C. Guerrero

Universidad Miguel Hernández de Elche, Elche, Valencia, Spain

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Publications (56)89.39 Total impact

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    ABSTRACT: This study addressed the impacts of wildfire and, in particular, its severity on the seed bank of the litter/ash layer and the topsoil of a Mediterranean pine plantation (Pinus pinaster Ait.) in north-central Portugal. The study location was selected for presenting a homogeneous pine cover before the fire, on the one hand, and, on the other, heterogeneous patches with distinct degrees of damage to the pine crowns immediately after the fire. The experimental design involved the selection, from the opposite valley side, of three zones with adjacent strips of Low and High Canopy Consumption (L/HCC). Within each of these strips, a transect was laid out along which three plots were established at 10 m intervals. The same was done in the unburnt area immediately outside the fire perimeter. At each plot, samples were collected within the first two weeks after the fire to: (i) asses viable seed densities for three sampling layers, using the indirect method for a 10-month period; (ii) estimate maximum temperature reached (MTRs) at 0–3 cm depth, on the basis of Near Infrared Spectroscopy (NIR). Fire severity at the plots was further determined by verifying, in situ, pine canopy consumption (FCC) as well as by measuring the minimum diameter of remaining shrub twigs (TDI). In comparison with the unburnt area, the recently burnt area as a whole revealed a substantial increase in overall densities of viable seeds. Seed bank composition, however, varied markedly within the burnt area but this could be explained reasonably well by differential effects of the wildfire associated with its severity, in terms of the two crown consumption classes as well as the TDI index but not the MTRs. The inclusion of the litter/ash layer and the separation of two soil depths were amply justified by providing clear support for the important role of fire severity, in particular for the two principal taxa (Calluna vulgaris and Erica spp., presum-ably mainly E. australis).
    Geoderma 04/2012; 191:80-88. · 2.51 Impact Factor
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    ABSTRACT: Wildfire is the major disturbance in Mediterranean forests. Prescribed fire can be an alternative to reduce the amount of fuel and hence decrease the wildfire risk. However the effects of prescribed fire must be studied, especially on ash properties, because ash is an important nutrient source for ecosystem recovery. The aim of this study is to determine the effects of a low severity prescribed fire on water-soluble elements in ash including pH, electrical conductivity (EC), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), aluminum (Al), manganese (Mn), iron (Fe), zinc (Zn), silica (SiO(2)) and total sulphur (TS). A prescribed fire was conducted in a cork oak (Quercus suber) (Q.S) forest located in the northeast part of the Iberian Peninsula. Samples were collected from a flat plot of 40×70m mainly composed of Q.S and Quercus robur (Q.R) trees. In order to understand the effects of the prescribed fire on the soluble elements in ash, we conducted our data analysis on three data groups: all samples, only Q.S samples and only Q.R samples. All three sample groups exhibited a significant increase in pH, EC (p<0.001), water-soluble Ca, Mg, Na, SiO(2) and TS and a decrease in water-soluble Mn, Fe and Zn. Differences were identified between oak species for water-soluble K, Al and Fe. In Q.S samples we registered a significant increase in the first two elements p<0.001 and p<0.01, respectively, and a non-significant impact in the third, at p<0.05. In Q.R data we identified a non-significant impact on water-soluble K and Al and a significant decrease in water-soluble Fe (p<0.05). These differences are probably due to vegetation characteristics and burn severity. The fire induced a higher variability in the ash soluble elements, especially in Q.S samples, that at some points burned with higher severity. The increase of pH, EC, Ca, Mg, Na and K will improve soil fertility, mainly in the study area where soils are acidic. The application of this low severity prescribed fire will improve soil nutrient status without causing soil degradation and thus is considered to be a good management strategy.
