Derivation of characteristics for the evaluation of game impact on tree regeneration

Background

Ungulate density and the percentage of browsed tree regeneration (browsing intensity (BI)) were positively correlated in 49 browsing inventories across Switzerland. However, BI indicates a non-linear relation to tree density and development. Hence, there are areas with little or no tree regeneration partly due to ungulates despite low BI. Contrary are areas with high regeneration density and trees developing through all height classes despite high BI (>30%). Browsing severity, tree reaction after browsing and tree growth could cause such site-specific differences.

Furthermore, the wolf currently returns to its traditional distribution area in central Europe. As a large carnivore, he will change the interactions between the organisms there. The impact of wolves on wild ungulates and on the vegetation cover and its composition is manifold: besides direct, numeric effects of wolves on the abundance and demography of their prey populations (like chamois, roe deer and red deer), indirect functional effects through mediated behavior of ungulates are also reported. Since the spatio-temporal habitat use of prey species is mediated by the occurrence and abundance of large predators, we cannot assume that the browsing level will gradually decrease in Switzerland. In contrast, trophic interactions between predators, herbivores and forests are complex and multilayered, in particular because forest ecosystems in central Europe are strongly influenced by forestry and hunting practices.

Project objectives

The project aims are i) to publish a literatur review about the complex direct and indirect relationships between wolf and forest regeneration ii) find gaps in the characteristics to evaluate the impact of game, iii) based on that develop an adjusted monitoring instrument and iv) test this monitoring concept in the region Calanda and 3 other surfaces in the canton of St. Gallen (Northeast Switzerland).

Research questions

1.   What are the potential effects of wolfes on the Swiss forests?
2.   How does the browsing intensity influence the regeneration structure? That is, to what extent differ locations where a browsing intensity on fir of less than 9% already causes a failure of the fir regeneration from those where fir regeneration is still present with> 20% to even> 30% browsing intensity and over the course of time can grew up through the height classes?
3.   With which additional simple characteristics can these differences in the browsing influence be determined in browsing surveys?
4.   What is the current influence of game on forest rejuvenation in the area of Calanda?
Method
Based on a literature review about the cascading impact of carnivores on forest the effects for Switzerland were estimated.
See Kupferschmid, A.D. & Bollmann, K. 2016. Direkte, indirekte und kombinierte Effekte von Wölfen auf die Waldverjüngung. Schweizerische Zeitschrift für Forstwesen. 167: 3–12.

In the main part of the project data were collected on 15 sampling points on 12 areas with different regeneration densities and browsing intensity (BI). Information were obtained on litter layer, humus type, soil pH, light, basal area, stand development etc. With regards to regeneration browsing severity of the terminal shoot and entire tree (see picture on "Verbissstärke"), browsing frequency, reaction after browsing and height increment where examined on trees in four height classes with i) the nearest 5 trees up to 10m distance, ii) the 6 dominant trees and iii) all trees in a 2-5m circular plot per sampling point. Furthermore, influences of the site such as growth rate, mortality caused by ungulate browsing and delayed reaction after browsing are examined by means of simulations under various browsing intensities. Lastly, the found features with differentiation characteristics are subsequently tested with foresters. This test was carried out in the 3 indicator areas on the St. Gallen side of the Calanda area, 3 additional indicator areas in the canton of St. Gallen and in 4 areas with rejuvenation sampling on the Grisons side of the Calanda mountain. The aim is to approach a scientifically based monitoring of the influence of ungulates on tree regeneration, which can easily be implemented by foresters.

First results

Publications regarding the cascading effect wolf - game - forest

Kupferschmid, A.D.& Bollmann, K. 2016. Direkte, indirekte und kombinierte Effekte von Wölfen auf die Waldverjüngung. Schweiz. Z. Forstwes. 167:3–12.

Kupferschmid, A.D. & . Bollmann, K. 2017. Effekte von Wölfen auf die Waldverjügnung in der Schweiz. www.waldwissen.net.

Kupferschmid, A.D., Beeli, F.& Thormann, J.-J. 2018. Effekte des Wolfrudels am Calanda auf die lokale Waldverjüngung. Bünder Wald 71:37-44.

Kupferschmid, A.D. 2017. Local trophic cascading impact of wolves on tree regeneration in summer and winter areas of ungulates. In: 6th symposium for research in protected areas. Salzburg. 353-356.

Publications about the influence of ungulate browsing

Kupferschmid, A.D. 2018. Selective behaviour of ungulates influences the growth of Abies alba differently depending on forest type. For. Ecol. Manage. 429:317-326.

Kupferschmid A.D, Brang P, Bugmann H. 2019. Abschätzung des Einflusses von Verbiss durch wildlebende Huftiere auf die Baumverjüngung. Schweiz. Z. Forstwes. 170:125–34

Publications about the pilot study for estimating the influence of ungulate browsing in two wildlife areas in the canton of St. Gallen

Kupferschmid AD. 2019. Verjüngungskontrolle St. Gallen: Auswertungen zur Piloterhebung 2018 in den Wildräumen 2 und 8, Eidg. Forschungsanstalt WSL, Birmensdorf. 103p. DOI: 10.13140/RG.2.2.33154.02242

Kupferschmid, A.D., Wunder, J.& Gmür, P. 2018. VEKO - Verjüngungskontrolle St. Gallen Pilotphase 2018. Birmensdorf, Eidg. Forschungsanstalt WSL & Kantonsforstamt St. Gallen. 24p. Version 6 vom 21. März 2018. DOI: 10.13140/RG.2.2.35791.02720

Kupferschmid, A.D. 2017. Einfluss des Verbisses: Empfehlungen zur Merkmalserhebung an den Kanton St. Gallen. Birmensdorf: Eidg. Forschungsanstalt WSL. 44.