Marks E.A.N., Molowny-Horas R., Domene X. (2015) Investigating the Use of Multi-Gaussian Nonlinear Regressions to Separate Collembolan Size Classes for Soil Quality Assessment. Water, Air, and Soil Pollution. 226: 0-0.EnllaçDoi: 10.1007/s11270-015-2503-6
Previous studies with bioindicator organisms have used somatic length distributions, i.e., population structure, to understand the effects of management, environment, or a potential contaminant on populations. We describe a statistical approach to separate somatic length classes of Folsomia candida juveniles as an endpoint for the assessment of changes in population structure. Reproduction-survival bioassays were carried out with five different biochars applied at increasing concentrations. Multi-Gaussian models parameterized juvenile size class cohorts, and the biomass of each size class cohort was estimated. Population structure was modified by both material type as well as concentration. Both biomass and population structure were sensitive to effects not reflected in juvenile number, the classic endpoint. Treatments with more size classes and larger individuals were taken to represent favorable conditions, and less size classes and smaller individuals indicated less favorable conditions. This extension of the standardized test provided additional information about the demography of the population. © 2015 Springer International Publishing Switzerland.
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.EnllaçDoi: 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.
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