Browsing resilience of fir, spurce and beach saplings

Due to long-term selection processes, autochthonous tree populations are well adapted to their local environments. Consequently, such provenances are differentiated in many traits. Furthermore, large herbivores have become major drivers of forest dynamics worldwide. Have traits evolved that allow both adaptation to climate change and resilience to ungulate browsing?

Main research questions

1. What is the influence of the genetic variation of autochtonous populations of fir (Abies alba), spruce (Picea abies) and beech (Fagus sylvatica) in relation to their growth habit and reaction after leader shoot loss due to browsing (or artificial clipping) and / or frost damage in Switzerland?
2. Are the proveniences that are well adapted to the future climate (ADAPT project: adaptive genetic variation of spruce, fir and beech) also for the forestry valuable provenances with good growth and of high quality?
3. Do the proveniences that are well adapted to the future climate react quickly and efficiently to the leader shoot loss due to browsing by deer and chamois?
4. Does the site have an impact on the provenience specific resilience after browsing?
5. Adaption to climate and ungulate browsing: Are both possible?

Method

In an extensive genecological common garden experiment, we investigated quantitative genetic variation within and among provenances of Abies alba, Picea abies, and Fagus sylvatica. Each species was represented by approx. 90 autochthonous provenances, covering the species’ ecological range in Switzerland (e.g., elevations from 330 until 2100 m a.s.l.). In 2012, ca. 4000 seedlings per species were planted in a single tree random plot design in an open-land study site.

Growth and phenology were measured in 2013 and 2014 (ADAPT).

In spring 2015, the saplings were clipped with three intensities (heavy, slight and no clipping) to simulated browsing by roe and red deer. Growth reactions were assessed one and two growing seasons after treatment, and provenance differences will be related to environmental variables of seed sources.

First Results

Growth traits before clipping showed higher genetic variation among provenances for Picea abies than for Abies alba and Fagus sylvatica, but provenances of both coniferous species from low elevations grew significantly faster than those from high elevations. Growth and clipping increased the variation in Abies alba. but microsite conditions are probably as important in determine growth and resilience after clipping than genetic differentiations among provenances. Analysing sapling traits measured two years after clipping and related these with environmental variables of seed sources will allow identifying potential among-provenance differences with respect to climate change and herbivory and show if proper provenance selection continues to be more important for Picea abies than for Abies alba and Fagus sylvatica.