Predicting mechanisms across scales: amplified effects of abiotic constraints on the recruitment of yewTaxus baccata

Abstract

Efforts to disentangle the mechanisms underlying large‐scale spatial patterns need to rely on multi‐scale approaches. We illustrate this key issue by analyzing the spatial consistency across scales of the effects of abiotic constraints on the regeneration of English yew Taxus baccata in Europe. We hypothesized that the recruitment rates in a given population would be strongly affected by water availability, which should result in a predictable pattern of regeneration success at regional and continental scales. Accordingly, we predicted: 1) at the regional scale water availability should be higher in sites occupied by yew populations than in random locations; 2) at the regional scale regeneration success should decrease when water availability is lower; and 3) at the continental scale, regeneration success should also decrease where water availability is lower, resulting in decreasing regeneration southwards. To test these predictions we first monitored seedling emergence and survival in two central Spanish populations over two years, and confirmed that yew recruitment is limited by water availability. Additionally, our analysis supported predictions 1 and 2: water availability strongly affected yew presence and regeneration success. At the continental scale (prediction 3), our results confirmed lower regeneration in southern European populations. Assessing the effect of climatic constraints across scales in key population parameters can help to improve large‐scale assessments of impacts of climate change on biodiversity.

Geographic consistency in the seed dispersal patterns of Taxus baccata L. in the Iberian Peninsula

“…Over the past centuries, yew populations have been declining in number, size, and therefore in connectivity (Dovčiak, 2002;Linares, 2013), especially at the margins of its geographical range (Sanz, 2008;González-Martínez et al, 2010). In the Iberian Peninsula, T. baccata is widespread, but most populations are small and suffer from lack of regeneration due to constrained recruitment (Abel et al, 2007;Sanz et al, 2009;Linares, 2013). Two 2 variability (Jordano, 1993).…”

“…However, few studies have actually assessed how consistent or inconsistent are those systems. On one hand, discerning whether the local, small-scale patterns of seed dispersal -with most of seeds being deposited under conspecific trees but very few out of forest -are generalized across yew distribution range is a prerequisite for the development of integrative and large-scale management plans (see also Sanz et al, 2009). On the other hand, understanding the magnitude and the sense of inter-annual variability in yew seed dispersal patterns is key to assess the ability of the species to cope with rapid ecological changes, especially those derived from human impact (Hampe, 2011).…”

Response of European yews to climate change: a review

“…European yew and climate change ditions (Sanz et al, 2009;Mendoza et al, 2009b). As above, this is most likely to operate at the level of reduced numbers of seedlings.…”

Summer rainfall variability in European Mediterranean mountains from the sixteenth to the twentieth century reconstructed from tree rings

“…The decrease in frequency of these wet events therefore implies a northward latitudinal displacement of these forests in the Mediterranean region, together with a substantial reduction thereof, as was modelled by Benito et al (2006Benito et al ( , 2008, García and Allué (2010), Keenan et al (2011), Ruiz-Labourdette et al (2011b, Engler et al (2011) or Thuiller et al (2011. Changes in this sense can perhaps be observed in Mediterranean mountains-Pinus uncinata , Taxus baccata (Sanz et al 2009) or Abies pinsapo (Linares and Carreira 2009). Our results indicate that the direct and indirect effects of extreme events on Mediterranean ecosystems might be greater than those caused by the mean change trends (Peñuelas et al 2000;Walther et al 2002;Gutschick and BassiriRad 2003;Groom et al 2004;Pausas 2004;Pausas and Fernández-Muñoz 2012).…”