The national forest inventory developed a three-phase sampling research. The first phase allowed to assess the land cover/land use classes extension. Approximately 300,000 sample points, randomly located on a 1-km x 1-km grid covering the whole Italian territory, were photo-interpreted on black and white digital orthophotos by 50 NFS technicians. Flight years were between 2000 and 2003 and the approximate scale of the images was 1:10. The adopted classification system is consistent with the first level of the CORINE Land Cover System (European Commission 1993) and with the FAO-Forest Resources Assessment (FRA) definition of Forest and Other Wooded Land (OWL). The “Total Wooded Area” is given by Forest and OWL together.
The second phase allowed to finalize the classification of sample points, estimating separately Forest and OWL areas that had been assigned to the same land cover/use class by the photo-interpreters, and to separate the sample points into eight inventory categories, 23 vegetation types and 91 sub-types using a national classification scheme. The second phase has been implemented through field surveys on a sub sample of 30,000 points randomly selected from the first phase Forest and Other Wooded Land stratum. In the second phase, also information on 40 qualitative attributes were collected, such as the management status, stand origin and structure, health condition, slope instability and erosion, etc. Administrative information, such as ownership, the protection status, management plans, and others have been collected through interviews or public database queries. Digital orthophotos were used in the field to assess crown cover, texture (horizontal spatial distribution of trees), and forest edges.
In the third phase, field crews carried out quantitative measurements of trees and lying and standing dead wood and assessed some remaining stand attributes especially those related to dendrometric features. Silvicultural aspects were assessed as well as stand health condition and non timber goods production. Measurements were taken on approximately 7,000 points randomly selected from the second phase sample and stratified by administrative region and forest type.
Integrative survey for soil carbon stock evaluation are under progress on about 1,500 points randomly selected by the second phase sample. The survey protocol was similar to the one followed for the third phase field works but samples were taken from litter, organic and mineral soil and from fine woody debris.