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Aligning with people’s values in landscape political decisions can help to minimise conflicts between stakeholders and support social acceptability of solutions for systemic transitions. This paper explores how shared and diverging values of the main stakeholders involved in socio-ecological crises, and the co-creation of solutions, can be key for finding common grounds for conflict resolution and sustainable socio-ecosystems management. These concepts were applied by a participatory process to identify and select solutions for the environmental and socio-economic crisis of the Mar Menor coastal lagoon and its watershed (SE Spain). With information from six sectorial workshops and one multisector workshop, a stakeholder analysis based on values and initiatives was performed. The results indicate that all the stakeholder groups prioritised transition to governance, economic and educational models that respect nature and cultural landscapes, with values aligning with the population’s identity and their livelihoods. The values and solutions linked with stakeholders ‘Farmers’, which represented the dominant model of high intensive agriculture in the area, differentiated most from the other stakeholders directly affected by the impact of their activities, such as ‘Fishers and salt producers’, ‘Tourism sector’ and ‘Local population’. Despite marked similarity in the underlying values among most stakeholders, reaching an agreement on initiatives can still be difficult. Therefore, we propose a conceptual model to find common grounds for negotiation based on shared values and initiatives. In those cases in which no common ground is found and disagreement persists, rules and enforcement are needed to protect all stakeholders’ sustainable development and livelihood.

This publication documents the co-design process of the Business Roadmap and policy recommendations (BRM) for sustainable development of the Mar Menor and surrounding Campo de Cartagena, and of the System Dynamics model to evaluate the impacts of the BRM on Key Performance Indicators (KPI) under different scenarios of socioeconomic, political and climate change. After presenting the co-design process and the modelled impacts on KPI it provides a short overview of featured results. The Business Road Map and Policy Recommendations (BRM) consists of the following 4 milestones and related 14 solutions: (I) Rural ecotourism: 1) The promotion of rural ecotourism activities. (II) Coastal ecotourism: 2) The promotion of coastal ecotourism activities. (III) Sustainable agriculture: 3) Implementation of nutrients, soil, and water retention measures 4) Reduction in fertilizer use 5) Denitrification of brine wastes from groundwater treated for irrigation 6) Decrease in agricultural water demand per hectare (i.e. 10% of decrease by default in the model) (IV) Integrated sustainable management: 7) Control of the extension of irrigated areas 8) Promotion of environmental education 9) Control of the number of groundwater wells (i.e. maximum 500 wells by default in the model) 10) Promotion of small ( 11) Surface water pumping from the Albujón ephemeral stream 12) Control of other point sources of pollution to the lagoon 13) Groundwater pumping and treatment 14) Increase in sea water desalination amount (twice the BAU value by default in the model) A flipbook version of this publication can be found here at the Knowledge Exchange Platform of the COASTAL project.

Esta publicación presenta el proceso de co-diseño de la Hoja de Ruta (BRM) para el desarrollo sostenible del Mar Menor y el Campo de Cartagena, y del modelo de Dinámica de Sistemas para evaluar los impactos del BRM en indicadores clave de sostenibilidad (KPI), bajo diferentes escenarios de cambio socioeconómico, político y climático. Tras presentar el proceso de co-diseño y los impactos sobre los KPI modelizados, se ofrece una breve visión general de los resultados destacados. La Hoja de Ruta (BRM) consiste en los siguientes 4 hitos y las 14 soluciones relacionadas: (I) Ecoturismo rural: 1) Fomento de las actividades de ecoturismo rural. (II) Ecoturismo costero: 2) Fomento de actividades de ecoturismo costero. (III) Agricultura sostenible: 3) La implementación de medidas de retención de nutrientes, suelo y agua. 4) Reducción en el uso de fertilizantes 5) Desnitrificación de los residuos de salmuera tratadas para riego 6) Disminución de la demanda de agrícola de agua por hectárea (IV) Gestión integrada y sostenible: 7) Control de la extensión de áreas agrícolas en regadío 8) Fomento de actividades de educación ambiental 9) Control del número de pozos de agua subterránea para riego 10) Fomento de pequeñas instalaciones (agro)fotovoltaicas ( 11) Bombeo controlado y tratamiento del agua superficial de la rambla del Albujón 12) Control de fuentes puntuales de contaminación de zonas urbanas 13) Extracción controlada y tratamiento de aguas subterráneas 14) Aumento de la cantidad de agua de mar desalinizada Una versión en formato ‘flipbook’ de esta publicación puede encontrarse aquí en la Plataforma de Intercambio de Conocimientos del proyecto COASTAL.&nbsp

Soils play a major role in the global carbon cycle and are crucial to the management of climate change. Changes in plant cover derived from different agricultural practices induce variations in the quality of plant residue inputs and in the soil microbial community structure and activity, which may enhance the storage and protection of organic carbon (OC) and nitrogen (N) within aggregates. The aim of this study was to assess how differences in the chemical composition of plant residues in combination with tillage management practices affect the local microbial community activity and structure, and subsequent soil aggregation and OC and N dynamics in an organic, rainfed almond (Prunus dulcis Mill.) orchard. In the laboratory, three types of plant residue (shoots, roots, and the combination of both) coming from different species belonging to each agricultural practice (reduced tillage, reduced tillage plus green manure, reduced tillage plus organic manure, and no-tillage) were mixed with their respective soils and the CO released was measured over 243 days at 60% WHC and 28 °C. Water-stable aggregates (including microaggregates within macroaggregates), enzymatic activities related to carbon (dehydrogenase and β-glucosidase) and N (urease) cycling, and the microbial biomass and community structure through phospholipid fatty acid analysis, were measured at the end of the incubation period. Our results indicate that the chemical composition of plant residues controls the microbial community response, mediating decomposition and the incorporation of OC and N in stable aggregates. Therefore, the incorporation of labile and N-rich plant residues into the soil by reduced tillage is recommended since mixing roots and shoots from green manure increased the formation of free micro-aggregates and improved OC and N stabilization in our semiarid agroecosystem., This research was supported with funds from the Fundación Séneca of the Murcia Region (projects 08757/PI/08, EMISEMUR 19350/PI/14 and DECADE 20917/PI/18). Parts of this research were performed within the framework of the project IMPASEC AGL2011-25069 funded by the Spanish Ministerio de Economía y Competitividad. María Almagro was supported by the Juan de la Cierva Program (Grant IJCI-2015-23500) and Antonio Ruiz-Navarro by the Fundación General from the Spanish Research Council (CSIC, ConFuturo Progamme).

We investigated the magnitude and drivers of spatial variability in soil and plant δ15 N across the landscape in a topographically complex semiarid ecosystem. We hypothesized that large spatial heterogeneity in water availability, soil fertility and vegetation cover would be positively linked to high local-scale variability in δ15 N. We measured foliar δ15 N in three dominant plant species representing contrasting plant functional types (tree, shrub, grass) and mycorrhizal association types (ectomycorrhizal or arbuscular mycorrhizal). This allowed us to investigate whether δ15 N responds to landscape-scale environmental heterogeneity in a consistent way across species. Leaf δ15 N varied greatly within species across the landscape and was strongly spatially correlated among co-occurring individuals of the three species. Plant δ15 N correlated tightly with soil δ15 N and key measures of soil fertility, water availability and vegetation productivity, including soil nitrogen (N), organic carbon (C), plant-available phosphorus (P), water-holding capacity, topographic moisture indices and normalized difference vegetation index. Multiple regression models accounted for 62-83% of within-species variation in δ15 N across the landscape. The tight spatial coupling and interdependence of the water, N and C cycles in drylands may allow the use of leaf δ15 N as an integrative measure of variations in moisture availability, biogeochemical activity, soil fertility and vegetation productivity (or 'site quality') across the landscape.

