Showing papers by "Artemi Cerdà published in 2010"

Soil microbial biomass and activity under different agricultural management systems in a semiarid Mediterranean agroecosystem

Abstract: A field experiment was carried out in a semiarid agricultural Mediterranean area located at the “El Teularet” experimental field in the Enguera Sierra (Valencia, southeast Spain) to assess the influence of different agricultural management systems on indicators of soil biological quality and activity (microbial biomass C, basal respiration, C mineralization coefficients, metabolic quotient (qCO2), respiratory quotient (RQ: moles CO2 evolved/moles O2 consumed), soluble C and dehydrogenase, urease, protease-BAA, phosphatase and β-glucosidase activities), one year after treatment establishment. The management practices assayed were as follows: application of the herbicides paraquat, glyphosate or oxyfluorfen, addition of olive tree pruning residues, ploughing, sowing of oats + addition of crop residues + ploughing, sowing of Medicago sativa, sowing of oats and vetch + addition of crop residues and addition of oat straw. A non-treated plot was used as control soil and a plot under natural vegetation was used as a standard of local, high quality soil. The plots with addition of oat straw had higher values of enzymatic activity, microbial biomass and respiration, reaching similar values to soil under native vegetation. The lowest levels of soil biological quality indicators were observed in the plots with application of some type of herbicide. Low RQ values were observed in these plots as consequence of the scarce-null inputs of organic matter, suggesting an increase in organic matter recalcitrance. The addition of oat straw to soil can be considered an effective technology, due to the rapid improvement of soil quality, for carrying out sustainable agriculture in semiarid Mediterranean agroecosystems.

The impact of cotton geotextiles on soil and water losses from Mediterranean rainfed agricultural land.

Abstract: High soil erosion risk of Mediterranean cultivated soils is due to steep slopes, high rainfall intensities and low vegetation cover. Traditional land management as ploughing and herbicides give rise to high soil erosion rates. This paper reports on the use of a cotton geotextiles to control soil and water losses on agricultural land under Mediterranean climatic conditions. Eight paired plots (1, 2, 4 and 16 m2) were studied during 1-year period under natural rainfall. Forty rainfall simulations under wet and dry climatic conditions, and water drop penetration time (WDPT) tests, were carried out in order to analyze the effect of a geotextile on soil and water losses on a typical rainfed orchard in Eastern Spain. Results showed that an 8 mm thick cotton geotextile reduced soil loss to negligible values (from 14 to 0·1 Mg ha−1 y−1) due to the low sediment concentration as geotextile covered 100% of the soil. However, infiltration rates decreased and runoff increased due to the hydrophobic response of the cotton material. The runoff discharge increased from 8% to 16% for the 2004 period under natural rainfall and from 27% to 87% under simulated rainfall when summer dry conditions were reached. The cotton geotextile reduced local soil losses at plot-scale, but increased runoff. Copyright © 2010 John Wiley & Sons, Ltd.

Contribution of the largest events to suspended sediment transport across the USA

Abstract: This work analyses the contribution of the largest events to suspended sediment transport on the continental scale. The analysis is based on the United States Geological Survey (USGS) Suspended Sediment and Ancillary database. Data were obtained from 1314 catchments, comprising more than 2 500 000 daily events. The total number of days in the dataset amounts to 10 000 years. Catchments are of different sizes and belong to distinct climatic environments; they are distributed for the analysis according to USA hydrological divisions (HDs). The main objective of the research is to examine the effect of the n-largest event on the total suspended sediment load over recorded periods, and to discuss different behaviour between HDs. To accomplish this, the daily events at each catchment are ranked by magnitude, and then the percentage represented by the n-largest event (e.g. 3-largest, 5-largest, 10-largest, 15-largest, 20-largest, 25-largest) is calculated from the total accumulated load. Results indicate that suspended sediment transported by the 25-largest events represents on average more than 50 per cent of the total load. The California HD, mostly under Mediterranean climatic conditions, accounts for the highest percentage of sediment transport across conterminous USA, whatever n-largest daily events are selected. There, the 3-largest events contribute, on average, 38 per cent of the total sediment load, the 10-largest events represent 61 per cent and the 25-largest events produce more than 76 per cent of the total sediment transport. Overall, the contribution of largest daily events seems not to depend on the climatic conditions in small catchments (<100 km2) and, in addition, the percentage of suspended sediment increases over all HDs, while, at the same time, the catchment size decreases. Finally, we discuss differences between catchments across the USA, according to climatic and historical (i.e. land use) factors. Copyright © 2009 John Wiley & Sons, Ltd.

