Pinus radiata site quality study in the Basque Country (Spain) using nutritional and physiographical criteria

Nutrient status in Pinus radiata sites in the Basque Country (Spain) have been established. Current-year, 1-year-old needles, and soil samples were collected in 7 sites. Needle samples were analyzed for calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P) and nitrogen (N). Soil samples were analyzed for pH (H₂O), N, P, Ca, Mg, K and aluminium (Al). The results indicate differences between sites and needles of different ages. In general, nutrient concentrations in needles are sufficient for the nutritive requirements, but some low concentrations of Mg and P found in 1-year-old needles, indicate that some trees may show signs of deficiency in the near future. In turn, N concentrations are, in many cases, higher than those usually found in this species and may originate growth disorders. These concentrations may be related to NO₃ ^? and NH₄ ⁺ deposition. Soil nutrients are sufficient for trees requirements, but the levels of K and Mg are low. Soil pH values are not very acid, and the value of the Ca/Al ratio is, in general, near 1. An arrangement of sites and physiographical and nutritional parameters based on correlation and principal component analysis is also presented.     

Wild edible plants traditionally gathered in Gorbeialdea (Biscay, Basque Country)

This ethnobotanical study aims to describe the domain of wild edible plants in Gorbeialdea (Biscay, Iberian Peninsula), and to assess the cultural importance of the different species and food categories. Field work was conducted between 2008 and 2010, interviewing 103 informants about the traditional use of wild plants for food. The edible use of 49 species was recorded, 45% of them gathered for their fruits. The most important species coincide with those registered in other regions in the north of the Iberian Peninsula (Prunus spinosa, Rubus ulmifolius, Castanea sativa, Fragaria vesca, Rumex acetosa, Vaccinium myrtillus and Arbutus unedo). However, the importance of some species and uses that had not been previously recorded as edible in the ethnobotanical literature of the Iberian Peninsula, highlights the singularity of the area. The consumption of the leaves of Fagus sylvatica, the seeds of Pinus radiata, and the shoots of Pteridium aquilinum are some examples of specific uses. The eating of the fruits of Quercus robur, and Q. ilex was common until some decades ago and is still remembered by the informants. However, the consumption of those fruits has now a social stigma, and as shown in this paper, it can be overlooked by a methodology only based on open interviews. The most important use-category was ‘fruits’, following the trend found in other northern regions of the Iberian and Italian Peninsulas. ‘Snack vegetables’ is also a relevant category, including 35% of the cited species, with a high diversity of chewed plants, mainly as hunger or thirst quenchers. On the contrary, there was a low valorization of condiments and elaborated vegetables.     

Metal Pollution by Old Lead-Zinc Mines in Urumea River Valley (Basque Country,Spain). Soil,Biota and Sediment

Soil, aquatic biota (moss: Brachythecium rivulare; aquatic macrophytes: Juncus effusus, Potamogeton crispus; fish: Salmo trutta fario, Anguilla anguilla, Phoxinus phoxinus, Chelon labrosus) and sediment samples from the Urumea river valley were analysed for metals by acid digestion and atomic absorption spectroscopy. The sediments show the presence of metal pollution (Cd: 2.5–24 mg kg^-1; Pb: 125–1,150 mg kg^-1; Zn: 125–2,500 mg kg^-1) because mining and industrial wastes. A selective retention of dense minerals in dam sediments contributes to the load of metal, but interstitial water analysis (Cd: <0.02–0.1 mg L^-1; Pb: 0.3–1.0 mg L^-1; Zn: <0.05–0.6 mg L^-1) shows that precipitation equilibrium controls their mobilisation. Biota samples show evidence of metal accumulation, moss reaching 1,100 mg kg^-1 in lead and 6,800 mg kg^-1 in zinc. Soil from the valley is polluted by both, river carried material and industrial sources (Cd: 1.0–4.0 mg kg^-1; Pb: 26–1,120 mg kg^-1; Zn: 105–1,390 mg kg^-1/math>), but they are used, indistinctly, for farming and pasture.     

