Winter browsing by moose (Alces alces) in a forested mountainous landscape of West-Central Sweden
Data files
Mar 19, 2025 version files 19.84 MB
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Dryad_Data_-_1.csv
202.67 KB
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Dryad_ModelingSASindata.xlsx
19.62 MB
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README.md
23.94 KB
Abstract
Browsing ecology involving ungulates and their food resource is complex as consumption may reflect responses to various factors, such as quantity and quality of browse species. This study investigated winter browsing by moose (Alces alces) in a mountainous landscape of west-central Sweden, characterized by Norway spruce (Picea abies) production forests with high inclusion of deciduous species. Field data on tree species abundances as well as fresh and previous browsing were collected along moose tracks and control transects, to answer our questions regarding browse selection in relation to availability. The data were analyzed using mainly modelling (Generalized linear mixed models) approaches. The results revealed greater amounts of available food trees (<5 m) in young compared to older forests and along moose tracks compared to control transects. Downy birch (Betula pubescens) was the most abundant independent of forest age class and transect type (i.e. tracks vs. controls). Quantitatively, the key winter browse in the study area was a mix of deciduous species, primarily downy birch and willows (Salix spp.) complemented by Eurasian aspen (Populus tremula) and grey alder (Alnus incana). In young forest, aspen, rowan (Sorbus aucuparia) and willows were the most selected species, while common juniper (Juniperus communis) was the least selected. In older forest, alder was most selected, followed by willows and rowan, while aspen and downy birch were the least selected, except for spruce and lodgepole pine (Pinus contorta). According to Jacobs selectivity index, downy birch, was underused while aspen, rowan and willows were overused in relation to their frequencies. The latter are often limited in today’s cultivated forest landscape and thus an increased amount of those species may be utilized to a higher degree by moose than an increase of downy birch. No effect from snow depth was detected and browsing on dwarf shrubs was not observed.
Dataset DOI: 10.5061/dryad.5mkkwh7dz
Description of the data and file structure
Data on browsing patterns of moose on snow-covered ground collected in west-central Sweden.
Files and variables
File: Dryad_ModelingSASindata.xlsx
Description:
Explanations of data sheets in Dryad_ModelingSASindata.xls. Each sheet is based on data from Dryad_Data – 1.csv, but formatted for analyses of different scales in SAS.
| Name of sheet | Selection of transects | Scale of data | Selection of trees | Description |
|---|---|---|---|---|
| Alltransects_transects | All transects | Transect scale | All trees | Summarized data based on all transects (24) |
| Moosetracks_transects | Moose tracks only | Transect scale | All trees | Summarized data based on moose track transects (16) |
| Alltransects_trees | All transects | Tree scale | All trees | Data for each individual tree on all transects (1920) |
| Moosetracks_trees | Moose tracks only | Tree scale | All trees | Data for each individual tree on moose track transects (1289) |
| Alltransects_transects_No5s | All transects | Transect scale | Trees <5 m | Summarized data based on all transects (24) excluding trees over 5 meters |
| Alltransects_transects_5s | All transects | Transect scale | Trees >5 m | Summarized data based on all transects (23) excluding trees under 5 meters |
| Moosetracks_transects_No5s | Moose tracks only | Transect scale | Trees <5 m | Summarized data based on moose track transects (16) excluding trees over 5 meters |
| Moosetracks_transect_5s | Moose tracks only | Transect scale | Trees >5 m | Summarized data based on moose track transects (14) excluding trees under 5 meters |
| Alltransects_trees_No5s | All transects | Tree scale | Trees <5 m | Data for each individual tree on all transects excluding trees over 5 meters (1684) |
| Alltransects_trees_5s | All transects | Tree scale | Trees >5 m | Data for each individual tree on all transects excluding trees under 5 meters (236) |
| Moosetracks_trees_No5s | Moose tracks only | Tree scale | Trees <5 m | Data for each individual tree on moose track transects excluding trees over 5 meters (1155) |
| Moosetracks_trees_5s | Moose tracks only | Tree scale | Trees >5 m | Data for each individual tree on moose track transects excluding trees under 5 meters (134) |
| Species_Mt_tr_No5s | Moose tracks only | Tree scale | Trees <5 m | Data for each individual food tree (no spruce or contorta) on moose track transects organized by species excluding trees over 5 meters (1005) |
| Jacobsindex | Moose tracks only | Transect scale | Trees <5 m | Data for calculating Jacobs selectivity index |
Explanations of variables in Dryad_ModelingSASindata.xls. Not all variables appear on every sheet.
