients. The highest runoff rates were measured on the heath and grass-covered parts of the hillslopes. Soil water repellency, measured from water drop penetration tests, reduced infiltration (especially under the heathland), and seems to be the cause of fast ponding and runoff generation during the first stages of rainstorms, reducing the infiltration rates and limiting the water storage capacity. However, the macropore flow can be enhanced on non-repellent layers, cracks or roots as it is shown by de shape and depth of the wetting fronts. The mosaic of different patterns of hydrological response to rainfall, such as runoff generation or infiltration, is governed by the spatial distribution of vegetation and its influence on the soil surface. The effects of vegetation on soil hydrology should be considered for afforestation works and flooding control.
Abstract: The occurrence of water repellency is common in surface horizons from Mediterranean soils during and immediately after the dry season. Several researchers have highlighted the important role played by certain plant species in developing soil water repellency, although it cannot be assumed that these species always induce water repellency under natural conditions. Water repellency has been often described in the surface of dune sands. Water repellency in sandy soils develops as a consequence of sand particles coated with organic substances produced by fungal activity. Partially decomposed plant parts directly contribute to the development of water repellency in soils. Although the organic matter content of water repellent soils can be very low, the presence of organic substances as humic acids can induce soil hydrophobicity. Some of the consequences of soil water repellency are reduced soil infiltration rates, enhanced runoff flow and soil erosion. The importance of these effects depends upon the severity and spatial variability of hydrophobicity. Some authors have reported unstable wetting fronts in water repellent soils, in contrast with wettable soils, where water can infiltrate forming an uniform horizontal wetting front. However, water repellent soils will get wet after prolonged or recurrent rainfall, what results in a ponded and very wet topsoil layer resting on relatively dry and/or still water repellent soil body. In such case, infiltrated water may flow following different paths. In a water repellent soil body, water may flow laterally, and provide water to places where vertical flow paths are formed, resulting in fingered infiltration. These vertically directed preferential flow paths facilitate the rapid movement of water and solutes to the groundwater. Preferential flow paths create spatial variability in soil moisture affecting plant growth. The distribution and variation with soil depth of water repellency has been studied in fire-affected sand dunes under three different vegetation types (pine forest, shrubland and sparse herbaceous vegetation) in SW Spain. The persistence and intensity of water repellency at the exposed surface of soil was measured using the water drop penetration time test and the contact angle method, respectively, in surface samples (0- 3 cm) collected at burned and unburned areas. The variation of water repellency with depth in burned areas was studied in soil profiles every 5 cm between 0 and 40 cm depth. None or slight soil water repellency was observed at unburned soil sites, whereas burned soil sites showed a high degree of repellency, especially under pines and shrubland. The spatial pattern of fire-induced soil water repellency was found to be associated to vegetation types, although it was modulated by soil acidity and the soil organic carbon content. Soil water repellency was generally higher at the soil surface, and decreased with depth. Dense pine forests and shrublands showed strong and/or severe water repellency in depth, but it was rare and limited to the first five centimeters under sparse herbaceous vegetation. The heterogeneity of moisture patterns under dense pine forests or shrublands showed the existence of wetting and water repellent three-dimensional soil patches.