Chemical and mineralogical characterization of soils derived from ophites in mediterranean climate (North of Spain)

Abstract

We have studied the chemical and mineralogical characteristics of ophites located in a diapiric formation in Burgos (North of Spain), and the soils derived from them. The ophites studied show mineralogical uniformity. Their main components are clinopyroxenes, plagioclases, biotite, and olivine. Generally, they show deuteric alteration mainly affecting the olivine. The presence of talc is attributed to an outpouring of basic magma (ophite) in an evapotiric environment of Keuper facies. Chemically, they are basic rocks, of basaltic nature, poor in silicon dioxide (SiO₂) and rich in magnesium oxide (MgO) and ferric oxides (Fe₂O₃). The weathering of the ophites results in clay consisting of chlorite, vermiculite, and interlayer chlorite‐vermiculite‐smectite inherited from original material. Small amount of extractable silica (Si), aluminum (Al), and iron (Fe) show the scarcity of amorphous material attributed to the high content in organic carbon (C) which prevents formation of allophane, and to the xeric moisture regime of soils in this location.     

Nitrous oxide emissions from grassland in an intensive dairy farm in the Basque Country of Spain

Abstract. Intensively managed grasslands are potentially a large source of N₂O in the North Coast of Spain because of the large N input, the wet soil conditions and mild temperatures. To quantify the effect of fertilizer type and management practices carried out by farmers in this area, field N₂O losses were measured over a year using the closed chamber technique. Plots received two types of fertilizer: cattle slurry (536 kg N ha^–1) and calcium ammonium nitrate (140 kg N ha^–1). N₂O losses were less in the slurry treatment than after mineral fertilizer. This was probably due to high, short‐lived peaks of N₂O encountered immediately following mineral N addition. In contrast, the seasonal distribution of N₂O losses from the slurry amended plot was more uniform over the year. The greater N₂O losses in the mineral treatment might have been enhanced by the combined effect of mineral fertilizer and past organic residues present from previous organic amendments. Weak relationships were found between N₂O emission rates and soil nitrate, soil ammonium, soil water content and temperature. Better relationships were obtained in the mineral treatment than in the slurry plots, because of the wider range in soil mineral N. Water filled pore space (WFPS) was a key factor controlling N₂O emissions. In the > 90% WFPS range no relationships were found. The best regressions were found for the mineral treatment in the 40–65% WFPS range, 49% of the variance being explained by soil nitrate and ammonium content. In the 65–90% WFPS range, 43% of the variance was explained by nitrate only, but the inclusion of soil ammonium did not improve the model as it did in the 40–65% WFPS range. This fact indicates that nitrification is likely to be an important process involved in N₂O emissions at the 40–65% WFPS.     

Organic carbon stocks in the soils of Brazil

Abstract. Soil organic carbon stocks to 1 m for Brazil, calculated using an updated Soil and Terrain (SOTER) database and simulation of phenoforms , are 65.9–67.5 Pg C, of which 65% is in the Amazonian region of Brazil. Other researchers have obtained similar gross results, despite very different spatial patterns mapped due to use of different methods.     

Effect of management and climate on biochemical properties of grassland soils from Galicia (NW Spain)

Biochemical properties are considered to be the best indicators available at present for assessing soil quality. However, there are still many gaps in our knowledge about how these properties are affected by abiotic factors and how these factors interact with soil management. With the aim of understanding how climate and soil management affect soil biochemical properties in grasslands soils from a temperate-humid area (Galicia, NW Spain), a total of 60 soils were analyzed for several microbial and biochemical properties. Grasslands were divided into groups according to the type of management applied (native compared with intensive) and to the climate in the area where they were sampled (Mediterranean subhumid with centroeuropean drift climate compared with Atlantic climate). We found that management had a greater influence on soil biochemical properties than climate. Altitude, which strongly influences climate in the region where the soils were analyzed, was found to be a significant factor that affected most soil biochemical properties. In conclusion, the results show that microbially-mediated processes are greatly affected by both, management and abiotic factors and that, for some properties (like net N mineralization and cellulase and casein-protease activities), abiotic factors can have an important influence on soil biochemical properties.     

Land evaluation for forestry: a study of the land requirements for growing Pinus radiata D. Don in the Basque Country, northern Spain

Land requirements for the growth of Pinus radiata D. Don were studied in 112 plots by comparing site index (SI) values with land characteristics. The SI at the reference age of 20 years ranged from 10.4 to 32.7 m. The growth of Radiata pine increased as soil rootable depth increased, with a mean depth of about 50 cm in plots with an SI higher than 29 m. The results show that soil physical properties had a major influence on growth rates with soils of a loamy texture resulting in higher rates than clay rich soils. Soil nitrogen and phosphorus availability had significant effects on growth on soils developed on non‐volcanic parent material whilst potassium availability was significant in soils on volcanic parent material. There were strong interactions among the land characteristics of each land unit so that the magnitude of the specific effect of a given variable was highly dependent on the values of the others. Results are discussed in relation to land use planning.     