    Environmental Research 02/2011; 111(2):237-47. · 3.24 Impact Factor
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    ABSTRACT: The aim of this study was to investigate the feasibility of using near-infrared (NIR) spectroscopy as an easy, inexpensive and rapid method to predict stability parameters in sewage sludge and compost derived there from. In the compost samples, predictions were successful (residual predictive deviation (RPD) higher than 2) for both CO2 accumulation after 8 days using alkali (NaOH) traps (CO2 NaOH 8d) and compost age. Predictions were moderately successful (RPD between 1.4 and 2) for water-soluble carbon (WSC), E2/E3 and E4/E6 ratios (ultraviolet–visible measurements in the water-soluble extract) and ash content. In sewage sludge, predictions were successful (RPD = 2.99) for ash content, moderately successful (RPD = 1.60) for WSC and CO2 NaOH 8d (RPD = 1.42), and unsuccessful (RPD < 1.4) for E2/E3 and E4/E6 ratios. The RPD values obtained for the predictions of properties provided by an automatic respirometer (maximum rates of O2 and CO2 and cumulative values after 8 and 30 days) in compost and sewage sludge ranged between 2.02–2.84 and 1.81–2.36, respectively. The low accuracy obtained for the prediction of the CO2 NaOH 8d in sewage sludge illustrated how high levels of respiration can affect the accuracy of the NaOH trap method. Global models combining the compost and sewage sludge samples were constructed and used for the prediction of data provided by the automatic respirometer, achieving RPD values higher than 3.5. This work demonstrates the potential of NIR spectroscopy for predicting certain parameters related to the stability of sewage sludge and its derived compost.
    Geoderma 08/2010; 158(1-2):93-100. · 2.51 Impact Factor
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    ABSTRACT: A field experiment was carried out in a semiarid agricultural Mediterranean area located at the “El Teularet” experimental field in the Enguera Sierra (Valencia, southeast Spain) to assess the influence of different agricultural management systems on indicators of soil biological quality and activity (microbial biomass C, basal respiration, C mineralization coefficients, metabolic quotient (qCO2), respiratory quotient (RQ: moles CO2 evolved/moles O2 consumed), soluble C and dehydrogenase, urease, protease-BAA, phosphatase and β-glucosidase activities), one year after treatment establishment. The management practices assayed were as follows: application of the herbicides paraquat, glyphosate or oxyfluorfen, addition of olive tree pruning residues, ploughing, sowing of oats + addition of crop residues + ploughing, sowing of Medicago sativa, sowing of oats and vetch + addition of crop residues and addition of oat straw. A non-treated plot was used as control soil and a plot under natural vegetation was used as a standard of local, high quality soil. The plots with addition of oat straw had higher values of enzymatic activity, microbial biomass and respiration, reaching similar values to soil under native vegetation. The lowest levels of soil biological quality indicators were observed in the plots with application of some type of herbicide. Low RQ values were observed in these plots as consequence of the scarce-null inputs of organic matter, suggesting an increase in organic matter recalcitrance. The addition of oat straw to soil can be considered an effective technology, due to the rapid improvement of soil quality, for carrying out sustainable agriculture in semiarid Mediterranean agroecosystems.
    Soil and Tillage Research 08/2010; 109:110-115. · 2.58 Impact Factor
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    ABSTRACT: Near infrared reflectance (NIR) spectroscopy has many advantages because it is a rapid and cost-effective technique. A needed steep is the development of soil spectral libraries and models (calibrations using multivariate techniques). The calibrations should contain the variability of the target site soils on which the models are to be used. Many times this premise is not easy to fulfil. A classical way to solve this problem is by the spiking of models with a few samples from the target site (local samples), and the subsequent recalibration of models. In this regional-scale study we hypothesized that small-sized models should integrate the spectral characteristics of local samples more easily than large-sized models and as consequence should produce more accurate predictions. With the aim to test this hypothesis different-sized models were constructed using different quantities of soil samples. Partial least squares (PLS) regression was used to construct the models which were relating NIR spectra to the Nitrogen Kjeldahl (NKj) contents in soil samples. Two strategies were used for the selection of samples in models: (i) strategy based on spectra characteristics (SC) and (ii) strategy based on NKj values (NV) of the samples. These different-sized models were sequentially spiked with local samples from target sites and recalibrated. The predictions accuracies obtained with the models before and after spiking were studied being the NKj the soil property selected. In general all predictions were very accurate including those obtained before the spiking of models. Predictions accuracy increased as consequence of spiking in three of the four target sites studied. A negative trend was observed between prediction accuracy and model size. The lower errors were obtained using small-sized models after spiking which were more accurate than local models too. It was noticeable the high accuracy obtained by local models which were constructed using only 20 local samples. Before spiking SC models were more accurate than NV models but scarce differences between both strategies were observed after spiking with 20 samples. The results suggested that small-sized models can be useful for local predictions after spiking and they were also emphasizing the relevant role of local samples in models. The results obtained could encourage the expansion of this technique because large data based seem not be needed. Therefore NIR users could primarily focus most of their efforts on obtaining highly accurate analytical values in a few set of samples.
