Molowny-Horas R., Basnou C., Pino J. (2015) A multivariate fractional regression approach to modeling land use and cover dynamics in a Mediterranean landscape. Computers, Environment and Urban Systems. 54: 47-55.LinkDoi: 10.1016/j.compenvurbsys.2015.06.001
The way landscapes change in time reveal a great deal of information about the interplay between the forces of nature and the impact of human-driven changes in a Mediterranean landscape. To understand the dynamics behind the process of polygon fragmentation in land use and cover vector maps we illustrate the potential of a novel regression methodology to cope with multivariate fractional data.An overlay of two vector-based land cover maps separated by a time interval of several years (1956 and 1993) show polygons that have become fragmented. Those fragments thus form a multivariate fractional bounded data set. An extension of the Papke and Wooldridge (1996) fractional regression estimation to the case of multivariate response variables has been subsequently developed to study the processes of polygon fragmentation between the two land use and cover maps.The methodology has been applied to a representative set of vector maps from the Barcelona province, Spain. Several explanatory variables have been used, among them the land cover type of the most important adjacent 1956 polygon. The results of our study indicate that the dynamics of fragmentation are determined not only by geographical and environmental variables but also by the neighboring landscape. We discuss its potential use when employed with techniques of landscape modeling. © 2015 Elsevier Ltd.
Marcer A., Saez L., Molowny-Horas R., Pons X., Pino J. (2013) Using species distribution modelling to disentangle realised versus potential distributions for rare species conservation. Biological Conservation. 166: 221-230.LinkDoi: 10.1016/j.biocon.2013.07.001
Range maps provide important information in species conservation management, specially in the case of rare species of conservation interest. For the vast majority of cases, this information can only be estimated by means of species distribution modelling. When absence data is unavailable, modelled distribution maps represent the spatial variation of the degree of suitability for the species rather than their realised distribution. Although discerning potentially suitable areas for a given species is an important asset in conservation, it is necessary to estimate current distributions in order to preserve current populations. This work explores the use of species distribution modelling (Maxent) for species of conservation interest when their Extent of Occurrence (EOO) is well-known and there is quality occurrence data. In this case, derived binary maps of potentially suitable areas can be obtained and used to assess the conservation and protection status of a given species in combination with the EOO and existing protected area networks. Seven species, which are rare and endemic to the Western Mediterranean, have been used as an example. Valuable information for conservation assessment such as potentially suitable areas, EOO, Areas of Occupancy (AOO) and degree of protection is provided for this set of species. In addition, the existing informal view that among experts these species have range sizes much smaller than their potentially suitable area is confirmed. This could probably be attributed to important but currently unknown predictor variables and to historical phylogeographic factors. © 2013 Elsevier Ltd.
Pino J., Font X., de Cáceres M., Molowny-Horas R. (2009) Floristic homogenization by native ruderal and alien plants in north-east Spain: The effect of environmental differences on a regional scale. Global Ecology and Biogeography. 18: 563-574.LinkDoi: 10.1111/j.1466-8238.2009.00458.x
Aim: To evaluate the relative potential contribution of native ruderals and aliens to plant homogenization at a regional scale, after taking into account the effect of diverse environmental distances. Location: Catalonia (north-east Spain) Methods: We have used the flora module of the BDBC project (Catalonian Database of Biodiversity), which provides information on plant species distribution per 10 × 10 km Universal Transverse Mercator (UTM) cell. Pairwise floristic similarities of: (1) total, (2) native non-ruderal, (3) native ruderal, and (4) alien vascular plant species have been calculated for a particularly well-sampled subset of UTM cells, using a modified version of the Simpson index. These similarities have been compared per UTM pair using Mantel tests, before and after considering their relative association with geographical, climatic and landscape distances from linear regression models. The floristic similarity of both total and native non-ruderal species was also correlated with the proportion of alien and native ruderal species after discounting the effects of environmental distances. Results: The proportion of variance explained by environmental correlates was highest for the floristic similarity of native non-ruderal plants and lowest for that of aliens. In all plant groups, climatic distance was the main significant variable of species similarity. Geographical distance was only significant for total and native non-ruderal species and was of secondary importance in both cases. Landscape distance was not significant in any case. Similarities among both aliens and native ruderals were significantly higher than among native non-ruderals, but these differences disappeared after removing the effect of environmental distances. Main conclusions: Species similarity between sites may depend on differences in environmental factors other than geographical distance. This has to be taken into account when exploring the implications for biotic homogenization. In the case of Catalonian flora, the potentially homogenizing effect of native ruderal and alien species seems to be associated with their lower dependence on geographical distance and climatic factors compared with those of native, non-ruderal species. © 2009 Blackwell Publishing Ltd.
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