The assessment of hedgerows and woodlots in Italy

The assessment of hedgerows and woodlots in Italy (De Natale F. 1 , Chincarini M 2 , Gasparini P 3 , Morelli S.3, Paletto A.3, Tosi V.2) Agricultural Research Council January 2011 (published on Zenodo in November 2025) 1 Affiliation in 2011 and current affiliation: CREA – Research Centre for Agriculture and Environment, via della Navicella 4, 00184 Roma – Italy (formerly researcher at CRA - Research Unit for Wood Production outside Forests, via Valle della Quistione 27, 00166 RomaItaly). Email: [email protected] 2 Affiliation in 2011 and current email contact: CREA - Research Centre for Forestry and Wood, piazza Nicolini 6, 38100 TrentoItaly (former CRA - Research Unit for Forest Monitoring and Management). Email: [email protected]; tos[email protected] 3 Affiliation in 2011 and current affiliation: CREA - Research Centre for Forestry and Wood, piazza Nicolini 6, 38100 TrentoItaly (former CRA - Research Unit for Forest Monitoring and Management). Email: patrizia.gasparin[email protected]v.it; [email protected]; stefano.morel[email protected] The assessment of hedgerows and woodlots in Italy CRA January 2011 The assessment at national level The second Italian National Forest Inventory (INFC, 2005) is an example of integration of a National Forest Inventory (NFI) and Trees outside Forest (TOF) assessment. The inventory is based on a stratified three-phase sampling, with a first phase aimed at classifying a large sample of points (approximately 301,000) on B&W digital orthophotos. Each sampling point is drawn randomly within the cell of a 1x1 km grid (unaligned systematic sampling). Following the classification procedure, few broad classes of land cover/land use were detected; in addition, the sampling points intercepting TOF were identified. The TOF investigated by INFC were restricted to woodlots, tree groups, riparian belts and tree rows. Scattered trees, orchards and other crop trees were not detected. Referring to FAO definition of forest, INFC considers as TOF the land covered by trees that fulfils the FAO requirements except for the area, that is less than 0,5 ha, and/or for the width, that is less than 20 m. The Italian NFI divides woodlots (or small tree groups) from hedgerows (or tree rows and wooded stripes). The former are forested areas spanning between 500 m2 and 5000 m2, wider than 20 m; the latter are between 3 and 20 m wide and more than 20 m long. As regards woodlots, the classification procedure refers to a minimum tree crown cover of 10%. Moreover, a minimum number of three trees was set for hedgerows. Each sampling point intercepting TOF was assigned to the surrounding land use; in case of different land uses, the closest to the sampling point was chosen. During the NFI photo-interpretation, 4,785 of the approximately 301,000 sampling points were classified as intercepting TOF. At the end of NFI photo-interpretation, a specific targeted research project (TOF Inventory) was started. All inventory sampling points intercepting TOF were surveyed again on orthophotos, by a specialized team, to verify the classification and to assess some simple quantitative/qualitative attributes (e.g. land cover/use, width, length, size, distance from forest, closeness to other hedgerows or woodlots). The NFI classification was confirmed in 94% of the cases, corresponding to 4,521 TOF sampling points. The assessment of hedgerows and woodlots in Italy CRA January 2011 The proportion of TOF sampling units was used to estimate the total area covered by hedgerows and woodlots in Italy. It is approximately 452,000 ha (s.e.= 1.5%), 1.5% of the country area (30,132,845 ha). The percentage of total forest area (Forest + Other Wooded Land) in Italy is 34.7%. Two thirds (299,500 ha) of TOF area is covered by tree hedgerows, while one third (152,600 ha) is covered by woodlots (Figure 1). Most hedgerows and woodlots (82%) are located in agricultural areas (Figure 2). 66% 34% Hedgerows Woodlots Figure 1 - TOF area distribution by type, Italian NFI estimate. Concerning hedgerows, 17.5% of them are located along roads or streets and 5.0% are along watercourses, while most of them (77.5%) are not strictly linked to these linear structures. With reference to the land use, the hedgerows along roads are about 18% of the total both in urban areas and crops, while their percentage decreases to 9% in pastures and 6% in unmanaged land. Hedgerows along watercourses are 56% of total in unmanaged land, respectively 6% and 5% in pastures and crops and even less frequent (2%) in urban areas (Figure 3). The assessment of hedgerows and woodlots in Italy CRA January 2011 10% 82% 6% 2% urban and periurban areas crops pastures not cultivated/not managed land Figure 2 – TOF area distribution by land use, Italian NFI estimate. