Land units map of Italy

Abstract

In this paper we present the land units map of Italy, covering an area of ca. 300,000 km² between 47°05′ N–35°29′ N and 6°37′ E–18°31′ E. The map was created by means of a Geographic Information System (GIS) and is based on the overlay of various thematic maps according to a hierarchical classification. The map scale is 1:250,000, with a minimum mapping unit of 50 ha. The GIS integration of different layers, covering the main environmental components (climate, lithology and geomorphology), resulted in a number of hierarchically arranged land units, homogeneous in terms of biotic potential and ecological processes. These units highlight the role of physical determinism in characterizing the Italian territory with a high degree of environmental heterogeneity. The proposed land classification scheme could be taken into consideration when planning initiatives aimed at surveying, monitoring, managing and sustainably developing the territory.

1. Introduction

In landscape ecological classification, land units are zones, defined on any scale, that display a certain degree of environmental homogeneity (Omernik & Bailey, 1997) and are considered as units of analysis (Loveland & Merchant, 2004; Wessels, Freitag, & van Jaarsveld, 1999). A spatial division of a geographic area into land units can be used to identify patterns of components that are dependent upon one another (Klijn & Udo de Haes, 1994; Zonneveld, 1995), thereby providing a rational basis for addressing a number of multi-scale problems in the field of landscape management and research (Cleland et al., 1997; Sanchez & Priego-Santander, 2011). These units represent a geographical framework that can be used to manage the territory according to ecological boundaries as opposed to political or administrative boundaries (Gallant, Loveland, Sohl, & Napton, 2004; Omernik, 2004; U.S. GAO, 1994). The environmental structure of land is controlled by the more stable physical features (e.g. climatic conditions, geological substrate and landform), which determine the distribution of species, habitats and potential natural vegetation types, and affect the use of the territory (Blasi & Frondoni, 2011; McMahon, Wiken, & Gauthier, 2004; Oliver et al., 2004). Therefore, land units can be identified at different geographic scales by integrating the basic environmental features of the landscape (Bailey, 2004; Cleland et al., 1997; Zonneveld, 1995). Factors that control patterns can be used to classify types and map their boundaries (Bailey, 1996).

This paper illustrates a method for the definition and mapping of land units in Italy resulting from a project funded by the Italian Ministry of the Environment, Land and Sea Protection. The project focused on a uniform national ecological classification to provide a common basis for environmental analysis at various levels. In particular, land units helped to characterize in Italy the potential natural vegetation types, defined as the vegetation in a given habitat that would develop at once to a mature stage without human influences (Tüxen, 1956), and related secondary successional stages (Blasi et al., 2011; Rosati, Marignani, & Blasi, 2008). This paper also contributes to the implementation of the European Landscape Convention (Council of Europe, Florence, 20.X.2000) by providing data on the diversity of landscape typologies at the national level.

2. Study area

Italy is located in the central Mediterranean basin between 47°05′ N – 35°29′ N and 6°37′ E – 18°31′ E. It covers approximately 300,000 km² and has a highly heterogeneous distribution of climate, physiography, vegetation cover and land use. There are two main mountain ranges (the Alps and the Apennines), extensive hilly zones, wide river valleys (first and foremost the Po plain), many large and small islands, and a long coastline.

3. Material and methods

The classification and mapping of land units was based on the relevance of significant environmental factors at different scales. The classification method and the selection of environmental factors follow a hierarchical and divisive approach (Bailey, 2004; Klijn, De Waal, & Voshaar, 1995; Sayre, Comer, Warner, & Cress, 2009) that identifies typological units occurring repeatedly within a geographic area. The nomenclature follows a scheme developed by Blasi, Carranza, Frondoni, and Rosati (2000; Blasi, Capotorti, & Frondoni, 2005). At coarse levels, the scheme subdivides land into: (i) Land Regions (ranging in scale from 1:1,000,000 to 1:250,000), based on macro-bioclimatic features; (ii) Land Systems (1:250,000 scale), delimited within the Land Regions according to diagnostic lithological features; (iii) Land Facets (ranging in scale from 1:250,000 to 1:50,000), delimited within the Land Systems according to diagnostic geomorphological features.

We systematically collected, homogenized and compiled original thematic maps of the main physical factors at the national level. For climatic regionalization we referred to the Phytoclimatic Map of Italy (scale 1:250,000) (Blasi & Michetti, 2007), extrapolating three climatic regions (Mediterranean, Transitional and Temperate). The lithological thematic layer was created by collecting, homogenizing and synthesizing geological maps at both the national (Bigi, Cosentino, Parotto, Sartori, & Scandone, 1992) and regional scales using the 1:100,000 and 1:50,000 geological sheets of the National Geological Service. The final lithological map includes eight lithological classes, plus lakes, glaciers and lagoons, which are kept as distinct units (Table 1).

Table 1. Lithological classes used to define the national lithological map.