Seed removal susceptibility through soil erosion shapes vegetation composition

Abstract: Soil erosion and vegetation cover are negatively related in semiarid slopes due to the influence of erosion on important soil surface properties for plant establishment and development, but also because the removal of seeds and plants. Previous published work concluded that seed mass is the main factor explaining the seed susceptibility to removal by soil erosion but that this susceptibility can be modified by the presence of seed appendages (hairs, wings, awns) and the ability of seeds to segregate mucilage in contact with water. In the present work we first analyzed how the presence of seed appendages and the ability of seeds to segregate mucilage modify the susceptibility of seeds to removal by soil erosion, and then if soil erosion, through its effects on seed removal can explain plant community composition of semiarid slopes. Results indicate that segregation of mucilage reduces seed susceptibility to be removed and that this seed susceptibility to removal is lower for plants living on steep slopes than that of species living in communities of flat sites. We then argue that soil erosion by water has the potential to affect plant communities of semi-arid Mediterranean slopes.

Ecohydrological adaptation of soils following land abandonment in a semi-arid environment.

Abstract: Representative land use types were selected in southeast Spain to investigate the redistribution of soil water in relation to vegetation development and land abandonment. Simulated rainfall experiments were performed during 2 days on each of the four selected surfaces: ploughed, a 3-year fallow field, a 12-year abandoned field with shrubs and a semi-natural field with Stipa tenacissima tussocks. Each experiment consisted of five runs of artificial rain. Soil moisture dynamics were measured by time domain reflectometry (TDR), as well as runoff and ponding on the plot surface. Also the movement of the wetting front was measured after each run. On the ploughed field, ponding and local runoff were less important with shallow and homogeneous wetting fronts. The other land uses showed increased heterogeneity in wetting front development, with soil water pockets under the plants that moved down at greater velocities than under the bare inter-spaces. It is hypothesized that S. tenacissima and possibly Artemisia herba-alba adapt their environment by capturing water through stem-root flow systems to divert water to deeper soil layers to reduce evaporation. Furthermore it is suggested that during vegetation development soil heterogeneity increases, as expressed by the water infiltration patterns observed, and that the bare inter-patches are important in the infiltration process.

The effect of ant mounds on overland flow and soil erodibility following a wildfire in eastern Spain

Abstract: This study examines the soil hydrological and erosional effects of ant mounds during summer and winter conditions following a wildfire in scrub terrain in eastern Spain. Forty rainfall simulations (1 m2 plots, 1 h duration, 78 mm h−1 intensity) were carried out over plots with mounds (n = 20) and mound-free control plots (n = 20) in August 2002, and repeated in December. By winter, some of the mound material had been removed and some vegetation regrowth occurred. Overall, mound presence increased soil erodibility in summer and winter due to the availability of highly erodible mound material. However, mound plots showed higher mean overland flow rates in summer (10·1 vs 6·9% for control plots) but lower rates in winter (59·3 vs 74·4% for control plots). This reversal is suggested to be caused by (i) post-fire changes in ground cover and (ii) seasonal differences in antecedent soil moisture. First, immediately after burning, an absorbent ash layer covered much of the soil surface, but this was partially masked by less permeable mound material, reducing infiltration on mound plots. By winter, the ash layer had been largely removed and ash particles clogged soil surface pores, reducing overall infiltration on control plots compared to mound plots. Second, during summer, the dry soil underneath the absorbent ash cover has a high infiltration capacity. In winter, soils are near saturation, resulting in a much greater runoff coefficient. Under these wet soil conditions, the presence of macropores (i.e. nest entrances) becomes important, reducing overland flow in mound plots. Copyright © 2010 John Wiley & Sons, Ltd.

