Artemi Cerdà

Influence of vegetation recovery on soil hydrology and erodibility following fire: an 11-year investigation

The present study investigates long-term changes in soil hydrological properties and erodibility during the regrowth of different types and densities of vegetation following a severe wildfire in the Serra Grossa Range, eastern Spain. Twelve plots of similar slope and soil characteristics, naturally recolonized by four different plant species (trees, herbs, shrubs and dwarf shrubs) were examined using rainfall simulations during an 11-year period. The mean erosion rate was 80 g m−2 h−1, 6 months after the fire under wet-winter conditions, declining to 30 g m−2 h−1 in the following summer and reaching <10 g m−2 h−1 after 2 years. Considerable variation under the different vegetation types was observed. Herbs and shrubs reduced erosion and overland flow coefficients to negligible values 2 years after fire, whereas under trees and dwarf shrubs, appreciable overland flow and soil loss still occurred after 5 years. On tree-covered plots (Pinus halepensis), overland flow actually increased over time in association with the development of topsoil hydrophobicity, reaching a coefficient of 27% 10 years after burning. Rates of post-fire overland flow and erosion reduction were strongly influenced not only by vegetation coverage but also by the type of cover and its effects on soil hydrophobicity.

Soil aggregate stability under different Mediterranean vegetation types

The influence of vegetation type on soil erodibility was studied by means of aggregate stability measurements using the Modified Emerson Water Dispersion Test (MEWDT), water-drop impacts (CND and TDI) and Ultrasonic Disruption (UD) methods on soils from north-facing slopes of the mountain range of La Serra Grossa in the eastern Iberian Peninsula. Soils with similar characteristics but covered by the main plant species at the study area were selected. Quercus ilex woodland showed the most resistant soil aggregates followed by Q. coccifera and Pistacea lentiscus scrubland, Brachypodium retusum grassland and Pinus halepensis woodland. Aggregates developed beneath dwarf shrubs like Rosmarinus officinalis, Thymus vulgaris, Ulex parviflorus and Anthyllis cystisoides were least resistant. The different methods and tests applied are useful to study the soil aggregate stability. The MEWDT and TDI tests showed only minor differences between samples due to the high aggregate resistance and the low energy applied by these tests. CND and UD tests are considered to be more suitable for resistant Mediterranean soil developed on limestone due to the greater energy applied. Aggregates tested from an initially moist (pF1) condition were always more stable than air dried aggregates. Rangeland management after disturbances by fire, agriculture or grazing, etc. should try to establish natural woodland (Q. ilex) in order to get the most stable soil. Alternative vegetation cover to the climax vegetation that give high aggregate stability are Q. coccifera and P. lentiscus scrublands. Immediately after disturbance, B. retusum grassland seems to be the best option for soil protection.

Changes in overland flow and infiltration after a rangeland fire in a Mediterranean scrubland

Changes in overland flow and infiltration after a wildfire (summer 1989) in a typical Mediterranean scrubland were measured during the winters of 1990, 1991, 1992 and 1995 by means of simulated rainfall. Infiltration increases gradually from 1990 (sixth months after the forest fire) to 1995 (five and a half years after the forest fire). Overland flow decreases from 45% of rainfall after the forest fire to less than 6% five and a half years later. The reduction in overland flow was greatest in the first two years after the fire because of the quick recovery of vegetation. The steady-state infiltration capacity increased every year after the fire. Runoff and infiltration changes are mainly determined by the gradual recovery of vegetation.

The immediate effectiveness of barley straw mulch in reducing soil erodibility and surface runoff generation in Mediterranean vineyards.

Soil and water loss in agriculture is a major problem throughout the world, and especially in Mediterranean areas. Non-conservation agricultural practices have further aggravated the situation, especially in vineyards, which are affected by one of the highest rates of soil loss among cultivated lands. Therefore, it is necessary to find the right soil practices for more sustainable viticulture. In this regard, straw mulching has proven to be effective in other crop and fire affected soils, but, nonetheless, little research has been carried out in vineyards. This research tests the effect of barley straw mulching on soil erosion and surface runoff on vineyards in Eastern Spain where the soil and water losses are non-sustainable. An experiment was setup using rainfall simulation tests at 55 mm h(-1) over 1h on forty paired plots of 0.24 m(2): twenty bare and twenty straw covered. Straw cover varied from 48 to 90% with a median value of 59% as a result of the application of 75 g of straw per m(2). The use of straw mulch resulted in delayed ponding and runoff generation and, as a consequence, the median water loss decreased from 52.59 to 39.27% of the total rainfall. The straw cover reduced the median sediment concentration in runoff from 9.8 to 3.0 g L(-1) and the median total sediment detached from 70.34 to 15.62 g per experiment. The median soil erosion rate decreased from 2.81 to 0.63 Mg ha(-1)h(-1) due to the straw mulch protection. Straw mulch is very effective in reducing soil erodibility and surface runoff, and this benefit was achieved immediately after the application of the straw.

Design and operation of a small and portable rainfall simulator for rugged terrain

A rainfall simulator designed to perform experiments in rugged terrain is presented. The portability of the apparatus allows the researcher to work in remote areas and on steep slopes. Rainfall intensity and distribution within the plot (0.24 m2) and drop-size were measured under different water pressure. For the best simulated rainfall distribution (1.55 kg cm2 of water pressure and 55 mm h−1 of rain intensity) the drop velocity and the kinetic energy were measured.

