A miscellany of traditional management techniques ...

135

Hedgerow Futures Edited by John W. Dover

A miscellany of traditional management techniques of woody field margins on the Po Plain, Italy: implications for biodiversity conservation T. Sitzia1*, T. Campagnaro1, D. McCollin2, and M. Dainese1 1 Land, Environment, Agriculture and Forestry Department, University of Padova, Legnaro (PD), I-35020 Italy; 2 Landscape and Biodiversity Research Group, School of Science and Technology, The University of Northampton, Northampton, NN2 6JD, United Kingdom * Corresponding author: [email protected] ABSTRACT Here we summarise the findings of a study investigating the environmental, management, and land use factors that influence patterns of biodiversity in field margins in the Po Plain, Italy, and evaluate these habitats for their cultural and biodiversity value. We highlight four traditional management techniques of woody vegetation in field margins on the Po Plain, Italy, and make recommendations for further study to investigate the ecosystem services and cultural significance of these features. INTRODUCTION Field margins assume an important ecological function in agricultural landscapes for both animal and plant species (Marshall & Smith, 1987). The progressive reduction of field margin density, related to changes in agricultural and urban land use, leads not only to habitat loss, but also to the loss of the fundamental functions which the field margins provide: for example, to the contribution of biomass production (Mezzalira, 1997) and to the rural landscape quality (Tempesta, 2006). Field margins provide functions with variable intensity according to their shape, growth habit and continuity of the vegetation (Zanaboni & Lorenzoni, 1989; Baudry et al., 2000). A knowledge of such hedgerow characteristics in rural landscapes is necessary to develop strategies for conservation, although standardised survey methods are not available (but, see DEFRA, 2007). Several studies have analysed the historic, economic, productive and ecological aspects of the North-eastern Po Plain (Paoletti, 1984; Paoletti & Lorenzoni, 1989; Zanetti, 1994; Mezzalira, 1997; Mannino et al., 2001; Correale Santacroce & Dalla Valle, 2007; Sitzia, 2007). Bidese & Peruffo (1993) applied a standard survey procedure that permitted the collection of sufficient information to describe in detail the principal characteristics of hedgerows, such as size, stand structure and tree species composition. Similarly, Franco & Chiozzotto (1995), Virgilietti & Dalla Valle (1998) and Franco (2000) surveyed the stand structural types (i.e., high and low windbreaks and shrubs), size and connectivity of the ecological network assumed as a network of hedgerows. However, a uniform survey procedure has rarely been applied at the regional scale. Here we present our work with the objective to fill this gap in order to better understand the biodiversity implications linked to different hedgerow attributes, hence, the focus will be on those intrinsic features that favour - or are in connection with - biodiversity. Recovering and integrating the contents of these studies, we applied a standard survey procedure of the vegetation community, structural, biophysical and biometric characters of the hedgerows to more than 500 field margins. Surveys were conducted at seven sites distributed within the landscape of two districts of the Po Plain: the low Venetian Plain and the reclaimed areas of Verona and Polesine (Bernardi, 2003; Cantarello, 2003; Milan, 2003; Berardo, 2005; Rizzi, 2006; Trentanovi, 2008).

Hedgerow Futures

136

Edited by John W. Dover

Whilst the main body of this work is presented elsewhere (Sitzia et al., in preparation), the purpose of this paper is to highlight the range of traditional management techniques present in the study region. METHODS Selection of sites and hedgerows The 56.4% of the Veneto Region (10,372 km2) is located on a plain area (De Pietro et al., 2008) that has been cultivated continuously since the 9th century AD and since the 1970s has acquired suburban and urban characteristics (Sereni, 1961; Paoletti & Lorenzoni, 1989; Tempesta, 2010). Land reclamation and hydraulic interventions have occurred at different times. 80% of the land is actually classified as agricultural land (Migliorini, 1972; RegioneVeneto, 2005). Therefore, the selection criteria of the sites were conditioned by the territorial structure that has been shaped by these changes.

