Structural diversity of English yew (Taxus baccata L.) populations

Abstract

In Europe, the English yew species (Taxus baccata L.) is endangered. Intensive human land-use, including forest management, has caused a decrease of the yew populations all over Europe. In Austria, gene conservation forests are used for the in situ conservation of populations of this rare tree species by silvicultural treatments. In order to improve the conservation management in these gene conservation forests, this study addresses the relation between competition and viability of yew populations through the use of structural diversity indices. The structural indices, which include mingling, tree-tree distance, diameter, and tree height differentiation, were determined for a structural group of four trees as well as the neighbouring trees of the male and female yews at the monitoring plots on a regular grid in three gene conservation forests. Although the three study sites provided quite different environmental conditions for English yew, the vitality of each individual yew was influenced by the interspecific competition of the neighbouring tree species at all sites. Low vitality was associated with a small mean distance to neighbours and large tree height differentiation. In conclusion, we suggest that a combination of different structural indicators is needed for an integrative assessment of conservation status in the gene conservation forests. This would help improve the evaluation of the impact management has on yew population viability.

Response of European yews to climate change: a review

“…• In forests that contain yews such as old-growth beech forests, but also young aggressively-growing beech stands or monoculture plantations (Schwendtner, 2011;Iszkulo et al, 2012), a degree of selective thinning to reduce timber volume by around 10-20% provides beneficial light to yew trees without unduly stimulating competitive species (Dahr et al, 2006: Ruprecht et al, 2010.…”

“…Seed production and subsequent seedling growth is also better under lighter shade (<5% sunlight) although yew seedlings will survive <2% full sunlight (Dhar et al, 2007;Ruprecht et al, 2010;Iszkuło, 2010;Linares, 2013). This should help yew to find suitable microclimates beneath the canopy of other trees.…”

“…This is likely to expose seeds (which mostly germinate in the second or even third year after reaching the ground - Melzack & Watts, 1982) and new seedlings to the full force of the changing climate. In the south, where yew is scattered through more open woodlands, this may cause less of a problem since the seedlings will have some overstorey above them buffering them from harsh conditions and the yew seedlings will still be highly competitive (Iszkuło & Boratyński, 2006;Dhar et al, 2007;Ruprecht et al, 2010).…”

Regeneration in multi-species in Serra da Lousã

“…Many references can be found about regeneration processes and conditions (Kathke and Bruelheide, 2010;Barja et al, 2009;Maltez-Mouro et al, 2009;Kabrick et al, 2008;Darabant et al, 2007;Oliver, 2007;Bolte and Villanueva, 2006;Paluch, 2005;Oliver, 2003;Rozas, 2002;Page et al, 2001;Burschel et al, 1992) as well as to stand diversity analysis (Ruprecht et al, 2010;Graz, 2004;Pommerening, 2006;Pommerening, 2002;Pretzsch, 1998).…”

Forest structure of Mediterranean yew (Taxus baccata L.) populations and neighbor effects on juvenile yew performance in the NE Iberian Peninsula

“…Although yew is an extremely shade-tolerant species (Niinemets & Valladares, 2006), the competition for light has been indicated as the main factor in explaining the decline of yew populations under a dense canopy (Ruprecht et al, 2009;Schwendtner, 2011). Recently, Devaney et al (2015 reported a reduced number of juvenile yews in shade conditions in the southwest Ireland and suggested that light availability may be a limiting factor in the recruitment of yew to later demographic stages.…”