Browsing regime and growth response of Abies alba saplings planted along light gradients

Abstract

Silver fir is a highly desirable species in European mountain forests from a management and conservation point of view, but it is also highly palatable for ungulates. We planted Abies alba saplings along natural light gradients to explore under natural browsing: (1) the light conditions under which saplings grow best in the absence of browsing; (2) when and by which ungulate species which saplings are browsed; and (3) under which conditions saplings react most vigorously to browsing. The experiment was carried out in a Swiss forest using four fenced plots each containing about 30 saplings planted in 2001, which were between 17 and 100 cm tall in 2009. For half of the saplings, browsing was allowed and filmed from April 2009 to January 2010. Saplings grew better with more light (13 % rather than 10 % canopy openness). Browsing was not a single event per sapling but a continuous process during the winter months. Almost all saplings exposed to browsing suffered heavy browsing by chamois and red deer, but no roe deer browsing was observed. The remainder of the browsed shoots were longer and contained more buds under 13 % canopy openness. The browsinginduced height differences between browsed and unbrowsed trees increased over time under all light conditions, and almost no diameter growth was measured in the years after browsing. In cases with severe browsing, management aimed at letting in more light does not lead to a substantially better tolerance of browsing. We thus recommend integrating the ''feeding strength'' in the assessment of browsing.

Recovery of Abies alba and Picea abies saplings to browsing and frost damage depends on seed source

“…Almost no Abies reacted with the bending upward of a previously existing branch, while for Picea flagging was very common after light and heavy clipping. Generally, flagging seems to be an efficient but rather rare reaction type for Abies saplings (Kupferschmid & Bugmann, ), in particular under natural browsing (Kupferschmid, Wasem, & Bugmann, ). The different reactions of the species to clipping could be caused by the plagiotropic growth of Abies but not Picea branches; that is, Abies follows the architectural model MASSART and Picea follows RAUH (Hallé & Oldeman, ).…”

Selective browsing behaviour of ungulates influences the growth of Abies alba differently depending on forest type

“…The importance of within-tree browsing intensity for Abies sapling growth was even more pronounced than that of forest type, as lightly browsed Abies saplings grew better than unbrowsed saplings in the year of browsing and also in the season after browsing. Generally, conspicuous tree saplings that stand out from the other vegetation are more likely to be browsed than partially obscured plants (Kupferschmid et al, 2015b;Miller et al, 1982). For example, dominant Picea abies saplings in a regeneration cluster were browsed more often than other trees in the cluster (Näscher, 1979).…”

“…Hartley et al, 1997). Larger saplings with a large crown volume have been found to be more likely to be browsed by ungulates (Iason et al, 1996;Kupferschmid et al, 2015b). Moreover, a close relationship between shoot size and bite size has been reported (Danell et al, 1994;Shipley et al, 1999).…”

“…Therefore, it is important to understand interactions between site characteristics and ungulate browsing. Kupferschmid et al (2015b) proposed, based on their experiment, that within-tree browsing intensity -i.e. the amount of tissue ungulates eat, such as leader buds only (decapitation), part(s) of the annual leader shoot, the entire annual leader shoot, or much more than just the annual leader shoot -should be integrated into assessments of browsing in order to better estimate the browsing 3 impact at different sites.…”

Bark Stripping by Deer Was More Intensive on New Recruits than on Advanced Regenerants in a Subalpine Forest

“…Overabundant deer cause serious issues for forest ecosystems by limiting the regeneration of natural forests [3][4][5], damaging planted trees [6][7][8][9][10], and consequently altering the species composition, stand structure, and ecosystem functions of forests [11,12]. These issues are caused mainly by foraging behaviors: stripping of bark from saplings and trees [13][14][15] and browsing on those and understory vegetation [16][17][18]. Bark stripping greatly damages saplings and trees by destroying xylem water conductivity [19] and increasing fungal infection [13].…”