Translocation of Pagoeta yew plant to promote connectivity of yew woods in Aralar

03-12-2019
According to findings from the characterization surveys conducted in the Basque Country, yew trees presence and density are significant in Pagoeta, with a well-connected representative population and abundant regeneration.

Actually, yew woods of Pagoeta may be making up a metapopulation with other yew tree woods located outside the SCA area, as well as in other Natura 2000 sites close by, such as Hernio Gazume and Izarraitz.
On the contrary, yew stands in Aralar are further apart to each other and, on top of that, the younger specimens are missing and regeneration is hardly seen. It seems that the herbivorous effect and the land-use regime shift that reduced forest canopy in the past are the cause. 
 
Apparently this scenario has not affected negatively the genetic structure of populations in Aralar and probably this is because it is too early to tell although this is clearly a negative condition for the habitat long-term conservation. 

This situation, along with the preliminary outcomes of the genetic study, makes the translocation strategy of Pagoeta yew seedlings to reinforce and interconnect Aralar populations especially appealing.
 
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The following factors were considered in addressing[1]:
 
  • - The effect on donor population. Translocation practice should not have any impact on these donor stands in Pagoeta. To this end, seedlings were dispersedly removed all times without leaving any bald areas in the regenerated population of two types of areas:
  •  
  •         ·High-density regenerated areas under yew trees of certain size. These seedlings will not be viable
  •         because they live under another specimen but they feature high densities, from 1 to 10 plants per
  •         square meter.
  •         ·“Golpes de tejo” (Holes of yew trees) that include many plants with their viability at jeopardy because
  •         density itself. A number of 5 plants per square meter is always retained.   
  •  
  • - Genetic relation. The relation between the donor and the host populations needs to be adequate from the genetic point of view. To this end, the genetic study outcomes were taken into account.
  • - Genetic diversity. To avoid negative genetic effects, seedlings from several donor stands will be translocated with the aim of providing the utmost genetic diversity to the translocated set.
  • - Viability in host conditions. For a successful translocation, translocated seedlings should be able to develop in Aralar or in other areas. To do so, translocations should be carefully implemented (extraction, nursery fattening up and plantation stages) and the causes that lead to the current scenario that continues showing active effects —namely herbivores— should be dealt with.
  •  
Taking this design as a basis, 350 seedlings were removed from 6 stands in Pagoeta. These were selected according to their genetic diversity and relation with the Gipuzkoa populations.

Removal took place in March 2019 by trying to keep as much seedling root apparatus as possible and transferring them on site to tray-containers with peat.

They were first irrigated in the same location and most of them were moved to the Diputación Foral of Gipuzkoa Arizmendi Nursing, in 2 days at most. Some of them were directly planted in Aralar in an experimental way, as early as possible.

Plants brought to the nursery were treated with fungicides. Subsequently, they remained under controlled conditions during a 6-8 month growth phase until being planted in the fall-winter of 2019, in fenced areas to be protected from herbivores
 
[1] Adapted from “Guidelines for Reintroductions and Other Conservation Translocations. IUCN 2013”