Land Suitability of the Different Cultivars in the South Tyrol Wine Region (Italy)

The geology and geomorphology of the territory as well as microclimate are local geographical features that serve as natural ecological resources. These factors influence the biosynthetic activities of plants and their phenology, promoting biodiversity and the qualitative predispositions of grapes and wine. South Tyrol is one of the smallest wine-growing regions in Italy, but owing to its position amid the Alps, it is also one of the most multifaceted, a region of wide geographical diversity and remarkable ecological range, host-ing a concentration of many different vine varieties and high quality wines. This applied territorial research investigates the particular environmental circumstances that favour this case. A data set describing approximately 26,000 vineyards and 5450 hectares has been employed to evaluate 18 subzones of wines and vines selected from 86 new geographical units defined within the DOC wine region. A new environmental mapping scheme called VHTG is proposed, based on the ecological indicators of grape variety, altitude, topoclimate and the geopedology of the vineyards. Using the VHTG method analyses, the comparisons between the territories of origin and their vine varieties can be rendered simpler and more direct, and it can distinguish the most suitable ecological conditions of wine production zones. It is now possible to examine more in detail the land suitability of the different cultivars, defined by the use of the ecological indicators summarized in the VHTG method. White grape varieties such as Sylvaner and Veltliner prefer high altitudes between 600 m and 900 m, a very high solar radiation SRI index from 80 to 95, and acidic sandy soils of silicate minerals. The most complete and intense tannic structure of regional Pinot Noir correlates to quite clayey soils with dolomite mineral, slightly alkaline, and SRI around 80. The indigenous red grape variety Lagrein is mostly localized on alluvial cone at altitudes under 350 m, on soft and ventilated acid sands with volcanic silicate minerals.


Introduction
The zoning of a wine-growing region involves its subdivision into small areas within which the natural features of the environment define a homogeneous and characteristic ecosystem, distinguishable from the adjacent ones. Zoning is a complex process that takes its cue from the concept of "terroir" [1] [2] [3] [4] [5], and consists of an integrated and interdisciplinary study, aimed at dividing the territory according to its suitability for a specific crop [6]. To do this, it is necessary to read and precisely catalog all those environmental elements that can affect the vegetative, productive and qualitative expression of cultivation. In several territorial studies, the analysis of the geological and geographical component was sometimes attempted in a subsidiary way, with greater analytical attention to the agronomic soils aspects [7]- [12]. This may be partially plausible by the investigation of restricted zones, geologically simple and homogeneous [13]. On the other hand if we consider wine-growing regions, comparing many territories, as well as for the study of restricted areas with multifaceted geographical situations or for the meticulous comparison between vineyards, geopedology may be complex and variable; thus a detailed evaluation of the geological component of both terroir and soil is essential [14]- [20].
In very complex geographical environments, such as the mountainous one of the Alps, separating the evaluation of some geographical concepts from pedological, biologic, technical and cultural components could provide meaningful scientific value. Geological, geographic and anthropological conditions constitute here the distinctive elements of many wine-growing areas. They form a set of determining factors or ecological indicators that can qualify the uniqueness of a territory, its vineyards and its wines. Among these factors are geography and landforms, geopedology, altitude, climate, sun exposure and grape vine variety.
To date these elements have never been linked together by studies concerning the South Tyrol wine-growing region. A single ecological element does not necessarily determine the specificity of place for a particular grape variety; rather it is the intersection of many geographical elements that creates distinctive conditions for vineyards and their wines [21]. It is therefore necessary to plan out a The first aim of the research is to propose a new system of wine territory analysis called VHTG (Variety-Height-Topoclimate-Geology), with the objective to codify a precise method suitable for this Alpine wine region. These are terroir's fixed geographical elements or ecological indicators, which, once cataloged, may be taken as a reference in future analytical evaluations of the wines quality from different sub-zones. A second topic of the research is to verify where the different cultivars are mainly cultivated within the sub-zones of South Tyrol wine region, and to combine them with the VHTG information.
Leaving aside the anthropic component of vineyard and cellar, this study must analyse a complex compilation of multidisciplinary data. We summarize these into three main families: the territory, the vine varieties and the quality of grape and musts. Specific skills and analytical methods are needed to extract value and new knowledge from complex territorial data sets. The goal is to identify ecological indicators that facilitate predictive analysis and to search for patterns in historical and territorial information to identify risks and opportunities in viticulture.
This evaluation of ecological indicators in the extensive South Tyrol mountains is difficult and not previously methodically studied or compared within the whole viticultural region.
We have sought new approaches for this applied research and to support decision-making in the viticultural sector, and new concepts are introduced to qualify the geographical identity of vineyards in a more precise and comparable way: vineyard geopedological identity (VGI) [14] and solar radiation identity index (SRI) [22]. These derive from a scientific analysis of the territory and allow discrimination and synthesis into simple indices of two complex environmental conditions: geopedology and topoclimate. These quantitative data help to characterize the potential of each local vineyard and are useful for discerning possible influences of ecological factors on the quality of musts and wines.
SRI and VGI method are useful to discriminate and predict territorial elements strongly connected to ecological diversity and wine quality. SRI is obtained from a high detailed geospatial analysis of the whole viticultural territory, and catalogs the topoclimatic value of each single vineyard within a simple numerical index rate between 0 -100. A topoclimatic condition consists of numerous independent variables of the vineyard, such as slope, orientation, position and exposure, shading settings, the position and zenithal height of the sun in the horizon, and which, as a whole, are thus an important natural ecological resource of the territory. The topoclimatic potential of each vineyard compared to its altitude represents an interesting new key to distinguish the geographical differences between vineyards or wine-growing areas. The SRI index rate can then be related to the biosynthetic activity of the vines as well as to the quality of the  [29]. This research is motivated by the need for new scientific analysis tools that allow us to compare the ecological status of every single vineyard in the varied and complex Alto Adige DOC wine region. The vineyards here are cultivated at altitudes between 200 m and 1300 m, the highest in Europe. The average annual rainfall varies from 400 -1200 mm/year. The region receives 300 sunny days per year [30] but the angle of sun exposure of the region's approximately 26,000 individual vineyards varies by 360˚, many remaining in the shade for entire seasons and for long hours during summer days. Strong contrasts are also found in the slopes, from quite flat to extremely steep. The soils are composed of various grain sizes and mineralogies translating into very different soil characteristics from acidic to neutral or alkaline, often varying within short distances.
South Tyrol offers a unique geographical situation offering excellent opportunities for analysis and comparison of ecological indicators and of abiotic stresses that stimulate different phenological responses in the plants. South Tyrol grows over 40 varieties of grape vines, approximately half of which are employed in quantity production (Table 1 and Figure 1).

