Geostatistical analisys on the relationship between vegetation pattern and human impact

Abstract

The purpose of this work is to evaluate the vegetation pattern of a mediterranean landscape, analyzed through the shape of the patches that constitute it, and its relationship with alterations introduced by land use and human impact. As a case of study the territory of the Monti Madonie Regional Park has been chosen, since it is a very heterogeneous area from the ecological point of view and a biodiversity hotspot. Shape Index has been used to evaluate pattern geometry and has been calculated for every single polygon. Resulting data has been grouped by vegetation type. Value is 1 when the patch is maximally compact and increases as patch shape becomes more irregular. Geostatistical analysis has been performed on each dataset. Acidophilous beech woods (Anemono apenninae-Fagetum) have the highest mean value (2,6), while basiphilous beech woods (Luzulo siculae-Fagetum) have a lower but still very high value (2,22). Basiphilous holm oak woods (Aceri campestris-Quercetum ilicis) show one of the highest mean values (2,43), while acidophilous holm oak woods (Geranio versicoloris-Quercetum ilicis, Teucrio siculi-Quercetum ilicis) value is lower (2,12). Even high mountain grasslands (Cerastio-Astragalion nebrodensis), serially connected to holm oak woods, show high values (2,18). Cliff vegetation (Asperulo-Potentilletum nebrodensis, Scabioso creticae-Centauretum ucriae, Anthemido cupanianae-Centauretum busambarensis) has an high value (ranging from 2,13 to 2,28) which is exclusively due to the abrupt change in slope. Thermophilous woods (IIici aquifoliae-Quercetum congestae, Oleo-Quercetum virgilianae, Quercetum leptobalanae, Erico-Quercion ilicis) have a mean value of 2,13. Grasslands and scrubs have intermediate values ranging from 1,97 to 2,03. Crops, vineyards and orange plantations have the lowest values, ranging from 1,49 to 1,82. Geostatistical analysis demonstrated a clear relationship between vegetation pattern and land use. In agricultural areas human impact produces more regualr patch shapes (low shape index value) due to cadastral limits. In natural and seminatural areas zonal vegetation shows a correlation between human impact and shape index values; in particular, woods which have been strongly exploited have higher shape index values. Azonal vegetation’s shape index value, instead, is exclusively correlated to terrain morphology.