Structural analysis of mixed stands coming from natural regeneration and plantations after fire

We analyzed the structure and growth of naturally regenerated stands of <i>Pinus brutia</i> that mixed with planted broad-leaved and conifer species, 12 years after wildfire and examined the degree of species mix. Field data on stand structure of <i>P. brutia</i> forest were taken in spring 2009 on northern and southern aspects differing in regeneration conditions. Sixteen sample plots were selected and all individuals and their attributes measured. The results showed that in northern aspects the forest is composed of <i>P. brutia</i> in the over-storey and <i>Quercus pubescens</i> and <i>Cupressus sempervirens</i> in the under-storey, while in southern aspects the forest was mainly composed by <i>P. brutia</i> (81%). Stem diameter distribution of <i>P. brutia</i> in both aspects followed almost a normal pattern. All <i>P. brutia</i> individuals were characterized by vigorous growth and good to normal stem quality. Aspect did not statistically affect structural characteristics of <i>P. brutia</i> trees and saplings. However, on the northern aspect stem diameter, height, crown length and basal area of <i>P. brutia</i> were greater than in the southern aspect. Aspect significantly affected structural characteristics of <i>Q. pubescens</i>

The effect of fire severity on first-year seedling establishment in a Pinus canariensis forest on Tenerife, Canary Islands

The Canarian pine (Pinus canariensis) exhibits a striking combination of high adult resistance to fire and intermediate serotiny. Hence, the study of its post-fire regeneration can support valuable new insights about functional adaptations to fire. Here, we analyse the firstyear seedling establishment after fire in a P. canariensis forest on the northern slope of Tenerife, Canary Islands. The effects of fire severity and other explanatory variables on the seedling density recorded 9 months after fire were examined. We detected a clear unimodal relationship between seedling density and fire severity, with maximum regeneration associated with intermediate fire severity and no regeneration associated with very high crown damage. The results suggested that high severity fires may have caused the partial destruction of the aerial seed bank and/or the creation of unfavourable seedbed conditions for germination and seedling emergence. The density of large pine trees, reflecting seed availability, was the second most important factor explaining the distribution of seedlings. Cover of scorched needle litter on the ground correlated strongly and positively with pine seedling density and negatively with fire severity. The complete lack of regeneration at sites most strongly affected by fire does not represent a major threat for the stand recovery of the Canarian pine, due to the very high tree resistance to fire and the tremendous capacity of the Canarian pine to resprout after fire. The observed very high seedling densities at sites with intermediate fire impacts can probably be related to both the complete liberation of the seed bank (including seeds stored in serotinous cones) and favourable micro-environmental conditions for seed germination and seedling establishment