Giovanni Pardini

Land use change effects on abandoned terraced soils in a Mediterranean catchment, NE Spain

Abstract The Serra de Rodes catchment (NE Spain), enclosed in the Natural Park of Cap de Creus, represents a typical Mediterranean ecosystem. This semiarid environment, with hot summers and mild winters, has been progressively abandoned by farmers during the last century. Nowadays, most of hillside soils are abandoned and only small patches of vineyards and olive trees are cultivated with very low management and incomes. In this study, we have assessed the effects of land use and land use change on the main soil quality parameters. Along two altitudinal gradients, we selected 11 random environments representative of the current land uses, in sequence from cultivated to early abandonment. The different vegetation stages were grouped in four main land use types according to the age of abandonment: cultivated fields (vineyard and olive trees, 0 years), recent abandonment (dense and cleared shrubs, 5 years), mid-abandonment (cleared cork trees and dense olive trees, 25 years) and early abandonment (dense cork trees and pine trees reforestation, 50 years). Erosion plots were installed in the previously selected environments for soil physicochemical characterisation, throughout 1-year observation, monitoring nutrient losses, runoff volume and sediment yield data. Analysis of variance (ANOVA) indicates significant differences in the main soil quality parameters such as soil organic matter (SOM), total nitrogen (N), water holding capacity (WHC) and pH, among the selected environments under different land use conditions. Factor analysis of the principal components (PCA) enabled the identification of three soil quality indices: index of soil erosion and nutrient losses (SENL), index of soil quality and fertility (SQF) and index of vegetation cover and soil protection (VCP). Soil organic matter, nutrient supply, soil vegetation cover and soil compaction are critical for soil degradation in these environments and they must be managed appropriately in order to ensure continuous soil rehabilitation. Furthermore, the main conclusion that may be drawn from this study is the significant influence of land use on the main soil quality parameters.

Regolith behaviour and physical weathering of clayey mudrock as dependent on seasonal weather conditions in a badland area at Vallcebre, Eastern Pyrenees

Abstract Studies on badland areas in the Vallcebre basin (Pyrenees) suggest that erosion rates are controlled by the weathering rate of mudrocks. To obtain the temporal pattern of physical weathering and its control on the erosive processes, monitoring of regolith temperatures at different aspect, depth and lithology, and periodical determination of regolith moisture and bulk density were carried out. Changes in surface regolith have also been monitored by means of photographic techniques, using an especially designed tripod. Finally, the hydrological and erosive response of the regolith trough the seasons were studied using rainfall simulations. The results obtained support and confirm previous knowledge on the role of frost action in mudrock weathering and the role of subsequent regolith development and wetness status on infiltration and runoff generation. These seasonal changes of behaviour are so important that they raise serious questions about the validity of observations or experiments carried out in only one season. This work confirms that erosion processes are controlled by regolith formation during winter and regolith depletion by storm rainfall erosion during summer, spring and early autumn. It also raises important points about annual trends of infiltration and erodibility, that should be used as guidelines for modelling runoff and sediment production.

Runoff erosion and nutrient depletion in five Mediterranean soils of NE Spain under different land use.

We investigated the influence of agricultural management and various plant covers related to the period of abandonment on soil properties, erosion and nutrient depletion in a typical Mediterranean area with sandy loam shallow soils. Cultivated soils (CS) with insufficient management, 5 year abandoned soils covered with meadow (A5), 25 year abandoned soils covered with dense scrubs (A25), 50 year abandoned soils covered with cork trees (A50) and soils in a 50 year pine reforested area (P50) were studied over a period of 6 months (May-October 1999). The soils were classified as Lithic Xerorthents. Both the differences in soil properties and response to rainfall events were mainly attributed to the different vegetation types and stages in land management. Principal components analysis (PCA) was performed on the results, by running the overall data determined after five rainfall events. The factors extracted by PCA of the samples by variables matrix represented the response of the environments to different rainfall intensities as a function of management or natural evolution after abandonment. CS environments showed the highest runoff and sediment yield as well as the highest amount of dissolved organic carbon (DOC) and nitrogen in runoff water. The sequence of abandonment (A5, A25 and A50) showed approximately the same runoff production, whereas eroded sediments (ES) and DOC were inversely correlated. Organic carbon in the ES and DOC in runoff water always increased with the period of abandonment, which accounted for consistent nutrient depletion. Nevertheless, the A50 environment (dominated by Quercus suber) showed the best soil properties, whilst the A25 environment with dense cover of Cistus monspeliensis and Calicotome espinosa seemed to cause a worsening effect on the soils physical and chemical properties. This is probably because these environments are more severely damaged by wild fire occurrence. In terms of sediment yield, the P50 environment followed CS environment, indicating that reforestation followed by insufficient forest management may negatively affect both soil properties and response to the erosive action of rainfall.