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% urban and periurban areas crops pastures not cultivated/not managed lands other linear features along watercourses along roads Figure 3 – Percentage distribution of hedgerows by land use The assessment of hedgerows and woodlots in Italy CRA January 2011 On the whole, most woodlots and hedgerows are close to a forest stand, but woodlots tend to be closer to forest than hedgerows. The percentage of woodlots further than 2000 m away from the nearest forest stand is equal to 6.8%, while the same percentage is equal to 15.5% for hedgerows. The median distance from the nearest forest stand is equal to 290 m for linear features and 174 m for woodlots. The difference between the two median distances resulted highly statistically significant by a Chi-square test (p= 4.2*10-24). Lastly, 79% of woodlots and 63% of hedgerows are located within a distance of 500 m from the nearest forest stand (figure 4). Concerning the dimensional attributes, the mean value for woodlot area is 2072 m2, while the mean hedgerows width is 9 m (s.d. = 4.6 m) and the mean length is 283 m (s.d. = 387 m). The hedgerows length varies considerably, while the width variability is limited by the definition of hedgerows (maximum width 20 m). As regards the crown cover of hedgerows, on orthophotos the sample plots were assigned to the pattern classes sparse or dense (uninterrupted canopy cover). Results show that most hedgerows have a dense cover (94.0%), while 6.0% are sparse. An additional attribute investigated by the TOF inventory is the spatial distribution of these landscape features. For each plot intercepting woodlots or hedgerows, the presence of other TOF within a squared area of 150 X 150 m was detected. Most TOF points resulted very close to other woodlots/hedgerows and their distribution seems to be aggregated and mainly linked to specific landscape types. The percentage of woodlots close to other woodlots/hedgerows was 84.3%, while it was 75.1% for hedgerows. Also the difference between these percentages resulted highly statistically significant by a Chi-square test (p= 1.8*10-12). At present, the Agricultural Research Council (CRA) is carrying out a research project, focusing on trees outside forests: FORFAR 4 . It started in 2009 and is a follow-up project of the TOF-Inventory. It is aimed at studying the role of TOF in the Italian rural landscape, in relation to their ecological, productive and cultural functions. The research activity consists of some additional analysis of the TOF-Inventory database and in developing and testing suitable sampling protocol for large-scale field surveys. As in the TOF-Inventory, the study is restricted to hedgerows and woodlots. 4 Forest species trees in the rural landscape (responsible Dr. G. Pignatti). End date: December 2011. The assessment of hedgerows and woodlots in Italy CRA January 2011 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0-99 100-199 200-299 300-399 400-499 500-599 600-699 700-799 800-899 900-999 1000-1099 1100-1199 1200-1299 1300-1399 1400-1499 1500-1599 1600-1699 1700-1799 1800-1899 1900-1999 2000 and more Distance from the nearest forest stand (m) Woodlots Hedgerows Figure 4 – Cumulative frequency distribution of woodlots and hedgerows by distance from the nearest forest stand The assessment of hedgerows and woodlots in Italy CRA January 2011 Field survey – Veneto case study As regards field attributes of TOF, some results for Italy are available from a local study carried out on a sub-sample of NFI hedgerows located in Veneto, an administrative region in the North-Eastern Italy. The total area of Veneto is 1,838,467 ha and the forest area percentage is 24.3%. The largest part of the territory lies in the Padana Plain and landscape is strongly dominated by the agricultural land use, while forest are mainly located on higher elevations. On the whole, 258 out of 18,400 sampling points falling in the Region intercepted hedgerows. A specific field survey protocol aimed at investigating the main characters of hedgerows was applied, focusing on stand structure, dendrometric characteristics and vegetation composition. The field survey was carried out on 105 sampling plots during the years 2006-2007. The plots were selected randomly among the photo-interpretation sampling units intercepting hedgerows located in rural areas or along water courses. Two different sample plots were used, a rectangular of 15 x 5 m to measure forest