Forme di vegetazione forestale del distretto reatino (regione Lazio)
Author(s)
Agrillo, Emiliano
Date Issued
February 23, 2010
Type
Doctoral Thesis
Abstract
This work deals with mapping of forest vegetation in the province of Rieti (Central Italy-Latium region), an area of 2748 sq. Km, which encompasses a district of Central Appennines.
Satellite Landsat images have been processed producing a first unsupervised map, a survey based on fieldwork verifying floristic structure and geographic limits (GPS sampling) of forest patches in the landscape mosaic has been carried out. A Supervised classification has therefore been obtained integrating the results of the coenological study in field. Coenology has been outlined describing forest vegetation types on the basis of dominant and codominant species in the plots, eventually connecting this data with Corine Biotopes System Classification and available Phytosociological nomenclature. Fifteen forest types have been recorded and mapped. Relations with existing nomenclature, INFC Classification, CORINE Biotopes, EUNIS, EU Forest Type Classification and Phytosociological-syntaxonomic analysis, has been quoted in order to obtain a satisfactory overview at the European scale.
This material has been submitted to quantitative phytogeographic analysis. Descriptive statistics have been applied to a matrix of binary data (presence/absence) of operational geographic units (OGU) of a geographic grid. In these quadrates of 4 x 4 Km, occurrence of a selected amount of emblematic trees has been recorded along with several environmental factors (elevation, slope, aspect, temperature and precipitations, nutrient availability and bed-rock permeability).
A geostatistical approach (Kriging, a set of linear regression routines used to interpolate data points) was used in order to obtain isolines of the parameters T and P. On this basis, a surface geostatistical analysis (Cell Statistics) produced mean values for annual T and P for each cell of the grid all across the study area.
A Digital Elevation Model (DEM, 20 m resolution) has been used to produce average values within the quadrates for elevation, slope and aspect.
An index of “nutrient availability” has been used to quantify the pedological diversity throughout the region. For each cell, a value of average potential soil fertility, based on degrees adimensional semiquantitative scale. An index of “permeability of the parent material” has been used to quantify changes in soil water drainage due to the lithological diversity throughout the region. For each cell, a value of average water availability, dealing with porosity and permeability characteristics of the different parent material, based on degrees adimensional semiquantitative scale.
Multivariate analysis has been applied to same dataset in order to obtain graphic overview of the relationships between species and environmental parameters.
From Descriptive Statistical and Multivariate analysis significant parameters have been identified able to outline predictive maps of the potential distribution according to these parameters.
The whole data set (the matrix of the figures of the significant environmental parameters for each cell) has been analysed comparing the statistical distribution of the cells in which the selected species are recorded.
The parameterization produced a simulated “potential range”, which is the core of the probabilistic approach of this study. It identifies a range sometimes larger than the one occupied by the species today. In order to assess the reliability of this prediction a geostatistical analysis has been performed using “the Kriging method”.
This approach allows informing important characteristic from the geographical structure of the predicted potential ranges. In some cases (see T. baccata) the locations of some existing stands lie outside the potential area. This suggests ongoing events of range restriction, range pulsation enlightening the local modes in the process of relictuality.
On the contrary in the case of P. halepensis the present-day sites suggesting the persistents in the same area of favourable sites with no apparent legacy of range pulsation.
The map of the forest vegetation in the district of the territories of Rieti, is per se an important goal in the knowledge of local forest diversity which is innovative due to lack previous documentation. This information is an essential value in the assessment of biogeographically consistent method of management as far as nature conservation is concern.
Additional information
Dottorato di ricerca in Scienze e tecnologie per la gestione forestale e ambientale
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