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Ruiz-Yanetti S.,University of Alicante | Chirino E.,Mediterranean Center for Environmental Studies Foundation | Chirino E.,University of Alicante | Bellot J.,University of Alicante
Journal of Arid Environments

In dryland areas, knowledge of plant water requirements and water use strategies of species are essential for use in afforestation, to ensure the establishment of seedlings in the first summer after planting. In this context, we used minilysimeters to estimate the daily whole-plant transpiration requirements in seedlings of Pinus halepensis, Pistacia lentiscus and Quercus coccifera, which are frequently used in afforestation. This estimate was calculated according to the following two conditions: high-soil moisture and a drought period. The results in both conditions indicated the highest daily rate (0.90-1.33 L m-2 day-1) for Q. coccifera, P. lentiscus was moderate (0.50-0.75 L m-2 day-1) and P. halepensis showed the lowest rate (0.37-0.44 L m-2 day-1). Species response under drought conditions was in accordance with their drought-avoidance strategy. P. halepensis and P. lentiscus displayed a water-saver mechanism, while Q. coccifera exhibited a water-spender mechanism. Our results show that the use of minilysimeters is a suitable method to determine whole-seedling transpiration rate and to accurately estimate the water requirements of species used for afforestation in dryland areas. © 2015 Elsevier Ltd. Source

Mayor A.G.,Wageningen University | Valdecantos A.,Mediterranean Center for Environmental Studies Foundation | Vallejo V.R.,University of Barcelona | Keizer J.J.,University of Aveiro | And 5 more authors.
Science of the Total Environment

Since the mid of the last century, fire recurrence has increased in the Iberian Peninsula and in the overall Mediterranean basin due to changes in land use and climate. The warmer and drier climate projected for this region will further increase the risk of wildfire occurrence and recurrence. Although the impact of wildfires on soil nutrient content in this region has been extensively studied, still few works have assessed this impact on the basis of fire recurrence. This study assesses the changes in soil organic C and nutrient status of mineral soils in two Southern European areas, Várzea (Northern Portugal) and Valencia (Eastern Spain), affected by different levels of fire recurrence and where short fire intervals have promoted a transition from pine woodlands to shrublands. At the short-term (<. 1. year), the amount of soil organic matter was higher in burned than in unburned soils while its quality (represented as labile to total organic matter) was actually lower. In any case, total and labile soil organic matter showed decreasing trends with increasing fire recurrence (one to four fires). At the long-term (> 5. years), a decline in overall soil fertility with fire recurrence was also observed, with a drop between pine woodlands (one fire) and shrublands (two and three fires), particularly in the soil microsites between shrubs. Our results suggest that the current trend of increasing fire recurrence in Southern Europe may result in losses or alterations of soil organic matter, particularly when fire promotes a transition from pine woodland to shrubland. The results also point to labile organic matter fractions in the intershrub spaces as potential early warning indicators for shifts in soil fertility in response to fire recurrence. © 2015. Source

Chirino E.,University of Alicante | Chirino E.,Forest Restoration Group | Vilagrosa A.,University of Alicante | Vilagrosa A.,Mediterranean Center for Environmental Studies Foundation | And 2 more authors.
Plant and Soil

In dryland ecosystems, post-transplant water stress produces high seedling mortality after the first summer following outplanting. Our aim was to assess the effects of clay and hydrogel, both on the water holding capacity of the growing media and on various morphological and physiological characteristics of Quercus suber seedlings in the nursery and, subsequently, during the first 2 years in the field. Quercus suber L. seedlings were grown in four types of growing media: CS (Control growing media, standard mixture of limed peat and coconut peat, 1:1 v/v ratio), SC-10 (CS mixed with sepiolite clay at 10% v/v) and HS (CS mixed with hydrogel Stockosorb® K-400 at two doses, 0.7 and 1.5% w/w). HS-1. 5 showed the best results, increasing the water holding capacity of the root plug, improving seedling water status and increasing seedling survival in the field. SC-10 showed an intermediate effect on seedling response in the field. Mixing hydrogel with a peat-based growing medium to form root plugs is a suitable technique for cultivating species to be planted in areas with a strong water deficit. This technique reduces post-transplant water stress in seedlings during their first months in the field and contributes to improve forest-restoration methods in dryland ecosystems. © 2011 Springer Science+Business Media B.V. Source

Palau J.L.,Mediterranean Center for Environmental Studies Foundation | Rovira F.,Mediterranean Center for Environmental Studies Foundation
Journal of Atmospheric and Oceanic Technology

Environmental measurements often show unsteady variability and background red noise (stochastic component) superimposed on persistent trivial daily, seasonal, and annual variability. In addition to this, environmental time series often present gaps due to a myriad of possible factors, such as malfunction of the sensors, connection loss, etc. As a result, interpreting and identifying periodicities in this type of time series by means of spectral analysis tools, like the Fourier transform, are difficult and lack precision. To overcome these difficulties, a methodology is proposed in the first part of this paper that integrates statistical tools (iterative Student's t test), parametric reconstruction, and spectral analysis (Lomb periodogram and wavelets). In the second part of the paper, this methodology is tested (i) in the high-frequency part of the spectrum of two (well known) synthetic time series and (ii) to identify nontrivial (e.g., daily cycles) high-frequency periodicities (linked to some mesometeorological processes) in three tropospheric ozone time series recorded by the Valencia regional air quality monitoring network (on the Mediterranean side of Spain) during a 14-yr period. This methodology can determine statistically significant, seasonally dependent recurrences in the highfrequency variability (<15 days) observed in ozone time series measured in a Mediterranean region of Spain under high noise-to-signal ratios. © 2012 American Meteorological Society. Source

Castell-Balaguer N.,Mediterranean Center for Environmental Studies Foundation | Castell-Balaguer N.,Norwegian Institute For Air Research | Tellez L.,Mediterranean Center for Environmental Studies Foundation | Mantilla E.,Mediterranean Center for Environmental Studies Foundation
Environmental Science and Pollution Research

Introduction: The Turia river basin, located in the east of the Iberian Peninsula, drains into the Mediterranean Sea near the city of Valencia (population, 814,208). The predominance of sea-breeze fluxes favours the inland transport of pollutants from the city up the basin where ozone concentrations exceeding the threshold for protection of human health are systematically recorded during the summer months. Methods: This work analyses the variability in ozone levels by examining their spatial and temporal distribution in a Mediterranean river basin downwind from a city within the period 2005-2008. Orographic determinants and atmospheric fluxes induce strong variations in ozone measurements, even on relatively close locations. Conclusions: Results show a different behaviour of the monthly means and the daily cycles depending on the season of the year and the measuring environment, with summer/winter ratios ranging from 2. 4 in cities to 1. 6 inland, and mean values always higher in the interior of the basin. Daily cycles show significant summer/winter differences related to the predominant situations of anticyclonic stability in winter, which limit ventilation, and the predominant breeze circulations in summer. Results also show a "weekend effect" at urban and medium-distance stations. At the most inland station, the weekend/weekday behaviour differs according to the season of the year; weekend ozone levels are higher in spring, autumn and winter, and lower in summer, coinciding with the predominance of local wind cycles that favour air mass penetration inland from the coast. © 2012 Springer-Verlag. Source

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