Clara Martí

Abstract: A macro- and micromorphologic study was done on the soils from a stepped sequence of seven dated fluvial terraces in the lower Segre river valley (Lleida, northeast Spain) under a present-day semiarid Mediterranean climate. The soils have evolved from the Holocene through the early Pleistocene, providing an excellent morphostratigraphic framework for evaluating time-dependent factors influencing soil formation in a dry and calcareous environment. Throughout the chronosequence, some properties are regularly age-related specially carbonatation in subsurface horizons. The carbonates occur mainly as micrite, and although microsparite and sparite also appear in the oldest soils, they are replaced by fine-grained calcite by dissolution-reprecipitation processes (micritization process), which is active at present. Some pedological paleofeatures as the presence of sparite and recarbonated argillans in oldest terrace can be interpreted as the reflex of climatic changes during the Quaternary. In spite of this climate variability. the soils display progressive and systematic patterns of carbonate accumulation: on the lowest terraces. the soils do not yet have secondary carbonates but in the beginning Late Pleistocene calcic horizons, with carbonate pendents, are developed; these pendents increase its thickness with age although pendent growth rates decreases from Late Pleistocene to Middle Pleistocene. In the middle of the Late Pleistocene, calcic horizons evolved to petrocalcic horizons, which increase its thickness in the Middle and specially in Early Pleistocene. The presence of calcic and petrocalcic horizons is the primary basis for soil classification. This criterion is applicable not only to the soils of the lower Segre river basin, but also to many soils throughout the semiarid Mediterranean region. (C) 2008 Elsevier B.V. All rights reserved.

Abstract: Livestock management may be an important variable controlling the distribution of soil chemistry in grazed summer pastures. Flocks congregate in some areas, produce spatial segregation of excretion. The study goal was to quantify the temporal variation (at the beginning and end of a summer grazing period) and the spatial variation in soil chemical properties in long-term livestock camping areas. In six linear transects, five topsoil sample points were obtained at 1, 20, 40, 60, and 80 meters from the centre of the camping areas to the surrounding Nardus stricta-dominant pasture that has been grazed for centuries. Soil available nutrients, total nitrogen (N), and organic carbon (C) increased linearly from 60 in towards the centre of the camping area as a result of stock concentration. Available N (nitrate, ammonium), phosphorus, potassium, and calcium were at least three times greater at the centre compared to surroundings. At, the end of the grazing period, cations (potassium, ammonium, magnesium) and organic C and N increased significantly at the centre in contrast with the mobile anions (nitrates and phosphates) easily lost or absorbed by plants. Long-term livestock grazing with permanent camping areas resulted in significant lateral and temporal increases of available nutrients in higher quantities than ecosystem can recycle. A reduction in stocking rate by paddock or rotation among different camping areas would aid in managing soil nutrients more effectively.

Abstract: A set of experiments with a rainfall simulator was performed in the field to evaluate the efficiency of parallel contour seeding as a post-fire restoration strategy in the arid central Ebro Valley (NE Spain). Rainfall simulations were conducted in spring, after seeded plant development, on calcareous and gypsiferous soils, with the same experimental design (two-soil treatments-seeded and nonseeded-per two soil types and per nine replicates). The parallel contour seeding treatment increases soil cover and soil surface roughness, which significantly ameliorates the hydrological and erosional response of both calcareous and gypsiferous burned soils. Seeding decreased soil loss, both in calcareous (23- fold) and gypsiferous soils (4- fold). In addition, it decreased the sediment concentration of runoff for calcareous (6- fold) and gypsiferous soils (2- fold) and the runoff coefficient for calcareous (3.5- fold) and gypsiferous soils (1.5- fold). On the other hand, seeding increased the steady state infiltration rate (3- fold), as well as surface soil moisture (1.2- fold) and wetting front depth (2- fold), with a similar order of magnitude for both soils. Time to runoff and runoff quality (electrical conductivity [EC] and pH) were not affected by seeding. Gypsiferous soils had a higher soil loss, runoff coefficient, and EC flow and a lower time to runoff, steady state infiltration rate, and wetting front depth than calcareous soils. Some of these differences were directly related to differences in soil gypsum and carbonate content (i. e., EC and pH of water runoff) and others are related to the proportion of surface soil protection, an indirect effect of soil characteristics. The results suggest that parallel contour seeding is an effective restoration measure with a short-term response that allows conservation of water and soil on recently burned arid lands, especially in situations of high erosion risk as occurs with soils with low plant cover.

Abstract: A study on the effects of fire and torrential rainfall on the soil erosion and hydrology of Pinus halepensis L. forest of the semi-arid Central Ebro Valley (NE-Spain) were carried out. A portable sprinkler-based rainfall simulator was used with two levels of rainfall energy (12,6Jm(-2)mm(-1) and 24,7 J m(-2)mm(-1)) and similar intensity (85 +/- 18 mm h(-1)). Rainfall simulations were conduced immediately after artificial burn of litter cover on nine different micro-plots and compared with paired unburned areas (2-soil status x 2 rainfall energies x 9 plots or replicates). In each rainfall simulation, the soil loss, soil infiltration (calculated by Horton model, wetting front, runoff coefficient, and runoff quality (EC and pH) were measured Fire increased significantly the sediment loss: 18.5 times with fine rainfall and 33.6 with coarse rainfall Sediment losses were as solutes dissolved in overland flow, mainly in unburned plots, and as particles in suspension, mainly in burned plots. Fire increased runoff quantity (about 1. 6 times) and decreased quality (by increasing significantly both EC and pH). These results indicate that when litter cover was burned, first rainfalls duplicate runoff and increase 20-30 times soil erosion in relation to unburned plots, especially with high rainfall energy. Soil infiltration decreased significantly in burned plots, with the highest rainfall energy. Because there is a high post-fire degradation risk, a restoration strategy for a short-term response should be designed on steep slopes with erodible soils, especially in and Mediterranean areas where torrential rainfall and wildfire are highly probable and their occurrence will increase with climate change.

