Spatial pattern and characteristic of tree-fall gaps to approach ecological forestry in northern Iran

Gaps created by falling trees (tree-fall gaps) are natural in forest ecosystems. Understanding scale, pattern and the effect of gaps on regeneration is important to current and future forest management. The aim of this study was to determine the size, shape and spatial pattern of tree-fall gaps and the associated forest regeneration. The study was carried out in three parcels (No. 15, 18 and 19) of the second District in Shastkalateh Forest in northern Iran. The size, location and regeneration of all tree-fall gaps were measured in the parcels. One way ANOVA was used to compare gap features and regeneration and Spearman’s rank correlation coefficient was used to test the relationship between gap size and regeneration density. The results showed that the total area of gaps created by tree-fall in the three parcels was 13.72 ha, or 7.4% and on average there were 1.06 gaps per hectare. Gap size ranged from 49 m2 to 1827 m2, with mean gap size being 658.2 m2. Most (69.2%) gaps were 200 m2 to 1000 m2 in size. Results of the spatial pattern analysis showed both uniform and irregular shapes for gaps in three parcels. ANOVA analysis showed a statistically significant difference between gap size and regeneration density and the Spearman rank correlation showed a direct relationship between gap size and the number of seedlings. These results provide useful information to manage forests according to ecological principles.