    Geoderma 08/2010; 158:66-77. · 2.51 Impact Factor
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    Geoderma 08/2010; 158(1-2):1-2. · 2.51 Impact Factor
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    ABSTRACT: Soil water repellency (WR) is one of the properties most affected by combustion during a forest fire. Measurements of water repellency can be made directly in field or in soil samples under laboratory conditions. In other hand, previous laboratory findings have demonstrated that soil properties can be a key factor controlling the development of WR by burning, terra rossa being a type of soil with a low susceptibility to develop WR. One of the objectives of this research was to confirm laboratory findings under field conditions. In summer 2008 WR was assessed in five areas recently affected by fires in MT. Carmel (NW Israel) and Alicante (SE Spain). The main difference between areas was the type of soil. Two of the soils were classified as Typic Xerorthents, another two as Lithic Rhodoxeralfs (terra rossa) and the other as a Calicixerept. In each one of the study areas WR was tested beneath Pinus halepensis in both burned and unburned (control) adjacent sites. WR tests were conducted under field conditions in triplicate using the water drop penetration time (WDPT) test in the top of the A horizon. A total of 300 field measurements were done. Soil samples from the first 0-2.5cm depth were also taken from the same places where WR was assessed for laboratory measurements. In general terms, without distinguishing between areas, fire increased the frequency of occurrence of WR in affected soils. However, the magnitude of this effect is quite different depending on the studied area. The study sites with terra rossa soils showed the lowest WR values. Most of samples were wettable (
    05/2010;
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    ABSTRACT: In semiarid ecosystems plant cover plays an important role in the improvement of physical, chemical and biochemical soil properties. With the aim of studying the influence of different plant species on soil properties, and establishing the relationships between them, 160 soil sam-ples from under four different plant species (Pinus halepensis, Quercus coccifera, Juniperus oxycedrus and Rosmarinus officinalis) were taken in a forest area of the province of Alicante (SE Spain). The following soil pro-perties were analyzed in all soil samples: organic carbon content, microbial biomass, soluble organic carbon, aggre-gate stability, basal respiration, and some eco-physiological ratios. In addition, the near infrared spectra (NIR) of all soil samples were obtained to verify the similarities or differ-ences between soil samples under the four species. Some differences in parameters such as organic carbon content or basal respiration were found mainly between the group of P. halepensis and Q. coccifera with respect to J. oxycedrus and R. officinalis. Despite this, the high organic carbon content found under the four plant species showed an influence on the rest of soil properties. Moreover, using a discriminant analysis with factorial scores from NIR absorbance data did not result in a good classification of samples in terms of the species, reflecting some similarities between them. Our results show that the high contents observed in some parameters under the four species, and the lack of significant differences in most of them, prove the important role of shrubland in semiarid conditions, it being capable of promoting good soil conditions.