Geology and Origin of Soil Sediments
Viticulture in South Tyrol is a complex mosaic with various main actors: over 5000 winegrowers and 216 wineries [31], 40 grape varieties and a multifaceted territory. We can evaluate the latter through targeted geological and geomorphological analysis. Within a few kilometres we find glaciers, deep valleys, sunny slopes and hills covered by vineyards. The variety of alpine landscapes found in C. G. Ferretti

Geopedology of the South Tyrol Sub-Regions
We proceed to a regional geological analysis by dividing South Tyrolean vineyard areas into seven geographical sub-regions ( Figure 1 and Table 1) to describe the area's geopedology in better detail. Please note that South Tyrol is a bilingual Italian and German region so every toponym generally has two names.
While we attempt to respect this assumption, in some cases for the requirements of graphic or scientific synthesis one of the two names may be missing.

Territorial Morphology of the Wine Region
In South Tyrolean viticulture, vineyards' geographical conditions have always been of great importance. This is a practical requirement, since the farmlands of the Alpine valleys have a narrow range, limited between the impervious areas, the high mountain altitudes and the valley floors, originally unhealthy, swampy and often flooded. Over the centuries, farmers have sought optimal locations to save rural space and to ensure good yields and wines. Exposure, altitude and geographical position play a fundamental role here, regulated by the morphological and microclimatic complexity of the Alpine and Dolomite valleys. The vineyards occupy approximately 5450 hectares, only 0.6% of the land area of South Tyrol, with 93% occupied by high mountains, forests, woods and meadows at high altitude [39].
Alpine morphology results in strong vegetational and climatic contrasts. This is a consequence of a multiform territory, almost exclusively mountainous and with very accentuated differences in elevation between the valley floor and the peaks. The geography and landforms of this territory greatly reduce the availa-

Ecological Indicators and Geographical Units
Data from studies resulting in the recent subdivision of this wine-growing area into restricted units were applied to this evaluation of ecological indicators [42].
These 86 additional geographical units were delimited on a qualitative, historical and traditional basis. Each unit is combined with those specific vine varieties that are best adapted to its geographical conditions.
To outline the most significant ecological indicators on a wide regional scale, we consider four VHTG main variables: vine variety, height, topoclimate, and geopedology ( Table 2). A precise classification and comparison of these four elements provides substantial indications for evaluating qualitative and productive differences, both in terms of grape varieties and quality of wines, even on a regional scale. For each geographical unit, an analysis was carried out by overlapping territorial and historiographic information that qualifies the specific geographical identity of each individual place. This evaluation references a closed and well-defined Alpine geographical system containing many ecological variables and resulting in comparisions between territories and wines.
Geopedology has been classified using the VGI method [14]. The VGI is compiled using data and information obtained using the research technologies of applied geology, documenting in a comparable manner all of the physical, mineral and chemical characteristics of the soil sediments.
Topological parametrization of every vineyard was obtained using the SRI Solar Identity index analysis [22]. SRI is an index calculated through geospatial analysis of the entire viticultural territory and is capable of detailed classification of the different topoclimate characteristics of vineyards. Any single vineyard can be identified via its own SRI index value. It effectively describes direct exposure to solar radiation and consequent ground level diurnal temperatures.