Figure 1 Northern Italy with the Po Plain (diagonal fill pattern). The survey sites are represented by letters (a: Canda, b: Frassinelli, c: Montegalda, d: Nogara, e: Peseggia, f: Piove di Sacco, g: Roncade) and are located within the boundary of the Veneto Region.

Seven survey sites (Figure 1) were selected on the basis of differences in agricultural intensity, measured according to municipal mean enterprise UAA (Utilized Agricultural Area) classes, subdividing the study areas in proportion to the total area of each class in the Veneto plain. The UAA classes considered are (C.I.A., 2003): • high (≥ 10 ha) • intermediate (3-10 ha) • low (< 3 ha) The mean enterprise UAA values can easily be acquired and are linked to the parcelling of the rural area that in turn conditions the quality of the landscape management by the enterprises (Trisorio, 2005).

Hedgerow Futures

137


Definition of hedgerow Within each area all the hedgerows were surveyed. The term hedgerow has been defined in different ways by different authors - although the one defining feature is that they comprise linear elements represented by shrubs and/or trees within a given landscape (Pollard et al., 1974; Corbit et al., 1999; Boutin et al., 2002). Here, we followed Bidese & Peruffo (1993) and Bickmore (2002) and define hedgerows using the following criteria: • the function is not exclusively ornamental; • the percentage of tree and/or shrub cover interruption of 2 m (gap) must be lower than 35%; • the length of a single gap must not exceed 20 m; beyond this threshold the gap is an opening that divides two different hedgerows; • the minimum distance between hedgerows must be 20 m; • the width must not exceed 20 m. The above measures refer to the horizontal plane. These measures should usually be assessed visually; however, in the case of ambiguous observations measurements are needed. The width is intended as that measure taken perpendicular to the hedgerow axis and adjoining the projection to the ground of those points representing the maximum extension of the crowns at the margins (Del Favero et al., 1998). The number of hedgerows corresponding to the above mentioned requirements and their density, varied between the sites as shown in Table 1. Table 1 General information on the sites under investigation: location, sampling area, number of hedgerows, UAA classes and hedgerow density. Site name

Municipalities

Sampling area (ha)

Surveyed hedgerows

UAA classes*

Hedgerow density (km/100ha)

Nogara

Nogara, Gazzo Veronese, Sorgà

625

59

H

2.7

Canda

Canda, Castelguglielmo

4,572

68

H

0.85

Piove di Sacco

Piove di Sacco, Arzegrande, Brugine, Pontelongo

420

107

L

6.97

Frassinelli

Martellago, Spinea, Brugine, Pontelongo

158

47

L

8.67

Peseggia

Zero Branco (TV), Scorzè (VE)

175

59

L

8.14

Roncade

Roncade

645

106

I

3.79

Montegalda

Grisignano di Zocco, Montegalda

627

92

I

3.92

*UAA classes: H (high), I (intermediate) and L (low).

Survey protocol For each hedgerow the surveyed characteristics are reported and defined in Table 2. Some of these were surveyed by considering the whole hedgerow as the sampling unit, whereas others were measured by subdividing the longitudinal length of the hedgerow in equal parts. The number of these equal parts was proportional to the total length (L) as described here below: • single part (L < 100 m);

Hedgerow Futures

138


• two parts (100 m ≤ L < 300m); • three parts (300m ≤ L < 600 m); • four parts (L ≥ 600 m). Table 2 List of the surveyed hedgerow characteristics, their definition and [unit of measurements]. Character

Sampling method*

Definition and units of measurements

Hedge stand type (MS)

W

Identified by the different growth forms (shrubs, trees, coppices, pollards) of the woody species composing the hedgerow [multi-storied, two-storied, high single-storied, low single-storied].

Planimetric organization (PO)

W

Number of rows with a maximum distance of 5 m [single-row, two-row, multi-row].

