Abstract
Forests in the montane-Mediterranean zone have only recently began to be affected by wildfires, therefore the knowledge necessary for restoration projects is missing. The aim of the study was to assess the effects of factors related to seedling attributes, weather conditions and site suitability on seedling performance. The characterisation of sites was based on bedrock and soil clay content as well as pre-fire vegetation. Apical growth and survival of seedlings was monitored for four years in Parnitha National Park. The parameters of a linear mixed model were estimated using annual apical growth of seedlings surviving in the end of the study as the dependent variable and type of site, rainfall, initial seedling height and age as explanatory ones. A quantile regression model using all the data available was estimated for each year of study, taking into account only initial height and site type as well as a logistic regression model of survival. The findings indicate that the growth of Greek fir seedlings depends on May rainfall mediated by soil clay content, which in turn depends on bedrock, which is consistent with the “inverse texture hypothesis”. Sites with low soil clay content were always more beneficial for survival, which was stronger affected by summer–autumn rainfall. In both contexts, drought stress due to soil clay content fades with increasing age. Sites that were not fir dominated prior to fire proved unsuitable also for planting fir seedlings. A minor part of the observed variability could be associated with the initial height of seedlings, especially for seedlings showing high rates of apical growth.
Highlights
The natural vegetation in the Mediterranean area, as elsewhere, is characterised by a zonation defined by altitude
The analysis reveals that the effects of rainfall on apical growth differ among sites
The starting point of the present study was the hypothesis that the annual apical growth and the survival of outplanted Greek fir seedlings would be affected in the same way by factors that distinguish seedlings, sites and years among each other, namely seedling height at planting, geological substrate and soil attributes and prefire vegetation of the site as well as rainfall
Summary
The natural vegetation in the Mediterranean area, as elsewhere, is characterised by a zonation defined by altitude. The Greek fir is a species endemic to south-central Greece that forms forests covering large areas in the montane-Mediterranean zone of its geographic distribution, typically between 900 and 1400 m asl, while isolated individuals are present from 600 to almost 2000 m asl [1]. This zone was hardly affected by wildfires in the past, but it has been increasingly affected in recent years. According to [2], 95,000 ha located higher than 900 m asl were affected by wildfires between 1983 and 2008; to the best of our knowledge, the first large scale wildfire affecting a Greek fir forest occurred in 2000 in Mainalo, Peloponnese.
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