How mudrock and soil physical properties influence badland formation at Vallcebre (Pre-Pyrenees, NE Spain)

Abstract Soils, regoliths and their parent materials were investigated in relation to the development of badlands in the Pre-Pyrenees, in NE Spain, on Late Cretaceous mudrocks under a mountain Mediterranean climate. Whilst all the soils in the area which are developed on mudrocks show a good structure and support a dense plant cover, the bare parent materials slake very rapidly giving rise to badlands characterized by high erosion rates. Several physical, chemical, mineralogical and micromorphological properties of soils, regoliths and related parent materials were analyzed in order to explain their different susceptibility to erosion and to determine which of all these properties are better related to such erosive behaviour. Only micromorphological and porosity properties were able to explain the erosion susceptibility, whilst mineralogical, chemical and physico-chemical (specific surface area) properties were not. Among the aggregate stability tests performed to estimate the relationships of soil components with the susceptibility to erosion, the Emerson test for macroaggregate evaluation, was particularly well suited. Although no good correlation was found between the Emerson test classes and organic matter content, we observed that the degree of slaking in organic-rich horizons, was always lower than in subsurface horizons and regoliths. Consequently, as far as organic rich aggregates are present in the soil surface, the influence of water in producing slaking, swelling and then erosion, will be minimum. However, when regoliths and rocks are uncovered, the influence of water in these particular materials, through freeze-drying and swell-shrinking, will give rise to mudrock desintegration leading to accelerated erosion.

Fractal scaling of surface roughness in artificially weathered smectite-rich soil regoliths

Abstract Laboratory trials were established to simulate, under controlled conditions, the natural weathering sequence of smectite-rich soil regoliths from a highly degraded badland area at Vallcebre, Eastern Pyrenees Range (Spain). Experiments were carried out to deepen the knowledge on the response of the bulk materials to experimental freezing–thawing and wetting–drying cycles, and the role of the mineral components in the path of surface structure detachment. During the experiments, variation of surface roughness was determined by measuring consecutive transects of the artificially weathered samples with a noncontact laser profile meter and data were analysed with a program written for this purpose. The analysis of data was based on the calculation of the fractal dimension, according to the Richardson equation, of sequential surface profiles of samples in frozen, thawed, wetted and dried conditions in order to achieve a dynamic description of surface aggregate shape arrangement along the whole sequence and at different scale ranges. The Hurst exponent of selected bulk data was also calculated in order to find added evidence of the nature of surface, which, in some cases, appeared to be multifractal with the Richardson diagram. The fractal model applied allowed to obtain fractal dimension values of surface roughness which were used to explain how the pedological characteristics of a given material containing clay and carbonate association may react to applied climatic extremes, thereby showing differential surface arrangement and weathering paths. Freezing and thawing as well as wetting and drying events modified the samples surface, and these effects describe the material susceptibility to weathering against individual climatic components and may be useful in erosion modelling at the catchment scale.