Soil degradation continues to be of the major threats for sustainable development and human well-being. Despite the advances in research, there is still a gap between research and effective conservation. To fill this gap, a change is needed in the paradigm of soil conservation research. Therefore, this paper aims to: (i) introduce the concept of Eco-Holistic- Soil Conservation (EHSC) to support the Sustainable Development Goals, (ii) present a framework for the implementation of EHSC, and (iii) show practical examples and recommendations of EHSC. The theory behind the concept of EHSC builds on a critical review of the main causes for success or failure of previous conservation projects and evaluation of latest holistic concepts and visions on conservation of soils and socio-ecosystems. The key principles underlying EHSC are: (1) perception of soils as living-systems, (2) holistic ecosystem approach, (3) central role of soil conservation for climate change mitigation and adaptation, and (4) ethical behavior in soil use. Implementation of EHSC requires a transdisciplinary approach involving a range of actions in three iterative phases: (1) diagnosis of the causes and processes of land degradation and the socio-economic context, (2) integrated assessment of the interactions and synergies between the factors and actors involved and the selection of EHSC actions, and (3) participatory evaluation and monitoring of impacts. Successful conservation requires more research on the resilience and adaptation of soils to climate change, integrated economic valuations of soil conservation, and protection of native peoples right to land in international legislation., This study was supported by the Spanish Ministerio de Economia y Competitividad (CGL2013-48753-R co-funded by European Union FEDER funds) and Fundación Séneca (20917/PI/18)

Este artículo contiene 16 páginas, 6 figuras, 2 tablas., Soil degradation by water is a serious environmental problem worldwide, with specific climatic factors being the major causes. We investigated the relationships between synoptic atmospheric patterns (i.e. weather types, WTs) and runoff, erosion and sediment yield throughout the Mediterranean basin by analyzing a large database of natural rainfall events at 68 research sites in 9 countries. Principal Component Analysis (PCA) was used to identify spatial relationships of the different WTs including three hydro-sedimentary variables: rainfall, runoff, and sediment yield (SY, used to refer to both soil erosion measured at plot scale and sediment yield registered at catchment scale). The results indicated 4 spatial classes of rainfall and runoff: (a) northern sites dependent on North (N) and North West (NW) flows; (b) eastern sites dependent on E and NE flows; (c) southern sites dependent on S and SE flows; and, finally, (d) western sites dependent on W and SW flows. Conversely, three spatial classes are identified for SY characterized by: (a) N and NE flows in northern sites (b) E flows in eastern sites, and (c) Wand SW flows in western sites. Most of the rainfall, runoff and SY occurred during a small number of daily events, and just a few WTs accounted for large percentages of the total. Our results confirm that characterization by WT improves understanding of the general conditions under which runoff and SY occur, and provides useful information for understanding the spatial variability of runoff, and SY throughout the Mediterranean basin. The approach used here could be useful to aid of the design of regional water management and soil conservation measures., This research was supported by projects funded by the MINECOFEDER: CGL2014-52135-C3-3-R, CGL2014-59946-R, CGL2015-65569- R, CGL2015-64284-C2-2-R, and PCIN-2017-061/AEI. When this manuscript was first submitted Estela Nadal-Romero and Damià Vericat received a “Ramón y Cajal” postdoctoral contract (RYC-2013-14371 and RYC‐2010‐06264, Spanish Ministry of Economy and Competitiveness, MEC). Damià Vericat is now a Serra Húnter Fellow at the University of Lleida. María Fernández-Raga received a “José Castillejo” postdoctoral grant (Spanish Ministry of Education, Culture and Sports). Carla Ferreira was supported by a post-doctoral research grant from the Portuguese Science and Technology Foundation (SFRH/ BPD/120093/2016). Mariano Moreno-de las Heras received a Juan de la Cierva postdoctoral contract (IJCI-2015-26463) from the MEC. José Andrés López-Tarazón received a Vicenç Mut postdoctoral fellowship from the Autonomous Balearic Government (CAIB PD/038/2016). José Andrés López-Tarazón and Ramon Batalla also acknowledge the Secretariat for Universities and Research of the Department of the Economy and Knowledge of the Autonomous Government of Catalonia for supporting the Consolidated Research Group 2014 SGR 645 (RIUSFluvial Dynamics Research Group), and the CERCA Programme. This paper has benefited from the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306).

Semiarid Mediterranean agroecosystems need the implementation of sustainable land management (SLM) practices in order to maintain acceptable levels of soil organic matter (SOM). The application of SLM practices helps to maintain soil structure and physical-chemical protection of soil organic carbon (SOC), hence improving soil carbon sequestration and mitigating CO 2 emissions to the atmosphere. In an organic, rain-fed almond ( Prunus dulcis Mill., var. Ferragnes) orchard under reduced tillage (RT), as the habitual management practice during the 14 years immediately preceding the experiment, we studied the effect of two agricultural management practices on soil aggregate distribution and SOC stabilization after four years of implementation. The implemented practices were (1) reduced tillage with a mix of Vicia sativa L. and Avena sativa L. as green manure (RTG) and (2) no-tillage (NT). Four aggregate size classes were differentiated by wet sieving (large and small macroaggregates, microaggregates, and the silt plus clay fraction), and the microaggregates occluded within small macroaggregates (SMm) were isolated. In addition, three organic C fractions were separated within the small macroaggregates and microaggregates, using a density fractionation method: free light fraction (free LF-C), intra-aggregate particulate OM (iPOM-C), and organic C associated with the mineral fraction (mineral-C). The results show that the combination of reduced tillage plus green manure (RTG) was the most-efficient SLM practice for SOC sequestration. The total SOC increased by about 14% in the surface layer (0–5 cm depth) when compared to RT. Furthermore, green manure counteracted the effect of tillage on soil aggregate rupture. The plant residue inputs from green manure and their incorporation into the soil by reduced tillage promoted the formation of new aggregates and activated the subsequent physical-chemical protection of OC. The latter mechanism occurred mainly in the fine iPOM-C occluded within microaggregates and mineral-C occluded within small macroaggregates fractions, which together contributed to an increase of up to 30% in the OC concentration in the bulk soil. No-tillage favored the OC accumulation in the mineral-C within the small macroaggregates and in the fine iPOM-C occluded within microaggregates in the surface layer, and in the mineral-C occluded within the small macroaggregates and microaggregates at 5–15 cm depth, but four years of cessation of tillage were not enough to significantly increase the total OC in the bulk soil.

Changes in plant cover after afforestation induce variations in litter inputs and soil microbial community structure and activity, which may promote the accrual and physical-chemical protection of soil organic carbon (SOC) within soil aggregates. In a long-term experiment (20 years) we have studied the effects, on soil aggregation and SOC stabilization, of two afforestation techniques: a) amended terraces with organic refuse (AT), and b) terraces without organic amendment (T). We used the adjacent shrubland (S) as control. Twenty years after stand establishment, aggregate distribution (including microaggregates within larger aggregates), sensitive and slow organic carbon (OC) fractions, basal respiration in macroaggregates, and microbial community structure were measured. The main changes occurred in the top layer (0-5cm), where: i) both the sensitive and slow OC fractions were increased in AT compared to S and T, ii) the percentage and OC content of microaggregates within macroaggregates (Mm) were higher in AT than in S and T, iii) basal respiration in macroaggregates was also higher in AT, and iv) significant changes in the fungal (rather than bacterial) community structure were observed in the afforested soils (AT and T) - compared to the shrubland soil. These results suggest that the increase in OC pools linked to the changes in microbial activity and fungal community structure, after afforestation, promoted the formation of macroaggregates - which acted as the nucleus for the formation and stabilization of OC-enriched microaggregates. © 2015 Elsevier Ltd., This research was found by the Spanish Research, Development and Innovation Plan I+D+I 2008-2011 (Project AGL2010-20941).