    European Journal of Forest Research 01/2010; 129:15-24. · 1.68 Impact Factor
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    ABSTRACT: In Spain, agriculture triggers soil degradation and erosion processes. New strategies have to be developed to reduce soil losses and recover or maintain soil functionality in order to achieve a sustainable agriculture. An experiment was designed to evaluate the effect of different agricultural management on soil properties and soil erosion. Five different treatments (ploughing, herbicide, control, straw mulch and chipped pruned branches) were established in “El Teularet experimental station” located in the Sierra de Enguera (Valencia, Spain). Soil sampling was conducted prior to treatment establishment, and again after 16 months, to determine soil organic matter content (OM), aggregate stability (AS), and microbial biomass carbon content (Cmic). Fifty rainfall simulations tests (55mm during one hour, 5-year return period) were applied to measure soil and water losses under each treatment. The highest values of OM, AS and Cmic were observed in the straw-covered plot, where soil and water losses were negligible. On the contrary, the plot treated with herbicides had the highest soil losses and a slight reduction in Cmic. Soil erosion control was effective after 16 months on the plots where vegetation was present while on the ploughed and herbicide-treated plots, the practices were not sustainable due to large water and soil losses. Except for the straw mulch plot, soil properties (OM, AS, Cmic) were not enhanced by the new land managements, but soil erosion control was achieved on three of the five plots used (weeds, weeds plus straw and weeds plus chipped pruned branches). Erosion control strategies such as weeds, weeds plus straw mulch and weeds plus chipped branches mulch are highly efficient in reducing soil losses on traditional herbicide-treated and ploughed agricultural land. However, it takes longer to recover other soil properties such as OM, AS, and Cmic.
    Soil and Tillage Research 12/2009; 106(1):117-123. · 2.58 Impact Factor
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    ABSTRACT: Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
    Arid Land Research and Management 10/2009; 23:267-282. · 0.56 Impact Factor
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    ABSTRACT: Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
    Arid Land Research and Management 07/2009; 23:3213-222. · 0.56 Impact Factor
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    ABSTRACT: In Eastern Spain, almond trees have been cultivated in terraced orchards for centuries, forming an integral part of the Mediterranean forest scene. In the last decades, orchards have been abandoned due to changes in society. This study investigates effects of changes in land use from forest to agricultural land and the posterior land abandonment on soil microbial community, and the influence of soil physico-chemical properties on the microbial community composition (assessed as abundances of phospholipids fatty acids, PLFA). For this purpose, three land uses (forest, agricultural and abandoned agricultural) at four locations in SE Spain were selected. Multivariate analysis showed a substantial level of differentiation in microbial community structure according to land use. The microbial communities of forest soils were highly associated with soil organic matter content. However, we have not found any physical or chemical soil property capable of explaining the differences between agricultural and abandoned agricultural soils. Thus, it was suggested that the cessation of the perturbation caused by agriculture and shifts in vegetation may have led to changes in the microbial community structure. PLFAs indicative of fungi and ratio of fungal to bacterial PLFAs were higher in abandoned agricultural soils, whereas the relative abundance of bacteria was higher in agricultural soils. Actinomycetes were generally lower in abandoned agricultural soils, while the proportions of vesicular-arbuscular mycorrhyzal fungi were, as a general trend, higher in agricultural and abandoned agricultural soils than in forests. Total microbial biomass and richness increased as agricultural < abandoned agricultural < forest soils.
    Applied Soil Ecology 07/2009; 42(3):315-323. · 2.21 Impact Factor
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    ABSTRACT: We studied the sensibility of the near infrared spectra (NIR) of soils to the changes caused by land use, and we compared with the sensibility of different sets of physical, chemical and biological soil properties. For this purpose, we selected three land uses, constituted by forest, almond trees orchards, and orchards abandoned between 10 and 15 years previously to sampling. Sampling was carried out in four different locations from the province of Alicante (SE Spain). We used discriminant analysis (DA) using different sets of soil properties. The different sets tested in this study using DA were: (1) physical and chemical properties (organic carbon, total nitrogen, available phosphorus, pH, electrical conductivity, cation exchange capacity, aggregate stability, water holding capacity, and available Ca, Mg, K and Na), (2) biochemical properties (microbial biomass carbon, basal respiration and urease, phosphatase and beta-glucosidase activities), (3) phospholipids fatty acids (PLFAs), (4) physical, chemical and biochemical properties (all properties of the previous sets), and (5) the NIR spectra of soils (scores of the principal components). In general, all sets of properties were sensible to land use. This was observed in the DAs by the separation (more or less clear) of samples in groups defined