Length (LG)

W

Linear development of the sampled unit (surveyed hedgerow) [m].

Width (WD)

S

Mean of the widths referring to the projection to the ground of the two points of maximum expansion of the marginal crown on the principal perpendicular axis of the hedgerow [m].

Width of permanent vegetation (WP)

S

Mean of the widths of permanent herbaceous and woody vegetation, not periodically removed by plough [m].

Total length of gaps (LG)

W

Sum of the length of gaps [m]: interruptions of the tree and/or shrub cover with length > 2m.

Ditch width (DW)

S

Mean of the width of ditches (a continuous narrow trench in the ground that enables water flow; located within or externally to the hedgerow) [cm].

Ditch depth (DD)

S

Mean of ditches depth [cm].

Mean diameter (WSD)

S

Mean dendrometric diameter of individuals with dbh ≥ 5 cm in classes of 1 cm [cm].

Mean height (WSH)

S

Cormometric height of individuals with dbh ≥ 5 cm in classes of 1 m [m].

Woody species richness (WSR)

W

Number of woody species, excluded those with only basal woody stem.

Number of snags (NS)

W

Number of standing dead trees with dbh ≥ 10 cm.

Number of logs (NF)

W

Number of fallen dead trees with dbh ≥ 10 cm.

* Sampling method indicates whether the whole hedgerow was surveyed (W) or the survey was carried out in subunits of 100 m length (S).

Within the centre of each part a sampling subunit of 10 m was surveyed. The values recorded in each subunit were then averaged for the whole hedgerow. The identification of the hedge structure was carried out through the analyses of the presence of four natural and artificial growth forms of the woody species that shape the hedgerows with a varying vertical distribution complexity of trees and shrubs (Sitzia et al., in preparation). These four identified hedge stand types are as follows: • multi-storied (formed by trees, shrubs, coppices and with or without pollards);

Hedgerow Futures

139


• two-storied (formed by pollards and shrubs or pollards and coppices or trees and shrubs or trees and coppices); • low single-storied (formed by coppices and shrubs, or only coppices or only shrubs); • high single-storied (formed by pollards and trees, or only pollards, or only trees). Shrubs and coppices usually form the low storey while pollards and trees the high storey (Figure 2). All woody species were identified to species and diameter and height for each stem (dbh ≥ 5 cm) were recorded. Furthermore, for the Montegalda site a supplementary survey on the herbaceous species present within the hedgerows’ boundaries was carried out. The sampling units were divided in order to obtain units with homogenous hedgerow structure and to include all of their variety found in such area. All vascular plants were identified to species. Herbaceous species were divided into different groups: forest, arable weeds and wetland species. These groups were chosen due to their different habitat requirements and to the site conditions that are found in the studied landscape context. Timing of fieldwork The survey was conducted between May and July. This period permitted easy access to agricultural fields compared to late summer as the crops during the later period, in particular maize crops, reach a development stage that reduces the accessibility and limits visibility. The mean number of field forms that can be filled by a skilled surveyor ranges from between 5-6 per day, corresponding to roughly one field form every 90 minutes (Sitzia et al., 2011).

Figure 2 The hedge stand types result from a combination of a maximum height of the growth forms (high tree, pollard, coppice, shrub) and a number of stories (one, two, multi). (a) multi-storied, (b) high single-storied, (c) two-storied, (d) low single-storied (modified from Sitzia et al. (2011)).

RESULTS AND DISCUSSION Physical characters and hedge stand structure The majority of the surveyed hedgerows (72%) were shorter than 200 m (Figure 3) whereas the majority of the remaining ones (21%) did not exceed 400 m. For 92% of the hedgerows the width of the permanent vegetation (WP) did not exceed 6 m (Figure 4). The mean width of WP is often associated with the species diversity of hedgerows (Hegarty & Cooper, 1994). It is widely acknowledged that the width (DW) and depth (DD) of ditches (Table 3) are of relevance for the presence of wildlife, for example bird species (O’Connor & Shrubb, 1986; Hinsley & Bellamy, 2000). Important habitat plants linked to wet environments (e.g., species of the genus Lemna, Iris and Alisma) due to the presence of water in the ditches increased the biodiversity of hedgerows

140


Figure 3 Number of hedgerows divided into length (LG) classes.

