http://http://dspace.unitus.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Wed, 22 May 2013 09:08:30 GMT 2013-05-22T09:08:30Z http://hdl.handle.net/2067/2134 Title: LaDy: software for assessing local landscape diversity profiles of raster land cover maps using geographic windows Authors: Ricotta, Carlo; Corona, Piermaria; Marchetti, Marco; Chirici, Gherardo; Innamorati, Stefano Abstract: Landscape ecology starts from the assumption that diversity and spatial arrangement of ecosystem mosaics have ecological implications and tries to understand the interactions between diversity and structure of large spatially heterogeneous areas and their ecological functions. These assumptions imply effective use of earth observation techniques and geographic information systems, enabling a global view of the landscape mosaics. In this paper, a software, LaDy (Landscape Diversity Software), for computing Re´nyi’s local landscape diversity profile on raster land cover maps is presented. LaDy is based on the use of Merchant’s adaptive geographic window, which is designed to operate on a neighborhood of patches instead of a fixed rectangular neighborhood of pixels (the conventional approach in image analysis). Description: L'articolo è disponibile sul sito dell'editore www.elsevier.com Tue, 31 Dec 2002 23:00:00 GMT http://hdl.handle.net/2067/2134 2002-12-31T23:00:00Z http://hdl.handle.net/2067/2131 Title: On parametric fragmentation measures Authors: Ricotta, Carlo; Corona, Piermaria; Marchetti, Marco; Chirici, Gherardo Abstract: In the landscape ecological literature, a number of measures have been proposed for quantifying landscape fragmentation based on distinct objectives and motivations. However, none seems to be generally preferred. The main reason for this disagreement is that, from a statistical viewpoint, by mapping fragmentation into a single scalar, information is necessarily lost and no ideal function is able to uniquely characterize all aspects of landscape fragmentation. A more complete summarization of fragmentation is possible if, instead of one single index, a parametric index family is applied whose members have varying sensitivities to the presence of large and small landscape patches. While traditional indices supply point descriptions of fragmentation, according to a parametric fragmentation family Ha, there is a continuum of possible fragmentation measures that differ in their sensitivity to the presence of large and small patches as a function of the scaling parameter a. Therefore, changing a allows for vector description of fragmentation. The purpose of this paper is to introduce a parametric generalization of Shannon’s entropy to summarize landscape fragmentation. A small set of artificial landscapes is used to clarify our proposal Description: L'articolo è disponibile sul sito dell'editore www.springerlink.com Sat, 31 Dec 2005 23:00:00 GMT http://hdl.handle.net/2067/2131 2005-12-31T23:00:00Z http://hdl.handle.net/2067/2121 Title: Beware of contagion! Authors: Ricotta, Carlo; Corona, Piermaria; Marchetti, Marco Abstract: Landscape ecology starts from the assumption that diversity and spatial arrangement of ecosystem mosaics has ecological implications and tries to understand the interactions between diversity and structure of large spatially heterogeneous areas and its ecological functions. This approach implies effective use of earth observation techniques and geographic information systems, enabling a global view of the landscape mosaics. Consequently, a large number of indices has been used to quantify the structure of categorical maps as a surrogate of actual landscapes and correlate them to ecological processes. In particular, the entropy-based contagion index has been extensively used to summarize the amount of clumping or fragmentation of patches on raster categorical maps. However, despite its widespread application, the contagion index is very dependent on pixel resolution. This effect may render it inadequate as a meaningful measure of landscape structure. To overcome this major shortcoming, in this short note we propose to quantify pixel adjacency with a bivariate summary statistics that is not adversely influenced by pixel resolution. Description: L'articolo è disponibile sul sito dell'editore www.elsevier.com Tue, 31 Dec 2002 23:00:00 GMT http://hdl.handle.net/2067/2121 2002-12-31T23:00:00Z