3.9 The Italian Forest Inventory: Methods, Results and Perspectives Vittorio Tosi
Summary
The first Italian Forest Inventory was carried out in 1985 using a procedure of systematic sampling with a network of sample plots regularly distributed on the ground. On every point classified as forest data was principally collected with the aim to inform about the wood resources (surfaces and volumes) at national level. The results of the inventory gave an image of the nation richer in forest areas than previously estimated. However it should be noticed that a large part of the forests consist of coppice and shrubland. Also the amount of volume of wood, especially of high forests, is not negligible.
Today we need more information about the forest area classified as brushwood, the vegetation of forest floor and a better knowledge of vegetation types. The next inventory should not be limited to the study of forest resources (like the first IFI), leaving out the analysis of the inter-relationships with other environmental resources and other uses of the land in general. Biomass of the entire vegetation, habitat of wildlife, the biodiversity, the risk of fire and recreation potential are some of the information to be gathered with a multi-resource inventory system. Other data obtained from various sources can be added to the traditional ones. This data, preferably with geographical references, should be integrated with information periodically collected with a network of monitoring projects and combined in a national geographic information system.
Keywords: national forest inventory, ground survey, inventory data, multiple resource inventory.
3.9.1 Introduction
The idea and planning of the first, and until now the only, national inventory of Italian forests began at the beginning of the 1980s and the collection of data started in 1983 and was completed in 1985. The final results were published in 1988.
The commission which was set up by the Ministry of Agriculture and Forestry suggested following a method which enabled the collection of the relevant information with the maximum ease and in the shortest possible time (at the same time keeping costs at a reasonable level). The model which fulfilled these demands had been used for the Forest Inventory of Bavaria (1970-71). The Institute in Trento was responsible for this project and in effect designed the preliminary approach.
3.9.2 Methods
A project of systematic sampling was planned to be carried out in one phase, consisting entirely of samples taken from the ground. Right at the start the idea of obtaining an overall view from aerial photographs was rejected due to the fact that suitable photographs of the national territory were not available and would have meant a special flight to carry out this work which would have delayed the start of the project, caused an increase in the costs and created the need to train personnel to interpret the photos.
The sample points were selected on the intersections of a grid every 3 km on an official map of the state with a scale of 1:25000.
Each point therefore represented 900 hectares, and there was a total of 33500 points selected over the national territory.
But not all of these areas were surveyed on the ground. A large number were classified as outside the context of the inventory (ie. they weren't forest) after a preliminary analysis using maps and photographic information (where recent aerial photographs were available a quick examination of the possible location of the survey area was carried out on the photograph).
The remaining areas were identified on the ground by an open ·topographic survey, starting with a datum point marked on the map. The information was collected using a compass, clinometer, range finder (or measuring wheel) and a programmed pocket calculator. The access route and the position of the sample area were described briefly including some topographic reference points to find the area again. A metal stake was planted at the end of the collection of data operation.
The sampling teams (personnel from the C.F.S. - National Forestry Corps) were composed of a team leader (usually a forestry graduate), a trained assistant and a general assistant. The teams were usually also aided by a local forest warden.
The teams were able to survey, on average, 2 to 3 areas a day.
The national inventory of italian forests cost about 2 million dollars (referred to 9 years ago), which equals about 25 cents per hectare of forest area or an average cost of 227 dollars for each sample area.
Standard definitions
Wherever possible European standard definitions for the classification of forest areas were adhered to, even though the characteristic of a high level of fragmentation in Italian woodland required a decrease in the size of the minimum area. The requisites for an area to be considered forest were as follows: minimum area 2000 m2, minimum width 20 m and at least 20% cover. In the case of areas newly reforested or without vegetation due to removal or unusual occurrences the cover was evaluated using conventional methods.
Sample unit
Around a sample point sample plots with fixed radius of 600 m 2 were delimited, with the possibility of reducing the area to 400 or 200 m2 when the size of the trees with certain conditions of density would have had made the collection of data too difficult. So, for example, in the high forests the area was reduced to 400 m2 where the height of the dominant trees was between 10 and 20 m and the actual cover more than 50%. The area could have been reduced to 200 m 2 if the cover had been 50% and the height of the dominant trees had been between 5 and 10 m. In the coppice forests the area could be reduced to 200 m2 if the same parameters existed as for the high forests, while an area of 400 m2 was suitable when the dominant height was between 10 and 15 m.