Actualización en métodos y técnicas para el estudio de los suelos afectados por incendios forestales

Abstract: espanolLos cientificos espanoles que estudian los suelos afectados por los incendios forestales son una comunidad dinamica y con proyeccion internacional Los investigadores espanoles son creativos y aportan a la comunidad cientifica nuevos avances en metodos y tecnicas para conocer los efectos del fuego sobre los suelos Ademas, las intensas relaciones con otros grupos de investigacion fuera de nuestras fronteras han permitido una permeabilidad a los grupos de investigacion espanoles que les ha llevado a utilizar y mejorar las tecnicas desarrolladas en otros paises Este libro revisa el uso de los metodos y tecnicas aplicadas para conocer y entender el efecto de los incendios a largo, medio y corto plazo Se revisan tecnicas novedosas, se actualizan aquellas con mas solera y se presenta el modo y la forma de trabajar para avanzar en el conocimiento cientifico catalaEls cientifics espanyols que estudien els sols afectats pels incendis forestals son una comunitat dinamica i amb projeccio internacional Els investigadors espanyols son creatius i aporten a la comunitat cientifica nous avancos en metodes i tecniques per coneixer els efectes del foc sobre els sols A mes, les intenses relacions amb altres grups d'investigacio fora de les nostres fronteres han permes una permeabilitat als grups d'investigacio espanyols que els ha portat a utilitzar i millorar les tecniques desenvolupades en altres paisos Aquest llibre revisa l'us dels metodes i tecniques aplicades per coneixer i entendre l'efecte dels incendis a llarg, mitja i curt termini Es revisen tecniques noves, s'actualitzen aquelles amb mes tradicio i es presenta la manera i la forma de treballar per avancar en el coneixement cientific

Biohydrology: coupling biology and soil hydrology from pores to landscapes

Abstract: The articles in this issue are a selection of the presentations made at the 2nd International Conference of Biohydrology. This special issue ‘Biohydrology—coupling biology and soil hydrology from pores to landscapes’ contains a range of articles on biological and hydrological interactions in soil, including large-scale systems research on the influence of forests on catchments and small-scale reductionist research on processes operating at the scale of soil pores. Copyright  2010 John Wiley & Sons, Ltd.

Designing laboratory rainfall simulation experiments to examine the effects of a layer of vegetative ash on soil hydrology in Mediterranean areas

Abstract: Vegetative ash formed during forest wildfires often blankets the ground. Some studies have found the ash layer to increases infiltration by storing rainfall and protecting the underlying soil from sealing (Cerda and Doerr, 2008; Woods and Balfour, 2008), but at the same time, others identified it as a potential cause of increased overland flow due to sealing the soil pores or crusting (Mallik et al., 1984; Onda et al., 2008). The variability in the effects of ash depends mainly on the ash type and temperature of combustion, ash thickness and soil type (Kinner and Moody, 2007; Larsen et al., 2009). In order to study the effect of the ash layer on the soil hydrology and soil erosion under i) intense thunderstorms, ii) wettable and water repellent soil and iii) different ash thicknesses, rainfall simulation experiments were performed in a small plot (0.09 m2) in order to reach the highest accuracy. The simulator comprises a constant head tank of 40x40 cm with 190 hypodermic needles of 0.5 mm. A randomization screen served to break up the raindrops and ensure random drop landing positions (Kamphorst, 1987). The average of the intensities applied in the experiment was 82.5 ± 4.13 mm h-1 during 40 minutes. In order to verify the constancy of the intensity it was measured before and after each simulation. The rainfall was conducted in a metal box of 30x30 cm within 1 m of distance from the randomization screen. The slope of the box was set at 10° (17%). It is designed to collect overland flow and subsurface flow through the soil. Each rainfall simulation was conducted on 3 cm of both wettable and water repellent soil (WDPT>7200s). They are the same soil but one transformed into hydrophobic. The treatments carried out are: a) bare soil, b) 5 mm of ash depth, c) 15 mm of ash depth and d) 30 mm of ash depth, with three replicates. The ash was collected from a wildfire and the thicknesses are in the range of the reported in the literature. The first replicate was used for analysis of water repellency, infiltration pattern and ash incorporation into the soil and the other replicates are used for a second rainfall, one after 24 hours and the other after being dried 4 days in the oven at 25oC. In total there were 40 simulations. Overland flow and subsurface drainage were collected at 1-minute intervals and the forms was stored every 5 min to allow determination of sediment concentrations, yield and erosion rates. The experiment was completed with the installation of two moisture sensors at 1.5 cm of the soil and four splash cups that allowed determining the splash detachment at the end on the simulation. The importance in this series of experiments is the reproducibility and comparison of the different thicknesses of ash with the wettable and repellent soil. The results demonstrate that ash is a key factor on the post-fire soil erosion and hydrology and that rainfall simulation is a key tool to improve knowledge on low frequency – high magnitude events.