Abstract: In landscape reconstruction in an opencast coal mine, a gradient of slopes can be obtained. The slope gradient can affect different processes, such as plant growth, especially in semi-arid conditions. On the other hand, to favor the heterogeneity of habitats and ensure long-term restoration, late successional woody species have been planted but with heterogeneous results. In this study, the effect of a slope gradient (from 11.4 to 15.5 degrees) on the growth and survival of five Mediterranean woody species 10 years after the reconstruction of mining banks was evaluated. Slope gradient reduced height growth significantly from 10 cm degree(-1) (lentish) to 25 cm degree(-1) (pine) in 10-year- old woody species. This gradient also reduced basal diameter growth from 0.22 mm degree(-1) (juniper) to 0.58 mm degree(-1) (pine). Survival and slope were not significantly correlated. Growth and survival of the 10-year- old woody species were equal to or higher than those of the same species in other afforestations in semi-arid conditions. This outcome demonstrates the adequacy of species and applied techniques of restoration that allow a long-term reliability of reclaimed mine slopes.

Abstract: Six different microsatellite loci (VVS2, VVMD5, VVMD7, ssrVrZAG47, ssrVrZAG62, and ssrVrZAG79) have been used in order to characterize 12 presumed accessions of Spanish 'Parraleta' cultivar and two of 'Graciano' cultivar. No differences were detected among the accessions of 'Parraleta'. Its allelic profile indicates a probable synonymy with other minor cultivars such as 'Ribote', 'Bomogastro' and 'Salceno Negro'. The two accessions of 'Graciano' analyzed differed in the six microsatellite loci. 'Graciano 17-15' was coincident to the 'Rojal' cultivar in all the analyzed alleles as well as in the ampelographic description. 'Parraleta' and 'Graciano 15-5' are thought to be closely related because they share 58% of the alleles for the loci analyzed. (C) 2004 Elsevier B.V. All rights reserved.

Abstract: The effect of heating and ash deposition on microbiological properties was studied in two arid soils in an incubation experiment, simulating the effects of bushfire. Top soil (0-15 cm) was heated to 150degreesC, 250degreesC and 500degreesC for 30 minutes; unheated soil was taken as a control (25degreesC). Samples of the soil heated to 250degreesC were mixed with black ash (1%, w/w) for analysis of their effect on microbial population and activity. Soils were incubated for nine months and their basal respiration was assessed three times a month. Normalized and specific respiration, biomass-C, bacteria, and fungi numbers were analyzed one month after heating and in the final month of incubation to assess short-term and long-term effects of fire on soil microbiology. At the start of the incubation period and for intermediate heating treatments (150degreesC and 250degreesC), basal and specific soil respiration and biomass-C were enhanced in calcareous soil but depleted in gypsiferous soil. At the highest temperature (500degreesC), these biological properties, as well as specific respiration and colony forming units, were significantly reduced in both soil types and for each period of sampling. At the end of the incubation period, all biological properties maintained the differences between treatments but with lower values than at the beginning of the incubation. Black ash addition increased basal respiration in both soils but did not affect other biological properties. These results demonstrate the existence of both labile and permanent effects of soil burning and a differential response on C dynamics as a function of soil properties.

Abstract: Fire passage is accompanied by a heat wave and ash deposition affecting the upper soil layer. Changes in soil properties are directly related to heat intensity, the amounts of ashes deposited, and soil type. We subjected two soils (gypsiferous soil and calcareous soil) to artificial heating and ash incorporation and compared changes in select chemical and physical properties. The two soils studied were selected to provide a wide range of characteristics in soils of the semiarid Ebro Valley (NE Spain). Samples of both soils were heated for 30 minutes in a muffle furnace at temperatures of 25degrees, 150degrees, 250degrees and 500degreesC. Ashes were added only on soil samples heated at 250degreesC in a quantity related to plant biomass growing on each soil (twice the amount in calcareous soil than in gypsiferous soil). Increasing heat intensity increased organic matter combustion as well as nutrient availability. Heating soil to 250degreesC caused a decrease in pH and an increase in electrolytic conductivity (ECe) and soluble Ca. Heating soil to 500degreesC caused an increase in pH and a decrease in ECe and soluble Ca. Total N content decreased at temperatures greater than 250degreesC, with about one-third being volatilized. Changes in chemical properties were similar for both soils although quantitative differences between soils were found. Cation exchange capacity (CEC) was reduced for gypsiferous soil heated to 500degreesC and to 250degreesC for calcareous soil. Heating increased sand-sized particles by fusion of clay, greatest in soil heated to 500degreesC. Soil aggregate stability (SAS) of both soils was reduced by heating to 250degreesC with greater reductions at 500degreesC, likely due to a reduction in organic matter and clay size particle content. A negative correlation was observed among SAS and soil erodibility (K-USLE). Bulk density and particle density increased in both soils when heated to 500degreesC. Water availability increased when soils were heated to 500degreesC likely due to texture and structural modifications. Addition of the ashes increased organic matter content, C/N ratio, and pH in both soils and increased nutrient availability. These responses were greater in calcareous, than in gypsiferous soil. Physical soil properties were not significantly modified by ash addition.