Figure 4 Number of hedgerows divided into width of the permanent vegetation (WP) classes.

and of their neighbouring ecosystems. The length (LG) and proportion (LG/100 m) of gaps has a strong influence in determining the dispersal capacity of plants and animals in hedgerows (Joyce et al., 1999; Baudry et al., 2000; Roy & de Blois, 2008; Silva & Prince, 2008). Multi-storied represents the most frequent hedge stand type (36%), highlighting a general complex structure of the tree and shrub layers within the studied hedgerows. As widely documented for forests (Pretzsch, 1997; Brokaw & Lent, 1998), ecosystems with a wide variability of structural components host a large variety of ecological niches hence, this can also be inferred for hedgerows. In fact, the diverse combination of trees, coppices, shrubs and pollards within hedgerows (corresponding to the multi-storied structure) creates a site with a higher habitat diversity for animal and plant species (Cook, 2002; Pisapia, 2009). Figure 5 shows the subdivision of the four hedgerow structures for each selected site, whereas Figure 6 shows the distribution of the various typologies of planimetric organization. Unusually high values in the

141


Figure 5 Proportion of the hedge stand types (MS) for each site.

Figure 6 Proportion of the planimetric organization (PO) of the hedgerows for each site.

biometric characters (Table 3) are related to an unusual low ratio between the hedgerow width and its density of stems and might be associated to hedgerows with a very limited availability of space for the development of the woody component and/or to a very high level of disturbance. Woody species and dead wood Figure 7 shows that only a small proportion of the analysed hedgerows had more than 14 woody species; the most common were (frequency > 40%): Salix alba L., Cornus sanguinea L., Platanus hybrida Bot., Sambucus nigra L., Rubus ulmifolius Schott, Robinia pseudoacacia L., Acer campestre L., Ulmus minor Miller. Aliens represent more than one third of the observed woody species (44 out of a total of 123). Most of the aliens are neophytes and only four (Robinia

142


Figure 7 Number of hedgerows hosting different woody species richness (WSR) classes.

Figure 8 Woody species richness (WSR) for each hedgerow stand type (MS). The median is indicated by the vertical line that runs down the center of the box.

pseudoacacia L., Parthenocissus quinquefolia (L.) Planchon, Ailanthus altissima (Miller) Swingle, Phytolacca americana L.) of these species are those considered by Celesti-Grapow et al. (2010) as invasive in the Veneto Region. One finding of note is that invasive light-demanding species, such as Robinia pseudoacacia L. and Ailanthus altissima (Miller) Swingle, are very common in agricultural landscapes and are expanding in hedgerows and from hedgerows into strips of no longer actively managed land. Figure 8 shows the relationship between hedge stand type and native woody species richness, highlighting that hedgerows with a higher structural complexity host a higher number

Hedgerow Futures

143


of woody species. This, together with the positive relation between woody species richness and bird diversity (Hinsley & Bellamy, 2000), strengthens the importance of multi-storied hedgerows for biodiversity as already suggested above (see section on physical characters and hedge stand structure). Dead wood (Table 3) ranks in the most important among diversity indicators as it favours the creation of ecological niches of many species (e.g., for saproxylic organisms) (Mason, 2001). Standing dead trees (snags) of hedgerows are important for a number of bird species for which they use cavities for nesting or roost sites, for example great tit (Parus major L.), European green woodpecker (Picus viridis L.) and tawny owl (Strix aluco L.) (Camerini & Groppali, 2003; Pisapia, 2009). Table 3 Hedgerow characteristics divided into physical, biometric and diversity characters. For each character the mean, standard deviation (SD), maximum and minimum value observed is given. Characters