In semiarid climates, soils are often found in pre-desertic states with constrained vegetation, organic matter and ecosystem functionality. These limitations negatively impact soil microbial communities which are important drivers of biogeochemical processes and strongly influence soil quality. The long-term impacts of restoration on the phylogenetic structure and metabolic functionality of soil microbial communities were studied in a representative degraded field area located in southeast-Spain. Restoration was undertaken 25 years ago by the singly application of two doses of organic domestic waste at 65 Mg ha−1 (LD plots) and 195 Mg ha−1 (HD plots). Control soils without amendment were also evaluated. Pyrosequencing of 16S- and 18S-rRNA genes did not reveal significant differences in phylogenetic diversity between restored and control soils. However, principal coordinates analysis of unweighted Unifrac distances showed variation in the structure of bacterial and fungal communities of HD plots. The number of Alpha-proteobacteria sequences was higher in HD plots than in LD and control plots, while Actinobacteria abundance diminished in HD plots. In contrast to Basidiomycota, the number of Ascomycota sequences responded positively to restoration. Changes in microbial phylogenetic structure were related to changes in functional structure established by multivariate analysis of community-level-physiological profiles. Interestingly, despite the absence of phylogenetic diversity, restoration decreased the catabolic diversity in HD plots. This effect is likely due to the aboveground plant influences in restored plots. Overall, in the long-term, soil restoration under semiarid conditions did not increase microbial diversity but influenced microbial community structure and functionality.

Sustainable farming practices can be beneficial or detrimental to crop production in the short-term, which will strongly determine their appeal to farmers. We evaluated the effects of several sustainable practices on soil properties, plant nutrition and ecophysiology and crop yield in a semiarid agroecosystem. A three-year randomised experiment was conducted in a rainfed almond grove where the initial soil management was reduced tillage. Two alternative treatments were evaluated: reduced tillage plus green manure and no-tillage. The following soil and plant parameters were measured once per year: soil organic carbon, total nitrogen and P olsen ; foliar N, P, δ 13 C and δ 15 N and crop yield. We found that soil bulk density increased significantly with no-tillage. Leaf δ 15 N was positively associated with soil fertility, foliar nutrient concentrations and crop yield across treatments. Leaf δ 13 C, N foliar and crop yield were strongly positively associated across treatments in every year of the study. Reduced tillage treatments displayed higher leaf δ 15 N, δ 13 C, N foliar and crop yield than the no-tillage treatment, indicating a sharp decrease in the leaf nitrogen status and intrinsic water use efficiency of almond trees during the transition from reduced tillage to no-tillage. In semiarid agroecosystems where soils are prone to compaction, some tillage is required to maintain optimal crop production in rainfed almonds.

La hidrología de las zonas semiáridas se caracteriza por la escasez e irregularidad de los eventos hidrometeorológicos y por la extrema variabilidad espacio-temporal de sus factores de control. Las cuencas experimentales de la Sierra del Picarcho (Cieza, Murcia) se establecieron en 1997 para estudiar los factores que controlan la generación de escorrentía en distintas escalas de trabajo, analizar la variabilidad de estos factores y desarrollar, y validar, modelos hidrológicos de simulación adaptados a estos ambientes. En el artículo se presentan los datos de escorrentía superficial obtenidos durante los tres primeros años de funcionamiento y se discute los factores de control a escala de parcela y de cuenca. También se estudia la evolución temporal de la humedad del suelo en la cuenca y se identifican qué factores la regulan.

We investigated the magnitude and drivers of spatial variability in soil and plant δ

The results of an experiment to evaluate the effect of rainfall characteristics on organic carbon (OC) losses and on the type of particles mobilised by erosion under natural rainfall and under different land uses (non-disturbed forested area, and a non-irrigated olive cropland) at plot scale are presented. Labile (particulate organic carbon, POC) and stable (mineral associated organic carbon, MOC) carbon pools were measured in soil and sediments. Based on the product of total rainfall and I30 (mm mmh−1), as a measure of rainfall erosivity, events were divided into three classes (from low to high erosivity). A positive correlation between P*I30 and OC concentration (r = 0.54, p

Most dryland ecosystems show high landscape heterogeneity that can influence soil fertility, although the underlying processes are still poorly understood. Furthermore, our understanding of the same could be affected by the scale dependency of the landscape representation. Here, we study the relationships between soil and landscape attributes at different spatial resolutions in a semiarid area, to better understand which landscape processes control soil fertility and whether such control is affected by the resolution of landscape representation. A stratified sampling plan based on topography, vegetation type and lithology was carried out in a semiarid catchment of south-east Spain to select the soil sampling sites. Furthermore, the landscape attributes were resampled at five different resolutions (5, 10, 20, 40 and 80 m) from digital elevation model and remote sensing data. Principal Component Analyses (PCA) for soil and landscape attributes were performed to ascertain the main trends of variation of each set. Then, correlations between the soil and landscape principal component scores at each resolution were calculated to determine the relationships between the two sets of variables. The first component of soil PCA (S-PC1) was related with a number of properties linked to soil fertility: soil organic carbon, nutrient availability, cation exchange capacity, pH and water-holding capacity. The S-PC1 was correlated positively with the first component of landscape PCA (L-PC1), which represents areas of dense vegetation cover associated with topographic convergence and/or low solar radiation. Besides, S-PC1 was also correlated negatively with L-PC2, which represents areas with intense channel formation on easily erodible lithologies and scarce vegetation cover. As the resolution of landscape representation decreased, the explained variance increased faster in L-PC2 than in L-PC1, showing that the representation of each underlying landscape process was more evident at a particular resolution. The relationship between soil fertility and landscape also seemed to change with spatial resolution, as S-PC1 was correlated best with L-PC1 at finer resolutions while the correlation with L-PC2 increased at coarser resolutions. The relationship of S-PC1 with L-PC1 and L-PC2 suggests the presence of a soil fertility gradient mainly ‘driven’ by water availability derived from local topographic conditions against gully erosion processes arising from geomorphological features. Each landscape process ‘controlling’ soil fertility is better represented at different resolutions: conditions that improve water availability were more evident at finer resolutions (5–10 m), while erosion was more evident at medium-coarse resolutions (20–40 m).

Total belowground C allocation (TBCA) accounts for a large fraction of gross primary production, it may overtake aboveground net primary production, and contributes to the primary source of detrital C in the mineral soil. Here, we measure soil respiration, water erosion, litterfall and estimate annual changes in C stored in mineral soil, litter and roots, in three representative land uses in a Mediterranean ecosystem (late-successional forest, abandoned agricultural field, rain-fed olive grove), and use two C balance approaches (steady-state and non-steady-state) to estimate TBCA. Both TBCA approaches are compared to assess how different C fluxes (outputs and inputs) affect our estimates of TBCA within each land use. In addition, annual net primary productivity is determined and C allocation patterns are examined for each land use. We hypothesized that changes in C stored in mineral soil, litter and roots will be slight compared to soil respiration, but will still have a significant effect on the estimates of TBCA. Annual net primary productivity was 648 ± 31.5, 541 ± 42.3 and 324 ± 22.3 g C m −2 yr −1 for forest, abandoned agricultural field and olive grove, respectively. Across land uses, more than 60% of the C was allocated belowground. Soil respiration ( F S ) was the largest component in the TBCA approaches across all land uses. Annual C losses through water erosion were negligible compared to F S (less than 1%) and had little effect on the estimates of TBCA. Annual changes in C stored in the soil, litter layer and roots were low compared to F S (16, 24 and 10% for forest, abandoned agricultural field and olive grove, respectively), but had a significant effect on the estimates of TBCA. In our sites, an assumption that Δ[ C S + C R + C L ]/Δ t = 0 will underestimate TBCA, particularly in the abandoned agricultural field, where soil C storage may be increasing more rapidly. Therefore, the steady-state model is unsuited to these Mediterranean ecosystems and the full model is recommended.