Organic carbon ranges in arable soils of England and Wales

Abstract. Knowledge of the stocks and the potential range of soil organic carbon (SOC) in various land–soil combinations is an important precursor to policies aimed at linking, for example, management of SOC to greenhouse gas emission controls. To investigate the factors controlling the percentage of SOC (%SOC) of soils in England and Wales, we made a multiple regression analysis of data for the 2448 arable and ley-arable sites in the 1980 England and Wales National Soil Inventory (NSI). Clay content, average annual precipitation and depth of topsoil explained 25.5% of the variation in %SOC, when calcareous and peaty soils and those susceptible to flooding were excluded. Using 'robust' statistics, 'indicative SOC management ranges' were estimated for different physiotopes, that is, landscape units for which the environmental factors governing %SOC are similar, namely soil clay content and precipitation. These ranges describe the expected %SOC range for an arable soil in a given physiotope. They have potential to support approximate targets for the %SOC of arable soils and for estimating upper and lower limits for sequestered soil carbon in arable systems.     

The historic man-made soils of the Generalife garden (La Alhambra, Granada, Spain)

We studied the soils of the Patio de la Acequia garden of the Generalife, a palatial villa forming part of La Alhambra, a World Heritage Site in Granada, Spain. This garden, which is estimated to be around 700 years old, is the oldest historical garden in the Western World. The soils are man‐made cumulimollihumic‐calcaric (hypereutric, anthric) Regosols. Noteworthy amongst the main pedogenic processes, in relation to the human activities of cultivation, irrigation and tillage, are horizonation, melanization (the contents of organic carbon varied between 0.59% and 8.87%, and those of P₂0₅ extracted with citric acid between 723 mg kg⁻¹ and 7333 mg kg⁻¹, with maximae in the Ap horizons) and structure formation. The soil fabric, studied at the ultramicroscopic level using scanning electron microscopy, is of laminar and partition‐walls’ type in the lower horizons, depending on the microped zones. The partition‐walls’ fabrics found are different to those of the possible pre‐existing sedimentary fabrics. These are numerous lithological discontinuities and at least two burials, leading us to deduce that there have been two main stages of filling with materials in the formation of these soils. The first is Arabic‐Medieval (13th century), when the garden was created, its surface being some 50 cm below the level of the paved area of the present patio. In the deeper parts, the materials employed in the fill are similar to the in situ soils of the zone, unaffected by the buildings. The second stage is Christian (15th century to the present day). During this period the Medieval garden was gradually buried under a layer of materials from the nearby soils and/or sediments mixed with manure until the surface was only just below the level of the paved area of the patio. In this work we discuss the difficult classification of these relatively little studied soils. In spite of their being clearly related to human activity, they are not classified as Anthrosols in the FAO system (1998) because soil materials cannot be classified as anthropopedogenic or as anthropogeomorphic.     

Sorption of dissolved organic carbon in soils: effects of soil sample storage,soil-to-solution ratio,and temperature

Experiments on the sorption of dissolved organic carbon (DOC) in soils were mainly conducted in batch approaches. Because varying setups were used in these studies, comparison of the results requires knowledge on the effects that different experimental conditions may have on the sorption of DOC. This investigation evaluated the DOC sorption of soils using differently pretreated soil samples (field-fresh (two sampling dates), air-dried, stored at 3°C and −18°C), at different soil-to-solution ratios (1:40, 1:20, 1:10 and 1:5 w/v) and different temperatures (5°C, 15°C, 25°C and 35°C). The sorption of DOC was analyzed using the initial mass (IM) approach, which regressed the initial amount of sorbate (normalized to soil mass) against the sorbed amount (normalized to soil mass). The DOC release — when a solution without DOC was added — strongly increased with temperature and soil-to-solution ratio. Among the different types of sample storage and preparation, air-drying resulted in the largest DOC release. The smallest release was from the field-fresh samples. Freezing and storage at 3°C resulted in intermediate DOC release with freezing having the greater effect. The release from air-dried samples exceeded that of field-fresh samples by a factor of four at maximum. In contrast, none of the experimental setups influenced the slope of the IM isotherms. Thus, it seems possible to compare directly the binding affinity of DOC to different soils as determined at varying experimental conditions.     

