Cover it up! Using plants to control buckthorn Early lessons for - PDF document

6/4/2018 Cover it up! Using plants to control buckthorn Early lessons for Minnesota Mike Schuster, Peter Wragg, Peter Reich, Lee Frelich Department of Forest Resources University of Minnesota Alex Roth Friends of the Mississippi River Paul Bockenstedt Stantec, Inc. Shawn Schottler St. Croix Watershed Research Station Ann Pierce Minnesota Department of Natural Resources Buckthorn fundamentally changes forests • Forms dense stands • Decreases native diversity – Forest structure – Animal forage and habitat – Nutrient cycling • Feedback loops with earthworms Buckthorn removal is insufficient • Up to $2,000 per acre • Incomplete removal or lack of follow‐up means buckthorn returns quickly and vigorously • Little benefit of removal within a few years Page 1 of 10 Agenda Item: 10 1

6/4/2018 Challenges of Removal There are some ways to control buckthorn but they are very expensive and/or cannot be used in all places Repeated burning Repeat removal Page 2 of 10 Agenda Item: 10 2

6/4/2018 Buckthorn is shade‐tolerant, but still needs some light Canopy Shade Understory Shade How can we re‐vegetate forests to move them into Suppression or Exclusion zones? Canopy Shade Understory Shade Re‐vegetation is common in grasslands, but not in forests B) Reveg. C) Invader A) System Type Growth Form Growth Form 40 Support Some Support No Support 30 # publications 20 10 0 d d s y s y u d u d n n a a o o o o l l e o e o s d c W c W s o a a a o b b r W G r r e e H H Schuster et al. 2018 Page 3 of 10 Agenda Item: 10 3

6/4/2018 Identifying an effective re‐vegetation method to control buckthorn means… • Cost and labor savings for managers and funders • Reduced herbicide applications • Increased forest health and diversity • Increased value of forests for wildlife and people How do different light environments affect buckthorn? Experiment in Cloquet, MN Canopy species combinations create a light gradient Canopy Shade Page 4 of 10 Agenda Item: 10 4

6/4/2018 Conifers create denser shade than broadleafs 2+ years of buckthorn growth is sensitive to shading Buckthorn juvenile mortality also increases with shading Page 5 of 10 Agenda Item: 10 5

6/4/2018 Conifer canopies offer strongest buckthorn suppression Lesson for Minnesota Species are not equal in their ability to create shade Managers may need to plant something different than what is already present on‐site How can these principles be applied via re‐vegetation? How do dense seeding and planting of native species affect buckthorn re‐establishment? Page 6 of 10 Agenda Item: 10 6

6/4/2018 Seeding experiment 200’ Herbicide No Herbicide No Seed No Seed 40’ or 80’ B C A D Herbicide No Herbicide Seed Seed Replicated 29 times across 7 sites Lesson for Minnesota Seeding didn’t increase shade in first year Perennial species already showing greater cover this year Re‐vegetation by seeding is a multi‐year process Early May seeded unseeded Page 7 of 10 Agenda Item: 10 7

6/4/2018 Planting experiment Replicated 18 times across 3 sites +2 partner sites Planting shrubs, trees, or sedges creates smaller buckthorn… … because they increase shade Page 8 of 10 Agenda Item: 10 8

6/4/2018 … because they increase shade fern shrub unplanted sedge tree Canopy Shade Understory Shade … because they increase shade Canopy Shade Understory Shade Lesson for Minnesota Re‐vegetating with native species can impede re‐establishment of buckthorn Page 9 of 10 Agenda Item: 10 9

6/4/2018 Shade reduces buckthorn seedling growth across all seeded and planted plots Lesson for Minnesota Deep shade smothers buckthorn This amount of shading can be created with re‐vegetation (not just with big trees) Goal is to reach this level of shading quickly after buckthorn removal Page 10 of 10 Agenda Item: 10 10