Tree rings are an important proxy to understand the natural drivers of climate variability in the Mediterranean Basin and hence to improve future climate scenarios in a vulnerable region. Here, we compile 316 tree-ring width series from 11 conifer sites in the western Iberian Range. We apply a new standardization method based on the trunk basal area instead of the tree cambial age to develop a regional chronology which preserves high- to low-frequency variability. A new reconstruction for the 1602–2012 period correlates at −0.78 with observational September temperatures with a cumulative mean of the 21 previous months over the 1945–2012 calibration period. The new IR2Tmax reconstruction is spatially representative for the Iberian Peninsula and captures the full range of past Iberian Range temperature variability. Reconstructed long-term temperature variations match reasonably well with solar irradiance changes since warm and cold phases correspond with high and low solar activity, respectively. In addition, some annual temperature downturns coincide with volcanic eruptions with a 3-year lag.

Daily precipitation datasets are usually large, bulky and hard to handle, but they are of key importance in many environmental studies. We developed a tool to create custom datasets from observed daily precipitation records. Reference values (RV) are computed for each day and location using multivariate logistic regression with altitude, latitude and longitude as covariates. The operations were compiled in an Open Source R package called reddPrec. The reddPrec package consists of a set of functions used to: i) apply a comprehensive quality control over original daily precipitation datasets, flagging suspect data based on five predefined criteria; ii) fill missing values in original data series by estimating precipitation values using the 10 nearest observations for each day; and iii) create new series and gridded datasets in locations where no data were recorded.

In Mediterranean areas with limited availability of water, an accurate knowledge of growth response to hydrological variables could contribute to improving management and stability of forest resources. The main goal of this study is to assess the temporal dynamic of soil moisture to better understand the water-growth relationship of Pinus halepensis forests in semiarid areas. Firstly, dendrochronological samples were extracted and the widths of annual tree rings were measured to compute basal area increments (BAI). Secondly, soil moisture was estimated over 20 hydrological years (1992–2012) by means of the HYDROBAL ecohydrological model. Finally, the tree growth was linked, to mean monthly and seasonal temperature, precipitation and soil moisture. Results depict the effect of soil moisture on growth (BAI) and explain 69–73% of the variance in semiarid forests, but only 51% in the subhumid forests. This highlights the fact that that soil moisture is a suitable and promising variable to explain growth variations of afforested Pinus halepensis in semiarid conditions and useful for guiding adaptation plans to respond pro-actively to water-related global challenges.

Climate predictions for the Mediterranean Basin include increased temperatures, decreased precipitation, and increased frequency of extreme climatic events (ECE). These conditions are associated with decreased growth of trees and their increased vulnerability to pests and diseases. The anatomy of tree rings is responsive to these environmental conditions. Quantitatively, the width of a tree ring is largely determined by the rate and duration of cell division by the vascular cambium. In the Mediterranean climate, cambial cell division may occur throughout almost the entire year. Alternatively, cell division may stop during relatively cool and dry winters, only to resume in the same year with milder temperatures and increased availability of water...

Wood is the main terrestrial biotic reservoir for long-term carbon sequestration. This study presents high-resolution cellular based measurements of wood formation dynamics in different coniferous forest sites all over the northern Hemisphere, with a deeper analysis in northeastern France.  We show that stem woody biomass production lags behind stem-girth increase by over 1 month. Northern Hemisphere forests shows similar time lags in boreal, temperate, subalpine and Mediterranean climates. The results show that these two growth processes exhibit differential sensitivities to local environmental conditions. Results suggest that forecasted changes in the annual cycle of climatic factors may shift the phase timing of stem size increase and woody biomass production in the future.

Wood formation in European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.) was intra-annually monitored to examine plastic responses of the xylem phenology according to altitude in one of the southernmost areas of their distribution range, i.e., in the Moncayo Natural Park, Spain. The monitoring was done from 2011 to 2013 at 1180 and 1580 m a.s.l., corresponding to the lower and upper limits of European beech forest in this region. Microcores containing phloem, cambium and xylem were collected biweekly from twenty-four trees from the beginning of March to the end of November to assess the different phases of wood formation...

In this study, the spatial patterns of relative air humidity and its relation to urban, geographical and meteorological factors in the city of Zaragoza (Spain) are discussed. We created a relative humidity database by means of 32 urban transects. Data were taken on different days and with different weather types. This data set was used to map the mean spatial distribution of urban dry island (UDI). Using stepwise multiple regression analysis and Landsat ETM+ images the relationships between mean UDI and the main geographic-urban factors: topography, land cover, and surface reflectivity, have been analyzed. Different spatial patterns of UDI were determined using Principal Component Analysis (PCA) (Varimax rotation). The three components extracted accounted for 91% of the total variance. PC1 accounted for the most general patterns (similar to mean UDI); PC2 showed a shift of dry areas to the SE and PC3 a shift to NW. Using data on wind direction in Zaragoza, we have found that the displacement of dry areas to the SE (PC 2) was greater during NW winds while the shift to the NW (PC 3) was produced mainly by SE winds.

Droughts are a recurrent phenomenon in the Mediterranean basin with negative consequences for society, economic activities and natural systems. Through this study we reconstruct 318 years of the Standard Precipitation Index (SPI). According to this drought index 7 substantially dry and 5 wet periods are identified since the late 17th century considering 1.76 standard deviations. Besides these, 36 drought and 28 pluvial years were identified. Some of these years, such as 1725, 1741, 1803 and 1879 are also revealed in other drought reconstructions in Romania and Turkey, suggesting coherent larger scale synoptic patterns drove these extreme deviations.