by land use (irrespective of site). The worst results were obtained using soil physical and chemical properties. The combination of physical, chemical and biological properties enhanced the separation of samples in groups, indicating higher sensibility. It is accepted than combination of properties of different nature is more effective to evaluate the soil quality. The microbial community structure (PLFAs) was highly sensible to the land use, grouping correctly the 100% of the samples according with the land use. The NIR spectra were also sensitive to land use. The scores of the first 5 components, which explained 99.97% of the variance, grouped correctly the 85% of the soil samples by land use, but were unable to group correctly the 100% of the samples. Surprisingly, when the scarce variance presents in components 5 to 40 was also used, the 100% of the samples were grouped by land use, as it was observed with PLFAs. But PLFAs analysis is expensive and time-consuming (some weeks). In contrast, only some minutes are needed for the obtainment of the NIR spectra. Additionally, no chemicals are need, decreasing the costs. The NIR spectrum of a soil contains relevant information about physical, chemical and biochemical properties. NIR spectrum could be considered as an integrated vision of soil quality, and as consequence offers an integrated vision of perturbations. Thus, NIR spectroscopy could be used as tool to monitoring soil quality in large areas. Acknowledgements: Authors acknowledge to "Bancaja-UMH" for the financial support of the project "NIRPRO"
    04/2009;
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    ABSTRACT: The accumulation of heavy metals in soils from different sources (atmospheric deposition, agricultural practices, urban-industrial activities, etc.) is of a great environmental concern. In this sense, there is a consensus in the literature that the total heavy metals in soil are not a suitable tool for risk assessment regarding heavy metal mobility and bioavailability. Several approaches have been proposed to estimate this bioavailability but controversy exists to define an universal method. The bioavailability is influenced, apart from other properties like pH, organic matter, etc., by the mineral fraction and texture of a soil. However, the determination of these parameters, especially the mineral composition, is laborious, expensive, and time consuming. Thus, the objectives of this work are the estimation of the texture and mineral components of contrasting soils and the heavy metal uptake (Cu, Zn, Pb, Ni, Cr, Cd) by barley after sewage sludge application using NIR spectroscopy. A set of 70 contrasting soils from different parts of Spain were used for the analysis of the texture and mineral composition. The mineralogical characterization of soil samples was carried out by X-ray diffraction (XRD) using whole soil random powder, oriented clay on ceramic plates, and clay random powder. Chung method was used for semi-quantitative interpretation of X-ray diffraction patterns of soils, obtaining the percentage of Calcite (Ca), Quartz (Q), Albite (Ab), Potassium Feldspar (FK), phyllosilicates (PS). For the prediction of heavy metal uptake, the 70 soils were divided in two separate sets of 36 (experiment 1) and 34 (experiment 2) soils. The methodology for both experiments, separated in time, was the same. The soils were amended with the same dose of sewage sludge (15.71 g dry weight kg-1) and placed in pots. In these pots, a bioassay with barley, under greenhouse conditions, was carried out. Eight weeks after sowing, the plants were harvested. Roots were dried in an oven at 65°C for 2 days, and total heavy metals were determined. The soil samples (air-dried and ground to pass through 2-mm sieve) were placed in glass Petri-dishes, and scanned on reflectance mode from 12000 to 3800 cm-1. For these measurements, a Fourier-Transform near infrared (FT-NIR) spectrophotometer (MPA, Bruker Optik GmbH, Germany) was used. Partial least squares (PLS) regressions were performed to relate the spectral information with the studied parameters. For the mineral parameters and texture, and according to the RPD value, the following models were obtained: excellent for Ca (R2=90.33; RPD=3.24) and Ab (R2=86.03; RPD=2.70), very good (where quantitative predictions are possible) for silt (R2=77.61; RPD=2.13), sand (R2=75.46; RPD=2.03), Q (R2=75.72; RPD=2.04) and FK (R2=78.97; RPD=2.20), and fair models which may be used for assessment and correlation for clay (R2=68.19; RPD=1.78) and PS (R2=67.63; RPD=1.77). For the case of the estimation of the heavy metal uptake, and using the results obtained in the experiment 1, very good models were obtained for Pb (R2=80.75; RPD=2.31), fair, where only high and low values are distinguishable, Ni (R2=50.13; RPD=1.43) and Cd (R2=57.65; RPD=1.56), and poor for Cu (R2=21.94; RPD=1.15), Zn (R2=1.03; RPD=1.02) and Cr (R2=46.01; RPD=1.38). The models developed with the results obtained in the experiment 2 were classified as follows: excellent for Zn (R2=87.62; RPD=2.89) and Ni (R2=85.67; RPD=2.68), very good for Pb (R2=75.08; RPD=2.04) and Cd (R2=77.37; RPD=2.13), good for Cu (R2=72.54; RPD=1.94), and fair for Cr (R2=54.9; RPD=1.51). Although satisfactory results were found for Cu and Zn in the experiment 2 (surprisingly, after the bad results of the experiment 1), they seemed not to be useful, since they were influenced by just one high value, very different to the rest. However, this was not the case of the rest of studied metals, which seemed to have similar patterns in both experiments, with logical differences due to the different ranges, soils, etc. The results indicate that NIR spectroscopy can be a very useful tool to estimate some mineral components and texture of soils but further analyses including a higher number of samples should be performed. For the case of heavy metal uptake, and according to the low number of samples and the observed differences between experiments, it is just possible to conclude that, although it seems that NIR spectroscopy could estimate the phytoavailability of some metals, greater efforts must be done. Acknowledgements: Jose. M. Soriano-Disla gratefully acknowledges the Spanish Ministry of Innovation and Culture for a research fellowship (AP2005-0320).