Lithological classes	Area (ha)
Effusive igneous	1,726,392
Intrusive igneous	1,039,559
Metamorphic	2,786,297
Carbonate sedimentary	5,922,991
Chemical sedimentary	315,657
Clastic sedimentary	5,831,006
Terraced clastic sedimentary	4,172,690
Terrigenous sedimentary	7,999,558
Lakes	175,550
Glaciers	88,264
Lagoons	107,890
Total	30,165,852

A geomorphological map was drafted using a digital elevation model from the National Geoportal (http://www.pcn.minambiente.it/) with a grid cell of 75 meters, using the Topographic Position Index (Tagil & Jenness, 2008). The final map includes seven morphological classes (Table 2).

Table 2. Geomorphological classes used to define the national geomorphological map.

Geomorphological classes	Area (ha)
Coast	553,929
Plain	7,965,785
Piedmont-slope	5,830,890
Table-land	399,564
Slope	7,688,484
Summit	4,227,263
Valley	3,128,232
Lakes	175,550
Glaciers	88,264
Lagoons	107,890
Total	30,165,852

The final digital map of land classification, based on the overlay and integration of the thematic maps, was drawn up at the standard scale of 1:250,000, with a minimum mapping unit of 50 ha. Esri ArcGIS 9.2 was used for the classification process and map production. The map projection is UTM Zone 32N, Datum WGS84.

Further map data, such as hydrography, mountains and main cities, were obtained from the National Geoportal (http://www.pcn.minambiente.it/). Other background images were obtained from the ArcGIS online map service (http://www.arcgis.com/).

4. Results

The land classification process led to the identification and mapping of 3 Land Regions, 24 Land Systems and 149 Land Facets (Main Map).

The Mediterranean Land Region covers 25% of the national territory and is characterized by a summer drought lasting longer than two months, little difference between summer and winter temperature and precipitation concentrated in the autumn/winter period. The Temperate Land Region covers 58% of the national territory and is characterized by brief or no summer aridity, a generally marked difference between winter and summer temperatures and precipitation concentrated in the spring/summer period. The Transitional Land Region covers 18% of the national territory and is characterized by thermic or pluviometric variants of the Mediterranean and Temperate Land Regions.

The 24 Land Systems are fairly evenly scattered throughout the three Land Regions (Figure 1). The larger Land Systems fall within the Temperate Land Region and are associated with sedimentary terrigenous, clastic and carbonate lithological types, whereas the smaller Land Systems are always associated with sedimentary chemical and intrusive igneous lithological types.

Figure 1. Percentage of area covered by the Land Systems in Italy, arranged according to the reference Land Regions.

Only three of the 149 Land Facets cover more than 5% of the national territory. The first is the Temperate Clastic Sedimentary Plain Land Facet, which measures 26,989 km² (9% of the national territory) and is found mainly in the low Po plain.

The second is the Temperate Terrigenous Sedimentary Slope Land Facet, which measures 19,195 km² (6% of the national territory) and is distributed mainly in the northern and central Apennines. The third is the Temperate Terraced Clastic Sedimentary Plain Land Facet, which measures 19,089 km² (6% of the national territory) and is distributed mainly in the high Po plain. For a detailed description of the ecological characteristics of the Land Regions, Land Systems and Land Facets, see Appendix A in Capotorti, Guida, Siervo, Smiraglia, and Blasi (2012a).

5. Conclusions

Land classification offers the opportunity to depict the deterministic effect of physical attributes on ecosystem patterns and associated ecological processes at broad scales. The Land Units Map of Italy resulting from this work led, in particular, to the identification and mapping of the vast environmental heterogeneity that characterizes the Italian peninsula. The hierarchical framework, combined with mapping techniques and GIS, yielded a detailed spatial classification that may be used for various landscape surveying purposes. This multi-scale proposal and the consequent localization and characterization of the land units can be used to define areas that are spatial expressions of specific processes. By shedding light on landscape trends, this specificity helps to address and solve planning and management problems.

Each classification level should be used for purposes that are suited to the scale of the source materials used to compile them. For example, Land Region maps are designed for broad-scale modeling and sampling applications, Land System maps should be used for strategic ecosystem assessment or conservation purposes, while Land Facet maps are more suited to detailed analyses in project-level applications, such as landscape conservation, evaluation or ecological network design (Blasi et al., 2008).

This multilevel scheme thus identifies land units that may be effectively used to address a wide range of landscape goals, such as the assessment of the state of conservation of land mosaics in relation to their potential composition and configuration (Capotorti et al., 2012b), as well as to monitor the main threats to biodiversity, such as climate changes (Beier & Brost, 2010), biological invasions (Celesti-Grapow et al., 2010) and land cover changes (Frondoni, Mollo, & Capotorti, 2011; Smiraglia, Zavattero, Ricotta, & Blasi, 2007).

Software

The final map and related thematic layers were collected, managed and processed using Esri ArcGIS 9.2.

Acknowledgments

This work was supported by the Ministry for the Environment, Land and Sea Protection of Italy. We would like to thank Leopoldo Michetti for his helpful advice.