Young conifer stands form a deer browsing refuge for an oak admixture: silvicultural implications for forest regeneration under herbivore pressure

Abstract

There is little knowledge how ungulate pressure on forest regeneration may be mitigated by silvicultural methods. The knowledge is especially needed for artificially regenerated, deciduous tree species. We studied factors affecting browsing incidence by deer in the Pisz Forest District in Poland, an area where 10,000 ha of forest was damaged by a 2002 hurricane. In 2006, we established three experimental plots (in total, 22.6 ha), in which the main species was Scots pine (Pinus sylvestris) admixed with pedunculate oak (Quercus robur). The data on browsing were collected in 2008-2015. In general, oak browsing incidence was unrelated to oak planting density. On a plantation scale, it was significantly affected by the pine age. Although in each variant all the oaks were browsed for four consecutive years (2009)(2010)(2011)(2012), in 2013 browsing incidence began to decrease. When the pines grew higher and formed a physical barrier, it was harder for deer-roe deer (Capreolus capreolus), red deer (Cervus elaphus) and moose (Alces alces)-to move through and locate the oaks. Moreover, within plantations, oak browsing incidence was higher in the patches with shorter pines.Browsing of individual saplings or small groups of saplings was also negatively affected by the height of neighbouring pine saplings. Oak density influenced deer selectivity depending on the tree height. In a low oak tree density, browsing incidence was unrelated to oak height, while in higher tree density, deer selected oaks of the height between 40 and 100 cm. We postulate that deciduous admixture in a coniferous (unattractive) stand can be planted with a few year delay. Older coniferous trees should impede locating of attractive tree species by deer and the browsing incidence.

Herbivory and Competing Vegetation Interact as Site Limiting Factors in Maritime Forest Restoration

“…We did not find support for the second predicted interaction that in non-fenced plots, seedlings may perform better in treatments without vegetation control because the competition may act as a Forests 2019, 10, 950 9 of 13 barrier to deer browse [2,28]. This result is likely due to high deer populations, on an isolated barrier island with limited food resources, resulting in high levels of herbivory where most palatable vegetation was browsed [62,67], regardless of Q. virginiana seedlings being obscured by competing vegetation.…”

“…Controlling competition is therefore often deemed necessary following clearcutting. Under specific circumstances, however, a trade-off exists whereby competition may be beneficial to seedlings by acting as a natural shelter to hide seedlings from browsing animals or reducing the negative effects of drought or flooding [2,26,28,29].Identified as regions of physiographical significance, maritime forests along the US Southern Atlantic coast provide major functions and services such as stabilizing soil, recharging groundwater, and biodiversity [30][31][32][33]. Late successional species comprise maritime forests and are dominated by Quercus virginiana Mill.…”

“…However, there are few studies of impacts of deer browse on maritime forests [43]. While browse control techniques can be used (e.g., fencing and tree shelters), these are often logistically and economically prohibitive due to installation and maintenance costs [25,28,44].The Target Plant Concept provides a conceptual framework for forest restoration to increase the likelihood of outplanting success [45]. A component of the concept is to identify and overcome important limiting site factors using site preparation [46].…”

“…Controlling competition is therefore often deemed necessary following clearcutting. Under specific circumstances, however, a trade-off exists whereby competition may be beneficial to seedlings by acting as a natural shelter to hide seedlings from browsing animals or reducing the negative effects of drought or flooding [2,26,28,29].…”

“…However, there are few studies of impacts of deer browse on maritime forests [43]. While browse control techniques can be used (e.g., fencing and tree shelters), these are often logistically and economically prohibitive due to installation and maintenance costs [25,28,44].…”