Clone-dependent browsing damage of poplar plantations and the repellent potential of Populus nigra × P. maximowiczii ʻMax-4’

Abstract

Browsing of poplar clones by wild ungulates is a widespread problem in short rotation coppice (SRC) plantations in Central Europe. We investigated the influence of poplar genotype on ungulate browsing intensity, identified the most browsing-resistant poplar clone and explored its repellent potential. Inspection of 11 poplar clones at 7 unfenced SRC plantations in the Czech Republic revealed the most avoided poplar clone by wildlife was Populus nigra × P. maximowiczii ʻMax-4’. Namely P. maximowiczii contributed to the repellent effect of ʻMax-4’ according to the analysis of impacts of individual parental poplar species on the browsing intensity of their hybrid progeny. In contrast, P. deltoides increased attractiveness of its hybrid progeny for browsing ungulates. Poplar browsing and bark stripping/fraying were not correlated. A subsequent feeding experiment with twigs of two poplar clones that had shown contrasting attractiveness for browsing in the field (intensively browsed P. × euroamericana AF24’ vs. avoided P. nigra × P. maximowiczii ʻMax-4’) demonstrated that red deer hinds (Cervus elaphus L.) bred on an experimental farm preferred ʻAF24’ over ʻMax-4’. There was no difference between consumption of fresh and wilted twigs of ʻMax-4’ suggesting the repellent compounds are stable over time. To uncover the chemical nature of repellent compounds, red deer hinds at the farm were offered grain fodder supplemented with polar and non-polar extracts of ʻMax-4’ shoots, commercial repellent (Stop Z) or empty carrier (controls). Non-polar extract of ʻMax-4’ produced transient feeding avoidance suggesting its potential as a game repellent, though optimisation of the extraction procedure and dosage is necessary.