DOI: 10.5061/dryad.fj6q573xg
title: The proximity of rapeseed fields influences levels of forest damage by red deer

description: We investigated the relationship between the level of red deer Cervus
 elaphus bark stripping damage in 68 Norway spruce Picea abies stands, and
 the presence of rapeseed Brassica napus fields in the surroundings,
 hypothesising that damage increases with decreasing distance to rapeseed
 fields. We also considered other potentially influencing factors, such as
 supplemental feeding, alternative forage availability, and deer use of
 spruce stands as indexed by a pellet group count. Bark stripping rates
 were measured in 68 planted stands of Norway spruce with a minimum size of
 1 ha and an age interval of 20-40 years. We selected, a priori, stands in
 forestry plans with a minimum of 80 % spruce. However, all stands were
 planted even-aged monocultures where cleaning of deciduous species had
 occurred at younger stages, resulting in a spruce proportion generally
 close to 100 %.  In each stand, 10 circular 100 m2 survey plots
 were systematically and evenly distributed (with a random starting point).
 Occurrence of fresh bark-stripping damage (i.e., wounds from preceding
 winter) was noted for the 10 spruce stems closest to the plot centre
 (i.e., 100 spruce stems per stand). We measured the distance from the
 rapeseed fields and feeding stations to the spruce stands by using QGIS.
 An index of relative forage availability was measured by estimating
 percent living vegetation cover of woody browse projected onto the
 horizontal plane in 20 m2 subplots within targeted stands (the same 10
 plots per stand as for the damage survey) and in the surrounding landscape
 in plots distributed along 500 m transects, one in each of the cardinal
 directions from the targeted stand (plots distributed at 0, 100, 200, 300,
 400, and 500 m from the stand edge (0 m) making a total of 24 transect
 plots per stand). The number of red deer pellet groups were counted within
 targeted spruce stands and in the surrounding landscape to provide indices
 of relative deer stand usage and overall abundance respectively. Pellet
 groups were surveyed in 100 m2 circular plots within the stands (the same
 plots as for damage and forage survey) and in the transect plots used for
 forage survey described above. Only fresh (from preceding winter) pellet
 groups were counted. Spruce stands closer to rapeseed had a significantly
 higher proportion of damaged stems. The increased level of bark stripping
 damage was not explained by a higher deer stand use closer to rapeseed
 fields. Spruce stands closer to supplemental feeding stations had
 significantly higher damage levels. Damage levels were negatively related
 to the amount of available browse in the forest.
description: <strong>Description of
 methods used for collection/generation of data: </strong>Bark
 stripping rates were measured in 68 planted stands of Norway spruce with a
 minimum size of 1 ha and an age interval of 20-40 years. We selected, a
 priori, stands in forestry plans with a minimum of 80 % spruce. However,
 all stands were planted even-aged monocultures where cleaning of deciduous
 species had occurred at younger stages, resulting in a spruce proportion
 generally close to 100 %.  In each stand, 10 circular 100 m2 survey plots
 were systematically and evenly distributed (with a random starting point).
 Occurrence of fresh bark-stripping damage (i.e., wounds from preceding
 winter) was noted for the 10 spruce stems closest to the plot centre
 (i.e., 100 spruce stems per stand). We measured the distance from the
 rapeseed fields and feeding stations to the spruce stands by using QGIS.
 An
 index of relative forage availability was measured by estimating percent
 living vegetation cover of woody browse projected onto the horizontal
 plane in 20 m2 subplots within targeted stands (the same 10 plots per
 stand as for the damage survey) and in the surrounding landscape in plots
 distributed along 500 m transects, one in each of the cardinal directions
 from the targeted stand (plots distributed at 0, 100, 200, 300, 400, and
 500 m from the stand edge (0 m) making a total of 24 transect plots per
 stand). The number of red deer pellet groups were
 counted within targeted spruce stands and in the surrounding landscape to
 provide indices of relative deer stand usage and overall abundance
 respectively. Pellet groups were surveyed in 100 m2 circular plots within
 the stands (the same plots as for damage and forage survey) and in the
 transect plots used for forage survey described above. Only fresh (from
 preceding winter) pellet groups were counted.
 Spruce stands closer to
 rapeseed had a significantly higher proportion of damaged stems. The
 increased level of bark stripping damage was not explained by a higher
 deer stand use closer to rapeseed fields. Spruce stands closer to
 supplemental feeding stations had significantly higher damage levels.
 Damage levels were negatively related to the amount of available browse in
 the forest. (Jarnemo A,
 Widén A, Månsson J, Felton A M. 2022. The proximity of rapeseed fields
 influences levels of forest damage by red deer. Ecological Solutions and
 Evidence.) <strong>Methods for processing the data:
 </strong>All the
 data collected was put into excel after the inventory was done in the
 field. We used the number of undamaged and damaged tree stems in the
 stands as response variable, thus this variable was not processed or
 changed from the raw data collected. We took an average number of the red
 deer pellet groups that was found in the stands, thus an average of the 10
 plots inventoried per stand. The same was done with the pellet groups
 measured along the transects surrounding the stands. Thus, we took an
 average number of fresh red deer pellet groups found along the 4 transects
 surrounding the stand (average of the 24 transect plots surrounding
 the spruce stand). The forage availability measured in the spruce
 stands and along the transects were processed before using the data. We
 first pooled the field layer and shrub layer data into an forage layer
 variable. Then we took the average of the forage layer per stand, thus the
 average of the 10 plots in each stand. The same was done for the 4
 transects surrounding the field, where we took the average forage layer of
 the 4 transects (average
 of the 24 transect plots surrounding the spruce
 stand).
 The
 distance to closest rape seed field was not processed, it is simply just
 the distance from the spruce stand edge to the closest rape seed field in
 kilometers. The same is done with the distance to the closest feeding
 station. <strong>Instrument- or software-specific information
 needed to interpret the data: </strong>We measured the distance from the rapeseed
 fields and feeding stations to the spruce stands by using
 QGIS,
  otherwise no ecific
 software was used to generate the data. Later, all analyses were carried out in R (version
 4.0.0). We used generalized mixed effects models (GLMMs, function glmer in
 lme4 package, (Bates et al. 2015)) with binomial distribution to model
 bark-stripping damage. We adopted a stepwise deletion approach and
 verified the removal of variables with likelihood ratio tests (function
 lrtest in package lmtest). All models were checked for basic assumptions
 of normality and heterogeneity of residuals using the Dharma package in R
 (Hartig, 2016). <strong>Standards and calibration information, if
 appropriate:  </strong>not appropriate
 <strong>Describe any
 quality-assurance procedures performed on the data:
 </strong>The data
 was collected by a team of members that were educated in how the data
 should be collected, we followed already established protocols used by
 earlier studies in the field. Thus the methods have been used before and
 are quality assured. Before the data was used in any final
 statistical model it was checked for basic assumptions of normality and
 heterogeneity of residuals using the Dharma package in R (Hartig,
 2016). <strong>People involved with sample
 collection, processing, analysis and/or submission:</strong> Anders
 Jarnemo, Anna Widén, Johan Månsson, Annika M
 Felton.