Reforestation with Pinus halepensis has been the most frequently used method for restoring supposedly degraded lands in Mediterranean semiarid areas, a key objective of which is to improve soil conditions to trigger succession. In this paper we study the effect of a 30 year-old reforestation on lands formerly dedicated to two different uses: shrubland and barley fields. The study area is located in SE Spain in a semiarid area with an annual rainfall of 298 mm. We hypothesize that the previous land use will influence present day soil characteristics. In addition, reforestations have led to the formation of microenvironments associated to: (i) tree development, which generates a radial gradient of influence; (ii) disturbance by mechanical works with resulting microenvironments such as escarpments, showing a worse initial state and, therefore, slower dynamics. Ten plots were set up on former shrubland and ten on a former barley field. Each plot represented a set of related microenvironments that followed a gradient of tree influence/mechanical disturbance. The microenvironments on former shrubland were: under escarpment (ES), plantation line adjacent to P. halepensis stem (PL), beneath P. halepensis crown (BC), the upper bank where part of the material of the terrace was dumped (UB) and original unaltered hillslope taken as pseudocontrol of the original soil (PC). In the former barley field, only PL, BC and PC microenvironments were present as no terracing was carried out. Pine growth created a strong gradient of litter input in the sequence PL > BC > PC which, however, had no significant effect on soil organic carbon (SOC) or other soil variables (except light changes in extractable K and pH). The incorporation of organic matter into the soil was probably delayed by the quality of recalcitrant pine litter and the unfavorable semiarid climate. In addition, disturbance created by reforestation works seems to have been buffered by redistribution of fine particles through short-range erosion and sedimentation. In the external part of the terrace, the values of SOC and extractable Na were higher, accompanied by increased electrical conductivity and decreased pH. The most striking differences found were related to former land use. SOC was three times higher in former shrubland than in former barley field. Likewise, available P was higher in the former barley field and extractable Na was higher in the former shrubland, both apparently related to the pre-reforestation state. The results indicate that soil dynamics thirty years after the reforestation has hardly erased the differences attributable to former land use. Soil dynamics induced by the input of organic matter from trees is slower that expected when the reforestation was planned. We conclude that any future application of reforestation should take into account the slow soil dynamics observed in this study in order to be more effective.

An experiment to evaluate the impact of water erosion and cultivation on the soil carbon dynamic and carbon stock in a semiarid area of South-East Spain was carried out. The study was performed under three different land use scenarios: (1) forest; (2) abandoned agricultural field; and (3) non-irrigated olive grove. Experimental erosion plots (in olive grove and forest) and sediment traps (in the abandoned area) were used to determine the carbon pools associated with sediments and runoff after each event occurring between September 2005 and November 2006. Change in land use from forest to cultivated enhanced the risk of erosion (total soil loss in olive cropland seven-fold higher than in the forest area) and reduced the soil carbon stock (in the top 5 cm) by about 50%. Mineral-associated organic carbon (MOC) represented the main C pool in the three study areas although its contribution to soil organic carbon (SOC) was significantly higher in the disturbed areas (78.91 ± 1.81% and 77.29 ± 1.21% for abandoned and olive area, respectively) than in the forest area (66.05 ± 3.11%). In both, the olive and abandoned soils, the reduction in particulate organic carbon (POC) was proportionally greater than the decline in MOC. The higher degree of sediment production in the olive cropland had an important consequence in terms of the carbon losses induced by erosion compared to the abandoned and forest plots. Thus, the total OC lost by erosion in the sediments was around three times higher in the cultivated (5.12 g C m−2) than the forest plot (1.77 g C m−2). The abandoned area displayed similar OC losses as a result of erosion as the forest plot (in the measurement period: 2.07 g C m−2, 0.63 g C m−2 and 0.65 g C m−2 for olive, forest and abandoned area, respectively). MOC represented the highest percentage of contribution to total sediment OC for all the events analysed and in all uses being, in general these values higher in Olive (74–90%) than in the other two areas (55–80%). The organic carbon lost was basically linked to the solid phase in the three land uses, although the contribution of DOC to total carbon loss by erosion varied widely with each event. Data from this study show that the more labile OC fraction (POC) lost in soil in the cultivated area was mainly due to the effect of cultivation (low overall biomass production and residue return together with high C mineralization) rather than to water erosion, given that the major part of the OC lost in sediments was in the form of MOC., This research was supported with founds from the Projects: ERHIBAC (GGL2004-03179 BTE) Spanish CICYT, the Project 3027/PI/05, Murcia Regional Government (SENECA Foundation) and RESEL project founded by the Spanish Ministerio de Medio Ambiente.

Soil erosion plots of different types and sizes are widely used to investigate the geomorphological processes related to soil erosion. This field method has provided a variety of results, depending on the characteristics of the plots, on their suitability to reflect the ecosystem's characteristics and on the objectives of each particular research. The coupling of real soil loss at patch and slope scale within a landscape and the values obtained by field plots depend, among other things, on how good the methodology performs over a set of ecosystem properties, such as those related with temporal and spatial scale issues, disturbance and representation of natural conditions, and the ability to account for the complexity of ecosystem interactions. Here, we present a review of (i) the advantages and limitations of the use of field plots to measure soil erosion; and (ii) the potential sources of variation in the results obtained due to a lack of harmony between methodological conditions and the processes operating in the environment at different scales. As regards the spatial and temporal scale of measurements, topics such as the exhaustion of available material within closed plots in long term measurements, the different erosion processes operating (and measured) at different spatial scales and the problems and alternatives of extrapolation of the results from larger to smaller scales, are the main causes of variation between measurements. The disturbance and inadequate representation of natural conditions, such as the heterogeneity, continuity and connectivity of factors and processes, are also sources of variation in the results of specific measurements. In short, the key factor is the difficulty to encapsulate the complexity of system interactions and to represent these interactions by means of field plots. The complexity concept is translated in the connectivity of water and sediment fluxes in the landscape and the interaction between processes and patterns of vegetation and surface components operating across scales., This research was financially supported by the Commission of the European Union through research contracts ERMES I (EV5V-CT91-0023), ERMES II (ENV4-CT95-0181), EUROSEM (STEP programme contract no 0053) and MWISED (ENV4-CT97-0687); the Spanish Ministries of Environment and of Science and Technology (CICYT) through contract RESEL (Contribución Española al Desarrollo del Convenio Mundial para Prevenir la Desertificación: I. — Red de Cuencas y Parcelas Experimentales de seguimiento y Evaluación de la Erosión y Desertificación), PROHIDRADE (AMB95-0986-C02-01), EPROHIDRO (HID98-1056-C01-01), SENSI (AMB99-1246), PROHISEM (REN01-2268-CO2-01/HID).