Effects of a layer of vegetative ash layer on wettable and water repellent soil hydrology

Abstract: Following a wildfire, a layer of vegetative ash often covers the ground until it is dissolved or redistributed by wind and water erosion. Much of the existing literature suggests that the ash layer temporally reduces infiltration by clogging soil pores or by forming a surface crust (Mallik et al., 1984; Onda et al., 2008). However, an increasing number of field-based studies have found that, at least in the short term, ash increases infiltration by storing rainfall and protecting the underlying soil from sealing (Cerda and Doerr, 2008; Woods and Balfour, 2008). On the other hand, after a fire the soil may have produced, enhanced or reduced its water repellency (Doerr et al., 2000). Very few studies have been taken into account the interaction of the ash and the repellent soil. The layer of ash may have similar role as a litter layer in delaying runoff and reducing erosion by storing water. In order to examine this interaction, it was been made a series of experiments using a laboratory rainfall simulation. It has been assessed the effects of an ash layer i) on a wettable and water repellent soil (WDPT > 7200s), ii) with different ash thicknesses (bare soil and 5 mm, 15 mm and 30 mm of ash), iii) preceding and following the first rain after a fire when the ground is still wetted and after being partially dried. Three replicates were done, being a total of 40 simulations. The ash used was collected from a Wildfire in Teruel (Spain) during summer of 2009. The simulations were conducted in metal boxes of 30x30 cm and filled with 3 cm of soil. The slope of the box was set at 10° (17%) and the intensity applied was 78-84 mm h-1during 40 minutes. The splash detachment was determined also using four splash cups. Overland flow and subsurface drainage was collected at 1-minute intervals and the former stored every 5 min to allow determination of sediment concentrations, yield and erosion rates. Each sample was examined at the end in terms of water repellency, infiltration pattern and ash incorporation into the soil. The results show that when ash covers the wettable soil, runoff occur for a short period of time in the middle of the event. It occurred latter on time but larger in quantity as the ash thickness increases (from 0% to 2% of runoff coefficient) and at the same time drainage is reduced (from 57 to 24%). This suggests that the ash layer became saturated and produce runoff until the water is able to drain into the soil. Oppositely, in water repellent soil as ash thickness increases both runoff is reduced (from 78% to 26%) and drainage is increased (from 0 to 16%). That fact indicates a modification in the hydraulic conductivity of the repellent soil due to the pressure of the ash layer. Splash and erosion rates are bigger in water repellent soils yet erosion rates never exceed 2.5 g m-2 h-1. The fact of wetting increases the runoff and drainage rates in wettable but reduce them in the water repellent soil. An irregular infiltration pattern is observed afterwards. After drying the soil, the increase in runoff indicates a crust formation. Moreover, in water repellent soils part of the repellency is reestablished. These findings demonstrate that the interaction of the soil-ash layer should be considered and better studied in the immediate hydrological response after wildfire due to its particular behavior.