Estuary resilience and recovery following exclusion of a non-native invader, Canada Geese
Presentation Abstract
Estuaries are threatened by non-native resident Canada geese (Branta canadensis, “CAGO”). Excessive grazing and grubbing pressure by CAGO shifts herbaceous marsh habitat to denuded mudflat, leading to marsh recession. The degree to which vegetation and seed banks can recover after CAGO exclusion remains unknown. We compare the recovery trajectory exclosures that are 1 and 10 years old to undisturbed and denuded sites to ask the questions 1) How does CAGO grazing impact species and Plant Functional Groups (PFGs) over time? 2) How do seed banks respond over time since grazing exclusion? 3) Is seed bank composition similar to above-ground species composition? Using mixed effects models and NMDS, we show that 1) Recently grazed sites were dominated by annual species, and had higher proportion of unvegetated ground compared to ungrazed sites. Perennial graminoid cover increased between 1 and 10 years at exclosed sites, however sites exclosed for 10 years had higher cover of non-native graminoid species. 2) Seed abundance was highest in denuded sites dominated by annual species; however, seed species richness did not vary as expected between grazing conditions. 3) Seed bank species composition was most similar to above-ground vegetation in denuded sites dominated by annual species. Excluding geese is an effective method of protecting remnant vegetation; however, these sites may be prone to invasion during the recovery period. Understanding whether management actions facilitate resilience of above-ground vegetation and seed banks is important to inform conservation and restoration best practices.
Session Title
Birds
Conference Track
SSE3: The Circle of Life
Conference Name
Salish Sea Ecosystem Conference (2022 : Online)
Document Type
Event
SSEC Identifier
SSE-traditionals-195
Start Date
28-4-2022 8:30 AM
End Date
28-4-2022 10:00 AM
Type of Presentation
Oral
Genre/Form
conference proceedings; presentations (communicative events)
Subjects – Topical (LCSH)
Canada goose--Migration--Northwest, Pacific; Estuaries--Conservation--Northwest, Pacific; Ecosystem management--Northwest, Pacific; Dams--Environmental aspects--Northwest, Pacific
Geographic Coverage
Northwest, Pacific
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Type
Text
Language
English
Format
application/pdf
Estuary resilience and recovery following exclusion of a non-native invader, Canada Geese
Estuaries are threatened by non-native resident Canada geese (Branta canadensis, “CAGO”). Excessive grazing and grubbing pressure by CAGO shifts herbaceous marsh habitat to denuded mudflat, leading to marsh recession. The degree to which vegetation and seed banks can recover after CAGO exclusion remains unknown. We compare the recovery trajectory exclosures that are 1 and 10 years old to undisturbed and denuded sites to ask the questions 1) How does CAGO grazing impact species and Plant Functional Groups (PFGs) over time? 2) How do seed banks respond over time since grazing exclusion? 3) Is seed bank composition similar to above-ground species composition? Using mixed effects models and NMDS, we show that 1) Recently grazed sites were dominated by annual species, and had higher proportion of unvegetated ground compared to ungrazed sites. Perennial graminoid cover increased between 1 and 10 years at exclosed sites, however sites exclosed for 10 years had higher cover of non-native graminoid species. 2) Seed abundance was highest in denuded sites dominated by annual species; however, seed species richness did not vary as expected between grazing conditions. 3) Seed bank species composition was most similar to above-ground vegetation in denuded sites dominated by annual species. Excluding geese is an effective method of protecting remnant vegetation; however, these sites may be prone to invasion during the recovery period. Understanding whether management actions facilitate resilience of above-ground vegetation and seed banks is important to inform conservation and restoration best practices.