A reduction in plant cover can lead to an increase in the erosionprocesses that diminish soil quality. Any rise in temperature resulting frompredicted climate changes may aggravate this effect, particularly in semiaridMediterranean areas. Bearing this in mind, the capacity of a soil to preserveorganic matter becomes very important if the soil is to maintain its physicaland chemical properties. Soil organic carbon and nitrogen changes wereevaluatedin a non-disturbed (with natural vegetation) and a disturbed (all vegetationmanually clipped to ground level) pine system. Nine years after vegetationremoval significant differences (p < 0.01) were found in the soil organiccarbon content between plots (top 20 cm), but not in totalnitrogen. In the disturbed plot 0.0232 Mg ha−1y−1 of soil organic carbon were lost through erosionand4.30 Mg ha−1 y−1 throughmineralization. In the first 48 months after vegetation removal the soilorganiccarbon content fell from 40.3 to 28.0 g kg−1. Inthe last 60 months of the experiment the amount of organic carbon in the soilfell from 28.0 to 27.7 g kg−1. This result wasmainly attributable to the intense oxidization, which took place during thefirst 60 months, of organic matter linked to the coarse soil mineral fraction.Up to the 72nd month the losses by erosion were a total of 532.7g, which rose to 1284.4 g by the end of theexperiment(108 months). The effect of vegetation removal in a Mediterranean semiarid arealeads to a rapid decline in the amount of organic carbon stored in the soil.Such perturbation is irreversible if left to nature.

Division S-6 — Notes, Organic refuse application to soil may improve soil structure and thus soil quality and productivity. Two semiarid, structureless soils with, F. Caravaca acknowledges a grant from Caja de Ahorros del Mediterráneo (CAM).

Sediment samples were collected during four years from two plots, one covered by natural vegetation and the other, a “replica” of the same plot, from which the vegetation was removed manually (disturbed plot), in order to evaluate the effects of vegetal cover on sediment particle size distribution. Particle-size was measured using a Coulter LS130 laser diffraction device. The effective size distribution of the sediment was compared with equivalent measurements of the same samples after chemical and mechanical dispersion (ultimate size distribution) to investigate the detachment and transport mechanisms involved in sediment mobilisation. The ratio between the ultimate particle size composition of the transported sediment and that of the parent soil provided a measure of the particle-size selectivity of the transported sediment. The median effective particle was coarser than the median ultimate particle for almost all the events recorded in both plots, confirming that much of the sediment in the runoff includes a substantial proportion of aggregates. Moreover, the texture of the sediment was finer than that of the matrix soil, with a depletion of clay and sand in exchange for an enrichment in silt, indicating the existence of transport selectivity in both plots. The effect of vegetal cover on the size distribution of the sediment was, particularly evident after high intensity rainfall events. An I30 of 40 mm h−1 was found to be the threshold value for changes to be produced in the sediment texture of the disturbed plot, with aggregates being broken down and 10%–20% more sand particles being observed at this value than after events of lower intensity. No differences were found in the natural plot after rainfall of varying intensities. The vegetal cover in the natural plot reduced the energy available for erosion from the rainfall by 50%, and, the energy from the runoff by 75%, hindering the break down of aggregates and the transport of dense particles. Moreover, the presence of vegetation meant the raindrop was the predominant contributor to soil loss in contrast to the disturbed plot where both raindrop and runoff contributed to the erosion.

Soil erosion, which is a widespread problem in semiarid areas, may lead to a decline in soil productivity since the finest and most fertile soil particles are those which are generally removed. Our objective was to determine the distribution of soil organic matter, phosphorus, potassium and cation exchange capacity within the fine fractions ( The data confirm that the proportion of soil organic matter depends on the stabilizing capacity of the different size fractions, both the clay and fine silt size fractions playing an important role in semiarid soils. To the detriment of the soil's organic matter content these fractions are easily eroded in soils under arid and semiarid conditions, which may render them unsuitable for agricultural purposes.

A deeper knowledge of the hydrological response of semi-arid Mediterranean watersheds would be useful in the prediction of runoff production for assessing flood risks and planning flood mitigation works. This study was conducted to identify the runoff generation mechanisms and their controlling factors at the hillslope scale in a Mediterranean semi-arid watershed. Four zero-order microcatchments were selected to measure rainfall and runoff for a three-year period. Two groups of soil were differentiated with respect to the hydrological response. The fine textured, poorly permeable soils of low organic carbon content had a greater runoff coefficient (9%) and lower runoff threshold (3·6 mm) than more permeable, coarser textured soils of medium organic carbon content ( 5 mm h−1); and (ii) a saturation-excess overland flow in the less degraded areas with a high organic carbon content (>2%), high infiltrability (>8 mm h−1) and covered by a dense plant cover (>50%). © 1998 John Wiley & Sons, Ltd.

A field experiment was carried out to evaluate the growth response of Pinus halepensis seedlings inoculated with Pisolithus arhizus and planted in a terraced rangeland amended with urban solid refuse. The application of the organic amendment mediated a significant increase in soil fertility and soil water content. Twenty seven months after planting seedling survival rates did not differ significantly among treatments and were above 95% in all cases. Growth of P. halepensis was significantly (p

Erosion mapping is a useful tool for soil conservation planning. The possible correlation between soil type or lithology with soil erodibility has been tested with the aim of facilitating the accomplishment of erosion maps from soil or lithology maps. Soil erodibility (K factor of the universal soil loss equation [USLE]) was determined from 340 samples taken from 4 soil types, on which approximately 95% of agriculture in the semiarid Mediterranean area is located. Calcaric regosols (K = 0.47) showed the highest erodibility and are significantly different from the other soil types. It was also possible to differentiate between calcic xerosols (K = 0.41) and petrocalcic xerosols (K = 0.37). No significant differences were established between the other soil types. The statistical analysis of the soil samples, grouped according to lithology, showed a better discrimination than is evident from those grouped as a function of soil type. It was possible to establish significant differences among all lithologies w...

Soil structure has been destroyed over large areas of arid and semi-arid regions by soil degradation processes. This study was conducted to investigate the effects of two organic amendments, urban refuse and peat, on the improvement of soil structure and to analyse correlations between organic carbon content, fungal and bacteria populations and aggregate stability. Two series of five plots were established in the southeast of Spain, in typical Mediterranean semi-arid to arid conditions. To one series different initial doses of urban refuse (0, 6.5, 13, 19.5 and 26 kg m−2) were added, whereas to the other series different doses of peat (0, 10, 20, 30 and 40 kg m−2) were added. The average percentage of stable aggregates showed a significant increase (31.6, 41.1, 53.7, 63.2%) with increased levels of urban refuse with respect to the control. On the other hand, peat was not effective in improving stable aggregates. The beneficial effect which appeared with urban refuse remained in the soil two years after application, probably due to the growth of natural vegetal cover in the treated plots. A marked increase in fungal and bacterial populations and a decrease in extractable organic carbon was observed in the plots into which urban refuse was incorporated. This, together with the high correlation coefficients between the percentage of stable aggregates and the microbial population, suggested that the combined action of polysaccharides from the urban refuse and the increase in microbiological activity was responsible for the initial formation of soil aggregates.

The constituents of urban refuse may have potential chemical benifits in reclaiming degraded soils and improving plant growth, but this may be offset by chemical problems such as increased soil salinity and the accumulation of heavy metals. A series of experiments was conducted in the Fortuna Basin in semi-arid south-east Spain on a Xeric Torriorthent to investigate changes in soil properties with urban refuse amendments varying from 6.5 to 26 kg·m−2. Soil chemical properties were monitored during three years after the application of solid, largely organic, urban refuse. Changes in the contents of potassium, phosphorus, nitrogen, organic carbon, exchangeable sodium, electrical conductivity, and the sodium, chlorine and sulphates in the saturation extract, as well as a number of heavy metals are reported. Salts are quickly leached out, whereas essential plant nutrients are retained. There is a clear medium-term benefit to soil fertility with the use of urban refuse. Potential off-site impacts of diluted toxic contaminants are discussed

An experiment was carried out to evaluate the growth of mycorrhizal Pinus halepensis seedlings planted in a semiarid soil amended with urban refuse in southeast Spain. Three fungal species were used: Pisolithus tinctorius, Rhizopogon roseolus, and Suillus collinitus. After 8 months, inoculated seedlings grown under controlled conditions did not differ significantly from controls with regard to plant height and nutrient assimilation. Other features such as root development and stem dry weight showed that the plants grew better in the absence of mycorrhizal inoculation. The mycorrhizal seedlings and the controls were planted in three experimental plots treated with urban refuse (0, 6, and 12 Kg m-2). After 1 year of growth under field conditions the results showed that the type of fungus inoculated significantly influenced P. halepensis development. This effect varied with the dose of urban refuse. Plant growth was encouraged by the application of refuse but only at the lowest dose. Under these conditions P. tinctorius was the most effective fungus and R. roseolus yielded poorer plant development. The highest application of urban refuse led to notably worse results and a significant decrease in seedling growth compared to controls. In the control plot (without refuse) S. collinitus was the most effective fungus in plant growth improvement. The smallest application of urban refuse had a positive effect on the assimilation of N, P, and K in seedlings inoculated with P. tinctorius and S. collinitus.