Mean

SD

Max

Min

Length (LG) [m]

173

137

1,000

30

Width (WD) [m]

5.66

2.03

17

0.5

Area (LG x WD) [m2]

996

892

7,500

56

Width of permanent vegetation (WP) [m]

2.74

2.43

15

0.05

Total length of gaps (LG) [m]

7.03

13.88

123

0

LG/100 m [m/100m]

4.05

6.84

33.5

0

Ditch width (DW) [cm]

171

121

600

0

Ditch depth (DD) [cm]

80

57

300

0

Mean diameter (WSD) [cm]

14.4

9.6

60

5

Mean height (WSH) [m]

7.5

2.3

18.2

2

Physical characters

Biometric characters

Basal area per hectare [m /ha]

36.7

51.2

711.2

0.6

Density of stems (dbh≥5cm) [n/ha]

2,700

3,027

35,294

153

Woody species richness (WRS)

9.97

5.05

27

1

WRS in 100 m

8.11

5.82

37.14

0.34

Native woody species richness (NWR)

6.5

3.7

20

0

Alien woody species richness (AWR)

3.1

2.3

15

0

Number of standing dead trees per 100 m (NS/100 m)

0.5

2.0

28.5

0

Number of fallen dead trees (NF/100m)

0.2

1.3

27.1

0

2

Indexes of diversity

Herbaceous species The hedgerows in Montegalda contained a total of 180 species, of which 23 were forest species, 40 arable weeds and 20 wetland species. Surprisingly, only a few of the recorded herbs were alien. Both wetland and forest species occurred with a similar frequency whereas, as expected, arable weeds were roughly three times more frequent.

144


Limitations of the hedge stand classification The classification of the hedgerow structure into four types was successful in that most hedgerows fell readily into these classes. However, this typology encompasses a range of management types both modern and traditional and, although land use is dominated by intensive agriculture, it is worth emphasising the strong cultural traditions that survive in this landscape. Traditional management techniques of hedgerows in this landscape include coppice, pollards, shredded trees, and stubs (trees cut at a height in-between coppice and pollards). This was an interesting finding in this study and attests to farmers and landowners finding value in the cut wood, although further study is needed to investigate the meanings and values of hedgerows to farmers in the Po Plain and the ecosystem services they provide. Further, this management is applied irrespective of the origins of species and is applied equally both to native and aliens. This suggests that management is adaptive and is flexible to changing conditions. CONCLUSIONS Whilst this work was carried out to take a standard forestry approach to an analysis of the structure and composition of hedgerows a surprising finding was the frequency of traditional management - by a variety of methods - which suggests that the cultural value of hedgerows is not lost in the Po Plain. However, the degree to which this is changing is unknown. The high frequency of some trees that were traditionally planted and used due to their multifunctionality (e.g., Morus alba L. was important for the farm’s self-production of fruits and for the cultivation of silkworms) represents an important legacy of past practices as their execution is nowadays almost lost. More work is needed on the ecosystem services provided by hedgerows in the Po Plain and on the relationships between people, field margins, and biodiversity. REFERENCE LIST