Distribution Patterns of Soil Properties in a Rural Mediterranean Area in Northeastern Spain

Abstract Soil properties on the Cap de Creus Peninsula, NE Spain depend primarily on scarce agricultural practices and early abandonment. In the study area, 90% of which is mainly covered by Cistus shrubs, 8 environments representing variations in land use/land cover and soil properties at different depths were identified. In each environment variously vegetated areas were selected and sampled. The soils, collected at different depths, were classified as Lithic Xerorthents according to the United States Department of Agriculture system of soil classification (USDA-NRCS 1975). Differences in soil properties were largely found according to the evolution of the plant canopy and the land use history. To identify underlying patterns in soil properties related to environmental evolution, factor analysis was performed and factor scores were used to determine how the factor patterns varied between soil variables, soil depths and selected environments. The three-factor model always accounted for 80% of the total variation in the data at the different soil depths. Organic matter was the more relevant soil property at 0–2 cm depth, whereas active minerals (silt and clay) were found to be the most relevant soil parameters controlling soil dynamics at the other depths investigated. Results showed that vineyards and olive tree soils are poorly developed and present worse conditions for mineral and organic compounds. Analysis of factor scores allowed independent assessment of soils, depth and plant cover and demonstrated that soils present the best physico-chemical characteristics under Erica arborea and meadows. In contrast, soils under Cistus monspeliensis were less nutrient rich and less well structured.

Rainfall/runoff/erosion relationships and soil properties survey in abandoned shallow soils of NE Spain

PurposeShallow soils previously cultivated under terraced systems may change their properties after agricultural release and spontaneous plant colonization. Investigations were conducted in terraced fields (NE Spain) to prove that vegetation installed after the abandonment may generally improve soil properties by the formation of stable organic horizons. However, restriction in plant species along the natural vegetation succession and intensification of erosion processes may occur after abandonment depending on fire frequency and soil use history.Materials and methodsTen environments with different plant covers under a Lithic Xerorthent were selected and erosion plots (Gerlach type) installed providing their best adaptability at the terrace scale. Selected soil environments represented the sequence of abandonment: from current poorly cultivated soils, soils under pasture, soils under shrubs, and soils under stands of pine and cork trees. Relevant rainfall events producing runoff and erosion were recorded from November 2011 to May 2012. Erosion rates and erosion components were analysed in sediments and water in order to monitor carbon, nitrogen and other nutrient removal by overland flow. Similarly, the physical and chemical properties of the soil environments under study were determined at the same time interval of runoff erosion.Results and discussionSoils under pasture, vines and recently burnt pine forest produced the highest runoff followed by soils under shrubs and forest. However, eroded soil yields and nutrient removal were much higher in cultivated soils and soils in recently burnt sites, which had shown poorer soil properties with respect to soils abandoned for longer and preserved by fire. Fire-affected soil environments also showed a thinner organic horizon and reduced water retention. Although erosion rates and nutrient depletion were low in all environments with respect to other areas of Spain, higher splash than water erosion was an early warning indicator of the high susceptibility to degradation of these shallow soils.ConclusionsResults outlined that the renaturalization dynamics after agricultural abandonment are complex biophysical processes involving the parent material, depth to bedrock and other soil properties as well as the succession of vegetative cover and plant associations responsible for building a new soil mantle contrasting with erosion processes. Planning for management of land abandonment is strongly recommended.

Remediation Potential of Forest Forming Tree Species Within Northern Steppe Reclamation Stands

Abstract The aim of the research was to study the features of accumulation of heavy metals by assimilation apparatus of coniferous and deciduous arboreous plants. The research identified excess of factual concentrations for Arsenic in mining rock in relation to values stated in IPC (indicative permissible concentrations). It is stated that the metals can be divided into three groups according to their absolute content in unit of foliage biomass. The element of excessive concentration is Mn, medium concentration is characteristic for Pb and Zn and low concentration is observed for Sb, Cr, As, Cu, Ni and Sn. Calculation of coefficient of biological accumulation of the metals under research has shown its high values for Crimean pine. The data presented for Black locust indicate low values of coefficient of biological accumulation, which is best noticeable for Chromium, Antimony and Tin. It is determined that a small amount of Sb and Sn are a subject to uptake by Black locust leaves, whilst for Crimean pine needles, Sb and As are characterised by the lowest inflow. The average content of lead is 209.11 kg·ha−1 for Crimean pine in all age groups of trees, whilst for Black locust, this index is only 15.52 kg·ha−1, which is 13.5 times less. Zinc accumulation is better performed by Black locust leaves, and it gradually decreases with increasing age. No definite trend of redistribution and subsequent accumulation of copper depending on tree species and age was found.