An experiment was conducted on a vertic Xerochrept, salinized by saline water irrigation, to investigate the effect of municipal solid waste (MSW) application and irrigation with normal (0.19 S m‐1) and saline (0.42 S m‐1) water, on the physical and chemical properties of the soil. The experiment was carried out during one tomato crop (6 months). Organic carbon, cation exchange capacity, exchangeable sodium, aggregate stability, infiltration rate, water holding capacity and plant growth were monitored. A high risk of secondary salinization was observed when the soil was irrigated with saline water. The physical properties of the soil, such as structural stability, infiltration rate and water holding capacity, were considerably improved by MSW application. This improvement could help in the reclamation of salinized soils due to the increased washing capacity.

Plants of Hedysarum confertum Desf. and Hedysarum spinosissimum L. inoculated with five Glomus species (G. epigaeum, G. etunicatum, G. fasciculatum, G. macrocarpum and G. mosseae) were grown in a marl soil for 14 weeks. Both legumes became colonized with VAM fungi, although colonization percentages were lower than those observed in nature. For H. confertum, G. epigaeum, G. fasciculatum, and G. macrocarpum increased growth significantly when compared to controls. For H. spinosissimum the most efficient fungi for growth improvement were G. macrocarpum, G. mosseae, and G. etunicatum. A clear growth‐depressing effect of G. fasciculatum on H. spinosissimum was observed. Root/shoot ratio increases with inoculation in H. confertum but can decrease in H. spinosissimum. P uptake was not markedly improved by mycorrhizal inoculation. The greatest amounts of P occurred in both legumes colonized by G. macrocarpum.

Catchments behave as sources or sinks of soil carbon, depending on the magnitude and type of land use changes within their drainage area, on the intensity of erosion processes and on the fate of eroded sediments. The effect of changing land uses on the organic soil carbon (C) stock and the soil C transported by water erosion and buried in depositional wedges behind check-dams was estimated in a Mediterranean catchment in SE Spain. Changes in land use patterns in the catchment between 1956 and 1997 (57% decrease in areas dedicated to agriculture and 1.5-fold increase of the total forest cover) induced an accumulation rate of total organic carbon (TOC) in the soil of 10.73 g m−2 year−1. Mineral-associated organic carbon (MOC) was the main soil carbon pool (70%). Particulate organic carbon (POC) was highest in the shrubland soils (33%). The average sediments/soil enrichment ratio at the subcatchment scale (8–125 ha) was 0.59 ± 0.43 g kg−1. Eroded soil C accounted for between 2% and 78% of the soil C stock in the first 5 cm of the soil in the subcatchments. The C erosion rate varied between 0.008 and 0.2 t ha−1 year−1. Observed changes in land use (decrease in agricultural areas) reduced soil C erosion, although sediments from non-agricultural sources are richer in organic C. At catchment scale from the 4% of the soil C stock mobilized by water erosion, 77% is buried in the sediment wedges behind check-dams. Soil C replacement due to increased vegetation cover between 1974 and 1997 represented a 36% of the original soil organic C stock. All together represent an erosion-induced sink of soil organic C of 40% compared to the original levels of 23 years before. This has caused the catchment to behave as a soil C sink within the soil erosion subsystem since the 1950s. The meaning of this erosion-induced C sink in a wider C balance which takes into account soil respiration remains uncertain., This work has been financially supported by the projects CICYT CGL2004-03179/BTE (Ministry of Science and Technology of Spain), SENECA 03027/PI/05 (Region of Murcia Government) and ERCO (CGL2007-62590/BTE) from the Ministry of Science and Innovation of Spain. The Dirección General del Medio Natural de la Región de Murcia (Directorate of Environment) and the Mancomunidad de Canales del Taibilla (Community of channels of the Taibilla river) are acknowledged for the interest shown in this research. The first author was financially supported by a Ramón y Cajal contract. Joris de Vente was supported by a contract in the integrated project DESIRE of the EU FP6 037046 (GOCE). Thanks are extended to Adolfo Carrasco Sánchez and Raquel Ros Alcaraz who helped in the laboratory and in the analysis of the data.

Restoration of degraded lands could be a way to reverse soil degradation and desertification in semiarid areas and mitigate greenhouse gases (GHG). Our objective was to evaluate the long-term effects of a single addition of organic refuse on soil physical properties and measure its carbon sequestration potential. In 1988, a set of five plots (87 m2 each) was established in an open desert-like scrubland (2–4% cover) in Murcia, Spain, to which urban solid refuse (USR) was added in a single treatment at different rates. Soil properties were monitored over a 5-yr period. Sixteen years after the addition, three of the plots were monitored again (P0: control, P1: 13 kg m–2, P2: 26 kg m–2 of USR added) to assess the lasting effect of the organic addition on the soil organic carbon (SOC) pools and on the physical characteristics of the soil. The SOC content was higher in P2 (16.4 g kg–1) and in P1 (11.8 g kg–1) than in P0 (7.9 g kg–1). Likewise, aerial biomass increased from 0.18 kg m–2 in P0 up to 0.27 kg m–2 in P1 and 0.46 kg m–2 in P2. This represents a total C sequestration of 9.5 Mg ha–1 in P2 and 3.4 Mg ha–1 in P1, most of the sequestered C remaining in the recalcitrant soil pool. Additionally, higher saturated hydraulic conductivity, aggregate stability, and available water content values and lower bulk density values were measured in the restored plots. Clearly, a single addition of organic refuse to the degraded soils to increase the potential for C sequestration was effective.

Published online 25 May 2006, An understanding of the sources of variation in the use of erosion plots and of their feasibility to meet the objectives of each specific research project is key to improving future field designs, selecting data for modelling purposes and furthering knowledge of soil erosion processes. Our own field experiences from ongoing research on soil erosion processes since 1989, have allowed us to detect several methodological problems that cause measurement variability. Here several examples are presented concerning: (i) differences in long-term soil erosion data between open and closed plots; (ii) differences in soil loss derived from replica soil erosion plots; and (iii) differences in soil loss data derived from plots at a range of spatial scales. Closed plots are not the most suitable method for long-term monitoring of soil erosion rates due to the risk of exhaustion of available material within the plot. The difference in time after which exhaustion occurs depends on the surface soil characteristics, the climatological conditions and the size of the plots. We detected four and seven years as time to exhaustion. Different results are frequently obtained between pairs of replica plots. Differences up to a factor of nine have been detected in total soil loss between replica plots due to different spatial patterns of surface components. Different constraints appear depending on the spatial scale of measurement of soil loss. We obtained lower runoff percentages at coarser scales; however, larger sediment concentrations are observed at coarser scales (1·32 g l-1, catchment; 0·30 g l-1, 30 m2; 0·17 g l-1, 1 m2 scales). The smaller the plot, the larger the hydrological disconnection within the system, the lower the energy flows due to short distances and the quicker the response to runoff due to an artificial decrease of concentration times for continuous flow., Funded by: Commission of the European Union; Grant Number: EV5V-CT91-0023, ENV4-CT95-0181, STEP program 0053, ENV4-CT97-0687 Spanish Ministries of Environment, and of Science and Technology; Grant Number: AMB95-0986-C02-01, HID98-1056-C01-01, AMB99-1246, REN01-2268-CO2-01/HID

