DOI: 10.5061/dryad.rjdfn2zn0
title: Ornithogenic alteration of a tundra ecosystem from decades of intense herbivory and dense nesting

description: Migratory animals can serve as ecological links between geographically
 distant ecosystems. Moreover, when seasonally linked ecosystems differ in
 carrying capacity of migrant species, those with high capacity may support
 population growth with consequences to shared ecosystems with lower
 capacity through trophic cascades. Agricultural production has increased
 carrying capacity of lesser snow (Anser caerulescens caerulescens) and
 Ross’s geese (Anser rossii, collectively, ‘light geese’) in southern
 agricultural landscapes where these species winter and stage during
 migration to and from northern breeding areas, resulting in population
 increase. In subarctic and arctic ecosystems where carrying capacity for
 geese is lower, high abundance and densities of light geese have caused
 trophic cascades during summer breeding. This has raised concern for
 resilience of northern ecosystems to withstand cumulative and intense
 pressures of above- and below-ground herbivory and nest construction. We
 investigated the empirical relationship between intensity of vegetation
 disturbance by multidecadal foraging and nest construction by up to ~1.3
 million geese and shifts in (i) plant community composition and (ii) taxon
 richness of freshwater plant communities near Karrak Lake, in Canada’s
 central arctic. Intense use by nesting light geese caused shifts from
 lowland communities dominated by grasses and sedges (collectively,
 graminoids), Sphagnum spp., and willows (Salix spp.) to those comprised of
 exposed peat, non-Sphagnum mosses, marsh ragwort (Tephroseris palustris),
 mare’s tail (Hippuris vulgaris), and particularly birch (Betula
 glandulosa). Community change was less apparent in upland regions that
 were naturally less vegetated even in the absence of avian herbivores, but
 fruticose lichens, crowberry (Empetrum nigrum) and white heather (Cassiope
 tetragona) dominated undisturbed plant communities whereas crustose
 lichens and bearberry (Arctostaphylos spp.) comprised disturbed
 communities. We did not find evidence for dominance by a limited number of
 species with long-term occupancy by light geese, as taxon richness was
 equivocal between disturbed and undisturbed plant communities. Cessation
 of foraging and nesting pressure increased taxon richness and
 reestablishment of locally eradicated plant species. Overall, herbivory
 and nesting effects were not uniform across this widespread nesting
 colony, and together with underlying influence from abiotic gradients,
 increased heterogeneity in the mosaic of vegetation communities.
description: # Ornithogenic alteration of a tundra ecosystem from decades of intense
 herbivory and dense nesting
 [https://doi.org/10.5061/dryad.rjdfn2zn0](https://doi.org/10.5061/dryad.rjdfn2zn0) ## Description of the data and file structure **Description of the data and file structure** Vegetation data collected at Karrak Lake, Nunavut over three years: 1998, 2014, and 2017. We have submitted two data files: 'MARK_multistate.xlsx' is an input file for the software MARK for a multistate analysis investing habitat change on sample plots between 1998 and 2014, and 'all17GwElev_from_R_2020_01_13.xlsx' contains point intersect vegetation data analysed in R. ### Files and variables #### File: MARK\_multistate.xlsx **Description:** habitat state change on plots between 1998 and 2024 ##### Variables * the first, third, and ninth columns are syntax required for MARK input files * second column: plot name: a unique identifier for the plot * fourth column: encounter history: first letter represents plot habitat in 1998, second letter represents plot habitat in 2014 (U=upland, G=graminoid, B=birch). For example, an encounter history of GB means that the plot was classified as graminoid habitat in 1998 and birch habitat in 2014. An encounter history of BB means that the plot was classified as birch habitat in both 1998 and 2014. * fifth column: frequency of occurrence of a record with that specific encounter history and associated variables: each record is unique so all equals 1 * sixth column: mean number of goose nests on plot. This is a continuous variable. * seventh column: number of years that a specific plot was inside the goose nesting colony perimeter. This is a continuous variable. * eighth column: number of years since goose colony retraction. In some part of the colony (particularly the south), the colony perimeter retracted in later years of the study. This is a continuous variable. Most values are zero as most sample plots were located within the goose colony for the duration of 1998 to 2014.  #### File: all17GwElev\_from\_R\_2020\_01\_13.xlsx **Description:**  point intersect vegetation data on sample plots in 2017. ##### Variables * plot: plot name: a unique identifier for the plot. * date: the date (year-month-day) the plot was visited and vegetation and habitat data were recorded. All data were recorded in 2017. * P1 through P60: a 4-letter code describing vegetation or habitat code at point-intersect. Codes and descriptions are provided below. Vegetation/habitat were sampled at 50 cm intervals, so P1 = 50 cm from plot center, P2 = 1 m from plot center....and so on out to a distance of 30 m from plot center. * SOIL through GODR: the number of occurrences of each vegetation or habitat type on a given plot. For example, SOIL = 3 means that of 60 point intersect records, 3 were habitat SOIL. Codes and descriptions are provided below and match those of variables P1 through P60. This is a continuous variable.  * crds_x1: UTM easting of sample plot. * crds_x2: UTM northing of sample plot. | common name | field code | description or scientific name | | :---------------------------- | :--------- | :------------------------------------------- | |   water | WATE |   | |   bedrock | BEDR |   large outcrops | |   boulder | BOUL |   greater than 1' diameter | |   cobble | COBB |   less than 1' diameter | |   pebble | PEBB |   &gt; 50% less than 1 cm diameter | |   gravel | GRAV |   &gt; 50% greater than 1 cm diameter | |   sand | SAND |   | |   clay | CLAY |   | |   soil | SOIL |   | |   peat | PEAT |   dead moss, usually Sphagnum | |   moss, Sphagnum | SPHA |   live moss, Sphagnum | |   moss carpet | MOCA |   live moss, very thin layer | |   mosss other | MOOT |   live moss, other than SPH or MOCA | |   lichen, crustose | LICRUST |  crust or scale (tiny lobes) lichen, on soil | |   lichen, foliose | LIFOL |  foliose lichen - with flattened 'leaves' | |   lichen, fruticose | LIFRUT |  fruticose lichen - shrubby, tufted | |   lichen, club | LICUP |  club lichens - stumpy, often with 'cups' | |   graminoids | GRAM | grasses and sedges | |   birch | BIRC |   Betula glandulosa | |   willow small | WILS |   Salix spp.; single leaves | |   willow medium | WILM |   Salix spp.; branching but prostrate | |   willow large (B=big) | WILB |   Salix spp.; bush-like, similar to birch | |   arctic heather | HEAT |   Cassiope tetragona | |   bearberry | BEAR |   Arctostaphylos spp. | |   blueberry | BLUE |   Vaccinium uliginosum | |   bog rosemary | BORO |   Andromeda polifolia | |   cloudberry | CLOU |   Rubus chamaemorus | |   cranberry | CRAN |   Vaccinium vitis-idaea | |   crowberry | CROW |   Empetrum nigrum | |   saxifrage | SAXIB |   Saxifraga spp. | |   moss-campion | MCAM |   Silene acaulis | |   labrador tea | LABT |   Ledum palustre | |   mare's tail | MATA |   Hippuris vulgaris | |   marsh cinquefoil | MACI |   Comarum palustre | |   mountain avens | MOAV |   Dryas integrifolia | |   purple rattle and lousewort | PEDI |   Pedicularis lanata, lapponica, sudetica | |   ragwort | RAGW |   Tephroseris palustris | |   vetch | VETC |   Astragalus, Lathyrus, Oxytropis | |   wintergreen | WINT |   Pyrola spp. | |   goose nest | NEST |   | |   goose dropping | GODR |   | ## Code/software Microsoft Excel Program MARK. Citation: White, G. C., and K. P. Burnham. 1999. Program MARK: Survival estimation from populations of marked animals. Bird Study 46:120-138. ## Access information Other publicly accessible locations of the data: * Other publicly accessible locations of the data: * on Dryad for previous publication: [https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.4275](https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecs2.4275)