Characterization of the spatial structure of the canopy in Pinus silvestris L. stands in Central Spain from hemispherical photographs
Montes, Fernando | Rubio, Agustín | Barbeito, Ignacio | Cañellas, Isabel
The spatial pattern was characterized in five experimental plots of 0.5ha established in Scots pine stands located in the Central Mountain Range of Spain with different ecological conditions and in which different silvicultural practises are employed. A new method is proposed to asses the spatial pattern from hemispherical photographs, based on the variance between the gap fractions in sky sectors, which was calculated as a function of the angular distance. The results were compared with the spatial pattern analysis based on the second moment measure, and with the analysis of the structure of the tree number semivariogram. The three methods give a very similar scale of the pattern for most of the plots. The mature plot with more intensive silviculture showed a regular pattern at scales below 6m. The mature plot in which the silviculture was less intensive showed a cluster pattern at scales around 10m, and clustering at similar scales was detected during regeneration. Cluster patterns at scales around 5m were found at the upper limit of the altitudinal range of Scots pine as well as at the lower limit, where Pyrenean oak stands merge with the pinewood. The method proposed allows the scale of the pattern of the canopy to be determined from hemispherical photographs, and can be easily implemented in forest inventories.
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