Carnicer J., Coll M., Pons X., Ninyerola M., Vayreda J., Penuelas J. (2014) Large-scale recruitment limitation in Mediterranean pines: The role of Quercus ilex and forest successional advance as key regional drivers. Global Ecology and Biogeography. 23: 371-384.EnllaçDoi: 10.1111/geb.12111
Aim: Large-scale patterns of limitations in tree recruitment remain poorly described in the Mediterranean Basin, and this information is required to assess the impacts of global warming on forests. Here, we unveil the existence of opposite trends of recruitment limitation between the dominant genera Quercus and Pinus on a large scale and identify the key ecological drivers of these diverging trends. Location: Spain Methods: We gathered data from the Spanish National Forest inventory to assess recruitment trends for the dominant species (Pinus halepensis, Pinus pinea, Pinus pinaster, Pinus nigra, Pinus sylvestris, Pinus uncinata, Quercus suber, Quercus ilex, Quercus petraea, Quercus robur, Quercus faginea and Quercus pyrenaica). We assessed the direct and indirect drivers of recruitment by applying Bayesian structural equation modelling techniques. Results: Severe limitations in recruitment were observed across extensive areas for all Pinus species studied, with recruitment failure affecting 54-71% of the surveyed plots. In striking contrast, Quercus species expanded into 41% of the plots surveyed compared to only 10% for Pinus and had a lower local recruitment failure (29% of Quercus localities compared to 63% for Pinus species). Bayesian structural equation models highlighted the key role of the presence of Q.ilex saplings and the increase in the basal area of Q.ilex in limiting recruitment in five Pinus species. The recruitment of P.sylvestris and P.nigra showed the most negative trends and was negatively associated with the impacts of fire. Main conclusions: This study identified Q.ilex, the most widespread species in this area, as a key driver of recruitment shifts on a large scale, negatively affecting most pine species with the advance of forest succession. These results highlight that the future expansion/contraction of Q.ilex stands with ongoing climate change will be a key process indirectly controlling the demographic responses of Pinus species in the Mediterranean Basin. © 2013 John Wiley & Sons Ltd.
Maso J., Pons X., Zabala A. (2014) Building the World Wide Hypermap (WWH) with a RESTful architecture. International Journal of Digital Earth. 7: 175-193.EnllaçDoi: 10.1080/17538947.2012.669414
The hypermap concept was introduced in 1992 as a way to hyperlink geospatial features to text, multimedia or other geospatial features. Since then, the concept has been used in several applications, although it has been found to have some limitations. On the other hand, Spatial Data Infrastructures (SDIs) adopt diverse and heterogeneous service oriented architectures (SOAs). They are developed by different standard bodies and are generally disconnected from mass market web solutions. This work expands the hypermap concept to overcome its limitations and harmonise it with geospatial resource oriented architecture (ROA), connecting it to the semantic web and generalising it to the World Wide Hypermap (WWH) as a tool for building a single 'Digital Earth'. Global identifiers, dynamic links, link purposes and resource management capabilities are introduced as a solution that orchestrates data, metadata and data access services in a homogeneous way. This is achieved by providing a set of rules using the current Internet paradigm formalised in the REpresentational State Transfer (REST) architecture and combining it with existing Open Geospatial Consortium (OGC) and International Organization for Standardization (ISO) standards. A reference implementation is also presented and the strategies needed to implement the WWH, which mainly consist in a set of additions to current Geographic Information System (GIS) products and a RESTful server that mediates between the Internet and the local GIS applications. © 2012 Taylor & Francis.
Pons X., Pesquer L., Cristobal J., Gonzalez-Guerrero O. (2014) Automatic and improved radiometric correction of landsat imageryusing reference values from MODIS surface reflectance images. International Journal of Applied Earth Observation and Geoinformation. 33: 243-254.EnllaçDoi: 10.1016/j.jag.2014.06.002
Radiometric correction is a prerequisite for generating high-quality scientific data, making it possibleto discriminate between product artefacts and real changes in Earth processes as well as accuratelyproduce land cover maps and detect changes. This work contributes to the automatic generation of surfacereflectance products for Landsat satellite series. Surface reflectances are generated by a new approachdeveloped from a previous simplified radiometric (atmospheric + topographic) correction model. Theproposed model keeps the core of the old model (incidence angles and cast-shadows through a digitalelevation model [DEM], Earth-Sun distance, etc.) and adds new characteristics to enhance and automatizeground reflectance retrieval. The new model includes the following new features: (1) A fitting model basedon reference values from pseudoinvariant areas that have been automatically extracted from existingreflectance products (Terra MODIS MOD09GA) that were selected also automatically by applying qualitycriteria that include a geostatistical pattern model. This guarantees the consistency of the internal andexternal series, making it unnecessary to provide extra atmospheric data for the acquisition date and time,dark objects or dense vegetation. (2) A spatial model for atmospheric optical depth that uses detailedDEM and MODTRAN simulations. (3) It is designed so that large time-series of images can be processedautomatically to produce consistent Landsat surface reflectance time-series. (4) The approach can handlemost images, acquired now or in the past, regardless of the processing system, with the exception ofthose with extremely high cloud coverage. The new methodology has been successfully applied to aseries of near 300 images of the same area including MSS, TM and ETM+ imagery as well as to differentformats and processing systems (LPGS and NLAPS from the USGS; CEOS from ESA) for different degreesof cloud coverage (up to 60%) and SLC-off. Reflectance products have been validated with some exampleapplications: time series robustness (for a pixel in a pseudoinvariant area, deviations are only 1.04% onaverage along the series), spectral signatures generation (visually coherent with the MODIS ones, butmore similar between dates), and classification (up to 4 percent points better than those obtained withthe original manual method or the CDR products). In conclusion, this new approach, that could also beapplied to other sensors with similar band configurations, offers a fully automatic and reasonably goodprocedure for the new era of long time-series of spatially detailed global remote sensing data. © 2014 The Authors.
Regos A., Dominguez J., Gil-Tena A., Brotons L., Ninyerola M., Pons X. (2014) Rural abandoned landscapes and bird assemblages: winners and losers in the rewilding of a marginal mountain area (NW Spain). Regional Environmental Change. : 0-0.EnllaçDoi: 10.1007/s10113-014-0740-7
In many regions of Europe, large-scale socio-economic changes have led to the abandonment of rural activities and a gradual takeover of natural vegetation. It is important to assess the relative positive and negative effects of land abandonment on particular areas where the low-intensity farming is no longer socially or economically viable in order to quantify the potential conservation costs and benefits of a rewilding as a land-use management policy. During the period 2000–2010, we studied the land-use/land-cover changes in an abandoned mountain landscape (Galicia, NW Spain) and evaluated the effects on breeding bird occurrence and distribution. For this purpose, we analysed remotely sensed data-derived maps in combination with data obtained from bird censuses carried out in 2000 and 2010 at both landscape and census plot scale. The results revealed a gradient of change from bare ground and open shrubland to closed shrubland and woodland. Thirteen shrubland and forest bird species showed a significant increase (including species of conservation concern such as Turtle Dove, Dartford Warbler and Western Bonelli’s Warbler), while four ecotone and open-habitat species (e.g. Red-backed Shrike) showed a significant negative trend. In conclusion, rewilding appears to have overall positive effects on biodiversity and should be considered by policy makers as alternative land-use strategy in marginal mountain areas, particularly if they have been historically affected by wildfires. Fire management aimed at favouring the creation of small burned areas in progressively closed landscapes derived from rewilding may be a complementary alternative to maintain open habitats in these areas.
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