New Article: Unraveling the role of light and biotic interactions on seedling performance of four Pyrenean species along environmental gradients

 In a new article, recently published in Forest Ecology and Management, we have assessed the role of factors acting at fine spatial and temporal scale (i.e. microsite level) on the dynamics of montane and subalpine forests of the Pyrenees. We established a set of experimental mixed plantations along elevational and environmental gradients using four common species in the area: Scots pine (Pinus sylvestris), mountain pine (Pinus uncinata), silver fir (Abies alba) and birch (Betula pendula), and monitored seedling performance over 4 years. 

Short events of extreme climatic conditions (drought, freezing) had a strong impact on juvenile tree mortality, mainly affecting the species growing further from their mean elevational range. Moreover, we found that positive plant-plant interactions were markedly species-specific and varied with elevation. They were in particular present in the subalpine sites, modulating the effects of unfavorable climatic conditions for species growing above their current limits. In contrast, we did not detect any positive nor negative effect of shrubs on the plants established at the low-elevation sites, suggesting that, in such conditions, the net effect of above- and belowground interactions is neutral. In these sites, the herbaceous cover was found to negatively affect A. alba survival, probably due to competition for water. Finally our results show a positive effect of canopy closure on silver fir survival.

 In summary, our study underlined that plant-plant interactions and other factors driving at fine temporal and spatial scales can have a strong impact in the dynamics of montane-subalpine forests of the Pyrenees. These processes acting at microsite level should thus be explicitly considered when implementing management plans to contend the future impacts of climate change in these areas.

Ameztegui, A; Coll, L (2013) Unraveling the role of light and biotic interactions on seedling performance of four Pyrenean species along environmental gradients. Forest Ecology and Management 303: 25-34.

The study area, in the Cadí Range, Catalonia (Photo: Aitor Ameztegui)