    04/2009;
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    ABSTRACT: Near infrared (NIR) reflectance spectroscopy offers important advantages because is a non-destructive technique, the pre-treatments needed in samples are minimal, and the spectrum of the sample is obtained in less than 1 minute without the needs of chemical reagents. For these reasons, NIR is a fast and cost-effective method. Moreover, NIR allows the analysis of several constituents or parameters simultaneously from the same spectrum once it is obtained. For this, a needed steep is the development of soil spectral libraries (set of samples analysed and scanned) and calibrations (using multivariate techniques). The calibrations should contain the variability of the target site soils in which the calibration is to be used. Many times this premise is not easy to fulfil, especially in libraries recently developed. A classical way to solve this problem is through the repopulation of libraries and the subsequent recalibration of the models. In this work we studied the changes in the accuracy of the predictions as a consequence of the successive addition of samples to repopulation. In general, calibrations with high number of samples and high diversity are desired. But we hypothesized that calibrations with lower quantities of samples (lower size) will absorb more easily the spectral characteristics of the target site. Thus, we suspect that the size of the calibration (model) that will be repopulated could be important. For this reason we also studied this effect in the accuracy of predictions of the repopulated models. In this study we used those spectra of our library which contained data of soil Kjeldahl Nitrogen (NKj) content (near to 1500 samples). First, those spectra from the target site were removed from the spectral library. Then, different quantities of samples of the library were selected (representing the 5, 10, 25, 50, 75 and 100% of the total library). These samples were used to develop calibrations with different sizes (%) of samples. We used partial least squares regression, and leave-one-out cross validation as methods of calibration. Two methods were used to select the different quantities (size of models) of samples: (1) Based on Characteristics of Spectra (BCS), and (2) Based on NKj Values of Samples (BVS). Both methods tried to select representative samples. Each of the calibrations (containing the 5, 10, 25, 50, 75 or 100% of the total samples of the library) was repopulated with samples from the target site and then recalibrated (by leave-one-out cross validation). This procedure was sequential. In each step, 2 samples from the target site were added to the models, and then recalibrated. This process was repeated successively 10 times, being 20 the total number of samples added. A local model was also created with the 20 samples used for repopulation. The repopulated, non-repopulated and local calibrations were used to predict the NKj content in those samples from the target site not included in repopulations. For the measurement of the accuracy of the predictions, the r2, RMSEP and slopes were calculated comparing predicted with analysed NKj values. This scheme was repeated for each of the four target sites studied. In general, scarce differences can be found between results obtained with BCS and BVS models. We observed that the repopulation of models increased the r2 of the predictions in sites 1 and 3. The repopulation caused scarce changes of the r2 of the predictions in sites 2 and 4, maybe due to the high initial values (using non-repopulated models r2 >0.90). As consequence of repopulation, the RMSEP decreased in all the sites except in site 2, where a very low RMESP was obtained before the repopulation (0.4 g×kg-1). The slopes trended to approximate to 1, but this value was reached only in site 4 and after the repopulation with 20 samples. In sites 3 and 4, accurate predictions were obtained using the local models. Predictions obtained with models using similar size of samples (similar %) were averaged with the aim to describe the main patterns. The r2 of predictions obtained with models of higher size were not more accurate than those obtained with models of lower size. After repopulation, the RMSEP of predictions using models with lower sizes (5, 10 and 25% of samples of the library) were lower than RMSEP obtained with higher sizes (75 and 100%), indicating that small models can easily integrate the variability of the soils from the target site. The results suggest that calibrations of small size could be repopulated and "converted" in local calibrations. According to this, we can focus most of the efforts in the obtainment of highly accurate analytical values in a reduced set of samples (including some samples from the target sites). The patterns observed here are in opposition with the idea of global models. These results could encourage the expansion of this technique, because very large data based seems not to be needed. Future studies with very different samples will help to confirm the robustness of the patterns observed. Authors acknowledge to "Bancaja-UMH" for the financial support of the project "NIRPROS".
