Abstract
Aim of study: In the Mediterranean region, yew (Taxus baccata L.) usually grows with other tree species in mixed forests. Yew recruitment and juvenile growth may depend on the structure of the forest and the net balance between competition for soil water and nutrients with neighbors and facilitation that these neighbors exert by protecting the plants from direct sun exposure. This study aims, at a regional scale, to analyze the structure of forests containing yew, and, on an individual level, to analyze the effect of the surrounding vegetation structure on the performance of yew juveniles.Area of study: The structural typologies of yew populations were defined based on field inventories conducted in 55 plots distributed in 14 localities in the North-Eastern (NE) Iberian Peninsula, covering a wide range of yew distribution in the area. In a second step, an analysis of neighboring species' effects on juveniles was conducted based on the data from 103 plots centered in yew juveniles in five localities.Main Results: A cluster analysis classified the inventoried stands into four forest structural types: two multi-stratified forests with scattered yew and two yew groves. Multiple regression modeling showed that the δ13C measured in last year's leaves positively relates to the basal area of conifer neighbors, but negatively with the cover of the yew crown by other trees.Research highlights: At a stand-level, the density of recruits and juveniles (625 ± 104 recruits ha-1, 259 ± 55 juveniles ha-1) in mixed forests was found to be higher than that on yew dominant stands (181 ± 88 recruits ha-1 and 57 ± 88 juveniles ha-1). At an individual-level, the water stress (estimated from leaf δ13C) of yew juveniles seems alleviated by the crown cover by neighbors while it increases with the basal area of conifers. Yew conservation should focus on selective felling for the reduction of basal area of neighbors surrounding the target tree, but avoid affecting the canopy cover to contribute to enhanced yew juvenile growth.Keywords: Biodiversity conservation; δ13C; forest management; plant-plant interaction; recruitment; Taxus baccata; water use efficiency.
Highlights
Yew (Taxus baccata L.) is a European temperate species (Preston & Hill, 1997), widely distributed in regions with mild winters and high humidity
Yew recruitment and juvenile growth may depend on the structure of the forest and the net balance between competition for soil water and nutrients with neighbors and facilitation that these neighbors exert by protecting the plants from direct sun exposure
At an individual-level, the water stress of yew juveniles seems alleviated by the crown cover by neighbors while it increases with the basal area of conifers
Summary
Yew (Taxus baccata L.) is a European temperate species (Preston & Hill, 1997), widely distributed in regions with mild winters and high humidity. In the Mediterranean region, yew trees usually grow in isolated populations in shady mountain ravines and on cliffs, or as a sub-canopy tree in a. Mediterranean yew stands were probably isolated into small populations during the last glaciations (Bennet et al, 1991) and are endangered by current land-use changes and fire spread. The need to identify appropriate management to maintain or enhance the resilience of forest ecosystems under the projected impacts of climate change has been highlighted by different authors From a conservation point of view, the identification of facilitation mechanisms may be useful for the management of threatened plants, such as the yew, or for the enhancement of the resilience of ecosystems to the projected impacts of the climate change From a conservation point of view, the identification of facilitation mechanisms may be useful for the management of threatened plants, such as the yew, or for the enhancement of the resilience of ecosystems to the projected impacts of the climate change (e.g. Batllori et al, 2009)
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