Table 1 List of variables to code from the studies, including key sources of heterogeneity known to influence the effects of herbivores on tundra ecosystems

Article ID

author_list

List of authors

P

title

Title of the publication

P

year

Year of publication

P

journal

Journal or publishing house

P

language

Language of the publication

P

study_ID

Unique ID number for study

C

searchable_pdf

Whether the document allows for automated text searches

P

Study location

country

Country or region name

P

locality

Site name describing the locality, as specified in the study

P

coordinate_source

Whether coordinates are provided in the text, based on maps, figures or place names

P

coordinates_N, coordinates_E

Geographic coordinates in decimal degrees

P

elevation

Elevation (m a.s.l.)

P

elevation_DEM

Elevation (m a.s.l.) extracted from digital elevation model

D

Study type

study_design

Whether the study involves experimental manipulations, observational approaches or whether the study design is unclear

C

diversity_contrast

Approach used to create or assess the difference in herbivore diversity, such as exclosures or spatial contrasts

C

size_selective_exclosures

Does the study use different exclosures that prevent access of different sized herbivores?

C

spatial_extent

Size of the study area

C

spatial_resolution

Spatial scale at which the outcome is reported for each study

C

temporal_resolution

Interval between measurements of the outcome

C

sampling_frequency

Frequency of measurements

C

year_start

Year when the study started

P

year_end

Year when the study finished

P

Exposure and comparator

herbivore_data

How is the composition of the herbivore assemblages assessed?

C

herbivore_ID_higher_diversity

Species (or group) list in the areas with higher herbivore diversity

P

herbivore_ID_lower_diversity

Species (or group) list in the areas with lower herbivore diversity

P

Outcome

measured_response_variable

What was measured in areas exposed to different herbivore diversity?

P/C

reported_units

Units in which the response variable is reported; "unitless" if there is no unit

P

value_higher_diversity

Value of the outcome in the higher diversity area

P

value_lower_diversity

Value of the outcome in the lower diversity area

P

value_type

Does the value refer to the mean, median, etc

P

variability_higher_diversity

Variability of the outcome in the higher diversity area

P

variability_lower_diversity

Variability of the outcome in the lower diversity area

P

variability_type

Type of variability measurement (SE, confidence intervals (CI), etc.)

P

sample_size_higher_diversity

Number of observations in the higher diversity area

P

sample_size_lower diversity

Number of observations in the lower diversity area

P

effect_size

Value of the comparison between areas with different diversity

P

effect_size_variability

Variability of the comparison

P

effect_size_variability_type

Type of variability measurement (SE, confidence intervals (CI), etc.)

P

effect_size_direction

Direction of the comparison, or unclear

C

effect_size_sample_size

Number of observations for the comparison if reported

P

effect_size_type

Type of comparison (e.g. model estimate)

C

effect_size_comments

Any additional comments

C

statistical_test

Type of statistical test reported (e.g. paired t-test)

P

statistical_test_value

Value of the test statistic

P

statistical_test_df

Degrees of freedom of the statistic

P

statistical_test_p

p-value of the statistical test

P

outcome_comments

Any additional comments

C

more_data

Is there data available in the paper that is not extractable in its current form?

C

Study validity assessment

bias_risk_criterion1

Biases due to uncontrolled confounding variables that influence both the herbivore diversity levels and the response variable

C

bias_risk_criterion2

Biases arising from systematic differences in the selection of areas into the study or analyses after treatment

C

bias_risk_criterion3or4

Biases arising from misclassification or measurement of contrasts of herbivore diversity (observational studies) or treatments (experimental studies)

C

bias_risk_criterion5

Biases arising from systematic differences in measurements of outcomes

C

bias_risk_criterion6

Biases in reporting of study findings

C

bias_risk_criterion7

Biases due to error in applied statistical methods

C

bias_risk_comments

Please indicate any relevant comments; if there were confounding variables please report them here

C

Context

distance_to_treeline

Distance (km) to southern border of arctic subzone E

D

distance_from_coast

Distance (km) to the coast

D

bioclimatic_zone

Bioclimatic zone A to E, or "other"

D

temperature

Temperature related variable(s) extracted from WorldClim

D

precipitation

Precipitation related variable(s) extracted from Worldclim

D

growing_season

Duration of growing season (days)

D

productivity

Value of NDVI (vegetation greenness)

D

recent_warming

Extent of recent warming

D

recent_greening

Extent of recent greening

D

extent_of_recent__change

Extent of recent change in growing season length

D

soil_chemistry

Soil chemistry

C

soil_texture

Broad categories of soil texture

C

soil_moisture

Soil moisture as described in the study

C

soil_type

Soil type as reported by the authors

P

soil_type_D

Soil type

D

permafrost

Presence of permafrost

C

permafrost_D

Presence of permafrost

D

habitat_type

Habitat types using the broad categories defined in CAVM

C

habitat_type_D

Habitat types

D

management_focus

Whether the study is framed within a management context

C

conservation_focus

Whether the study is framed within a conservation context

C