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Title: Assessing the attributes of scattered trees outside the forest by a multi-phase sampling strategy
Authors: Baffetta, Federica
Corona, Piermaria
Fattorini, Lorenzo
Keywords: Forest inventories;Multi-phase sampling strategy;Tree outside forest
Issue Date: 2011
Publisher: Oxford University Press
Source: Baffetta, F., Corona, P., Fattorini, F. 2011. Assessing the attributes of scattered trees outside the forest by a multi-phase sampling strategy. "Forestry" 84 (3):315-325
A sampling strategy to be used with multi - phase forest inventories is proposed for assessing scattered trees outside the
forest on large territories. The fi rst phase is carried out by means of a systematic search over the area to be inventoried.
The area is partitioned into regular polygons of the same size and points are randomly located, one per polygon.
Subsequently, in the second phase, the land cover class of the fi rst-phase points is determined by very high - resolution
remotely sensed imagery and a sample of points are selected from each land cover stratum. Then, the number of trees
outside the forest lying within plots at the sampled points is recorded on the imagery. Finally, in the third phase, a
subsample is selected from the second-phase samples of each stratum and the biophysical attributes of trees within plots
are measured in the fi eld. Approximately unbiased estimators of abundance and of totals and averages of biophysical
attributes are achieved in the second and third phase , respectively, together with the estimators of the corresponding
variances. A simulation study is performed in order to assess the accuracy of the strategy under random and aggregated
distributions of trees. The sampling errors achieved in the second phase using sampling fractions of ~ 0.3 per cent of
trees vary from 6 to 13 per cent , whereas the errors achieved in the third phase using sampling fractions of ~ 0.15 per
cent vary from 15 to 31 per cent . The results obtained from three case studies carried out in Italy confi rm the accuracy
levels achieved in the simulation.
L'articolo è disponibile sul sito dell'editore
ISSN: 0015-752X
DOI: 10.1093/forestry/cpr015
Appears in Collections:DiSAFRi - Archivio della produzione scientifica

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