| Variable | Format | Unit | Explanation |
|---|---|---|---|
| Runno | 1, 2, 3, etc | Run number | |
| Transect_no | 1, 2, 3, etc | Unique number for every transect | |
| Area | text | Name of transect (based on location), for reference | |
| Date | 22-01-07 | Date for survey | |
| Length / T_length | 50 | m | Length of transect, usually 50 - otherwise 25 m |
| Moose_track | 0/1 | Type of transect | |
| Control | 0/1 | Type of transect | |
| Young_forest | 0/1 | Type of transect | |
| Older_forest | 0/1 | Type of transect | |
| Snow_depth | 0, 1, 2, 3, etc | cm | Average of 3-5 representative measurings along each transect |
| Shrub_cov | 10, 20, 30 etc | % | Estimation of % of transect with visable dwarf shrubs (nearest 10%) |
| Browsing_shrub | 1, 2, 3, etc | Number of observed browsing events of dwarf shrubs along moose track | |
| Cross_tracks | 1, 2, 3, etc | Number of crossing moose tracks along transect | |
| Tree_ID | 01012 | Unique number for each tree: e.g. 01 = first transect, 012 = 12:th tree | |
| Tree_species | 1, 2, 3, etc | pine = 1, spruce = 2, downy birch = 3, silver birch = 4, aspen = 5, rowan = 6, willows = 7, alder = 8, juniper=9, lodgepole=10 | |
| Sp_name | text | Species name | |
| Height | 1, 1.5, 2, etc | m | Height of tree, nearest 0.5 m |
| B_height | 0/1 | Tree within browsing height | |
| TS_browsed | 0/1 | Top shoot browsed or not (only applicable for conifers) | |
| Shoots_browsed | 0, 1, 2, 3, etc | Number of browsed side shoots | |
| Fresh_browsing | 0/1 | Freshly browsed or not | |
| Proc_browsed | 10, 20, 30 etc | % | Estimation of percentage of shoots freshly browsed |
| Prop_browsed | 0.01, 0.02, 0.03 etc | Estimation of proportion of shoots freshly browsed | |
| Tot_Shoots | 0, 1, 2, 3, etc | Sum of browsed shoots | |
| Tot_UBShoots | 0, 1, 2, 3, etc | Sum of unbrowsed shoots (estimated from Sum of browsed shoots and Estimation of % of shoots browsed) | |
| Prev_browsed | 0/1 | Is there previous browsing on the tree | |
| Ch_direct | 0/1 | Has there been a change of direction before the tree (should be read backward for analysis, since animals are tracked in opposite direction) | |
| Height_noSP | 1, 1.5, 2, etc | m | Height of tree, nearest 0.5 m excluding spruce |
| 5m | 0/1 | Is the tree over 5 m | |
| Only transect scale: | |||
| Type | text | Moose_track or Control | |
| Forestage | text | Older_forest or Young_forest | |
| Cross_tracks_ALL | 1, 2, 3, etc | Number of crossing deer tracks along transects (all species) | |
| alder | 1, 2, 3, etc | Number of individuals | |
| aspen | 1, 2, 3, etc | Number of individuals | |
| downy_birch | 1, 2, 3, etc | Number of individuals | |
| juniper | 1, 2, 3, etc | Number of individuals | |
| lodgepole | 1, 2, 3, etc | Number of individuals | |
| pine | 1, 2, 3, etc | Number of individuals | |
| rowan | 1, 2, 3, etc | Number of individuals | |
| Salix | 1, 2, 3, etc | Number of individuals | |
| spruce | 1, 2, 3, etc | Number of individuals | |
| GT | 1, 2, 3, etc | Grand total - number of individuals, species pooled | |
| GT_nospruce | 1, 2, 3, etc | Grand total - number of individuals, species pooled excluding spruce | |
| Trees_FB | 1, 2, 3, etc | Number of individuals with fresh browsing | |
| Prop_TFB | 0.01, 0.02, 0.03 etc | Proportion of individuals with fresh browsing | |
| Trees_PB | 1, 2, 3, etc | Number of individuals with previous browsing | |
| Shoots_FB | 1, 2, 3, etc | Number of shoots with fresh browsing | |
| Proc_ShB | 0.01, 0.02, 0.03 etc | % | Estimation of percentage of shoots freshly browsed |
| Tot_UBshoots | 0.01, 0.02, 0.03 etc | Estimation of number of shoots without fresh browsing | |
| Direction | 1, 2, 3, etc | Number of direction changes along track (minimum 60 degree turn within 2 meters) | |
| *species name*(J.I.) | 0.01, 0.02, 0.03 etc | Jacobs selectivity index value for each species |
* Variable names on sheet “Species_Mt_tr_No5s” have the species name at the beginning of each variable, but the remainder of the name corresponds to variables found in the list above and represents the same for the species in question.