Mineralogy of the Soil Sediments
A better understanding of the mineralogical and chemical composition of the  soil sediments and the origin of some of the mineral macronutrients present were achieved through the use of X-ray diffraction analysis. The mineral soil composition and density influences grape quality and may indirectly the organoleptic properties of wine [43]. Silicate minerals express acidic soils, dolomite minerals give moderately alkaline pH values, while limestone favours alkaline soils. The content of clays and phyllosilicate minerals supports the cation-exchange capacity and the soil moisture [44]. Without going into the analytical detail of these facts, it is observed that these are some of the geopedological elements, which fundamentally influence the biosynthetic activity of plants and the quality of its fruits [23]. The knowledge of the mineralogical component of the soils has therefore an essential meaning in the terroir investigation of the South Tyrol wine region. To determine the crystalline phases of the soil sediments, 44 diffractometric analyses (XRD) have been done to complete the VGI method of classification for the vineyards. Qualitative powder diffraction analysis (XRD) allowed estimation of the crystalline phases representative of the different geographical areas.

Analysis of the Geographical Areas and Ecological Indicators Descriptions
We identified 18 wines and vines that are more present or characteristic of particular geographical areas, as indicated in the map in Figure 3. In order to assign rigorous values to territorial data it was necessary to define which are most representative for this wine-growing research over a wide-ranging region. Drawing on experience with the South Tyrol model a new VHTG classification scheme composed of the factors of vine variety, height, topoclimate, and geopedology is proposed.
This scheme can facilitate future observation and assessment of the geographic factors of well-defined areas and classification of ecological indicators that are precursors of abiotic stress for the vines. These territorial data are transposed into a quantitative matrix that analyses vineyard altitudes, their topoclimates by means of the vineyard irradiation index (SRI), and the geopedological terroir using the VGI system. To complete the quantitative analysis, qualitative elements of the different areas are also considered, including basic information on air temperature, rainfall, prevailing winds and microclimate. In a multidisciplinary analysis involving various professional figures and scientists from different backgrounds, it is essential to provide a qualitative environmental description allowing more functional sharing of information.   The dispersion of the points in the SRI-altitude graphs reflects the ability of vine varieties to adapt to the abiotic stress caused by both altitude and topoclimate. From a graphic point of view the orientation and breadth of the data set distribution region can be clearly visualized, for example by using the kernel density estimation confidence prediction [45]. Figure 4 shows that at low altitudes the SRI data are more dispersed, the distribution region is quite vertical, and therefore solar radiation is less of a limiting factor for the vine. Where altitude becomes a limiting factor for the vine variety the distribution region is more inclined towards higher values, the SRI values increase. Some more resis-   Terlaner is a cuvee of several white grape varieties grown near the village of Terlano. The data representing three of these varieties are therefore presented. It is interesting that these grape varieties seem to be connected to different ranges of SRI and heights. Chardonnay is more widespread at lower altitudes less than 450 m: beyond this it requires high SRI. Sauvignon Blanc is widespread at low and intermediate elevations but below 600 m. Pinot Blanc has a wider distribution of altitude and SRI and grows in vineyards up to those that exceed 900 m above sea level.

Incidence of SRI and Altitude on Grape Variety
Using the schemes and the proposed classifications it is possible to distinguish and compare the topoclimate ecological indicators on a regional scale even in complex geographical environments. Future detailed analyses will require more refined comparison data; however qualitative descriptions of the areas on a regional scale already highlights geographical elements that will allow new comparisons information between grape varieties, vineyards and wine quality.
The graphs of Figure