Data collection
As well as the general descriptive characteristics of the forest areas containing the sample points (height above sea level, slope, orientation, viability, possibility of extraction, ownership, restrictions, etc.) in the sample area information was collected regarding the local value of variables of interest. Having ascertained that the volume of the woody mass
could be obtained using double entry tables, the results in the areas classified as high forest consisted of the measurements:
- diameters measured at 1.3 m from ground level for trees above the 2.5 cm diameter limit;
- the height of a sub-sample of trees distributed in different diametric classes, representatives of the species or group of species present (in pure stands or those composed of only conifers or only broadleaf species: 15 tree heights with a DBH above 17.5 cm and 5 for those with DBH between 7.5 and 17.5; in the mixed stands: 10 measurements for each species or group); in such a manner it was developed a high curve for each sample plot and for each species or group.
- the diameter increment, from a boring, on the same trees used for the height measurements;
- the stump (diameter of a section) of trees felled during the last solar year, if present.
Other data were collected including tree type by origin, technological characteristics of the stem and average age of the even-age stands.
For the coppice forests the data collected were limited to the measurement of the diameter of the coppice shoots, a height measurement sample, as well as a combined measurement (height-diametric) of the standard trees present.
Volume
Each tree present in the sample area was given a height at the DBH deduced from the height curve produced for each species ( or group) in each sample unit.
For the volume of the trees the preferred method was to draw up suitable tables of double entry ( d,h), starting with the existing volume function already derived for the principal species in Italy, rather than produce new tables for the whole national territory involving the collection of sample trees in the sample areas. Such a choice was determined by economic and administrative considerations, with noticeable advantages from an operational point of view. While for the coppice forests the functions produced covered the whole high-diameter range, for the high forests, given that the minimum diameter limit of the tables was 15 cm, it was necessary to use particular mensuration with reference to the examples with small dimensions.
Estimate of the woody mass increment
From the samples (cores) taken at 1.3 m with a Pressler increment borer the current annual radial increment was deduced, while for the increment in height, more difficult to measure directly, a system of functions describing the development of height in relation to diameter at 1.3 m was used. This enabled the estimation of the variation in height that on average took place with variation of diameter. From the values of the estimate of actual radial increment and the statistical average height one, the volume increment percent was determined (combined explicit method of Hellrigl).
Volume of felled wood
The presence of stumps in the area, cut less than one year previously, allowed an estimate of the amount felled. This was achieved by obtaining relationships between diameter at the base and at 1,3 m, measuring the diameter of the section of the stumps and also the DBH of the subjects of comparable dimensions growing nearby.
The areas covered with particular vegetation (brushwood, maquis, riparian forest and rock-plants), as well as high forest stands or coppice forests with height less than 5 m required a reduced amount of information to be collected, and this was limited to an estimate at a distance (without physically delimiting the area) of the specific composition, average height and age.
It was hoped that the information obtained would provide results on a national scale. In fact for the principal stratifications results were also obtained on a regional level, with an acceptable standard error width.
3.9.3 Results of the First Italian Forest Inventory
A few years ago the Director General of Forests commented on the initial results of the inventory, defining Italy as a "country rich in poor forests". This can be explained by the fact that the forest surfaces altogether turned out to be of higher value than that supplied from forestry statistics. However in the forest surfaces are included areas covered by minor vegetation (shrubland, rock-plants, etc.), which, even though they have no great economic value, are important in ecological terms.
Some figures
National forest area - ordinary forest surface
high forest coppice forest
specialised forest area
(poplar, sweet chestnut, cork oak) particular forest area
( shrubland, etc.)
Distribution of ownership:
Specific composition of forest area:
conifer broadleaf mixed
8,675,000 ha (29% of the total area of the nation (SE% = 0,9)
6,1 47,000 ha
2,1 79,000 ha (SE% = 2.0) 3,674,000 ha (SE% = 1 .3)
279,000 ha 2,239,000 ha 2/3 private 1/3 public 16 % 81 % 4 %
Volume of wood in high forests (>5 m): 405,000,000 m3 average volume per hectare 211 m3 (SE% = 1.6) current annual increment 15,000,000 m 3 current annual increment per hectare 7.9 m3
( considering only the trees over 17 .5 cm of diameter the value of increment is 5.1 m 3, 2.9 in percent and the average volume per hectare is 177 m 3)
Volume of wood in coppice forests (>5 m):
average volume per hectare 323,000,000 m3 115 m3
Proportion of volume of specific composition ( ordinary forest area and specialised):
conifer: 268,566,000 m3 (36.2%)
broadleaf: 472,420,000 m3 (63.8%)
Felling:
- in the areas considered coppice, 2% of the area is felled annually;
- in the high forest areas little more than 1 % of the volume (SE% = 25) is removed and 36% of the current increment of high forest.