Baudry, J.; Bunce, R. G. H. & Burel, F. (2000). Hedgerows: An international perspective on their origin, function and management. Journal of Environmental Management 60:7-22. Berardo, A. (2005). Valutazione dell’efficacia delle siepi nella tutela della biodiversità. Caso studio delle Valli Veronesi. MS Thesis. Università degli Studi di Padova. Bernardi, C. (2003). Diversità strutturale, caratteristiche biofisiche ed indice di forma dei sistemi agroforestali di roncade (TV). MS Thesis. Università degli Studi di Padova. Bickmore, J. C. (2002). Hedgerow Survey Handbook, a standard procedure for local survey in the UK. Countryside Council for Wales, Bangor. Bidese, F. & Peruffo, A. (1993). Rilievo del sistema di siepi ed alberate campestri in un’area agricola del Veneto. Acer 9(6):9-13. Boutin, C.; Jobin, B.; Belanger, L. & Choiniere, L. (2002). Plant diversity in three types of hedgerows adjacent to cropfields. Biodiversity and Conservation 11:1-25. Brokaw, N. V. L. & Lent, R. A. (1998). Vertical structure. In: M. L. Hunter (ed.). Maintaing biodiversity in Forest Ecosystems. Cambridge University Press, Cambridge (UK), pp. 373-399. C.I.A. (2003). Atlante dell’Agricoltura Veneta. Confederazione Italiana Agricoltori, Padova. Camerini, G. & Groppali, R. (2003). Avifauna e siepi negli ambienti coltivati della pianura. Pianura 16:93-108. Cantarello, E. (2003). Struttura, biometria forme ed evoluzione decennale di 200 siepi boscate planiziali. MS Thesis. Università degli Studi di Padova. Celesti-Grapow, L.; Pretto, F.; Carli, E. & Blasi, C. (eds.) (2010). Flora vascolare alloctona e invasiva delle regioni d’Italia. Casa Editrice Università La Sapienza, Roma. Cook, E. A. (2002). landscape structure indices for assessing urban ecological networks. Landscape and Urban Planning 58:269-280. Corbit, M.; Marks, P. L. & Gardescu, S. (1999). Hedgerows as habitat corridors for forest herbs in central New York, USA. Journal of Ecology 87:220-232. Correale Santacroce, F. & Dalla Valle, C. (2007). Gli impianti lineari polifunzionali nel territorio agricolo. Alberi e Territorio 4(3):14-19. De Pietro, C.; Vignotto, C.; Lucchese, E.; Bovo, V. & Franz, A. (2008). L’Italia secondo i Conti Pubblici