The Mar Menor is a coastal lagoon increasingly threatened by urban and agricultural pressures. The main watercourse draining into the lagoon is the Rambla del Albujón. A fortnightly campaign carried out over one annual cycle enabled us to characterize the treated urban sewage effluents and agricultural sources which contribute to the nutrient fluxes in the watercourse. Multivariate analysis provided information for establishing chemical signatures and for assessing the relative influence of the various sources on the water quality at the outlet. Mass balances were used to examine net gains and losses, and cross-correlations with rainfall to analyze climatic influence and control factors in the trends of the nutrient flux. The rainfall pattern was significantly cross-correlated with nitrate and phosphorus fluxes from agricultural sources, while fluctuations in the resident population explained the phosphorus flux trend in urban sources. 50% of dissolved inorganic nitrogen was from agricultural sources, while 70% of total phosphate and 91% of total organic carbon were from urban point sources. The net amounts of all the nutrients fell as a result of plant uptake and/or denitrification in the channel. The control of urban point sources (phosphorus-enriched) is suggested as a promptly action for improving the health of the coastal lagoon., This project was funded by the European Commission, EESD Specific Program (EVK-CT-2002-00112; tempQsim project) and by the Autonomous Community of Murcia (Spain), through the Agriculture and Water Council (RP-AG 02018/CV/01).

A 5-year study of the reforestation of a semiarid Mediterranean ecosystem with Pinus halepensis is presented. Reforestation of Mediterranean semiarid ecosystems is challenging as a result of harsh environmental conditions and historical human exploitation leading to degradation. New techniques have to be developed in order to increase survivorship and growth that integrates nursery and field treatments. A total of 60 treatments resulting from 12 site × 5 plant preparation techniques were tested. Plant preparation consists of mycorrhizing in nursery, extra fertilizing in nursery, planting in containers in the nursery, planting in the field with a polypropylene tube, and control plants (bred in plastic bags). Soil preparation consists of hole, subsoiling without amendment, subsoiling with composted organic amendment added in the surface or in the furrow of plantation and subsoiling with fresh organic amendment added in the surface or in the furrow of plantation. Each one of these treatments was tested with a hydrophilic acrylic copolymer and without it. Survivorship was very high (0.91) given the prevailing environmental conditions. Subsoiling promoted higher survival than holes, and plants bred in containers had lower levels of survivorship than control ones. Protecting seedlings with polypropylene tubes had no effect on survivorship. The most effective treatment for promoting growth was organic amendment, the effect of which increased until the fourth year. Protection with tubes was very effective in increasing height, although only in the short-term. Subsoiling also promoted faster growth than holes, although the effect was less noticeable after 3 years and was, in any case, less effective than organic amendment. Other treatments promoting faster growth were the use of fresh organic waste as opposed to composted waste and its incorporation in the plantation furrow rather than as a layer on the surface. The addition of hydrophilic acrylic copolymer reduced growth during the first months of the reforestation. The fertilization of plants in the nursery and inoculation with spores of mycorhyzal fungi did not improve seedling growth. Plants bred in containers performed worse than control plants bred in individual plastic bags. The findings suggests the importance of nutrient supply in semiarid environments, an aspect that has been previously neglected in favor of water supply. Organic amendments reinforce both and can be recommended as long as adequate environmental controls are in place., This work was supported by the Spanish National Plan of RþD (Project AGF99- 1132).

From the 1980s onward studies on interrill soil erosion were intensified in SE Spain. The main achievements of the research carried out in the field areas of Alicante and Murcia concern: first, (1) the estimation of erosion rates directly in the field under a wide range of methodologies, different scales and different environmental conditions; (2) estimations based on existing models, such as the USLE, carried out for different subcatchments of the Segura and Júcar catchments; and (3) other parametric and physical event-based models have also been calibrated and validated. Second, the progress of the knowledge in understanding erosion mechanisms. New and reviewed concepts regarding mainly hydrological behaviour and sediment movement and transport at patch, slope and catchment scale have improved our understanding of soil-erosion processes in Mediterranean-type ecosystems. These concepts focus on: (1) the definition of runoff generation models more appropriate to Mediterranean conditions; (2) the definition of thresholds for runoff generation; (3) the definition of models of soil water redistribution within soils and at landscape level; (4) the establishment of conditions and controls for sediment detachment and movement; and (5) the characterization of the change in the controlling factors of soil erosion and degradation under different environmental characteristics (climatic or human-induced). The insights into soil-erosion processes obtained and the renewed hydrological and geomorphological concepts achieved can be very valuable for the design of new strategies of erosion management and ecosystems restoration., Funded by: Commission of the European Union; Grant Number: ERMES I (EV5V-CT91-0023), ERMES II (ENV4-CT95-0181), EUROSEM (STEP 0053), MWISED (ENV4-CT97-0687) Spanish Ministry of Environment Spanish Ministry of Science and Technology; Grant Number: RESEL, PROHIDRADE (AMB95-0986-C02-01), EPROHIDRO (HID98-1056-C01-01), SENSI (AMB99-1246), PROHISEM (REN01-2268-CO2-01/HID)

8 pages, 1 figure, 2 tables., Organo-mineral particle-size fractions play a major role in soil structure. However, our knowledge of these size fractions must increase if we are to optimise the physical regeneration of degraded soils in semiarid areas. Twenty soils (sieved, F. Caravaca acknowledges a grant from Caja de Ahorros del Mediterráneo (CAM).

Our aim was to evaluate the long-term influences of urban organic amendments on the enzymes involved in the carbon cycle under semi-arid conditions, including changes in the biomass and structure of the microbial community. A soil was restored 24 years ago with an organic amendment based on domestic organic waste. Organic amendment was applied to soil in order to increase the content of total organic carbon (TOC) by 0.5% and 1.5% with respect to the original TOC content. Enzyme isoform composition was studied by using zymographic techniques based on protein extraction, separation by gel electrophoresis and further enzyme-specific, in-gel staining. Total cellulose and β-glucosidase activities, microbial biomass estimated by phospholipid-fatty acid analysis and the number of isoforms of each enzyme showed increases related to the initial amount of organic amendment and the consequent development of vegetation. The information obtained by enzyme activity assays may be improved by the use of zymographic techniques, which allow the investigation of the variety of isoforms of each enzyme. This information could improve the understanding of the relationship between the microbial community and carbon cycling in restored areas.