Results which the first Italian Forest Inventory did not supply
Some information was considered to be adequate in the ideal project situation but now it is insufficient.
In particular there is a lack of knowledge on the present state of:
- the land cover classified as brushwood which constitute 26% of the total forest area (with reference in particular to the estimate of biomass, but also the grade of covering, the proportion of type of vegetation);
- the amount of the biomasses of the vegetation classified as "low";
- the vegetation of the forest floor, the spontaneous flora, useful for identifying the phytosociology of the vegetation type.
On these topics, the first Italian Forest Inventory survey collected only some information regarding the presence and distribution of regeneration.
3.9.4 Towards a Multi-Resource Inventory
No decisions have yet been made about repeating the IFI due to the reforms which have recently affected the Ministry and which have partially blocked activity.
After finishing the first IFI some inventorial surveys were initiated at a regional level.
However the activities in the region of Liguria are interesting, where an inventorial map is being prepared of the environmental resources, with the aim of evaluating the possibility of producing an informative system, at a national level, for the forest environment.
There is no doubt that a new inventory could not be limited to the study of forest resources (like the first IFI), leaving out the analysis of the inter-relationships with other environmental resources and other uses of the land in general.
It is therefore necessary on the one hand to widen the scope of the information gathered, examining (as well as forests) also pastures, alpine meadows, uncultivated land and formations which are not forests, and on the other hand to evaluate the natural environ
ment with respect to the whole of its resources.
In order to do this an inventorial structure with multiple functions, of a permanent nature, capable of checking the current conditions and evolving dynamics is needed. Such a structure must be simple and flexible so that the acquisition and integration of the information from the different sources is possible at various levels ( eg. national, regional, local) and according to a multi-resource philosophy.
It is important to succeed in using various available sources: maps, satellite images, aerial photographs, to these other data can be added obtained from various sources (eg.
history of fires). This data, preferably with geographical references, should be integrated with information periodically collected with a network of monitoring projects and combined in a national geographic information system.
Among the objectives of the inventory should be the evaluation of the biomass, including the dead woody material (for all levels of vegetation including the lower and for all ecosystems), the collection of information on the habitat and wildlife, present and
potential, (in this regard the horizontal and vertical profile of vegetation is important), the development of the biodiversity and evolving tendencies, the risk of fire (index of combustibility of the ecosystems), the leisure potential, the level of hydrogeological protection and the wildness of the woods.
It would also seem more logical if the forestry personnel integrated with other interested parties for a coordinated approach to the description of the territory.
3.9.5 References
BIANCHI, M.; T OSI, V., 1992: L'inventario forestale nel rilievo globale degli ambienti naturali e seminaturali. Proceedings of seminar held in Brasimone (Bo), UNIF, ISAFA, ENEA. Trento.
CASTELLANI, C.; S CRINZI, G.; TABACCHI, G.; T OSI, V .• 1983: Inventario Forestale Nazionale Italiano. Istruzioni per le squadre di rilevamento. Ministero dell'Agricoltura e delle Foreste.
Istituto Sperimentale per l'Assestamento Forestale e per l'Alpicoltura. Trento.
CASTELLANI , C.; S CRINZI, G.; TA BACCHI, G.; T OSI, V ., 1984: lnventario forestale nazionale (I.F.N.). Tavole di cubatura a doppia entrata. Ministero dell'Agricoltura e delle Foreste. Istituto Sperimentale per l'Assestamento Forestale e per l'Alpicoltura. Trento.
CASTELLANI, C.; S CRINZI, G.; TABACCHI, G.; TOSI, V ., 1988: lnventario Forestale Nazionale.
Sintesi metodologica e risultati. Ministero dell'Agricoltura e delle Foreste. lstituto Sperimentale per l'Assestamento forestale e per l'Alpicoltura. Trento.
SCRINZI, G. , 1986: Invenlario forestale nazionale italiano: cenni sui principali aspelli metodologici.
Dendronalura, n. 1.
TOSI, V.; CARUSO, C., 1 985: ltalienische Forslinvenlur. Forstliche Nalionalinventuren in Europa.
Milleilungen der Abteilung fi.ir forslliche Biometrie, Freiburg i. Br. 85,3: 179-198.