145


Territoriali (CPT). I flussi finanziari pubblici nella Regione Veneto. Regione Veneto, Venezia. DEFRA. (2007). Hedgerow Survey Handbook. A standard procedure for local surveys in the UK. UK Department for Environment, Food and Rural Affairs, London. Del Favero, R.; Andrich, O. & Carraro, G. (1998). Norme per la redazione dei piani di riordino forestale. Regione del Veneto - Direzione Regionale Foreste ed Economia Montana, Mestre (Venice). Franco, D. (2000). Paesaggio, reti ecologiche e agroforestazione. Il Verde Editoriale, Milano. Franco, D. & Chiozzotto, E. (1995). Un progetto di riqualificazione ecologico-produttiva nel paesaggio rurale del Comune di Venezia. Acer 11(3):10-17. Hegarty, C. A. & Cooper, A. (1994). Regional Variation of Hedge Structure and Composition in NorthernIreland in Relation to Management and Land-Use. Biology and Environment-Proceedings of the Royal Irish Academy 94B:223-236. Hinsley, S. A. & Bellamy, P. E. (2000). The influence of hedge structure, management and landscape context on the value of hedgerows to birds: A review. Journal of Environmental Management 60:33-49. Joyce, K. A.; Holland, J. M. & Doncaster, C. P. (1999). Influences of hedgerow intersections and gaps on the movement of carabid beetles. Bulletin of Entomological Research 89:523-531. Mannino, I.; Franco, D. & Zanetto, G. (2001). Reti ecologiche agroforestali e processi paesaggistici: la valutazione socio-economica. Genio Rurale 64(1):22-28. Marshall, E. J. P. & Smith, B. D. (1987). Field margin flora and fauna; interaction with agriculture. In: J. M. Way & P. W. Greig-Smith (eds.). Field margins. British Crop Protection Council, Thornton Heath, pp. 23-33. Mason, F. (2001). Problematiche di conservazione e gestione. In: S. Ruffo (ed.). Le foreste della Pianura Padana. Un labirinto dissolto. Museo Friulano di Storia Naturale, Udine, pp. 91-138. Mezzalira, G. (1997). Siepi per la produzione di legna da ardere nella pianura veneta. Sherwood - Foreste ed Alberi Oggi 21:13-18. Migliorini, E. (1972). Veneto. Collana “Le Regioni d’Italia”, Vol. IV. Unione Tipografico - Editrice Torinese, Torino. Milan, L. (2003). I corridoi ecologici del Polesine: forme, struttura e biodiversità dei sistemi arborei nel territorio rurale. MS Thesis. Università degli Studi di Padova. O’Connor, R. J. & Shrubb, M. (1986). Farming and Birds. Cambridge University Press, Cambridge (UK). Paoletti, M. G. (1984). La vetazione spontanea dell’agroecosistema e il controllo dei fitofagi del mais. Atti Giornate Fitopatologiche 11:445-456. Paoletti, M. G. & Lorenzoni, G. G. (1989). Agroecology Patterns in Northeastern Italy. Agriculture Ecosystems & Environment 27:139-154. Pisapia, A. (2009). Condomini affollati. Acer 25(1):37-39. Pollard, E.; Hooper, M. D. & Moore, N. W. (1974). Hedges. W. Collins Sons, London. Pretzsch, H. (1997). Analysis and modelling of spatial stand structure. Methodological considerations based on mixed beech-larch stands in Lower Saxony. Forest Ecology and Management 97:237-253. RegioneVeneto. (2005). Programma di Sviluppo Rurale per il Veneto 2007-2013. Regione Veneto, Venezia. Rizzi, A. (2006). Complessità strutturale dei corridoi arborei lineari nel paesaggio rurale di Montegalda (VI). MS Thesis. Università degli Studi di Padova. Roy, V. & de Blois, S. (2008). Evaluating hedgerow corridors for the conservation of native forest herb diversity. Biological Conservation 141:298-307. Sereni, E. (1961). Storia del paesaggio agrario. Laterza, Roma. Silva, M. & Prince, M. E. (2008). The conservation value of hedgerows for small mammals in prince Edward Island, Canada. American Midland Naturalist 159:110-124. Sitzia, T. (2007). Hedgerows as corridors for woodland plants: a test on the Po Plain, northern Italy. Plant Ecology 188:235-252. Sitzia, T.; Trentanovi, G.; Rizzi, A. & Cattaneo, D. (2011). Siepi rurali: struttura arborea e biofisica. Proposta e applicazione di un protocollo di rilevamento. Sherwood - Foreste ed Alberi Oggi 174:25-31. Tempesta, T. (2006). Il valore del paesaggio rurale. In: T. Tempesta & M. Thiene (eds.). Percezione e valore del paesaggio. FrancoAngeli, Milano, pp. 9-108. Tempesta, T. (2010). The perception of agrarian historical landscapes: A study of the Veneto plain in Italy. Landscape and Urban Planning 97:258-272. Trentanovi, G. (2008). Biodiversità nel paesaggio rurale: relazioni tra struttura e flora delle siepi della Saccisica (Padova, Nord Italia). MS Thesis. Università degli Studi di Padova. Trisorio, A. (2005). Misurare la sostenibilità, indicatori per l’agricoltura italiana. Istituto Nazionale di Economia Agraria, Roma. Virgilietti, P. & Dalla Valle, C. (1998). Indagine sulle siepi campestri progettate dall’Azienda Regionale

146


Foreste del Veneto tra il 1991 e il 1993. Sherwood - Foreste ed Alberi Oggi 35:9-11. Zanaboni, A. & Lorenzoni, G. G. (1989). The importance of relict vegetation and hedges in the agroecosystems and environment reconstruction. Agriculture Ecosystems & Environment 27:155-161. Zanetti, M. (1994). Progetto siepe. Il Pendolino, San Donà di Piave (Venice).