蔬菜连作对铜尾矿土壤中有机碳、腐殖质碳以及可溶性有机碳的影响

Carbon of humus acids （HSAC） and dissolved organic carbon （DOC） are the most active forms of soil organic carbon （SOC） and play an important role in global carbon recycling. We investigated the concentrations of HSAC, water-soluble organic carbon （WSOC）, hot water-extractable organic carbon （HWOC） and SOC in soils under different vegetation types of four copper mine tailings sites with differing vegetation succession time periods in Tongling, China. The concentrations of HSAC, WSOC, HWOC and SOC increased with vegetation succession. WSOC concentration increased with the accumulation of SOC in the tailings, and a linearly positive correlation existed between the concentrations of HSAC and SOC in the tailings. However, the percentages of HSAC and DOC in the SOC decreased during vegetation succession. The rate of SOC accumulation was higher when the succession time was longer than 20 years, whereas the speeds of soil organic matter （SOM） decomposition and humification were slow, and the concentrations of HSAC and DOC increased slowly in the tailings. The percentage of carbon of humic acid （HAC） in HSAC increased with vegetation succession, and the values of humification index （HI）, HAC/carbon of fulvic acid, also increased with the accumulation of HSAC and SOC in soils of the tailings sites. However, the HI value in the each of the tailings was less than 0.50. The humification rate of SOM was lower than the accumulation rate of SOM, and the level of soil fertility was still very low in the tailings even after 40 years of natural restoration.     

Potential effects of the increase in carbon dioxide and climate change on the dynamics of vegetation

The continued CO₂ loading of the atmosphere appears to be responsible for inducing three new force factors controlling dynamic changes in the world's vegetation. They come from (1) enhanced fertilization with the single most important plant nutrient, (2) the widely expected global temperature increase, and (3) aggravated weather disturbances. Increased CO₂ absorption may enhance plant growth but it may also increase soil-nutrient limitations. It surely will enhance the metabolism of forest trees similarly as global warming will enhance plant metabolism, but both factors may also shorten the lifespan of perennial plants. Increased weather disturbances can be expected to produce new physiological stresses on the standing vegetation, particularly on habitats with poor soils. Since wide-spread forest decline has been reported from both the Atlantic and Pacific region, it seems possible that the roughly synchronie mass mortality of trees during the past two decades is related to the global increase in CO₂. The paper gives an overview of forest decline and dieback as known from past and present research and suggests how the changing atmospheric environment may interact in this widely observed contemporary phenomenon of vegetation dynamics.     

Carbon storage in loess derived surface soils from Central Germany: Influence of mineral phase variables

The influence of the soil mineral phase on organic matter storage was studied in loess derived surface soils of Central Germany. The seven soils were developed to different genetic stages. The carbon content of the bulk soils ranged from 8.7 to 19.7 g kg^—1. Clay mineralogy was confirmed to be constant, with illite contents > 80 %. Both, specific surface area (SSA, BET‐N₂‐method) and cation exchange capacity (CEC) of bulk soils after carbon removal were better predictors of carbon content than clay content or dithionite‐extractable iron. SSA explained 55 % and CEC 54 % of the variation in carbon content. The carbon loadings of the soils were between 0.57 and 1.06 mg C m^—2, and therefore in the ”︁monolayer equivalent” (ME) level. The increase in SSA after carbon removal (ΔSSA) was significantly and positively related to carbon content (r² = 0.77). Together with CEC of carbon‐free samples, ΔSSA explained 90 % of the variation in carbon content. Clay (< 2 μm) and fine silt fractions (2—6.3 μm) contained 68—82 % of the bulk soil organic carbon. A significantly positive relationship between carbon content in the clay fraction and in the bulk soil was observed (r² = 0.95). The carbon pools of the clay and fine silt fractions were characterized by differences in C/N ratio, δ¹³C ratio, and enrichment factors for carbon and nitrogen. Organic matter in clay fractions seems to be more altered by microbes than organic matter in fine silt fractions. The results imply that organic matter accumulates in the fractions of smallest size and highest surface area, apparently intimately associated with the mineral phase. The amount of cations adhering to the mineral surface and the size of a certain and specific part of the surface area (ΔSSA) are the mineral phase properties which affect the content of the organic carbon in loess derived arable surface soils in Central Germany most. There is no monolayer of organic matter on the soil surfaces even if carbon loadings are in the ME level.     

