Assessing the attributes of scattered trees outside the forest by a multi-phase sampling strategy
Authors: Baffetta, Federica; Corona, Piermaria; Fattorini, Lorenzo
Source: Forestry, Volume 84, Number 3, 02 2011 , pp. 315-325(11)
Publisher: Oxford University Press
Abstract:A sampling strategy to be used with multi-phase forest inventories is proposed for assessing scattered trees outside the forest on large territories. The first 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 first-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 field. 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 confirm the accuracy levels achieved in the simulation.
Document Type: Research Article
Publication date: 02 2011
- Forestry publishes refereed papers on all aspects of research, practice and policy that promote the sustainable development of forests, woodlands and trees. In considering suitability for publication attention is given to both the originality of contributions and their practical application. Preference is usually given to work undertaken in the temperate and/or boreal zones; only articles of exceptional merit from tropical zones will also be considered.