The influence of aspect and vegetation on seasonal changes in erosion under rainfall simulation on a clay soil in Spain

The seasonal and spatial variability of soil erosion under contrasting slope aspects in southeastern Spain was studied by performing and interpreting 84 rainfall simulation experiments conducted at an intensity of 55 mm h−1 during 1 h. The vegetated soils on the north-facing slope and the upper afforested parts had negligible sediment yield, runoff and erosion, while the bare soils on the south-facing slope had very high runoff rates. Runoff sediment concentration decreased over time during simulated rainfall events on the vegetated areas while it increased on the bare ones. Solute release decreased over time on both surface types. Seasonally, runoff sediment concentration was highest in autumn, decreasing in winter and spring, due to the exhaustion of erodible soil and the vegetation growth. Sediment concentrations increased slightly in summer when runoff and erosion rates where very low. Increasing seasonal variability corresponded with increasing runoff and soil loss rates. Key words: Runoff, soil loss...

Influences of micro-relief patterns and plant cover on runoff related processes in badlands from Tabernas (SE Spain)

Abstract Soil surface morphology, soil thickness and their evolution strongly affect infiltration processes. Badland surfaces are characterised by a substantially low plant cover and a reduced soil development controlled by high erosion rates. In the badlands of Tabernas (Almeri´a, SE Spain), the soil surface morphology exhibits a marked spatial variability, caused by different processes under moisture and temperature alternations in different slope aspects. Previous studies on the area have revealed. the different hydrologic behaviour of North- and South-facing surfaces. In this paper, we go into more detail trying to establish the influences of both micro-relief patterns and plant cover on the hydrological behaviour of sixteen representative soil surfaces from the badlands of Tabernas. Rain simulations at a constant intensity of 55 mm/h have been carried out on 16 circular plots of 0.24 m 2 , during 30 min, to evaluate runoff, infiltration, and sediment production parameters. Surface morphology has been evaluated by image analysis of photographs, before and after the simulations the following parameters have been considered: plant cover and type, length and width of cracks, and stoniness. Surface roughness was determined with a laser profile meter. Runoff and erosion responses have been gathered in three and four groups, respectively, which are related to differences in slope gradient, soil depth and surface morphology. Runoff is positively correlated with slope gradient and negatively correlated with plant cover and total cover. Erosion is negatively correlated with lichen cover, with non-cryptogamic plant cover, with total cover and with surface area occupied by cracks. In some aspects, Tabernas badlands have an hydrological behaviour similar to other badlands described elsewhere (i.e., shallow moisture penetration, short times to runoff, different responses in runoff). However, they are particular in the following: (a) apparent morphological stability after rainfall events of high magnitude and intensity, along with high sediment production associated either from micro-rills that follow open cracks in the regolith, or from overland flow on bare, crusted, silty surfaces; (b) runoff enhancement by surface roughness through the channelling effect of the sealed depressions among pedestals and mounds of crustose lichens.

Use of barley straw residues to avoid high erosion and runoff rates on persimmon plantations in Eastern Spain under low frequency-high magnitude simulated rainfall events

Soil and water losses due to agricultural mismanagement are high and non-sustainable in many orchards. An experiment was set up with rainfall simulation at 78 mm h–1 over 1 hour on 20 paired plots of 2 m2 (bare and straw covered) in new persimmon plantations in Eastern Spain. Effects of straw cover on the control of soil and water losses were assessed. An addition of 60% straw cover (75 g m–2) resulted in delayed ponding and runoff generation and consequently reduced water losses from 60% to 13% of total rainfall. The straw cover reduced raindrop impact and thus sediment detachment from 1014 to 47 g plot–1 h–1. The erosion rate was reduced from 5.1 to 0.2 Mg ha–1 h–1. The straw mulch was found to be extremely efficient in reducing soil erosion rates.

Soil erosion after land abandonment in a semiarid environment of southeastern Spain

Different soil units were selected in southeastern Spain to investigate the effects of land abandonment on soil erosion under semiarid conditions. The study sites selected were a cultivated field (bare), a 3‐yr‐abandoned field (herbs), a 10‐yr‐abandoned field (Artemisia herba‐alba Asso.), and two soil units covered with semi‐native (Stipa tena‐cissima L) and native (Pinus halepensis Miller) vegetation. Simulated rainfall measurements showed that the erosion and runoff increased after the land abandonment, but later erosion decreased owing to the influence of increasing vegetation. Runoff discharge (35%) and the erosion rates (334 g m2 h‐1) were high in the 3‐yr‐abandoned land in comparison with the other land uses. Cultivation promotes infiltration of rainfall; as a consequence, the runoff and erosion rates were greatly reduced. Under Stipa tenacissima and Artemisia herba‐alba, site conditions were very stable because of the high infiltration rates in the vegetated patches (100% of the rain infiltrated). ...

The influence of slope angle on sediment, water and seed losses on badland landscapes

Abstract By means of simulated rainfall the influence of the slope angle on the soil, water and seed erosion has been studied on badland surfaces. Slope angle has a clear positive effect controlling soil erodibility and erosion rates, but it does not have any influence on the volume of runoff after 40 minutes of rain at an intensity of 55 mm h−1. In contrast, slope angle has a clear influence on runoff initiation, with cracks and crusts as the main factors controlling the time to ponding and time to runoff. Both ponding and runoff initiation start earlier on pediments than on slopes, where more cracks exist. Steady-state infiltration rates and seed losses have an inverse relationships with slope angle. Pediments have 40 times lower erosion rates and 6 times higher seed losses than slopes. The different behaviour of seed losses between pediment and slope is due to the strategy of the seeds against erosion processes.