Grape Variety and Ecological Indicators
The VHTG data collected in this study indicate geographical ecosystems characteristic of each analysed areas. The purpose of this research is to provide a base of homogeneously defined territorial information within the entire wine region, which we can refer to evaluate any different behaviours in both grapevine vegetative growth and wine's quality from different areas. Future wines evaluations and comparisons by means of vineyards monitoring, wine analysis or wine tasting will benefit from the data of this territorial classification. It is not the object of this research to analyse the geographical or pedological data in excessive detail in competition with a targeted evaluation of vineyards or specific varieties, but to identify geographic correlations between wide ranging regional territories and their wines. We can report the following main geographical markers observed in the geographical units, listed below according to grape variety or wine:  Cabernet and Merlot: Fine soils, low altitude, and warm climate [46] [47] are the distinctive geographical features for these varieties. SRIs vary greatly depending on the exposure and inclination of the vineyard. High SRI values are very important to support the long and complete ripening of the fruit in the final phase [48] [49]. From the SRI/H graph, individual vineyards with these exclusive characteristics can be distinguished. The qualitative assessments listed may be used as a basis for further study of wines from different geographical units.  Pinot Noir (Blauburgunder): Low SRI indices. The area is affected by the shadow of the mountains during long periods of the year and in the morning hours during the summer. The wide dispersion of the index confirms the adaptability of the grape variety to different geographical conditions and selective microclimates. In South Tyrol it is also cultivated at high altitudes above 1000 m, thus in low mountain microclimates, but in this case the SRI values must be high. This grape variety is recently spreading in Vinschgau, where it is now the most cultivated (Table 1). Regarding the quality of the wine, it appears that greater completeness in the tannins and aromatic expression are connected to the unit of Mazon, possessing texturally fine, alkaline soils and highly aerated vineyards [42].  Chardonnay and Pinot Gris (Ruländer): Low altitude, high temperatures, medium-low SRI and alkaline soils of the valley floor support a stylistic line of these wines which are now popular. SRI values are very scattered. Low altitude, high temperatures, medium-fine grained soils and almost constant wind are the most distinctive ecological factors of this wine area.  Sauvugnon Blanc: This grape variety has a certain adaptability to different altitudes and soils, from acid to alkaline, but its aromatic line depends on the degree of ripeness of the fruit [50] [51] and varies greatly from area to area. In this zone, the mid-hill morphology is irregular and locally steep, thus SRIs are very variable. Sandy soil sediments are enriched with dolomite minerals and are therefore alkaline.  Gewürztraminer: This grape adapts quite well to altitude and SRI, preferring fine, neutral to alkaline soils, a not too ventilated environment and day-night temperature changes. In the studied area SRI is varied due to the hilly morphology which exposes the vineyards in various directions from south to north-east. Higher SRI indices are measured at high altitudes, while air temperatures rise in the lower areas and near the valley floor so a reduction of SRI value is possible.

Dataset Representation on Maps
A goal of this research was to devise a cartographic representation form of the geospatial information, even at different scales. We are convinced that correct and clear images allow us to visualize and better understand complex geospatial concepts. Examples are presented in Figure 5, showing a 3D representation of the SRI ecological indicator, and Figure 6   In addition to information on ecological indicators in the alpine environment, this research has confirmed the necessity of an accurate geopedological classification for the territory to enable more precise soil maps [36] [52]. Given the ex- We are convinced that all the knowledge, datasets and geospatial information from both geopedological and agronomic scientific disciplines should be combined. Only in this way it is possible to obtain a more precise and faithful image of the territory as well as encouraging applied wine research in a complex alpine ecosystem.

Conclusions
The South Tyrol wine-growing region occupies a geographical complex Italian territory amid the Alps. This wine region is particularly suitable for studies of the geographical links between terroir, land suitability for viticulture and quality of their wines, because it represents a geographical system enclosed between high mountain ranges but with highly variable ecological features. A marked va- zone have been created. These will favour future interdisciplinary analyses, as well as comparisons between geographical zones and the different vines phenological behaviour or wine qualities from diverse production areas. This latter information is needed for deepening and more extended data sampling. Precise vineyards monitoring, wine analysis and wine tasting, will have to provide the information for such comparative researches.
SRI data compared to the altitude of the vineyards represents an interesting new key to the geographical peculiarities of this wine-growing territory allowing us to distinguish in detail the topoclimate differences between vineyards or wine-growing areas. Associated with the ecological information obtained from the VGI method, the data allow us to recognize and classify in great detail the winegrowing geographical units at a regional scale as well as at the scale of individual vineyards.
The geospatial analysis of metadata has made it possible to summarize complex elements in simpler and more accessible frameworks, for example by introducing geographical maps with precise indications of vineyards and wines.
This will be increasingly useful for the correct interpretation of quality and for geographical location of wines. The procedure and indices adopted for evaluation and prediction of the territoriality of wine can be extended to a global perspective as effective tools for assessing abiotic stresses in plant physiology and biogenetics, including the adaptation of plants to climate change.
This study confirms how geographical terroir indicate the preferential locations of vines and wines. Specific production areas have been identified as more dedicated to certain quality wines, therefore constituting a reference for the analysis of environmental indicators for the whole wine region. In fact, through a precise classification of the geographical identity of the territory it is possible to better assess any connection between natural ecological resources, viticulture and wine typicity.
It has been found that the white wines of the Vinschgau and Eisacktal valleys are best combined with high solar radiation, acidic sandy soils based on silicate minerals. Pinot Noir from the Mazon unit is marked by fine, slightly alkaline soils and low SRI values. A similar geopedological situation benefits the Gewürztraminer from the Söll unit, which however needs greater amounts of solar radia-