Fluxes and storage of fine-grained sediment and associated contaminants in the Na Borges River (Mallorca,Spain)

Samples of suspended and fine channel bed sediment were used to examine the spatial and temporal variability in the amount of fine-grained sediment and associated contaminants temporarily stored in the Na Borges River (319 km²) in Mallorca and the relationship of such channel storage to the fluxes of fine sediment and associated contaminant through the system. This Mediterranean groundwater-dominated river drains a predominantly agricultural catchment, although urbanisation during the twentieth century has changed the catchment hydrology. A re-suspension technique was used to obtain estimates of channel storage at monthly intervals during the 2004–2005 hydrological year at eight locations along the main stem of the stream (i.e. 26 km). The estimates of fine sediment storage ranged between 0 and 13,000 g m^− 2, with a mean value of 2400 g m^− 2. Only Cu exceeded the critical threshold (36 μg g^− 1), established by existing guidelines for the contaminant content of fluvial sediment. The results demonstrated significant spatial and temporal variability, in response to the influence of urban point sources, agricultural practises, seasonal groundwater interactions and the first-flush effect. The amount of fine sediment entering storage during the study period was 515.2 t, representing the net increase in storage over the study period. As a result, the mean specific storage was 21 t km^− 1. Suspended-sediment load and temporary fine sediment storage are the two basic components of the channel sediment budget that interact to determine sediment transport through a channel system, and they can therefore be used to compute the total input of sediment and associated contaminants to the system. Accordingly, storage values were compared with estimates of suspended sediment load and associated contaminant load values at three measuring stations along the river. During the study period, storage in the main channel system represented 87% of the sediment input and 68% of the contaminant input, indicating that deposition was more important than transport. The low gradient of the main channel and the low return period (i.e. 0–2.5 years) of the flood events that occurred during the study period meant that remobilised bed sediment and associated contaminants were redeposited downstream rather than being flushed to the catchment outlet as suspended sediment. Furthermore, the river bed is dry during the summer months, allowing sealing and crusting processes to stabilise the sediment deposited during the wet season and thereby reduce its availability for remobilisation at the beginning of the next wet season. Together, these factors promote sediment deposition and storage, with the result that sediment progressively accumulate over several hydrological years until a major flood event (i.e. return period ≈ 5 years) evacuates the stored sediment.     

Assessment of potentially toxic element contamination in soils from Portman Bay (SE,Spain)

Purpose

The present study deals with the geochemical fractions of Pb, Cd, Zn, Cu and As present on profiles using chemical simple extraction process. This work was conducted on Portman Bay, located in the SE Spain and strongly affected by mining activities.

Materials and methods

Four simple extractions were applied to selected samples in order to evaluate the potential mobility of metals. X-ray diffraction (XRD) was applied to the characterisation of samples and the residues remaining after each extraction, providing additional information about the sediment phases carrying the elements studied.

Results and discussion

The results obtained after the extractions suggested that the highest potentially toxic element (PTE) content was obtained in the oxidising medium. The mineralogical composition is an important factor that should be taken into account in the evaluation of PTE mobility, firstly because the mineral phases react differently in the proposed situations depending on their chemical nature, and secondly, because the presence of a particular phase depends on the degree of weathering.

Conclusions

The evaluation of PTE mobility and mineralogical composition under different environmental conditions may be very important in the execution of restoration projects which could involve dredging and mobilisation of materials.

     

Mobility of sulphate in experimentally acidified soils from Galicia (NW Spain)

Retention of S0₄ ^2? was investigated in Galician soils throughout an intense regime of acidification. Experiments consisted of the addition of an H2SO4 solution (pH 2.7) to columns of 6 soils of contrasting properties over 1, 2, or 5 months. Leachates were obtained continuously throughout the experiment for analysis, and analysis made of the solid fractions after 1, 2 or 5 months. The greatest capacities for retention of S0₄ ^2? were found in soil developed from serpentine and micaschist; the lowest in soils from granite, slate and sandy sediments. The surface horizons, especially those rich in organic matter, displayed low retention of 5042-. The amount of S0₄ ^2? adsorbed throughout the experiment depended on the content of crystalline forms of Fe and with the Fe and Al extracted with dithionite-citrate.The low retention of S0₄ ^2? in the organic horizons and the slightly negative relation with the organic matter suggest an inhibitory effect of the organic matter on the S0₄ ^2? retention process. Results of the study show, that under conditions of moderate acidity, SO₄ ^2? retention occurs in the form of adsorption; in strongly acidic conditions, the precipitation of aluminium-sulphate minerals may provide an additional retention mechanism.