    04/2009;
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    ABSTRACT: The use of treated wastewater for the irrigation of agricultural soils is an alternative to utilizing better-quality water, especially in semiarid regions where water shortage is a very serious problem. However, this practise can modify the soil equilibrium and affect its quality. In this work two soil quality indices (models) are used to evaluate the effects of long-term irrigation with treated wastewater in soil. The models were developed studying different soil properties in undisturbed forest soils in SE Spain, and the relationships between soil parameters were established using multiple linear regressions. Model 1, that explained 92% of the variance in soil organic carbon (SOC) showed that the SOC can be calculated by the linear combination of 6 physical, chemical and biochemical properties (acid phosphatase, water holding capacity (WHC), electrical conductivity (EC), available phosphorus (P), cation exchange capacity (CEC) and aggregate stability (AS)). Model 2 explains 89% of the SOC variance, which can be calculated by means of 7 chemical and biochemical properties (urease, phosphatase, and
    01/2009;
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    Efectos de los incendios forestales sobre los suelos en España. El estado de la cuestión visto por los científicos españoles, 01/2009: chapter 3.4: pages 185-217; Càtedra de Divulgació de la Ciència. Universitat de Valencia., ISBN: 978-84-370-7653-9
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    Applied Soil Ecology 01/2009; 42:315-323. · 2.21 Impact Factor
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    ABSTRACT: Soil microbiology is crucial for soil system functioning. Fire can affect soil microbes directly through heating and indirectly by modifying soil properties. Microbes will also be affected by post-fire environmental factors and the reestablishment of vegetation. The most important factor affecting soil microbes seems to be the burn severity, which is controlled by such factors as fire intensity, duration, and soil properties which normally causes a decrease in the numbers of microbes. The temperatures reached in the topsoil are often sufficient to affect soil microorganisms and other soil properties related to the post-fire microbial recolonization. In extreme cases, the topsoil can undergo complete sterilization. Fungi seem to be more sensitive to heating than bacteria and actinomycetes, and a higher impact under wet soil conditions has been reported. In the case of fungi that form arbuscular mycorrhizas, almost all the studies show a negative influence resulting in a reduced number of propagules. An important factor is the presence of fungal resistant structures, such as sclerotia, from which new mycelia originate to colonize new plants. The activity of soil microorganisms also decreases due to changes in the quality of organic matter. In the short-term, mainly due to the increase in soluble carbon and nutrients in affected soils, an increase in heterotrophic bacteria population basal respiration is commonly observed. After depletion of the easily mineralized organic compounds, this initial increase in microbial basal respiration is generally followed by a decrease as the remaining carbon and nitrogen forms are more
    Fire Effects on Soils and Restoration Strategies, 01/2009: chapter 5: pages 133-175; Science Publishers, Inc.., ISBN: 978-1-57808-526-2
  • Dynamic Soil, Dynamic Plant. 01/2009; 3:132-135.