BMC Ecol. 2017 Apr 4;17(1):12. doi: 10.1186/s12898-017-0122-3.
- 1
- Department
of Forestry and Wildlife Management, Faculty of Applied Ecology and
Agricultural Sciences, Inland Norway University of Applied Sciences, Pb
400, 2418, Elverum, Norway. karen.mathisen@inn.no.
- 2
- School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK.
- 3
- Department
of Forestry and Wildlife Management, Faculty of Applied Ecology and
Agricultural Sciences, Inland Norway University of Applied Sciences, Pb
400, 2418, Elverum, Norway.
Abstract
BACKGROUND:
Plant
strategies to resist herbivory include tolerance and avoidance.
Tolerance strategies, such as rapid regrowth which increases the
palatability of new shoots, can lead to positive feedback loops between
plants and herbivores. An example of such a positive feedback occurs
when moose
(Alces alces) browse trees in boreal forests. We described the degree of
change in tree morphology that accumulated over time in response to
repeated browsing by moose,
using an index of accumulated browsing. We evaluated whether
accumulated browsing could predict the probability and extent of current
browsing across woody species in a Norwegian boreal forest, and how our
accumulated browsing index related to changes in tree height, shoot
availability and shoot size.
RESULTS:
The
probability and extent of current browsing increased with the degree of
accumulated browsing in all tree species. Plants highly modified by
previous browsing were the most attractive, with no indication of
decreased preference with repeated browsing over time. The preference
for previously browsed trees is most likely driven by increased relative
availability of shoots within browsing height and maybe increased
palatability. This response to previous browsing was general for both
preferred and avoided forage species, in both conifers and deciduous
trees.
CONCLUSIONS:
Our
results suggest that the adaptation for rapid regrowth after browsing
does not reduce herbivory on trees. Rather, our results indicate that
plant responses to browsing increase the probability of future
herbivory. This response could potentially lead to higher plant
mortality where cervid populations are maintained at stable high
densities and has implications for plant population dynamics and
forestry practices.
KEYWORDS:
Accumulated browsing; Alces alces; Brooming; Compensatory growth; Height; Palatability; Regrowth; Tolerance