attributes and a smaller inner sub-plot of 10 x 1.25 m for floristic surveys. During 2006 and 2007 field campaigns, all expected data were collected for 81 of the 105 total surveyed hedgerows; the remaining were not accessible for a complete survey or did not exist anymore as a consequence of land use changes. The main results of this study concern the management condition hedgerows, their naturalness, species composition, structure and deadwood. As regards management condition, 43,2% of the hedgerows surveyed is substantially not managed, while 66,8% is still managed. The more frequent management types are mowing, coppicing, pollarding and pruning. Most abandoned hedgerows (89%) were managed in the past. Old management practices were mostly coppicing (57%) and pruning (23%). Concerning naturalness, five classes were distinguished: planted, regenerated, remnant, planted/regenerated and regenerated/remnant. According to Forman & Godron 5 , planted hedgerows are usually highly artificial, with very low biodiversity content; remnant 5 Forman RTT, Godron M (1986): Landscape Ecology. J. Wiles and Sons, New York. The assessment of hedgerows and woodlots in Italy CRA January 2011 hedgerows originated from deforestation have the greatest amount of biodiversity and forest species; regenerated hedgerows originated by spontaneous colonization usually have an intermediate level of biodiversity. Among the surveyed hedgerows, 32.1% are planted , 30.9% are planted/regenerated and the regenerated type is also common (25.9%). None of the surveyed hedgerows is remnant, but some intermediate regenerated/remnant hedgerows were found (11.1%). As regards the dominant tree species, more than 40% of hedgerows resulted to be dominated by introduced (“allochthonous”) species. The 19.8% of hedgerows analysed are dominated by North-American Robinia pseudoacacia, the most frequent allochthonous species; Platanus hybrida (which is here considered an introduced species but its origins in Italy are doubtful) is dominant in 11.1% of the plots and Populus canadensis (an hybrid between European Populus nigra and North-American Populus deltoides) in 8.6%. Only one hedgerow was dominated by Broussonetia papyrifera and one by Morus alba, both Asiatic species. Some hedgerow structural characteristics were also surveyed. As regards the vertical structure, 40.7% of hedgerows present two layers (normally one layer of dominant trees and a second layer of shrubs), 30.9% more than two layers and 28.4% only one layer. Hedgerows resulted to be quite dense: the mean crown cover is 82.1% and it is higher in multi-layered features, with a mean value of 93.4%, than in both two-layer (79.1%) and one-layer (74.1%) structures. At last, the quantitative and qualitative presence of deadwood in the hedgerows was measured, divided into standing and lying deadwood (which was in turn divided into coarse and fine woody debris). Concerning the lying deadwood, the estimated total volume using the Line Intersect Sampling (LIS) method is 8.8 m3/ha, 5.0 m3/ha of coarse woody debris and 3.8 m3/ha of fine woody debris. Standing dead tree density is 75 stems/ha with a mean diameter of 8,9 cm; the distribution by diameter classes highlights that 60.9% of snags are concentrated in 5-10 cm class, 17.4% in 0-5 cm class, 10.9% in 10-15 cm class, while only 10.8% in >20 cm class. The distribution by decay classes reveals a high frequency of recently dead (34.8%), weakly decayed (30.4%), and medium decayed deadwood (21.7%), while only 13.1% of snags belongs to fourth and fifth decay classes. The assessment of hedgerows and woodlots in Italy CRA January 2011 Publications on Italian TOF inventory - Paletto A., Chincarini M., Tosi V. (2010). Gli alberi fuori foresta nel paesaggio dell’Italia meridionale: rilevanza, distribuzione e principali caratteri. Sherwood 161: 15-20. - Chincarini M., Paletto A., Tosi V., (2009). Valutazione della copertura arborea in formazioni forestali lineari: confronto tra densiometro sferico e stima visuale. Estimo e Territorio 1: 30-35. - Paletto A., Chincarini M., Tosi V., (2008). Une analyse de la variabilité des volumes de bois mort observée dans les haies de Vénétie (Italie). Revue Forestière Française 4: 437-450. - Paletto A., Chincarini M. (2007). Le caratteristiche delle formazioni forestali lineari venete. Alberi e Territorio 10-11: 43-47. - Paletto A., De Natale F., Gasparini P., Morelli S., Tosi V. (2006). L’Inventario degli Alberi Fuori Foresta (IAFF) come strumento di analisi del paesaggio e di supporto alle scelte di pianificazione territoriale. Forest@ 3(2): 253-266. https://doi.org/10.3832/efor0363-0030253