Erosion and sediment characteristics were measured using simulated rainfall on two cultivated soils of contrasting lithology (Quaternary calcareous colluvium and Tertiary marls) in a semiarid Mediterranean area of SE Spain. Two rainfall intensities, high (56.0±2.4 mm h−1) and medium (31.4±1.4 mm h−1), were used in order to know the mechanisms involved in each selected condition. For each simulated event, runoff and sediment were sampled at 1-min intervals on a 1-m wide by 2-m long erosion plot. The erosion rate was calculated as the total amount of soil lost divided by the time period of the test. The duration of the test was that needed to reach steady state runoff, an average time of 24.5 min for Quaternary calcareous colluvium and 17.7 min for Tertiary marls. The size distribution of the transported sediment in the field (effective size distribution) was compared with equivalent measurements of the same samples after chemical and mechanical dispersion (ultimate size distribution) to investigate the detachment and transport mechanisms involved in sediment mobilisation. The results showed that the soil type determined the hydrological response, regardless of the rainfall intensity. The erosional response was, however, determined by the rainfall and soil surface characteristics. In Quaternary calcareous colluvial soils, the predominant erosion process depended on the rainfall intensity, with a prevailing detachment-limited condition in high-intensity events and prevailing transport-limited conditions in those events of medium intensity. These differences in the main erosion processes were reflected in the size of the transported material and in the change in sediment size within the storm. Thus, a time-dependent size distribution of the eroded material (decreasing coarse fractions and increasing fine fractions with runoff time) was observed for high-intensity events. In medium-intensity events, on the other hand, the time-independent size distribution of the eroded material indicated transport-limited erosion. Due to the rapid surface crusting on the Tertiary marl soil, no differences in the main erosion processes or in the sediment size distribution occurred for the different rainfall intensities tested. The erosion of marl soils was determined mainly by the limited quantity of available sediment. The effective size of material was a more sensitive parameter than the ultimate size of the sediment to study the way in which the sediment was transported., This research was supported by the EC Environment and Climate Research Programme (Contract no. ENV4-CT97-0687).

A better knowledge of soil erosion by water is essential for planning effective soil and water conservation practices in semi-arid Mediterranean environments. The special climatic and hydrological characteristics of these areas, however, make accurate soil loss predictions difficult, particularly in the absence of minimal data. Two zero-order experimental microcatchments (328-759 m2), representative of an extensive semi-arid watershed with a high potential erosion risk in the south-east of Spain, were selected and monitored for 3 years (1991-93) in order to provide information on the hydrological and erosional response. A pluviogram and hydrograph recorded data at 1-min intervals during each storm, after which the soil loss was collected and the particle size of the sediment was analysed. Runoff coefficients of about 9% and soil losses of between 84·83 and 298·9 g m-2 year-1 were observed in the area. Rapid response times (geometric mean values lower than 2 h) and low runoff thresholds (mean values between 3·5 to 5·9 mm) were the norm in the experimental areas. A rain intensity of over 15 mm h-1 was considered as erosive rainfall in these areas because of the total soil loss and the transport capacity of the overland flow. Differences in pore-size distribution explained the different hydrological responses observed between areas. The erosional response was more complex and basically seemed to be determined by soil aggregate stability and topographical properties. A greater proportion of finer particles in the eroded material than in the soil matrix indicated selective erosion and the transport of finer material., Funded by: EC Environment and Climate Research Programme; Grant Number: ENV4-CT97-0687 Spanish CICYT; Grant Number: HID98-1056-C02-01

An afforestation experiment with the drought resistant species Pinus halepensis Miller was conducted in a degraded semiarid rangeland of southeastern Spain to evaluate the influence of site preparation on soil moisture and seedling performance. Three different land preparation treatments were tested: manual terracing, mechanical terracing and mechanical terracing with organic amendment addition. Mechanical terracing (+/− organic amendment) always included subsoiling. Soil moisture to a depth of 1 m was monitored by the neutron scattering method during a 28-month-period. The study revealed significant differences among land treatments with respect to soil moisture content and water uptake by the seedlings. Mechanical terracing increased soil water storage up to 40% more effectively than manual terracing. Analysis of moisture depletion rates at different soil depths indicated that seedling access to the water stored into the deeper layers of the profile was constrained by high soil penetration resistance in the manual terraces. As a result of limited water availability, seedling survival after the dry summers of 1994 and 1995 was only 62% in this treatment (98% in the mechanical terraces). The addition of urban solid refuse (USR) further increased the water reserve in the mechanically terraced soils (up to 40%), due to enhanced water infiltration and diminished evaporation from the soil surface. Early root penetration to the deeper and wetter layers of the profile also contributed to increased water availability for the seedlings in the mechanical terraces+USR. Two years after planting, only the seedlings in this treatment were able to deplete homogeneously the moisture stored into the soil profile to a depth of 1 m., This work was funded by the Spanish Comision Interministerial de Ciencia y Tecnologia (CICYT), Projects FOR-91-0352, AGF-95-0097 and AGF-99-1132.

The factors which control soil moisture patterns in a semiarid area are determined in two different locations: a burnt zone with little vegetation and an unburnt zone with a greater vegetal cover. In the burnt area, the factors affecting the spatial variability of the soil water content are those considered as local controls such as soil texture and slope. These factors are able to explain a significant part of the spatial distribution of soil moisture in this zone independently of the soil moisture state. In the unburnt area, the factors affecting soil moisture were those related with the presence or absence of vegetation in semiarid environments. The upslope contributing area, aspect, soil profile curvature and soil depth best explained the spatial variability of the soil moisture content in the vegetated zone. The actual influence of these factors showed marked seasonal variations due to changes in the physiological activity of the vegetal cover. These factors, which are in part responsible for the distribution of soil moisture, are not commonly integrated in traditional topographic wetness indices. The topographic index of Beven and Kirkby (Beven, K.J., Kirkby, M., 1979. Hydrological Sciences Bulletin 24, 43–69) is extended to account for the interstorm soil water losses. The new indices incorporating the hillslope aspect improve the prediction power of soil water content patterns in semiarid areas., Financial support from Spanish CICYT (HID98-1056-CO2-01) and Dirección General de Conservación de la Naturaleza-MIMAM (Programa RESEL).

9 pages, 6 tables., Soil amendment with organic materials prior to afforestation as well as the use of mycorrhizal inoculation, are advisable practices in afforestation of semiarid areas. In this work, the effect of both organic amendment and mycorrhizal treatment on the microbial activity of a soil afforested with Aleppo pine (Pinus halepensis Miller) was studied. Labile carbon fractions (water soluble carbon and water soluble carbohydrates), microbiological parameters (microbial biomass carbon, basal respiration and metabolic quotient), and enzyme activities such as oxydoreductases (deshydrogenase and catalase activities) and hydrolases (urease, protease and phosphatase) were determined. All these parameters were found positively influenced by organic amendment and mycorrhizal treatment of plant roots by inoculation of fungi or forest soil addition. The best result was obtained when mycorrhizal inoculation with fungi was supplemented by organic amendment., This work was funded by the CICYT (Comision Interministerial de Ciencia y Tecnologia), Project AGF-95-0097.

Nous avons mis en place un essai d'amelioration de la croissance de jeunes plantations de Pinus halepensis dans une zone semi-aride du sud-est de l'Espagne. Les traitements suivants ont ete appliques comme facteurs principaux: travail mecanique du sol en terrasses, travail manuel du sol, travail du sol en terrasse avec apport d'un amendement organique constitue de residus solides urbains, et travail manuel du sol avec apport d'un amendement organique. Un apport de sol forestier a ete applique en deuxieme facteur. Vingt et un mois apres la plantation, le travail du sol avec amendement organique augmente significativement la croissance de P halepensis. Le traitement qui combine le travail mecanique du sol et un amendement organique a ete le plus efficace sur la survie et l'amelioration de la croissance des pins. L'apport de sol forestier a un effet positif sur la croissance des pins sauf dans le traitement qui combine travail manuel du sol et amendement organique. La croissance de P halepensis est correlee a la teneur en eau du sol (r = 0,83; P 0,01) qui est la plus elevee dans le traitement qui combine travail mecanique du sol et amendement organique. La teneur en phosphore qui est amelioree par les amendements organiques est correlee avec la croissance des plants (r = 0,75; P = 0,05). L'effet positif d'un apport du sol forestier parait etre de nature microbiologique.