File: Dryad_Data_-_1.csv
Description:
Explanations of variables in file DryadData – 1.csv
| Variable | New name | Format | Unit | Explanation |
|---|---|---|---|---|
| Runno | Runno | 1, 2, 3, etc | Run number | |
| Transect no | Transect_no | 1, 2, 3, etc | Unique number for every transect | |
| Area | Area | text | Name of transect (based on location), for reference | |
| Date | Date | 22-01-07 | Date for survey | |
| Length | Length | 50 | m | Length of transect, usually 50 - otherwise 25 m |
| Moose track | Moose_track | 0/1 | Type of transect | |
| Control | Control | 0/1 | Type of transect | |
| Young forest | Young_forest | 0/1 | Type of transect | |
| Older forest | Older_forest | 0/1 | Type of transect | |
| Snow depth | Snow_depth | 1, 2, 3, etc | cm | Average of 3-5 representative measurings along each transect |
| Shrub | Shrub_cov | 10, 20, 30 etc | % | Estimation of % of transect with visable dwarf shrubs (nearest 10%) |
| Browsing shrub | Shrub_browsed | 1, 2, 3, etc | Number of observed browsing events of dwarf shrubs along moose track | |
| Cross tracks | Cross_tracks | 1, 2, 3, etc | Number of crossing moose tracks along transect | |
| Tree ID | Tree_ID | 01012 | Unique number for each tree: e.g. 01 = first transect, 012 = 12:th tree | |
| Tree species | Tree_species | 1, 2, 3, etc | pine = 1, spruce = 2, downy birch = 3, silver birch = 4, aspen = 5, rowan = 6, willows = 7, alder = 8, juniper=9, lodgepole=10 | |
| Species name | Sp_name | text | Species name | |
| Height | Height | 1, 1.5, 2, etc | m | Height of tree, nearest 0.5 m |
| B_height | B_height | 0/1 | Tree within browsing height | |
| Top sprig browsed | Apical_browsing | 0/1 | Top shoot browsed or not | |
| Side sprig browsed | Lateral_browsing | 0, 1, 2, 3, etc | Number of browsed side shoots | |
| Fresh_browsed | Fresh_browsing | 0/1 | Freshly browsed or not | |
| Amount browsing | Proc_browsing | 5, 10, 15, etc | % | Estimation of % of shoots freshly browsed |
| Browsed shoots | No_browsed_shoots | 0, 1, 2, 3, etc | Sum of browsed shoots | |
| Unbrowsed shoots | No_unbrowsed_shoots | 0, 1, 2, 3, etc | Sum of unbrowsed shoots (estimated from Sum of browsed shoots and Estimation of % of shoots browsed) | |
| Previously browsed | Previous_browsing | 0/1 | Is there previous browsing on the tree | |
| Change of direction | Direction_change | 0/1 | Has there been a change of direction before the tree (should be read backward for analysis, since animals are tracked in opposite direction) | |
| Comment | Comment | text | Comments |
For information on data collection and study system, see submission by Hambeson et al.
The statistical analyses were performed using SAS 9.4 (SAS Institute Inc., 2016) and specifically Chi square test (using PROC FREQ) and generalized linear mixed model (GLMM, using PROC GLIMMIX) in SAS.
Scripts are given in Dryad_Scripts SAS.doc
Explanations of analyses are given individually for each analysis, e.g.
*testing number of pine > 5 m along moose tracks vs controls and forest type - *;
PROC GLIMMIX data=WORK.Alltransects_transects_5s;
CLASS T_length Young_forest Moose_track;
MODEL pine = Young_forest Moose_track Young_forest*Moose_track/dist=Poisson link=log;
RANDOM T_length;
LSMEANS Young_forest Moose_track / cl ilink plots=mean(ilink cl);
TITLE ‘No. pine > 5 m along transects’;
RUN;
Jacobs selectivity index (formula described in Hambeson et al.) was calculated using the total from the columns species name_Fresh_brow from the sheet “Species_Mt_tr_No5s” (representing proportion of use) and the total number of individuals of the species under 5 meters (representing proportion of the total availability of trees).